DOKK Library

Plug-in Development Guide Release 26.1

Authors Julien Signoles with Thibaud Antignac Loïc Correnson Matthieu Lemerre Virgile Prevosto

License CC-BY-SA-4.0

Developer Manual
         Plug-in Development Guide
                             Release 26.1 (Iron)

     Julien Signoles with Thibaud Antignac, Loïc Correnson, Matthieu Lemerre and
                                   Virgile Prevosto

This work is licensed under a Creative Commons “Attribution-
ShareAlike 4.0 International” license.

                          CEA-List, Université Paris-Saclay
                          Software Safety and Security Lab

©2009-2023 CEA LIST

Foreword                                                                                           9

1 Introduction                                                                                    11
  1.1   About this document . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       11
  1.2   Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     12

2 Tutorial                                                                                        13
  2.1   Development Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . .         13
  2.2   What Does a Plug-in Look Like? . . . . . . . . . . . . . . . . . . . . . . . . .          14
  2.3   The Hello plug-in . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     14
        2.3.1   Creating a new plug-in . . . . . . . . . . . . . . . . . . . . . . . . . . .      15
        2.3.2   A Very Simple Plug-in . . . . . . . . . . . . . . . . . . . . . . . . . . .       16
        2.3.3   Registering a Plug-in in Frama-C . . . . . . . . . . . . . . . . . . . . .        17
        2.3.4   Displaying Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . .       17
        2.3.5   Adding Command-Line Options           . . . . . . . . . . . . . . . . . . . . .   18
        2.3.6   About the plug-in build process . . . . . . . . . . . . . . . . . . . . . .       20
        2.3.7   Testing your Plug-in . . . . . . . . . . . . . . . . . . . . . . . . . . . .      22
        2.3.8   Documenting your Source Code . . . . . . . . . . . . . . . . . . . . . .          26
        2.3.9   Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      28
  2.4   The ViewCfg plug-in . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       28
        2.4.1   Visiting the AST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      28
        2.4.2   Plug-in registration and command-line options . . . . . . . . . . . . .           32
        2.4.3   Interfacing with other plug-ins . . . . . . . . . . . . . . . . . . . . . .       33
        2.4.4   Splitting files and providing a mini-GUI for testing . . . . . . . . . . .        34
        2.4.5   Saving/Loading Data, and Usability in a Multi-Project Setting . . . .             37

3 Software Architecture                                                                           41
  3.1   General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       41
  3.2   Plug-ins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    43
  3.3   Libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   43


  3.4   Kernel Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     43
  3.5   Kernel Internals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    44

4 Advanced Plug-in Development                                                                    45
  4.1   Plug-in dependencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      45
        4.1.1   Declaring dependencies . . . . . . . . . . . . . . . . . . . . . . . . . .        46
        4.1.2   Notifying users via frama-c-configure . . . . . . . . . . . . . . . . . . .       47
  4.2   Frama-C Makefiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       47
  4.3   Testing   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   48
        4.3.1   Using ptests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    49
        4.3.2   Test directory structure . . . . . . . . . . . . . . . . . . . . . . . . . .      49
        4.3.3   What happens when you run a test . . . . . . . . . . . . . . . . . . . .          51
        4.3.4   Detailed directives . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     53
        4.3.5   Pre-defined macros for tests commands . . . . . . . . . . . . . . . . .           57
  4.4   Plug-in Migration from Makefile to Dune . . . . . . . . . . . . . . . . . . . .           57
        4.4.1   Files organization changes . . . . . . . . . . . . . . . . . . . . . . . . .      57
        4.4.2   Template dune file . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      58
        4.4.3   autoconf and configure . . . . . . . . . . . . . . . . . . . . . . . . .          58
        4.4.4   GUI migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       59
        4.4.5   Build and . . . . . . . . . . . . . . . . . . . . . . . . . .         60
        4.4.6   Installing Additional Files . . . . . . . . . . . . . . . . . . . . . . . . .     60
        4.4.7   Migrating tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     60
  4.5   Plug-in General Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      60
  4.6   Logging Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      61
        4.6.1   From printf to Log . . . . . . . . . . . . . . . . . . . . . . . . . . . .        62
        4.6.2   Log Quick Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . .       62
        4.6.3   Logging Routine Options . . . . . . . . . . . . . . . . . . . . . . . . .         63
        4.6.4   Advanced Logging Services . . . . . . . . . . . . . . . . . . . . . . . .         65
  4.7   The Datatype library: Type Values and Datatypes . . . . . . . . . . . . . . .             67
        4.7.1   Type Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      67
        4.7.2   Datatype . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      68
  4.8   Plug-in Registration and Access . . . . . . . . . . . . . . . . . . . . . . . . . .       71
        4.8.1   Registration through a .mli File . . . . . . . . . . . . . . . . . . . . .        71
        4.8.2   Kernel-integrated Registration and Access . . . . . . . . . . . . . . . .         71
        4.8.3   Dynamic Registration and Access . . . . . . . . . . . . . . . . . . . . .         73
  4.9   Project Management System . . . . . . . . . . . . . . . . . . . . . . . . . . .           75
        4.9.1   Overview and Key Notions . . . . . . . . . . . . . . . . . . . . . . . .          76
        4.9.2   State: Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    76


        4.9.3   Registering a New State . . . . . . . . . . . . . . . . . . . . . . . . . .       78
        4.9.4   Direct Use of Low-level Functor State_builder.Register . . . . . .                80
        4.9.5   Using Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      82
        4.9.6   Selections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    83
   4.10 Command Line Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .          84
        4.10.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     84
        4.10.2 Tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     86
   4.11 Initialization Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    86
   4.12 Customizing the AST creation . . . . . . . . . . . . . . . . . . . . . . . . . .          89
   4.13 Customizing the machine model . . . . . . . . . . . . . . . . . . . . . . . . . .         90
   4.14 Machdep record fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       96
   4.15 Visitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    98
        4.15.1 Entry Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       98
        4.15.2 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      98
        4.15.3 Action Performed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       99
        4.15.4 Visitors and Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . .      99
        4.15.5 In-place and Copy Visitors . . . . . . . . . . . . . . . . . . . . . . . .         99
        4.15.6 Differences Between the Cil and Frama-C Visitors . . . . . . . . . . . . 101
        4.15.7 Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
   4.16 Logical Annotations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
   4.17 Extending ACSL annotations . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
   4.18 Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
        4.18.1 Representations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
        4.18.2 Map Indexed by Locations         . . . . . . . . . . . . . . . . . . . . . . . . 108
   4.19 GUI Extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
   4.20 Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

A Changes                                                                                        111

Bibliography                                                                                     119

List of Figures                                                                                  121

Index                                                                                            123


This is the documentation of the Frama-C implementation1 which aims at helping developers
integrate new plug-ins inside this platform. It started as a deliverable of the task 2.3 of the
ANR RNTL project CAT2 .
The content of this document corresponds to the version 26.1 (Iron), released on February 15,
2023, of Frama-C. However the development of Frama-C is still ongoing: features described
here may still evolve in the future.


We gratefully thank all the people who contributed to this document: Michele Alberti, Gergö
Barany, Patrick Baudin, Allan Blanchard, Richard Bonichon, David Bühler, Pascal Cuoq,
Zaynah Dargaye, Basile Desloges, Florent Garnier, Pierre-Loïc Garoche, Philippe Herrmann,
Boris Hollas, Nikolaï Kosmatov, Jean-Christophe Léchenet, Romain Maliach-Auguste, An-
dré Maroneze, Benjamin Monate, Yannick Moy, Anne Pacalet, Valentin Perrelle, Armand
Puccetti, Muriel Roger and Boris Yakobowski.
We also thank Johannes Kanig for his Mlpost support3 , the tool formerly used for making
figures of this document.


                                                                              Chapter 1


Frama-C (Framework for Modular Analyses of C) is a software platform which helps the devel-
opment of static and dynamic analysis tools for C programs thanks to a plug-in mechanism.
This guide aims at helping developers program within the Frama-C platform, in particular for
developing a new analysis or a new source-to-source transformation through a new plug-in.
For this purpose, it provides a step-by-step tutorial, a general presentation of the Frama-C
software architecture and an overview of the API of the Frama-C kernel. However it does
not provide a complete documentation of the Frama-C API and, in particular, it does not
describe the API of existing Frama-C plug-ins.
This guide introduces neither the use of Frama-C, which is the purpose of the user manual [3]
and of the reference articles [7, 12], nor the use of plug-ins which are documented in separated
and dedicated manuals [2, 4, 9, 11, 19]. We assume that the reader of this guide already read
the Frama-C user manual and knows the main Frama-C concepts.
The reader of this guide may be either a Frama-C beginner who just finished reading the user
manual and wishes to develop their own analysis with the help of Frama-C, an intermediate-
level plug-in developer who would like to have a better understanding of one particular aspect
of the framework, or a Frama-C expert who wants to remember details about one specific point
of the Frama-C development.
Frama-C is fully developed within the OCaml programming language [13]. Motivations for this
choice are given in a Frama-C experience report [8]. However this guide does not provide any
introduction to this programming language: the World Wide Web already contains plenty of
resources for OCaml developers (see for instance

1.1     About this document

To ease reading, section heads may state the category of readers they are intended for and a
set of prerequisites.
Appendix A references all the changes made to this document between successive Frama-C
In the index, page numbers written in bold italics (e.g. 1 ) reference the defining sections
for the corresponding entries while other numbers (e.g. 1) are less important references.
Furthermore, the name of each OCaml value in the index corresponds to an actual Frama-C

                                  CHAPTER 1. INTRODUCTION

 The most important paragraphs are displayed inside gray boxes like this one. A plug-in
 developer must follow them very carefully.

 There are numerous code snippets in this document. Beware that copy/pasting them
 from the PDF to your favorite text editor may prevent your code from compiling, because
 the PDF text can contain non-ASCII characters.

1.2    Outline

This guide is organised in three parts.

Chapter 2 is a step-by-step tutorial for developing a new plug-in within the Frama-C plat-
    form. At the end of this tutorial, a developer should be able to extend Frama-C with a
    simple analysis available as a Frama-C plug-in.

Chapter 3 presents the Frama-C software architecture.

Chapter 4 details how to use all the services provided by Frama-C in order to develop a
    fully integrated plug-in.

                                                                            Chapter 2


Target readers: beginners.

This chapter aims at helping a developer to write their first Frama-C plug-in. At the end of
the tutorial, any developer should be able to extend Frama-C with a simple analysis available
as a Frama-C plug-in. This chapter was written as a step-by-step explanation on how to
proceed towards this goal. It will get you started, but it does not tell the whole story. You
will get it with your own experiments, and by reading the other chapters of this guide as
Section 2.1 provides some tips for setting up a development environment for Frama-C. Sec-
tion 2.2 shows what a plug-in looks like. Then Section 2.3 explains the basis for writing a
standard Frama-C plug-in, while Section 2.4 details how to interact with Frama-C and other
plug-ins to implement analyzers of C programs.

2.1       Development Environment

It is easy to develop a plug-in for Frama-C with any IDE, as long as it supports the OCaml
language. This includes (but is not limited to) Emacs or Vim with the Merlin1 tool, or
VS Code with the OCaml platform extension. The last is probably the easiest to setup for a
beginner in OCaml.
Most modern IDEs support (directly or indirectly, via Merlin) OCaml-LSP2 , which is an
implementation of LSP (Language Server Protocol) for OCaml.
Concerning code formatting, the Frama-C team currently uses the ocp-indent opam package
for code indentation. Consider installing it if you want to ensure your code follows the same
Overall, it is strongly suggested to use an OCaml-aware IDE and take the time to set it up.
Plug-ins use several different parts of the Frama-C API, and a properly setup IDE greatly
improves productivity, offering features such as auto-completion, type checking, syntax high-
lighting, and code navigation.


                                     CHAPTER 2. TUTORIAL

2.2     What Does a Plug-in Look Like?
Figure 2.1 shows how a plug-in can integrate with the Frama-C platform. This tutorial focuses
on specific parts of this figure.

                                             Plug-in directory

                                 Plug-in                              dune
                             implementation                       dune-project
      Plugin                        Register

       Type                          Options
                                                                 Plug-in GUI

      Project                          ...                               ...

                                                               (GUI extension point)

                                                                         registration points

                          Figure 2.1: Plug-in Integration Overview.

The implementation of the plug-in is provided inside a specific directory. The plug-in registers
with the Frama-C platform through kernel-provided registration points. These registrations
are performed through hooks (by applying a function or a functor). For instance, the next
section shows how to:

  • extend the Frama-C entry point thanks to the function Db.Main.extend if you want to
    run plug-in specific code whenever Frama-C is executed;
  • use specific plug-in services provided by the module Plugin, such as adding a new
    Frama-C option.

2.3     The Hello plug-in
This simple plug-in illustrates how to create your own plug-in basically with several aspects
of the Frama-C framework: building the plugin and installing the plug-in, registration, getting

                                      2.3. THE HELLO PLUG-IN

command-line options, console output, testing and documentation. (In case of difficulty, it is
explained at the end of this section how to generate the whole plug-in.)

2.3.1      Creating a new plug-in

A plug-in is built using Dune3 . It is composed minimally of the following files:

  • a dune-project file that describes the project;

  • a dune file that describes the build of the project;

  • a <my_plugin>.ml file that defines the API of the plugin (which can be empty).

For example, for the Hello plugin:

 File ./dune-project

       (lang dune 3.2)
       (using dune_site 0.1)

       (name frama-c-hello)
       (package (name frama-c-hello))

The dune_site feature4 mentioned in this file allows us to rely on dune to install the plug-in
in a place where Frama-C will find it and load it at runtime.

 File ./dune

       ( library
        (name Hello)
        (public_name frama-c-hello.core)
        ( flags -open Frama_c_kernel :standard)
        ( libraries frama-c.kernel)

       ( plugin
        ( optional )
        (name hello)
        ( libraries frama-c-hello.core)
        ( site (frama-c plugins))) is just an empty file.
Then the plugin can be built using the following command:
dune build
If Dune is installed, this should compile the project successfully. Note that Dune emits
messages during compilation, but erases them afterwards. In case of success, there will be
no visible output at the end. Note that this behavior can be configured with Dune’s option

                                      CHAPTER 2. TUTORIAL

 Dune always looks for dune-project files in the parent directories, so make sure that
 your Hello directory is not inside another one containing a Dune project (e.g. if you are
 running this directly from the Frama-C source archive), otherwise dune build may fail.
 You can always add option “--root .”, or create an empty dune-workspace file in the
 current directory to force Dune to ignore parent directories.

Note a few details about the naming conventions:

  • in the dune-project file, the name of the plugin is frama-c-<my-plugin>

  • in the dune file, the name of:

        – the library is my_plugin;
        – the public name of the library is frama-c-<my-plugin>.core (dune project name
        – the name of the plugin is <my-plugin>;
        – the plugin must at least include the library frama-c-<my-plugin>.core.

Of course, for now, our plug-in does nothing, so let us change that.

2.3.2    A Very Simple Plug-in

Let us add a simple file to our plug-in:

 File ./

     let run () =
           let chan = open_out "hello.out" in
           Printf . fprintf chan "Hello, world!\n";
           flush chan;
          close_out chan
       with Sys_error _ as exc →
           let msg = Printexc.to_string exc in
           Printf . eprintf "There was an error: %s\n" msg

     let () = Db.Main.extend run

This file defines a simple function that writes a message to an output file, then registers the
function run as an entry point. Frama-C will call it among the other plug-in entry points if
the plug-in is loaded.
The plug-in is compiled the same way as previously explained in 2.3.1. Then, one can execute
the script using the command:
dune exec -- frama-c
Executing this command creates a hello.out file in the current directory.

 You can think of dune exec -- as a wrapper for frama-c which adds your plug-in to
 those already present in Frama-C. It operates on a local Dune sandbox, allowing you to
 test it without risking “polluting” your installed Frama-C.

                                          2.3. THE HELLO PLUG-IN

2.3.3     Registering a Plug-in in Frama-C

To make this script better integrated into Frama-C, its code must register itself as a plug-
in. Registration provides general services, such as outputting to the Frama-C console and
extending Frama-C with new command-line options.
Registering a plug-in is achieved through the use of the Plugin.Register functor:

 File ./

      let help_msg = "output a warm welcome message to the user"

      module Self = Plugin.Register
           let name = "hello world"
           let shortname = "hello"
           let help = help_msg

      let run () =
            let chan = open_out "hello.out" in
            Printf . fprintf chan "Hello, world!\n";
            flush chan;
           close_out chan
        with Sys_error _ as exc →
            let msg = Printexc.to_string exc in
            Printf . eprintf "There was an error: %s\n" msg

      let () = Db.Main.extend run

The argument to the Plugin.Register functor is a module with three values:

   • name is an arbitrary, non-empty string containing the full name of the module.
   • shortname is a small string containing the short name of the module, to be used as a
     prefix for all plug-in options5 . It cannot contain spaces.
   • help is a string containing free-form text, with a description of the module.

Visible results of the registration include:

   • “hello world” appears in the list of available plug-ins; you can check it by running
     dune exec -- frama-c -plugins;
   • default options for the plug-in work, including the inline help (available with
     dune exec -- frama-c -hello-help).

2.3.4     Displaying Messages

The signature of the module Self obtained by applying Plugin.Register is
General_services. One of these general services is logging, i.e. message display. In Frama-
C, one should never attempt to write messages directly to stderr or stdout: use the general
services instead6 .
     Frama-C does not enforce that all plug-in options are prefixed with its shortname, but it is customary to
do so.
     However, writing to a new file using standard OCaml primitives is OK.

                                          CHAPTER 2. TUTORIAL

 File ./

       let help_msg = "output a warm welcome message to the user"

       module Self = Plugin.Register
            let name = "hello world"
            let shortname = "hello"
            let help = help_msg

       let run () =
          Self . result "Hello, world!";
          let product =
             Self .feedback ∼ level:2 "Computing the product of 11 and 5...";
            11 * 5
          Self . result "11 * 5 = %d" product

       let () = Db.Main.extend run

Running this script yields the following output:
       $ dune exec -- frama-c
       [hello] Hello, world!
       [hello] 11 * 5 = 55

The result routine is the function to use to output results of your plug-in. The Frama-C
output routines take the same arguments as the OCaml function Format.printf7 .
Function feedback outputs messages that show progress to the user. In this example, we
decided to emit a feedback message with a log level of 2, because we estimated that in most
cases the user is not interested in seeing the progress of a fast operation (simple multiplica-
tion). The default log level is 1, so by default this message is not displayed. To see it, the
verbosity of the hello plug-in must be increased:
       $ dune exec -- frama-c -hello-verbose 2
       [hello] Hello, world!
       [hello] Computing the product of 11 and 5...
       [hello] 11 * 5 = 55

For a comprehensive list of logging routines and options, see Section 4.6.

2.3.5     Adding Command-Line Options

We now extend the hello world plug-in with new options.
If the plug-in is installed (globally, with dune install, or locally, with dune exec), it will be
loaded and executed on every invocation of frama-c, which is not how most plug-ins work.
To change this behavior, we add a boolean option, set by default to false, that conditionally
enables the execution of the main function of the plug-in. The usual convention for the name
of this option is the short name of the module, without suffix, i.e. -hello in our case.
     The Format module is part of the OCaml standard library and provides advanced pretty-printing features.
If you are not familiar with it, consider grepping some Frama-C messages to get a feel for how to use it.

                                    2.3. THE HELLO PLUG-IN

We also add another option, -hello-output, that takes a string argument. When set, the
hello message is displayed in the file given as argument.

 File ./

     let help_msg = "output a warm welcome message to the user"

     module Self = Plugin.Register
          let name = "hello world"
          let shortname = "hello"
          let help = help_msg

     module Enabled = Self.False
          let option_name = "-hello"
          let help = "when on (off by default), " ^ help_msg

     module Output_file = Self.String
          let option_name = "-hello-output"
          let default = "-"
          let arg_name = "output-file"
          let help =
            "file where the message is output (default: output to the console)"

     let run () =
           if Enabled.get() then
              let filename = Output_file.get () in
              let output msg =
                 if Output_file.is_default() then
                    Self . result "%s" msg
                    let chan = open_out filename in
                    Printf . fprintf chan "%s\n" msg;
                    flush chan;
                   close_out chan;
             output "Hello, world!"
       with Sys_error _ as exc →
           let msg = Printexc.to_string exc in
           Printf . eprintf "There was an error: %s\n" msg

     let () = Db.Main.extend run

Registering these new options is done by calling the Self.False and Self.String functors,
which respectively create a new boolean option whose default value is false and a new string
option with a user-defined default value (here, "-"). The values of these options are obtained
via Enabled.get () and Output_file.get ().
With this change, the hello message is displayed only if Frama-C is executed with the -hello

                                    CHAPTER 2. TUTORIAL

     $ dune exec -- frama-c
     $ dune exec -- frama-c -hello
     [hello] Hello, world!
     $ dune exec -- frama-c -hello -hello-output hello.out
     $ ls hello.out

These new options also appear in the inline help for the hello plug-in:
     $ dune exec -- frama-c -hello-help

     -hello            when on (off by default), output a warm welcome message
                       to the user (opposite option is -no-hello)
     -hello-output <output-file> file where the message is output (default:
                       output to the console)

2.3.6    About the plug-in build process

As mentioned before, each plug-in needs a module declaring its public API. In our examples,
this was file, which was left empty. To make it more explicit to future users of our
plug-in, it is customary to add a comment such as the following:

 File ./

     (∗∗ Hello World plug−in.

          No function is exported. ∗)

Note that, to avoid issues, the name of each compilation unit (here hello_world) must be
different from the plug-in name set in the dune file (here hello), from any other plug-in
names (e.g. eva, wp, etc.) and from any other Frama-C kernel OCaml files (e.g. plugin).
The module name chosen by a plug-in (here hello) is used by Dune to pack that plug-in; any
functions declared in it become part of the plug-in’s public API. They become accessible to
other plug-ins and need to be maintained by the plug-in developer. Leaving it empty avoids
exposing unnecessary implementation details.
Inside the plug-in’s directory, dune build compiles it and creates the packed module. It can
be installed along with the other Frama-C plug-ins using dune install.
You can then just launch frama-c (without any options), and the hello plug-in will be
automatically loaded. Check it with the command frama-c -hello-help.
You can uninstall it by running dune uninstall.

Splitting your source files
Here is a slightly more complex example where the plug-in has been split into several files.
Usually, plug-in registration through Plugin.Register should be done at the bottom of the
module hierarchy, while registration of the run function through Db.Main.extend should
be at the top. The three following files completely replace the ./ from the
previous section. Modules are directly called by their name in the classical OCaml way.

                                     2.3. THE HELLO PLUG-IN

 File ./

      let help_msg = "output a warm welcome message to the user"

     module Self = Plugin.Register
          let name = "hello world"
          let shortname = "hello"
          let help = help_msg

     module Enabled = Self.False
          let option_name = "-hello"
          let help = "when on (off by default), " ^ help_msg

     module Output_file = Self.String
          let option_name = "-hello-output"
          let default = "-"
          let arg_name = "output-file"
          let help =
            "file where the message is output (default: output to the console)"

 File ./

      let output msg =
            let filename = Hello_options.Output_file.get () in
            if Hello_options.Output_file.is_default () then
              Hello_options. Self . result "%s" msg
               let chan = open_out filename in
               Printf . fprintf chan "%s\n" msg;
               flush chan;
              close_out chan
        with Sys_error _ as exc →
            let msg = Printexc.to_string exc in
            Printf . eprintf "There was an error: %s\n" msg

 File ./

      let run () =
         if Hello_options.Enabled.get() then
           Hello_print.output "Hello, world!"

      let () = Db.Main.extend run

The plug-in can be tested again by running:
     $ dune build
     $ dune install
     $ frama-c -hello -hello-output hello.out

                                     CHAPTER 2. TUTORIAL

     $ more hello.out
     Hello, world!

However, this does not consist in a proper test per se. The next section presents how to
properly test plug-ins.

2.3.7    Testing your Plug-in

Frama-C supports non-regression testing of plug-ins. This is useful to check that further
plug-in modifications do not introduce new bugs. The tool allowing to perform the tests is
called ptests .

 Historically, ptests was developed before Frama-C used Dune. It was adapted to Dune to
 maintain backwards compatibility, but new plug-ins may prefer using Dune’s test sytem

This is the general layout of the tests directory in a Frama-C plug-in; each file will be
explained later.
     <plug-in directory>
     +- tests
        +- ptests_config
        +- test_config
        +- suite1
           +- test1.c
           +- ...
           +- oracle
              +- ...
           +- result
              +- test1.0.exec.wtests
              +- ...
       +- ...

Inside the tests directory, ptests_config lists the test suites, i.e. directories containing
 File ./tests/ptests_config

     DEFAULT_SUITES= hello

Small plug-ins typically have a single test directory with the plug-in name.
Then, a default configuration must be provided for the tests. This is done by adding a
test_config file to the tests directory.

 File ./tests/test_config

     PLUGIN: hello

This configuration must include the plug-ins required by the test; usually, the plug-in itself,
but also other plug-ins on which it depends. The plug-in name is the one provided in the
plugin section of the dune file.

                                     2.3. THE HELLO PLUG-IN

For non-regression testing, the current behavior of a program is taken as the oracle against
which future versions will be tested. In this tutorial, the test will be about the correct Hello,
world! output made by the option -hello of the plug-in.
Each test file should contain a run.config comment with test directives and the C source
code used for the test (note: there are other ways to declare and control tests, as detailed in
Section 4.3.2).
For this tutorial, no actual C code is needed, so ./tests/hello/hello_test.c will only
contain the run.config header:

 File ./tests/hello/hello_test.c

     /* run.config
        OPT: -hello

In this file, there is only one directive, OPT: -hello, which specifies that Frama-C will set
option -hello when running the test. A look at Section 4.3.4 gives you an idea of the kinds
of directives which can be used to test plug-ins.
Once run.config has been configured, it becomes possible to generate Dune test files via
the ptests tool:
     $ frama-c-ptests
     Test directory: tests
     Total number of generated dune files: 2

This must be done each time a test configuration is modified or a test file or directory is
Then, one can execute the tests and get the output generated by the plug-in, by run-
ning dune build @ptests. Note that if you forget the intermediate step of running
frama-c-ptests, you may end up with the following error:
     Error: Alias "ptests" specified on the command line is empty.
     It is not defined in tests or any of its descendants.

But with the dune files generated by frama-c-ptests, you can run the tests:
     $ dune build @ptests
     Files ../oracle/ and hello_test.res.log differ
     % dune build @"tests/hello/result/hello_test.0.exec.wtests": diff failure on
     (cd _build/default/tests/hello/result && diff --new-file "hello_test.res.log"
     File "tests/hello/oracle/", line 1, characters 0-0:
     diff --git a/_build/default/tests/hello/oracle/
     index e69de29..5f6ab23 100644
     --- a/_build/default/tests/hello/oracle/
     +++ b/_build/default/tests/hello/result/hello_test.res.log
     @@ -0,0 +1,2 @@
     +[kernel] Parsing hello_test.c (with preprocessing)
     +[hello] Hello, world!

There is a lot of information in the output. The relevant parts can be summarized as:

                                      CHAPTER 2. TUTORIAL

  • Dune runs its tests inside a sandboxed environment, in directory _build/default, which
    is (approximately) a copy of the plug-in file tree;

  • Dune compared two files, none of which existed before running the test:
    result/hello_test.res.log and oracle/;

  • The last lines (which should be colored, if your terminal supports colors) show the
    textual difference between the expected and actual outputs.

The first file, result/hello_test.res.log, is the actual output of the execution of the test
command. The second file, oracle/, is the expected output of the
The result file is re-generated each time the test is run. The oracle file, however, is supposed
to exist beforehand (unless the test produces no output).
In reality, there are 2 pairs of files for each test: a pair .res.{log,oracle} and another
.err.{log,oracle}. The first one contains results sent to the standard output (stdout),
while the second one contains messages sent to the standard error (stderr). In our example,
the error output is empty, so it generates no differences. Note that Dune only outputs
messages in case of errors, i.e. tests producing the expected result are silent.
Finally, concerning the actual diff in the test (last two lines), the first line (starting with
[kernel]) is emitted by the Frama-C kernel, and the second one is our plug-in’s result, as
Once you have verified the actual output is the one you expected, you can promote it to the
status of “official oracle” for future non-regression tests, by running:
     $ dune promote

Note, however, that if the oracles do not exist, they must be created:
     $ frama-c-ptests -create-missing-oracles tests
     $ dune promote

The option -create-missing-oracles always creates both result and error oracles. Most
of the time, however, only the former is useful. After promoting tests, it is useful to remove
empty oracles:
     $ frama-c-ptests -remove-empty-oracles tests

The new oracle should be committed to source control, for future testing.

 Once your plug-in has test files, the dune build command presented earlier will not only
 compile your plug-in, but also run its tests. Therefore, if you want to simply compile it,
 you will have to run dune build @install instead. Despite the name, the command will
 not install your plug-in, it will only build and collect all files necessary for its installation.

Now, let’s introduce an error. Assume the plug-in has been modified as follows:

 File ./

      let run () =
         if Hello_options.Enabled.get() then
           Hello_print.output "Hello world!" (∗ removed comma ∗)

      let () = Db.Main.extend run

                                         2.3. THE HELLO PLUG-IN

We assume that “Hello, world!” has been unintentionally changed to “Hello world!”.
Running these commands:
       $ dune build @install
       $ dune build @ptests
       Files ../oracle/ and hello_test.res.log are different
       % dune build @"tests/hello/result/hello_test.0.exec.wtests": diff failure on
        (cd _build/default/tests/hello/result && diff --new-file "hello_test.res.log
            " "../oracle/")
       File "tests/hello/oracle/", line 1, characters 0-0:
       diff --git a/_build/default/tests/hello/oracle/ b/_build
       index 5f6ab2389a..cf2e5c010c 100644
       --- a/_build/default/tests/hello/oracle/
       +++ b/_build/default/tests/hello/result/hello_test.res.log
       @@ -1,2 +1,2 @@
        [kernel] Parsing hello_test.c (with preprocessing)
       -[hello] Hello, world!
       +[hello] Hello world!

displays the differences (à la diff) between the current execution and the saved oracles.
Here, the diff clearly shows that the only difference is the missing comma in the generated
message due to our (erroneous) modification. After fixing the OCaml code, running again the
previous commands shows that all test cases are successful.
You may check other Frama-C plug-ins as examples of how to integrate a plug-in with
ptests. Small plug-ins such as Report and Variadic are good examples (see directories
src/plugins/report/tests and src/plugins/variadic/tests). Please note Frama-C of-
fers no particular support for other kinds of testing purposes, such as test-driven development
(TDD)8 . Additional information about plug-in testing is available in Sections 4.3.

Summary of Testing Operations
Here’s a summarized list of operations in order to add a new test:

   1. Create a test case (.c or .i file in tests/<suite>).

   2. Add a run.config header to the test.

   3. frama-c-ptests -create-missing-oracles

   4. dune build @ptests

   5. Manually inspect oracle diffs to check that they are ok.

   6. dune promote

   7. frama-c-ptests -remove-empty-oracles

Operations to perform when modifying the plug-in code:
    For instance, one required feature for TDD that ptests does not support, is to force the user to manually
create ./tests/*/oracle/*.oracle files before running a new test.

                                   CHAPTER 2. TUTORIAL

  1. dune build @install

  2. dune build @ptests

  3. If there are expected diffs, run dune promote; otherwise, fix code and re-run the first

2.3.8    Documenting your Source Code

One can generate the documentation of a plugin using the command:
dune build @doc
This relies on odoc and requires the plug-in to be documented following the odoc guidelines
(check for details).
We show here how the Hello plug-in could be slightly documented and use odoc features
such as @-tags and cross references. First, we modify the file to export all inner
modules, otherwise odoc will not generate documentation for them:

 File ./

     (∗∗ Hello World plug−in.
         All modules are exported to illustrate documentation generation by odoc. ∗)

     module Hello_run = Hello_run
     module Hello_options = Hello_options
     module Hello_print = Hello_print

Then, we add some documentation tags to our modules:

 File ./

     (∗∗ This module contains the possible command line options
         for the Hello plug−in.
         @author Anne Onymous
         @see < http://frama−−c−plugin−development−guide.pdf>
             Frama−C Developer Manual, Tutorial

     (∗∗ Content of the welcome message. ∗)
     let help_msg = "output a warm welcome message to the user"

     (∗∗ Registration of the plug−in to Frama−C. ∗)
     module Self = Plugin.Register
           let name = "hello world"
           let shortname = "hello"
           let help = help_msg

     (∗∗ Enabling of the plug−in. ∗)
     module Enabled = Self.False
           let option_name = "-hello"
           let help = "when on (off by default), " ^ help_msg

                                   2.3. THE HELLO PLUG-IN

    (∗∗ Output of the plug−in. ∗)
    module Output_file = Self.String
          let option_name = "-hello-output"
          let default = "-"
          let arg_name = "output-file"
          let help =
            "file where the message is output (default: output to the console)"

File ./

    (∗∗ This module contains the printing method of the Hello plug−in.
        @author Anne Onymous
        @see < http://frama−−c−plugin−development−guide.pdf>
           Frama−C Developer Manual, Tutorial

    (∗∗ Outputs a message to the output selected in
         @param msg Message to output.
         @raise Sys_error if filesystem error.
    let output msg =
          let filename = Hello_options.Output_file.get () in
          if Hello_options.Output_file.is_default () then
            Hello_options. Self . result "%s" msg
             let chan = open_out filename in
             Printf . fprintf chan "%s\n" msg;
             flush chan;
            close_out chan
      with Sys_error _ as exc →
          let msg = Printexc.to_string exc in
          Printf . eprintf "There was an error: %s\n" msg

File ./

    (∗∗ This module contains the main control logic of the Hello plug−in.
        @author Anne Onymous
        @see < http://frama−−c−plugin−development−guide.pdf>
           Frama−C Developer Manual, Tutorial

    (∗∗ Controls the output of a given message by
             {!val:Hello_print.output} depending on the state of
    let run () =
       if Hello_options.Enabled.get() then
         Hello_print.output "Hello, world!"

    (∗∗ Definition of the entry point of the hello plug−in. ∗)
    let () = Db.Main.extend run

                                         CHAPTER 2. TUTORIAL

Running      dune build @doc       will   generate      documentation       files    in
./_build/default/_doc/_html. Open index.html in your browser and navigate to
see them. Note that odoc may report some warnings due to absence of annotation data for
Frama-C’s modules:
        Warning: Couldn't find the following modules:
          Frama_c_kernel Frama_c_kernel__Plugin

This should not prevent the generation of documentation for the library itself; but links to
modules such as Enabled and Output_file will not work.

2.3.9      Conclusion

This simple tutorial now comes to its end. It focused on the standard features of architectures
and interfaces of Frama-C plug-ins. A companion archive hello.tar.gz is available in the
download section of the Frama-C website9 . The next tutorial will make you dive in C analysis.

2.4       The ViewCfg plug-in
In this section, we create a new ViewCfg plug-in that computes the control flow graph of a
function and outputs it in the DOT format. Through its implementation, we explain some
of Frama-C APIs such as how to visit an AST10 , how to hook a plug-in, how to interface
a plug-in with other plug-ins, and how to make a plug-in usable in a multi-project setting
(which also allows it to save/load data).
This section assumes the reader is already familiar with the basics of plug-ins for Frama-C as
covered by the Hello plug-in in the previous section.

2.4.1      Visiting the AST

Writing an analysis for C programs is the primary purpose of a Frama-C plug-in. That
usually requires visiting the AST to compute information for some C constructs. There are
two different ways of doing that in Frama-C:

  • through a direct recursive descent; or
  • by using the Frama-C visitor.

The first case is usually better if you have to compute information for most C constructs,
while the latter is better if only few C constructs are interesting or if you have to write a
program transformation. Of course, it is also possible to combine both ways to tune it to
specific needs.

Pretty-printing with direct recursive descent
Frama-C already has a function to pretty-print statements (namely Printer.pp_stmt), but
it is not suitable for us, as it will recursively print substatements of compound statements
(blocks, if, while, ...), while we only want to pretty-print the node representing the current
statement: substatements will be represented by other nodes. Thus we will use the following
small function:
      The direct link is:
      Abstract Syntax Tree

                                    2.4. THE VIEWCFG PLUG-IN

      open Cil_types

      let   print_stmt out = function
        |   Instr i → Printer.pp_instr out i
        |   Return _ → Format.pp_print_string out "< return> "
        |   Goto _ → Format.pp_print_string out "< goto> "
        |   Break _ → Format.pp_print_string out "< break> "
        |   Continue _ → Format.pp_print_string out "< continue> "
        |   If (e,_,_,_) → Format.fprintf out "if %a" Printer.pp_exp e
        |   Switch(e,_,_,_) → Format.fprintf out "switch %a" Printer.pp_exp e
        |   Loop _ → Format.fprintf out "< loop> "
        |   Block _ → Format.fprintf out "< block> "
        |   UnspecifiedSequence _ → Format.fprintf out "< unspecified sequence> "
        |   TryFinally _ | TryExcept _ | TryCatch _ → Format.fprintf out "< try> "
        |   Throw _ → Format.fprintf out "< throw> "

The Cil_types module contains the definition of the AST of a C program, like constructors
Cil_types.Instr, Cil_types.Return, and so on which are of type Cil_types.stmtkind.
The Printer module contains functions that print the different Cil types. The documentation
of these module is available on the Frama-C website11 , or by typing make doc in the Frama-C
source distribution.

Creating the graphs with a visitor
In order to create our output, we must make a pass through the whole AST. An easy way
to do that is to use the Frama-C visitor mechanism. A visitor is a class with one method per
type of the AST, whose default behavior is to just call the method corresponding to each
of its children. By inheriting from the visitor, and redefining some of the methods, one can
perform actions on selected parts of the AST, without the need to traverse the AST explicitly.
      class print_cfg out = object
         inherit Visitor .frama_c_inplace

Here we used the so-called “in place” visitor, which should be used for read-only access to the
AST. When performing code transformations, a “copy” visitor should be used, that creates
a new project (see section 4.15.4).
There are three kinds of nodes where we have something to do. First, at the file level, we
create the whole graph structure.
       method! vfile _ =
        Format.fprintf out "digraph cfg {\n";
        Cil.DoChildrenPost (fun f → Format.fprintf out "}\n%!"; f)

Cil.DoChildrenPost is one of the possible visitAction s, that tells the visitor what to do
after the function is executed. With DoChildrenPost func, the func argument is called
once, after all children have been executed. Therefore, we use it to close the curly braces
after all functions have been printed in the file.
Then, for each function, we encapsulate the CFG in a subgraph, and do nothing for the other
       method! vglob_aux g =
        match g with
    From; look for API Documentation inside the
page corresponding to your Frama-C version.

                                           CHAPTER 2. TUTORIAL

              | GFun(f,_) →
                Format.fprintf out " subgraph cluster_%a {\n" Printer.pp_varinfo f.svar;
                Format.fprintf out "   graph [label=\"%a\"];\n" Printer.pp_varinfo f.svar;
                Cil.DoChildrenPost (fun g → Format.fprintf out " }\n"; g)
              | _ → Cil.SkipChildren

Cil.SkipChildren tells the visitor not to visit the children nodes, which makes it more
efficient12 .
Last, for each statement, we create a node in the graph, and create the edges toward its
          method! vstmt_aux s =
           Format.fprintf out "      s%d [label=%S];\n"
              s.sid (Pretty_utils.to_string print_stmt s.skind);
            List . iter (fun succ → Format.fprintf out " s%d → s%d;\n" s.sid succ.sid)

This code could be optimized, for instance by replacing the final DoChildren by
SkipChildren for statements that cannot contain other statements, like Instr, and avoid
visiting the expressions.
Finally, we close the object definition:

Hooking into Frama-C
Now we need to ensure the code is called at the appropriate time when Frama-C is run. Note
that if we simply add a function at the toplevel (i.e. let () = run ()), it will not work,
because Frama-C will not have had the time to parse the sources and produce its AST (used
by Ast.get ()). For more details about initialization issues, see Section 4.11.
        let run () =
           let chan = open_out "" in
           let fmt = Format.formatter_of_out_channel chan in
           Visitor .visitFramacFileSameGlobals (new print_cfg fmt) (Ast.get ());
          close_out chan

        let () = Db.Main.extend run

Now, since Frama-C uses Dune, this code needs to be integrated as a Dune project, as has
been done in the Hello tutorial. We need to create a new directory. In it, we will put all of the
code seen so far, in an .ml file. We will then add the corresponding dune and dune-project
 File dune

        ( library
         (name ViewCfg)
         (public_name frama-c-view-cfg.core)
         ( flags -open Frama_c_kernel :standard)
         ( libraries frama-c.kernel))

        ( plugin
      In a copying visitor, Cil.JustCopy should have been used instead.

                                      2.4. THE VIEWCFG PLUG-IN

      (name view-cfg)
      ( libraries frama-c-view-cfg.core)
      ( site (frama-c plugins)))

 File dune-project

     (lang dune 3.2)
     (using dune_site 0.1)

     (name frama-c-view-cfg)
     (package (name frama-c-view-cfg))

Finally, we need an (empty) interface file, called, in the same directory.
With all of this, we can compile the project with:
       dune build

And run it as a Frama-C plugin:
       dune exec -- frama-c [options] file.c [file2.c]

And the graph can be visualized with an external tool, such as dotty or xdot.

This produces a graph like in Figure 2.2

         File test.c                                             f                  main

             void f( int g)                                  g ++;                      i = 3;

                                                              g --;                 if i > 0
                                                            <return>         <loop>
             int main(int argc, char **argv)
                int i = 3;                                               i --;                   f(3);

                 if ( i > 0)                                                     if i
                      while (--i);
                    }                                                     <break>
                                                                             __retres = 0;
                 return 0;                                                       <return>

                           Figure 2.2: Control flow graph for file test.c.

                                    CHAPTER 2. TUTORIAL

Further improvements
There are many possible enhancements to this code:

  • There is a bug when trying to print statements that contain strings (such as
    printf("Hello\n"), due to double quotes. Such statements must be protected us-
    ing the "%S" Format directive;

  • The plug-in could be properly registered as such, allowing it to accept command-line
    options, for instance to compute the control flow graph of a single function given as

  • The graphs could be fancier, in particular by distinguishing between branching nodes
    and plain ones, or showing block entries and exits; or linking call sites to the called

We will concentrate on another extension, which is to reuse the analysis of the Eva plug-in
to color unreachable nodes. To do so, because we will combine different plug-ins, we need to
ensure their correct ordering. This requires the definition of some command-line options for
our plug-in.

2.4.2   Plug-in registration and command-line options

We have already seen how to register options in the previous “Hello” tutorial. We now apply
these principles to the ViewCfg plug-in.
     module   Self = Plugin.Register(struct
        let   name = "control flow graph"
        let   shortname = "viewcfg"
        let   help = "control flow graph computation and display"

     module Enabled = Self.False(struct
        let option_name = "-cfg"
        let help =
          "when on (off by default), computes the CFG of all functions."

     module   OutputFile = Self.String(struct
        let   option_name = "-cfg-output"
        let   default = ""
        let   arg_name = "output-file"
        let   help = "file where the graph is output, in dot format."

     let run () =
        if Enabled.get() then
           let filename = OutputFile.get () in
           let chan = open_out filename in
           let fmt = Format.formatter_of_out_channel chan in
           Visitor .visitFramacFileSameGlobals (new print_cfg fmt) (Ast.get ());
          close_out chan

     let () = Db.Main.extend run

                                          2.4. THE VIEWCFG PLUG-IN

We added two options, -cfg to compute the CFG conditionally (important for ordering
plug-in executions), and -cfg-output to choose the output file.
An interesting addition would be a -cfg-target option, which would take a set of files or
functions whose CFG would be computed, using the Self.Kernel_function_set functor.
Depending on the targets, visiting the AST would have different starting points. This is left
as an exercise for the reader.
Another interesting exercise is to solve the following problem. Currently, the complete CFG
for the whole application is computed in each Frama-C step, i.e. executing frama-c test.c
-cfg -then -report would compute the CFG twice. Indeed, the -cfg option sets Enabled
to true, and the run function is executed once per task. To solve this problem, one has
to create a boolean state to remember that the plug-in has already been executed. The
apply_once function in the State_builder module helps dealing with this issue (reading
the section 2.4.5 of this tutorial and section 4.9 of this manual should help you understand
the underlying notion of states).
With these command-line options, we can properly interface our ViewCfg plug-in with the
eva plug-in.

2.4.3       Interfacing with other plug-ins

Plug-ins can use functions specified in the public interfaces of other plug-ins, as long as they
are declared as dependencies. To do so, you only need to add them to the libraries stanza13
in the dune file. We will use a function from the Eva plug-in in our example, so we will add
frama-c-eva.core to the dune file:
         ( libraries   frama-c.kernel frama-c-eva.core))

Now our plug-in can call all functions and access all types declared in Eva’s public interface.
For historical reasons, several kernel-integrated plug-ins, such as From, InOut and Slicing, had
their API exposed via the Db module of the Frama-C kernel. This has been deprecated for
Eva, and newer plug-ins expose their public interface directly.
In our example, we will use Eva’s new API to obtain reachability information computed by
the value analysis. The code modification we propose is to color in pink the nodes guaranteed
to be unreachable by the value analysis. For this purpose, we change the vstmt_aux method
in the visitor:
          method! vstmt_aux s =
            let color =
               if Eva.Analysis.is_computed () then
                  if Eva.Results.is_reachable s
                 then "fillcolor=\"#ccffcc\" style=filled"
                  else "fillcolor=pink style=filled"
               else ""
           Format.fprintf out "       s%d [label=%S %s]\n"
               s.sid (Pretty_utils.to_string print_stmt s.skind) color;
            List . iter
               (fun succ → Format.fprintf out " s%d → s%d;\n" s.sid succ.sid)
      A stanza is, roughly speaking, a “term” in dune parlance: a parenthesized expression.

                                      CHAPTER 2. TUTORIAL

This code fills the nodes with green if the node may be reachable, and in pink if the node is
guaranteed not to be reachable; but only if the value analysis was previously computed.
To test this code, we recompile the plug-in with the modified dune file to take into account
the dependency on Eva, as well as the modified vstmt_aux. We run dune build @install
and then we run Eva, and then our plug-in:
        dune exec -- frama-c test.c -eva -then -cfg && dotty

The relative order of most options and file names is not important between occurrences of
-then, but it is important whether they are before or after -then-related options (-then,
-then-on, -then-last); see Section 4.11 for details. Here, we want to ensure that Eva is
run before our plug-in, so we order it as -eva -then -cfg. Without -then, even if -eva is
before -cfg in the command line, it is not guaranteed that it will run before; options in the
same “block” can be thought of as concurrent: there is no specified order between them.
The resulting graph is shown in Figure 2.3.

         File test.c                                          f                  main

             void f( int g)                                 g ++;                    i = 3;

                                                            g --;                if i > 0
                                                         <return>        <loop>
             int main(int argc, char **argv)
                int i = 3;                                            i --;                   f(3);

                 if ( i > 0)                                                  if i
                      while (--i);
                    }                                                  <break>
                                                                         __retres = 0;
                 return 0;                                                    <return>

            Figure 2.3: Control flow graph colored with reachability information.

2.4.4    Splitting files and providing a mini-GUI for testing

Our plug-in is starting to amass enough code that we should envisage to split it into several
modules, for better organizing it. Dune automatically compiles all source files it finds, unless
specified otherwise, and it handles dependencies between them, so it is essentially free to do
so. As we did in the Hello tutorial, we will split our file into smaller modules.
We will create the following files: : will contain the module registration (Self) and command-line options
     (Enabled and OutputFile);

                                         2.4. THE VIEWCFG PLUG-IN : will contain the print_stmt function and the visitor; : will contain the definition of function run and the call to Db.Main.extend.

Note that a few changes are needed to the code: functions from other files need to include
that file name as module, e.g. Enabled.get becomes Options.Enabled.get.
For simplicity’s sake, we will remove options -cfg and -cfg-output and replace them with a
single boolean option, -cfg-gui, to launch the GUI (this prevents unsuitable combinations
of -cfg and -cfg-gui). The new option is defined as below:
        module Gui = Self.False(struct
           let option_name = "-cfg-gui"
           let help =
             "when on (off by default), displays a mini-GUI for showing graphs."

And the run function in becomes simply:
        let run () =
           if Options.Gui.get() then

We can now erase and re-run dune build @install to compile the plug-in.

Mini-GUI for testing
Extending Frama-C’s Ivette graphical user interface is a task too large for this tutorial; Ivette
being a desktop Electron application, written in TypeScript and using React, there is a
substantial amount of explaining to do before one can show how to integrate a Frama-C
plug-in in it.
Instead, for this tutorial, we will use a lightweight OCaml GUI library, BOGUE14 . You can
install it through opam:
        $ opam install bogue

It is based on SDL2, which means you may need to install non-OCaml dependencies15 .
Since we will be using BOGUE in our plug-in, we need to declare it in the dune file:
         ( libraries   frama-c.kernel frama-c-eva.core bogue))

We also need a way to print an individual function as a standalone graph, without having to
call the file visitor (Visit.vfile). We will call it dump_function and put it in a separate

 File ./

        open Cil_types

        let dump_function fundec fmt =
 "Computing CFG for function %s"
          Format.fprintf fmt "digraph %s {\n" fundec.svar.vorig_name;
            ( Visitor .visitFramacFunction (new Visit.print_cfg fmt) fundec);
          Format.fprintf fmt "\n}\n"
      With opam < 2.1, you may need to install and run depext. With opam ≥ 2.1, depext is already included.

                                     CHAPTER 2. TUTORIAL

The code prints a feedback message, then the header, calls the visitor, and prints the footer.
This function will be called by our “mini-GUI”, and the output will be sent to dotty, which
will open a window with our graph.
The actual GUI code is put inside a file appropriately named

 File ./

     open Bogue
     module W = Widget
     module L = Layout

      let show () =
        (∗ Create a few widgets for our GUI: a label, a text input with the function
             to be displayed, and a button to show it. ∗)
         let l = W.label "Show graph for function:" in
         let t = W.text_input ∼text:"main" () in
         let b = W.button "Show CFG" in
         let status = W.label (String.make 50 '-') in (∗ used for error messages ∗)
         let layout = L.tower_of_w [l;t;b;status] in
         let show_graph _button =
            let name = W.get_text t in
              (∗ Check the function name exists and is defined (not just declared). ∗)
               let kf = Globals.Functions.find_by_name name in
               let fd = Kernel_function.get_definition kf in
              W.set_text status "";

            (∗ Create a temporary file with the graph and pass it to 'dotty'. ∗)
            let (tmpname, oc) = Filename.open_temp_file "cfg_view" ".dot" in
            Dump.dump_function fd (Format.formatter_of_out_channel oc);
            close_out oc;
            let cmd = Format.asprintf "dotty %S" tmpname in
            ignore (Sys.command cmd);
            W.set_text status (String.make 50 '-');
            Unix.unlink tmpname
          | Not_found →
            W.set_text status ("Error: function " ^ name ^ " not found.")
          | Kernel_function.No_Definition →
            W.set_text status ("Error: function " ^ name ^ " is not defined.")
        W.on_release ∼release:show_graph b;
        let board = Bogue.make [] [layout] in board

Most of the code is boilerplate for Bogue. The only Frama-C-related part is the checking
of the function name: Globals.Functions.find_by_name raises exception Not_found if the
name input by the user does not exist. But even if it does, since we need a function definition,
we must check that it is not simply declared. Besides that, we simply call dump_function.
Figure 2.4 shows what this mini-GUI looks like.
Whenever we click the “Show CFG” button, a new dotty window is opened. After we close
it, we can repeat the operation as we like.
Note that the feedback message “Computing CFG for function” is emitted each time we click
the button, which means we perform a new visit. For large computations and programs, this

                                   2.4. THE VIEWCFG PLUG-IN

                  Figure 2.4: Mini-GUI with Bogue for testing our plug-in.

is wasteful, and we should be able to easily cache the result. The next section will show how
to do it using states.

2.4.5   Saving/Loading Data, and Usability in a Multi-Project Setting

Registering and using state
In this section, we will learn how to register state into Frama-C. A state is a piece of in-
formation kept by a plug-in. For instance, we can use a boolean state to store whether an
expensive analysis has been executed, to avoid recomputing it. Another example of state:
the Eva plug-in computes, for each statement, a table associating to each AST variable a set
of values the program may have at runtime; this association table is a state.
State registration provides several features:

  • It allows the state to be saved and reloaded with the rest of the session, for instance
    when using frama-c -save/frama-c -load;

  • It helps maintaining consistency between the AST and the results and parameters of
    the analysis of the different plug-ins.

We will modify our Dump module to output the DOT graph as a string, and store it in a
hash table from fundec to string. Storing this string will allow us to memoize [15] our
computation: the string is computed the first time the CFG of a function is displayed, while
the following requests will reuse the result of the computation. Registering the hash table
as a Frama-C state is mandatory to ensure Frama-C consistency: for instance, by using a
standard OCaml hash table, a user that would have loaded several sessions through a GUI
could observe the CFG of function of a previous session instead of the one he wants to observe.
Registering a state is done by a functor application:
     module Cfg_graph_state = State_builder.Hashtbl
          let name = "Dump.Cfg_graph_state"
          let dependencies = [ Ast.self; Eva.Analysis.self ]
          let size = 17

The State_builder module provides several functors that help registering states.
State_builder.Hashtbl allows the developer to create a hash table. It is parameterized

                                            CHAPTER 2. TUTORIAL

by a module describing the hash table and its key, a module describing the data associated
to keys, and other information.
The Datatype and Cil_datatype modules describe the hash table and its associated data,
and explain for instance how the datatype should be copied, printed, or marshalled to the
disk. They are part of the Type library [18], described in Section 4.7. Datatype provides de-
scriptions for standard OCaml types, and Cil_datatype for the CIL types (in the Cil_types
The last module argument describes the initial size of the hash table16 , a name (mainly used
for internal debugging), and a list of dependencies. Here we expressed that our hash table
depends on the AST and the results of the Eva plug-in. For instance, whenever the Frama-C
kernel updates one of these states, it will automatically reset our hash table. This ensures
consistency of the analysis: if the AST of a function changes, or the value analysis is executed
with a different entry point, this potentially affects the display of the control flow graph, that
we must recompute.
Once the module has been declared, it is fairly easy to use it.
        let dump_to_string fundec =
 "Computing CFG for function %s"
            ( Visitor .visitFramacFunction (new Visit.print_cfg Format.str_formatter) fundec);
          Format.flush_str_formatter ()

        let dump_to_string_memoized = Cfg_graph_state.memo dump_to_string

        let dump_function fundec fmt =
          Format.fprintf fmt "digraph %s {\n%s\n}\n"
            (dump_to_string_memoized fundec)

dump_function now takes two steps: first the CFG is printed to a string, then the string
is printed to the fmt argument. This allows the dump_to_string part to be memoized, i.e.
the results of dump_to_string are saved so that later calls to dump_function with the same
fundec argument reuse that result.
To check this, we re-run our mini-GUI with:
        $ dune exec -- frama-c <file> -cfg-gui

The first graph for each function will show the message “Computing CFG for function ...”,
but subsequent calls will no longer do it.
Also, we can see the effects of the dependency on the Eva plug-in by first launching the value
analysis and then our plug-in:
        $ dune exec -- frama-c <file> -eva -then -cfg-gui

In this case, the graphs will be colored.
Finally, to check that the state dependency on Eva works, we will use a more complex
command line:
        $ dune exec -- frama-c <file> -eva -then -cfg-gui -then -main f
      This initial size is an optimization feature; the table automatically grows when needed.

                                   2.4. THE VIEWCFG PLUG-IN

We have three stages: first run Eva, then open the mini-GUI, then change the entry point
(-main f means that the program will start executing from function f) and re-open the mini-
GUI. Remember that most Frama-C options persist from one stage to the next: the same way
that we do not have to repeat -eva after the first -then, we do not have to repeat -cfg-gui
after the second -then. If we want to avoid re-running the mini-GUI in future stages, we
need to use apply_once, as mentioned in Section 2.4.2.
What we observe is the following: when the mini-GUI opens, we click Show CFG, see a
“Computing CFG for function ...” message, and get a mostly-green CFG. Then, we close the
mini-GUI, and it opens again. Clicking Show CFG will show the same “Computing CFG”
message, but the graph will be entirely pink: with f as the entry point, function main is never
called, therefore entirely unreachable. Because the entry point changed, and Eva depends on
its state, it is automatically recomputed. Because our plug-in depends on Eva’s state, it
recomputes the graph when we ask again for the CFG.
Another way to observe how Frama-C automatically handles states is to display a CFG, save
the session (option -save <file>), and then load it again:
     $ dune exec -- frama-c <file> -eva -then -cfg-gui -save session.sav

Then click on the “Show CFG” (see the feedback message), then close the CFG and the
mini-GUI. Reload the session:
     $ dune exec -- frama-c -load session.sav

Click “Show CFG” and you will not see the “Computing CFG” message: the state
Cfg_graph_state had beem automatically saved by Frama-C and has just been loaded from
the session.

Clearing states, selection and projects
There is one caveat though: if the user computes the CFG before running the Eva analysis,
and then runs Eva, they will not see a colored graph (unless they re-launch Eva with different
parameters). This is because the state of the CFG is reset when the state of Eva is reset, not
when it is first computed.
To solve this problem, we will manually reset the Cfg_graph_state if we detect that Eva
has been run since the last time we computed the CFG. For that, we have to remember the
previous value of Eva.Analysis.is_computed (), i.e. to register another state:
     module Eva_is_computed = State_builder.Ref
          let name = "Dump.Eva_is_computed"
          let dependencies = []
          let default () = false

This new state only consists of a reference to a boolean value.
Then we just replace dump_function in the code above by the following.
     let dump_function fundec fmt =
        if not (Eva_is_computed.get ()) && Eva.Analysis.is_computed () then begin
          Eva_is_computed.set true;
           let selection = State_selection.with_dependencies Cfg_graph_state.self in
          Project. clear ∼ selection ();

                                      CHAPTER 2. TUTORIAL

       Format.fprintf fmt "digraph %s {\n%s\n}\n"
         (dump_to_string_memoized fundec)

The only parts that need to be explained are the notions of selection and project. A selection
is just a set of states; here we selected the state Cfg_graph_state with all of its dependencies,
as resetting this state would also impact states that would depend on it (even if there are
none for now). We use Project.clear to reset the selection.

Project explanation
A project [17] is a consistent version of all the states of Frama-C. Frama-C is multi-AST,
i.e.Frama-C plug-ins can change the AST of the program, or perform incompatible analyses
(e.g. with different entry points). Projects consistently group a version of the program’s AST
with the states related to it.
The Project.clear function has type:
     val clear : ? selection : State_selection .t → ?project:t → unit → unit

The arguments selection and project can be seen as a coordinate system, and the function
allows to clear specific versions of specific states. By default, Frama-C functions act on the
current project. The developer has to use Project.on or optional arguments to act on
different projects. Frama-C automatically handles duplication and switch of states when
duplicating or changing of projects. This is the last benefit of state registration.
To summarize:

  • To store results, plug-ins should register states;

  • A project is a consistent version of all the states in Frama-C, together with a version of
    the AST;

  • A session is a set of projects;

  • Frama-C transparently handles the versioning of states when changing or duplicating
    projects, saving and reloading sessions from disk, etc.

  • The version of the state in a project can change; by default Frama-C functions operate
    on the current project.

  • A selection is a set of states. Dependencies allow to create selections.

  • As a plug-in developer, you have to remember that is up to you to preserve consistency
    between your states and their dependencies by clearing the latter when the former is
    modified in an incompatible way. For instance, it would have been incorrect not to call
    State_selection.with_dependencies in the last code snippet of this tutorial.

Projects are generally created using copy visitors. We encourage the reader to experiment
with multi-project development by using them. An interesting exercise would be to change
the AST so that execution of each instruction is logged to a file, and then re-read that file to
print in the CFG how many times each instruction has been executed. Another interesting
exercise would be to use the apply_once function so that the ViewCfg plug-in is executed
only once, as explained in section 2.4.2 of this tutorial.

                                                                                Chapter 3

                                                 Software Architecture

Target readers: beginners.

In this chapter, we present the software architecture of Frama-C. First, Section 3.1 presents
its general overview. Then, we focus on four different parts:

  • Section 3.2 explains what a plug-in really is and the main mechanisms of plug-in inte-

  • Section 3.3 introduces the libraries that Frama-C provides.

  • Section 3.4 introduces the kernel services that plug-in developers might want to use.

  • Section 3.5 introduces the kernel internals. You can safely skip it if you are not a
    Frama-C kernel developer.

3.1     General Description

From a plug-in developer point of view, the main goals of the Frama-C platform is to provide
services to ease:

  • analysis and source-to-source transformation of big-size C programs;

  • addition of new plug-ins; and

  • plug-ins collaboration.

In order to reach these goals, Frama-C has a plug-ins based software architecture based on a
kernel. Historically the kernel was itself based on Cil [16]: even if they have evolved separately
since the Frama-C Hydrogen age, there are still a lot of similarities between Cil and several
modules of the Frama-C kernel (e.g. the ASTs).
The Frama-C architecture design is presented in this chapter, and summarized in Figure 3.1.
In this figure, each of the four rounded colored boxes represents a subdirectory d of directory
src, while each of the small square boxes represents a subdirectory in one subdirectory
src/d. The remaining sections will explain the goal of each of these boxes. They do not
detail each module of each directory: use the API documentation generated by make doc for
that purpose.



                plug-in 1      plug-in 2    ...      plug-in n

                            Kernel Services

      AST Traversal
               visitor                                  ast_queries

analysis      ast_transformations                        parsetree

                AI                                Plug-in Interactions
           abstract_interp                          cmdline_parameters


    Kernel Internals
 parsing       typing        runtime                 datatype        project


              Figure 3.1: Frama-C Architecture Design.

                                           3.2. PLUG-INS

3.2     Plug-ins

In Frama-C, plug-ins are program analysis or source-to-source transformations. The ones
provided within Frama-C are in directory src/plugins/plugin_name. Each plug-in is an
extension point of Frama-C which has to be registered through Plugin.Register (see Sec-
tion 4.5). Frama-C allows plug-in collaborations: a plug-in p can use a list of plug-ins p1 , . . . ,
pn and conversely. Mutual dependences between plug-ins are even possible. If a plug-in is
designed to be used by another plug-in, it has to register its API either by providing a .mli
file, or through modules Dynamic or Db. The first method is the preferred one, the second
one (through module Dynamic) is the only possible one to define mutually dependent plug-ins
while the third one (through module Db) is now fully deprecated even if most of the older
Frama-C plug-ins are still defined this way.

3.3     Libraries

Libraries are defined in the directory src/libraries. They are either third-party libraries
or dedicated independent libraries which may be used by other parts of Frama-C.
Extension of the OCaml standard library are provided in directory src/libraries/stdlib.
For instance, modules FCmodule_name (e.g. FCHashtbl) provides a module_name-like in-
terface (e.g. Hashtbl) with an uniform API for all OCaml versions supported by Frama-C
and possibly additional useful operations for the corresponding datastructures.
Single-file libraries are provided in directory src/libraries/utils.                 For instance,
Pretty_utils provides pretty-printing facilities.
datatype      (directory     src/libraries/datatype)    and   project    (directory
src/libraries/project) are two multiple-files libraries. They are respectively pre-
sented in Sections 4.7 and 4.9.

3.4     Kernel Services

The kernel services is defined in directory src/kernel_services. It is the part of the Frama-
C kernel which may be useful to develop plug-ins.
This services may be split in four main parts:

   • two ASTs and the data structures directly built upon them;

   • plug-in interactions toolbox;

   • predefined generic analyzers;

   • the abstract interpretation framework.

The standard AST used by most analyzers is defined in module Cil_types of direc-
tory src/kernel_services/ast_data. It contains the types which describes both the
C constructs and the ACSL ones [1]. The same directory also contains modules defin-
ing datastructures directly based upon the AST (module Globals), functions (module
Kernel_function), annotations (module Annotations) and so on. A related directory is

                             CHAPTER 3. SOFTWARE ARCHITECTURE

src/kernel_services/ast_queries. It contains modules which provides specific operations
in order to get information about AST-related values.
In the same way, an untyped AST quite close of the C input source is defined in module Cabs
of directory src/kernel_services/parsetree. This AST is only well suited for syntactic
analyzers/program transformers.
Frama-C also provides services to plug-ins which help both their integration in the plat-
form and their interactions with the kernel and the other plug-ins.        They enforce
some platform-wide consistency by ensuring that some common actions (e.g. print-
ing messages to end-users) are handled by all plugins in a similar way. Directory
src/kernel_services/cmdline_parameters provides modules which eases the definition of
analyzers’ parameters accessible by the end-user through command-line options. Similarly,
directory src/kernel_services/plugin_entry_points provides modules to interact with
the Frama-C kernel or other plug-ins.
Next, Frama-C provides predefined ways to visit the ASTs, in particular through
object-oriented visitors defined in directory src/kernel_services/visitors (see Sec-
tion 4.15).    Some predefined analyzers, such as a multiple generic dataflow anal-
ysis are provided in directory src/kernel_services/analysis, while some prede-
fined program transformation, such as cloning a function, are provided in directory
src/kernel_services/ast_transformations. Finally, Frama-C provides an abstract in-
terpretation toolbox with various lattices in directory abstract_interp.

3.5     Kernel Internals

Target readers: kernel developers.

The kernel internals is defined in directory src/kernel_internals. It is part of the Frama-C
kernel which should be useless to develop analysis plug-ins, except possibly for very low-level
interactions, or to extend the C or ACSL services of Frama-C. Consequently, if you are not
a kernel developer, you can safely ignore this section.
The internals is split in three different parts, each of them being an independent subdirectory:

  • the directory src/kernel_internals/parsing contains the lexer and parser which
    generate the untyped AST (aka Cabs) from the C input source code;

  • the directory src/kernel_internals/typing contains the compiler which generates
    the standard AST (aka Cil) from the untyped one;

  • the directory src/kernel_internals/runtime contains modules whose primary pur-
    pose is to perform side-effects while Frama-C is booting.

                                                                                            Chapter 4

                                Advanced Plug-in Development

This chapter details how to use services provided by Frama-C in order to be fully operational
with the development of plug-ins. Each section describes technical points a developer should
be aware of. Otherwise, one could find oneself in one or more of the following situations 1
(from bad to worse):

   1. reinventing the (Frama-C) wheel;

   2. being unable to do some specific things (e.g. saving results of an analysis on disk, see
      Section 4.9.2);

   3. introducing bugs in his/her code;

   4. introducing bugs in other plug-ins using his/her code;

   5. breaking the kernel consistency and so potentially breaking all Frama-C plug-ins (e.g.
      if s/he modifies the AST without changing project, see Section 4.9.5).

In this chapter, we suppose that the reader is able to write a minimal plug-in like hello
described in chapter 2 and knows about the software architecture of Frama-C (chapter 3).
Moreover plug-in development requires the use of advanced features of OCaml (module sys-
tem, classes and objects, etc). Plug-in development also requires some familiarity with the
Dune build system.
Note that the following subsections can be read in no particular order: their contents are
indeed quite independent from one another even if there are references from one section to
another one.

4.1      Plug-in dependencies

Target readers: standard plug-in developers.

Prerequisite: Basic knowledge of the Dune build system.
    It is fortunately quite difficult (but not impossible) to fall into the worst situation by mistake if you are
not a kernel developer.

                           CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

Some plug-ins only depend on the Frama-C kernel, and in this case, require no special con-
figuration. However, many plug-ins depend either on other Frama-C plug-ins, or on external
libraries, tools and components. In both cases, it is important to specify such dependencies,
to avoid the user trying and failing to compile or run your plug-in.
Plug-in dependencies are usually defined in the plug-in’s dune file. There are mainly two
kinds of dependencies: mandatory and optional. Mandatory dependencies are necessary for
the plug-in to run at all, and their absence means the plug-in must be disabled. Optional
dependencies do not prevent compilation and usage of the plug-in, but it may work less
efficiently, precisely, or fail when specific features are requested.

 Plug-in developers must ensure that optional dependencies are tested for their absence and
 dealt with gracefully; a plug-in must not crash when optional dependencies are missing.

Most dependencies (OCaml library dependencies, such as other plug-ins or OCaml mod-
ules) are specified using Dune’s library stanza2 . As is often the case, examples are very
instructive; here is an example of mandatory dependencies from the Dive plug-in’s dune file:
      ( library
         ( libraries frama-c.kernel frama-c-studia.core frama-c-server.core)

The libraries field contains frama-c.kernel (essential for all plug-ins), but also
frama-c-studia.core and frama-c-server.core, meaning this plug-in requires both the
Studia and Server plug-ins to be enabled. If any of them is disabled (either due to missing
dependencies, or as a result of a user request), then Dive will also be disabled.
Note: to explicitly disable a plug-in, use the dev/ script.
Note that OCaml libraries can also be specified, e.g. adding zarith to libraries above
would require that Zarith be installed and available via ocamlfind.

4.1.1    Declaring dependencies

Optional dependencies can be detected and disabled in different ways:

   • If the module is dynamically accessible via Db (see Section 4.8.2 for more details), the
     detection can be done directly in OCaml and requires no special handling in the dune

   • Otherwise, you can define two versions of the implementation (both implementing the
     same interface), in two different files. One of these files will use the required module,
     while the other will implement a dummy version without it. The select notation from
     the library stanza allows telling Dune which file to compile.

Here is an example of select from the Aoraï plug-in, which defines an optional dependency
on the Eva plug-in:
      ( libraries [...]
       ( select from
        (frama-c-eva.core →
    Full documentation about Dune’s |library| stanza is available at

                                    4.2. FRAMA-C MAKEFILES

         ( →

In the example above, Aoraï defines two files: and (we recommend this naming convention, but it is not
enforced by dune). The general form of the select stanza is:
      ( select < file> from
         (< cond_1> → < file_1> )
         (< cond_2> → < file_2> )
         ( → < default> )

It then checks for each condition <cond_i> in order, and the first one that matches is selected,
otherwise it will be the fallback/default one. The selected <file_i> will be renamed to
<file> and used in the build.

4.1.2     Notifying users via frama-c-configure

Frama-C has a special Dune target, @frama-c-configure, which prints a summary of the con-
figuration as seen by Dune when run via dune build @frama-c-configure. It is especially
helpful to understand why a given plug-in is disabled.
Plug-in developers should always include such a section in their dune file, listing each optional
library and its current availability, via the %{lib-available:<lib>} special variable.
Here is an example from Frama-Clang, which requires the following libraries:
      ( libraries frama-c.kernel frama-c-wp.core camlp-streams zarith)

Its plug-in library name is frama-clang.core. Its availability must be displayed as the
“summary” of the configuration, written as the first line, with each dependency as a subitem:
       ( alias frama-c-configure)
       (deps (universe))
       (action (progn
                 (echo "Clang:" %{lib-available:frama-clang.core} "\n")
                 (echo " - zarith:" %{lib-available: zarith } "\n")
                 (echo " - camlp5:" %{lib-available:camlp5} "\n") ; for gen_ast
                 (echo " - camlp-streams:" %{lib-available:camlp-streams} "\n")
                 (echo " - wp:" %{lib- available :frama-c-wp.core} "\n")

Note that camlp5 is not among the dependencies declared in libraries; it is used by another
component, gen_ast.

4.2      Frama-C Makefiles

Target readers: standard plug-in developers.

Prerequisite: Knowledge of make.

                          CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

Since the adoption of Dune, Frama-C’s Makefiles were largely simplified. They are still used
for some tasks, partially due to conciseness (make is shorter than dune build), partially
because some tasks are better suited for them. Some standard targets are defined in various
Makefiles that are installed in Frama-C’s shared directory.
A minimal plugin’s Makefile can thus be the following:

 File Makefile

      FRAMAC_SHARE:=$(shell frama-c-config -print-share-path)

      ## Common definitions

      include ${FRAMAC_SHARE}/Makefile.common

      ## Tests−related targets

      include ${FRAMAC_SHARE}/Makefile.testing

      ## Installation−related targets

      include ${FRAMAC_SHARE}/Makefile.installation

Makefile.testing introduces various targets related to Frama-C’s testing infrastructure (see
Section 4.3). This includes notably tests to run all the tests of the plugin, after having taken
care of generating the corresponding dune files.
Makefile.installation provides two targets, install and uninstall. By default, instal-
lation will occur in the current opam switch, but this can be modified by using the PREFIX
variable (note that if you install your plugin in a non-default place, you will have to explicitly
instruct Frama-C to load it through option -load-plugin.
Other Makefiles include Makefile.documentation, providing the doc for generating the
documentation (see Section 2.3.8), and Makefile.linting which is used by Frama-C itself
to perform various syntactic checks through target check-lint and fix indentation issues
through lint. If you want to use the same conventions as Frama-C itself, you’ll need to have
ocp-indent installed to launch these targets.

4.3     Testing

In this section, we present ptests, a tool provided by Frama-C in order to perform non-
regression and unit tests.

 Historically, ptests has been developed before Frama-C switched to Dune. It has been
 ported to Dune, but some features had to be adapted and others became redundant; it
 is likely that in the future ptests will be replaced with direct usage of the Dune testing

ptests is a test preparation tool that parses specially crafted C comments to create several
Dune test targets, so that users can more easily create test cases with custom Frama-C
The generated test targets are then run via Dune. Each result of the execution is compared
with the previously saved result (called the oracle). A test is successful if and only if there is

                                         4.3. TESTING

no difference. Actually, the number of results is twice the number of tests, because standard
and error outputs are compared separately.
First, Section 4.3.1 explains how to use ptests. Next, Section 4.3.2 describes the test file
structure for Frama-C plug-ins. Section 4.3.2 introduces the syntax of test headers, that
is, how to define test cases and their options. Section 4.3.3 explains how to declare test
dependencies (files other than the test itself). Last, Section 4.3.4 presents the full list of
ptests directives.

4.3.1   Using ptests

ptests only prepares tests (by creating appropriate dune files), but does not run them. When-
ever a new test file is added, or test headers of existing test files are modified, you need to
run frama-c-ptests to regenerate them. Note that, to run all of Frama-C tests (which in-
clude several directories, plus the tests of many plug-ins), you should run make run-ptests
instead, which will call frama-c-ptests with the proper arguments to generate test targets
for all directories.
If new tests are created (by adding a new file, or adding an extra test case to an existing
file), you must run frama-c-ptests -create-missing-oracles. This will create empty test
oracles for Dune.
Then, to run the tests, use dune build @ptests. If there are differences between the current
run and oracles from previous runs, Dune will indicate them and mark the tests as failures.
If the changes are intended, after manual inspection you can promote them as new oracles,
via dune promote. This will simply replace the existing oracles with the new ones. Finally,
you can use frama-c-ptests -remove-empty-oracles to remove empty oracles (typically,
messages sent to the standard error) before committing the files to version control.
If you simply want to re-run all tests for your plug-in, run make tests.

4.3.2   Test directory structure

This is the file structure of the tests directory, where Frama-C plug-ins are expected to place
their tests:
     < plug-in directory>
     +- tests
        +- ptests_config
        +- test_config
        +- suite1
           +- test1.c
           +- ...
           +- oracle
              +- test1.res. oracle
              +- test1.err. oracle
              +- ...
           +- result
              +- test1.res.log
              +- test1.err.log
              +- ...
       +- ...

                          CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

Files test_config and ptests_config
Inside tests, two files are mandatory: ptests_config and test_config.
ptests_config usually contains a single line with the list of test suites for that plug-in,
prefixed with DEFAULT_SUITES=. A test suite is a sub-directory of the current tests directory.
     DEFAULT_SUITES=basic parsing misc options

In the example above, our plug-in has at least four sub-directories inside the tests directory.
Each test suite can contain any number of test files.
test_config contains a list of common directives to be applied to each test, in all test suites.
It typically contains a line PLUGIN: <module> with the name of the plug-in being developed
(for more details about PLUGIN:, check Section 4.3.4).
Each test suite can also contain its own test_config file. Each test case in that suite will then
inherit the directives from the parent test_config as well as those from the test_config
in its directory.
Finally, different test configurations can be specified by creating other files, e.g. the existence
of a file test_config_prove will create a configuration named prove. A test case can
contain multiple test headers (to be detailed in the next section), with different directives for
each configuration. Configurations are specified when running tests, e.g. instead of running
dune build @ptests, you can run instead dune build @ptests_config_prove to run tests
only from the prove configuration.

 All Dune @ptests-related targets must be run after frama-c-ptests (or
 make run-ptests) has been run, otherwise Dune may not find the generated files
 and report errors such as Alias "ptests_config" specified on the command line is empty.

The catch-all command make tests run tests for all suites, and all configurations.

Test headers
Inside each test suite, we find one or more test files: either .c or .i files which typically start
with the following header:
     /* run.config
       // test directives, one per line

That is, a multiline C comment block (/* */) with run.config and a list of lines containing
test directives. This test header tells ptests how to generate the test commands.
Note that a configuration suffix can be added to run.config. Also, we can define multiple
test headers, such as:
     /* run.config
     /* run.config_eva
       STDOPT: +"-eva"

This will create a test case for the default configuration, and a different one for the eva
Multiple configurations may share the same set of directives:

                                                 4.3. TESTING

       /* run.config, run.config_< name>               [, ...]
          ... common directives ...

The following wildcard is also supported, and matches any configuration: /* run.config* .
Note that it does not define a new configuration, but generates tests for every existing con-
figuration in the directory (as defined by the existence of test_config_* files).

oracle and result directories
Inside each test suite, there are two directories, oracle and result3 , each containing at least
one file per test case (remember that a single test file can contain several test cases, one per
The oracle directory contains the test oracles, that is, the expected results saved from
previous runs.
The result directory contains the generated Dune files produced by ptests.

  The naming of these directories is due to historical reasons; the result directory used
  to contain the current test outputs, which were then compared to the oracles, mirroring
  their directory structure. Nowadays, it could be called targets, for instance.

Oracle files are named <test_name><optional_test_number>.<stream>.oracle.
<test_name> is simply the filename of the test file, minus its extension4 .
<optional_test_number> is a 0-numbered list of test numbers for files with multiple
tests: .0, then .1, .2, etc. It is omitted if the test file defines a single test case. <stream>
is out for stdout (standard output) and err for stderr (standard error). Therefore, there
are two oracle files for each test case. An absent oracle is equivalent to an empty one.
Files in result are named <test_name>.<test_number>.exec.wtests (or, in case there are
EXECNOW5 directives, they end with .execnow.wtests). They are always 0-numbered, even
when there is a single test case per file. These are JSON files containing the data to be used
(by frama-c-wrapper via the generated dune file) in each test, e.g. the command-line to be
run, the output file name, and the associated oracle. These .wtests files are not generated
when the use of frama-c-wrapper is not required (via ptests’ option -wrapper "").

4.3.3     What happens when you run a test

Complex tests using relative paths or extra files require understanding how Dune runs the
tests, so that they can be properly written.
By default, Dune will create a _build directory where it stores compiled files and other
resources the user may request. When a test is run, Dune will copy the test file and its
dependencies (detailed in the next section) to a subdirectory inside _build (usually, mirroring
the original directory structure), cd to the test subdirectory, and run the test command from
there. It will redirect the standard and error streams to two files (<test>.res.log and
<test>.err.log), and compare them to the test oracles. If they are identical, by default
     If there are other configurations, there will also be an oracle_<config> and a result_<config> directory
per configuration.
     Note that this prevents having two tests in the same suite which differ only by their extension, e.g. test1.c
and test1.i.
     See Section 4.3.4 for details about this and other directives.

                                CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

Dune will not report anything. Otherwise, it will print a message and the diff between the
current result and the previous oracle.

Test dependencies
Dune tracks dependencies between files so that it knows when objects must be rebuilt and
tests must be run again. For compiling OCaml files, it usually computes this information
automatically. For tests, however, such information must come from the user. ptests will use
it to generate Dune rules that will ensure tests are re-run if their dependencies are modified.
Properly annotating test dependencies is essential to ensure reproducible, parallelizable tests.
Otherwise, non-deterministic behavior may occur.
One way to declare dependencies is to use a DEPS directive6 with a space-separated list of
files. For instance, a test file.c which #includes a file.h must declare it as a dependency:
        /∗ run.config
           DEPS: file.h
        #include "file.h"

When tests mention their dependencies in the command line, a shorter syntax is available,
using the Dune special variable %{dep:<file>}. For instance, tests from saveload typically
consist of multiple sub-tests, one creating a session file with -save and another loading it with
-load. The second test obviously must run after the first one; adding the dependency will
ensure that Dune will sequence them correctly. In the example below, each STDOPT directive
defines a test case.
        /∗ run.config
           STDOPT: +"−save test1.sav"
           STDOPT: +"−load %{dep:test1.sav}"

You can combine DEPS and %{dep:} as you wish in your tests. Prefer %{dep:} for local
dependencies, since it does not accumulate towards following tests, and DEPS for dependencies
which are common to several tests.
Note that forgetting to specify dependencies can lead to test failures in unexpected ways,
such as the dependencies not being copied to Dune’s test directory, or two tests running in
parallel and reading/writing concurrently to the same file.

Working directory and relative paths
Any directive can identify a file using a relative path. The current working directory (con-
sidered as .) will be a directory inside Dune’s sandbox, that is, a result directory inside
the “mirror” directory of the test file. This “mirror” directory structure is created by Dune
(by default, inside a _build directory in the root of the Dune project), with dependencies
copied lazily for each test. Therefore, pay attention to the fact that references to the parent
directory (..) will likely not match what you expect.
      Section 4.3.4 provides details about ptests directives.

                                         4.3. TESTING

4.3.4     Detailed directives

Directives can have various functions: some create test cases, while others modify the envi-
ronment (and therefore affect other directives). Each directive is specified in a separate line
and has the form
       DIRECTIVE: value (everything until the newline character)

Example 4.1 Test tests/sparecode/calls.c declares the following directives.
       /* run.config
          OPT: -sparecode-analysis
          OPT: -slicing-level 2 -slice-return main -slice-print

These directives state that we want to test sparecode and slicing analyses on this file. Two
test cases are defined, each with its specific set of options. The default command (frama-c)
will be run with these arguments, plus the test file name, plus a few other implicit options
(-check, -no-autoload-plugins, -load-module, etc).

Table 4.1 shows all the directives that can be used in the configuration header of a test (or
a test suite). Those whose name are underlined are the directives that actually create test
cases; the others modify or disable test cases.

 Name         Specification                                            default
 CMD          Program to run.                                          frama-c
 COMMENT      A configuration comment; this directive does nothing.    None
 DEPS         The list of files this test depends on.                  None
 DONTRUN      Disable this test file for the current configuration.    None
 EXECNOW      Run a custom command.                                    None
 EXIT         Indicate expected exit code, if not 0.                   None
 FILEREG      File name pattern of files considered as test cases.     .*\.\(c|i\)
 FILTER       Command reading the standard input used to filter        None
              results. In such a command, the predefined macro
              @PTEST_ORACLE@ is set to the basename of the oracle.
 LIBS         Libraries to be loaded with each subsequent run (their   None
              compilation is not managed by ptests, contrary to the
              modules of MODULE directive).
 LOG          Add an additional file that the test must generate and   None
              compare against an oracle. Note that this directive is
              only used by ‘OPT‘ and ‘STDOPT‘ directives. The
              syntax for EXECNOW related to that need is different
              (see the description of EXECNOW directive).
 MACRO        Define a new macro.                                      None
 MODULE       Register a dynamic module to be built and loaded with    None
              each subsequent test.
 NOFRAMAC     Empty the list of frama-c commands to be launched        None
              (EXECNOW directives are still executed). Used when the
              test must not run |frama-c|, but another command.

                          CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

 OPT          Options given to the program.                            None (but usually de-
                                                                       fined in test_config)
 PLUGIN       Plugins to be loaded with each subsequent run.           None (but usually de-
                                                                       fined in test_config)
 STDOPT       Add and remove options from the default set (see text    None
              for syntax details).
 TIMEOUT      Kill the test after the given duration (in seconds of None
              CPU user time) and report a failure.
                  Table 4.1: Directives in configuration headers of test files.
                  Underlined directives are the only ones which actually gen-
                  erate test cases.

In the following, we detail some aspects of several directives.

  • DONTRUN and NOFRAMAC directives do not need any content, but it might be useful to
    provide an explanation of why the test should not be run (e.g test of a feature that is
    under development and not fully operational yet).

  • CMD allows changing the command that is used for the following OPT directives (until
    a new CMD directive is found). No new test case is generated if there is no further OPT
    directive. For a given configuration level, the default value for directive CMD is the last
    CMD directive of the preceding configuration level.

  • LOG adds a file to be compared against an oracle in the next OPT or STDOPT directive.
    Several files can be monitored from a single OPT/STDOPT directive, through several LOG
    directives. These files must be generated in the result directory of the corresponding
    suite (and potentially alternative configuration). After an OPT or STDOPT directive is
    encountered, the set of additional LOG files is reset to its default. Note that EXECNOW
    directives can also be prefixed with LOGs, but they are written in the same line, without
    the separating colon (:).

  • By default, the test command (usually, frama-c) is expected to return successfully (i.e.,
    with an exit status of 0). If a test is supposed to lead to an error, an EXIT directive
    must be used. It takes as argument an integer (typically 1 to denote a user error)
    representing the expected exit status for the subsequent tests. All tests triggered by
    OPT or STDOPT directives encountered after the EXIT directive will be expected to exit
    with the corresponding status, until a new EXIT directive is encountered. (EXIT: 0 will
    thus indicate that subsequent tests are expected to exit normally).

  • If there are several OPT directives in the same configuration level, they correspond to
    different test cases. The OPT directives of a given configuration level replace the ones
    of the preceding level.

  • The STDOPT directive takes as default set of options the last OPT directive(s) of the
    preceding configuration level. If the preceding configuration level contains several OPT
    directives, hence several test cases, STDOPT is applied to each of them, leading to the
    same number of test cases. The syntax for this directive is the following.

                                     4.3. TESTING

         STDOPT: [[+#-]"opt" ...]

  unlike in OPT, here options are always given between quotes. An option following
  a + (resp. #) is added to the end (resp. start) of the current set of options, while an
  option following a - is removed from it. The directive can be empty (meaning that
  the corresponding test will use the standard set of options). As with OPT, each STDOPT
  corresponds to a different (set of) test case(s). LOG directives preceding an STDOPT are
  taken into account.

• The syntax for EXECNOW directives is the following.

         EXECNOW: [ [ LOG file | BIN file ] ... ] cmd

  Files after LOG are log files generated by command cmd and compared from oracles,
  whereas files after BIN are binary files, also generated by cmd, but not compared to
  any oracles. Full access path to these files has to be specified only in cmd. Execution
  order between different OPT/STDOPT/EXECNOW directives is unspecified, unless there are
  dependencies between them (see DEPS directive). EXECNOW directives from a given level
  are added to the directives of the following levels.
  Note: An EXECNOW command without BIN and without LOG will not be be executed by
  Dune; a warning is emitted in this case.

• The MACRO directive has the following syntax:

         MACRO: macro-name content

  where macro-name is any sequence of characters containing neither a blank nor an @, and
  content extends until the end of the line. Once such a directive has been encountered,
  each occurrence of @macro-name@ in a CMD, LOG, OPT, STDOPT or EXECNOW directive at
  this configuration level or in any level below it will be replaced by content. Existing
  predefined macros are listed in section 4.3.5.

• The MODULE directive takes as argument the name of a .cmxs module. It will then add
  a directive to compile this file with the command @PTEST_MAKE_MODULE@ <MODULE>
  where @PTEST_MAKE_MODULE@ defaults to make -s. Option -load-module <MODULE>
  will then be appended to any subsequent Frama-C command triggered by the test.

• The LIBS directive takes as argument the name of a .cmxs module. The -load-module
  <LIBS> will then be appended to any subsequent Frama-C command triggered by the
  test. The compilation is not managed by ptests.

• The FILEREG directive contains a regular expression indicating which files in the direc-
  tory containing the current test suite are actually part of the suite. This directive is
  only usable in a test_config configuration file.

                        CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

 • The FILTER directive specifies a transformation on the test result files before the com-
   parison to the oracles. The filtering command read the result from the standard input
   and the oracle will be compared with the standard output of that command. In such a
   directive, the predefined macro @PTEST_ORACLE@ is set to the basename of the oracle.
   That allows running a diff command with the oracle of another test configuration

      FILTER: diff --new-file @PTEST_DIR@/oracle_config/@PTEST_ORACLE@ -

    Chaining multiple filter commands is possible by defining several FILTER directives
    (they are applied in the reverse order), and an empty command drops the previous
    FILTER directives.
 • The DEPS directive takes a set of filepaths and adds them to the set of dependencies
   for the next OPT/STDOPT/EXECNOW directives. Whenever these dependencies change,
   the test cases depending on them must be re-run. Otherwise, Dune does not re-run
   successful tests. Dependencies also ensure that tests which require output from others
   are run serially and not in parallel. Note that Dune also has a special variable notation
   which can be used to specify dependencies: %{dep:<file>}. For instance, the following

             DEPS: file1.h file2.c
             OPT: -cpp-extra-args="-Ifile1.h" file2.c

    Is equivalent to:

             OPT: -cpp-extra-args="-I%{dep:file1.h}" %{dep:file2.c}

    The special variable notation is interpreted by Dune before executing the command.
    All dependencies (either via DEPS or %{dep:}) are collected and added to the set of
    dependencies for the test case.
 • If there are OPT/STDOPT directives after a NOFRAMAC directive, they will be executed,
   unless they are themselves discarded by another subsequent NOFRAMAC directive.

@ in the text of a directive As mentioned above, @ is recognized by ptests as the
beginning of a macro. If you need to have a literal @ in the text of the directive itself, it
needs to be doubled, i.e. @@ will be translated as @.

Summary: ordering of test executions
There is no total ordering between the tests in a test file header. The only ordering is
dictated by the dependencies declared in the test cases. Dune will by default run tests in
A consequence of this ordering is that, if you need a test to produce output that will be
consumed by another test, the consumer must declare the produced file as a dependency.

                       4.4. PLUG-IN MIGRATION FROM MAKEFILE TO DUNE

4.3.5   Pre-defined macros for tests commands

Table 4.2 gives the definition of the most important predefined macros that can be used in
ptests’ directives. Refer to frama-c-ptests –help to have the full list.

 Name                    Expansion
 frama-c                 path to Frama-C executable
 PTEST_CONFIG            either the empty string or _ followed by the name of the
                         current alternative configuration (see section 4.3.2).
 PTEST_DIR               current test suite directory
 PTEST_FILE              path to the current test file
 PTEST_NAME              basename of the current test file (without suffix)
 PTEST_NUMBER            rank of current test in the test file. There are in fact two in-
                         dependent numbering schemes: one for EXECNOW commands
                         and one for regular tests (if more than one OPT).
 PTEST_RESULT            shorthand alias to @PTEST_DIR@/result@PTEST_CONFIG@
                         (the result directory dedicated to the tested configuration)
 PTEST_ORACLE            basename of the current oracle file (macro only usable in
                         FILTER directives)
 PTEST_DEFAULT_OPTIONS   the default option list: -check -no-autoload-plugins
                     Table 4.2: Predefined macros for ptests

4.4     Plug-in Migration from Makefile to Dune

Target readers: developers who have an existing plug-in for Frama-C 25 or less and want
to migrate this plug-in to Frama-C 26 or more.

Prerequisite: Being familiar with the plug-in to migrate. Depending on how complex the
plug-in is, it may require an advanced knowledge of the Dune build system.

Please note that this section is a best effort procedure for making the migration as smooth
as possible. If the plug-in is particularly complex, please contact us if you need some help
for migrating it.

4.4.1   Files organization changes

 Due to the way dune operates, it is preferable to work on the migration starting from a
 “clean” directory, without compilation and tests (in result directory of the test suites)
 artifacts. Otherwise, dune will complain about conflicts between files being both present
 in the original source directory and the target of a compilation rule.

Previously for a plug-in named Plugin, only the file Plugin.mli was necessary to expose
the signature of the plug-in. Now, one has to also provide an implementation file
On the other hand, it is not necessary that it begins with a capital letter anymore: you can
have and plugin.mli. If these files are not present, all functions included in the
modules constituting the plug-in will be exported.

                          CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

For most plug-ins, the autoconf and configure will be useless. In particular, Frama-C does
not provide any autoconf and configure features anymore. So for most plug-ins these files
will be entirely removed (see 4.4.3). Thus, the does not exist anymore. A
Makefile may be useful to provide some shortcuts (see Section 4.2).
If a plugin has a graphical user-interface, it is recommended to put the related files into a
separate directory in the directory of the plug-in (see 4.4.4).
It was previously possible to indicate . as a test suite for ptests. In such a case, tests source
files were directly in the tests directory. This is not possible anymore. If the plug-in tests
follow this architecture, these tests should be moved in a subdirectory of tests and the
oracles updated before starting the migration.

4.4.2    Template dune file

This basic template should be enough for most plug-ins. The next sections explain how to
add more information to this file to handle some common cases.
     ( rule
       ( alias frama-c-configure)
       (deps (universe))
       ( action ( progn
                  (echo "MyPlugin:" %{lib-available:frama-c-myplugin.core} "\n")
                  (echo " - Frama-C:" %{lib-available:frama-c.kernel} "\n")

     ( library
       ( optional )
       (name myplugin)
       (public_name frama-c-myplugin.core)
       ( flags -open Frama_c_kernel :standard)
       ( libraries frama-c.kernel)

     ( plugin
       ( optional )
       (name myplugin) (libraries frama-c-myplugin.core) (site (frama-c plugins))

For the creation of the dune-project file, please refer to Section 2.3.

4.4.3    autoconf and configure

Indicating whether a plug-in is available and why (availability of the dependencies) is now
handled via the frama-c-configure rule.
When working in the Frama-C src/plugins directory, enabling or disabling the plug-in at
build time is done thanks to the script dev/
Plug-ins dependencies are now declared in the dune file. In the libraries field. For instance,
if in the autoconf of the plug-in, the following lines are present:

                        4.4. PLUG-IN MIGRATION FROM MAKEFILE TO DUNE


The libraries should be now:
        ( libraries
            ( select from
              (%{lib- available:zarith } ->
              ( ->
            ( select from
              (%{lib- available:frama -c-eva.core} ->
              ( ->

For external binaries, the keyword is bin-available.
In the case some file must be generated at build time, it is recommended to use a rule together
with an action of generation. The executable itself can be generated from an OCaml file itself.
For example:
     ( executable
      (name myconfigurator)
      ( libraries str))

     ( rule
      (deps VERSION_FILE)
      ( targets generated- file )
      ( action (run ./myconfigurator.exe))

4.4.4    GUI migration

Just like there is a dune for the core features of the plug-in, there is now a dune file for the
GUI, that depends on the core features of the plug-in and the Frama-C GUI. This file is to put
in the gui subdirectory. Again, if there are additional dependencies, they must be indicated
in the libraries field:
     ( library
       (name myplugin_gui)
       (public_name frama-c-myplugin.gui)
       ( optional )
       ( flags -open Frama_c_kernel -open Frama_c_gui -open MyPlugin :standard)
       ( libraries frama-c.kernel frama-c.gui frama-c-myplugin.core)

     ( plugin ( optional )
        (name myplugin-gui)
        ( libraries frama-c-myplugin.gui)
        ( site (frama-c plugins_gui)))

                           CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

4.4.5      Build and

Provided that the dune files are ready. The plug-in can now be built using the command
dune build @install. The file can now be removed.

4.4.6      Installing Additional Files

If your plug-in has additional files to install besides the compiled files, themselves (typically,
files in share), you can use an install stanza in the dune file, as in:
       ( install
         (package frama-c-myplugin)
         ( section ( site (frama-c share)))
         ( files (share/myfile as frama-c-myplugin/myfile)))

With the stanza above, the installation of package frama-c-myplugin will copy myfile from
the share directory of the plug-in sources into the frama-c-myplugin directory inside the
share directory of Frama-C’s installation. Other target sections are available (e.g. bin for
installing an additional executable), see the dune manual7 for more information.

4.4.7      Migrating tests

In the test_config* files, the PLUGIN field is now mandatory and must list the plug-in and
all the plug-ins on which it directly depends on. For example the plug-in defined in our
previous dune file, and assuming that the tests use all mandatory and optional dependencies:
       PLUGIN: myplugin,wp,eva
       OPT: ...

The ptests_config file now lists the test suites. Notice that this file was previously generated
and probably list in the ignored files for the versioning system. Now, it must be versioned
in such a case. Assuming that the plug-in has three suites basic, eva and wp. This file now
       DEFAULT_SUITES=basic eva wp

For most plug-ins, these modifications should be enough so that:
       dune exec -- frama-c-ptests
       dune build @ptests

behaves in expected way.
For more advanced usage of ptests please refer to Section 4.3.

4.5       Plug-in General Services
Module Plugin provides an access to some general services available for all plug-ins. The
goal of this module is twofold. First, it helps developers to use general Frama-C services.
Second, it provides to the end-user a set of features common to all plug-ins. To access to
these services, you have to apply the functor Plugin.Register.

 Each plug-in must apply this functor exactly once.


                                     4.6. LOGGING SERVICES

Example 4.2 Here is how the plug-in From applies the functor Plugin.Register for its own
      include Plugin.Register
            let name = "from analysis"
            let shortname = "from"
            let help = "functional dependencies"

Applying this functor mainly provides two different services. First it gives access to functions
for printing messages in a Frama-C-compliant way (see Section 4.6). Second it allows to define
plug-in specific parameters available as options on the Frama-C command line to the end-user
(see Section 4.10).

4.6     Logging Services

Displaying results of plug-in computations to users, warning them of the hypothesis taken by
the static analyzers, reporting incorrect inputs, all these tasks are easy to think about, but
turn out to be difficult to handle in a readable way. As soon as your plug-in is registered (see
Section 4.5 above), though, you automatically benefit from many logging facilities provided
by the kernel. What is more, when logging through these services, messages from your plug-in
combine with other messages from other plug-ins, in a consistent and user-friendly way.
As a general rule, you should never write to standard output and error channels through
OCaml standard libraries.     For instance, you should never use Stdlib.stdout and
Stdlib.stderr channels, nor Format.printf-like routines.
Instead, you should use Format.fprintf to implement pretty-printers for your own complex
data, and only the printf-like routines of Log.Messages to display messages to the user.
All these routines are immediately available from your plug-in general services.

Example 4.3 A minimal example of a plug-in using the logging services:
      module Self = Plugin.Register
           let name = "foo plugin"
           let shortname = "foo"
           let help = "illustration of logging services"

      let pp_dg out n =
        Format.fprintf out
          "you have at least debug %d" n

      let run () =
         Self . result "Hello, this is Foo Logs !";
         Self .debug ∼level:0 "Try higher debug levels (%a)" pp_dg 0;
         Self .debug ∼level:1 "If you read this, %a." pp_dg 1;
         Self .debug ∼level:3 "If you read this, %a." pp_dg 3;

      let () = Db.Main.extend run ()

                         CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

Running this example, you should see:
     $ frama-c -foo-debug 2
     [foo] Hello, this is Foo Logs !
     [foo] Try higher debug levels (you have at least debug 0).
     [foo] If you read this, you have at least debug 1.

Notice that your plug-in automatically benefits from its own debug command line parameter,
and that messages are automatically prefixed with the name of the plug-in. We now get into
more details for an advanced usage of logging services.

4.6.1   From printf to Log

Below is a simple example of how to make a printf-based code towards being Log-compliant.
The original code, extracted from the Occurrence plug-in in Frama-C-Lithium version is as
     let print_one v l =
       Format.printf "variable %s (%d):@\n" v.vname v.vid;
       List . iter
         (fun (ki, lv) →
             Format.printf " sid %a: %a@\n" d_ki ki d_lval lv)

     let print_all () =
       compute ();
       Occurrences. iter print_one

The transformation is straightforward. First you add to all your pretty-printing functions an
additional Format.formatter parameter, and you call fprintf instead of printf:
     let print_one fmt v l =
       Format.fprintf fmt "variable %s (%d):@\n" v.vname v.vid;
       List . iter
         (fun (ki, lv) →
             Format.fprintf fmt " sid %a: %a@\n" d_ki ki d_lval lv)

Then, you delegate toplevel calls to printf towards an appropriate logging routine, with a
formatting string containing the necessary "%t" and "%a" formatters:
     let print_all () =
       compute ();
        result "%t" (fun fmt → Occurrences.iter (print_one fmt))

4.6.2   Log Quick Reference

The logging routines for your plug-ins consist in an implementation of the Log.Messages
interface, which is included in the Plugin.S interface returned by the registration of your
plug-in. The main routines of interest are:

result <options> "..."
     Outputs most of your messages with this routine. You may specify ~ level :n option to
     discard too detailed messages in conjunction with the verbose command line option.
     The default level is 1.

                                            4.6. LOGGING SERVICES

feedback <options> "..."
        Reserved for short messages that gives feedback about the progression of long compu-
        tations. Typically, entering a function body or iterating during fixpoint computation.
        The level option can be used as for result .

debug <options> "..."
        To be used for plug-in development messages and internal error diagnosis. You may
        specify ~ level :n option to discard too detailed messages in conjunction with the debug
        command line option. The default message level is 1, and the default debugging level
        is 0. Hence, without any option, debug discards all its messages.

warning <options> "..."
        For reporting to the user an important information about the validity of the analysis
        performed by your plug-in. For instance, if you locally assume non arithmetic overflow
        on a given statement, etc. Typical options include ~current:true to localize the message
        on the current source location.

 error <options> "..."
 abort <options> "..."
        Use these routines for reporting to the user an error in its inputs. It can be used for
        non valid parameters, for instance. It should not be used for some not-yet implemented
        feature, however.
        The abort routine is a variant that raises an exception and thus immediately aborts the
        computation8 . If you use error , execution will continue until the end of current stage
        or current group of the running phase (see section 4.11).

 failure <options> "..."
 fatal <options> "..."
        Use these routines for reporting to the user that your plug-in is now in inconsistent
        state or can not continue its computation. Typically, you have just discovered a bug in
        your plug-in!
        The fatal routine is a variant that raises an exception. failure has a behavior similar
        to error above, except that it denotes an internal error instead of a user error.

verify (condition) <options> "..."
        First the routine evaluates the condition and the formatting arguments, then, discards
        the message if the condition holds and displays a message otherwise. Finally, it returns
        the condition value.
        A typical usage is for example:
                    assert ( verify (x> 0) "Expected a positive value (%d)" x)

4.6.3       Logging Routine Options

Logging routines have optional parameters to modify their general behavior. Hence their
involved type in Log.mli.
      The raised exception is not supposed to be caught by anything else than the main entry point of Frama-C.

                         CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

Level Option. A minimal level of verbosity or debugging can be specified for the message
to be emitted. For the result and feedback channels, the verbosity level is used ; for the
debug channel, the debugging level is used.

     ~ level :$n$ minimal level required is n.

Category Option Debug, result, and feedback output can be associated to a debugging
key with the optional argument ~dkey which takes an argument of abstract type category .
Each category must be registered through the register_category function. You can define
subcategories by putting colons in the registered name. For instance a:b:c defines a subcat-
egory c of a:b, itself a subcategory of a. User can then choose to output debugging messages
belonging to a given category (and its subcategories) with the -plugin-msg-key <category>
In order to decide whether a message should be output, both level and category options are

  • if neither ~ level nor ~dkey, the effect is the same as having a level of 1 and no category.

  • if only ~ level is provided, the message is output if the corresponding verbosity or de-
    bugging level is sufficient

  • if only ~dkey is used, the message is output if the corresponding category is in used
    (even if the verbosity or debugging level is 0)

  • if both ~ level and ~dkey are present, the message is output if the two conditions above
    (sufficient verbosity or debugging level and appropriate category in use) hold. As a
    rule of thumb, you should refrain from using both mechanisms to control the output
    of a message. If some messages of a category do not have the same importance, use
    subcategories to give the user a finer control on what they want to see on the output.

Warning Category Option Warning output can also be associated with a category,
via the ~wkey optional argument that takes a value of abstract type warn_category.
Warning categories are distinct from plain categories, and must be registered with the
register_warn_category function. As explained in the user manual [3], each category can
be associated with a status that controls what will happen when a warning is triggered, from
completely ignoring it to aborting execution. The default is to emit the warning, but this
can be changed by using the set_warn_status function.

Source Options. By default, a message is not localized. You may specify a source location,
either specifically or by using the current location of an AST visitor.

     ~source:s use the source location s (see Log.mli)

     ~current:true use the current source location managed by Cil.CurrentLoc.

Emission Options. By default, a message is echoed to the user after its construction, and
it is sent to registered callbacks when emitted. See Section 4.6.4 below for more details on
how to globally modify such a behavior. During the message construction, you can locally
modify the emission process with the following options:

                                    4.6. LOGGING SERVICES

     ~emitwith:f suppresses the echo and sends the emitted event only to the callback
     function f . Listeners are not fired at all.

     ~once:true finally discards the message if the same one was already emitted before with
     the ~once option.

Append Option. All logging routines have the ~append:f optional parameter, where f
is function taking a Format.formatter as parameter and returning unit. This function f is
invoked to append some text to the logging routine. Such continuation-passing style is some-
time necessary for defining new polymorphic formatting functions. It has been introduced
for the same purpose than standard Format.kfprintf-like functions.

4.6.4   Advanced Logging Services

Message Emission
During message construction, the message content is echoed in the terminal. This echo may
be delayed until message completion when ~once has been used. Upon message completion,
the message is emitted and sent to all globally registered hook functions, unless the ~emitwith
option has been used.
To interact with this general procedure, the plug-in developer can use the following functions
defined in module Log:
     val set_echo:     ?plugin: string → ?kinds:kind list → bool → unit
     val add_listener: ?plugin: string → ?kinds:kind list → (event → unit) → unit

The logging routines take as argument a (polymorphic) formatting string, followed by the
formatting parameters, and finally return unit. It is also possible to catch the generated
message, and to pass it to a continuation that finally returns a value different than unit.
For this purpose, you must use the with_<log> routines variants. These routines take a
continuation f for additional parameter. After emitting the corresponding message in the
normal way, the message is passed to the continuation f . Hence, f has type event → α, and
the log routine returns α.
For instance, you typically use the following code fragment to return a degenerated value
while emitting a warning:
        let rec fact n =
           if (n> 12) then
             with_warning (fun _ → 0) "Overflow for %d, return 0 instead" x
           else if n≤ 1 then 1 else n * fact (n-1)

Generic Routines
The Log.Messages interface provides two generic routines that can be used instead of the
basic ones:

log ?kind ?verbose ?debug <options> "..."
     Emits a message with the given kind, when the verbosity and/or debugging level are

                           CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

logwith f ?wkey ?emitwith ?once <options> "..."
       Emits a message like warning, and finally pass the generated event (or None) to the
       continuation f , and returns its result.

The default kind is Result, but all the other kind of message can be specified. For verbosity
and debugging levels, the message is emitted when:
 log   "..."                  verbosity is at least 1
 log   ~verbose:n             verbosity is at least n
 log   ~debug:n               debugging is at least n
 log   ~verbose:v ~debug:d    either verbosity is at least v
                              or debugging is at least d.

Channel Management
The logging services are build upon channels, which are basically buffered formatters to
standard output extended with locking, delayed echo, and notification services.
The very safe feature of logging services is that recursive calls are protected. A message is
only echoed upon termination, and a channel buffer is stacked only if necessary to preserve
Services provided at plug-in registration are convenient shortcuts to low-level logging service
onto channels. The Log interface allows you to create such channels for your own purposes.
Basically, channels ensure that no message emission interfere with each others during echo on
standard output. Hence the forbidden direct access to Stdlib.stdout. However, Log interface
allows you to create such channels on your own, in addition to the one automatically created
for your plug-in.

new_channel name
       This creates a new channel. There is only one channel per name, and the function
       returns the existing one if any. Plug-in channels are registered under their short-name,
       and the kernel channel is registered under Log.kernel_channel_name.

log_channel channel ?kind ?prefix
     This routine is similar to the log one.

With both logging routines, you may specify a prefix to be used during echo. The available
switches are:

       Label t: use the string t as a prefix for the first echoed line of text, then use an
       indentation of same length for the next lines.

       Prefix t: use the string t as a prefix for all lines of text.

       Indent n: use an indentation of n spaces for all lines of text.

When left unspecified, the prefix is computed from the message kind and the channel name,
like for plug-ins.


Output Management
It is possible to ask Log to redirect its output to another channel:

set_output out flush
      The parameters are the same than those of Format.make_formatter: out outputs a
      (sub)-string and flush actually writes the buffered text to the underlying device.

It is also possible to have a momentary direct access to Stdlib.stdout, or whatever its
redirection is:

print_on_output "..."
      The routine immediately locks the output of Log and prints the provided message. All
      message echoes are delayed until the routine actually returns. Notification to listeners
      is not delayed, however.
print_delayed "..."
      This variant locks the output only when the first character would be written to output.
      This gives a chance to a message to be echoed before your text is actually written.

Remark that these two routines can not be recursively invoked, since they have a lock to a non-
delayed output channel. This constraint is verified at runtime to avoid incorrect interleaving,
and you would get a fatal error if the situation occurs.

Warning: these routine are dedicated to expensive output only. You get the advantage of
not buffering your text before printing. But on the other hand, if you have messages to be
echoed during printing, they must be stacked until the end of your printing.
You get a similar functionality with Kernel\_function.CodeOutput.output. This routine
prints your text by calling Log.print_delayed, unless the command line option -ocode has
been set. It this case, your text is written to the specified file.

4.7     The Datatype library: Type Values and Datatypes

Type values and datatypes are key notions of Frama-C. They are both provided by the
Datatype library. An overview as well as technical details may also be found in a related
article in French [18]. A short summary focusing on (un)marshaling is described in another ar-
ticle [6]. First, Section 4.7.1 introduces type values. Then Section 4.7.2 introduces datatypes
built on top of type values.

4.7.1   Type Value

A type value is an OCaml value which dynamically represents a static monomorphic OCaml
type τ . It gets the type τ Type.t. There is at most one type value which represents the type
τ . Type values are used by Frama-C to ensure safety when dynamic typing is required (for
instance to access to a dynamic plug-in API, see Section 4.8.3).
Type values for standard OCaml monomorphic types are provided in module Datatype.

Example 4.4 The type value for type int is while the one for type string
is Datatype.string. The former has type int Type.t while the latter has type string

                          CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

Type values are created when building datatypes (see Section 4.7.2). There is no type value
for polymorphic types. Instead, they have to be created for each instance of a polymorphic
type. Functions for accessing such type values for standard OCaml polymorphic types are
provided in moduleDatatype.

Example 4.5 The type value for type int list is Datatype.list while the
one for type string →char →bool is Datatype.func2 Datatype.string Datatype.char
Datatype.bool. The former has type int list Type.t while the latter has type (string
→char →bool) Type.t.

4.7.2   Datatype

A datatype provides in a single module a monomorphic type and usual values over it. Its
signature is Datatype.S. It contains the type itself, the type value corresponding to this
type, its name, functions equal, compare, hash and pretty which may respectively be used
to check equality, to compare, to hash and to pretty print values of this type. It also contains
some other values (for instance required when marshaling). Whenever possible, a datatype
implements an extensible version of Datatype.S, namely Datatype.S_with_collections.
For a type τ , this extended signature additionally provides modules Set, Map and Hashtbl
respectively implementing sets over τ , maps and hashtables indexed by elements of τ .
Datatypes for OCaml types from the standard library are provided in module Datatype, while
those for AST’s types are provided in module Cil_datatype. Furthermore, when a kernel
module implements a datastructure, it usually implements Datatype.S.

Example 4.6 The following line of code pretty prints whether two statements are equal.
     (∗ assuming the type of [stmt1] and [stmt2] is Cil_types.stmt ∗)
       fmt (∗ a formatter previously defined somewhere ∗)
       "statements %a and %a are %sequal"
       Cil_datatype.Stmt.pretty stmt1
       Cil_datatype.Stmt.pretty stmt2
       ( if Cil_datatype.Stmt.equal stmt1 stmt2 then "" else "not ")

Example 4.7 Module Datatype.String implements Datatype.S_with_collections.
Thus you can initialize a set of strings in the following way.
      let string_set =
        List . fold_left
          (fun acc s → Datatype.String.Set.add s acc)
          [ "foo"; "bar"; "baz" ]

Building Datatypes
For each monomorphic type, the corresponding datatype may be created by applying the
functor Datatype.Make. In addition to the type t corresponding to the datatype, several
values must be provided in the argument of the functor. These values are properly docu-
mented in the Frama-C API. The following example introduces them in a practical way.

Example 4.8 Here is how to define in the more precise way the datatype corresponding to
a simple sum type.


     type ab = A | B of int
     module AB =
            (∗ the type corresponding to the datatype ∗)
            type t = ab
            (∗ the unique name of the built datatype; usually the name of the
                type ∗)
             let name = "ab"
            (∗ representants of the type: a non−empty list of values of this type. It
                is only used for safety check: the best the list represents the
                different possible physical representation of the type, the best the
                check is. ∗)
             let reprs = [ A; B 0 ]
            (∗ structural descriptor describing the physical representation of the
                type. It is used when marshaling. ∗)
             let structural_descr =
                 (Structural_desr.Sum [| [| Structural_descr.p_int |] |])
            (∗ equality, compare and hash are the standard OCaml ones ∗)
             let equal (x:t) y = x = y
             let compare (x:t) y = x y
             let hash (x:t) = Hashtbl.hash x
            (∗ the type ab is a standard functional type, thus copying and rehashing
                are simply identity. Rehashing is used when marshaling. ∗)
             let copy = Datatype.identity
             let rehash = Datatype.identity
            (∗ the type ab does never contain any value of type Project.t ∗)
             let mem_project = Datatype.never_any_project
            (∗ pretty printer ∗)
             let pretty fmt x =
               Format.pp_print_string fmt
                (match x with A → "a" | B n → "b" ^ string_of_int n)

Only providing an effective implementation for the values name and reprs is mandatory.
For instance, if you know that you never use values of type t as keys of hashtable, you can
define the function hash equal to the function Datatype.undefined , and so on. To ease this
process, you can also use the predefined structure Datatype.Undefined.

Example 4.9 Here is a datatype where only the function equal is provided.
     (∗ the same type than the one of the previous example ∗)
     type ab = A | B of int
     module AB =
            type t = ab
             let name = "ab"
             let reprs = [ A; B 0 ]
             include Datatype.Undefined
             let equal (x:t) y = x = y

One weakness of Datatype.Undefined is that it cannot be used in a projectified state
(see Section 4.9.2) because its values cannot be serializable. In such a case, you can use

                              CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

the very useful predefined structure Datatype.Serializable_undefined which behaves as
Datatype.Undefined but defines the values which are relevant for (un)serialization.

Datatypes of Polymorphic Types
As for type values, it is not possible to create a datatype corresponding to polymorphic types,
but it is possible to create them for each of their monomorphic instances.

 For building such instances, you must not apply the functor Datatype.Make since it will
 create two type values for the same type (and with the same name): that is forbidden.

Instead, you must use the functor Datatype.Polymorphic for types with one type parameter
and the functor Datatype.Polymorphic2 for types with two type parameters9 . These func-
tors takes as argument how to build the datatype corresponding each monomorphic instance.

Example 4.10 Here is how to apply Datatype.Polymorphic corresponding to the type ’a
t below.
        type α ab = A of α | B of int
        module Poly_ab =
               type α t = α ab
                let name ty = ty ^ " ab"
                let module_name = "Ab"
                let reprs ty = [ A ty ]
                let structural_descr d =
                     [| [| Structural_descr.pack d |]; [| Structural_descr.p_int |] |]
                let mk_equal f x y = match x, y with
                  | A x, A y → f x y
                  | B x, B y → x = y
                  | A _, B _ | B _, A _ → false
                let mk_compare f x y = match x, y with
                  | A x, A y → f x y
                  | B x, B y → x y
                  | A _, B _ → 1
                  | B _, A _ → -1
              let mk_hash f = function A x → f x | B x → 257 * x
              let map f = function A x → A (f x) | B x → B x
              let mk_internal_pretty_code f prec_caller fmt = function
                 | A x →
                     (fun fmt → Format.fprintf fmt "A %a" (f Type.Call) x)
                 | B n →
                     (fun fmt → Format.fprintf fmt "B %d" n)
      Polymorphic3 and Polymorphic4 also exist in case of polymorphic types with 3 or 4 type parameters.

                             4.8. PLUG-IN REGISTRATION AND ACCESS

           let mk_pretty f fmt x =
             mk_internal_pretty_code (fun _ → f) Type.Basic fmt x
           let mk_varname _ = "ab"
           let mk_mem_project mem f = function
             | A x → mem f x
             | B _ → false
      module Ab = Poly_AB.Make

      (∗ datatype corresponding to the type [int ab] ∗)
      module Ab_int = Ab(Datatype.Int)

      (∗ datatype corresponding to the type [int list ab] ∗)
      module Ab_Ab_string = Ab(Datatype.List(Datatype.Int))

      (∗ datatype corresponding to the type [(string, int) Hashtbl.t ab] ∗)
      module HAb = Ab(Datatype.String.Hashtbl.Make(Datatype.Int))

Clearly it is a bit painful. However you probably will never apply this functor yourself. It is
already applied for the standard OCaml polymorphic types like list and function (respectively
Datatype.List and Datatype.Function).

4.8     Plug-in Registration and Access

In this section, we present how to register plug-ins and how to access them. Actually, there
are three different ways, but the recommended one is through a .mli file.
Section 4.8.1 indicates how to register and access a plug-in through a .mli file. Section 4.8.2
indicates how to register and access a kernel-integrated plug-in while Section 4.8.3 details
how to register and access a standard plug-in.

4.8.1    Registration through a .mli File

Target readers: plug-in developers.

Prerequisite: Basic knowledge of dune.

From dune point of view, a plug-in is simply an OCaml library. In order for plugin B to use
a function which is declared in the interface of plugin A, the dune file of B must contain in
its libraries clause frama-c-a.core (see Section 4.1), or more generally the public_name
under which A is declared.

4.8.2    Kernel-integrated Registration and Access

Target readers: kernel-integrated plug-in developers.

Prerequisite: Accepting to modify the Frama-C kernel. Otherwise, you can still register
your plug-in as any standard plug-in (see Section 4.8.3 for details).

                             CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

 This registration method is deprecated and only kept here for historical purpose. No
 new entry point should be added in the Db, which will be removed in a future version of
A database, called Db (in directory src/kernel_services/plugin_entry_points), groups
together the API of all kernel-integrated plug-ins. So it permits easy plug-in collaborations.
Each kernel-integrated plug-in is only visible through Db. For example, if a plug-in A wants to
know the results of another plug-in B, it uses the part of Db corresponding to B. A consequence
of this design is that each plug-in has to register in Db by setting a function pointer to the
right value in order to be usable from others plug-ins.

Example 4.11 Plug-in Impact registers function compute_pragmas in the following way.

 File src/plugins/impact/

       let compute_pragmas () = ...
       let () = Db.Impact.compute_pragmas ← compute_pragmas

Thus each developer who wants to use this function calls it by pointer dereferencing like this.
       let () = !Db.Impact.compute_pragmas ()

If a kernel-integrated plug-in has to export some datatypes usable by other plug-ins, such
datatypes have to be visible from module Db. Thus they cannot be declared in the plug-in
implementation itself like any other plug-in declaration because postponed type declarations
are not possible in OCaml.
Such datatypes are called plug-in types. The solution is to put these plug-ins types in some
files linked before Db; hence you have to put them in another directory than the plug-in
directory. The best way is to create a directory dedicated to types.

Recommendation 4.1 The suggested name for this directory is p_types for a plug-in p.

Example 4.12 Suppose you are writing a plug-in p which exports a specific type t corre-
sponding to the result of the plug-in analysis. The standard way to proceed is the following.
 File src/plugins/p_types/p_types.mli

       type t = ...

 File src/kernel_services/plugin_entry_points/db.mli

       module P : sig
         val run_and_get: (unit → P_types.t) ref
            (∗∗ Run plugin analysis (if it was never launched before).
                @return result of the analysis. ∗)

This design choice has a side effect : it reveals exported types. You can always hide them
using a module to encapsulate the types (and provide corresponding getters and setters to
access them).
At this point, part of the plug-in code is outside the plug-in implementation. This code
should be linked before Db 10 .
     A direct consequence is that you cannot use the whole Frama-C functionalities, such as module Db, inside
this code.

                             4.8. PLUG-IN REGISTRATION AND ACCESS

4.8.3   Dynamic Registration and Access

Target readers: standard plug-ins developers.

 Dynamic registration is obsolete. Newer development should favor exporting a static API,
 as explained in Section 4.8.1.

Registration of kernel-integrated plug-ins requires to modify module Db which belongs to
the Frama-C kernel. Such a modification is not possible for standard plug-ins which are
fully independent of Frama-C. Consequently, the Frama-C kernel provides another way for
registering a plug-in through the module Dynamic.
In short, you have to use the function Dynamic.register in order to register a value from
a dynamic plug-in and you have to use function Dynamic.get in order to apply a function
previously registered with Dynamic.register.

Registering a value
The signature of Dynamic.register is as follows.
     val register : plugin: string → string → α Type.t → α →

The first argument is the name of the plug-in registering the value and the second one is a
binding name of the registered OCaml value. The pair (plug-in name, binding name) must
not be used for value registration anywhere else in Frama-C. It is required in order for another
plug-in to access to this value (see next paragraph). The third argument is the type value
of the registered value (see Section 4.7.1). It is required for safety reasons when accessing to
the registered value (see the next paragraph). The fourth argument is the value to register.

Example 4.13 Here is how the function run of the plug-in hello of the tutorial is registered.
The type of this function is unit → unit.
      let run () : unit = ...
      let () =
          (Datatype.func Datatype.unit Datatype.unit)

If the string "" is already used to register a dynamic value, then the exception
Type.AlreadyExists is raised during plug-in initialization (see Section 4.11).
The function call Datatype.func Datatype.unit Datatype.unit returns the type value
representing unit → unit. Note that, because of the type of Dynamic.register and the
types of its arguments, the OCaml type checker complains if the third argument (here the
value run) has not the type unit → unit.

Accessing to a registered value
The signature of function Dynamic.get is as follows.
     val get: plugin: string → string → α Type.t → α

                         CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

The arguments must be the same than the ones used at value registration time (with
Dynamic.register). Otherwise, depending on the case, you will get a compile-time or a
runtime error.

Example 4.14 Here is how the previously registered function run of Hello may be applied.
     let () =
         (Datatype.func Datatype.unit Datatype.unit)

The given strings and the given type value must be the same than the ones used when reg-
istering the function. Otherwise, an error occurs at runtime. Furthermore, the OCaml type
checker will complain either if the third argument (here ()) is not of type unit or if the
returned value (here () also) is not of type unit.

The above-mentioned mechanism requires access to the type value corresponding to the type
of the registered value. Thus it is not possible to access a value of a plug-in-defined type.
For solving this issue, Frama-C provides a way to access type values of plug-in-defined types
in an abstract way through the functor Type.Abstract.

Example 4.15 There is no current example in the Frama-C open-source part, but consider
a plug-in which provides a dynamic API for callstacks as follows.
     module P =
          let name = "Callstack"
          let shortname = "Callstack"
          let help = "callstack library"

     (∗ A callstack is a list of a pair (kf ∗ stmt) where [kf] is the kernel
        function called at statement [stmt]. Building the datatype also creates the
        corresponding type value [ty]. ∗)
     type callstack = (Kernel_function.t * Cil_datatype.Stmt.t) list

     (∗ Implementation ∗)
     let empty = []
     let push kf stmt stack = (kf, stmt) :: stack
     let pop = function [] → [] | _ :: stack → stack
     let rec print = function
       | [] → ""
       | (kf, stmt) :: stack → "function %a called at stmt %a"
           Kernel_function.pretty kf
           Cil_datatype.Stmt.pretty stmt;
         print stack

     (∗ Type values ∗)
     let kf_ty = Kernel_function.ty
     let stmt_ty = Cil_datatype.Stmt.ty

                               4.9. PROJECT MANAGEMENT SYSTEM

      module D =
           type t = callstack
           let name = "Callstack.t"
           let reprs = [ empty; [ Kernel_function.dummy (), Cil.dummyStmt ] ]
           include Datatype.Serializable_undefined

      (∗ Dynamic API registration ∗)
      let register name ty =
        Dynamic.register ∼plugin:"Callstack" name ty

      let   empty = register "empty" D.ty empty
      let   push = register "push" (Datatype.func3 kf_ty stmt_ty D.ty D.ty) push
      let   pop = register "pop" (Datatype.func D.ty D.ty) pop
      let   print = register "print" (Datatype.func D.ty Datatype.unit) print

You have to use the functor Type.Abstract to access to the type value corresponding to the
type of callstacks (and thus to access to the above dynamically registered functions).
      (∗ Type values ∗)
      let kf_ty = Kernel_function.ty
      let stmt_ty = Cil_datatype.Stmt.ty

      (∗ Access to the type value for abstract callstacks ∗)
      module C = Type.Abstract(struct let name = "Callstack.t" end)

      let get name ty = Dynamic.get   ∼plugin:"Callstack"   name ty

      (∗ mutable callstack ∗)
      let callstack_ref = ref (get "empty" C.ty)

      (∗ operations over this mutable callstack ∗)

      let push_callstack =
        (∗ getting the function outside the closure is more efficient ∗)
         let push = get "push" (Datatype.func3 kf_ty stmt_ty C.ty C.ty) in
        fun kf stmt → callstack_ref ← push kf stmt !callstack_ref

      let pop_callstack =
        (∗ getting the function outside the closure is more efficient ∗)
         let pop = get "pop" (Datatype.func C.ty C.ty) in
        fun () → callstack_ref ← pop !callstack_ref

      let print_callstack =
        (∗ getting the function outside the closure is more efficient ∗)
         let print = get "print" (Datatype.func C.ty Datatype.unit) in
        fun () → print !callstack_ref

      (∗ ... algorithm using the callstack ... ∗)

4.9     Project Management System

Prerequisite: Knowledge of the OCaml module system and labels.

                          CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

In Frama-C, a key notion detailed in this section is the one of project. An overview as well
as technical details may also be found in a related article in French [17]. Section 4.9.1 first
introduces the general principle of project. Section 4.9.2 introduces the notion of states. State
registration is detailed in Sections 4.9.3 and 4.9.4. The former is dedicated to standard (high-
level) registration, while the latter is dedicated to low-level registration. Then Section 4.9.5
explains how to use projects. Finally Section 4.9.6 details state selections.

4.9.1    Overview and Key Notions

A project groups together an AST with the set of global values attached to it. Such values
are called states. Examples of states are parameters (see Section 4.10) and results of analyses
(Frama-C extensively uses memoization [14, 15] in order to prevent running analyses twice).
In a Frama-C session, several projects (and thus several ASTs) can exist at the same time.
The project library ensures project non-interference: modifying the value of a state in a
project does not impact any value of any state in any other project. To ensure this property,
each state must be registered in the project library as explained in Sections 4.9.3 and 4.9.4.
Relations between states and projects are summarized in Figure 4.1.

                                          Project p1       ...      Project pn
                     AST a             value of a in p1    ...    value of a in pn
                    data d1           value of d1 in p1    ...   value of d1 in pn
                      ...                    ...           ...          ...
                    data dm           value of dm in p1    ...   value of dm in pn

                      Figure 4.1: Representation of the Frama-C State.

To ease development, Frama-C maintains a current project (Project.current ()): all op-
erations are automatically performed on it. For instance, calling Ast.get () returns the
Frama-C AST of the current project. It is also possible to access values in others projects as
explained in Section 4.9.5.

4.9.2    State: Principle

 If some data should be part of the state of Frama-C, you must register it in the project
 library (see Sections 4.9.3 and 4.9.4).

Here we first explain what are the functionalities of each state and then we present the general
principle of registration.

State Functionalities
Whenever you want to attach some data (e.g. a table containing results of an analysis) to an
AST, you have to register it as an internal state. The main functionalities provided to each
internal state are the following.

  • It is automatically updated whenever the current project changes. Your data are thus
    always consistent with the current project. More precisely, you still work with your

                                 4.9. PROJECT MANAGEMENT SYSTEM

      global data (for instance, a hashtable or a reference) as usual in OCaml. The project
      library silently changes the data when required (usually when the current project is
      changing). The extra cost due to the project system is usually an extra indirection.
      Figure 4.2 summarizes these interactions between the project library and your state.

                                          State 1

              Project 1         ...                                       Client 1 =
                                                    answer 1              local version of state 1
                                          State n
project                   ...                                           ...

                                          State 1   answer n             Client n =
                                                                         local version of state n
             Project p          ...

                                          State n

               Server = Project Library

    Figure 4.2: Interaction between the project library and your registered global data.

  • It is part of the information saved on disk for restoration in a later session.

  • It may be part of a selection which is a consistent set of states. With such a selection,
    you can control on which states project operations are consistently applied (see Sec-
    tion 4.9.6). For example, it is possible to clear all the states which depend on Value
    Analysis results.

  • It is possible to ensure inter-analysis consistency by setting state dependencies.
    For example, if the entry point of the analyzed program is changed (using
    Globals.set_entry_point), all the results of analyses depending on it (like value anal-
    ysis’ results) are automatically reset. If such a reset were not performed, the results
    of the value analysis would not be consistent anymore with the current entry point,
    leading to incorrect results.

      Example 4.16
  "%B" (Eva.Analysis.is_computed ()); (∗ true ∗)
           Globals.set_entry_point "f" true;
  "%B" (Eva.Analysis.is_computed ()); (∗ false ∗)

      As the value analysis has been automatically reset when setting the entry point, the
      above code outputs
           [kernel] true
           [kernel] false

                            CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

State Registration: Overview
For registering a new state, functor State_builder.Register is provided. Its use is de-
scribed in Section 4.9.4 but it is a low-level functor which is usually difficult to apply in a
correct way. Higher-level functors are provided to the developer in modules State_builder
and Cil_state_builder that allow the developer to register states in a simpler way. They
internally apply the low-level functor in the proper way. Module State_builder provides
state builders for standard OCaml datastructures like hashtables whereas Cil_state_builder
does the same for standard Cil datastructures (like hashtables indexed by AST statements)11 .
They are described in Section 4.9.3.

 Registering a new state must be performed when the plugin is initialized. Thus, using
 OCaml let module construct to register the new state is forbidden (except if you really
 know what you are doing).

4.9.3    Registering a New State

Here we explain how to register and use a state. Registration through the use of the low-level
functor State_builder.Register is postponed in Section 4.9.4 because it is more tricky and
rarely useful.
In most non-Frama-C applications, a state is a global mutable value. One can use it to store
results of analyses. For example, using this mechanism inside Frama-C to create a state
which would memoize some information attached to statements would result in the following
piece of code.
       open Cil_datatype
       type info = Kernel_function.t * Cil_types.varinfo
       let state : info Stmt.Hashtbl.t = Stmt.Hashtbl.create 97
       let compute_info (kf,vi) = ...
       let memoize s =
          try Stmt.Hashtbl.find state s
         with Not_found → Stmt.Hashtbl.add state s (compute_info s)
       let run () = ... Eva.Analysis.compute (); ... memoize some_stmt ...

However, if one puts this code inside Frama-C, it does not work because this state is not
registered as a Frama-C state. For instance, it is never saved on the disk and its value is
never changed when setting the current project to a new one. For this purpose, one has to
transform the above code into the following one.
       module State =
             let size = 97
             let name = "state"
             let dependencies = [ Eva.Analysis.self ]
       let compute_info (kf,vi) = ...
       let memoize = State.memo compute_info
       let run () = ... Eva.Analysis.compute (); ... memoize some_stmt ...
    These datastructures are only mutable datastructures (like hashtables, arrays and references) because
global states are always mutable.

                                4.9. PROJECT MANAGEMENT SYSTEM

A quick look on this code shows that the declaration of the state itself is more complicated
(it uses a functor application) but its use is simpler. Actually what has changed?

  1. To declare a new internal state, apply one of the predefined functors in modules
     State_builder or Cil_state_builder (see interfaces of these modules for the list
     of available modules). Here we use Cil_state_builder.Stmt_hashtbl which provides
     a hashtable indexed by statements. The type of values associated to statements is a pair
     of Kernel_function.t and Cil_types.varinfo. The first argument of the functor is
     then the datatype corresponding to this type (see Section 4.7.2). The second argument
     provides some additional information: the initial size of the hashtable (an integer sim-
     ilar to the argument of Hashtbl.create), an unique name for the resulting state and
     its dependencies. This list of dependencies is built upon values self which are called
     state kind (or simply kind) and are part of any state’s module (part of the signature of
     the low-level functor State_builder.Register). This value represents the state itself
     as first-class value (like type values for OCaml types, see Section 4.7.1).

  2. From outside, a state actually hides its internal representation in order to ensure some
     invariants: operations on states implementing hashtables do not take hashtables as
     arguments because they implicitly use the hidden hashtable. In our example, a prede-
     fined memo function is used in order to memoize the computation of compute_info.
     This memoization function implicitly operates on the hashtable hidden in the internal
     representation of State.

Postponed dependencies Sometimes, you want to access a state kind before defining it.
That is usually the case when you have two mutually-dependent states: the dependencies of
the first one provided when registering it must contain the state kind of the second one which
is created by registering it. But this second registration also requires a list of dependencies
containing the first state kind.
For solving this issue, it is possible to postpone the addition of a state kind to dependencies
until all modules have been initialized. However, dependencies must be correct before any-
thing serious is computed by Frama-C. So the right way to do this is the use of the function
Cmdline.run_after_extended_stage (see Section 4.11 for advanced explanation about the
way Frama-C is initialized).

Example 4.17 Plug-in from puts a reference to its state kind in the following way. This
reference is initialized at module initialization time.

 File src/kernel_services/plugin_entry_points/db.mli

     module From = struct
       val self : State.t ref

 File src/kernel_services/plugin_entry_points/

     module From = struct
       val self = ref State.dummy (∗ postponed ∗)

                            CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

 File src/plugins/from/

     module Tbl =
             let name = "functionwise_from"
             let size = 97
             let dependencies = [ Eva.Analysis.self ]
     let () =
       (∗ performed at module initialization runtime. ∗)
       Db.From.self ← Tbl.self

Plug-in pdg uses from for computing its own internal state. So it declares this dependency
as follows.

 File src/plugins/pdg/

     module Tbl =
             let name = "Pdg.State"
             let dependencies = [] (∗ postponed because !Db.From.self may
                                     not exist yet ∗)
             let size = 97
     let () =
         (fun () →
               [ !Db.From.self ])

Dependencies over the AST Most internal states depend directly or indirectly on the
AST of the current project. However, the AST plays a special role as a state. Namely, it
can be changed in place, bypassing the project mechanism. In particular, it is possible to
add globals. Plugins that perform such changes should inform the kernel when they are done
using Ast.mark_as_changed or Ast.mark_as_grown. The latter must be used when the only
changes are additions, leaving existing nodes untouched, while the former must be used for
more intrusive changes. In addition, it is possible to tell the kernel that a state is “monotonic”
with respect to AST changes, in the sense that it does not need to be cleared when nodes
are added (the information that should be associated to the new nodes will be computed as
needed). This is done with the function Ast.add_monotonic_state. Ast.mark_as_grown
will not touch such a state, while Ast.mark_as_changed will clear it.

4.9.4    Direct Use of Low-level Functor State_builder.Register

Functor State_builder.Register is the only functor which really registers a state. All the
others internally use it. In some cases (e.g. if you define your own mutable record used as a
state), you have to use it. Actually, in the Frama-C kernel, there are only three direct uses of
this functor over thousands of state registrations: so you will certainly never use it.

                                   4.9. PROJECT MANAGEMENT SYSTEM

This functor takes three arguments. The first and the third ones respectively correspond to
the datatype and to information (name and dependencies) of the states: they are similar to
the corresponding arguments of the high-level functors (see Section 4.9.3).
The second argument explains how to handle the local version of the state under registration.
Indeed here is the key point: from the outside, only this local version is used for efficiency
purposes (remember Figure 4.2). It would work even if projects do not exist. Each project
knows a global version. The project management system automatically switches the local
version when the current project changes in order to conserve a physical equality between local
version and current global version. So, for this purpose, the second argument provides a type
t (type of values of the state) and five functions create (creation of a new fresh state), clear
(cleaning a state), get (getting a state), set (setting a state) and clear_some_projects (how
to clear each value of type project in the state if any).

  The following invariants must hold:12

                                    create () returns a fresh value                                    (4.1)
                     ∀p of type t, create () = (clear p; set p; get ())                                (4.2)
                              ∀p of type t, copy p returns a fresh value                               (4.3)
                ∀p1, p2 of type t such that p1 != p2, (set p1; get ()) != p2                           (4.4)

Invariant 4.1 ensures that there is no sharing with any value of a same state: so each new
project has got its own fresh state. Invariant 4.2 ensures that cleaning a state resets it to its
initial value. Invariant 4.3 ensures that there is no sharing with any copy. Invariant 4.4 is a
local independence criterion which ensures that modifying a local version does not affect any
other version (different from the global current one) by side effects.

Example 4.18 To illustrate this, we show how functor State_builder.Ref (registering a
state corresponding to a reference) is implemented.
       module Ref
         (Data: Datatype.S)
         (Info: sig include Info val default : unit → Data.t end) =
         type data = Data.t
          let create () = ref Info. default
          let state = ref (create ())

Here we use an additional reference: our local version is a reference on the right value. We
can use it in order to safely and easily implement get and set required by the registration.
         include Register
              type t = data ref (∗ we register a reference on the given type ∗)
              let create = create
              let clear tbl = tbl ← Info.default
              let get () = !state
              let set x = state ← x
              let clear_some_projects f x =
                 if Data.mem_project f !x then begin clear x; true end else false
    As usual in OCaml, = stands for structural equality while == (resp. !=) stands for physical equality (resp.

                              CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT


For users of this module, we export “standard” operations which hide the local indirection
required by the project management system.
          let set v = !state ← v
          let get () = !(!state)
          let clear () = !state ← Info.default

As you can see, the above implementation is error prone; in particular it uses a double indirec-
tion (reference of reference). So be happy that higher-level functors like State_builder.Ref
are provided which hide such implementations from you.

4.9.5      Using Projects

As said before, all operations are done by default on the current project. But sometimes plug-
in developers have to explicitly use another project, for example when the AST is modified
(usually through the use of a copy visitor, see Section 4.15) or replaced (e.g. if a new one is
loaded from disk).

 An AST must never be modified inside a project. If such an operation is re-
 quired, you must either create a new project with a new AST, usually by using
 File.init_project_from_cil_file or File.init_project_from_visitor; or write
 the following line of code (see Section 4.9.6):

      let selection = State_selection.only_dependencies Ast.self in
      Project.clear ~selection ()

Operations over projects are grouped together in module Project. A project has type
Project.t. Function Project.set_current sets the current project on which all opera-
tions are implicitly performed.

Example 4.19 Suppose that you saved the current project into file foo.sav in a previous
Frama-C session13 thanks to the following instruction. "foo.sav"

In a new Frama-C session, executing the following lines of code (assuming the value analysis
has never been computed previously)
        let print_computed () =
  "%B" (Eva.Analysis.is_computed ())
        print_computed (); (∗ false ∗)
        let old = Project.current () in
           let foo = Project.load ∼name:"foo" "foo.sav" in
           Project.set_current foo;
           Eva.Analysis.compute ();
           print_computed (); (∗ true ∗)
      A session is one execution of Frama-C (through frama-c or frama-c-gui).

                               4.9. PROJECT MANAGEMENT SYSTEM

       Project.set_current old;
       print_computed () (∗ false ∗)
     with Project.IOError _ →
       Kernel.abort "error while loading"

     [kernel] false
     [kernel] true
     [kernel] false

This example shows that the value analysis has been computed only in project foo and not in
project old.

 An important invariant of Frama-C is: if p is the current project before running an analysis,
 then p will be the current project after running it. It is the responsibility of any plug-in
 developer to enforce this invariant for his/her own analysis.

To be sure to enforce the above-mentioned invariant, the project library provides an alter-
native to the use of Project.set_current: Project.on applies an operation on a given
project without changing the current project (i.e. locally switch the current project in order
to apply the given operation and, afterwards, restore the initial context).

Example 4.20 The following code is equivalent to the one given in Example 4.19.
     let print_computed () = "%B" (Eva.Analysis.is_computed ())
     print_computed (); (∗ false ∗)
        let foo = Project.load ∼name:"foo" "foo.sav" in
        Project.on foo
          (fun () → Eva.Analysis.compute (); print_computed () (∗ true ∗)) ();
        print_computed () (∗ false ∗)
     with Project.IOError _ →
        exit 1

It displays

4.9.6      Selections

Most operations working on a single project (e.g. Project.clear or Project.on) have
an optional parameter selection of type State_selection.t. This parameter allows the
developer to specify on which states the operation applies. A selection is a set of states which
allows the developer to consistently handle state dependencies.

Example 4.21 The following statement clears all the results of the value analysis and all
its dependencies in the current project.
     let selection = State_selection.with_dependencies Eva.Analysis.self in
     Project. clear ∼ selection ()

                          CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

The selection explicitly indicates that we also want to clear all the states which depend on the
value analysis’ results.

 Use selections carefully: if you apply a function f on a selection s and f handles a state
 which does not belong to s, then the computed result by Frama-C is potentially incorrect.

Example 4.22 The following statement applies a function f in the project p (which is not
the current one). For efficiency purposes, we restrict the considered states to the command
line options (see Section 4.10).
     Project.on   ∼ selection:(Parameter_state.get_selection   ()) p f ()

This statement only works if f only handles values of the command line options. If it tries
to get the value of another state, the result is unspecified and all actions using any state of
the current project and of project p also become unspecified.

4.10     Command Line Options

Prerequisite: Knowledge of the OCaml module system.

Values associated with command line options are called parameters. The parameters of the
Frama-C kernel are stored in module Kernel while the plug-in specific ones have to be defined
in the plug-in source code.

4.10.1    Definition

In Frama-C, a parameter is represented by a value of type Typed_parameter.t and by a
module implementing the signature Parameter_sig.S. The first representation is a low-level
one required by emitters (see Section 4.16) and the GUI. The second one provides a high-
level API: each parameter is indeed a state (see Section 4.9.2). Several signatures extending
Parameter_sig.S are provided in order to deal with the usual parameter types. For example,
there are signatures Parameter_sig.Int and Parameter_sig.Bool for integer and boolean
parameters. Mostly, these signatures provide getters and setters for modifying parameter
Implementing such an interface is very easy thanks to a set of functors provided by the output
module of Plugin.Register. Indeed, you have just to choose the right functor according to
your option type and potentially the wished default value. Below are some examples of such
functors (see the signature Parameter_sig.Builder for an exhaustive list).

  1. False (resp. True) builds a boolean option initialized to false (resp. true).

  2. Int (resp. Zero) builds an integer option initialized to a specified value (resp. to 0).

  3. String (resp. Empty_string ) builds a string option initialized to a specified value
     (resp. to the empty string "").

  4. String_set builds an option taking a set of strings in argument (initialized to the
     empty set).

                                 4.10. COMMAND LINE OPTIONS

  5. Kernel_function_set builds an option taking a set of kernel functions in argument
     (initialized to the empty set).

Each functor takes as argument (at least) the name of the command line option corresponding
to the parameter and a short description for this option.

Example 4.23 The parameter corresponding to the option -occurrence of the plug-in
occurrence is the module Print (defined in the file src/plugins/occurrence/
It is implemented as follows.
     module Print =
            let option_name = "-occurrence"
            let help = "print results of occurrence analysis"

So it is a boolean parameter initialized by default to false. The declared interface for this
module is simply
     module Print: Parameter_sig.Bool

Another example is the parameter corresponding to the option -impact-pragma of the
plug-in impact. This parameter is defined by the module Pragma (defined in the file
src/plugins/impact/ It is implemented as follows.
     module Pragma =
            let option_name = "-impact-pragma"
            let arg_name = "f1, ..., fn"
            let help = "use the impact pragmas in the code of functions f1,...,fn"

Thus it is a set of kernel_functions initialized by default to the empty set. Frama-C uses
the field arg_name in order to print the name of the argument when displaying help. The
field help is the help message itself. The Interface for this module is simple:
     module Pragma: Parameter_sig.Kernel_function_set

Recommendation 4.2 Parameters of a same plug-in plugin should belong to a module
called Options, Plugin_options, Parameters or Plugin_parameters inside the plug-in di-

Using a kernel parameters or a parameter of your own plug-in is very simple: you have simply
to call the function get corresponding to your parameter.

Example 4.24 To know whether Frama-C uses unicode, just write
     Kernel.Unicode.get ()

Inside the plug-in From, just write
     From_parameters.ForceCallDeps.get ()

in order to know whether callsite-wise dependencies have been required.

                         CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

Using a parameter of a plug-in p in another plug-in p′ requires the use of module
Dynamic.Parameter: since the module defining the parameter is not visible from the out-
side of its plug-in, you have to use the dynamic API of plug-in p in which p’s parameters
are automatically registered (see Section 4.8.3). The module Dynamic.Parameter defines
sub-modules which provide easy access to parameters according to their OCaml types.

Example 4.25 Outside the plug-in From, just write
     Dynamic.Parameter.Bool.get "-calldeps" ()

in order to know whether callsite-wise dependencies have been required.

4.10.2    Tuning

It is possible to modify the default behavior of command line options in several ways by
applying functions just before or just after applying the functor defining the corresponding
Functions which can be applied afterwards are defined in the output signature of the applied

Example 4.26 Here is how the option "-slicing-level" restricts the range of its argument to
the interval [0; 3].
     module Calls =
             let option_name = "-slicing-level"
             let default = 2
             let arg_name = ""
             let help = "..." (∗ skipped here ∗)
     let () = Calls.set_range ∼min:0 ∼max:3

Functions which can be applied before applying the functor are defined in the module

Example 4.27 Here is how the opposite of option "-safe-arrays" is renamed into "-unsafe-
arrays" (otherwise, by default, it would be "-no-safe-arrays").
     let () = Parameter_customize.set_negative_option_name "-unsafe-arrays"
     module SafeArrays =
             let module_name = "SafeArrays"
             let option_name = "-safe-arrays"
             let help = "for arrays that are fields inside structs, assume that \
                         accesses are in bounds"

4.11     Initialization Steps

Prerequisite: Knowledge of linking of OCaml files.

                                   4.11. INITIALIZATION STEPS

 In a standard way, Frama-C modules are initialized in the link order which remains mostly
 unspecified, so you have to use side-effects at module initialization time carefully.

This section details the different stages of the Frama-C boot process to help advanced plug-in
developers interact more deeply with the kernel process. It can also be useful for debugging
initialization problems.
As a general rule, plug-in routines must never be executed at link time. Any useful code, be
it for registration, configuration or C-code analysis, should be registered as function hooks to
be executed at a proper time during the Frama-C boot process. In general, registering and
executing a hook is tightly coupled with handling the command line parameters.
The parsing of the command line parameters is performed in several phases and stages , each
one dedicated to specific operations. Following the general rule stated at the beginning of
this section, even the kernel services of Frama-C are internally registered as hooks routines
to be executed at a specific stage of the initialization process, among plug-ins ones.
From the plug-in developer point of view, the hooks are registered by calling the
run_after_xxx_stage routines in Cmdline module and extend routine in the Db.Main mod-
The initialization phases and stages of Frama-C are described below, in their execution order.

A – The Initialization Stage: this stage initializes Frama-C compilation units, following
    some partially specified order. More precisely:

     1. the architecture dependencies depicted on Figure 3.1 (cf. p. 41) are respected. In
        particular, the kernel services are linked first, then the kernel integrated types for
        plug-ins, and finally the plug-ins are linked in unspecified order;
     2. when the GUI is present, for any plug-in p, the non-gui modules of p are always linked
        before the gui modules of p;
     3. finally, the module Boot is linked at the very end of this stage.

     Plug-in developers cannot customize this stage. In particular, the module Cmdline (one
     of the first linked modules, see Figure 3.1) performs a very early configuration stage,
     such as setting the global verbosity and debugging levels.

B – The Early Stage: this stage initializes the kernel services. More precisely:

     (a) first, the parsing of command line options registered for the Cmdline.Early stage;
    (b) then, all functions registered through Cmdline.run_after_early_stage are exe-
        cuted in an unspecified order.

C – The Extending Stage: the searching and loading of dynamically linked plug-ins,
    scripts and modules is performed at this stage. More precisely:

     (a) the command line options registered for the Cmdline.Extending stage are treated,
         such as -load-script
    (b) the hooks registered through Cmdline.run_during_extending_stage are executed.
        Such hooks include kernel function calls for searching, loading and linking the various
        plug-ins and scripts compilation units, with respect to the command line options
        parsed during stages B and C.

                         CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

D – The Running Phase: the command line is split into several groups of command line
    arguments, each of them separated by an option -then or an option -then-on p (thus
    if there is n occurrences of -then or -then-on p, then there are n + 1 groups). For each
    group, the following stages are executed in sequence: all the stages are executed on the
    first group provided on the command line, then they are executed on the second group,
    and so on.

    1. The Extended Stage: this step is reserved for commands which require that all
       plug-ins are loaded but which must be executed very early. More precisely:
       (a) the command line options registered for the Cmdline.Extended stage are treated,
           such as -verbose-* and -debug-*;
       (b) the hooks registered through Cmdline.run_after_extended_stage. Most of
           these registered hooks come from postponed internal-state dependencies (see Sec-
           tion 4.9.3).
       Remark that both statically and dynamically linked plug-ins have been loaded at this
       stage. Verbosity and debug level for each plug-in are determined during this stage.
    2. The Exiting Stage: this step is reserved for commands that make Frama-C exit
       before starting any analysis at all, such as printing help information:
       (a) the command line options registered for the Cmdline.Exiting stage are treated;
       (b) the hooks registered through Cmdline.run_after_exiting_stage are exe-
           cuted in an unspecified order. All these functions should do nothing (using
           Cmdline.nop) or raise Cmdline.Exit for stopping Frama-C quickly.
    3. The Loading Stage: this is where the initial state of Frama-C can be replaced by
       another one. Typically, it would be loaded from disk through the -load option. As
       for the other stages:
       (a) first, the command line options registered for the Cmdline.Loading stage are
       (b) then, the hooks registered through Cmdline.run_after_loading_stage are ex-
           ecuted in an unspecified order. These functions actually change the initial state
           of Frama-C with the specified one. The Frama-C kernel verifies as far as possible
           that only one new-initial state has been specified.
       Normally, plug-ins should never register hooks for this stage unless they actually set
       a different initial state than the default one. In such a case:
         They must call the function Cmdline.is_going_to_load while initializing.

    4. The Configuring Stage: this is the usual place for plug-ins to perform special
       initialization routines if necessary, before having their main entry points executed.
       As for previous stages:
       (a) first, the command line options registered for the Cmdline.Configuring stage
           are treated. Command line parameters that do not begin by a hyphen (character
           ’-’) are not options and are treated as C files. Thus they are added to the list
           of files to be preprocessed or parsed for building the AST (on demand);
       (b) then, the hooks registered through Cmdline.run_after_configuring_stage are
           executed in an unspecified order.
    5. The Setting Files Stage: this stage sets the C files to analyze according to those
       indicated on the command line. More precisely:

                              4.12. CUSTOMIZING THE AST CREATION

        (a) first, each argument of the command line which does not begin by a hyphen
            (character ’-’) is registered for later analysis;
       (b) then, the hooks registered through Cmdline.run_after_setting_files are ex-
           ecuted in an unspecified order.
    6. The Main Stage: this is the step where plug-ins actually run their main entry
       points registered through Db.Main.extend. For all intents and purposes, you should
       consider that this stage is the one where these hooks are executed.

4.12     Customizing the AST creation

Prerequisite: None.

Plug-ins may modify the way source files are transformed into the AST over which the
analyses are performed. Customization of the front-end of Frama-C can be done at several

A – Parsing: this stage takes care of converting an individual source file into a parsed AST
    (a.k.a Cabs, which differs from the type-checked AST on which most analyses operate).
    By default, source files are treated as C files, possibly needing a pre-processing phase.
    It is possible to tell Frama-C to use another parser for files ending with a given suffix by
    registering this parser with the File.new_file_type function. Suffixes .h, .i, .c and
    .ci are reserved for Frama-C kernel. The registered parser is supposed to return a pair
    consisting of a type-checked AST (Cil_types.file) and a parsed AST (Cabs.file).
    The former can be obtained from the latter with the Cabs2cil.convFile function,
    which guarantees that the resulting Cil_types.file respects all invariants expected by
    the Frama-C kernel.

B – Type-checking: a normal Cabs.file (i.e. not obtained through a custom parsing
    function) can be transformed before being type-checked. Transformation hooks are
    registered through Frontc.add_syntactic_transformation.

C – After linking: Once all source files have been processed, they are all linked together
    in a single AST. Transformations can be performed on the resulting AST at two stages:

    1. before clean-up (i.e. removal of useless temporary variables and prototypes that are
       never called). At that stage, global tables indexing information related to the AST
       have not yet been filled.
    2. after clean-up. At this stage, index tables are filled, and can thus be used. On the
       other hand, the transformation must take care itself of keeping in sync the AST and
       the tables

    Registering a transformation for this stage is done through the func-
    tion          File.add_code_transformation_before_cleanup                  (respectively
    File.add_code_transformation_after_cleanup). If such a transformation modify
    the control-flow graph of a function f, in particular by adding statements, it must call
    File.must_recompute_cfg, in order to have the graph recomputed afterwards.

                          CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

4.13     Customizing the machine model

Prerequisite: None.

Several aspects of the C standard that are implementation-defined, such as the width of
standard integer types, endianness, signedness of the char type, etc., as well as a few compiler
and architecture specific features, can be customized using a machdep configuration, defining
a new machine model.
To create a new machine model, define an instance of Cil_types.mach. You can base
it on the examples available in tests/misc/custom_machdep/ and
src/kernel_internals/runtime/ The new definition can be added to Frama-
C’s database using File.new_machdep.

Example 4.28 A custom machine description may be implemented as follows (the meaning
of each field is presented later in this section):
     let my_machine =
        version           = "generic C compiler for my machine";
       compiler           = "generic";
       cpp_arch_flags = [];
        sizeof_short      = 2;
        sizeof_int        = 4;
        sizeof_long       = 4;
        sizeof_longlong = 8;
        sizeof_ptr        = 4;
        sizeof_float      = 4;
       sizeof_double      = 8;
       sizeof_longdouble = 12;
        sizeof_void       = 1;
       sizeof_fun         = 1;
       size_t = "unsigned long";
       wchar_t = "int";
        ptrdiff_t = "int";
        alignof_short = 2;
        alignof_int = 4;
       alignof_long = 4;
        alignof_longlong = 4;
       alignof_ptr = 4;
        alignof_float = 4;
       alignof_double = 4;
       alignof_longdouble = 4;
        alignof_str = 1;
       alignof_fun = 1;
        alignof_aligned = 16;
       char_is_unsigned = false;
         const_string_literals = true;
        little_endian = true;
       underscore_name = false ;
       has__builtin_va_list = true;

      let () = File.new_machdep "my_machine" my_machine

                           4.13. CUSTOMIZING THE MACHINE MODEL

After this code is loaded, Frama-C can be instructed to use the new machine model using the
-machdep command line option.
If you intend to use Frama-C’s standard library headers, you must also do the following:

  • define constant __FC_MACHDEP_<CUSTOM>, replacing <CUSTOM> with the name
    (in uppercase letters) of your created machdep; this can be done via

  • provide a header file with macro definitions corresponding to your OCaml definitions.
    For the most part, these are macros prefixed by __FC_, corresponding to standard
    C macro definitions, e.g., __FC_UCHAR_MAX. These definitions are used by Frama-C’s
    <limits.h> and other headers to provide the standard C definitions. The test file
    tests/misc/custom_machdep/__fc_machdep_custom.h (reproduced below) contains
    a complete example of the required definitions. Other examples can be found in

Make sure that your custom header defines the __FC_MACHDEP include guard, and that the
program you are analyzing includes this header before all other headers. One way to ensure
this without having to modify any source files is to use an option such as -include in GCC.

Example 4.29 Contents of tests/misc/custom_machdep/__fc_machdep_custom.h, used
as example for creating custom machdeps. Notice the unusual size for int (3 bytes), selected
for testing purposes only, and inconsistent with the chosen values for INT_MIN and INT_MAX,
which do not fit in 3 bytes.
     /* skeleton of a real custom machdep header.
        Note: the values provided here are merely for illustrative purposes
             and are not necessarily consistent between them. */
     #ifndef __FC_MACHDEP
     #define __FC_MACHDEP

     #ifdef __FC_MACHDEP_CUSTOM

     /* Constants required by the C standard */
     #undef __CHAR_UNSIGNED__
     #define __WORDSIZE 32
     #define __SIZEOF_SHORT 2
     #define __SIZEOF_INT 3
     #define __SIZEOF_LONG 4
     #define __SIZEOF_LONGLONG 8
     #define __CHAR_BIT 8
     #define __PTRDIFF_T int
     #define __SIZE_T unsigned int

     #define   __FC_SCHAR_MIN (-128)
     #define   __FC_SCHAR_MAX 127
     #define   __FC_UCHAR_MAX 255
     #define   __FC_SHRT_MIN (-32768)
     #define   __FC_SHRT_MAX 32767
     #define   __FC_USHRT_MAX 65535
     #define   __FC_INT_MIN (-2147483647 - 1)
     #define   __FC_INT_MAX 2147483647
     #define   __FC_UINT_MAX 4294967295U


#define   __FC_LONG_MIN (-2147483647L -1L)
#define   __FC_LONG_MAX 2147483647L
#define   __FC_ULONG_MAX 4294967295UL
#define   __FC_LLONG_MIN (-9223372036854775807LL -1LL)
#define   __FC_LLONG_MAX 9223372036854775807LL
#define   __FC_ULLONG_MAX 18446744073709551615ULL

#define __INT_MAX_T signed long long
#define __UINT_MAX_T unsigned long long

#define __FC_PATH_MAX 256

/* Optional constants */
#define __INT8_T signed char
#define __UINT8_T unsigned char
#define __INT16_T signed short
#define __UINT16_T unsigned short

#define   __INTPTR_T signed long
#define   __UINTPTR_T unsigned long
#define   __INT32_T signed long
#define   __UINT32_T unsigned long
#define   __INT64_T signed long long
#define   __UINT64_T unsigned long long

/* Required constants */
#define __INT_LEAST8_T signed char
#define __UINT_LEAST8_T unsigned char
#define __INT_LEAST16_T signed short
#define __UINT_LEAST16_T unsigned short
#define __INT_LEAST32_T signed long
#define __UINT_LEAST32_T unsigned long
#define __INT_LEAST64_T signed long long
#define __UINT_LEAST64_T unsigned long long

#define   __INT_FAST8_T signed char
#define   __UINT_FAST8_T unsigned char
#define   __INT_FAST16_T signed int
#define   __UINT_FAST16_T unsigned int
#define   __INT_FAST32_T signed long
#define   __UINT_FAST32_T unsigned long
#define   __INT_FAST64_T signed long long
#define   __UINT_FAST64_T unsigned long long

/* POSIX */
#define __SSIZE_T int
/* stdio.h */
#define __FC_L_tmpnam 1024
/* stdint.h */
#define __FC_INTMAX_MIN (-9223372036854775807LL -1LL)
#define __FC_INTMAX_MAX 9223372036854775807LL
#define __FC_UINTMAX_MAX 18446744073709551615ULL

                      4.13. CUSTOMIZING THE MACHINE MODEL

#define   __FC_EOF (-1)
#define   __FC_FOPEN_MAX 20
#define   __FC_RAND_MAX 32767
#define   __WCHAR_T unsigned short

/* for stdarg.h */
#define __FC_VA_LIST_T char*

/* for time.h */
#define __FC_TIME_T long

/* for wchar.h */
#define __WINT_T unsigned int
#define __FC_WEOF (0xFFFFFFFFU)
#define __FC_WINT_MIN 0

/* for errno.h */

#define   __FC_EPERM 1
#define   __FC_ENOENT 2
#define   __FC_ESRCH 3
#define   __FC_EINTR 4
#define   __FC_EIO 5
#define   __FC_ENXIO 6
#define   __FC_E2BIG 7
#define   __FC_ENOEXEC 8
#define   __FC_EBADF 9
#define   __FC_ECHILD 10
#define   __FC_EAGAIN 11
#define   __FC_ENOMEM 12
#define   __FC_EACCES 13
#define   __FC_EFAULT 14
#define   __FC_ENOTBLK 15
#define   __FC_EBUSY 16
#define   __FC_EEXIST 17
#define   __FC_EXDEV 18
#define   __FC_ENODEV 19
#define   __FC_ENOTDIR 20
#define   __FC_EISDIR 21
#define   __FC_EINVAL 22
#define   __FC_ENFILE 23
#define   __FC_EMFILE 24
#define   __FC_ENOTTY 25
#define   __FC_ETXTBSY 26
#define   __FC_EFBIG 27
#define   __FC_ENOSPC 28
#define   __FC_ESPIPE 29
#define   __FC_EROFS 30
#define   __FC_EMLINK 31
#define   __FC_EPIPE 32
#define   __FC_EDOM 33
#define   __FC_ERANGE 34
#define   __FC_EDEADLK 35
#define   __FC_ENAMETOOLONG 36


#define   __FC_ENOLCK 37
#define   __FC_ENOSYS 38
#define   __FC_ENOTEMPTY 39
#define   __FC_ELOOP 40
#define   __FC_ENOMSG 42
#define   __FC_EIDRM 43
#define   __FC_ECHRNG 44
#define   __FC_EL2NSYNC 45
#define   __FC_EL3HLT 46
#define   __FC_EL3RST 47
#define   __FC_ELNRNG 48
#define   __FC_EUNATCH 49
#define   __FC_ENOCSI 50
#define   __FC_EL2HLT 51
#define   __FC_EBADE 52
#define   __FC_EBADR 53
#define   __FC_EXFULL 54
#define   __FC_ENOANO 55
#define   __FC_EBADRQC 56
#define   __FC_EBADSLT 57
#define   __FC_EBFONT 59
#define   __FC_ENOSTR 60
#define   __FC_ENODATA 61
#define   __FC_ETIME 62
#define   __FC_ENOSR 63
#define   __FC_ENONET 64
#define   __FC_ENOPKG 65
#define   __FC_EREMOTE 66
#define   __FC_ENOLINK 67
#define   __FC_EADV 68
#define   __FC_ESRMNT 69
#define   __FC_ECOMM 70
#define   __FC_EPROTO 71
#define   __FC_EMULTIHOP 72
#define   __FC_EDOTDOT 73
#define   __FC_EBADMSG 74
#define   __FC_EOVERFLOW 75
#define   __FC_ENOTUNIQ 76
#define   __FC_EBADFD 77
#define   __FC_EREMCHG 78
#define   __FC_ELIBACC 79
#define   __FC_ELIBBAD 80
#define   __FC_ELIBSCN 81
#define   __FC_ELIBMAX 82
#define   __FC_ELIBEXEC 83
#define   __FC_EILSEQ 84
#define   __FC_ERESTART 85
#define   __FC_ESTRPIPE 86
#define   __FC_EUSERS 87
#define   __FC_ENOTSOCK 88
#define   __FC_EDESTADDRREQ 89
#define   __FC_EMSGSIZE 90
#define   __FC_EPROTOTYPE 91
#define   __FC_ENOPROTOOPT 92

                          4.13. CUSTOMIZING THE MACHINE MODEL

    #define   __FC_EPROTONOSUPPORT 93
    #define   __FC_ESOCKTNOSUPPORT 94
    #define   __FC_ENOTSUP 95
    #define   __FC_EOPNOTSUPP 95
    #define   __FC_EPFNOSUPPORT 96
    #define   __FC_EAFNOSUPPORT 97
    #define   __FC_EADDRINUSE 98
    #define   __FC_EADDRNOTAVAIL 99
    #define   __FC_ENETDOWN 100
    #define   __FC_ENETUNREACH 101
    #define   __FC_ENETRESET 102
    #define   __FC_ECONNABORTED 103
    #define   __FC_ECONNRESET 104
    #define   __FC_ENOBUFS 105
    #define   __FC_EISCONN 106
    #define   __FC_ENOTCONN 107
    #define   __FC_ESHUTDOWN 108
    #define   __FC_ETOOMANYREFS 109
    #define   __FC_ETIMEDOUT 110
    #define   __FC_ECONNREFUSED 111
    #define   __FC_EHOSTDOWN 112
    #define   __FC_EHOSTUNREACH 113
    #define   __FC_EALREADY 114
    #define   __FC_EINPROGRESS 115
    #define   __FC_ESTALE 116
    #define   __FC_EUCLEAN 117
    #define   __FC_ENOTNAM 118
    #define   __FC_ENAVAIL 119
    #define   __FC_EISNAM 120
    #define   __FC_EREMOTEIO 121
    #define   __FC_EDQUOT 122
    #define   __FC_ENOMEDIUM 123
    #define   __FC_EMEDIUMTYPE 124
    #define   __FC_ECANCELED 125
    #define   __FC_ENOKEY 126
    #define   __FC_EKEYEXPIRED 127
    #define   __FC_EKEYREVOKED 128
    #define   __FC_EKEYREJECTED 129
    #define   __FC_EOWNERDEAD 130
    #define   __FC_ENOTRECOVERABLE 131
    #define   __FC_ERFKILL 132
    #define   __FC_EHWPOISON 133

      error "I'm supposed to be called with __FC_MACHDEP_CUSTOM macro defined"

An example of the complete command-line is presented below, for a custom machdep
called myarch, defined in file and with stdlib constants defined in
      frama-c -load-script -machdep myarch \
        -cpp-extra-args="-D__FC_MACHDEP_MYARCH -include machdep_myarch.h"

                             CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

4.14       Machdep record fields

Each field in the machdep record is succintly described in the Cil_types module. We present
below a thorough description of each field.

version : human-readable textual description of the machdep.

compiler : defines whether special compiler-specific extensions will be enabled. It should be
     one of the strings below:

       msvc : enables Cil.msvcMode, that is, MSVC (Visual Studio)-specific extensions;
        gcc : enables Cil.gccMode, that is, GCC-specific extensions;
 generic (or any other string): no special compiler-specific extensions.

       Note that some compiler extensions, such as attributes, are always enabled.

cpp_arch_flags : list of arguments to be added to the command-line when invoking the C
     preprocessor. Typically used to ensure that multiarch compilers apply the appropriate
     predefined macros14 . E.g. use ["-m32"] for a 32-bit machdep when preprocessing
     with a 64-bit multiarch GCC. Note that, in practice, very few programs rely on such
     predefined macros, such as __x86_64 and __i386.

sizeof_short : size (in bytes) of the short type.

sizeof_int : size (in bytes) of the int type.

sizeof_long : size (in bytes) of the long type.

sizeof_longlong : size (in bytes) of the long long type. Note that machdeps (for compiler
     "gcc" in particular) must always have at least one type that is 8 bytes wide, which is
     typically long long.

sizeof_ptr : size (in bytes) of an object (non-function) pointer.

sizeof_float : size (in bytes) of a single-precision floating point. In implementations com-
     pliant with ISO/IEC/IEEE 60559 -IEEE 754, this is always 4.

sizeof_double : size (in bytes) of a double-precision floating point. In implementations
     compliant with ISO/IEC/IEEE 60559 - IEEE 754, this is always 8.

sizeof_longdouble : size (in bytes) of a long double floating point. Note: type
     long double is currently not supported by existing Frama-C plugins, but this field
     exists for future expansion, and to compute sizeof of aggregates properly.

sizeof_void : the result of evaluating sizeof(void) by the compiler (or 0 if unsupported).

sizeof_fun : the result of evaluating sizeof(f), where f is a function (not a function
     pointer) by the compiler (or negative if unsupported).

size_t : a string containing the actual type that size_t expands to, e.g. "unsigned long".
    Note that the sizes of standard integer types are already defined in the machdep, so they do not depend
on these flags.

                                4.14. MACHDEP RECORD FIELDS

wchar_t : a string containing the actual type that wchar_t expands to. If unsupported, you
     can use int.

ptrdiff_t : a string containing the actual type that ptrdiff_t expands to. If unsupported,
     you can use int.

alignof_short : the result of evaluating _Alignof(short).

alignof_int : the result of evaluating _Alignof(int).

alignof_long : the result of evaluating _Alignof(long).

alignof_longlong : the result of evaluating _Alignof(long long).

alignof_ptr : the result of evaluating _Alignof(char*) (or any other pointer, including
     function pointers).

alignof_float : the result of evaluating _Alignof(float).

alignof_double : the result of evaluating _Alignof(double).

alignof_longdouble : the result of evaluating _Alignof(long double).

alignof_str : the result of evaluating _Alignof("a") (a literal string).

alignof_fun : the result of evaluating _Alignof(f), where f is a function (or negative if

alignof_aligned : the default alignment of a type having the aligned attribute (or 1 if un-
     supported). This corresponds to the default alignment when using #pragma packed()
     without a numeric argument.

char_is_unsigned : whether type char is unsigned.

const_string_literals : whether string literals have const chars, or are writable.
     If true, the following code has undefined behavior, otherwise it is defined:
     char *s = "no"; s[0] = 'g';.

little_endian : whether the machine is little endian.

underscore_name : whether the compiler generates assembly labels by prepending _ to the
     identifier. That is, will function foo() have the label foo, or _foo?

has__builtin_va_list : whether __builtin_va_list is a (built-in) type known by the

__thread_is_keyword : whether __thread is a keyword (otherwise, it can be used as a
     standard identifier).

Writing a new machdep Writing a machdep for a new architecture is not trivial, due
to the fact that some steps are hard to automate. If you have a working compiler for the
target architecture, you can use it to produce an executable that will print the contents of
expressions such as sizeof(long), _Alignof(int), etc. You can also use the compiler to
test for unsupported features. In case printf is not available, you can use the exit code of
the program (return code of main). In case you can only preprocess, but not compile and
run the program, the assembly code may provide some useful data.

                            CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

4.15      Visitors

Prerequisite: Knowledge of OCaml object programming.

Module Cil offers a visitor, Cil.cilVisitor, that allows to traverse (parts of) an AST.
It is a class with one method per type of the AST, whose default behavior is simply to
call the method corresponding to its children. This is a convenient way to perform local
transformations over a whole Cil_types.file by inheriting from it and redefining a few
methods. However, the original Cil visitor is of course not aware of the internal state of
Frama-C itself. Hence, there exists another visitor, Visitor.generic_frama_c_visitor,
which handles projects in a transparent way for the user. There are very few cases where the
plain Cil visitor should be used.

 Basically, as soon as the initial project has been built from the C source files (i.e. one of
 the functions File.init_∗ has been applied), only the Frama-C visitor should occur.

There are a few differences between the two (the Frama-C visitor inherits from the Cil one).
These differences are summarized in Section 4.15.6, which the reader already familiar with
Cil is invited to read carefully.

4.15.1     Entry Points

Module Cil offers various entry points for the visitor.         They are functions called
Cil.visitCilAstType where astType is a node type in the Cil’s AST. Such a function takes
as argument an instance of a cilVisitor and an astType and gives back an astType trans-
formed according to the visitor. The entry points for visiting a whole Cil_types.file
(Cil.visitCilFileCopy, Cil.visitCilFile and visitCilFileSameGlobals) are slightly
different and do not support all kinds of visitors. See the documentation attached to them
in cil.mli for more details.

4.15.2     Methods

As said above, there is a method for each type in the Cil AST (including for
logic annotation). For a given type astType, the method is called vastType 15 , and
has type astType→astType’ visitAction, where astType’ is either astType or ast-
Type list (for instance, one can transform a global into several ones). visitAction
describes what should be done for the children of the resulting AST node, and
is presented in the next section.     In addition, some types have two modes of
visit: one for the declaration and one for use.       This is the case for varinfo
(vvdec and vvrbl), logic_var (vlogic_var_decl and vlogic_var_use) logic_info
(vlogic_info_decl and vlogic_info_use), logic_type_info (vlogic_type_info_decl
and vlogic_type_info_use), and logic_ctor_info (vlogic_ctor_info_decl and
vlogic_ctor_info_use). More detailed information can be found in cil.mli.

 For the Frama-C visitor, two methods, vstmt and vglob take care of maintaining the
 coherence between the transformed AST and the internal state of Frama-C . Thus they
 must not be redefined. One should redefine vstmt_aux and vglob_aux instead.

    This naming convention is not strictly enforced. For instance the method corresponding to offset is

                                         4.15. VISITORS

4.15.3    Action Performed

The return value of visiting methods indicates what should be done next. There are six

  • SkipChildren the visitor does not visit the children;

  • ChangeTo v the old node is replaced by v and the visit stops;

  • DoChildren the visit goes on with the children; this is the default behavior;

  • JustCopy is only meaningful for the copy visitor. Indicates that the visit should go on
    with the children, but only perform a fresh copy of the nodes

  • ChangeToPost(v,f) the old node is replaced by v, and f is applied to the result. This is
    however not exactly the same thing as returning ChangeTo(f(v)). Namely, in the case
    of vglob_aux, f will be applied to v only after the operations needed to maintain the
    consistency of Frama-C’s internal state with respect to the AST have been performed.
    Thus, ChangeToPost should be used with extreme caution, as f could break some
    invariants of the kernel.

  • DoChildrenPost f visit the children and apply the given function to the result.

  • JustCopyPost(f) is only meaningful for the copy visitor. Performs a fresh copy of the
    nodes and all its children and applies f to the copy.

  • ChangeDoChildrenPost(v,f) the old node is replaced by v, the visit goes on with the
    children of v, and when it is finished, f is applied to the result. In the case of vstmt_aux,
    f is called after the annotations in the annotations table have been visited, but before
    they are attached to the new statement, that is, they will be added to the result of
    f. Similarly, vglob_aux will consider the result of f when filling the table of globals.
    Note that ChangeDoChildrenPost(x,f) where x is the current node is not equivalent
    to DoChildrenPost f, as in the latter case, the visitor mechanism knows that it still
    deals with the original node.

4.15.4    Visitors and Projects

Copy visitors (see next section) implicitly take an additional argument, which is the project
in which the transformed AST should be put in.
Note that the tables of the new project are not filled immediately. Instead, actions are
queued, and performed when a whole Cil_types.file has been visited. One can access the
queue with the get_filling_actions method, and perform the associated actions on the
new project with the fill_global_tables method.
In-place visitors always operate on the current project (otherwise, two projects would risk
sharing the same AST).

4.15.5    In-place and Copy Visitors

The visitors take as argument a Visitor_behavior.t, which comes in two flavors: inplace
and copy. In the in-place mode, nodes are visited in place, while in the copy mode, nodes
are copied and the visit is done on the copy. For the nodes shared across the AST (varinfo,

                          CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

compinfo, enuminfo, typeinfo, stmt, logic_var, logic_info and fieldinfo), sharing is of
course preserved, and the mapping between the old nodes and their copy can be manipulated
explicitly through the following modules, which define a function for each of the types above.

  • Reset allows to reset the mappings.

  • Get gets the copy corresponding to an old value. If the given value is not known, it
    behaves as the identity.

  • Memo is similar to Get, except that if the given value is not known, a new binding is

  • Get_orig gets the original value corresponding to a copy (and behaves as the identity
    if the given value is not known).

  • Setname sets a copy for a given value. Be sure to use it before any occurrence of the
    old value has been copied, or sharing will be lost.

  • Set_orig sets the original value corresponding to a given copy.

 Functions from the Get_origname modules allow to retrieve additional information tied
 to the original AST nodes. Its result must not be modified in place (this would defeat the
 purpose of operating on a copy to leave the original AST untouched). Moreover, note that
 whenever the index used for name is modified in the copy, the internal state of the visitor
 behavior must be updated accordingly (via the function) for
 to give correct results.

The list of such indices is given Figure 4.3.

                            Type           Index
                            varinfo        vid
                            compinfo       ckey
                            enuminfo       ename
                            typeinfo       tname
                            stmt           sid
                            logic_info     l_var_info.lv_id
                            logic_var      lv_id
                            fieldinfo      fname and fcomp.ckey

                              Figure 4.3: Indices of AST nodes.

 Last, when using a copy visitor, the actions (see previous section) SkipChildren and
 ChangeTo must be used with care, i.e. one has to ensure that the children are fresh.
 Otherwise, the new AST will share some nodes with the old one. Even worse, in such
 a situation the new AST might very well be left in an inconsistent state, with uses of
 shared node (e.g. a varinfo for a function f in a function call) which do not match the
 corresponding declaration (e.g the GFun definition of f).
 When in doubt, a safe solution is to use JustCopy instead of SkipChildren and
 ChangeDoChildrenPost(x,fun x -> x) instead of ChangeTo(x).

                                         4.15. VISITORS

4.15.6     Differences Between the Cil and Frama-C Visitors

As said in Section 4.15.2, vstmt and vglob should not be redefined. Use vstmt_aux and
vglob_aux instead. Be aware that the entries corresponding to statements and globals in
Frama-C tables are considered more or less as children of the node. In particular, if the
method returns ChangeTo action (see Section 4.15.3), it is assumed that it has taken care
of updating the tables accordingly, which can be a little tricky when copying a file from a
project to another one. Prefer ChangeDoChildrenPost. On the other hand, a SkipChildren
action implies that the visit will stop, but the information associated to the old value will be
associated to the new one. If the children are to be visited, it is undefined whether the table
entries are visited before or after the children in the AST.

4.15.7     Example

Here is a small copy visitor that adds an assertion for each division in the program, stating
that the divisor is not zero:
     open Cil_types
     open Cil

     module M = Plugin.Register

     (∗ Each annotation in Frama−C has an emitter, for traceability.
        We create thus our own, and says that it will only be used to emit code
        annotations, and that these annotations do not depend
        on Frama−C's command line parameters.
     let syntax_alarm =
         "Syntactic check" [ Emitter.Code_annot ] ∼correctness:[] ∼tuning:[]

      class non_zero_divisor prj = object ( self )
         inherit Visitor .generic_frama_c_visitor (Visitor_behavior.copy prj)

         (∗ A division is an expression: we override the vexpr method ∗)
         method! vexpr e = match e.enode with
           | BinOp((Div|Mod), _, denom, _) →
             (∗ denom might contain references to variables. Since we haven't visited
                 the node yet, they're bound to the varinfo of the original project.
                 we perform a plain copy, which will just ensure that they are replaced
                 with varinfos of the new project: frama_c_plain_copy is a visitor that
                 performs a copy, using the same correspondance tables as self. ∗)
             let denom = Visitor.visitFramacExpr self#frama_c_plain_copy denom in
             let logic_denom = Logic_utils.expr_to_term ∼coerce:false denom in
             let assertion = Logic_const.prel (Rneq, logic_denom, Cil.lzero ()) in
             (∗ At this point, we have built the assertion we want to insert. It remains
                 to attach it to the correct statement. The cil visitor maintains the
                 information of which statement and function are currently visited in
                 the [current_stmt] and [current_kf] methods, which return None when
                 outside of a statement or a function , e.g. when visiting a global
                 declaration. Here, it necessarily returns [Some]. ∗)
             let stmt = match self#current_kinstr with
                | Kglobal → assert false
                | Kstmt s → s

                          CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

             let kf = Option.get self#current_kf in
             (∗ The above statement and function are related to the original project. We
                 need to attach the new assertion to the corresponding statement and
                 function of the new project. Cil provides functions to convert a
                 statement (function) of the original project to the corresponding
                 one of the new project. ∗)
             let new_stmt = Visitor_behavior.Get.stmt self#behavior stmt in
             let new_kf = Visitor_behavior.Get.kernel_function self#behavior kf in
             (∗ Since we are copying the file in a new project, we cannot insert
                 the annotation into the current table, but in the table of the new
                 project. To avoid the cost of switching projects back and forth,
                 all operations on the new project are queued until the end of the
                 visit , as mentioned above. This is done in the following statement. ∗)
               (fun () →
                   Annotations.add_assert syntax_alarm ∼kf:new_kf new_stmt assertion)
                self # get_filling_actions ;
           | _ → DoChildren

     (∗ This function creates a new project initialized with the current file plus
        the annotations related to division. ∗)
     let create_syntactic_check_project () =
         (File.create_project_from_visitor "syntactic check" (new non_zero_divisor))

      let () = Db.Main.extend create_syntactic_check_project

4.16       Logical Annotations
Prerequisite: None.

Logical annotations set by the users in the analyzed C program are part of the AST. However
others annotations (those generated by plug-ins) are not directly in the AST because it would
contradict the rule “an AST must never be modified inside a project” (see Section 4.9.5).
So all the logical annotations (including those set by the users) are put in global projectified
tables maintained up-to-date by the Frama-C kernel. Anytime a plug-in wants either to access
to or to add/delete an annotation, it must use the corresponding modules or functions and not
the annotations directly stored in the AST. These modules and functions are the following.

  • Module Annotations which contains the database of annotations related to the AST
    (global annotations, function contracts and code annotations). Adding or deleting an
    annotation requires to define an emitter by Emitter.create first.
  • Module Property_status should be used to get or to modify the validity status
    of logical properties. Modifying a property status requires to define an emitter by
    Emitter.create first. Key concepts and theoretical foundation of this module are
    described in an associated research paper [5].
  • Module Property provides access to all logical properties on which property statuses
    can be emitted. In particular, an ACSL annotation has to be converted into a property
    if you want to access its property statuses.

                             4.17. EXTENDING ACSL ANNOTATIONS

  • Modules Logic_const, Logic_utils, Logic_parse_string and Logic_to_c, contain
    several operations over annotations.

4.17     Extending ACSL annotations

Prerequisite: Knowledge of the ACSL specification language.

Frama-C supports the possibility of adding specific ACSL annotations in the form
of special clauses. Such clauses can be of different categories, as described by

  • A contract extension will be stored in the b_extendedb_extended field of

  • A global extension will be found as a global ACSL annotation in the form of a
    Cil_types.Dextended constructor.

  • A code annotation extension will be stored with the Cil_types.AExtended constructor.
    Such an extension has itself different flavors, determined by the type:

        – it can be meant to be evaluated exactly at the current program point (like an
          ACSL assert), or
        – it can be related to the next statement (or block), like an ACSL statement contract,
        – it can be a loop extension, or
        – it can be used both as a loop extension or be related to the next (non-loop)

An extension is characterized by its introducing keyword kw, or loop kw for a loop extension.
It is not possible to have the same keyword for two distinct extensions, especially if they
belong to different categories, as this would lead to ambiguities in the parser.
Once an extension is registered a clause of the form kw e1,...,en;, where each ei can be
any syntactically valid ACSL term or predicate, will be treated by the parser as belonging to
the extension kw.
Contract extension clauses must occur after assumes and requires clauses if any, but can be
freely mixed with other behavior clauses (post-conditions, assigns, frees and allocates).
Similarly, in a loop annotation, loop kw e1, ..., en; will be treated as belonging to the
kw extension. In case the loop annotation has a loop variant, the extension must occur
before. Otherwise, there is no ordering constraint with other loop annotations clauses.
Global extensions can either be a standalone global annotation, or a whole block of global
extensions, the latter case following the syntax of axiomatic blocks.
Finally, a code annotation extension must appear as a single code annotation, like any code
Code (and loop) extensions can be made specific to a set of existing behaviors using the
standard ACSL for construction. Namely, for bhv: loop kw e1, ..., en; will indicate
that the (loop) extension is supposed to be considered only when behavior bhv is active
(although it is ultimately up to the plugin to decide what to do with this information).

                         CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

An acsl_extension is a triple (id, kw, ext) where id is its unique ID, used in annotation
tables and generated by Logic_const.new_acsl_extension, kw identifies the extension, and
ext is an acsl_extension_kind and can take three forms:

  • Ext_id id with id an int that the plugin can use to refer to the annotation in its
    internal state. This identifier is under the full responsibility of the plugin and will
    never be used by the kernel.

  • Ext_preds preds with preds a possibly empty list of predicates.

  • Ext_terms terms with terms a possibly empty list of terms.

For the latter two cases, the corresponding list is traversed normally by the visitor (see
section 4.15).
In order for the extension to be recognized by the parser, it must be registered by one of the
following functions, depending on its category.

  • Acsl_extension.register_behavior

  • Acsl_extension.register_global

  • Acsl_extension.register_global_block

  • Acsl_extension.register_code_annot

  • Acsl_extension.register_code_annot_next_stmt

  • Acsl_extension.register_code_annot_next_loop

  • Acsl_extension.register_code_annot_next_both

Each function takes the following mandatory arguments:

  • kw the name of the extension,

  • typer the type-checking function itself.

  • status, a boolean flag indicating whether the extended annotation may have a validity
    status, and

During type-checking, the list [e1;...;en] will be given to typer, together with the current
typing environment (which allows discriminating between contract and loop extensions and
will have the appropriate logic labels set in the local environment). typer must return the
corresponding acsl_extension_kind (possibly adding an entry for key id in an internal
table if it chooses to return Ext_id id).
The first argument of typer is a Logic_typing.typing_context which provides lookup
functions for the various kinds of identifiers that are present in the environment, as well as
extensible type-checking functions for predicates, terms, and assigns clauses. Indeed, these
functions take themselves as argument a typing_context ctxt and will use the functions of
ctxt to type-check the children of the current node. Extensions can take advantage of this
open recursion to recognize only subtrees of an otherwise normal ACSL predicate or term.
For instance, the following code will let extension foo replace all occurrences of \foo by 42.

                              4.17. EXTENDING ACSL ANNOTATIONS

     open Logic_ptree
     open Cil_types
     open Logic_typing

      let type_foo typing_context _loc l =
         let type_term ctxt env expr =
           match expr.lexpr_node with
           | PLvar "\\foo" → Logic_const.tinteger ∼loc:expr.lexpr_loc 42
           | _ → typing_context.type_term ctxt env expr
         let typing_context = { typing_context with type_term } in
         let res =
           List .map (typing_context.type_term typing_context (Lenv.empty())) l
        Ext_terms res

      let () = Acsl_extension.register_behavior "foo" type_foo false

With this extension enabled, Frama-C will interpret the following clause in a given source file:
     /*@ foo 84 == \foo + \foo; */

as the following type-checked AST fragment:
     /*@ foo 84 == 42 + 42; */

If the extended clause is of kind Ext_preds l or Ext_terms l, and all the information of
the extension is contained in the list l, no function other than the typing function needs to
be registered. The parsing will use the standard way to parse untyped predicates and terms.
After typing, the visitor will traverse each element of l as well as any predicate or term
present in the AST. The pretty-printer will output these elements as a comma-separated list
preceded by kw (or loop kw if the extension is a loop annotation).
However, depending on the situation, the following optional functions can be provided to the
registration function in order to modify how ACSL extensions are handled by Frama-C:

  • preprocessor a transformer to apply on the untyped term or predicate read during
    the parsing phase,

  • visitor the visitor function to be applied when visiting the extension,

  • printer the pretty-printing function associated to the extension,

  • short_printer a function used to provide a brief textual representation of an extension.

The preprocessor function is applied just after parsing the extension terms. It takes the
list of untyped terms or predicates and can either return the same list (but reading it to do
some stuff) or return a new list. By default, this function is the identity.
The visitor function is used by the Frama-C visitors. It takes the current visitor, together
with the acsl_extension_kind of the extended clause and must returns a Cil.visitAction.
By default, this function just returns Cil.DoChildren.
The printer function is used by the Cil_printer.pp_extended function. It takes the cur-
rent pretty-printer, the formatter, together with the acsl_extension_kind of the extended
clause. By default, it prints the list of terms or predicates if the kind is Ext_preds l or
Ext_terms l. If the kind is Ext_id i, it only prints the integer i.

                         CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

The short_printer function is a function that can be useful for debugging or user-feedback.
As an alternative to Cil_printer.pp_extended, the Cil_printer.pp_short_extended can
be used to get brief description of the content of the extension. It is for example used by the
GUI to get a more informative name for the extension in the file tree. By default, it does not
print anything about the content of the extension, so that the result is "kwd" or "loop kwd".
When the extension kind is Ext_id, it is common that the plugin defining the extension
contains a table that associates some data to this identifier. In such a case, a printer might
be needed to reconstruct the source code from the data so that a pretty printed code can be
parsed again. For the same reason, an extension that registers a preprocessor that modifies
the AST should probably register a printer to recover the original content.
It is also common, when the kind is Ext_id, to define a particular visitor for the extension,
either to ignore the content of the extension as it is in an internal table of the plugin (thus
returning a SkipChildren action) or, on the opposite, to give the possibility to a user defined
visitor to get an access to this content.
The following code shows a more complete extension example. It provides the user a way
to load some types (assumed to be external to Frama-C) so that they can be used in ACSL
     open Logic_ptree
     open Logic_typing
     open Cil_types

     let preprocessor =
       List .map (fun e → begin match e with
            | { lexpr_node = PLnamed ("load", { lexpr_node = PLvar s; _ }) ; _ } →
              if not (Logic_env.is_logic_type s) then Logic_env.add_typename s
              else Kernel.error "Type already exists %s" s
            | _ → ()
         end ; e)

     module Ts = struct
      let id = ref 0
      let types = Hashtbl.create 5

       let add t = let i = !id in Hashtbl.add types i t ; id ← i + 1 ; i
       let find = Hashtbl.find types

     let typer ctxt loc = function
       | [ { lexpr_node = PLnamed ("load", { lexpr_node = PLvar s; _ }) ; _ } ] →
         let ti = { lt_name = s ; lt_params = [] ; lt_def = None ; lt_attr = []} in
         ctxt.add_logic_type s ti ;
         Ext_id (Ts.add ti)
       | _ →
         ctxt.error loc "Expected type loader"

     let visitor _ _ = Cil.SkipChildren

     let gen_printer s _pp fmt = function
       | Ext_id i →
         Format.fprintf fmt "%s: %s"
           ( if s then "ext_type" else "load") (Ts.find i).lt_name
       | _ → assert false

                                      4.18. LOCATIONS

     let printer = gen_printer false
     let short_printer = gen_printer true

     let () =
       Acsl_extension. register_global
         "ext_type" ∼preprocessor typer     ∼visitor ∼printer ∼short_printer   false

Namely, specification:
     /*@ ext_type load: foo ; */
       axiomatic Pred {
         predicate P(foo f) reads \nothing ;
     /*@ lemma X: \forall foo f ; P(f) ; */

is correctly parsed and typed by Frama-C and leads to the following displayed version in the

4.18     Locations

Prerequisite: None.

In Frama-C, different representations of C locations exist. Section 4.18.1 presents them.
Moreover, maps indexed by locations are also provided. Section 4.18.2 introduces them.

4.18.1    Representations

There are four different representations of C locations. Actually only three are really rel-
evant. All of them are defined in module Locations. They are introduced below. See
the documentation of src/kernel_services/abstract_interp/locations.mli for details
about the provided operations on these types.

                         CHAPTER 4. ADVANCED PLUG-IN DEVELOPMENT

  • Type Location_Bytes.t is used to represent values of C expressions like 2 or ((int)
    &a) + 13. With this representation, there is no way to know the size of a value while
    it is still possible to join two values. Roughly speaking it is represented by a mapping
    between C variables and offsets in bytes.

  • Type location, equivalently Location.t is used to represent the right part of a C
    affectation (including bitfields). It is represented by a Location_Bits.t (see below)
    attached to a size. It is possible to join two locations if and only if they have the same

  • Type Location_Bits.t is similar to Location_Bytes.t with offsets in bits instead of
    bytes. Actually it should only be used inside a location.

  • Type Zone.t is a set of bits (without any specific order). It is possible to join two zones
    even if they have different sizes.

Recommendation 4.3 Roughly speaking, locations and zones have the same purpose. You
should use locations as soon as you have no need to join locations of different sizes. If you
require to convert locations to zones, use the function Locations.enumerate_valid_bits.

As join operators are provided for these types, they can be easily used in abstract interpre-
tation analyses (which can themselves be implemented thanks to one of functors of module

4.18.2    Map Indexed by Locations

Modules Lmap and Lmap_bitwise provide functors implementing maps indexed by locations
and zones (respectively). The argument of these functors have to implement values attached
to indices (resp. locations or zones).
These implementations are quite more complex than simple maps because they automatically
handle overlaps of locations (or zones). So such implementations actually require that the
structures implementing the values attached to indices are at least semi-lattices; see the
corresponding signatures in module Lattice_type. For this purpose, functors of the abstract
interpretation toolbox can help (see in particular module Abstract_interp).

4.19     GUI Extension

Prerequisite: Knowledge of Lablgtk3.

Each plug-in can extend the Frama-C graphical user interface (aka GUI ) in order to
support its own functionalities in the Frama-C viewer. For this purpose, a plug-in
developer has to register a function of type Design.main_window_extension_points
→ unit thanks to Design.register_extension.            The input value of type
Design.main_window_extension_points is an object corresponding to the main win-
dow of the Frama-C GUI. It provides accesses to the main widgets of the Frama-C
GUI and to several plug-in extension points. The documentation of the class type
Design.main_window_extension_points is accessible through the source documentation
(see Section 2.3.8).

                                         4.20. PACKAGING

Besides time-consuming computations have to call the function !Db.progress from time to
time in order to keep the GUI reactive.
The GUI implementation uses Lablgtk3 [10]: you can use any Lablgtk3-compatible code in
your gui extension. A complete example of a GUI extension may be found in the plug-in
Occurrence (see file src/plugins/occurrence/gui/

 Potential issues All the GUI plug-in extensions share the same window and same
 widgets. So conflicts can occur, especially if you specify some attributes on a predefined
 object. For example, if a plug-in wants to highlight a statement s in yellow and another
 one wants to highlight s in red at the same time, the behavior is not specified but it could
 be quite difficult to understand for an user.

4.20       Packaging

If you intend to release your plug-in, a possible way is to take advantage of the opam in-
tegration within dune16 . Basically, the dune-project file (see Section 2.3) should con-
tain a stanza (generate_opam_files true), as well as some meta-information (location
of the sources, licence, author(s), etc.). It is also possible to provide this information in a
file my-plugin-package.opam.template, assuming my-plugin-package is the name of the
package of the plug-in in the dune-project file. See the dune documentation for detailed
information about the creation of the opam file.


                                                                 Appendix A


This chapter summarizes the major changes in this documentation between each Frama-C
release, from newest to oldest.

26.0 Iron

  • Makefiles/Dune: Document the use of dune for compiling and testing plug-in, and
    describe transition from a Makefile-based to a dune-based setup.

  • Journalisation: Journalisation has been removed.

25.0 Manganese

  • Testing: Document new directives (PLUGIN, SCRIPT and LIBS) and new predefined
    macros for ptests.

22.0 Titanium

  • Testing: Document new directives TIMEOUT and NOFRAMAC

21.0 Scandium

  • Configure:    Documentation     of   configure_pkg,   plugin_require_pkg    and
    plugin_use_pkg macros.

20.0 Calcium

  • Testing: Documentation of the new directive MODULE.

                                 APPENDIX A. CHANGES

19.0 Potassium

 • ACSL Extension: Document new status flag for registration functions

 • Testing: Document usage of @@ in a directive

 • Profiling with Landmarks: New section

18.0 Argon

 • Logging Services: Document error and failure behaviors.

 • ACSL Extensions: New extension categories, for global and plain code annotations


 • Logging Services: Introduction of warning categories


 • Tutorial: Update and complete the Hello plug-in section along with making it available

 • Testing: Explain the appropriate way to handle compilation of .ml scripts during tests

 • Makefiles: Remove references to obsolete Makefile.plugin file


 • Makefiles: Update overview of Makefiles.

 • ACSL Extensions: Update documentation after refactoring of ACSL extensions.

 • Machine model: fully new section.


 • ACSL Extensions: Updated documentation for newly introduced loop extensions.


 • Tutorial: Plugin Cfg renamed to ViewCfg; minor fixes.

 • Ptests: Documentation of the new directive EXEC.

 • Ptests: Documentation for sharing directives amongst ptests configurations

 • Makefiles: Documentation for install:: target in dynamic plugins

 • Makefiles: Documentation of exported TARGET_* variables

 • Makefiles: Documentation of new option PLUGIN_EXTRA_DIRS

 • Ptests: New option -gui


 • License Policy: remove this section.

 • Ptests: New configuration directive LOG and new macro PTEST_RESULT

 • File Tree: remove this section, now subsumed by the new Chapter on Software Archi-
   tecture and by the API documentation.

 • File Tree Overview: remove this useless section.

 • Software Architecture: rewrite the whole chapter.

 • No more PLUGIN_HAS_MLI.


 • Type Library: document Datatype.Serializable_undefined.

 • Command Line Options: document Parameter_sig.Kernel_function_set.

 • warn about using Frama-C macros within conditionals

 • Logical Annotations: document ACSL extended clauses mechanism (added sec-
   tion 4.17).

 • Tutorial: fix


 • Reference Manual: update list of main kernel modules.

 • Logical Annotations: document module Property.

 • Command Line Options: update according to kernel changes that split the module
   Plugin into several modules.

 • Architecture, Plug-in Registration and Access and Reference Manual: docu-
   ment registration of a plug-in through a .mli file.

 • Makefiles: introducing Makefile.generic.

 • Testing: MACRO configuration directive.

                                 APPENDIX A. CHANGES


 • Tutorial: fully rewritten.

 • Architecture and Reference Manual: remove references to Cilutil module.


 • Makefile WARN_ERROR_ALL variable.

 • Log: Debug category (˜dkey argument).

 • Visitor: DoChildrenPost action.

 • Testing: document the need for directories to store result and oracles.

 • Project Management System: Fine tuning of AST dependencies.

 • Testing: added PTESTS_OPTS and PLUGIN_PTESTS_OPTS Makefile’s variables.

 • Type: document the type library.

 • Logical Annotations: fully updated.

 • Reference Manual: update kernel files.

 • Testing: merge parts in Advanced Plug-in Development and in Reference Manual.

 • Website: refer to CEA internal documentation.

 • Command Line Options: explain how to modify the default behavior of an option.

 • Command Line Options: fully updated.

 • Project Management System: fully updated.

 • Plug-in Registration and Access: Type replaced by Datatype and document labeled
   argument journalize.

 • updated.

 • Plug-in General Services: updated.

 • Software Architecture: Type is now a library, not just a single module.


 • Tutorial of the Future: new chapter for preparing a future tutorial.

 • Types as first class values: links to articles.

 • Tutorial: kernel-integrated plug-ins are now deprecated.

 • Visitors: example is now out-of-date.




  • Visitors: update example to new kernel API.

  • Documentation: external plugin API documentation.

  • Visitors: fix bug (replace DoChildrenPost by ChangeDoChildrenPost), change se-
    mantics wrt vstmt_aux.


  • Very Important Preliminary Warning: adding this very important chapter.

  • Tutorial: fix bug in the ‘Hello World’ example.

  • Testing: updated semantics of CMD and STDOPT directives.

  • Initialization Steps: updated according to new options -then and -then-on and to
    the new ‘Files Setting’ stage.

  • Visitors: example updated

We list changes of previous releases below.


  • updated

  • Tutorial: the section about kernel-integrated plug-in is out-of-date

  • Project: no more rehash in datatypes

  • Initialisation Steps: fixed according to the current implementation

  • Plug-in Registration and Access: updated according to API changes

  • Documentation: updated and improved

  • Introduction: is aware of the Frama-C user manual

  • Logical Annotations: fully new section

  • Tutorial: fix an efficiency issue with the Makefile of the Hello plug-in


  • Makefiles: update according to the new Makefile.kernel

                                  APPENDIX A. CHANGES


 • Makefiles: update according to the new makefiles hierarchy

 • Writing messages: fully documented

 • Initialization Steps: the different stages are more precisely defined. The implementa-
   tion has been modified to take into account specificities of dynamically linked plug-ins

 • Project Management System: mention value descr in Datatype

 • Makefile.plugin: add documentation for additional parameters


 • Initialization Steps: update according to the new implementation

 • Command Line Options: update according to the new implementation

 • Plug-in General Services: fully new section introducing the new module Plugin

 • File Tree: update according to changes in the kernel

 • Makefiles: update according to the new file Makefile.dynamic and the new file

 • Architecture: update according to the recent implementation changes

 • Tutorial: update according to API changes and the new way of writing plug-ins

 • update according to changes in the way of adding a simple plug-in

 • Plug-in Registration and Access: update according to the new API of module Type


 • Changes: fully new appendix

 • Command Line Options: new sub-section Storing New Dynamic Option Values

 • compliant with new implementations of configure_library and

 • Exporting Datatypes: now embedded in new section Plug-in Registration and Access

 • GUI: update, in particular the full example has been removed

 • Introduction: improved

 • Plug-in Registration and Access: fully new section

 • Project: compliant with the new interface

 • Reference Manual: integration of dynamic plug-ins

 • Software architecture: integration of dynamic plug-ins

 • Tutorial: improve part about dynamic plug-ins

 • Tutorial: use Db.Main.extend to register an entry point of a plug-in.

 • Website: better highlighting of the directory containing the html pages


 • GUI: fully updated

 • Testing: new sub-section Alternative testing

 • Testing: new directive STDOPT

 • Tutorial: new section Dynamic plug-ins

 • Visitor: ChangeToPost in sub-section Action Performed


 • GUI: fully updated

 • Makefile: additional variables of Makefile.plugin

 • Project: new important note about registration of internal states in Sub-section In-
   ternal State: Principle

 • Testing: more precise documentation in the reference manual


 • Documentation: new sub-section Website

 • Documentation: new ocamldoc tag @plugin developer guide

 • Index: fully new

 • Project: new sub-section Internal State: Principle

 • Reference manual: largely extended

 • Software architecture: fully new chapter


 • First public release



 [1] Patrick Baudin, Jean-Christophe Filliâtre, Thierry Hubert, Claude Marché, Benjamin
     Monate, Yannick Moy, and Virgile Prevosto. ACSL: ANSI C Specification Language.
     Version 1.8, March 2014.

 [2] Patrick Baudin and Anne Pacalet. Slicing plug-in.

 [3] Loïc Correnson, Pascal Cuoq, Florent Kirchner, Armand Puccetti, Virgile Prevosto,
     Julien Signoles, and Boris Yakobowski. Frama-C User Manual, February 2015. http:

 [4] Loïc Correnson, Zaynah Dargaye, and Anne Pacalet. Frama-C’s WP plug-in, February

 [5] Loïc Correnson and Julien Signoles. Combining Analysis for C Program Verification. In
     Formal Methods for Industrial Critical Systems (FMICS), August 2012.

 [6] Pascal Cuoq, Damien Doligez, and Julien Signoles. Lightweight Typed Customizable
     Unmarshaling. ML Workshop’11, September 2011.

 [7] Pascal Cuoq, Florent Kirchner, Nikolai Kosmatov, Virgile Prevosto, Julien Signoles, and
     Boris Yakobowski. Frama-C, A Program Analysis Perspective. In the 10th International
     Conference on Software Engineering and Formal Methods (SEFM 2012), volume 7504
     of LNCS, pages 233–247. Springer, 2012.

 [8] Pascal Cuoq and Julien Signoles. Experience Report: OCaml for an industrial-strength
     static analysis framework. In Proceedings of International Conference of Functional
     Programming (ICFP’09), pages 281–286, New York, NY, USA, September 2009. ACM

 [9] Pascal Cuoq, Boris Yakobowski, and Virgile Prevosto. Frama-C’s value analysis plug-in,
     February 2015.

[10] Jacques Garrigue, Benjamin Monate, Olivier Andrieu, and Jun Furuse. LablGTK2.

[11] Philippe Hermann and Julien Signoles.  Frama-C’s RTE plug-in, April 2013.

[12] Florent Kirchner, Nikolai Kosmatov, Virgile Prevosto, Julien Signoles, and Boris
     Yakobowski. Frama-c: A software analysis perspective. Formal Aspects of Computing,
     pages 1–37, 2015. Extended version of [7].


[13] Xavier Leroy, Damien Doligez, Jacques Garrigue, Didier Rémy, and Jérôme Vouillon.
     The Objective Caml system.

[14] Donald Michie. Memo functions: a language feature with "rote-learning" properties.
     Research Memorandum MIP-R-29, Department of Machine Intelligence & Perception,
     Edinburgh, 1967.

[15] Donald Michie. Memo functions and machine learning. Nature, 218:19–22, 1968.

[16] George C. Necula, Scott McPeak, Shree Prakash Rahul, and Westley Weimer. CIL:
     Intermediate Language and Tools for Analysis and Transformation of C Programs. In
     CC ’02: Proceedings of the 11th International Conference on Compiler Construction,
     pages 213–228, London, UK, 2002. Springer-Verlag.

[17] Julien Signoles. Foncteurs impératifs et composés: la notion de projet dans Frama-C. In
     Hermann, editor, JFLA 09, Actes des vingtièmes Journées Francophones des Langages
     Applicatifs, volume 7.2 of Studia Informatica Universalis, pages 245–280, 2009. In French.

[18] Julien Signoles. Une bibliothèque de typage dynamique en OCaml. In Hermann, editor,
     JFLA 11, Actes des vingt-deuxièmes Journées Francophones des Langages Applicatifs,
     Studia Informatica Universalis, pages 209–242, January 2011. In French.

[19] Nicolas Stouls and Virgile Prevosto.  Frama-C’s Aoraï plug-in, April 2013.

                                      LIST OF FIGURES

                                                                List of Figures

2.1   Plug-in Integration Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . .     14
2.2   Control flow graph for file test.c. . . . . . . . . . . . . . . . . . . . . . . . . .   31
2.3   Control flow graph colored with reachability information. . . . . . . . . . . .         34
2.4   Mini-GUI with Bogue for testing our plug-in. . . . . . . . . . . . . . . . . . .        37

3.1   Frama-C Architecture Design. . . . . . . . . . . . . . . . . . . . . . . . . . . .      42

4.1   Representation of the Frama-C State. . . . . . . . . . . . . . . . . . . . . . . .      76
4.2   Interaction between the project library and your registered global data. . . .          77
4.3   Indices of AST nodes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100



Abstract Interpretation, 44, 108                vexpr, 101
Abstract_interp, 108                            vfile, 29
Acsl_extension                                  vglob, 98
    register_behavior, 104                      vlogic_ctor_info_decl, 98
    register_code_annot, 104                    vlogic_ctor_info_use, 98
    register_code_annot_next_both, 104          vlogic_info_decl, 98
    register_code_annot_next_loop, 104          vlogic_info_use, 98
    register_code_annot_next_stmt, 104          vlogic_type_info_decl, 98
    register_global, 104                        vlogic_type_info_use, 98
    register_global_block, 104                  vlogic_var_decl, 98
Analysis                                        vlogic_var_use, 98
    compute, 77                                 voffs, 98
    is_computed, 77                             vstmt, 98
Annotation, 98, 102                             vvdec, 98
Annotations, 43, 102                            vvrbl, 98
    add_assert, 101                           dummyStmt, 74
Architecture, 41                              lzero, 101
    Plug-in, 14                               visitAction, 98
AST, 76, 98, 102                                ChangeDoChildrenPost, 99–101
    Copying, 99, 101                            ChangeTo, 99–101
    Modification, 45, 82, 98–100                ChangeToPost, 99
    Sharing, see Sharing                        DoChildren, 30, 34, 99, 101
Ast                                             DoChildrenPost, 29, 30, 99
    add_monotonic_state, 80                     JustCopy, 30, 99, 100
    get, 33, 76                                 JustCopyPost, 99
    mark_as_changed, 80                         SkipChildren, 30, 99–101
    mark_as_grown, 80                         visitCilAstT ype, 98
    self, 37, 82, 101                         visitCilFile, 98
                                              visitCilFileCopy, 98
Boot, 87                                      visitCilFileSameGlobals, 98
                                           Cil_datatype, 68
Cabs, 44                                      Fundec, 37
    file, 89                                  Stmt, 68, 74, 75, 78
Cabs2cil                                      Varinfo, 78
    convFile, 89                           Cil_state_builder, 78, 79
Cil, 98                                       Stmt_hashtbl, 78
    cilVisitor, 98, 98                     Cil_types, 43
      behavior, 101                           acsl_extension, 104
      current_kinstr, 101                     acsl_extension_kind, 104
      fill_global_tables, 99                  behavior, 103
      get_filling_actions, 99, 101            binop


     Div, 101                                  run_after_setting_files, 89
     Mod, 101                                  run_during_extending_stage, 87
   code_annotation_node                        stage
     AExtended, 103                               Configuring, 88
   compinfo, 100                                  Early, 87
   enuminfo, 100                                  Exiting, 88
   exp_node                                       Extended, 88
     BinOp, 101                                   Extending, 87
   ext_category, 103                              Loading, 88
   ext_code_annot_context, 103              Command Line, 18, 32
   fieldinfo, 100                              -machdep, 91
   file, 89, 98, 99, 101                       -ocode, 67
   global, 98                                  Option, 61, 84, 84
     GFun, 30                                  Parsing, 87
   global_annotation                        Consistency, 45, 76, 77, 84, 98, 100
     Dextended, 103                         Context Switch, 81, 83
   logic_ctor_info, 98
                                            Dataflow2, 108
   logic_info, 98, 100
                                            Datatype, 68, 79, 81
   logic_type_info, 98
                                               Library, 67
   logic_var, 98, 100
                                            Datatype, 67, 68
   mach, 90
                                               Bool, 39
   offset, 98
                                               bool, 68
                                               char, 68
     Rneq, 101
                                               func, 73, 75
   stmt, 100                                   func2, 68
   stmtkind                                    func3, 75
     Block, 29                                 Function, 71
     Break, 29                                 identity, 68
     Continue, 29                              Int, 70
     Goto, 29                                  int, 67, 68
     If, 29                                    List, 70, 71
     Instr, 29                                 list, 68
     Loop, 29                                  Make, 68–70
     Return, 29                                never_any_project, 68
     Switch, 29                                Pair, 78
     TryExcept, 29                             Polymorphic, 70
     TryFinally, 29                            Polymorphic2, 70
     UnspecifiedSequence, 29                   Polymorphic3, 70
   typeinfo, 100                               Polymorphic4, 70
   varinfo, 78, 79, 98–100                     Ref, 81
Cmdline, 87                                    S, 68, 81
   Exit, 88                                    S_no_copy
   is_going_to_load, 88                          equal, 68
   nop, 88                                       pretty, 68, 74
   run_after_configuring_stage, 88             S_with_collections, 68
   run_after_early_stage, 87                     Hashtbl, 70, 78
   run_after_exiting_stage, 88                   Set, 68
   run_after_extended_stage, 79, 80, 88        Serializable_undefined, 70, 74
   run_after_loading_stage, 88                 String, 37, 68, 70


    string, 67, 68                                  init_from_cmdline, 98
    Ty                                              init_project_from_cil_file, 82, 98
      t, 40, 74, 75, 78, 84                         init_project_from_visitor, 82, 98
      ty, 74, 75                                    must_recompute_cfg, 89
    Undefined, 69                                   new_file_type, 89
    undefined, 69                                   new_machdep, 90
    unit, 73, 75                                 From, 79, 80
Db, 43, 72, 72, 73                               From_parameters
    From.self, 79, 80                               ForceCallDeps, 85
    Impact.compute_pragmas, 72                   Frontc
    Main, 14                                        add_syntactic_transformation, 89
      extend, 14, 16–18, 21, 25, 28, 61, 87,
         89, 101                                 Globals, 43
    progress, 109                                   Functions
    Value                                             find_by_name, 36
      compute, 78, 82                               set_entry_point, 77
      is_computed, 82                            GUI, 14, 108
      self, 78, 80, 83
                                                 Hashtable, 78, 79
Design, 14
                                                 Hello, 45
    main_window_extension_points, 108
                                                 Highlighting, 109
    register_extension, 108
                                                 Hook, 14
dune-project, 109
Dynamic, 14, 43, 73                              Initialization, 73, 86, 87
    get, 73, 75
    Parameter, 86                                Kernel, 41, 80
      Bool, 86                                      Internals, 44
    register, 73, 73, 74                            Services, 43
                                                 Kernel, 84
Emitter, 84                                         CodeOutput, 67
Emitter                                             SafeArrays, 86
    create, 102                                     Unicode, 85
Entry Point, 77                                  Kernel_function, 43, 74, 75, 78
Entry point, 14                                     dummy, 74
Equality                                            get_definition, 36
    Physical, 81                                    Make_Table, 80
    Structural, 81                               Kind, 79
    Analysis                                     Lablgtk, 109
      compute, 77                                Lattice, 108
      is_computed, 34, 40, 77                    Lattice_type, 108
      self, 37                                   Linking, 87
    Results                                      Lmap, 108
      is_reachable, 34                           Lmap_bitwise, 108
                                                 Loading, 77, 82, 88
FCHashtbl, 43                                    Location, 107
File                                             Locations, 107
    add_code_transformation_after_cleanup,           enumerate_valid_bits, 108
    add_code_transformation_before_cleanup,          Location, 108
    create_project_from_visitor, 101                 location, 108
    init_from_c_files, 98                            Location_Bits, 108


      Location_Bytes, 108                          Bool, 84, 85
      Zone, 108                                    Builder, 84
Log                                                  Empty_string, 84
   add_listener, 65                                  False, 84, 85
   log_channel, 66                                   Int, 84
   Messages, 61, 62                                  Kernel_function_set, 85, 85
      abort, 63                                      String, 84
      debug, 63                                      String_set, 84
      error, 63                                      True, 84
      failure, 63                                    Zero, 84
      fatal, 63                                    Int, 84
      feedback, 63                                 Kernel_function_set, 85
      log, 65                                      S, 84
      logwith, 66                              Parameter_state
      register_warn_category, 64                   get_selection, 84
      result, 62                               Parameters, 84
      set_warn_status, 64                      Pdg, 80
      verify, 63                               Plug-in, 13, 43
      warn_category, 64                            Access, 73
      warning, 63                                  API, 73
   new_channel, 66
                                                   Architecture, 14
   print_delayed, 67
                                                   Basic, 15
   print_on_output, 67
                                                   Command Line Options, 32
   set_echo, 65
                                                   Command-Line Options, 18
   set_output, 67
                                                   Documentation, 26
Logging, see Messages
                                                   GUI, 14, 87, 108
Logic_const, 103
                                                   Initialization, see Initialization
   new_acsl_extension, 104
                                                   Kernel-integrated, 43
   prel, 101
                                                   Messages, 17
Logic_parse_string, 103
Logic_to_c, 103                                    Pdg, see Pdg
Logic_typing                                       Registration, 17, 73
   typing_context, 104                             Simple, 16
Logic_utils, 103                                   Testing, 22
   expr_to_term, 101                               Types, 72
                                               plugin_types, 72
Machine model, 90                              Plugin, 14, 60
Makefile, 47                                       Register, 17, 18, 21, 27, 32, 43, 60, 61,
Marshaling, 68                                          74, 84
memo, 78                                       Pretty_utils, 43
Memoization, 76, 78, 79                        Printer_api
Messages, 61                                       S.pp_exp, 29
Module Initialization, see Initialization          S.pp_instr, 29
                                                   S.pp_stmt, 28
Occurrence, 109
                                                   S.pp_varinfo, 30
Oracle, 48
                                               Project, 37, 45, 68, 76, 98, 99
Parameter, 76                                      Current, 76, 76, 81, 82, 84, 99
Parameter_customize, 86                            Initial, 98
    set_negative_option_name, 86                   Use, 82
Parameter_sig                                  Project, 14, 40, 82


    clear, 40, 40, 82, 83                    structure
    current, 76, 82                            Sum, 68, 70
    IOError, 82                              t
    load, 82                                   Structure, 68, 70
    on, 83, 83, 84
    save, 82                            Test, 22, 48
    set_current, 82, 82, 83                 Configuration, 23
Project_skeleton                            Directive, 23, 53
    t, 82                                      CMD, 53, 54
Property, 102                                  COMMENT, 53
Property_status, 102                           DEPS, 53, 56
Ptests, 22, 48                                 DONTRUN, 53
ptests_config, 50                              EXECNOW, 53, 55
                                               EXIT, 53
Saving, 45, 77, 78, 82                         FILEREG, 53, 55
Selection, 77, 83                              FILTER, 53, 56
self, 79                                       LIBS, 53, 55
Session, 82                                    LOG, 53
Sharing, 99, 100                               MACRO, 53, 55
    Widget, 109                                MODULE, 53, 55
Side-Effect, 81, 87                            NOFRAMAC, 53
State, 76, 83, 84, 98                          OPT, 23, 53, 54
    Cleaning, 81, 83                           PLUGIN, 54
    Dependency, 77, 79, 81, 83, 84             STDOPT, 54, 54
       Postponed, 79, 88                       TIMEOUT, 54
    Functionalities, 76                     Header, 23, 50
    Global Version, 81                      Suite, 50
    Kind, see Kind                      test_config, 50, 55
    Local Version, 81, 81               Type
    Name, 79, 81                            Dynamic, 67
    Registration, 76, 78                    Value, 67, 73, 74
    Selection, see Selection            Type, 14
    Sharing, 81                             Abstract, 74, 75
State, 79                                   AlreadyExists, 73
    dummy, 79                               name, 70
State_builder, 78, 79                       par, 68, 70
    Hashtbl, 37                             precedence
    Ref, 39, 81                                Basic, 68
    Register, 78, 79, 80, 81                   Call, 68
State_dependency_graph                      t, 67, 73
    S.add_codependencies, 80            Typed_parameter, 84
State_selection, 83
    only_dependencies, 82               Visitor, 28, 98
    S                                       Behavior, 99, 100
       with_dependencies, 40                Cil, 98
    t, 40                                     Entry Point, 98
    with_dependencies, 83                   Copy, 82, 99, 99, 100
Structural_descr                            In-Place, 99, 99
    p_int, 68, 70                       Visitor
    pack, 70                                frama_c_inplace, 29


     current_kf, 101
     vglob_aux, 30, 98
     vstmt_aux, 30, 34, 98
   generic_frama_c_visitor, 98, 101
   visitFramacFileSameGlobals, 33
   visitFramacFunction, 36, 38
   copy, 99, 101
   Get, 100
     kernel_function, 101
     stmt, 101
   Get_orig, 100
   inplace, 99
   Memo, 100
   Reset, 100
   Set, 100
   Set_orig, 100
   t, 99