NAME

ld.lld — ELF linker from the LLVM project

SYNOPSIS

DESCRIPTION

A linker takes one or more object, archive, and library files, and combines them into an output file (an executable, a shared library, or another object file). It relocates code and data from the input files and resolves symbol references between them.

ld.lld is a drop-in replacement for the GNU BFD and gold linkers. It accepts most of the same command line arguments and linker scripts as GNU linkers.

ld.lld currently supports i386, x86-64, ARM, AArch64, PowerPC32, PowerPC64, MIPS32, MIPS64, RISC-V, AMDGPU, Hexagon and SPARC V9 targets. ld.lld acts as a Microsoft link.exe-compatible linker if invoked as lld-link and as macOS's ld if invoked as ld.ld64. All these targets are always supported however ld.lld was built, so you can always use ld.lld as a native linker as well as a cross linker.

OPTIONS

Many options have both a single-letter and long form. When using the long form options other than those beginning with the letter o may be specified using either one or two dashes preceding the option name. Long options beginning with o require two dashes to avoid confusion with the -o path option.

--allow-multiple-definition

Do not error if a symbol is defined multiple times. The first definition will be used.

--allow-shlib-undefined

Allow unresolved references in shared libraries. This option is enabled by default when linking a shared library.

--apply-dynamic-relocs

Apply link-time values for dynamic relocations.

--as-needed

Only set DT_NEEDED for shared libraries if used.

--auxiliary=value

Set the DT_AUXILIARY field to the specified name.

--Bdynamic, --dy

Link against shared libraries.

--Bstatic, --static, --dn

Do not link against shared libraries.

-Bno-symbolic

Don't bind default visibility defined symbols locally for -shared (default).

-Bsymbolic

Bind default visibility defined symbols locally for -shared. Also set the DF_SYMBOLIC flag.

-Bsymbolic-functions

Bind default visibility defined function symbols locally for -shared.

-Bsymbolic-non-weak-functions

Bind default visibility defined STB_GLOBAL function symbols locally for -shared.

--build-id=value

Generate a build ID note. value may be one of fast, md5, sha1, tree, uuid, 0xhex-string, and none. tree is an alias for sha1. Build-IDs of type fast, md5, sha1, and tree are calculated from the object contents. fast is not intended to be cryptographically secure.

--build-id

Synonym for --build-id=fast.

--color-diagnostics=value

Use colors in diagnostics. value may be one of always, auto, and never. auto enables color if and only if output is to a terminal.

--color-diagnostics

Alias for --color-diagnostics=auto.

--compress-debug-sections=value

Compress DWARF debug sections. value may be none or zlib. The default compression level is 1 (fastest) as the debug info usually compresses well at that level, but if you want to compress it more, you can specify -O2 to set the compression level to 6.

--cref

Output cross reference table. If -Map is specified, print to the map file.

--defsym=symbol=expression

Define a symbol alias. expression may be another symbol or a linker script expression. For example, ‘--defsym=foo=bar’ or ‘--defsym=foo=bar+0x100’.

--demangle

Demangle symbol names.

--disable-new-dtags

Disable new dynamic tags.

--discard-all, -x

Delete all local symbols.

--discard-locals, -X

Delete temporary local symbols.

--discard-none

Keep all symbols in the symbol table.

--dynamic-linker=value

Specify the dynamic linker to be used for a dynamically linked executable. This is recorded in an ELF segment of type PT_INTERP.

--dynamic-list=file

Similar to --export-dynamic-symbol-list. When creating a shared object, implies -Bsymbolic but does not set DF_SYMBOLIC

--EB

Select the big-endian format in the OUTPUT_FORMAT command.

--EL

Select the little-endian format in the OUTPUT_FORMAT command.

--eh-frame-hdr

Request creation of .eh_frame_hdr section and PT_GNU_EH_FRAME segment header.

--emit-relocs, -q

Generate relocations in the output.

--enable-new-dtags

Enable new dynamic tags.

--end-lib

End a grouping of objects that should be treated as if they were together in an archive.

--entry=entry

Name of entry point symbol.

--error-limit=value

Maximum number of errors to emit before stopping. A value of zero indicates that there is no limit.

--error-unresolved-symbols

Report unresolved symbols as errors.

--error-handing-script=script_path

Call script script_path upon some error, with tag as first argument, and an extra parameter as second argument. The script is expected to return 0 on success. Any other value is considered a generic error. tag may be missing-lib followed by the name of the missing library. undefined-symbol followed by the name of the undefined symbol.

--execute-only

Mark executable sections unreadable. This option is currently only supported on AArch64.

--exclude-libs=value

Exclude static libraries from automatic export.

--export-dynamic, -E

Put symbols in the dynamic symbol table.

--export-dynamic-symbol=glob

(executable) Put matched non-local defined symbols to the dynamic symbol table. (shared object) References to matched non-local STV_DEFAULT symbols shouldn't be bound to definitions within the shared object even if they would otherwise be due to -Bsymbolic , -Bsymbolic-functions or --dynamic-list

--export-dynamic-symbol-list=file

Read a list of dynamic symbol patterns from file. Apply --export-dynamic-symbol on each pattern.

--fatal-warnings

Treat warnings as errors.

--filter=value, -F value

Set the DT_FILTER field to the specified value.

--fini=symbol

Specify a finalizer function.

--format=input-format, -b input-format

Specify the format of the inputs following this option. input-format may be one of binary, elf, and default. default is a synonym for elf.

--gc-sections

Enable garbage collection of unused sections.

--gdb-index

Generate .gdb_index section.

--hash-style=value

Specify hash style. value may be sysv, gnu, or both. both is the default.

--help

Print a help message.

--icf=all

Enable identical code folding.

--icf=safe

Enable safe identical code folding.

--icf=none

Disable identical code folding.

--ignore-data-address-equality

Ignore address equality of data. C/C++ requires each data to have a unique address. This option allows lld to do unsafe optimization that breaks the requirement: create copies of read-only data or merge two or more read-only data that happen to have the same value.

--ignore-function-address-equality

Ignore address equality of functions. This option allows non-PIC calls to a function with non-default visibility in a shared object. The function may have different addresses within the executable and within the shared object.

--image-base=value

Set the base address to value.

--init=symbol

Specify an initializer function.

--keep-unique=symbol

Do not fold symbol during ICF.

-l libName, --library=libName

Root name of library to use.

-L dir, --library-path=dir

Add a directory to the library search path.

--lto-aa-pipeline=value

AA pipeline to run during LTO. Used in conjunction with --lto-newpm-passes.

--lto-newpm-passes=value

Passes to run during LTO.

--lto-Oopt-level

Optimization level for LTO.

--lto-partitions=value

Number of LTO codegen partitions.

-m value

Set target emulation.

--Map=file, -M file

Print a link map to file.

--nmagic, -n

Do not page align sections, link against static libraries.

--no-allow-shlib-undefined

Do not allow unresolved references in shared libraries. This option is enabled by default when linking an executable.

--no-as-needed

Always set DT_NEEDED for shared libraries.

--no-color-diagnostics

Do not use colors in diagnostics.

--no-demangle

Do not demangle symbol names.

--no-dynamic-linker

Inhibit output of an .interp section.

--no-fortran-common

Do not search archive members for definitions to override COMMON symbols.

--no-gc-sections

Disable garbage collection of unused sections.

--no-gnu-unique

Disable STB_GNU_UNIQUE symbol binding.

--no-merge-exidx-entries

Disable merging .ARM.exidx entries.

--no-nmagic

Page align sections.

--no-omagic

Do not set the text data sections to be writable, page align sections.

--no-relax

Disable target-specific relaxations. For x86-64 this disables R_X86_64_GOTPCRELX and R_X86_64_REX_GOTPCRELX GOT optimization.

--no-rosegment

Do not put read-only non-executable sections in their own segment.

--no-undefined-version

Report version scripts that refer undefined symbols.

--no-undefined

Report unresolved symbols even if the linker is creating a shared library.

--no-warn-symbol-ordering

Do not warn about problems with the symbol ordering file or call graph profile.

--no-whole-archive

Restores the default behavior of loading archive members.

--no-pie, --no-pic-executable

Do not create a position independent executable.

--noinhibit-exec

Retain the executable output file whenever it is still usable.

--nostdlib

Only search directories specified on the command line.

-o path

Write the output executable, library, or object to path. If not specified, a.out is used as a default.

-Ovalue

Optimize output file size. value may be:

0

Disable string merging.

1

Enable string merging.

2

Enable string tail merging. If --compress-debug-sections is given, compress debug sections at compression level 6 instead of 1.

-O1 is the default.

--oformat=format

Specify the format for the output object file. The only supported format is binary, which produces output with no ELF header.

--omagic, -N

Set the text and data sections to be readable and writable, do not page align sections, link against static libraries.

--opt-remarks-filename file

Write optimization remarks in YAML format to file.

--opt-remarks-passes pass-regex

Filter optimization remarks by only allowing the passes matching pass-regex.

--opt-remarks-with-hotness

Include hotness information in the optimization remarks file.

--orphan-handling=mode

Control how orphan sections are handled. An orphan section is one not specifically mentioned in a linker script. mode may be:

place

Place orphan sections in suitable output sections.

warn

Place orphan sections as for place and also report a warning.

error

Place orphan sections as for place and also report an error.

place is the default.

--pack-dyn-relocs=format

Pack dynamic relocations in the given format. format may be:

none

Do not pack. Dynamic relocations are encoded in SHT_REL(A).

android

Pack dynamic relocations in SHT_ANDROID_REL(A).

relr

Pack relative relocations in SHT_RELR, and the rest of dynamic relocations in SHT_REL(A).

android+relr

Pack relative relocations in SHT_RELR, and the rest of dynamic relocations in SHT_ANDROID_REL(A).

none is the default. If --use-android-relr-tags is specified, use SHT_ANDROID_RELR instead of SHT_RELR.

--pic-veneer

Always generate position independent thunks.

--pie, --pic-executable

Create a position independent executable.

--power10-stubs=mode

Whether to use Power10 instructions in call stubs for R_PPC64_REL24_NOTOC and TOC/NOTOC interworking. mode may be:

yes

(default) Use.

auto

Currently the same as yes.

no

Don't use.

--print-gc-sections

List removed unused sections.

--print-icf-sections

List identical folded sections.

--print-map

Print a link map to the standard output.

--print-archive-stats=file

Write archive usage statistics to the specified file. Print the numbers of members and fetched members for each archive.

--push-state

Save the current state of --as-needed, --static, and --whole-archive.

--pop-state

Restore the states saved by --push-state.

--relocatable, -r

Create relocatable object file.

--reproduce=path

Write a tar file to path, containing all the input files needed to reproduce the link, a text file called response.txt containing the command line options and a text file called version.txt containing the output of ld.lld --version. The archive when unpacked can be used to re-run the linker with the same options and input files.

--retain-symbols-file=file

Retain only the symbols listed in the file.

--rpath=value, -R value

Add a DT_RUNPATH to the output.

--rsp-quoting=value

Quoting style for response files. The supported values are windows and posix.

--script=file, -T file

Read linker script from file. If multiple linker scripts are given, they are processed as if they were concatenated in the order they appeared on the command line.

--section-start=section=address

Set address of section.

--shared, --Bsharable

Build a shared object.

--shuffle-sections=seed

Shuffle matched sections using the given seed before mapping them to the output sections. If -1, reverse the section order. If 0, use a random seed.

--soname=value, -h value

Set DT_SONAME to value.

--sort-common

This option is ignored for GNU compatibility.

--sort-section=value

Specifies sections sorting rule when linkerscript is used.

--start-lib

Start a grouping of objects that should be treated as if they were together in an archive.

--strip-all, -s

Strip all symbols. Implies --strip-debug.

--strip-debug, -S

Strip debugging information.

--symbol-ordering-file=file

Lay out sections in the order specified by file.

--sysroot=value

Set the system root.

--target1-abs

Interpret R_ARM_TARGET1 as R_ARM_ABS32.

--target1-rel

Interpret R_ARM_TARGET1 as R_ARM_REL32.

--target2=type

Interpret R_ARM_TARGET2 as type, where type is one of rel, abs, or got-rel.

--Tbss=value

Same as --section-start with .bss as the sectionname.

--Tdata=value

Same as --section-start with .data as the sectionname.

--Ttext=value

Same as --section-start with .text as the sectionname.

--thinlto-cache-dir=value

Path to ThinLTO cached object file directory.

--thinlto-cache-policy=value

Pruning policy for the ThinLTO cache.

--thinlto-jobs=value

Number of ThinLTO jobs.

--threads=N

Number of threads. all (default) means all of concurrent threads supported. 1 disables multi-threading.

--time-trace

Record time trace.

--time-trace-file=file

Write time trace output to file.

--time-trace-granularity=value

Minimum time granularity (in microseconds) traced by time profiler.

--trace

Print the names of the input files.

--trace-symbol=symbol, -y symbol

Trace references to symbol.

--undefined=symbol, -u symbol

If symbol is not defined after symbol resolution, and there's a static library that contains an object file defining the symbol, load the member to include the object file in the output file.

--undefined-glob=pattern

Synonym for --undefined, except that it takes a glob pattern. In a glob pattern, * matches zero or more characters, ? matches any single character, and [...] matches the characters within brackets. All symbols that match a given pattern are handled as if they were given as arguments of --undefined.

--unique

Creates a separate output section for every orphan input section.

--unresolved-symbols=value

Determine how to handle unresolved symbols.

--use-android-relr-tags

Use SHT_ANDROID_RELR / DT_ANDROID_RELR* tags instead of SHT_RELR / DT_RELR*.

-v

Display the version number and proceed with linking if object files are specified.

-V, --version

Display the version number and exit.

--verbose

Verbose mode.

--version-script=file

Read version script from file.

--warn-backrefs

Warn about reverse or cyclic dependencies to or between static archives. This can be used to ensure linker invocation remains compatible with traditional Unix-like linkers.

--warn-backrefs-exclude=glob

Glob describing an archive (or an object file within --start-lib) which should be ignored for --warn-backrefs

--warn-common

Warn about duplicate common symbols.

--warn-ifunc-textrel

Warn about using ifunc symbols in conjunction with text relocations. Older versions of glibc library (2.28 and earlier) has a bug that causes the segment that includes ifunc symbols to be marked as not executable when they are relocated. As a result, although the program compiles and links successfully, it gives segmentation fault when the instruction pointer reaches an ifunc symbol. Use -warn-ifunc-textrel to let lld give a warning, if the code may include ifunc symbols, may do text relocations and be linked with an older glibc version. Otherwise, there is no need to use it, as the default value does not give a warning. This flag has been introduced in late 2018, has no counter part in ld and gold linkers, and may be removed in the future.

--warn-unresolved-symbols

Report unresolved symbols as warnings.

--whole-archive

Force load of all members in a static library.

--why-extract=file

Print to a file about why archive members are extracted.

--wrap=symbol

Redirect symbol references to __wrap_symbol and __real_symbol references to symbol.

-z option

Linker option extensions.

dead-reloc-in-nonalloc=section_glob=value

Resolve a relocation in a matched non-SHF_ALLOC section referencing a discarded symbol to value Accepts globs, in the event of a section matching more than one option, the last option takes precedence. An order of least specific to most specific match is recommended.

execstack

Make the main stack executable. Stack permissions are recorded in the PT_GNU_STACK segment.

bti-report=[none|warning|error]

Specify how to report the missing GNU_PROPERTY_AARCH64_FEATURE_1_BTI property. none is the default, linker will not report the missing property otherwise will be reported as a warning or an error.

cet-report=[none|warning|error]

Specify how to report the missing GNU_PROPERTY_X86_FEATURE_1_IBT or GNU_PROPERTY_X86_FEATURE_1_SHSTK properties. none is the default, linker will not report the missing property otherwise will be reported as a warning or an error.

force-bti

Force enable AArch64 BTI instruction in PLT, warn if Input ELF file does not have GNU_PROPERTY_AARCH64_FEATURE_1_BTI property.

force-ibt

Force enable Intel Indirect Branch Tracking in PLT, warn if an input ELF file does not have GNU_PROPERTY_X86_FEATURE_1_IBT property.

global

Sets the DF_1_GLOBAL flag in the DYNAMIC section. Different loaders can decide how to handle this flag on their own.

ifunc-noplt

Do not emit PLT entries for ifunc symbols. Instead, emit text relocations referencing the resolver. This is an experimental optimization and only suitable for standalone environments where text relocations do not have the usual drawbacks. This option must be combined with the -z notext option.

initfirst

Sets the DF_1_INITFIRST flag to indicate the module should be initialized first.

interpose

Set the DF_1_INTERPOSE flag to indicate to the runtime linker that the object is an interposer. During symbol resolution interposers are searched after the application but before other dependencies.

muldefs

Do not error if a symbol is defined multiple times. The first definition will be used. This is a synonym for --allow-multiple-definition.

nocombreloc

Disable combining and sorting multiple relocation sections.

nocopyreloc

Disable the creation of copy relocations.

nodefaultlib

Set the DF_1_NODEFLIB flag to indicate that default library search paths should be ignored.

nodelete

Set the DF_1_NODELETE flag to indicate that the object cannot be unloaded from a process.

nodlopen

Set the DF_1_NOOPEN flag to indicate that the object may not be opened by dlopen(3).

nognustack

Do not emit the PT_GNU_STACK segment.

norelro

Do not indicate that portions of the object should be mapped read-only after initial relocation processing. The object will omit the PT_GNU_RELRO segment.

notext

Allow relocations against read-only segments. Sets the DT_TEXTREL flag in the DYNAMIC section.

now

Set the DF_BIND_NOW flag to indicate that the run-time loader should perform all relocation processing as part of object initialization. By default relocations may be performed on demand.

origin

Set the DF_ORIGIN flag to indicate that the object requires $ORIGIN processing.

pac-plt

AArch64 only, use pointer authentication in PLT.

pack-relative-relocs

Similar to -pack-dyn-relocs=relr , but synthesizes the GLIBC_ABI_DT_RELR version dependency if there is a GLIBC_2.* version dependency. glibc ld.so rejects loading a dynamically linked object without the GLIBC_ABI_DT_RELR version dependency.

rel

Use REL format for dynamic relocations.

rela

Use RELA format for dynamic relocations.

retpolineplt

Emit retpoline format PLT entries as a mitigation for CVE-2017-5715.

rodynamic

Make the .dynamic section read-only. The DT_DEBUG tag will not be emitted.

separate-loadable-segments

 

separate-code

 

noseparate-code

Specify whether two adjacent PT_LOAD segments are allowed to overlap in pages. noseparate-code (default) allows overlap. separate-code allows overlap between two executable segments, or two non-executable segments. separate-loadable-segments disallows overlap.

shstk

x86 only, use shadow stack.

stack-size=size

Set the main thread's stack size to size. The stack size is recorded as the size of the size. PT_GNU_STACK program segment.

start-stop-gc

Don't let __start_/__stop_ references retain the associated C identifier name sections (default).

nostart-stop-gc

Let __start_/__stop_ references retain the associated C identifier name sections.

text

Do not allow relocations against read-only segments. This is the default.

wxneeded

Create a PT_OPENBSD_WXNEEDED segment.

IMPLEMENTATION NOTES

ld.lld's handing of archive files (those with a .a file extension) is different from traditional linkers used on Unix-like systems.

Traditional linkers maintain a set of undefined symbols during linking. The linker processes each file in the order in which it appears on the command line, until the set of undefined symbols becomes empty. An object file is linked into the output object when it is encountered, with its undefined symbols added to the set. Upon encountering an archive file a traditional linker searches the objects contained therein, and processes those that satisfy symbols in the unresolved set.

Handling mutually dependent archives may be awkward when using a traditional linker. Archive files may have to be specified multiple times, or the special command line options --start-group and --end-group may be used to have the linker loop over the files in the group until no new symbols are added to the set.

ld.lld records all symbols found in objects and archives as it iterates over command line arguments. When ld.lld encounters an undefined symbol that can be resolved by an object file contained in a previously processed archive file, it immediately extracts and links it into the output object.

With certain archive inputs ld.lld may produce different results compared to traditional linkers. In practice, large bodies of third party software have been linked with ld.lld without material issues.

The --warn-backrefs option may be used to identify a linker invocation that may be incompatible with traditional Unix-like linker behavior.