Manual Pages  — LD.LLD

ld.lld – ELF linker from the LLVM project

SYNOPSIS DESCRIPTION OPTIONS IMPLEMENTATION NOTES

ld.lld [options] objfile ...

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.

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.
--define-common -, -d
	Assign space to common symbols.
--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
	Read a list of dynamic symbols from file. (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. 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
--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-O opt-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-define-common
	Do not assign space to common symbols.
--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. This is currently a no-op.
--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.
-O value
	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.

-O 1 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.
--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
	Undo the effect of --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.
--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.
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 -znotext 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.
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.

Ap 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.