LD(1)
💖 NAME 💖
ld — the GNU linker, bestie. That's it, that's the whole name section. This is straight out of LD(1) in the GNU Development Tools fam and we're gonna get into it 🌸
✨ SYNOPSIS ✨
ld [options] objfile ...🦋 DESCRIPTION 🦋
okay so picture this: you've got a whole pile of object files and archive files just sitting there, unlinked, tragic. ld combines a number of object and archive files, relocates their data, and ties up symbol references. That's the whole job. And usually? The very last step in compiling a program is to run ld. The final boss, basically 👑
ld accepts Linker Command Language files written in a superset of AT&T's Link Editor Command Language syntax, and the point of that is to give you explicit and total control over the linking process. Total control. Main character energy fr fr.
⚠️ real talk: this man page does not describe the command language. For full details on the command language and on other aspects of the GNU linker, go look up theldentry ininfo. iykyk 💅
This version of ld uses the general purpose BFD libraries to operate on object files. Why do we care? Because it means ld can read, combine, and write object files in many different formats — for example, COFF or a.out 🌈. Different formats may even be linked together to produce any available kind of object file. Versatile queen.
Aside from its flexibility, the GNU linker is more helpful than other linkers in providing diagnostic information. Many linkers just abandon execution immediately upon encountering an error, which is so dramatic and unhelpful 😭. But whenever possible, ld continues executing, which lets you identify other errors too — or, in some cases, get an output file in spite of the error. Resilient. We love her.
The GNU linker ld is meant to cover a broad range of situations, and to be as compatible as possible with other linkers. Which means... you have many choices to control its behavior. Many. Choices. Buckle up 🎀
💅 OPTIONS 💅
The linker supports a plethora of command-line options, but in actual practice few of them are used in any particular context. For instance, a frequent use of ld is to link standard Unix object files on a standard, supported Unix system. On such a system, to link a file hello.o:
ld -o <output> /lib/crt0.o hello.o -lcThis tells ld to produce a file called output as the result of linking the file /lib/crt0.o with hello.o and the library libc.a, which will come from the standard search directories. (See the discussion of the -l option below, bestie, it's coming 👀)
Some of the command-line options to ld may be specified at any point in the command line. HOWEVER — and this is the important part — options which refer to files, such as -l or -T, cause the file to be read at the point at which the option appears in the command line, relative to the object files and other file options. So position matters, no cap.
Repeating non-file options with a different argument will either have no further effect, or override prior occurrences (those further to the left on the command line) of that option. Options which may be meaningfully specified more than once are noted in the descriptions below ✍️
Non-option arguments are object files or archives which are to be linked together. They may follow, precede, or be mixed in with command-line options — except that an object file argument may not be placed between an option and its argument. Don't do it. It's giving chaos 🙈
Usually the linker is invoked with at least one object file, but you can specify other forms of binary input files using -l, -R, and the script command language. If no binary input files at all are specified, the linker does not produce any output, and issues the message:
No input files.If the linker cannot recognize the format of an object file, it will assume that it is a linker script 🧚. A script specified in this way augments the main linker script used for the link (either the default linker script or the one specified by using -T). This feature permits the linker to link against a file which appears to be an object or an archive, but actually merely defines some symbol values, or uses INPUT or GROUP to load other objects. Sneaky! Iconic!
Specifying a script in this way merely augments the main linker script, with the extra commands placed after the main script. Use the -T option to replace the default linker script entirely — but note the effect of the INSERT command. Noted 📝
For options whose names are a single letter, option arguments must either follow the option letter without intervening whitespace, or be given as separate arguments immediately following the option that requires them.
For options whose names are multiple letters, either one dash or two can precede the option name; for example, -trace-symbol and --trace-symbol are equivalent. BUT — note — there is one exception to this rule. Multiple letter options that start with a lower case 'o' can only be preceded by two dashes. Why? To reduce confusion with the -o option. So for example -omagic sets the output file name to magic whereas --omagic sets the NMAGIC flag on the output. Two completely different vibes 💀
Arguments to multiple-letter options must either be separated from the option name by an equals sign, or be given as separate arguments immediately following the option that requires them. For example, --trace-symbol foo and --trace-symbol=foo are equivalent. Unique abbreviations of the names of multiple-letter options are accepted ✨
⚠️ Note — if the linker is being invoked indirectly, via a compiler driver (e.g.gcc) then all the linker command-line options should be prefixed by-Wl,(or whatever is appropriate for the particular compiler driver) like this:
gcc -Wl,--start-group foo.o bar.o -Wl,--end-groupThis is important, because otherwise the compiler driver program may silently drop the linker options, resulting in a bad link 😱. Confusion may also arise when passing options that require values through a driver, as the use of a space between option and argument acts as a separator, and causes the driver to pass only the option to the linker and the argument to the compiler. In this case, it is simplest to use the joined forms of both single- and multiple-letter options, such as:
gcc foo.o bar.o -Wl,-eENTRY -Wl,-Map=a.mapHere is a table of the generic command-line switches accepted by the GNU linker:
@file — Read command-line options from file. The options read are inserted in place of the original@file option. If file does not exist, or cannot be read, then the option will be treated literally, and not removed. Options in file are separated by whitespace. A whitespace character may be included in an option by surrounding the entire option in either single or double quotes. Any character (including a backslash) may be included by prefixing the character to be included with a backslash. The file may itself contain additional@file options; any such options will be processed recursively 🔁-akeyword — This option is supported for HP/UX compatibility. The keyword argument must be one of the stringsarchive,shared, ordefault.-aarchiveis functionally equivalent to-Bstatic, and the other two keywords are functionally equivalent to-Bdynamic. This option may be used any number of times.--auditAUDITLIB — Adds AUDITLIB to theDT_AUDITentry of the dynamic section. AUDITLIB is not checked for existence, nor will it use theDT_SONAMEspecified in the library. If specified multiple timesDT_AUDITwill contain a colon separated list of audit interfaces to use. If the linker finds an object with an audit entry while searching for shared libraries, it will add a correspondingDT_DEPAUDITentry in the output file. This option is only meaningful on ELF platforms supporting the rtld-audit interface.-binput-format,--format=input-format —ldmay be configured to support more than one kind of object file. If yourldis configured this way, you can use the-boption to specify the binary format for input object files that follow this option on the command line. Even whenldis configured to support alternative object formats, you don't usually need to specify this, asldshould be configured to expect as a default input format the most usual format on each machine. input-format is a text string, the name of a particular format supported by the BFD libraries. (You can list the available binary formats withobjdump -i.) You may want to use this option if you are linking files with an unusual binary format. You can also use-bto switch formats explicitly (when linking object files of different formats), by including-binput-format before each group of object files in a particular format. The default format is taken from the environment variableGNUTARGET. You can also define the input format from a script, using the commandTARGET;-cMRI-commandfile,--mri-script=MRI-commandfile — For compatibility with linkers produced by MRI,ldaccepts script files written in an alternate, restricted command language, described in the MRI Compatible Script Files section of GNUlddocumentation. Introduce MRI script files with the option-c; use the-Toption to run linker scripts written in the general-purposeldscripting language. If MRI-cmdfile does not exist,ldlooks for it in the directories specified by any-Loptions. 🔍-d,-dc,-dp— These three options are equivalent; multiple forms are supported for compatibility with other linkers. They assign space to common symbols even if a relocatable output file is specified (with-r). The script commandFORCE_COMMON_ALLOCATIONhas the same effect.--depauditAUDITLIB,-PAUDITLIB — Adds AUDITLIB to theDT_DEPAUDITentry of the dynamic section. AUDITLIB is not checked for existence, nor will it use theDT_SONAMEspecified in the library. If specified multiple timesDT_DEPAUDITwill contain a colon separated list of audit interfaces to use. This option is only meaningful on ELF platforms supporting the rtld-audit interface. The-Poption is provided for Solaris compatibility.--enable-linker-version— Enables theLINKER_VERSIONlinker script directive, described in Output Section Data. If this directive is used in a linker script and this option has been enabled then a string containing the linker version will be inserted at the current point. > ⚠️ Note — the location of this option on the linker command line is significant. It will only affect linker scripts that come after it on the command line, or which are built into the linker.--disable-linker-version— Disables theLINKER_VERSIONlinker script directive, so that it does not insert a version string. This is the default. 🫶--enable-non-contiguous-regions— bestie, this one is literally the "it's fine, go find another seat" option 💅 it stops the linker from throwing a fit when an input section doesn't fit a matching output section.
The linker goes ahead and tries to allocate the input section to subsequent matching output sections, and generates an error only if no output section is large enough. This is useful when several non-contiguous memory regions are available and the input section does not require a particular one.
The order in which input sections are evaluated does not change, for instance:
MEMORY {
MEM1 (rwx) : ORIGIN = 0x1000, LENGTH = 0x14
MEM2 (rwx) : ORIGIN = 0x1000, LENGTH = 0x40
MEM3 (rwx) : ORIGIN = 0x2000, LENGTH = 0x40
}
SECTIONS {
mem1 : { *(.data.*); } > MEM1
mem2 : { *(.data.*); } > MEM2
mem3 : { *(.data.*); } > MEM3
}
with input sections:
.data.1: size 8
.data.2: size 0x10
.data.3: size 4results in .data.1 affected to mem1, and .data.2 and .data.3 affected to mem2, even though .data.3 would fit in mem3.
Heads up bestie, this option is incompatible with INSERT statements because it changes the way input sections are mapped to output sections. Not a vibe. 😭
--enable-non-contiguous-regions-warnings— this one turns on warnings for when--enable-non-contiguous-regionsallows possibly unexpected matches in sections mapping, potentially leading to silently discarding a section instead of failing because it does not fit any output region. Lowkey important, don't skip it 🫶-eentry,--entry=entry — use entry as the explicit symbol for beginning execution of your program, rather than the default entry point. If there is no symbol named entry, the linker will try to parse entry as a number, and use that as the entry address (the number will be interpreted in base 10; you may use a leading0xfor base 16, or a leading0for base 8). For i386 PE, entry can be also the original function name (without the leading underscore and/or the trailing stdcall@numberwhen applicable).--exclude-libslib,lib,... — gives the linker a list of archive libraries from which symbols should not be automatically exported 🙈 the library names may be delimited by commas or colons. Specifying--exclude-libs ALLexcludes symbols in all archive libraries from automatic export.
This option is available only for ELF and PE targeted ports of the linker. For PE targets, symbols explicitly listed in a .def file are still exported, regardless of this option. For ELF targeted ports, symbols affected by this option will be treated as hidden.
--exclude-modules-for-implibmodule,module,... — a list of object files or archive members from which symbols should not be automatically exported, but which should be copied wholesale into the import library being generated during the link. The module names may be delimited by commas or colons, and must match exactly the filenames used byldto open the files; for archive members, this is simply the member name, but for object files the name listed must include and match precisely any path used to specify the input file on the linker's command-line. Symbols explicitly listed in a.deffile are still exported, regardless of this option.
[This option is specific to PE targeted ports of the linker]
-E,--export-dynamic,--no-export-dynamic— when you're creating a dynamically linked executable, using the-Eoption or the--export-dynamicoption causes the linker to add all symbols to the dynamic symbol table. The dynamic symbol table is the set of symbols which are visible from dynamic objects at run time. It's giving "everyone gets an invite" energy ✨
If you do not use either of these options (or use the --no-export-dynamic option to restore the default behavior), the dynamic symbol table will normally contain only those symbols which are referenced by some dynamic object mentioned in the link.
If you use dlopen to load a dynamic object which needs to refer back to the symbols defined by the program, rather than some other dynamic object, then you will probably need to use this option when linking the program itself.
You can also use the dynamic list to control what symbols should be added to the dynamic symbol table if the output format supports it. See the description of --dynamic-list.
Note that this option is specific to ELF targeted ports. PE targets support a similar function to export all symbols from a DLL or EXE; see the description of --export-all-symbols below. 👑
--export-dynamic-symbol=glob — when creating a dynamically linked executable, symbols matching glob will be added to the dynamic symbol table. When creating a shared library, references to symbols matching glob will not be bound to the definitions within the shared library. This option is a no-op when creating a shared library and-Bsymbolicor--dynamic-listare not specified. This option is only meaningful on ELF platforms which support shared libraries.--export-dynamic-symbol-list=file — specify a--export-dynamic-symbolfor each pattern in the file. The format of the file is the same as the version node without scope and node name. See VERSION for more information.-EB— link big-endian objects. This affects the default output format.-EL— link little-endian objects. This affects the default output format.-fname,--auxiliary=name — when creating an ELF shared object, set the internalDT_AUXILIARYfield to the specified name. This tells the dynamic linker that the symbol table of the shared object should be used as an auxiliary filter on the symbol table of the shared object name.
If you later link a program against this filter object, then, when you run the program, the dynamic linker will see the DT_AUXILIARY field. If the dynamic linker resolves any symbols from the filter object, it will first check whether there is a definition in the shared object name. If there is one, it will be used instead of the definition in the filter object. The shared object name need not exist. Thus the shared object name may be used to provide an alternative implementation of certain functions, perhaps for debugging or for machine-specific performance.
This option may be specified more than once. The DT_AUXILIARY entries will be created in the order in which they appear on the command line. Periodt 💅
-Fname,--filter=name — when creating an ELF shared object, set the internalDT_FILTERfield to the specified name. This tells the dynamic linker that the symbol table of the shared object which is being created should be used as a filter on the symbol table of the shared object name.
If you later link a program against this filter object, then, when you run the program, the dynamic linker will see the DT_FILTER field. The dynamic linker will resolve symbols according to the symbol table of the filter object as usual, but it will actually link to the definitions found in the shared object name. Thus the filter object can be used to select a subset of the symbols provided by the object name.
Some older linkers used the -F option throughout a compilation toolchain for specifying object-file format for both input and output object files. The GNU linker uses other mechanisms for this purpose: the -b, --format, --oformat options, the TARGET command in linker scripts, and the GNUTARGET environment variable. The GNU linker will ignore the -F option when not creating an ELF shared object.
-fini=name — when creating an ELF executable or shared object, call NAME when the executable or shared object is unloaded, by settingDT_FINIto the address of the function. By default, the linker uses_finias the function to call.-g— ignored. Provided for compatibility with other tools. It's just there to be there, no thoughts, head empty 🍓-Gvalue,--gpsize=value — set the maximum size of objects to be optimized using the GP register to size. This is only meaningful for object file formats such as MIPS ELF that support putting large and small objects into different sections. This is ignored for other object file formats.-hname,-soname=name — when creating an ELF shared object, set the internalDT_SONAMEfield to the specified name. When an executable is linked with a shared object which has aDT_SONAMEfield, then when the executable is run the dynamic linker will attempt to load the shared object specified by theDT_SONAMEfield rather than using the file name given to the linker.-i— perform an incremental link (same as option-r).-init=name — when creating an ELF executable or shared object, call NAME when the executable or shared object is loaded, by settingDT_INITto the address of the function. By default, the linker uses_initas the function to call.-lnamespec,--library=namespec — add the archive or object file specified by namespec to the list of files to link. This option may be used any number of times. If namespec is of the form:filename,ldwill search the library path for a file calledfilename, otherwise it will search the library path for a file calledlibnamespec.a.
On systems which support shared libraries, ld may also search for files other than libnamespec.a. Specifically, on ELF and SunOS systems, ld will search a directory for a library called libnamespec.so before searching for one called libnamespec.a. (By convention, a .so extension indicates a shared library.) Note that this behavior does not apply to :filename, which always specifies a file called filename.
The linker will search an archive only once, at the location where it is specified on the command line. If the archive defines a symbol which was undefined in some object which appeared before the archive on the command line, the linker will include the appropriate file(s) from the archive. However, an undefined symbol in an object appearing later on the command line will not cause the linker to search the archive again. 👀
See the -( option for a way to force the linker to search archives multiple times.
You may list the same archive multiple times on the command line.
Okay so real talk, bestie: this whole archive-searching situation? It's just, like, standard for Unix linkers. Nothing wild. But — and this is a big but — if you're out here running ld on AIX, heads up, because the AIX linker does NOT behave like this. Different vibe entirely. Don't get caught slippin'. 💅
-L searchdir,--library-path=searchdir— Add the path searchdir to the list of paths thatldgoes hunting through for archive libraries andldcontrol scripts. Use it as many times as you want, no limits, go off. The directories get searched in the order you dropped them on the command line, and anything you name on the command line gets searched before the default directories.
Every -L option applies to all -l options, no matter what order they show up in. But — plot twist — -L options do not affect how ld searches for a linker script unless the -T option is specified. iykyk.
If searchdir starts with = or $SYSROOT, that prefix gets swapped out for the sysroot prefix — the one controlled by the --sysroot option, or the one specified when the linker was configured. ✨
The default set of paths it searches (like, when you don't hand it an -L) depends on which emulation mode ld is using, and sometimes also on how it was configured. Very "depends on the day" of it.
You can also declare paths inside a link script with the SEARCH_DIR command. Directories specified that way get searched at the point in which the linker script appears in the command line. 🫶
-m emulation— Emulate the emulation linker. You can pull up the full list of available emulations with the--verboseor-Voptions. If you don't use-m, the emulation gets taken from theLDEMULATIONenvironment variable — assuming that's even defined, bestie. Otherwise? The default emulation depends on how the linker was configured. C'est la vie. 💜--remap-inputs=pattern=filename,--remap-inputs-file=file— These two let you change the names of input files before the linker even tries to open them. Iconic, honestly. So--remap-inputs=foo.o=bar.omeans any attempt to load a file calledfoo.owill instead try to load a file calledbar.o. Wildcard patterns are permitted in the first filename, so--remap-inputs=foo*.o=bar.owill rename any input file matchingfoo*.otobar.o. 🌈
There's an alternative form, --remap-inputs-file=filename, which reads the remappings out of a file. Each line in that file can hold a single remapping. Blank lines get ignored. Anything from a hash character (#) to the end of a line counts as a comment and is also ignored. The mapping pattern can be separated from the filename by whitespace or an equals (=) character. So flexible. So demure.
You can specify these options multiple times — their contents just accumulate. 🎀 The remappings get processed in the order they occur on the command line, and if they came from a file, in the order they occur in that file. The moment a match is made, no further checking for that filename happens. Done. Periodt.
If the replacement filename is /dev/null or just NUL, the remapping will literally cause the input file to be ignored. Which is a super convenient way to experiment with removing input files from a complicated build environment. Science! 🔥
Note — this option is position dependent and only affects filenames that come after it on the command line. So this:
ld foo.o --remap-inputs=foo.o=bar.oWill have no effect, whereas:
ld --remap-inputs=foo.o=bar.o foo.oWill rename the input file foo.o to bar.o. Order matters, always.
Note — these options also affect files referenced by INPUT statements in linker scripts. But since linker scripts are processed after the entire command line is read, the position of the remap options on the command line isn't significant. 😌
If the verbose option is enabled, then any mappings that match get reported — although, again, the verbose option needs to be enabled on the command line before the remapped filenames appear. Timing, babes.
And if the -Map or --print-map options are enabled, the remapping list will be included in the map output. 📝
-M,--print-map— Print a link map to the standard output. A link map spills the tea about the link, including all of this:- Where object files are mapped into memory. 📍
- How common symbols are allocated.
- All archive members included in the link, with a mention of the symbol which caused the archive member to be brought in.
- The values assigned to symbols.
Note — symbols whose values are computed by an expression that involves a reference to a previous value of the same symbol may not have correct results displayed in the link map. Why? Because the linker discards intermediate results and only keeps the final value of an expression. 😭 Under those circumstances the linker will display the final value enclosed by square brackets. So for example a linker script containing:
foo = 1
foo = foo * 4
foo = foo + 8will produce the following output in the link map if the -M option is used:
0x00000001 foo = 0x1
[0x0000000c] foo = (foo * 0x4)
[0x0000000c] foo = (foo + 0x8)See Expressions for more information about expressions in linker scripts.
- How GNU properties are merged.
When the linker merges input .note.gnu.property sections into one output .note.gnu.property section, some properties get removed or updated. These actions are reported in the link map. For example:
Removed property 0xc0000002 to merge foo.o (0x1) and bar.o (not found)This indicates that property 0xc0000002 is removed from output when merging properties in foo.o, whose property 0xc0000002 value is 0x1, and bar.o, which doesn't have property 0xc0000002.
Updated property 0xc0010001 (0x1) to merge foo.o (0x1) and bar.o (0x1)This indicates that property 0xc0010001 value is updated to 0x1 in output when merging properties in foo.o, whose 0xc0010001 property value is 0x1, and bar.o, whose 0xc0010001 property value is 0x1.
- On some ELF targets, a list of fixups inserted by
--relax:
foo.o: Adjusting branch at 0x00000008 towards "far" in section .textThis indicates that the branch at 0x00000008 in foo.o, targeting the symbol "far" in section .text, has been replaced by a trampoline. 🦋
--print-map-discarded,--no-print-map-discarded— Print (or do not print) the list of discarded and garbage collected sections in the link map. Enabled by default. 🗑️--print-map-locals,--no-print-map-locals— Print (or do not print) local symbols in the link map. Local symbols will have the text(local)printed before their name, and will be listed after all of the global symbols in a given section. Temporary local symbols (typically those that start with.L) will not be included in the output. Disabled by default. 🙈-n,--nmagic— Turn off page alignment of sections, and disable linking against shared libraries. If the output format supports Unix style magic numbers, mark the output as"NMAGIC". No frills, no pages. 💀-N,--omagic— Set the text and data sections to be readable and writable. Also, do not page-align the data segment, and disable linking against shared libraries. If the output format supports Unix style magic numbers, mark the output as"OMAGIC".
Note — although a writable text section is allowed for PE-COFF targets, it does not conform to the format specification published by Microsoft. So like, technically permitted, but don't be messy about it. 😬
--no-omagic— This option negates most of the effects of the-Noption. It sets the text section to be read-only, and forces the data segment to be page-aligned. Note — this option does not enable linking against shared libraries. Use-Bdynamicfor that. 🙅-o output,--output=output— Use output as the name for the program produced byld. If you don't specify this option, the namea.outis used by default. The script commandOUTPUTcan also specify the output file name. ✨
Note — the linker will delete the output file before it starts to write to it. It will do this even if it turns out that the link can't be completed due to errors. Just. Gone. 😭
Note — the linker will check to make sure the output file name doesn't match the name of any of the input files, but that's it. That's all the checking you get. In particular it will not complain if the output file might overwrite a source file or some other important file. Therefore in build systems it is recommended to use the -o option as the last option on the linker command line. For example, consider:
ld -o $(EXE) $(OBJS)
ld $(OBJS) -o $(EXE)If the EXE variable isn't defined for some reason, the first version of the linker command could end up deleting one of the object files (the first one in the OBJS list), whereas the second version of the linker command will generate an error message and not delete anything. Protect your files, bestie, put -o last. 🫶
--dependency-file=depfile— Write a dependency file to depfile. This file contains a rule suitable formakedescribing the output file and all the input files that were read to produce it. The output is similar to the compiler's output with-M -MP.
Note — there is no option like the compiler's-MM, to exclude "system files" (which is not a well-specified concept in the linker, unlike "system headers" in the compiler). So the output from--dependency-fileis always specific to the exact state of the installation where it was produced, and should not be copied into distributed makefiles without careful editing. No copy-paste-and-pray here. 🧚
-O level— If level is a numeric value greater than zero,ldoptimizes the output. This might take significantly longer, and therefore probably should only be enabled for the final binary. 🌸 At the moment this option only affects ELF shared library generation. Future releases of the linker may make more use of this option. Also, currently there is no difference in the linker's behaviour for different non-zero values of this option. Again, this may change with future releases. So it's giving "watch this space." 👑
okay, still on -O level real quick —
If level is 0 or the string fast then ld skips the operations that are optional instead, which gives you a faster link but slower, larger binaries 😭. Currently the only operation that gets skipped is the combining of mergeable sections, but lowkey that may change in the future.
If level is the string default, or just the - character, then you get the linker's default behaviour: neither optimizing nor skipping. The neutral, moisturized, unbothered option ✨.
-pluginname — pull a plugin into the linking process. name is the absolute filename of the plugin. Usually this parameter gets added automatically by the compiler when you're doing link time optimization, but bestie, users can totally add their own plugins if they so wish 💅.
heads up: the location of compiler-originated plugins is different from the place where the ar, nm and ranlib programs search for their plugins. For those commands to make use of a compiler based plugin, it first has to be copied into the ${libdir}/bfd-plugins directory. All gcc based linker plugins are backward compatible, so it's enough to just copy in the newest one 👑.
--push-state— lets you preserve the current state of the flags governing input file handling, so they can all be restored with one corresponding--pop-stateoption. save point, basically 🫶.
The options covered are: -Bdynamic, -Bstatic, -dn, -dy, -call_shared, -non_shared, -static, -N, -n, --whole-archive, --no-whole-archive, --link-mapless, --no-link-mapless, -r, -Ur, --copy-dt-needed-entries, --no-copy-dt-needed-entries, --as-needed, --no-as-needed, and -a.
One target for this option is specifications for pkg-config. When used with the --libs option, all possibly needed libraries are listed and then possibly linked with all the time. It's better to return something like this:
-Wl,--push-state,--as-needed -libone -libtwo -Wl,--pop-state--pop-state— undoes the effect of--push-state, restoring the previous values of the flags governing input file handling. the rewind, the ctrl+z, the "not me forgetting my own settings" 🙈.-q,--emit-relocs— leave relocation sections and contents in fully linked executables. Post link analysis and optimization tools may need this info to perform correct modifications of executables. Tradeoff: larger executables 💀.
This option is currently only supported on ELF platforms.
--force-dynamic— force the output file to have dynamic sections. This option is specific to VxWorks targets.-r,--relocatable— generate relocatable output, i.e. generate an output file that can in turn serve as input told. Everyone calls this partial linking. Side effect: in environments that support standard Unix magic numbers, this option also sets the output file's magic number to"OMAGIC". If this option is not specified, an absolute file is produced. And when you're linking C++ programs, this option will not resolve references to constructors — for that, use-Ur.
When an input file doesn't have the same format as the output file, partial linking is only supported if that input file doesn't contain any relocations. Different output formats can have further restrictions; for example some "a.out"-based formats don't support partial linking with input files in other formats at all 🚫.
When the relocatable output contains both contents which require link-time optimization (LTO) and contents which don't require LTO, a .gnu_object_only section will be created to contain a relocatable object file, as if -r is applied to all relocatable inputs which don't require LTO. When processing a relocatable input with a .gnu_object_only section, the linker will extract the .gnu_object_only section as a separate input.
Note that since -r groups some sections from different input files together, there may be negative impacts on code size and locality in the final executable or shared library 😬.
This option does the same thing as -i.
-Rfilename,--just-symbols=filename — read symbol names and their addresses from filename, but do not relocate it or include it in the output. This lets your output file refer symbolically to absolute locations of memory defined in other programs. You may use this option more than once.
For compatibility with other ELF linkers, if the -R option is followed by a directory name, rather than a file name, it is treated as the -rpath option. sneaky 😏.
--rosegment,--no-rosegment— attempt to ensure that only a single read-only, non-code segment is created. Only useful when used in conjunction with the-z separate-codeoption. The resulting binaries should be smaller than if-z separate-codeis used on its own. Without this option, or if--no-rosegmentis specified, the-z separate-codeoption will create two read-only segments, one before the code segment and one after it.
The name of the options are misleading, but they have been chosen in order for the linker to be compatible with the LLD and GOLD linkers. iykyk.
Thse options (their typo, not mine 💅) are only supported by ELF targets.
-s,--strip-all— omit all symbol information from the output file. every last crumb 🍓.-S,--strip-debug— omit debugger symbol information (but not all symbols) from the output file.--strip-discarded,--no-strip-discarded— omit (or do not omit) global symbols defined in discarded sections. Enabled by default.-plugin-save-temps— store the plugin "temporary" intermediate files permanently. no take-backs 💖.-t,--trace— print the names of the input files asldprocesses them. If-tis given twice then members within archives are also printed.-toutput is useful to generate a list of all the object files and scripts involved in linking — for example when packaging files for a linker bug report 🐛.-Tscriptfile,--script=scriptfile — use scriptfile as the linker script. This script replacesld's default linker script (rather than adding to it), unless the script contains"INSERT", so commandfile must specify everything necessary to describe the output file.
If scriptfile does not exist in the current directory, ld looks for it in the directories specified by any preceding -L options.
Command line options that appear before the -T option can affect the script, but command line options that appear after it do not.
Multiple -T options will accumulate if they are augmenting the current script, otherwise the last, non-augmenting, -T option will be used.
There are other ways of specifying linker scripts. See
-dTscriptfile,--default-script=scriptfile — use scriptfile as the default linker script.
This option is similar to the --script option except that processing of the script is delayed until after the rest of the command line has been processed. That allows options placed after the --default-script option on the command line to affect the behaviour of the linker script, which can be important when the linker command line cannot be directly controlled by the user (eg because the command line is being constructed by another tool, such as gcc) 🧚.
-usymbol,--undefined=symbol — force symbol to be entered in the output file as an undefined symbol. Doing this may, for example, trigger linking of additional modules from standard libraries.-umay be repeated with different option arguments to enter additional undefined symbols. This option is equivalent to the"EXTERN"linker script command.
If this option is being used to force additional modules to be pulled into the link, and if it is an error for the symbol to remain undefined, then the option --require-defined should be used instead.
--require-defined=symbol — require that symbol is defined in the output file. This option is the same as option--undefinedexcept that if symbol is not defined in the output file then the linker will issue an error and exit 🚨. The same effect can be achieved in a linker script by using"EXTERN","ASSERT"and"DEFINED"together. This option can be used multiple times to require additional symbols.-Ur— for programs that do not use constructors or destructors, or for ELF based systems, this option is equivalent to-r: it generates relocatable output, i.e. an output file that can in turn serve as input told. For other binaries however the-Uroption is similar to-rbut it also resolves references to constructors and destructors.
For those systems where -r and -Ur behave differently, it does not work to use -Ur on files that were themselves linked with -Ur — once the constructor table has been built, it cannot be added to. Use -Ur only for the last partial link, and -r for the others. read that twice bestie 😭.
--orphan-handling=MODE — control how orphan sections are handled. An orphan section is one not specifically mentioned in a linker script 🥺.
MODE can have any of the following values:
"place"— orphan sections are placed into a suitable output section following the strategy described in Orphan Sections. The option--uniquealso affects how sections are placed."discard"— all orphan sections are discarded, by placing them in the/DISCARD/section."warn"— the linker will place the orphan section as for"place"and also issue a warning."error"— the linker will exit with an error if any orphan section is found.
The default if --orphan-handling is not given is "place".
--unique[=SECTION]— creates a separate output section for every input section matching SECTION, or if the optional wildcard SECTION argument is missing, for every orphan input section. (An orphan section is one not specifically mentioned in a linker script.) You may use this option multiple times on the command line; it prevents the normal merging of input sections with the same name, overriding output section assignments in a linker script 🦋.-v,--version,-V— display the version number forld. The-Voption also lists the supported emulations. See also the description of the--enable-linker-versionin Options,,Command-line Options which can be used to insert the linker version string into a binary.-x,--discard-all— delete all local symbols.-X,--discard-locals— bestie, this one just deletes all the temporary local symbols. All of them. Gone. (We're talking the ones that start with system-specific local label prefixes — usually.Lon ELF systems, orLon the old-school traditional a.out systems, iykyk.)-ysymbol,--trace-symbol=symbol — prints the name of every linked file where symbol shows up 🕵️. You can hand this option over as many times as you want — it's not a one-time thing. Heads up though: on a lot of systems you gotta prepend an underscore. This one is so useful when you've got an undefined symbol in your link and you're like "where tf is this reference even coming from 😭".-Ypath — adds path to the default library search path. Keepin' it real: this option exists purely for Solaris compatibility. That's the whole vibe.-zkeyword — okay so the keywords it recognizes are, in order:call-nop=prefix-addr,call-nop=suffix-nop,call-nop=prefix-byte,call-nop=suffix-byte— these specify the 1-byteNOPpadding when transforming an indirect call to a locally defined function,foo, via its GOT slot. So:call-nop=prefix-addrgenerates"0x67 call foo".call-nop=suffix-nopgenerates"call foo 0x90".call-nop=prefix-bytegenerates"byte call foo". Andcall-nop=suffix-bytegenerates"call foo byte". Supported for i386 and x86_64 ✨.cet-report=none,cet-report=warning,cet-report=error— controls how the missingGNU_PROPERTY_X86_FEATURE_1_IBTandGNU_PROPERTY_X86_FEATURE_1_SHSTKproperties get reported in the input.note.gnu.propertysection.cet-report=noneis the default, and it makes the linker not report missing properties in input files.cet-report=warningmakes the linker throw a warning for missing properties in input files.cet-report=errormakes the linker throw an error for missing properties in input files. Also note:ibtwill turn off the missingGNU_PROPERTY_X86_FEATURE_1_IBTproperty report, andshstkwill turn off the missingGNU_PROPERTY_X86_FEATURE_1_SHSTKproperty report. Supported for Linux/i386 and Linux/x86_64 💅.combreloc,nocombreloc— combines multiple dynamic relocation sections and sorts them to improve dynamic symbol lookup caching. And withnocombreloc, you just… don't do that. Simple as.common,nocommon— generates common symbols withSTT_COMMONtype during a relocatable link. If you gonocommon, useSTT_OBJECTtype instead.common-page-size=value — sets the page size most commonly used to value. The memory image layout gets optimized to minimize memory pages if the system is using pages of this size. Chef's kiss 👑defs— reports unresolved symbol references from regular object files. This happens even if the linker is creating a non-symbolic shared library. Fun fact: this option is the exact inverse of-z undefs.dynamic-undefined-weak,nodynamic-undefined-weak— makes undefined weak symbols dynamic when building a dynamic object, if they're referenced from a regular object file and not forced local by symbol visibility or versioning.nodynamic-undefined-weak= don't make them dynamic. If you give neither option, a target may default to either option being in force, or make some other selection of undefined weak symbols dynamic. Also, not all targets support these options, so don't assume 🌸.execstack— marks the object as requiring executable stack.global— this one is only meaningful when building a shared object. It makes the symbols defined by this shared object available for symbol resolution of subsequently loaded libraries.globalaudit— only meaningful when building a dynamic executable. It marks the executable as requiring global auditing by setting the"DF_1_GLOBAUDIT"bit in the"DT_FLAGS_1"dynamic tag. Global auditing requires that any auditing library defined via the--depauditor-Pcommand-line options be run for all dynamic objects loaded by the application.ibtplt— generates Intel Indirect Branch Tracking (IBT) enabled PLT entries. Supported for Linux/i386 and Linux/x86_64.ibt— generatesGNU_PROPERTY_X86_FEATURE_1_IBTin.note.gnu.propertysection to indicate compatibility with IBT. This also impliesibtplt. Supported for Linux/i386 and Linux/x86_64.indirect-extern-access,noindirect-extern-access— generatesGNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESSin.note.gnu.propertysection to indicate that the object file requires canonical function pointers and cannot be used with copy relocation. This option also impliesnoextern-protected-dataandnocopyreloc. Supported for i386 and x86-64.
And then noindirect-extern-access removes GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS from .note.gnu.property section.
initfirst— only meaningful when building a shared object. It marks the object so that its runtime initialization will happen before the runtime initialization of any other objects brought into the process at the same time. Similarly, the runtime finalization of the object will happen after the runtime finalization of any other objects. First in, last out, icon behavior fr fr.interpose— tells the dynamic loader it should modify its symbol search order so that symbols in this shared library interpose all other shared libraries not so marked.unique,nounique— when generating a shared library or other dynamically loadable ELF object, marks it as one that should (by default) only ever be loaded once, and only in the main namespace (when using"dlmopen"). This is mostly used to mark fundamental libraries like libc, libpthread et al, which don't usually function correctly unless they're the sole instances of themselves. This behaviour can be overridden by the"dlmopen"caller and does not apply to certain loading mechanisms (such as audit libraries).lam-u48— generatesGNU_PROPERTY_X86_FEATURE_1_LAM_U48in.note.gnu.propertysection to indicate compatibility with Intel LAM_U48. Supported for Linux/x86_64.lam-u57— generatesGNU_PROPERTY_X86_FEATURE_1_LAM_U57in.note.gnu.propertysection to indicate compatibility with Intel LAM_U57. Supported for Linux/x86_64.lam-u48-report=none,lam-u48-report=warning,lam-u48-report=error— controls how the missingGNU_PROPERTY_X86_FEATURE_1_LAM_U48property gets reported in the input.note.gnu.propertysection.lam-u48-report=noneis the default and makes the linker not report missing properties in input files.lam-u48-report=warningmakes the linker issue a warning for missing properties in input files.lam-u48-report=errormakes the linker issue an error for missing properties in input files. Supported for Linux/x86_64 ⭐.lam-u57-report=none,lam-u57-report=warning,lam-u57-report=error— same energy, but for the missingGNU_PROPERTY_X86_FEATURE_1_LAM_U57property in the input.note.gnu.propertysection.lam-u57-report=noneis the default (no reporting of missing properties in input files),lam-u57-report=warningissues a warning,lam-u57-report=errorissues an error. Supported for Linux/x86_64.lam-report=none,lam-report=warning,lam-report=error— and this one covers both the missingGNU_PROPERTY_X86_FEATURE_1_LAM_U48andGNU_PROPERTY_X86_FEATURE_1_LAM_U57properties in the input.note.gnu.propertysection.lam-report=noneis the default and makes the linker not report missing properties in input files.lam-report=warningissues a warning for missing properties in input files.lam-report=errorissues an error for missing properties in input files. Supported for Linux/x86_64.lazy— when generating an executable or shared library, marks it to tell the dynamic linker to defer function call resolution to the point when the function is called (that's lazy binding), rather than at load time. And lowkey, lazy binding is the default anyway.loadfltr— specifies that the object's filters be processed immediately at runtime.max-page-size=value — sets the maximum memory page size supported to value.mark-plt,nomark-plt— marks PLT entries with dynamic tags,DT_X86_64_PLT,DT_X86_64_PLTSZandDT_X86_64_PLTENT. ⚠️ Okay so real talk: since this option stores a non-zero value in ther_addendfield ofR_X86_64_JUMP_SLOTrelocations, the resulting executables and shared libraries are incompatible with dynamic linkers such as those in older versions of glibc without the change to ignorer_addendinR_X86_64_GLOB_DATandR_X86_64_JUMP_SLOTrelocations, which don't ignore ther_addendfield ofR_X86_64_JUMP_SLOTrelocations. Supported for x86_64.muldefs— allows multiple definitions. Chaos permitted, apparently 😌.nocopyreloc— disables linker-generated.dynbssvariables used in place of variables defined in shared libraries. Heads up: this may result in dynamic text relocations.nodefaultlib— specifies that the dynamic loader's search for dependencies of this object should ignore any default library search paths.nodelete— specifies that the object shouldn't be unloaded at runtime.nodlopen— specifies that the object is not available to"dlopen".nodump— specifies that the object cannot be dumped by"dldump".noexecstack— marks the object as not requiring executable stack.noextern-protected-data— don't treat protected data symbols as external when building a shared library. This option overrides the linker backend default. It can be used to work around incorrect relocations against protected data symbols generated by compiler. Fair warning: updates on protected data symbols by another module aren't visible to the resulting shared library 👀. Supported for i386 and x86-64.
noreloc-overflow— kills the relocation overflow check 💀. only use this if you're certain there's not gonna be any dynamic relocation overflow at run-time. supported for x86_64.memory-seal,nomemory-seal— tells the executable or shared library that all thePT_LOADsegments should be sealed so nobody can mess with them anymore (like changing the protection flags, the segment size, or removing the mapping). it's a security hardening thing that needs system support, and it generatesGNU_PROPERTY_MEMORY_SEALin the.note.gnu.propertysection.now— when you're generating an executable or shared library, this marks it to tell the dynamic linker to resolve all the symbols when the program starts, or when the shared library gets loaded bydlopen— instead of waiting until the function is actually first called. no deferring, bestie.origin— says the object requires$ORIGINhandling in paths.pack-relative-relocs,nopack-relative-relocs— generates compact relative relocation in position-independent executables and shared libraries ✨. it addsDT_RELR,DT_RELRSZandDT_RELRENTentries to the dynamic section. it gets ignored when you're building a position-dependent executable and relocatable output.nopack-relative-relocsis the default, which disables compact relative relocation. when linked against the GNU C Library, aGLIBC_ABI_DT_RELRsymbol version dependency on the shared C Library gets added to the output. supported for i386 and x86-64.relro,norelro— creates an ELFPT_GNU_RELROsegment header in the object, which is a memory segment that should be made read-only after relocation, if supported. careful though: specifyingcommon-page-sizesmaller than the system page size will render this protection totally useless 😭.norelromeans don't create thatPT_GNU_RELROsegment at all.report-relative-reloc— reports dynamic relative relocations generated by the linker. supported for Linux/i386 and Linux/x86_64.sectionheader,nosectionheader— generates the section header.nosectionheadermeans don't generate it.sectionheaderis the default.separate-code,noseparate-code— creates a separate codePT_LOADsegment header in the object. this is a memory segment that should contain only instructions and has to be in wholly disjoint pages from any other data.noseparate-codemeans no separate codePT_LOADsegment.shstk— generatesGNU_PROPERTY_X86_FEATURE_1_SHSTKin the.note.gnu.propertysection to indicate compatibility with Intel Shadow Stack. supported for Linux/i386 and Linux/x86_64.stack-size=value— specifies a stack size for an ELFPT_GNU_STACKsegment. specifying zero will override any default non-zero sizedPT_GNU_STACKsegment creation.start-stop-gc,nostart-stop-gc— okay so when--gc-sectionsis in effect, a reference from a retained section to__start_SECNAMEor__stop_SECNAMEcauses all input sections namedSECNAMEto also be retained — but only ifSECNAMEis representable as a C identifier and either__start_SECNAMEor__stop_SECNAMEis synthesized by the linker.-z start-stop-gcdisables this effect, letting sections get garbage collected like those special synthesized symbols were never defined 🗑️. but heads up:-z start-stop-gchas no effect on a definition of__start_SECNAMEor__stop_SECNAMEin an object file or linker script. such a definition will prevent the linker from providing a synthesized__start_SECNAMEor__stop_SECNAMErespectively, and therefore the special treatment by garbage collection for those references.start-stop-visibility=value— specifies the ELF symbol visibility for synthesized__start_SECNAMEand__stop_SECNAMEsymbols. value must be exactlydefault,internal,hidden, orprotected. if no-z start-stop-visibilityoption is given,protectedis used for compatibility with historical practice. however, it's highly recommended to use-z start-stop-visibility=hiddenin new programs and shared libraries so these symbols don't get exported between shared objects — which is usually not what you intended bestie 💅.text,notext,textoff— reports an error ifDT_TEXTRELis set, i.e. if the position-independent or shared object has dynamic relocations in read-only sections.notextortextoffmeans don't report that error.undefs— do not report unresolved symbol references from regular object files, whether you're creating an executable or a shared library. this option is the inverse of-z defs.unique-symbol,nounique-symbol— avoids duplicated local symbol names in the symbol string table.unique-symbolappends"."number"to duplicated local symbol names.nounique-symbolis the default.x86-64-baseline,x86-64-v2,x86-64-v3,x86-64-v4— specify the x86-64 ISA level needed in the.note.gnu.propertysection.x86-64-baselinegeneratesGNU_PROPERTY_X86_ISA_1_BASELINE.x86-64-v2generatesGNU_PROPERTY_X86_ISA_1_V2.x86-64-v3generatesGNU_PROPERTY_X86_ISA_1_V3.x86-64-v4generatesGNU_PROPERTY_X86_ISA_1_V4. supported for Linux/i386 and Linux/x86_64.isa-level-report=none,isa-level-report=all,isa-level-report=needed,isa-level-report=used— specifies how to report x86-64 ISA levels in input relocatable files.isa-level-report=none, which is the default, makes the linker not report x86-64 ISA levels in input files.isa-level-report=allmakes the linker report needed and used x86-64 ISA levels in input files.isa-level-report=neededmakes it report needed x86-64 ISA levels in input files.isa-level-report=usedmakes it report used x86-64 ISA levels in input files. supported for Linux/i386 and Linux/x86_64.
other keywords are ignored for Solaris compatibility. (yes, ignored. iconic honestly.)
💖 --gnu-tls-tag / --no-gnu-tls-tag 💖
--gnu-tls-tag,--no-gnu-tls-tag— adds aGLIBC_ABI_GNU_TLSversion tag dependency in output programs and shared libraries when linking against glibc, if input relocatable object files call___tls_get_addr. the output will fail to load and run at run-time against glibc that doesn't define theGLIBC_ABI_GNU_TLSversion tag 😭. unless it's disabled by the--disable-gnu-tls-tagconfigure option at linker build time, when no options are specified, the linker will add theGLIBC_ABI_GNU_TLSversion tag dependency if the inputs have a___tls_get_addrcall andlibc.sodefines theGLIBC_ABI_GNU_TLSversion tag. supported for Linux/i386.
✨ --gnu2-tls-tag / --no-gnu2-tls-tag ✨
--gnu2-tls-tag,--no-gnu2-tls-tag— adds aGLIBC_ABI_GNU2_TLSversion tag dependency in output programs and shared libraries when linking against glibc, if input relocatable object files have anR_386_TLS_DESC_CALLorR_X86_64_TLSDESC_CALLrelocation. same deal: the output will fail to load and run at run-time against glibc which doesn't define theGLIBC_ABI_GNU2_TLSversion tag. unless disabled by the--disable-gnu2-tls-tagconfigure option at linker build time, when no options are specified, the linker will add theGLIBC_ABI_GNU2_TLSversion tag dependency if inputs have anR_386_TLS_DESC_CALLorR_X86_64_TLSDESC_CALLrelocation andlibc.sodefines theGLIBC_ABI_GNU2_TLSversion tag. supported for Linux/i386 and Linux/x86_64.
🫶 archive grouping: -( archives -) / --start-group / --end-group 🫶
-( archives -),--start-group archives --end-group— the archives should be a list of archive files. they may be either explicit file names, or-loptions.
so here's the tea ☕: the specified archives get searched repeatedly until no new undefined references pop up. normally, an archive is searched only once, in the order it's specified on the command line. so if a symbol in that archive is needed to resolve an undefined symbol referred to by an object in an archive that appears later on the command line, the linker would be like "nope, can't resolve that" 🙈. by grouping the archives, they all get searched repeatedly until all possible references are resolved. slay.
this option is not allowed within a--start-lib/--end-liboption pair.
using this option has a significant performance cost ⚠️. it's best to use it only when there are unavoidable circular references between two or more archives.
🧚 --start-lib objects --end-lib 🧚
--start-lib objects --end-lib— the objects should be a list of object files.
the specified objects get treated as if they were members of an archive whose name has been placed at the location of --start-lib on the command line. all the usual linker archive handling properties and command line options apply to such an artificial archive 💅.
this option may be used multiple times, in which case each set of the objects specified will be treated as an individual archive. nesting this option is not allowed though.
options that affect archive processing are not allowed between --start-lib and --end-lib, because it would make zero sense to apply them midway through handling an archive. these options include: -(/--start-group, -)/--end-group, --whole-archive, and --no-whole-archive, as well as --pop-state where it would change the state of the --whole-archive setting.
🦋 --accept-unknown-input-arch / --no-accept-unknown-input-arch 🦋
--accept-unknown-input-arch,--no-accept-unknown-input-arch— tells the linker to accept input files whose architecture can't be recognised. the assumption is that the user knows what they're doing and deliberately wants to link in these unknown input files 👀. this was the default behaviour of the linker before release 2.14. from release 2.14 onwards, the default behaviour is to reject such input files, and so the--accept-unknown-input-archoption was added to restore the old behaviour.--as-needed,--no-as-needed— okay so this one is about ELFDT_NEEDEDtags for dynamic libraries that show up on the command line after the--as-neededoption. Normally the linker is extra and adds aDT_NEEDEDtag for literally every dynamic library mentioned on the command line, whether the library is actually needed or not 💀.--as-neededmakes it so aDT_NEEDEDtag only gets emitted for a library that, at that point in the link, satisfies a non-weak undefined symbol reference from a regular object file — or, if the library isn't found in theDT_NEEDEDlists of other needed libraries, a non-weak undefined symbol reference from another needed dynamic library. And bestie note this: object files or libraries that appear on the command line after the library in question don't affect whether the library is seen as needed. It's basically the same energy as the rules for extraction of object files from archives.--no-as-neededrestores the default behaviour.
Lowkey important: on Linux based systems the--as-neededoption also has an affect on the behaviour of the--rpathand--rpath-linkoptions. See the description of--rpath-linkfor more details. 🌸
--add-needed,--no-add-needed— so these two have been deprecated, because their names are too similar to--as-neededand--no-as-neededand that's just chaos. They've been replaced by--copy-dt-needed-entriesand--no-copy-dt-needed-entries. Periodt.-assertkeyword — this option is ignored for SunOS compatibility. That's it, that's the whole vibe. 🙈-Bdynamic,-dy,-call_shared— link against dynamic libraries ✨. This is only meaningful on platforms for which shared libraries are supported. This option is normally the default on such platforms. The different variants of this option exist for compatibility with various systems. You may use this option multiple times on the command line: it affects library searching for-loptions which follow it.-Bgroup— set the"DF_1_GROUP"flag in the"DT_FLAGS_1"entry in the dynamic section 👑. This makes the runtime linker handle lookups in this object and its dependencies to be performed only inside the group.--unresolved-symbols=report-allis implied. This option is only meaningful on ELF platforms which support shared libraries.-Bstatic,-dn,-non_shared,-static— do not link against shared libraries, nope 🚫. This is only meaningful on platforms for which shared libraries are supported. The different variants exist for compatibility with various systems. You may use this option multiple times on the command line: it affects library searching for-loptions which follow it. This option also implies--unresolved-symbols=report-all. And plot twist — this option can be used with-shared. Doing so means that a shared library is being created, but that all of the library's external references must be resolved by pulling in entries from static libraries. Sneaky but iconic.-Bsymbolic— when creating a shared library, bind references to global symbols to the definition within the shared library, if any 💅. Normally it's possible for a program linked against a shared library to override the definition within the shared library. This option is only meaningful on ELF platforms which support shared libraries.-Bsymbolic-functions— same thing but for global function symbols 🫶, when creating a shared library, bind references to them to the definition within the shared library, if any. This option is only meaningful on ELF platforms which support shared libraries.-Bno-symbolic— this option can cancel previously specified-Bsymbolicand-Bsymbolic-functions. Undo button energy ✨.- *
--dynamic-list=dynamic-list-file* — specify the name of a dynamic list file to the linker. This is typically used when creating shared libraries to specify a list of global symbols whose references shouldn't be bound to the definition within the shared library, or when creating dynamically linked executables to specify a list of symbols which should be added to the symbol table in the executable. This option is only meaningful on ELF platforms which support shared libraries.
The format of the dynamic list is the same as the version node without scope and node name. See VERSION for more information.
--dynamic-list-data— include all global data symbols to the dynamic list 💖.--dynamic-list-cpp-new— provide the builtin dynamic list for C++operator newanddelete. It is mainly useful for building shared libstdc++.--dynamic-list-cpp-typeinfo— provide the builtin dynamic list for C++ runtime type identification 🌈.--check-sections,--no-check-sections— asks the linker not to check section addresses after they have been assigned, to see if there are any overlaps. Normally the linker will perform this check, and if it finds any overlaps it will produce suitable error messages. The linker does know about, and does make allowances for, sections in overlays. The default behaviour can be restored by using the command-line switch--check-sections. Section overlap is not usually checked for relocatable links. You can force checking in that case by using the--check-sectionsoption.--copy-dt-needed-entries,--no-copy-dt-needed-entries— this one is about how dynamic libraries referred to byDT_NEEDEDtags inside ELF dynamic libraries mentioned on the command line get treated. Normally the linker won't add aDT_NEEDEDtag to the output binary for each library mentioned in aDT_NEEDEDtag in an input dynamic library. With--copy-dt-needed-entriesspecified on the command line though, any dynamic libraries that follow it will have theirDT_NEEDEDentries added. The default behaviour can be restored with--no-copy-dt-needed-entries.
This option also has an effect on the resolution of symbols in dynamic libraries 😭. With --copy-dt-needed-entries, dynamic libraries mentioned on the command line will be recursively searched, following their DT_NEEDED tags to other libraries, in order to resolve symbols required by the output binary. With the default setting, however, the searching of dynamic libraries that follow it will stop with the dynamic library itself. No DT_NEEDED links will be traversed to resolve symbols.
--cref— output a cross reference table 📋. If a linker map file is being generated, the cross reference table is printed to the map file. Otherwise, it is printed on the standard output.
The format of the table is intentionally simple, so that it may be easily processed by a script if necessary. The symbols are printed out, sorted by name. For each symbol, a list of file names is given. If the symbol is defined, the first file listed is the location of the definition. If the symbol is defined as a common value then any files where this happens appear next. Finally any files that reference the symbol are listed. So organized bestie 💅.
--ctf-variables,--no-ctf-variables— the CTF debuginfo format supports a section which encodes the names and types of variables found in the program which do not appear in any symbol table 🦋. These variables clearly cannot be looked up by address by conventional debuggers, so the space used for their types and names is usually wasted: the types are usually small but the names are often not.--ctf-variablescauses the generation of such a section. The default behaviour can be restored with--no-ctf-variables.- *
--ctf-share-types=method* — adjust the method used to share types between translation units in CTF.share-unconflicted— put all types that do not have ambiguous definitions into the shared dictionary, where debuggers can easily access them, even if they only occur in one translation unit. This is the default. 👑share-duplicated— put only types that occur in multiple translation units into the shared dictionary: types with only one definition go into per-translation-unit dictionaries. Types with ambiguous definitions in multiple translation units always go into per-translation-unit dictionaries. This tends to make the CTF larger, but may reduce the amount of CTF in the shared dictionary. For very large projects this may speed up opening the CTF and save memory in the CTF consumer at runtime. Lowkey efficient ✨.
--no-define-common— this option inhibits the assignment of addresses to common symbols. The script command"INHIBIT_COMMON_ALLOCATION"has the same effect.
The --no-define-common option allows decoupling the decision to assign addresses to Common symbols from the choice of the output file type; otherwise a non-Relocatable output type forces assigning addresses to Common symbols. Using --no-define-common allows Common symbols that are referenced from a shared library to be assigned addresses only in the main program 💜. This eliminates the unused duplicate space in the shared library, and also prevents any possible confusion over resolving to the wrong duplicate when there are many dynamic modules with specialized search paths for runtime symbol resolution.
--force-group-allocation— this option causes the linker to place section group members like normal input sections, and to delete the section groups. This is the default behaviour for a final link, but this option can be used to change the behaviour of a relocatable link (-r). The script command"FORCE_GROUP_ALLOCATION"has the same effect.- *
--defsym=symbol*=expression — create a global symbol in the output file, containing the absolute address given by expression. You may use this option as many times as necessary to define multiple symbols in the command line. A limited form of arithmetic is supported for the expression in this context: you may give a hexadecimal constant or the name of an existing symbol, or use"+"and"-"to add or subtract hexadecimal constants or symbols. If you need more elaborate expressions, consider using the linker command language from a script.
Note: there should be no white space between symbol, the equals sign ("="), and expression. Fr fr, don't do it 💀.
The linker processes --defsym arguments and -T arguments in order — putting --defsym before -T will define the symbol before the linker script from -T is processed, while putting --defsym after -T will define the symbol after the linker script has been processed. This difference has consequences for expressions within the linker script that use the --defsym symbols, and which order is correct will depend on what you are trying to achieve. so real, bestie 💖
--demangle[=style],--no-demangle— these options control whether to demangle symbol names in error messages and other output. When the linker is told to demangle, it tries to present symbol names in a readable fashion: it strips leading underscores if they are used by the object file format, and converts C++ mangled symbol names into user readable names. Different compilers have different mangling styles. The optional demangling style argument can be used to choose an appropriate demangling style for your compiler. The linker will demangle by default unless the environment variableCOLLECT_NO_DEMANGLEis set. These options may be used to override the default. ✨ iconic behavior, honestly-Ifile,--dynamic-linker=file— set the name of the dynamic linker. This is only meaningful when generating dynamically linked ELF executables. The default dynamic linker is normally correct; don't use this unless you know what you are doing. ⚠️ for real, do not touch unless you know what you're doing--no-dynamic-linker— when producing an executable file, omit the request for a dynamic linker to be used at load-time. This is only meaningful for ELF executables that contain dynamic relocations, and usually requires entry point code that is capable of processing these relocations.--embedded-relocs— this option is similar to the--emit-relocsoption except that the relocs are stored in a target-specific section. This option is only supported by the BFIN, CR16 and M68K targets.--disable-multiple-abs-defs— do not allow multiple definitions with symbols included in filename invoked by-Ror--just-symbols.--fatal-warnings,--no-fatal-warnings— treat all warnings as errors. The default behaviour can be restored with the option--no-fatal-warnings.-w,--no-warnings— do not display any warning or error messages. This overrides--fatal-warningsif it has been enabled. This option can be used when it is known that the output binary will not work, but there is still a need to create it. chaotic but valid 💀--force-exe-suffix— make sure that an output file has a.exesuffix. If a successfully built fully linked output file does not have a.exeor.dllsuffix, this option forces the linker to copy the output file to one of the same name with a.exesuffix. This option is useful when using unmodified Unix makefiles on a Microsoft Windows host, since some versions of Windows won't run an image unless it ends in a.exesuffix.--gc-sections,--no-gc-sections— enable garbage collection of unused input sections. It is ignored on targets that do not support this option. The default behaviour (of not performing this garbage collection) can be restored by specifying--no-gc-sectionson the command line. Note that garbage collection for COFF and PE format targets is supported, but the implementation is currently considered to be experimental. experimental? we love a risky queen 👑
--gc-sections decides which input sections are used by examining symbols and relocations. The section containing the entry symbol and all sections containing symbols undefined on the command-line will be kept, as will sections containing symbols referenced by dynamic objects. Note that when building shared libraries, the linker must assume that any visible symbol is referenced. Once this initial set of sections has been determined, the linker recursively marks as used any section referenced by their relocations. See --entry, --undefined, and --gc-keep-exported.
This option can be set when doing a partial link (enabled with option -r). In this case the root of symbols kept must be explicitly specified either by one of the options --entry, --undefined, or --gc-keep-exported or by a "ENTRY" command in the linker script.
As a GNU extension, ELF input sections marked with the "SHF_GNU_RETAIN" flag will not be garbage collected.
--print-gc-sections,--no-print-gc-sections— list all sections removed by garbage collection. The listing is printed on stderr. This option is only effective if garbage collection has been enabled via the--gc-sectionsoption. The default behaviour (of not listing the sections that are removed) can be restored by specifying--no-print-gc-sectionson the command line.--gc-keep-exported— when--gc-sectionsis enabled, this option prevents garbage collection of unused input sections that contain global symbols having default or protected visibility. This option is intended to be used for executables where unreferenced sections would otherwise be garbage collected regardless of the external visibility of contained symbols. Note that this option has no effect when linking shared objects since it is already the default behaviour. This option is only supported for ELF format targets.--print-output-format— print the name of the default output format (perhaps influenced by other command-line options). This is the string that would appear in an"OUTPUT_FORMAT"linker script command.--print-memory-usage— print used size, total size and used size of memory regions created with theMEMORYcommand. This is useful on embedded targets to have a quick view of amount of free memory. The format of the output has one headline and one line per region. It is both human readable and easily parsable by tools. Here is an example of an output:
Memory region Used Size Region Size %age Used
ROM: 256 KB 1 MB 25.00%
RAM: 32 B 2 GB 0.00%Note: if you want to find out about the memory usage of the linker itself, then the --stats option will do this. cute little memory check 🫶
--help— print a summary of the command-line options on the standard output and exit.--target-help— print a summary of all target-specific options on the standard output and exit.-Map=mapfile— print a link map to the file mapfile. See the description of the-Moption, above. If mapfile is just the character"-"then the map will be written to stdout.
Specifying a directory as mapfile causes the linker map to be written as a file inside the directory. Normally name of the file inside the directory is computed as the basename of the output file with .map appended. If however the special character "%" is used then this will be replaced by the full path of the output file. Additionally if there are any characters after the % symbol then .map will no longer be appended.
-o foo.exe -Map=bar [Creates ./bar]
-o ../dir/foo.exe -Map=bar [Creates ./bar]
-o foo.exe -Map=../dir [Creates ../dir/foo.exe.map]
-o ../dir2/foo.exe -Map=../dir [Creates ../dir/foo.exe.map]
-o foo.exe -Map=% [Creates ./foo.exe.map]
-o ../dir/foo.exe -Map=% [Creates ../dir/foo.exe.map]
-o foo.exe -Map=%.bar [Creates ./foo.exe.bar]
-o ../dir/foo.exe -Map=%.bar [Creates ../dir/foo.exe.bar]
-o ../dir2/foo.exe -Map=../dir/% [Creates ../dir/../dir2/foo.exe.map]
-o ../dir2/foo.exe -Map=../dir/%.bar [Creates ../dir/../dir2/foo.exe.bar]It is an error to specify more than one "%" character.
If the map file already exists then it will be overwritten by this operation.
--no-keep-memory—ldnormally optimizes for speed over memory usage by caching the symbol tables of input files in memory. This option tellsldto instead optimize for memory usage, by rereading the symbol tables as necessary. This may be required ifldruns out of memory space while linking a large executable.--no-undefined,-z defs— report unresolved symbol references from regular object files. This is done even if the linker is creating a non-symbolic shared library. The switch--[no-]allow-shlib-undefinedcontrols the behaviour for reporting unresolved references found in shared libraries being linked in. The effects of this option can be reverted by using"-z undefs".--allow-multiple-definition,-z muldefs— normally when a symbol is defined multiple times, the linker will report a fatal error. These options allow multiple definitions and the first definition will be used. first come, first served 💅--allow-shlib-undefined,--no-allow-shlib-undefined— allows or disallows undefined symbols in shared libraries. This switch is similar to--no-undefinedexcept that it determines the behaviour when the undefined symbols are in a shared library rather than a regular object file. It does not affect how undefined symbols in regular object files are handled.
The default behaviour is to report errors for any undefined symbols referenced in shared libraries if the linker is being used to create an executable, but to allow them if the linker is being used to create a shared library.
The reasons for allowing undefined symbol references in shared libraries specified at link time are that:
- A shared library specified at link time may not be the same as the one that is available at load time, so the symbol might actually be resolvable at load time.
- There are some operating systems, eg BeOS and HPPA, where undefined symbols in shared libraries are normal.
The BeOS kernel for example patches shared libraries at load time to select whichever function is most appropriate for the current architecture. This is used, for example, to dynamically select an appropriate memset function. iconic lore tbh 🌈
--error-handling-script=scriptname— okay so if you pass this, the linker will run scriptname every single time it hits an error 🙈. But rn only two kinds of error are actually supported: missing symbols and missing libraries. The script gets two arguments — the keyword"undefined-symbol"or"missing-lib", plus the name of the undefined symbol or the missing library. The whole idea? The script is supposed to be your little helpful bestie and suggest where that symbol or library might be hiding 🕵️. Once the script is done doing its thing, the normal linker error message still gets displayed. No skipping the sad part, bestie.
Heads up tho: whether this option even exists is controlled by a configure time switch, so it might just not be there in your particular implementation. Vibe check your build first 💅.
--no-undefined-version— normally, when a symbol has an undefined version, the linker just ignores it and moves on, no thoughts head empty. This option says absolutely not, symbols with undefined version are disallowed and a fatal error gets issued instead. 💀--default-symver— create and use a default symbol version (the soname) for unversioned exported symbols. Giving them a little default outfit ✨.--default-imported-symver— same energy but for unversioned imported symbols: create and use a default symbol version (the soname). 🫶--no-warn-mismatch— so normallyldthrows an error if you try to link together input files that are mismatched for some reason — maybe they were compiled for different processors, or for different endiannesses 👀. This option tellsldto just silently permit those possible errors. Use it with care, like only in cases where you've already taken some special action that ensures the linker errors are inappropriate.--no-warn-search-mismatch— normallyldgives you a warning if it finds an incompatible library during a library search. This option silences that warning 🤫.--no-whole-archive— turns off the effect of the--whole-archiveoption for any archive files that come after it. Not allowed within a--start-lib/--end-liboption pair.--no-link-mapless— reject archives that lack an index aka symbol map, for all the subsequent archives referred to on the command line. If one of those files shows up, you get a link error. This is the traditional behavior, iykyk.--noinhibit-exec— retain the executable output file whenever it's still usable. Normally the linker will not produce an output file if it hits errors during the link process; it exits without writing an output file when it issues any error whatsoever. This flag is like "no bestie, keep the file, I can work with this" 😤.-nostdlib— only search library directories that were explicitly specified on the command line. Library directories specified in linker scripts (including linker scripts specified on the command line) are ignored. Periodt. 🚫--oformat=output-format—ldmay be configured to support more than one kind of object file. If yourldis set up that way, you can use--oformatto specify the binary format for the output object file. Even whenldsupports alternative object formats, you usually don't need to specify this, becauseldshould be configured to produce the most usual format on each machine as the default output format. output-format is a text string — the name of a particular format supported by the BFD libraries. (You can list the available binary formats withobjdump -i.) The script commandOUTPUT_FORMATcan also specify the output format, but this option overrides it.--out-implib file— create an import library in file corresponding to the executable the linker is generating (eg. a DLL or ELF program). This import library (which should be called"*.dll.a"or"*.a"for DLLs) may be used to link clients against the generated executable. This behaviour makes it possible to skip a separate import library creation step (eg."dlltool"for DLLs) 🎀. This option is only available for the PE and ELF targetted ports of the linker.-pie,--pic-executable— create a position independent executable. Currently only supported on ELF platforms. Position independent executables are relocated by the dynamic linker to the virtual address the OS chooses for them, which can vary between invocations 🔄. They're markedET_DYNin the ELF file header, but they differ from shared libraries in a number of ways. In particular, defined symbols in a PIE by default can not be overridden by another object the way they can be in a shared library.-no-pie— create a position dependent executable. This is the default. Chill, lowkey boring, but reliable 💜.-qmagic— this option is ignored for Linux compatibility.-Qy— this option is ignored for SVR4 compatibility.--relax,--no-relax— an option with machine dependent effects. Only supported on a few targets, so check before you get attached.
On some platforms the --relax option performs target specific, global optimizations that become possible when the linker resolves addressing in the program — like relaxing address modes, synthesizing new instructions, selecting shorter versions of current instructions, and combining constant values. It's giving glow up for your addressing ✨.
On some platforms these link time global optimizations may make symbolic debugging of the resulting executable impossible 😭. This is known to be the case for the Matsushita MN10200 and MN10300 family of processors.
On platforms where the feature is supported, --no-relax will disable it.
On platforms where the feature is not supported, both --relax and --no-relax are accepted, but ignored. They're just there. Being cute. Doing nothing 🙈.
--retain-symbols-file=filename— retain only the symbols listed in the file filename, discarding all the others. filename is simply a flat file, with one symbol name per line. This option is especially useful in environments (such as VxWorks) where a large global symbol table is accumulated gradually, to conserve run-time memory 👑
--retain-symbols-file does not discard undefined symbols, or symbols needed for relocations. Those stay, bestie.
You may only specify --retain-symbols-file once in the command line. It overrides -s and -S.
-rpath=dir— add a directory to the runtime library search path. This is used when linking an ELF executable with shared objects. All-rpatharguments are concatenated and passed to the runtime linker, which uses them to locate shared objects at runtime. Literally passing notes to the runtime linker 📝.
The -rpath option is also used when locating shared objects which are needed by shared objects explicitly included in the link; see the description of the -rpath-link option. Searching -rpath in this way is only supported by native linkers and cross linkers which have been configured with the --with-sysroot option.
If -rpath is not used when linking an ELF executable, the contents of the environment variable LD_RUN_PATH will be used if it is defined.
The -rpath option may also be used on SunOS. By default, on SunOS, the linker will form a runtime search path out of all the -L options it is given. If a -rpath option is used, the runtime search path will be formed exclusively using the -rpath options, ignoring the -L options. This can be useful when using gcc, which adds many -L options which may be on NFS mounted file systems.
For compatibility with other ELF linkers, if the -R option is followed by a directory name, rather than a file name, it is treated as the -rpath option.
-rpath-link=dir— when using ELF or SunOS, one shared library may require another. This happens when an"ld -shared"link includes a shared library as one of the input files.
When the linker encounters such a dependency while doing a non-shared, non-relocatable link, it will automatically try to locate the required shared library and include it in the link, if it's not included explicitly. In such a case, several directories are searched as described below. The -rpath-link option specifies the first set of directories to search. This option may specify a sequence of directory names either by providing a list of names separated by colons, or by appearing multiple times.
The tokens $ORIGIN and $LIB can appear in these search directories. They will be replaced by the full path to the directory containing the program or shared object in the case of $ORIGIN, and either lib — for 32-bit binaries — or lib64 — for 64-bit binaries — in the case of $LIB.
The alternative form of these tokens — ${ORIGIN} and ${LIB} — can also be used. The token $PLATFORM is not supported. Sorry bestie, that one's not invited to the party.
The --rpath-link option should be used with caution as it overrides the search path that may have been hard compiled into a shared library. In such a case it's possible to unintentionally use a different search path than the runtime linker would have used. 🚨
When additional shared libraries are required, the linker will search directories in the order listed below in order to find them. Note however that this only applies to additional libraries needed to satisfy already included shared libraries. It does not apply to libraries that are included via the -l command line option. Searches for -l libraries are only conducted in directories specified by the -L option.
- Any directories specified by
-rpath-linkoptions. - Any directories specified by
-rpathoptions. The difference between-rpathand-rpath-linkis that directories specified by-rpathoptions are included in the executable and used at runtime, whereas the-rpath-linkoption is only effective at link time. Searching-rpathin this way is only supported by native linkers and cross linkers which have been configured with the--with-sysrootoption. - On an ELF system, for native linkers, if the
-rpathand-rpath-linkoptions were not used, search the contents of the environment variableLD_RUN_PATH. - On SunOS, if the
-rpathoption was not used, search any directories specified using-Loptions. - For a native linker, search the contents of the environment variable
LD_LIBRARY_PATH. - For a native ELF linker, the directories in
DT_RUNPATHorDT_RPATHof a shared library are searched for shared libraries needed by it. TheDT_RPATHentries are ignored ifDT_RUNPATHentries exist.
- Okay for a linker on a Linux system: if
/etc/ld.so.confexists, then the list of directories found inside that file. 🎀 Tiny note though bestie — the path to this file gets prefixed with the "sysroot" value, if that's defined, and then any "prefix" string if the linker was configured with the--prefix=<path>option. - For a native linker on a FreeBSD system: whatever directories the
_PATH_ELF_HINTSmacro says, which is defined in theelf-hints.hheader file. 🌸 - Any directories you specified with a "SEARCH_DIR" command in a linker script given on the command line — and yes that includes scripts given by
-T(but not-dT). Noted. 💅 - The default directories, which are normally
/liband/usr/lib. The OGs. 🫶 - Any directories specified by a plugin's
LDPT_SET_EXTRA_LIBRARY_PATH. Plugins stay doing the most fr. - Any directories specified by a "SEARCH_DIR" command in a default linker script.
⚠️ But on Linux-based systems there's an extra lil caveat okay: if the--as-neededoption is active and a shared library is located that would normally satisfy the search and this library does not have aDT_NEEDEDtag forlibc.so, and there's another shared library later on in the set of search directories which also satisfies the search and that second shared library does have aDT_NEEDEDtag forlibc.so— then the second library gets selected instead of the first. Plot twist. 😭
And if the required shared library is not found at all? The linker issues a warning and just keeps going with the link. It's giving "we move". 💀
--section-ordering-file=script— this one augments the current linker script with extra mapping of input sections to output sections. This file must use the same syntax forSECTIONSas normal linker scripts use, but it should not do anything other than place input sections into output sections.@pxref{SECTIONS}
A second constraint on the section ordering script: it can only reference output sections that are already defined by whichever linker script is currently in use (ie the default linker script, or a script specified on the command line). But here's the slay — the benefit of the section ordering script is that the input sections get mapped to the start of the output sections, so it can guarantee the ordering of sections inside the output section. ✨
For example, imagine the default linker script looks like this:
SECTIONS {
.text : { *(.text.hot) ; *(.text .text.*) }
.data : { *(.data.big) ; *(.data .data.*) }
}Then if a section ordering file like this is used:
.text : { *(.text.first) ; *(.text.z*) }
.data : { foo.o(.data.first) ; *(.data.small) }This would be equivalent to a linker script like this:
SECTIONS {
.text : { *(.text.first) ; *(.text.z*) ; *(.text.hot) ; *(.text .text.*) }
.data : { foo.o(.data.first) ; *(.data.small) ; *(.data.big) ; *(.data .data.*) }
}And the advantage of the section ordering file? It can order the sections that actually matter to you without having to worry about any other sections, or memory regions, or anything else. Main character energy tbh. 👑
-shared-Bshareable— create a shared library. Currently this is only supported on ELF, XCOFF and SunOS platforms. On SunOS, the linker will automatically create a shared library if the-eoption is not used and there are undefined symbols in the link. Periodt.--sort-common--sort-common=ascending--sort-common=descending— this tellsldto sort the common symbols by alignment, in ascending or descending order, when it places them into the appropriate output sections. The symbol alignments considered are sixteen-byte or larger, eight-byte, four-byte, two-byte, and one-byte. Why? To prevent gaps between symbols caused by alignment constraints. 🧚 And if no sorting order is specified, then descending order is assumed. (She has a default. Love that for her.)--sort-section=name— this one appliesSORT_BY_NAMEto all wildcard section patterns in the linker script.--sort-section=alignment— this one appliesSORT_BY_ALIGNMENTto all wildcard section patterns in the linker script.--spare-dynamic-tags=count— specifies how many empty slots to leave in the.dynamicsection of ELF shared objects. Empty slots may be needed by post-processing tools, like the prelinker. The default is5. Five lil vacancies, reserved, no subletting. 🎀--split-by-file[=size]— similar to--split-by-relocbut it creates a new output section for each input file when size is reached. size defaults to a size of1if it isn't given. 🦋--split-by-reloc[=count]— tries to create extra sections in the output file so that no single output section in the file contains more than count relocations. This is useful when generating huge relocatable files for downloading into certain real time kernels with the COFF object file format, because COFF cannot represent more than65535relocations in a single section. 😭
Note that this will fail to work with object file formats which do not support arbitrary sections.
Also: the linker will not split up individual input sections for redistribution, so if a single input section contains more than count relocations, one output section will contain that many relocations. It is what it is. count defaults to a value of 32768.
--stats[=filename]— compute and display statistics about the linker's operation, like execution time and memory usage. 📊
If the optional filename argument is not supplied then only basic information is reported, and it's sent to the standard error output stream. If the filename argument is supplied then extended information is written to the named file. If filename is set to just the - symbol, then the extended information is sent to the standard output stream. And if filename starts with +, then the file is opened in append mode rather than overwrite mode. Tiny detail, big difference. 💅
If the -Map option has been enabled then the information is also recorded in the map file as well. Note: if both the --stats option and the -Map options have been given filename arguments and they match, then the information will only be written out once, not twice. No dupes allowed.
If the LD_STATS environment variable is defined then this behaves like the --stats option. If the variable's value is a string then that will be used as the name of a file into which the information should be recorded. Otherwise the information will be sent to the standard output stream. Using the environment variable lets stats be recorded without having to alter the linker's command line. Note: if both the environment variable and the --stats option are used, then the --stats option takes precedence. She said the flag wins, sorry babe. 🙈
The extended information reported includes the CPU time used and, if the getrusage() system library call is available, then maximum set size and the user and system run times as well. In addition, if the mallinfo or mallinfo2 system library calls are available then the total memory usage is reported.
The information is displayed for individual parts of the linking process, which are referred to as phases. Note that individual phases can contain or overlap with each other, so it should not be assumed that the overall resources used by the linker is the sum of the resources used by the individual phases. Math does not math here, bestie. ⚠️
In addition the information is also reported for a special phase called ALL, which covers the entire linking process. 🌈
When extended information is being reported, the linker version, command line arguments and linker start time are also included. This makes it easier to handle the situation where multiple links are being invoked by a build system, and to identify exactly which arguments were responsible for producing the statistics that are reported. Detective work, honestly. 🔍
The extended output looks something like this:
Stats: linker version: (GNU Binutils) 2.44.50.20250401
Stats: linker started: Wed Apr 2 09:36:41 2025
Stats: args: ld -z norelro -z nomemory-seal -z no-separate-code -o a.out [...]
Stats: phase cpu time rss user time system time memory
Stats: name (microsec) (KiB) (seconds) (seconds) (KiB)
Stats: ALL 390082 217740 0 0 25219440
Stats: ctf processing 12 0 0 0 0
Stats: string merge 1324 0 0 0 406544
Stats: parsing 349 288 0 0 119792
Stats: plugins 1 0 0 0 0
Stats: processing files 259616 214524 0 0 31569120
Stats: write 116493 0 0 0 48096--no-stats— disables the reporting of usage statistics, should it have been enabled via the--statscommand line option or theLD_STATSenvironment variable. Off switch. Say less. 💜--sysroot=directory— use directory as the location of the sysroot, overriding the configure-time default. This option is only supported by linkers that were configured using--with-sysroot. 🤷♀️--task-link— this is used by COFF/PE-based targets to create a task-linked object file where all of the global symbols have been converted to statics. Glow down, honestly.--traditional-format— for some targets, the output oflddiffers in some ways from the output of some existing linker. This switch requestsldto use the traditional format instead. Old-school cool. 💖
For example, on SunOS, ld combines duplicate entries in the symbol string table. This can reduce the size of an output file with full debugging information by over 30 percent. Unfortunately, the SunOS dbx program can not read the resulting program (gdb has no trouble). The --traditional-format switch tells ld to not combine duplicate entries. Trade-offs, bestie, trade-offs. 😭
--section-start=sectionname=org— plops a section in the output file at the exact absolute addressorggave you. You can use this option as many times as you want to place multiple sections.orghas to be a single hexadecimal integer; for compatibility with other linkers, you're allowed to skip the leading0xthat hex values usually wear. Note: there should be no white space betweensectionname, the equals sign"=", andorg. Like, none. Zip. Zero. 🫶--image-base=org— this one's a shapeshifter depending on your format, bestie. When you're using ELF, it's the same as-Ttext-segment, and both of those options effectively set the base address of the ELF executable. When you're using PE, it uses the value as the base address of your program or dll. That's the lowest memory location that gets used when your program or dll is loaded. To cut down on relocating and to boost the performance of your dlls, each one should have a unique base address and should not overlap any other dlls. The default is0x400000for executables, and0x10000000for dlls. ✨-Tbss=org,-Tdata=org,-Ttext=org— same as--section-start, but with".bss",".data"or".text"as thesectionname. Convenience era. 💅-Ttext-segment=org— when creating an ELF executable, this sets the address of the first byte of the first segment. Heads up though: when-pieis used together with-Ttext-segment=org, the output executable gets markedET_EXECso that the address of the first byte of the text segment is guaranteed to beorgat run time. Locked in. 🔒-Trodata-segment=org— when you're creating an ELF executable or shared object for a target where the read-only data lives in its own segment separate from the executable text, this sets the address of the first byte of the read-only data segment.-Tldata-segment=org— when creating an ELF executable or shared object for the x86-64 medium memory model, this sets the address of the first byte of the ldata segment.--unresolved-symbols=method— decides how unresolved symbols get handled. There are four possible values formethod, and they are:ignore-all— do not report any unresolved symbols. living your truth, ignoring the problem 🙈report-all— report all unresolved symbols. This is the default.ignore-in-object-files— report unresolved symbols that are contained in shared libraries, but ignore them if they come from regular object files.ignore-in-shared-libs— report unresolved symbols that come from regular object files, but ignore them if they come from shared libraries. This can be useful when creating a dynamic binary and you already know that all the shared libraries it should be referencing are included on the linker's command line.
The behaviour for shared libraries on their own can also be controlled by the --[no-]allow-shlib-undefined option.
Normally the linker generates an error message for each reported unresolved symbol, but the --warn-unresolved-symbols option can switch this to a warning instead.
--dll-verbose,--verbose[=NUMBER]— shows you the version number forldand lists the linker emulations that are supported. It also shows which input files can and cannot be opened, and shows the linker script the linker is using. If the optionalNUMBERargument is> 1, plugin symbol status gets displayed too. maximum transparency, we love to see it 🔍--version-script=version-scriptfile— names the version script you want to hand the linker. This is typically used when making shared libraries, to specify extra info about the version hierarchy for the library being created. It's only fully supported on ELF platforms that support shared libraries; peek at VERSION for that. It's partially supported on PE platforms, which can use version scripts to filter symbol visibility in auto-export mode: any symbols marked local in the version script will not be exported.--warn-common— warns you when a common symbol gets combined with another common symbol, or with a symbol definition. Unix linkers allow this kinda sloppy practice, but linkers on some other operating systems do not. This option lets you find potential problems from combining global symbols. Unfortunately, some C libraries use this practice, so you may get warnings about symbols in the libraries as well as in your programs. not the library catching strays 😭
There are three kinds of global symbols, illustrated here with C examples:
int i = 1;— a definition, which goes in the initialized data section of the output file.extern int i;— an undefined reference, which does not allocate space. There must be either a definition or a common symbol for the variable somewhere.int i;— a common symbol. If there are only (one or more) common symbols for a variable, it goes in the uninitialized data area of the output file. The linker merges multiple common symbols for the same variable into a single symbol. If they're of different sizes, it picks the largest size. The linker turns a common symbol into a declaration if there is a definition of the same variable.
The --warn-common option can produce five kinds of warnings. Each warning is a pair of lines: the first describes the symbol just encountered, and the second describes the previous symbol encountered with the same name. One or both of the two symbols will be a common symbol.
- Turning a common symbol into a reference, because there is already a definition for the symbol.
<file>(<section>): warning: common of `<symbol>'
overridden by definition
<file>(<section>): warning: defined here- Turning a common symbol into a reference, because a later definition for the symbol is encountered. This is the same as the previous case, except that the symbols are encountered in a different order.
<file>(<section>): warning: definition of `<symbol>'
overriding common
<file>(<section>): warning: common is here- Merging a common symbol with a previous same-sized common symbol.
<file>(<section>): warning: multiple common
of `<symbol>'
<file>(<section>): warning: previous common is here- Merging a common symbol with a previous larger common symbol.
<file>(<section>): warning: common of `<symbol>'
overridden by larger common
<file>(<section>): warning: larger common is here- Merging a common symbol with a previous smaller common symbol. This is the same as the previous case, except that the symbols are encountered in a different order.
<file>(<section>): warning: common of `<symbol>'
overriding smaller common
<file>(<section>): warning: smaller common is here--warn-constructors— warns you if any global constructors are used. This is only useful for a few object file formats. For formats like COFF or ELF, the linker literally cannot detect the use of global constructors. it's giving "I tried my best" 🫠--warn-execstack,--warn-execstack-objects,--no-warn-execstack— on ELF platforms the linker may generate warning messages if it's asked to create an output file containing an executable stack. There are three possible states:- Do not generate any warnings.
- Always generate warnings, even if the executable stack is requested via the
-z execstackcommand line option. - Only generate a warning if an object file requests an executable stack, but not if the
-z execstackoption is used.
The default state depends on how the linker was configured when it was built. The --no-warn-execstack option always puts the linker into the no-warnings state. The --warn-execstack option puts the linker into the warn-always state. The --warn-execstack-objects option puts the linker into the warn-for-object-files-only state.
Note: ELF format input files can specify that they need an executable stack by having a .note.GNU-stack section with the executable bit set in its section flags. They can specify that they do not need an executable stack by having the same section, but without the executable flag bit set. If an input file does not have a .note.GNU-stack section then the default behaviour is target specific. For some targets, the absence of such a section implies that an executable stack is required. This is often a problem for hand crafted assembler files. hand crafted assembler stays causing chaos fr fr 💀
--error-execstack,--no-error-execstack— if the linker is about to generate a warning message about an executable stack, then the--error-execstackoption will instead change that warning into an error. Heads up though — this option does not change the linker's execstack warning generation state. Use--warn-execstackor--warn-execstack-objectsto set a specific warning state.
The --no-error-execstack option restores the default behaviour of generating warning messages.
--warn-multiple-gp— warns you if multiple global pointer values are required in the output file. This is only meaningful for certain processors, like the Alpha. Specifically: some processors put large-valued constants in a special section. A special register (the global pointer) points into the middle of this section, so constants can be loaded efficiently via a base-register relative addressing mode. Since the offset in base-register relative mode is fixed and relatively small (e.g., 16 bits), this limits the maximum size of the constant pool. So in large programs, it's often necessary to use multiple global pointer values to be able to address all possible constants. This option makes a warning get issued whenever that case occurs. niche processor lore, iykyk 👑--warn-once— only warn once for each undefined symbol, rather than once per module which refers to it. we are NOT doing the spam ✋--warn-rwx-segments,--no-warn-rwx-segments— warns you if the linker creates a loadable, non-zero sized segment that has all three of the read, write and execute permission flags set. A segment like that represents a potential security vulnerability. On top of that, warnings will also be generated if a thread local storage segment is created with the execute permission flag set, regardless of whether or not it has the read and/or write flags set. security girlies, this one's for you 🚨
okay so back to it — these warnings? enabled by default, bestie. turn 'em off with --no-warn-rwx-segments, turn 'em back on with --warn-rwx-segments. simple as. 💅
--error-rwx-segments & --no-error-rwx-segments 🚨
so if the linker is about to drop a warning message about an executable, writeable segment, or an executable TLS segment, then --error-rwx-segments is the drama queen that upgrades that lil warning into a full-on ERROR instead. meanwhile --no-error-rwx-segments just restores the default vibe of "warning message, that's it." 😌
heads up —--error-rwx-segmentsdoes not turn on warnings about these segments by itself. those warnings are either enabled by default (if the linker was configured that way), or you flip them on yourself via the--warn-rwx-segmentscommand line option. iykyk. ✨
--warn-section-align 🎯
warns you if the address of an output section gets moved because of alignment. typically the alignment is set by an input section. and the address is only changed if it wasn't explicitly specified — that is, if the SECTIONS command didn't give that section a start address. got it? periodt. 💅
--warn-textrel 📝
warns if the linker adds DT_TEXTREL to a position-independent executable or shared object. short. sweet. iconic. 🍓
--warn-alternate-em 👀
warns if an object has alternate ELF machine code. the way that's the whole option... 💀
--warn-unresolved-symbols 💌
so when the linker is about to report an unresolved symbol (see the --unresolved-symbols option), it'll normally throw a whole error at you. this option makes it go "ok but gentle" and drop a warning instead. 🦋
--error-unresolved-symbols 😤
restores the linker's default behaviour — which is generating errors when it's reporting unresolved symbols. we're back on our no-nonsense bs.
--whole-archive 📦
for each archive mentioned on the command line after --whole-archive, include every object file in the archive in the link — instead of searching the archive for just the required object files. normally this is used to turn an archive file into a shared library, forcing every object to be included in the resulting shared library. and yes bestie, this option can be used more than once. ✨
this option is not allowed within a --start-lib/--end-lib option pair. 🚫
two lil notes for when you use this option from gcc:
- gcc doesn't know about this option, so you have to use
-Wl,-whole-archive. - don't forget to use
-Wl,-no-whole-archiveafter your list of archives — because gcc is gonna add its own list of archives to your link, and you probably don't want this flag affecting those too. lowkey important fr fr. 💖
--link-mapless 🗺️
accepts archives that lack an index (aka a symbol map) for all the subsequent archives referred on the command line. if it's missing, that index gets made internally on the fly at a performance cost. 🥲 this is the default, btw. 🎀
--wrap=symbol 🎁
uses a wrapper function for symbol. any undefined reference to symbol gets resolved to __wrap_symbol. any undefined reference to __real_symbol gets resolved to symbol. bestie this is literally how you cosplay as a system function. 🌸
this can be used to provide a wrapper for a system function. the wrapper function should be called __wrap_symbol. if it wishes to call the system function, it should call __real_symbol.
here's a trivial example:
void *
__wrap_malloc (size_t c)
{
printf ("malloc called with %zu\n", c);
return __real_malloc (c);
}if you link other code with this file using --wrap malloc, then all calls to malloc will call the function __wrap_malloc instead. and the call to __real_malloc inside __wrap_malloc will call the real malloc function. 💅
you might also wanna provide a __real_malloc function so that links without the --wrap option will still succeed. but — pls listen — if you do this, do not put the definition of __real_malloc in the same file as __wrap_malloc. because if you do, the assembler may resolve the call before the linker even gets a chance to wrap it to malloc. 💀
and remember: only undefined references get replaced by the linker. so translation unit internal references to symbol are not resolved to __wrap_symbol. check this next one — the call to f inside g is not resolved to __wrap_f:
int
f (void)
{
return 123;
}
int
g (void)
{
return f();
}--eh-frame-hdr & --no-eh-frame-hdr 🗂️
requests (--eh-frame-hdr) or suppresses (--no-eh-frame-hdr) the creation of the .eh_frame_hdr section and the ELF PT_GNU_EH_FRAME segment header. pick your fighter. 🥊
--no-ld-generated-unwind-info 🌈
requests creation of .eh_frame unwind info for linker generated code sections like PLT. this option is on by default if linker generated unwind info is supported. 💖
--discard-sframe 🗑️
discards .sframe stack trace info from the output. it also prohibits the creation of SFrame stack trace data for linker generated code sections like PLT. this option is off by default. 🫶
--enable-new-dtags & --disable-new-dtags 🏷️
so this linker can create the new dynamic tags in ELF — but the older ELF systems may not understand them. 😭 if you specify --enable-new-dtags, the new dynamic tags will be created as needed and the older dynamic tags get omitted. if you specify --disable-new-dtags, no new dynamic tags get created. by default, the new dynamic tags are not created. and note — those options are only available for ELF systems. 💅
--hash-size=number 🔢
sets the default size of the linker's hash tables to a prime number close to number. bumping this value up can cut down the time it takes the linker to do its thing — but at the expense of memory. and dropping it down saves memory at the expense of speed. ✨ the default is 4051 under normal circumstances, and 1021 if the --reduce-memory-overheads command line option is used. 👑
--hash-style=style 🎀
sets the type of the linker's hash table(s). style can be:
sysv— for the classic ELF.hashsectiongnu— for the new style GNU.gnu.hashsectionboth— for both the classic ELF.hashand new style GNU.gnu.hashhash tables
the default depends on how the linker was configured, but for most Linux based systems it'll be both. 💖
--compress-debug-sections=... 🗜️
on ELF platforms, these options control how DWARF debug sections get compressed using zlib.
--compress-debug-sections=none— doesn't compress DWARF debug sections. it's giving "leave me and my sections alone" energy. 🙈--compress-debug-sections=zlib-gnu— compresses DWARF debug sections and renames them to begin with.zdebuginstead of.debug. 🏷️--compress-debug-sections=zlib-gabi— also compresses them, but rather than renaming, it sets theSHF_COMPRESSEDflag in the sections' headers. 💅
--compress-debug-sections=zlib is just an alias for --compress-debug-sections=zlib-gabi. 🫶
--compress-debug-sections=zstd compresses DWARF debug sections using zstd. 🔥
hey, heads up — this option overrides any compression in input debug sections. so if a binary is linked with --compress-debug-sections=none, for example, then any compressed debug sections in input files will be uncompressed before they're copied into the output binary. 😭
the default compression behaviour varies depending on the target involved and the configure options used to build the toolchain. you can suss out the default by examining the output from the linker's --help option. 🌈
--reduce-memory-overheads 🧠
this option reduces memory requirements at ld runtime — at the expense of linking speed. 🥲 it was introduced to select the old O(n^2) algorithm for link map file generation, rather than the new O(n) algorithm, which uses about 40% more memory for symbol storage. 💀
another effect of the switch is to set the default hash table size to 1021 — which again saves memory at the cost of lengthening the linker's run time. this is not done, however, if the --hash-size switch has already been used. 💅
the --reduce-memory-overheads switch may also be used to enable other tradeoffs in future versions of the linker. 🌸
--max-cache-size=size 💾
ld normally caches the relocation information and symbol tables of input files in memory with unlimited size. this option sets the maximum cache size to size. note — if the --no-keep-memory command line option has been used, then the linker acts as if the maximum cache size has been set to 0 — ie nothing is retained. 😭
--build-id & --build-id=style 🆔
requests the creation of a .note.gnu.build-id ELF note section, or a .buildid COFF section. the contents of the note are unique bits identifying this linked file. style can be:
uuid— use 128 random bitssha1— use a 160-bit SHA1 hashmd5— use a 128-bit MD5 hashxx— use a 128-bit XXHASH on the normative parts of the output contents0xhexstring— use a chosen bit string specified as an even number of hexadecimal digits (-and:characters between digit pairs are ignored) 🎀
if style is omitted, sha1 is used.
the md5, sha1, and xx styles produce an identifier that's always the same in an identical output file, but almost certainly unique among all nonidentical output files. it is not intended to be compared as a checksum for the file's contents. a linked file may be changed later by other tools, but the build ID bit string identifying the original linked file does not change. ✨
passing none for style disables the setting from any --build-id options earlier on the command line. 🫶
--package-metadata=JSON— this one asks the linker to cook up a.note.packageELF note section, and the note's contents are straight-up JSON, per the package metadata spec 🫶. Want the lore? It's athttps://systemd.io/ELF_PACKAGE_METADATA/. The JSON argument also supports percent-encoding, and these specific%[string]escapes (where string is the name from HTML's Named Character References):%[comma]gives you,,%[lbrace]gives{,%[quot]gives",%[rbrace]gives}, and%[space]gives an actual space character ✨. And if the JSON argument is missing or empty? That disables the creation of the metadata note — but only if a previous--package-metadataoption had already turned one on. Also, if your linker was built with libjansson, that JSON string gets validated for real. No cap. 💅
Okay so boom, plot twist — the PE linker is built different 😤 and it supports the -shared option, which makes the output a dynamically linked library (DLL) instead of a regular ol' executable. And bestie, you should name your output *.dll when you use this option, okay? Name it right 🎀. On top of that, the linker fully supports standard *.def files, and you can drop them on the linker command line just like an object file — and honestly it should come before the archives it exports symbols from, so those symbols actually get linked in, exactly like a normal object file would. iykyk 🔥
So in addition to the options that every target shares, the PE linker has its own extra command-line options that are PE-only. And for the ones that take values? You can separate the option from its value with either a space or an equals sign, your call 🌸.
--add-stdcall-alias— if you pass this, symbols with a stdcall suffix (@nn) get exported both as-is and with the suffix stripped off. Two for one, iconic 👑. [This option is specific to PE targeted ports of the linker]--base-filefile — uses file as the name of the file where it saves the base addresses of every relocation needed to generate DLLs withdlltool. [This option is specific to PE targeted ports of the linker]--dll— build a DLL instead of a regular executable 🦋. You could also use-shared, or just declare aLIBRARYinside a given.deffile, whichever vibe you're on. [This option is specific to PE targeted ports of the linker]--enable-long-section-names/--disable-long-section-names— so the PE variants of the COFF object format added an extension that lets section names go past eight characters, which is the normal COFF limit. By default these longer names are only allowed inside object files, because fully-linked executable images don't carry the COFF string table that's needed to support them 📝. But as a GNU extension, you can allow long names in executable images too, or (probably pointlessly!) disallow them in object files, by flipping these two options. Heads up though: executable images built with these long section names are slightly non-standard, since they're carrying a string table around, and they may produce confusing output when inspected with non-GNU PE-aware tools like file viewers and dumpers 💀. BUT — plot twist — GDB relies on PE long section names to find Dwarf-2 debug info sections in an executable image at runtime. So if neither option is given on the command line,ldwill enable long section names — overriding the default and technically correct behaviour — whenever it spots debug information while linking an executable image and it's not stripping symbols. [This option is specific to PE targeted ports of the linker]--enable-stdcall-fixup/--disable-stdcall-fixup— this is the "fuzzy linking" feature, and it's giving matchmaker energy 💖. If the link finds a symbol it can't resolve, it goes looking for another defined symbol that differs only in the format of the symbol name (cdecl vs stdcall) and resolves by linking to that match. For example, the undefined symbol_foomight get linked to the function_foo@12, or the undefined_bar@16might get linked to the function_bar. When the linker does this it prints a warning, because normally it should have failed the link — but sometimes import libraries generated from third-party DLLs legitimately need this to be usable. If you specify--enable-stdcall-fixup, the feature is fully on and warnings are not printed. If you specify--disable-stdcall-fixup, the feature is off and these mismatches get treated as errors, periodt. [This option is specific to PE targeted ports of the linker]--leading-underscore/--no-leading-underscore— for most targets the default symbol prefix is an underscore, and that's defined in the target's description. With this option you can disable or enable that default underscore symbol-prefix. [This option is specific to PE targeted ports of the linker]--export-all-symbols— pass this and every global symbol in the objects used to build a DLL gets exported by the DLL 🎉. Note that this is actually the default if there otherwise wouldn't be any exported symbols at all. But when symbols are explicitly exported via DEF files, or implicitly exported via function attributes, the default flips to not exporting anything else unless you give this option. And listen, some things stay off the guest list no matter what: the symbolsDllMain@12,DllEntryPoint@0,DllMainCRTStartup@12, andimpure_ptrwill not be automatically exported. Symbols imported from other DLLs won't be re-exported either, and neither will symbols that specify the DLL's internal layout — like ones beginning with_head_or ending with_iname. Also no symbols fromlibgcc,libstd++,libmingw32, orcrtX.oget exported. Symbols whose names begin with__rtti_or__builtin_are skipped too, to help C++ DLLs behave (and this is the correct call). And finally, there's an extensive list of cygwin-private symbols that aren't exported (obviously this one only applies when you're building DLLs for cygwin targets). Those cygwin-excludes are:_cygwin_dll_entry@12,_cygwin_crt0_common@8,_cygwin_noncygwin_dll_entry@12,_fmode,_impure_ptr,cygwin_attach_dll,cygwin_premain0,cygwin_premain1,cygwin_premain2,cygwin_premain3, andenviron. [This option is specific to PE targeted ports of the linker]--exclude-symbolssymbol,symbol,... — hands you a list of symbols that should not be automatically exported 🚫. The symbol names can be delimited by commas or colons, dealer's choice. [This option is specific to PE targeted ports of the linker]--exclude-all-symbols— says no symbols should be automatically exported. At all. None. [This option is specific to PE targeted ports of the linker]--file-alignment— sets the file alignment. Sections in the file will always start at file offsets that are multiples of this number. It defaults to512. [This option is specific to PE targeted ports of the linker]--heapreserve /--heapreserve,commit — tells it how many bytes of memory to reserve (and optionally commit) for this program's heap 🍓. The default is 1MB reserved, 4K committed. [This option is specific to PE targeted ports of the linker]--kill-at— pass this and the stdcall suffixes (@nn) get stripped from symbols before they're exported. Say bye 👋. [This option is specific to PE targeted ports of the linker]--large-address-aware— sets the appropriate bit in theCharacteristicsfield of the COFF header, signalling that this executable supports virtual addresses greater than 2 gigabytes 💪. This one should be used together with the/3GBor/USERVA=value megabytes switch in the[operating systems]section of theBOOT.INI. Otherwise, that bit literally has no effect. [This option is specific to the i386 PE targeted port of the linker]--disable-large-address-aware— undoes the effect of a previous--large-address-awareoption. Super useful if--large-address-awareis always set by your compiler driver (looking at you, Cygwin gcc 🙈) and your executable doesn't actually support virtual addresses greater than 2 gigabytes. [This option is specific to the i386 PE targeted port of the linker]--major-image-versionvalue — sets the major number of theimage version. Defaults to1. [This option is specific to PE targeted ports of the linker]--major-os-versionvalue — sets the major number of theos version. Defaults to4. [This option is specific to PE targeted ports of the linker]--major-subsystem-versionvalue — sets the major number of thesubsystem version. Defaults to4. [This option is specific to PE targeted ports of the linker]--minor-image-versionvalue — sets the minor number of theimage version. Defaults to0. [This option is specific to PE targeted ports of the linker]--minor-os-versionvalue — sets the minor number of theos version. Defaults to0. [This option is specific to PE targeted ports of the linker]--minor-subsystem-versionvalue — sets the minor number of thesubsystem version. Defaults to0. [This option is specific to PE targeted ports of the linker]--output-deffile — the linker will create file, and inside it will be a DEF file corresponding to the DLL it's generating ✨. That DEF file (which should be called*.def, bestie) can be used to create an import library withdlltool, or used as a reference for automatically or implicitly exported symbols. [This option is specific to PE targeted ports of the linker]--enable-auto-image-base/--enable-auto-image-base=value — automatically picks the image base for DLLs, optionally starting from base value, unless one is specified with the--image-baseargument instead. By hashing the dllname to cook up unique image bases for each DLL, it dodges in-memory collisions and relocations that could otherwise slow your program down. Main character efficiency 💅. [This option is specific to PE targeted ports of the linker]--disable-auto-image-base— nope, no automatically generated unique image base. If there's no user-specified image base (--image-base), then it just uses the platform default. [This option is specific to PE targeted ports of the linker]--dll-search-prefixstring — when linking dynamically to a dll that has no import library, this makes it search for<string><basename>.dllin preference tolib<basename>.dll🔍. This behaviour makes it easy to tell DLLs built for the various "subplatforms" apart — native, cygwin, uwin, pw, etc. For instance, cygwin DLLs typically use--dll-search-prefix=cyg. [This option is specific to PE targeted ports of the linker]--enable-auto-import— okay bestie, this one does sophisticated linking of"_symbol"to"__imp__symbol"for DATA imports from DLLs, so you can bypass the dllimport mechanism on the user side and reference unmangled symbol names. [This option is specific to PE targeted ports of the linker]
The following remarks pertain to the original implementation of the feature and are obsolete nowadays for Cygwin and MinGW targets.
Note: Use of the 'auto-import' extension will cause the text section of the image file to be made writable. This does not conform to the PE-COFF format specification published by Microsoft.
Note — use of the 'auto-import' extension will also cause read only data which would normally be placed into the.rdatasection to be placed into the.datasection instead. This is in order to work around a problem with consts that is described here:http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
Using 'auto-import' generally will 'just work' -- but sometimes you may see this message:
"variable '<var>' can't be auto-imported. Please read the
documentation for ld's "--enable-auto-import" for details."This message occurs when some (sub)expression accesses an address ultimately given by the sum of two constants (Win32 import tables only allow one). Instances where this may occur include accesses to member fields of struct variables imported from a DLL, as well as using a constant index into an array variable imported from a DLL. Any multiword variable (arrays, structs, long long, etc) may trigger this error condition. However, regardless of the exact data type of the offending exported variable, ld will always detect it, issue the warning, and exit.
There are several ways to address this difficulty, regardless of the data type of the exported variable:
One way is to use --enable-runtime-pseudo-reloc switch. This leaves the task of adjusting references in your client code for runtime environment, so this method works only when runtime environment supports this feature.
A second solution is to force one of the 'constants' to be a variable -- that is, unknown and un-optimizable at compile time. For arrays, there are two possibilities: a) make the indexee (the array's address) a variable, or b) make the 'constant' index a variable. Thus:
extern type extern_array[];
extern_array[1] -->
{ volatile type *t=extern_array; t[1] }or
extern type extern_array[];
extern_array[1] -->
{ volatile int t=1; extern_array[t] }For structs (and most other multiword data types) the only option is to make the struct itself (or the long long, or the ...) variable:
extern struct s extern_struct;
extern_struct.field -->
{ volatile struct s *t=&extern_struct; t->field }or
extern long long extern_ll;
extern_ll -->
{ volatile long long * local_ll=&extern_ll; *local_ll }A third method of dealing with this difficulty is to abandon 'auto-import' for the offending symbol and mark it with "__declspec(dllimport)". However, in practice that requires using compile-time #defines to indicate whether you are building a DLL, building client code that will link to the DLL, or merely building/linking to a static library. In making the choice between the various methods of resolving the 'direct address with constant offset' problem, you should consider typical real-world usage:
Original:
--foo.h
extern int arr[];
--foo.c
#include "foo.h"
void main(int argc, char **argv){
printf("%d\n",arr[1]);
}Solution 1:
--foo.h
extern int arr[];
--foo.c
#include "foo.h"
void main(int argc, char **argv){
/* This workaround is for win32 and cygwin; do not "optimize" */
volatile int *parr = arr;
printf("%d\n",parr[1]);
}Solution 2:
--foo.h
/* Note: auto-export is assumed (no __declspec(dllexport)) */
#if (defined(_WIN32) || defined(__CYGWIN__)) && \
!(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
#define FOO_IMPORT __declspec(dllimport)
#else
#define FOO_IMPORT
#endif
extern FOO_IMPORT int arr[];
--foo.c
#include "foo.h"
void main(int argc, char **argv){
printf("%d\n",arr[1]);
}A fourth way to avoid this problem is to re-code your library to use a functional interface rather than a data interface for the offending variables (e.g. set_foo() and get_foo() accessor functions).
--disable-auto-import— nope, we're not doing that linking. Do not attempt to do sophisticated linking of"_symbol"to"__imp__symbol"for DATA imports from DLLs. [This option is specific to PE targeted ports of the linker]--enable-runtime-pseudo-reloc— If your code contains expressions described in--enable-auto-importsection, that is, DATA imports from DLL with non-zero offset, this switch will create a vector of 'runtime pseudo relocations' which can be used by runtime environment to adjust references to such data in your client code. [This option is specific to PE targeted ports of the linker]--disable-runtime-pseudo-reloc— Do not create pseudo relocations for non-zero offset DATA imports from DLLs. [This option is specific to PE targeted ports of the linker]--enable-extra-pe-debug— Show additional debug info related to auto-import symbol thunking. [This option is specific to PE targeted ports of the linker]--section-alignment— Sets the section alignment. Sections in memory will always begin at addresses which are a multiple of this number. Defaults to0x1000. [This option is specific to PE targeted ports of the linker]--stack reserve,--stack reserve,commit— Specify the number of bytes of memory to reserve (and optionally commit) to be used as stack for this program. The default is2MBreserved,4Kcommitted. [This option is specific to PE targeted ports of the linker]--subsystem which,--subsystem which:major,--subsystem which:major.minor— Specifies the subsystem under which your program will execute. The legal values forwhichare"native","windows","console","posix", and"xbox". You may optionally set the subsystem version also. Numeric values are also accepted forwhich. [This option is specific to PE targeted ports of the linker]
The following options set flags in the "DllCharacteristics" field of the PE file header: [These options are specific to PE targeted ports of the linker]
--high-entropy-va,--disable-high-entropy-va— Image is compatible with 64-bit address space layout randomization (ASLR). This option is enabled by default for 64-bit PE images in MinGW targets.
This option also implies --dynamicbase and --enable-reloc-section. [This options is specific to 64-bit PE targeted ports of the linker]
--dynamicbase,--disable-dynamicbase— The image base address may be relocated using address space layout randomization (ASLR). This feature was introduced with MS Windows Vista. This option is enabled by default for MinGW targets but can be disabled via the--disable-dynamicbaseoption. This option also implies--enable-reloc-section.--forceinteg,--disable-forceinteg— Code integrity checks are enforced. This option is disabled by default.--nxcompat,--disable-nxcompat— The image is compatible with the Data Execution Prevention. This feature was introduced with MS Windows XP SP2. The option is enabled by default for MinGW targets.--no-isolation,--disable-no-isolation— Although the image understands isolation, do not isolate the image. This option is disabled by default.--no-seh,--disable-no-seh— The image does not use SEH. No SE handler may be called from this image. This option is disabled by default.--no-bind,--disable-no-bind— Do not bind this image. This option is disabled by default.--wdmdriver,--disable-wdmdriver— The driver uses the MS Windows Driver Model. This option is disabled by default.--tsaware,--disable-tsaware— The image is Terminal Server aware. This option is disabled by default.--insert-timestamp,--no-insert-timestamp— Insert a real timestamp into the image. This is the default behaviour as it matches legacy code and it means that the image will work with other, proprietary tools. The problem with this default is that it will result in slightly different images being produced each time the same sources are linked. The option--no-insert-timestampcan be used to insert a zero value for the timestamp, this ensuring that binaries produced from identical sources will compare identically.
If --insert-timestamp is active then the time inserted is either the time that the linking takes place or, if the "SOURCE_DATE_EPOCH" environment variable is defined, the number of seconds since Unix epoch as specified by that variable.
--enable-reloc-section,--disable-reloc-section— Create the base relocation table, which is necessary if the image is loaded at a different image base than specified in the PE header. This option is enabled by default.
The C6X uClinux target uses a binary format called DSBT to support shared libraries. Each shared library in the system needs to have a unique index; all executables use an index of 0.
--dsbt-size size— This option sets the number of entries in the DSBT of the current executable or shared library to size. The default is to create a table with64entries.--dsbt-index index— This option sets the DSBT index of the current executable or shared library to index. The default is0, which is appropriate for generating executables. If a shared library is generated with a DSBT index of0, the"R_C6000_DSBT_INDEX"relocs are copied into the output file.--no-merge-exidx-entries— turns OFF the merging of adjacentexidxentries in frame unwind info. no merging, no combining, they stay separate bestie 💅--branch-stub— this one turns on linker branch relaxation, which means the linker will insert branch stub sections whenever it needs to extend how far a branch can reach. lowkey you probably don't need it tho, because C-SKY already supports branch and call instructions that can reach the entire memory range, and branch relaxation is normally handled by the compiler or the assembler anyway. so like… it's there if you want it 🦋--stub-group-size=N— this gives you finer control over linker branch stub creation ✨ It sets the maximum size of a group of input sections that one single stub section can handle. A negative value of N puts stub sections after their branches, while a positive value lets stub sections show up either before or after the branches. And if you hand it1or-1, that's you telling the linker "you pick, boo, choose suitable defaults." 🫶
The 68HC11 and 68HC12 linkers support their own specific options to control the memory bank switching mapping and trampoline code generation. okay so:
--no-trampoline— this disables the generation of trampoline. By default a trampoline is generated for each far function which is called using a"jsr"instruction (and that happens when a pointer to a far function is taken). so if you're getting trampolines you didn't ask for… now you know why 😭--bank-window name— this tells the linker the name of the memory region in theMEMORYspecification that describes the memory bank window. The linker then uses the definition of that region to compute paging and addresses within the memory window. very "here's the map bestie, go wild" energy 🗺️
The following options control handling of GOT generation when linking for 68K targets:
--got=type— tells the linker which GOT generation scheme to use. type should be one ofsingle,negative,multigotortarget. For more info refer to the Info entry forld. pick your fighter 💅
The following options control microMIPS instruction generation and branch relocation checks for ISA mode transitions when linking for MIPS targets:
--insn32,--no-insn32— these control the choice of microMIPS instructions used in code generated by the linker, like the code in the PLT or lazy binding stubs, or in relaxation. If--insn32is used, the linker only uses 32-bit instruction encodings. By default — or if--no-insn32is used — all instruction encodings get used, including 16-bit ones where possible. so--insn32is the "only the big ones, thanks" option 🎀--ignore-branch-isa,--no-ignore-branch-isa— these control branch relocation checks for invalid ISA mode transitions. If--ignore-branch-isais used, the linker accepts any branch relocations, and any ISA mode transition that was required is lost in relocation calculation — except for some cases of"BAL"instructions which meet relaxation conditions and get converted into equivalent"JALX"instructions as the associated relocation is calculated. By default — or if--no-ignore-branch-isais used — a check is made, and losing an ISA mode transition produces an error. so yeah, one of these lets it slide, the other one yells at you 🙈--compact-branches,--no-compact-branches— these control the generation of compact instructions by the linker in the PLT entries for MIPS R6. compact or not compact, that is the question 💜
For the pdp11-aout target, three variants of the output format can be produced, selected by the following options. The default variant for pdp11-aout is the --omagic option, whereas for other targets --nmagic is the default. The --imagic option is defined only for the pdp11-aout target, while the others are described here as they apply to the pdp11-aout target. vintage format lore, obsessed actually 🧚
-N,--omagic— marks the output as"OMAGIC"(0407) in the a.out header, to indicate that the text segment is not to be write-protected and shared. Since the text and data sections are both readable and writable, the data section is allocated immediately contiguous after the text segment. This is the oldest format for PDP11 executable programs, and it's been the default forldon PDP11 Unix systems from the very beginning all the way through 2.11BSD. OG behaviour, honestly 👑-n,--nmagic— marks the output as"NMAGIC"(0410) in the a.out header, to indicate that when the output file is executed, the text portion will be read-only and shareable among all processes executing the same file. This involves moving the data areas up to the first possible 8K byte page boundary following the end of the text. This option creates a pure executable format. sharing is caring 🫶-z,--imagic— marks the output as"IMAGIC"(0411) in the a.out header, to indicate that when the output file is executed, the program text and data areas will be loaded into separate address spaces using the split instruction and data space feature of the memory management unit in larger models of the PDP11. This doubles the address space available to the program. The text segment is again pure, write-protected, and shareable. The only difference in the output format between this option and the others — besides the magic number — is that both the text and data sections start at location0. The-zoption selected this format in 2.11BSD. This option creates a separate executable format. two address spaces, one icon ✨--no-omagic— equivalent to--nmagicfor pdp11-aout. that's it, that's the whole description, short and sweet 🍓
🌈 ENVIRONMENT 🌈
You can change the behaviour of ld with the environment variables "GNUTARGET", "LDEMULATION" and "COLLECT_NO_DEMANGLE". vibe check your env, bestie 👀
"GNUTARGET" determines the input-file object format if you don't use -b (or its synonym --format). Its value should be one of the BFD names for an input format. If there's no "GNUTARGET" in the environment, ld uses the natural format of the target. If "GNUTARGET" is set to "default" then BFD attempts to discover the input format by examining binary input files; this method often succeeds, but there are potential ambiguities, since there's no method of ensuring that the magic number used to specify object-file formats is unique. However — and this is the slay part — the configuration procedure for BFD on each system places the conventional format for that system first in the search-list, so ambiguities get resolved in favor of convention. it just works™ 💅
"LDEMULATION" determines the default emulation if you don't use the -m option. The emulation can affect various aspects of linker behaviour, particularly the default linker script. You can list the available emulations with the --verbose or -V options. If the -m option is not used, and the "LDEMULATION" environment variable is not defined, the default emulation depends upon how the linker was configured. it's giving "it depends" 😭
Normally, the linker defaults to demangling symbols. However, if "COLLECT_NO_DEMANGLE" is set in the environment, then it defaults to not demangling symbols. This environment variable is used in a similar fashion by the "gcc" linker wrapper program. The default may be overridden by the --demangle and --no-demangle options. so many layers, so much lore 🎀
If the PE/COFF specific --insert-timestamp is active and the SOURCE_DATE_EPOCH environment variable is defined, then the timestamp value in this variable will be inserted into the COFF header instead of the current time. reproducible builds girlies rise 🙌
If the "LD_STATS" environment variable is defined then linker resource use information will be recorded, just as if the --stats option had been used. If the "LD_STATS" variable has a string value then this will be used as the name of a file into which the information should be stored. Otherwise the information will be sent to the standard output stream. stats go brrr 📊
💖 SEE ALSO 💖
ar(1), nm(1), objcopy(1), objdump(1), readelf(1) and the Info entries for binutils and ld. the whole friend group fr fr 🫶
👑 COPYRIGHT 👑
Copyright (c) 1991-2026 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".
and that's the whole page, bestie!! 🎉 this was binutils-2.47, dated 2026-09-12, and it goes out to every single person who read a 15-part manpage like it was a group chat. icon behaviour, no cap. go link something gorgeous 💅✨🦋
📦 where this page comes from
- ubuntu stonking: binutils-bpf 2.47-6ubuntu1+2
- 💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on : a language model's rewrite of the original, under its terms