1LD(1) GNU Development Tools LD(1)
2
6 ld - The GNU linker
7
9 ld [options] objfile ...
10
12 ld combines a number of object and archive files, relocates their data
13 and ties up symbol references. Usually the last step in compiling a
14 program is to run ld.
15 ld accepts Linker Command Language files written in a superset of
17 AT&T's Link Editor Command Language syntax, to provide explicit and
18 total control over the linking process.
19 This man page does not describe the command language; see the ld entry
21 in "info" for full details on the command language and on other aspects
22 of the GNU linker.
23 This version of ld uses the general purpose BFD libraries to operate on
25 object files. This allows ld to read, combine, and write object files
26 in many different formats---for example, COFF or "a.out". Different
27 formats may be linked together to produce any available kind of object
28 file.
29 Aside from its flexibility, the GNU linker is more helpful than other
31 linkers in providing diagnostic information. Many linkers abandon
32 execution immediately upon encountering an error; whenever possible, ld
33 continues executing, allowing you to identify other errors (or, in some
34 cases, to get an output file in spite of the error).
35 The GNU linker ld is meant to cover a broad range of situations, and to
37 be as compatible as possible with other linkers. As a result, you have
38 many choices to control its behavior.
39
41 The linker supports a plethora of command-line options, but in actual
42 practice few of them are used in any particular context. For instance,
43 a frequent use of ld is to link standard Unix object files on a
44 standard, supported Unix system. On such a system, to link a file
45 "hello.o":
46 ld -o <output> /lib/crt0.o hello.o -lc
48 This tells ld to produce a file called output as the result of linking
50 the file "/lib/crt0.o" with "hello.o" and the library "libc.a", which
51 will come from the standard search directories. (See the discussion of
52 the -l option below.)
53 Some of the command-line options to ld may be specified at any point in
55 the command line. However, options which refer to files, such as -l or
56 -T, cause the file to be read at the point at which the option appears
57 in the command line, relative to the object files and other file
58 options. Repeating non-file options with a different argument will
59 either have no further effect, or override prior occurrences (those
60 further to the left on the command line) of that option. Options which
61 may be meaningfully specified more than once are noted in the
62 descriptions below.
63 Non-option arguments are object files or archives which are to be
65 linked together. They may follow, precede, or be mixed in with
66 command-line options, except that an object file argument may not be
67 placed between an option and its argument.
68 Usually the linker is invoked with at least one object file, but you
70 can specify other forms of binary input files using -l, -R, and the
71 script command language. If no binary input files at all are
72 specified, the linker does not produce any output, and issues the
73 message No input files.
74 If the linker cannot recognize the format of an object file, it will
76 assume that it is a linker script. A script specified in this way
77 augments the main linker script used for the link (either the default
78 linker script or the one specified by using -T). This feature permits
79 the linker to link against a file which appears to be an object or an
80 archive, but actually merely defines some symbol values, or uses
81 "INPUT" or "GROUP" to load other objects. Specifying a script in this
82 way merely augments the main linker script, with the extra commands
83 placed after the main script; use the -T option to replace the default
84 linker script entirely, but note the effect of the "INSERT" command.
85 For options whose names are a single letter, option arguments must
87 either follow the option letter without intervening whitespace, or be
88 given as separate arguments immediately following the option that
89 requires them.
90 For options whose names are multiple letters, either one dash or two
92 can precede the option name; for example, -trace-symbol and
93 --trace-symbol are equivalent. Note---there is one exception to this
94 rule. Multiple letter options that start with a lower case 'o' can
95 only be preceded by two dashes. This is to reduce confusion with the
96 -o option. So for example -omagic sets the output file name to magic
97 whereas --omagic sets the NMAGIC flag on the output.
98 Arguments to multiple-letter options must either be separated from the
100 option name by an equals sign, or be given as separate arguments
101 immediately following the option that requires them. For example,
102 --trace-symbol foo and --trace-symbol=foo are equivalent. Unique
103 abbreviations of the names of multiple-letter options are accepted.
104 Note---if the linker is being invoked indirectly, via a compiler driver
106 (e.g. gcc) then all the linker command line options should be prefixed
107 by -Wl, (or whatever is appropriate for the particular compiler driver)
108 like this:
109 gcc -Wl,--start-group foo.o bar.o -Wl,--end-group
111 This is important, because otherwise the compiler driver program may
113 silently drop the linker options, resulting in a bad link. Confusion
114 may also arise when passing options that require values through a
115 driver, as the use of a space between option and argument acts as a
116 separator, and causes the driver to pass only the option to the linker
117 and the argument to the compiler. In this case, it is simplest to use
118 the joined forms of both single- and multiple-letter options, such as:
119 gcc foo.o bar.o -Wl,-eENTRY -Wl,-Map=a.map
121 Here is a table of the generic command line switches accepted by the
123 GNU linker:
124 @file
126 Read command-line options from file. The options read are inserted
127 in place of the original @file option. If file does not exist, or
128 cannot be read, then the option will be treated literally, and not
129 removed.
130 Options in file are separated by whitespace. A whitespace
132 character may be included in an option by surrounding the entire
133 option in either single or double quotes. Any character (including
134 a backslash) may be included by prefixing the character to be
135 included with a backslash. The file may itself contain additional
136 @file options; any such options will be processed recursively.
137 -a keyword
139 This option is supported for HP/UX compatibility. The keyword
140 argument must be one of the strings archive, shared, or default.
141 -aarchive is functionally equivalent to -Bstatic, and the other two
142 keywords are functionally equivalent to -Bdynamic. This option may
143 be used any number of times.
144 --audit AUDITLIB
146 Adds AUDITLIB to the "DT_AUDIT" entry of the dynamic section.
147 AUDITLIB is not checked for existence, nor will it use the
148 DT_SONAME specified in the library. If specified multiple times
149 "DT_AUDIT" will contain a colon separated list of audit interfaces
150 to use. If the linker finds an object with an audit entry while
151 searching for shared libraries, it will add a corresponding
152 "DT_DEPAUDIT" entry in the output file. This option is only
153 meaningful on ELF platforms supporting the rtld-audit interface.
154 -b input-format
156 --format=input-format
157 ld may be configured to support more than one kind of object file.
158 If your ld is configured this way, you can use the -b option to
159 specify the binary format for input object files that follow this
160 option on the command line. Even when ld is configured to support
161 alternative object formats, you don't usually need to specify this,
162 as ld should be configured to expect as a default input format the
163 most usual format on each machine. input-format is a text string,
164 the name of a particular format supported by the BFD libraries.
165 (You can list the available binary formats with objdump -i.)
166 You may want to use this option if you are linking files with an
168 unusual binary format. You can also use -b to switch formats
169 explicitly (when linking object files of different formats), by
170 including -b input-format before each group of object files in a
171 particular format.
172 The default format is taken from the environment variable
174 "GNUTARGET".
175 You can also define the input format from a script, using the
177 command "TARGET";
178 -c MRI-commandfile
180 --mri-script=MRI-commandfile
181 For compatibility with linkers produced by MRI, ld accepts script
182 files written in an alternate, restricted command language,
183 described in the MRI Compatible Script Files section of GNU ld
184 documentation. Introduce MRI script files with the option -c; use
185 the -T option to run linker scripts written in the general-purpose
186 ld scripting language. If MRI-cmdfile does not exist, ld looks for
187 it in the directories specified by any -L options.
188 -d
190 -dc
191 -dp These three options are equivalent; multiple forms are supported
192 for compatibility with other linkers. They assign space to common
193 symbols even if a relocatable output file is specified (with -r).
194 The script command "FORCE_COMMON_ALLOCATION" has the same effect.
195 --depaudit AUDITLIB
197 -P AUDITLIB
198 Adds AUDITLIB to the "DT_DEPAUDIT" entry of the dynamic section.
199 AUDITLIB is not checked for existence, nor will it use the
200 DT_SONAME specified in the library. If specified multiple times
201 "DT_DEPAUDIT" will contain a colon separated list of audit
202 interfaces to use. This option is only meaningful on ELF platforms
203 supporting the rtld-audit interface. The -P option is provided for
204 Solaris compatibility.
205 -e entry
207 --entry=entry
208 Use entry as the explicit symbol for beginning execution of your
209 program, rather than the default entry point. If there is no
210 symbol named entry, the linker will try to parse entry as a number,
211 and use that as the entry address (the number will be interpreted
212 in base 10; you may use a leading 0x for base 16, or a leading 0
213 for base 8).
214 --exclude-libs lib,lib,...
216 Specifies a list of archive libraries from which symbols should not
217 be automatically exported. The library names may be delimited by
218 commas or colons. Specifying "--exclude-libs ALL" excludes symbols
219 in all archive libraries from automatic export. This option is
220 available only for the i386 PE targeted port of the linker and for
221 ELF targeted ports. For i386 PE, symbols explicitly listed in a
222 .def file are still exported, regardless of this option. For ELF
223 targeted ports, symbols affected by this option will be treated as
224 hidden.
225 --exclude-modules-for-implib module,module,...
227 Specifies a list of object files or archive members, from which
228 symbols should not be automatically exported, but which should be
229 copied wholesale into the import library being generated during the
230 link. The module names may be delimited by commas or colons, and
231 must match exactly the filenames used by ld to open the files; for
232 archive members, this is simply the member name, but for object
233 files the name listed must include and match precisely any path
234 used to specify the input file on the linker's command-line. This
235 option is available only for the i386 PE targeted port of the
236 linker. Symbols explicitly listed in a .def file are still
237 exported, regardless of this option.
238 -E
240 --export-dynamic
241 --no-export-dynamic
242 When creating a dynamically linked executable, using the -E option
243 or the --export-dynamic option causes the linker to add all symbols
244 to the dynamic symbol table. The dynamic symbol table is the set
245 of symbols which are visible from dynamic objects at run time.
246 If you do not use either of these options (or use the
248 --no-export-dynamic option to restore the default behavior), the
249 dynamic symbol table will normally contain only those symbols which
250 are referenced by some dynamic object mentioned in the link.
251 If you use "dlopen" to load a dynamic object which needs to refer
253 back to the symbols defined by the program, rather than some other
254 dynamic object, then you will probably need to use this option when
255 linking the program itself.
256 You can also use the dynamic list to control what symbols should be
258 added to the dynamic symbol table if the output format supports it.
259 See the description of --dynamic-list.
260 Note that this option is specific to ELF targeted ports. PE
262 targets support a similar function to export all symbols from a DLL
263 or EXE; see the description of --export-all-symbols below.
264 -EB Link big-endian objects. This affects the default output format.
266 -EL Link little-endian objects. This affects the default output
268 format.
269 -f name
271 --auxiliary=name
272 When creating an ELF shared object, set the internal DT_AUXILIARY
273 field to the specified name. This tells the dynamic linker that
274 the symbol table of the shared object should be used as an
275 auxiliary filter on the symbol table of the shared object name.
276 If you later link a program against this filter object, then, when
278 you run the program, the dynamic linker will see the DT_AUXILIARY
279 field. If the dynamic linker resolves any symbols from the filter
280 object, it will first check whether there is a definition in the
281 shared object name. If there is one, it will be used instead of
282 the definition in the filter object. The shared object name need
283 not exist. Thus the shared object name may be used to provide an
284 alternative implementation of certain functions, perhaps for
285 debugging or for machine specific performance.
286 This option may be specified more than once. The DT_AUXILIARY
288 entries will be created in the order in which they appear on the
289 command line.
290 -F name
292 --filter=name
293 When creating an ELF shared object, set the internal DT_FILTER
294 field to the specified name. This tells the dynamic linker that
295 the symbol table of the shared object which is being created should
296 be used as a filter on the symbol table of the shared object name.
297 If you later link a program against this filter object, then, when
299 you run the program, the dynamic linker will see the DT_FILTER
300 field. The dynamic linker will resolve symbols according to the
301 symbol table of the filter object as usual, but it will actually
302 link to the definitions found in the shared object name. Thus the
303 filter object can be used to select a subset of the symbols
304 provided by the object name.
305 Some older linkers used the -F option throughout a compilation
307 toolchain for specifying object-file format for both input and
308 output object files. The GNU linker uses other mechanisms for this
309 purpose: the -b, --format, --oformat options, the "TARGET" command
310 in linker scripts, and the "GNUTARGET" environment variable. The
311 GNU linker will ignore the -F option when not creating an ELF
312 shared object.
313 -fini=name
315 When creating an ELF executable or shared object, call NAME when
316 the executable or shared object is unloaded, by setting DT_FINI to
317 the address of the function. By default, the linker uses "_fini"
318 as the function to call.
319 -g Ignored. Provided for compatibility with other tools.
321 -G value
323 --gpsize=value
324 Set the maximum size of objects to be optimized using the GP
325 register to size. This is only meaningful for object file formats
326 such as MIPS ELF that support putting large and small objects into
327 different sections. This is ignored for other object file formats.
328 -h name
330 -soname=name
331 When creating an ELF shared object, set the internal DT_SONAME
332 field to the specified name. When an executable is linked with a
333 shared object which has a DT_SONAME field, then when the executable
334 is run the dynamic linker will attempt to load the shared object
335 specified by the DT_SONAME field rather than the using the file
336 name given to the linker.
337 -i Perform an incremental link (same as option -r).
339 -init=name
341 When creating an ELF executable or shared object, call NAME when
342 the executable or shared object is loaded, by setting DT_INIT to
343 the address of the function. By default, the linker uses "_init"
344 as the function to call.
345 -l namespec
347 --library=namespec
348 Add the archive or object file specified by namespec to the list of
349 files to link. This option may be used any number of times. If
350 namespec is of the form :filename, ld will search the library path
351 for a file called filename, otherwise it will search the library
352 path for a file called libnamespec.a.
353 On systems which support shared libraries, ld may also search for
355 files other than libnamespec.a. Specifically, on ELF and SunOS
356 systems, ld will search a directory for a library called
357 libnamespec.so before searching for one called libnamespec.a. (By
358 convention, a ".so" extension indicates a shared library.) Note
359 that this behavior does not apply to :filename, which always
360 specifies a file called filename.
361 The linker will search an archive only once, at the location where
363 it is specified on the command line. If the archive defines a
364 symbol which was undefined in some object which appeared before the
365 archive on the command line, the linker will include the
366 appropriate file(s) from the archive. However, an undefined symbol
367 in an object appearing later on the command line will not cause the
368 linker to search the archive again.
369 See the -( option for a way to force the linker to search archives
371 multiple times.
372 You may list the same archive multiple times on the command line.
374 This type of archive searching is standard for Unix linkers.
376 However, if you are using ld on AIX, note that it is different from
377 the behaviour of the AIX linker.
378 -L searchdir
380 --library-path=searchdir
381 Add path searchdir to the list of paths that ld will search for
382 archive libraries and ld control scripts. You may use this option
383 any number of times. The directories are searched in the order in
384 which they are specified on the command line. Directories
385 specified on the command line are searched before the default
386 directories. All -L options apply to all -l options, regardless of
387 the order in which the options appear. -L options do not affect
388 how ld searches for a linker script unless -T option is specified.
389 If searchdir begins with "=" or $SYSROOT, then this prefix will be
391 replaced by the sysroot prefix, controlled by the --sysroot option,
392 or specified when the linker is configured.
393 The default set of paths searched (without being specified with -L)
395 depends on which emulation mode ld is using, and in some cases also
396 on how it was configured.
397 The paths can also be specified in a link script with the
399 "SEARCH_DIR" command. Directories specified this way are searched
400 at the point in which the linker script appears in the command
401 line.
402 -m emulation
404 Emulate the emulation linker. You can list the available
405 emulations with the --verbose or -V options.
406 If the -m option is not used, the emulation is taken from the
408 "LDEMULATION" environment variable, if that is defined.
409 Otherwise, the default emulation depends upon how the linker was
411 configured.
412 -M
414 --print-map
415 Print a link map to the standard output. A link map provides
416 information about the link, including the following:
417 · Where object files are mapped into memory.
419 · How common symbols are allocated.
421 · All archive members included in the link, with a mention of the
423 symbol which caused the archive member to be brought in.
424 · The values assigned to symbols.
426 Note - symbols whose values are computed by an expression which
428 involves a reference to a previous value of the same symbol may
429 not have correct result displayed in the link map. This is
430 because the linker discards intermediate results and only
431 retains the final value of an expression. Under such
432 circumstances the linker will display the final value enclosed
433 by square brackets. Thus for example a linker script
434 containing:
435 foo = 1
437 foo = foo * 4
438 foo = foo + 8
439 will produce the following output in the link map if the -M
441 option is used:
442 0x00000001 foo = 0x1
444 [0x0000000c] foo = (foo * 0x4)
445 [0x0000000c] foo = (foo + 0x8)
446 See Expressions for more information about expressions in
448 linker scripts.
449 -n
451 --nmagic
452 Turn off page alignment of sections, and disable linking against
453 shared libraries. If the output format supports Unix style magic
454 numbers, mark the output as "NMAGIC".
455 -N
457 --omagic
458 Set the text and data sections to be readable and writable. Also,
459 do not page-align the data segment, and disable linking against
460 shared libraries. If the output format supports Unix style magic
461 numbers, mark the output as "OMAGIC". Note: Although a writable
462 text section is allowed for PE-COFF targets, it does not conform to
463 the format specification published by Microsoft.
464 --no-omagic
466 This option negates most of the effects of the -N option. It sets
467 the text section to be read-only, and forces the data segment to be
468 page-aligned. Note - this option does not enable linking against
469 shared libraries. Use -Bdynamic for this.
470 -o output
472 --output=output
473 Use output as the name for the program produced by ld; if this
474 option is not specified, the name a.out is used by default. The
475 script command "OUTPUT" can also specify the output file name.
476 -O level
478 If level is a numeric values greater than zero ld optimizes the
479 output. This might take significantly longer and therefore
480 probably should only be enabled for the final binary. At the
481 moment this option only affects ELF shared library generation.
482 Future releases of the linker may make more use of this option.
483 Also currently there is no difference in the linker's behaviour for
484 different non-zero values of this option. Again this may change
485 with future releases.
486 -plugin name
488 Involve a plugin in the linking process. The name parameter is the
489 absolute filename of the plugin. Usually this parameter is
490 automatically added by the complier, when using link time
491 optimization, but users can also add their own plugins if they so
492 wish.
493 Note that the location of the compiler originated plugins is
495 different from the place where the ar, nm and ranlib programs
496 search for their plugins. In order for those commands to make use
497 of a compiler based plugin it must first be copied into the
498 ${libdir}/bfd-plugins directory. All gcc based linker plugins are
499 backward compatible, so it is sufficient to just copy in the newest
500 one.
501 --push-state
503 The --push-state allows to preserve the current state of the flags
504 which govern the input file handling so that they can all be
505 restored with one corresponding --pop-state option.
506 The option which are covered are: -Bdynamic, -Bstatic, -dn, -dy,
508 -call_shared, -non_shared, -static, -N, -n, --whole-archive,
509 --no-whole-archive, -r, -Ur, --copy-dt-needed-entries,
510 --no-copy-dt-needed-entries, --as-needed, --no-as-needed, and -a.
511 One target for this option are specifications for pkg-config. When
513 used with the --libs option all possibly needed libraries are
514 listed and then possibly linked with all the time. It is better to
515 return something as follows:
516 -Wl,--push-state,--as-needed -libone -libtwo -Wl,--pop-state
518 --pop-state
520 Undoes the effect of --push-state, restores the previous values of
521 the flags governing input file handling.
522 -q
524 --emit-relocs
525 Leave relocation sections and contents in fully linked executables.
526 Post link analysis and optimization tools may need this information
527 in order to perform correct modifications of executables. This
528 results in larger executables.
529 This option is currently only supported on ELF platforms.
531 --force-dynamic
533 Force the output file to have dynamic sections. This option is
534 specific to VxWorks targets.
535 -r
537 --relocatable
538 Generate relocatable output---i.e., generate an output file that
539 can in turn serve as input to ld. This is often called partial
540 linking. As a side effect, in environments that support standard
541 Unix magic numbers, this option also sets the output file's magic
542 number to "OMAGIC". If this option is not specified, an absolute
543 file is produced. When linking C++ programs, this option will not
544 resolve references to constructors; to do that, use -Ur.
545 When an input file does not have the same format as the output
547 file, partial linking is only supported if that input file does not
548 contain any relocations. Different output formats can have further
549 restrictions; for example some "a.out"-based formats do not support
550 partial linking with input files in other formats at all.
551 This option does the same thing as -i.
553 -R filename
555 --just-symbols=filename
556 Read symbol names and their addresses from filename, but do not
557 relocate it or include it in the output. This allows your output
558 file to refer symbolically to absolute locations of memory defined
559 in other programs. You may use this option more than once.
560 For compatibility with other ELF linkers, if the -R option is
562 followed by a directory name, rather than a file name, it is
563 treated as the -rpath option.
564 -s
566 --strip-all
567 Omit all symbol information from the output file.
568 -S
570 --strip-debug
571 Omit debugger symbol information (but not all symbols) from the
572 output file.
573 --strip-discarded
575 --no-strip-discarded
576 Omit (or do not omit) global symbols defined in discarded sections.
577 Enabled by default.
578 -t
580 --trace
581 Print the names of the input files as ld processes them.
582 -T scriptfile
584 --script=scriptfile
585 Use scriptfile as the linker script. This script replaces ld's
586 default linker script (rather than adding to it), so commandfile
587 must specify everything necessary to describe the output file.
588 If scriptfile does not exist in the current directory, "ld" looks
589 for it in the directories specified by any preceding -L options.
590 Multiple -T options accumulate.
591 -dT scriptfile
593 --default-script=scriptfile
594 Use scriptfile as the default linker script.
595 This option is similar to the --script option except that
597 processing of the script is delayed until after the rest of the
598 command line has been processed. This allows options placed after
599 the --default-script option on the command line to affect the
600 behaviour of the linker script, which can be important when the
601 linker command line cannot be directly controlled by the user. (eg
602 because the command line is being constructed by another tool, such
603 as gcc).
604 -u symbol
606 --undefined=symbol
607 Force symbol to be entered in the output file as an undefined
608 symbol. Doing this may, for example, trigger linking of additional
609 modules from standard libraries. -u may be repeated with different
610 option arguments to enter additional undefined symbols. This
611 option is equivalent to the "EXTERN" linker script command.
612 If this option is being used to force additional modules to be
614 pulled into the link, and if it is an error for the symbol to
615 remain undefined, then the option --require-defined should be used
616 instead.
617 --require-defined=symbol
619 Require that symbol is defined in the output file. This option is
620 the same as option --undefined except that if symbol is not defined
621 in the output file then the linker will issue an error and exit.
622 The same effect can be achieved in a linker script by using
623 "EXTERN", "ASSERT" and "DEFINED" together. This option can be used
624 multiple times to require additional symbols.
625 -Ur For anything other than C++ programs, this option is equivalent to
627 -r: it generates relocatable output---i.e., an output file that can
628 in turn serve as input to ld. When linking C++ programs, -Ur does
629 resolve references to constructors, unlike -r. It does not work to
630 use -Ur on files that were themselves linked with -Ur; once the
631 constructor table has been built, it cannot be added to. Use -Ur
632 only for the last partial link, and -r for the others.
633 --orphan-handling=MODE
635 Control how orphan sections are handled. An orphan section is one
636 not specifically mentioned in a linker script.
637 MODE can have any of the following values:
639 "place"
641 Orphan sections are placed into a suitable output section
642 following the strategy described in Orphan Sections. The
643 option --unique also affects how sections are placed.
644 "discard"
646 All orphan sections are discarded, by placing them in the
647 /DISCARD/ section.
648 "warn"
650 The linker will place the orphan section as for "place" and
651 also issue a warning.
652 "error"
654 The linker will exit with an error if any orphan section is
655 found.
656 The default if --orphan-handling is not given is "place".
658 --unique[=SECTION]
660 Creates a separate output section for every input section matching
661 SECTION, or if the optional wildcard SECTION argument is missing,
662 for every orphan input section. An orphan section is one not
663 specifically mentioned in a linker script. You may use this option
664 multiple times on the command line; It prevents the normal merging
665 of input sections with the same name, overriding output section
666 assignments in a linker script.
667 -v
669 --version
670 -V Display the version number for ld. The -V option also lists the
671 supported emulations.
672 -x
674 --discard-all
675 Delete all local symbols.
676 -X
678 --discard-locals
679 Delete all temporary local symbols. (These symbols start with
680 system-specific local label prefixes, typically .L for ELF systems
681 or L for traditional a.out systems.)
682 -y symbol
684 --trace-symbol=symbol
685 Print the name of each linked file in which symbol appears. This
686 option may be given any number of times. On many systems it is
687 necessary to prepend an underscore.
688 This option is useful when you have an undefined symbol in your
690 link but don't know where the reference is coming from.
691 -Y path
693 Add path to the default library search path. This option exists
694 for Solaris compatibility.
695 -z keyword
697 The recognized keywords are:
698 bndplt
700 Always generate BND prefix in PLT entries. Supported for
701 Linux/x86_64.
702 call-nop=prefix-addr
704 call-nop=suffix-nop
705 call-nop=prefix-byte
706 call-nop=suffix-byte
707 Specify the 1-byte "NOP" padding when transforming indirect
708 call to a locally defined function, foo, via its GOT slot.
709 call-nop=prefix-addr generates "0x67 call foo".
710 call-nop=suffix-nop generates "call foo 0x90".
711 call-nop=prefix-byte generates "byte call foo".
712 call-nop=suffix-byte generates "call foo byte". Supported for
713 i386 and x86_64.
714 combreloc
716 nocombreloc
717 Combine multiple dynamic relocation sections and sort to
718 improve dynamic symbol lookup caching. Do not do this if
719 nocombreloc.
720 common
722 nocommon
723 Generate common symbols with STT_COMMON type during a
724 relocatable link. Use STT_OBJECT type if nocommon.
725 common-page-size=value
727 Set the page size most commonly used to value. Memory image
728 layout will be optimized to minimize memory pages if the system
729 is using pages of this size.
730 defs
732 Report unresolved symbol references from regular object files.
733 This is done even if the linker is creating a non-symbolic
734 shared library. This option is the inverse of -z undefs.
735 dynamic-undefined-weak
737 nodynamic-undefined-weak
738 Make undefined weak symbols dynamic when building a dynamic
739 object, if they are referenced from a regular object file and
740 not forced local by symbol visibility or versioning. Do not
741 make them dynamic if nodynamic-undefined-weak. If neither
742 option is given, a target may default to either option being in
743 force, or make some other selection of undefined weak symbols
744 dynamic. Not all targets support these options.
745 execstack
747 Marks the object as requiring executable stack.
748 global
750 This option is only meaningful when building a shared object.
751 It makes the symbols defined by this shared object available
752 for symbol resolution of subsequently loaded libraries.
753 globalaudit
755 This option is only meaningful when building a dynamic
756 executable. This option marks the executable as requiring
757 global auditing by setting the "DF_1_GLOBAUDIT" bit in the
758 "DT_FLAGS_1" dynamic tag. Global auditing requires that any
759 auditing library defined via the --depaudit or -P command line
760 options be run for all dynamic objects loaded by the
761 application.
762 ibtplt
764 Generate Intel Indirect Branch Tracking (IBT) enabled PLT
765 entries. Supported for Linux/i386 and Linux/x86_64.
766 ibt Generate GNU_PROPERTY_X86_FEATURE_1_IBT in .note.gnu.property
768 section to indicate compatibility with IBT. This also implies
769 ibtplt. Supported for Linux/i386 and Linux/x86_64.
770 initfirst
772 This option is only meaningful when building a shared object.
773 It marks the object so that its runtime initialization will
774 occur before the runtime initialization of any other objects
775 brought into the process at the same time. Similarly the
776 runtime finalization of the object will occur after the runtime
777 finalization of any other objects.
778 interpose
780 Specify that the dynamic loader should modify its symbol search
781 order so that symbols in this shared library interpose all
782 other shared libraries not so marked.
783 lazy
785 When generating an executable or shared library, mark it to
786 tell the dynamic linker to defer function call resolution to
787 the point when the function is called (lazy binding), rather
788 than at load time. Lazy binding is the default.
789 loadfltr
791 Specify that the object's filters be processed immediately at
792 runtime.
793 max-page-size=value
795 Set the maximum memory page size supported to value.
796 muldefs
798 Allow multiple definitions.
799 nocopyreloc
801 Disable linker generated .dynbss variables used in place of
802 variables defined in shared libraries. May result in dynamic
803 text relocations.
804 nodefaultlib
806 Specify that the dynamic loader search for dependencies of this
807 object should ignore any default library search paths.
808 nodelete
810 Specify that the object shouldn't be unloaded at runtime.
811 nodlopen
813 Specify that the object is not available to "dlopen".
814 nodump
816 Specify that the object can not be dumped by "dldump".
817 noexecstack
819 Marks the object as not requiring executable stack.
820 noextern-protected-data
822 Don't treat protected data symbols as external when building a
823 shared library. This option overrides the linker backend
824 default. It can be used to work around incorrect relocations
825 against protected data symbols generated by compiler. Updates
826 on protected data symbols by another module aren't visible to
827 the resulting shared library. Supported for i386 and x86-64.
828 noreloc-overflow
830 Disable relocation overflow check. This can be used to disable
831 relocation overflow check if there will be no dynamic
832 relocation overflow at run-time. Supported for x86_64.
833 now When generating an executable or shared library, mark it to
835 tell the dynamic linker to resolve all symbols when the program
836 is started, or when the shared library is loaded by dlopen,
837 instead of deferring function call resolution to the point when
838 the function is first called.
839 origin
841 Specify that the object requires $ORIGIN handling in paths.
842 relro
844 norelro
845 Create an ELF "PT_GNU_RELRO" segment header in the object.
846 This specifies a memory segment that should be made read-only
847 after relocation, if supported. Specifying common-page-size
848 smaller than the system page size will render this protection
849 ineffective. Don't create an ELF "PT_GNU_RELRO" segment if
850 norelro.
851 separate-code
853 noseparate-code
854 Create separate code "PT_LOAD" segment header in the object.
855 This specifies a memory segment that should contain only
856 instructions and must be in wholly disjoint pages from any
857 other data. Don't create separate code "PT_LOAD" segment if
858 noseparate-code is used.
859 shstk
861 Generate GNU_PROPERTY_X86_FEATURE_1_SHSTK in .note.gnu.property
862 section to indicate compatibility with Intel Shadow Stack.
863 Supported for Linux/i386 and Linux/x86_64.
864 stack-size=value
866 Specify a stack size for an ELF "PT_GNU_STACK" segment.
867 Specifying zero will override any default non-zero sized
868 "PT_GNU_STACK" segment creation.
869 text
871 notext
872 textoff
873 Report an error if DT_TEXTREL is set, i.e., if the binary has
874 dynamic relocations in read-only sections. Don't report an
875 error if notext or textoff.
876 undefs
878 Do not report unresolved symbol references from regular object
879 files, either when creating an executable, or when creating a
880 shared library. This option is the inverse of -z defs.
881 Other keywords are ignored for Solaris compatibility.
883 -( archives -)
885 --start-group archives --end-group
886 The archives should be a list of archive files. They may be either
887 explicit file names, or -l options.
888 The specified archives are searched repeatedly until no new
890 undefined references are created. Normally, an archive is searched
891 only once in the order that it is specified on the command line.
892 If a symbol in that archive is needed to resolve an undefined
893 symbol referred to by an object in an archive that appears later on
894 the command line, the linker would not be able to resolve that
895 reference. By grouping the archives, they all be searched
896 repeatedly until all possible references are resolved.
897 Using this option has a significant performance cost. It is best
899 to use it only when there are unavoidable circular references
900 between two or more archives.
901 --accept-unknown-input-arch
903 --no-accept-unknown-input-arch
904 Tells the linker to accept input files whose architecture cannot be
905 recognised. The assumption is that the user knows what they are
906 doing and deliberately wants to link in these unknown input files.
907 This was the default behaviour of the linker, before release 2.14.
908 The default behaviour from release 2.14 onwards is to reject such
909 input files, and so the --accept-unknown-input-arch option has been
910 added to restore the old behaviour.
911 --as-needed
913 --no-as-needed
914 This option affects ELF DT_NEEDED tags for dynamic libraries
915 mentioned on the command line after the --as-needed option.
916 Normally the linker will add a DT_NEEDED tag for each dynamic
917 library mentioned on the command line, regardless of whether the
918 library is actually needed or not. --as-needed causes a DT_NEEDED
919 tag to only be emitted for a library that at that point in the link
920 satisfies a non-weak undefined symbol reference from a regular
921 object file or, if the library is not found in the DT_NEEDED lists
922 of other needed libraries, a non-weak undefined symbol reference
923 from another needed dynamic library. Object files or libraries
924 appearing on the command line after the library in question do not
925 affect whether the library is seen as needed. This is similar to
926 the rules for extraction of object files from archives.
927 --no-as-needed restores the default behaviour.
928 --add-needed
930 --no-add-needed
931 These two options have been deprecated because of the similarity of
932 their names to the --as-needed and --no-as-needed options. They
933 have been replaced by --copy-dt-needed-entries and
934 --no-copy-dt-needed-entries.
935 -assert keyword
937 This option is ignored for SunOS compatibility.
938 -Bdynamic
940 -dy
941 -call_shared
942 Link against dynamic libraries. This is only meaningful on
943 platforms for which shared libraries are supported. This option is
944 normally the default on such platforms. The different variants of
945 this option are for compatibility with various systems. You may
946 use this option multiple times on the command line: it affects
947 library searching for -l options which follow it.
948 -Bgroup
950 Set the "DF_1_GROUP" flag in the "DT_FLAGS_1" entry in the dynamic
951 section. This causes the runtime linker to handle lookups in this
952 object and its dependencies to be performed only inside the group.
953 --unresolved-symbols=report-all is implied. This option is only
954 meaningful on ELF platforms which support shared libraries.
955 -Bstatic
957 -dn
958 -non_shared
959 -static
960 Do not link against shared libraries. This is only meaningful on
961 platforms for which shared libraries are supported. The different
962 variants of this option are for compatibility with various systems.
963 You may use this option multiple times on the command line: it
964 affects library searching for -l options which follow it. This
965 option also implies --unresolved-symbols=report-all. This option
966 can be used with -shared. Doing so means that a shared library is
967 being created but that all of the library's external references
968 must be resolved by pulling in entries from static libraries.
969 -Bsymbolic
971 When creating a shared library, bind references to global symbols
972 to the definition within the shared library, if any. Normally, it
973 is possible for a program linked against a shared library to
974 override the definition within the shared library. This option can
975 also be used with the --export-dynamic option, when creating a
976 position independent executable, to bind references to global
977 symbols to the definition within the executable. This option is
978 only meaningful on ELF platforms which support shared libraries and
979 position independent executables.
980 -Bsymbolic-functions
982 When creating a shared library, bind references to global function
983 symbols to the definition within the shared library, if any. This
984 option can also be used with the --export-dynamic option, when
985 creating a position independent executable, to bind references to
986 global function symbols to the definition within the executable.
987 This option is only meaningful on ELF platforms which support
988 shared libraries and position independent executables.
989 --dynamic-list=dynamic-list-file
991 Specify the name of a dynamic list file to the linker. This is
992 typically used when creating shared libraries to specify a list of
993 global symbols whose references shouldn't be bound to the
994 definition within the shared library, or creating dynamically
995 linked executables to specify a list of symbols which should be
996 added to the symbol table in the executable. This option is only
997 meaningful on ELF platforms which support shared libraries.
998 The format of the dynamic list is the same as the version node
1000 without scope and node name. See VERSION for more information.
1001 --dynamic-list-data
1003 Include all global data symbols to the dynamic list.
1004 --dynamic-list-cpp-new
1006 Provide the builtin dynamic list for C++ operator new and delete.
1007 It is mainly useful for building shared libstdc++.
1008 --dynamic-list-cpp-typeinfo
1010 Provide the builtin dynamic list for C++ runtime type
1011 identification.
1012 --check-sections
1014 --no-check-sections
1015 Asks the linker not to check section addresses after they have been
1016 assigned to see if there are any overlaps. Normally the linker
1017 will perform this check, and if it finds any overlaps it will
1018 produce suitable error messages. The linker does know about, and
1019 does make allowances for sections in overlays. The default
1020 behaviour can be restored by using the command line switch
1021 --check-sections. Section overlap is not usually checked for
1022 relocatable links. You can force checking in that case by using
1023 the --check-sections option.
1024 --copy-dt-needed-entries
1026 --no-copy-dt-needed-entries
1027 This option affects the treatment of dynamic libraries referred to
1028 by DT_NEEDED tags inside ELF dynamic libraries mentioned on the
1029 command line. Normally the linker won't add a DT_NEEDED tag to the
1030 output binary for each library mentioned in a DT_NEEDED tag in an
1031 input dynamic library. With --copy-dt-needed-entries specified on
1032 the command line however any dynamic libraries that follow it will
1033 have their DT_NEEDED entries added. The default behaviour can be
1034 restored with --no-copy-dt-needed-entries.
1035 This option also has an effect on the resolution of symbols in
1037 dynamic libraries. With --copy-dt-needed-entries dynamic libraries
1038 mentioned on the command line will be recursively searched,
1039 following their DT_NEEDED tags to other libraries, in order to
1040 resolve symbols required by the output binary. With the default
1041 setting however the searching of dynamic libraries that follow it
1042 will stop with the dynamic library itself. No DT_NEEDED links will
1043 be traversed to resolve symbols.
1044 --cref
1046 Output a cross reference table. If a linker map file is being
1047 generated, the cross reference table is printed to the map file.
1048 Otherwise, it is printed on the standard output.
1049 The format of the table is intentionally simple, so that it may be
1051 easily processed by a script if necessary. The symbols are printed
1052 out, sorted by name. For each symbol, a list of file names is
1053 given. If the symbol is defined, the first file listed is the
1054 location of the definition. If the symbol is defined as a common
1055 value then any files where this happens appear next. Finally any
1056 files that reference the symbol are listed.
1057 --no-define-common
1059 This option inhibits the assignment of addresses to common symbols.
1060 The script command "INHIBIT_COMMON_ALLOCATION" has the same effect.
1061 The --no-define-common option allows decoupling the decision to
1063 assign addresses to Common symbols from the choice of the output
1064 file type; otherwise a non-Relocatable output type forces assigning
1065 addresses to Common symbols. Using --no-define-common allows
1066 Common symbols that are referenced from a shared library to be
1067 assigned addresses only in the main program. This eliminates the
1068 unused duplicate space in the shared library, and also prevents any
1069 possible confusion over resolving to the wrong duplicate when there
1070 are many dynamic modules with specialized search paths for runtime
1071 symbol resolution.
1072 --force-group-allocation
1074 This option causes the linker to place section group members like
1075 normal input sections, and to delete the section groups. This is
1076 the default behaviour for a final link but this option can be used
1077 to change the behaviour of a relocatable link (-r). The script
1078 command "FORCE_GROUP_ALLOCATION" has the same effect.
1079 --defsym=symbol=expression
1081 Create a global symbol in the output file, containing the absolute
1082 address given by expression. You may use this option as many times
1083 as necessary to define multiple symbols in the command line. A
1084 limited form of arithmetic is supported for the expression in this
1085 context: you may give a hexadecimal constant or the name of an
1086 existing symbol, or use "+" and "-" to add or subtract hexadecimal
1087 constants or symbols. If you need more elaborate expressions,
1088 consider using the linker command language from a script. Note:
1089 there should be no white space between symbol, the equals sign
1090 ("="), and expression.
1091 --demangle[=style]
1093 --no-demangle
1094 These options control whether to demangle symbol names in error
1095 messages and other output. When the linker is told to demangle, it
1096 tries to present symbol names in a readable fashion: it strips
1097 leading underscores if they are used by the object file format, and
1098 converts C++ mangled symbol names into user readable names.
1099 Different compilers have different mangling styles. The optional
1100 demangling style argument can be used to choose an appropriate
1101 demangling style for your compiler. The linker will demangle by
1102 default unless the environment variable COLLECT_NO_DEMANGLE is set.
1103 These options may be used to override the default.
1104 -Ifile
1106 --dynamic-linker=file
1107 Set the name of the dynamic linker. This is only meaningful when
1108 generating dynamically linked ELF executables. The default dynamic
1109 linker is normally correct; don't use this unless you know what you
1110 are doing.
1111 --no-dynamic-linker
1113 When producing an executable file, omit the request for a dynamic
1114 linker to be used at load-time. This is only meaningful for ELF
1115 executables that contain dynamic relocations, and usually requires
1116 entry point code that is capable of processing these relocations.
1117 --embedded-relocs
1119 This option is similar to the --emit-relocs option except that the
1120 relocs are stored in a target specific section. This option is
1121 only supported by the BFIN, CR16 and M68K targets.
1122 --disable-multiple-abs-defs
1124 Do not allow multiple definitions with symbols included in filename
1125 invoked by -R or --just-symbols
1126 --fatal-warnings
1128 --no-fatal-warnings
1129 Treat all warnings as errors. The default behaviour can be
1130 restored with the option --no-fatal-warnings.
1131 --force-exe-suffix
1133 Make sure that an output file has a .exe suffix.
1134 If a successfully built fully linked output file does not have a
1136 ".exe" or ".dll" suffix, this option forces the linker to copy the
1137 output file to one of the same name with a ".exe" suffix. This
1138 option is useful when using unmodified Unix makefiles on a
1139 Microsoft Windows host, since some versions of Windows won't run an
1140 image unless it ends in a ".exe" suffix.
1141 --gc-sections
1143 --no-gc-sections
1144 Enable garbage collection of unused input sections. It is ignored
1145 on targets that do not support this option. The default behaviour
1146 (of not performing this garbage collection) can be restored by
1147 specifying --no-gc-sections on the command line. Note that garbage
1148 collection for COFF and PE format targets is supported, but the
1149 implementation is currently considered to be experimental.
1150 --gc-sections decides which input sections are used by examining
1152 symbols and relocations. The section containing the entry symbol
1153 and all sections containing symbols undefined on the command-line
1154 will be kept, as will sections containing symbols referenced by
1155 dynamic objects. Note that when building shared libraries, the
1156 linker must assume that any visible symbol is referenced. Once
1157 this initial set of sections has been determined, the linker
1158 recursively marks as used any section referenced by their
1159 relocations. See --entry and --undefined.
1160 This option can be set when doing a partial link (enabled with
1162 option -r). In this case the root of symbols kept must be
1163 explicitly specified either by an --entry or --undefined option or
1164 by a "ENTRY" command in the linker script.
1165 --print-gc-sections
1167 --no-print-gc-sections
1168 List all sections removed by garbage collection. The listing is
1169 printed on stderr. This option is only effective if garbage
1170 collection has been enabled via the --gc-sections) option. The
1171 default behaviour (of not listing the sections that are removed)
1172 can be restored by specifying --no-print-gc-sections on the command
1173 line.
1174 --gc-keep-exported
1176 When --gc-sections is enabled, this option prevents garbage
1177 collection of unused input sections that contain global symbols
1178 having default or protected visibility. This option is intended to
1179 be used for executables where unreferenced sections would otherwise
1180 be garbage collected regardless of the external visibility of
1181 contained symbols. Note that this option has no effect when
1182 linking shared objects since it is already the default behaviour.
1183 This option is only supported for ELF format targets.
1184 --print-output-format
1186 Print the name of the default output format (perhaps influenced by
1187 other command-line options). This is the string that would appear
1188 in an "OUTPUT_FORMAT" linker script command.
1189 --print-memory-usage
1191 Print used size, total size and used size of memory regions created
1192 with the MEMORY command. This is useful on embedded targets to
1193 have a quick view of amount of free memory. The format of the
1194 output has one headline and one line per region. It is both human
1195 readable and easily parsable by tools. Here is an example of an
1196 output:
1197 Memory region Used Size Region Size %age Used
1199 ROM: 256 KB 1 MB 25.00%
1200 RAM: 32 B 2 GB 0.00%
1201 --help
1203 Print a summary of the command-line options on the standard output
1204 and exit.
1205 --target-help
1207 Print a summary of all target specific options on the standard
1208 output and exit.
1209 -Map=mapfile
1211 Print a link map to the file mapfile. See the description of the
1212 -M option, above.
1213 --no-keep-memory
1215 ld normally optimizes for speed over memory usage by caching the
1216 symbol tables of input files in memory. This option tells ld to
1217 instead optimize for memory usage, by rereading the symbol tables
1218 as necessary. This may be required if ld runs out of memory space
1219 while linking a large executable.
1220 --no-undefined
1222 -z defs
1223 Report unresolved symbol references from regular object files.
1224 This is done even if the linker is creating a non-symbolic shared
1225 library. The switch --[no-]allow-shlib-undefined controls the
1226 behaviour for reporting unresolved references found in shared
1227 libraries being linked in.
1228 The effects of this option can be reverted by using "-z undefs".
1230 --allow-multiple-definition
1232 -z muldefs
1233 Normally when a symbol is defined multiple times, the linker will
1234 report a fatal error. These options allow multiple definitions and
1235 the first definition will be used.
1236 --allow-shlib-undefined
1238 --no-allow-shlib-undefined
1239 Allows or disallows undefined symbols in shared libraries. This
1240 switch is similar to --no-undefined except that it determines the
1241 behaviour when the undefined symbols are in a shared library rather
1242 than a regular object file. It does not affect how undefined
1243 symbols in regular object files are handled.
1244 The default behaviour is to report errors for any undefined symbols
1246 referenced in shared libraries if the linker is being used to
1247 create an executable, but to allow them if the linker is being used
1248 to create a shared library.
1249 The reasons for allowing undefined symbol references in shared
1251 libraries specified at link time are that:
1252 · A shared library specified at link time may not be the same as
1254 the one that is available at load time, so the symbol might
1255 actually be resolvable at load time.
1256 · There are some operating systems, eg BeOS and HPPA, where
1258 undefined symbols in shared libraries are normal.
1259 The BeOS kernel for example patches shared libraries at load
1261 time to select whichever function is most appropriate for the
1262 current architecture. This is used, for example, to
1263 dynamically select an appropriate memset function.
1264 --no-undefined-version
1266 Normally when a symbol has an undefined version, the linker will
1267 ignore it. This option disallows symbols with undefined version and
1268 a fatal error will be issued instead.
1269 --default-symver
1271 Create and use a default symbol version (the soname) for
1272 unversioned exported symbols.
1273 --default-imported-symver
1275 Create and use a default symbol version (the soname) for
1276 unversioned imported symbols.
1277 --no-warn-mismatch
1279 Normally ld will give an error if you try to link together input
1280 files that are mismatched for some reason, perhaps because they
1281 have been compiled for different processors or for different
1282 endiannesses. This option tells ld that it should silently permit
1283 such possible errors. This option should only be used with care,
1284 in cases when you have taken some special action that ensures that
1285 the linker errors are inappropriate.
1286 --no-warn-search-mismatch
1288 Normally ld will give a warning if it finds an incompatible library
1289 during a library search. This option silences the warning.
1290 --no-whole-archive
1292 Turn off the effect of the --whole-archive option for subsequent
1293 archive files.
1294 --noinhibit-exec
1296 Retain the executable output file whenever it is still usable.
1297 Normally, the linker will not produce an output file if it
1298 encounters errors during the link process; it exits without writing
1299 an output file when it issues any error whatsoever.
1300 -nostdlib
1302 Only search library directories explicitly specified on the command
1303 line. Library directories specified in linker scripts (including
1304 linker scripts specified on the command line) are ignored.
1305 --oformat=output-format
1307 ld may be configured to support more than one kind of object file.
1308 If your ld is configured this way, you can use the --oformat option
1309 to specify the binary format for the output object file. Even when
1310 ld is configured to support alternative object formats, you don't
1311 usually need to specify this, as ld should be configured to produce
1312 as a default output format the most usual format on each machine.
1313 output-format is a text string, the name of a particular format
1314 supported by the BFD libraries. (You can list the available binary
1315 formats with objdump -i.) The script command "OUTPUT_FORMAT" can
1316 also specify the output format, but this option overrides it.
1317 --out-implib file
1319 Create an import library in file corresponding to the executable
1320 the linker is generating (eg. a DLL or ELF program). This import
1321 library (which should be called "*.dll.a" or "*.a" for DLLs) may be
1322 used to link clients against the generated executable; this
1323 behaviour makes it possible to skip a separate import library
1324 creation step (eg. "dlltool" for DLLs). This option is only
1325 available for the i386 PE and ELF targetted ports of the linker.
1326 -pie
1328 --pic-executable
1329 Create a position independent executable. This is currently only
1330 supported on ELF platforms. Position independent executables are
1331 similar to shared libraries in that they are relocated by the
1332 dynamic linker to the virtual address the OS chooses for them
1333 (which can vary between invocations). Like normal dynamically
1334 linked executables they can be executed and symbols defined in the
1335 executable cannot be overridden by shared libraries.
1336 -qmagic
1338 This option is ignored for Linux compatibility.
1339 -Qy This option is ignored for SVR4 compatibility.
1341 --relax
1343 --no-relax
1344 An option with machine dependent effects. This option is only
1345 supported on a few targets.
1346 On some platforms the --relax option performs target specific,
1348 global optimizations that become possible when the linker resolves
1349 addressing in the program, such as relaxing address modes,
1350 synthesizing new instructions, selecting shorter version of current
1351 instructions, and combining constant values.
1352 On some platforms these link time global optimizations may make
1354 symbolic debugging of the resulting executable impossible. This is
1355 known to be the case for the Matsushita MN10200 and MN10300 family
1356 of processors.
1357 On platforms where this is not supported, --relax is accepted, but
1359 ignored.
1360 On platforms where --relax is accepted the option --no-relax can be
1362 used to disable the feature.
1363 --retain-symbols-file=filename
1365 Retain only the symbols listed in the file filename, discarding all
1366 others. filename is simply a flat file, with one symbol name per
1367 line. This option is especially useful in environments (such as
1368 VxWorks) where a large global symbol table is accumulated
1369 gradually, to conserve run-time memory.
1370 --retain-symbols-file does not discard undefined symbols, or
1372 symbols needed for relocations.
1373 You may only specify --retain-symbols-file once in the command
1375 line. It overrides -s and -S.
1376 -rpath=dir
1378 Add a directory to the runtime library search path. This is used
1379 when linking an ELF executable with shared objects. All -rpath
1380 arguments are concatenated and passed to the runtime linker, which
1381 uses them to locate shared objects at runtime. The -rpath option
1382 is also used when locating shared objects which are needed by
1383 shared objects explicitly included in the link; see the description
1384 of the -rpath-link option. If -rpath is not used when linking an
1385 ELF executable, the contents of the environment variable
1386 "LD_RUN_PATH" will be used if it is defined.
1387 The -rpath option may also be used on SunOS. By default, on SunOS,
1389 the linker will form a runtime search path out of all the -L
1390 options it is given. If a -rpath option is used, the runtime
1391 search path will be formed exclusively using the -rpath options,
1392 ignoring the -L options. This can be useful when using gcc, which
1393 adds many -L options which may be on NFS mounted file systems.
1394 For compatibility with other ELF linkers, if the -R option is
1396 followed by a directory name, rather than a file name, it is
1397 treated as the -rpath option.
1398 -rpath-link=dir
1400 When using ELF or SunOS, one shared library may require another.
1401 This happens when an "ld -shared" link includes a shared library as
1402 one of the input files.
1403 When the linker encounters such a dependency when doing a non-
1405 shared, non-relocatable link, it will automatically try to locate
1406 the required shared library and include it in the link, if it is
1407 not included explicitly. In such a case, the -rpath-link option
1408 specifies the first set of directories to search. The -rpath-link
1409 option may specify a sequence of directory names either by
1410 specifying a list of names separated by colons, or by appearing
1411 multiple times.
1412 The tokens $ORIGIN and $LIB can appear in these search directories.
1414 They will be replaced by the full path to the directory containing
1415 the program or shared object in the case of $ORIGIN and either lib
1416 - for 32-bit binaries - or lib64 - for 64-bit binaries - in the
1417 case of $LIB.
1418 The alternative form of these tokens - ${ORIGIN} and ${LIB} can
1420 also be used. The token $PLATFORM is not supported.
1421 This option should be used with caution as it overrides the search
1423 path that may have been hard compiled into a shared library. In
1424 such a case it is possible to use unintentionally a different
1425 search path than the runtime linker would do.
1426 The linker uses the following search paths to locate required
1428 shared libraries:
1429 1. Any directories specified by -rpath-link options.
1431 2. Any directories specified by -rpath options. The difference
1433 between -rpath and -rpath-link is that directories specified by
1434 -rpath options are included in the executable and used at
1435 runtime, whereas the -rpath-link option is only effective at
1436 link time. Searching -rpath in this way is only supported by
1437 native linkers and cross linkers which have been configured
1438 with the --with-sysroot option.
1439 3. On an ELF system, for native linkers, if the -rpath and
1441 -rpath-link options were not used, search the contents of the
1442 environment variable "LD_RUN_PATH".
1443 4. On SunOS, if the -rpath option was not used, search any
1445 directories specified using -L options.
1446 5. For a native linker, search the contents of the environment
1448 variable "LD_LIBRARY_PATH".
1449 6. For a native ELF linker, the directories in "DT_RUNPATH" or
1451 "DT_RPATH" of a shared library are searched for shared
1452 libraries needed by it. The "DT_RPATH" entries are ignored if
1453 "DT_RUNPATH" entries exist.
1454 7. The default directories, normally /lib and /usr/lib.
1456 8. For a native linker on an ELF system, if the file
1458 /etc/ld.so.conf exists, the list of directories found in that
1459 file.
1460 If the required shared library is not found, the linker will issue
1462 a warning and continue with the link.
1463 -shared
1465 -Bshareable
1466 Create a shared library. This is currently only supported on ELF,
1467 XCOFF and SunOS platforms. On SunOS, the linker will automatically
1468 create a shared library if the -e option is not used and there are
1469 undefined symbols in the link.
1470 --sort-common
1472 --sort-common=ascending
1473 --sort-common=descending
1474 This option tells ld to sort the common symbols by alignment in
1475 ascending or descending order when it places them in the
1476 appropriate output sections. The symbol alignments considered are
1477 sixteen-byte or larger, eight-byte, four-byte, two-byte, and one-
1478 byte. This is to prevent gaps between symbols due to alignment
1479 constraints. If no sorting order is specified, then descending
1480 order is assumed.
1481 --sort-section=name
1483 This option will apply "SORT_BY_NAME" to all wildcard section
1484 patterns in the linker script.
1485 --sort-section=alignment
1487 This option will apply "SORT_BY_ALIGNMENT" to all wildcard section
1488 patterns in the linker script.
1489 --spare-dynamic-tags=count
1491 This option specifies the number of empty slots to leave in the
1492 .dynamic section of ELF shared objects. Empty slots may be needed
1493 by post processing tools, such as the prelinker. The default is 5.
1494 --split-by-file[=size]
1496 Similar to --split-by-reloc but creates a new output section for
1497 each input file when size is reached. size defaults to a size of 1
1498 if not given.
1499 --split-by-reloc[=count]
1501 Tries to creates extra sections in the output file so that no
1502 single output section in the file contains more than count
1503 relocations. This is useful when generating huge relocatable files
1504 for downloading into certain real time kernels with the COFF object
1505 file format; since COFF cannot represent more than 65535
1506 relocations in a single section. Note that this will fail to work
1507 with object file formats which do not support arbitrary sections.
1508 The linker will not split up individual input sections for
1509 redistribution, so if a single input section contains more than
1510 count relocations one output section will contain that many
1511 relocations. count defaults to a value of 32768.
1512 --stats
1514 Compute and display statistics about the operation of the linker,
1515 such as execution time and memory usage.
1516 --sysroot=directory
1518 Use directory as the location of the sysroot, overriding the
1519 configure-time default. This option is only supported by linkers
1520 that were configured using --with-sysroot.
1521 --task-link
1523 This is used by COFF/PE based targets to create a task-linked
1524 object file where all of the global symbols have been converted to
1525 statics.
1526 --traditional-format
1528 For some targets, the output of ld is different in some ways from
1529 the output of some existing linker. This switch requests ld to use
1530 the traditional format instead.
1531 For example, on SunOS, ld combines duplicate entries in the symbol
1533 string table. This can reduce the size of an output file with full
1534 debugging information by over 30 percent. Unfortunately, the SunOS
1535 "dbx" program can not read the resulting program ("gdb" has no
1536 trouble). The --traditional-format switch tells ld to not combine
1537 duplicate entries.
1538 --section-start=sectionname=org
1540 Locate a section in the output file at the absolute address given
1541 by org. You may use this option as many times as necessary to
1542 locate multiple sections in the command line. org must be a single
1543 hexadecimal integer; for compatibility with other linkers, you may
1544 omit the leading 0x usually associated with hexadecimal values.
1545 Note: there should be no white space between sectionname, the
1546 equals sign ("="), and org.
1547 -Tbss=org
1549 -Tdata=org
1550 -Ttext=org
1551 Same as --section-start, with ".bss", ".data" or ".text" as the
1552 sectionname.
1553 -Ttext-segment=org
1555 When creating an ELF executable, it will set the address of the
1556 first byte of the text segment.
1557 -Trodata-segment=org
1559 When creating an ELF executable or shared object for a target where
1560 the read-only data is in its own segment separate from the
1561 executable text, it will set the address of the first byte of the
1562 read-only data segment.
1563 -Tldata-segment=org
1565 When creating an ELF executable or shared object for x86-64 medium
1566 memory model, it will set the address of the first byte of the
1567 ldata segment.
1568 --unresolved-symbols=method
1570 Determine how to handle unresolved symbols. There are four
1571 possible values for method:
1572 ignore-all
1574 Do not report any unresolved symbols.
1575 report-all
1577 Report all unresolved symbols. This is the default.
1578 ignore-in-object-files
1580 Report unresolved symbols that are contained in shared
1581 libraries, but ignore them if they come from regular object
1582 files.
1583 ignore-in-shared-libs
1585 Report unresolved symbols that come from regular object files,
1586 but ignore them if they come from shared libraries. This can
1587 be useful when creating a dynamic binary and it is known that
1588 all the shared libraries that it should be referencing are
1589 included on the linker's command line.
1590 The behaviour for shared libraries on their own can also be
1592 controlled by the --[no-]allow-shlib-undefined option.
1593 Normally the linker will generate an error message for each
1595 reported unresolved symbol but the option --warn-unresolved-symbols
1596 can change this to a warning.
1597 --dll-verbose
1599 --verbose[=NUMBER]
1600 Display the version number for ld and list the linker emulations
1601 supported. Display which input files can and cannot be opened.
1602 Display the linker script being used by the linker. If the optional
1603 NUMBER argument > 1, plugin symbol status will also be displayed.
1604 --version-script=version-scriptfile
1606 Specify the name of a version script to the linker. This is
1607 typically used when creating shared libraries to specify additional
1608 information about the version hierarchy for the library being
1609 created. This option is only fully supported on ELF platforms
1610 which support shared libraries; see VERSION. It is partially
1611 supported on PE platforms, which can use version scripts to filter
1612 symbol visibility in auto-export mode: any symbols marked local in
1613 the version script will not be exported.
1614 --warn-common
1616 Warn when a common symbol is combined with another common symbol or
1617 with a symbol definition. Unix linkers allow this somewhat sloppy
1618 practice, but linkers on some other operating systems do not. This
1619 option allows you to find potential problems from combining global
1620 symbols. Unfortunately, some C libraries use this practice, so you
1621 may get some warnings about symbols in the libraries as well as in
1622 your programs.
1623 There are three kinds of global symbols, illustrated here by C
1625 examples:
1626 int i = 1;
1628 A definition, which goes in the initialized data section of the
1629 output file.
1630 extern int i;
1632 An undefined reference, which does not allocate space. There
1633 must be either a definition or a common symbol for the variable
1634 somewhere.
1635 int i;
1637 A common symbol. If there are only (one or more) common
1638 symbols for a variable, it goes in the uninitialized data area
1639 of the output file. The linker merges multiple common symbols
1640 for the same variable into a single symbol. If they are of
1641 different sizes, it picks the largest size. The linker turns a
1642 common symbol into a declaration, if there is a definition of
1643 the same variable.
1644 The --warn-common option can produce five kinds of warnings. Each
1646 warning consists of a pair of lines: the first describes the symbol
1647 just encountered, and the second describes the previous symbol
1648 encountered with the same name. One or both of the two symbols
1649 will be a common symbol.
1650 1. Turning a common symbol into a reference, because there is
1652 already a definition for the symbol.
1653 <file>(<section>): warning: common of `<symbol>'
1655 overridden by definition
1656 <file>(<section>): warning: defined here
1657 2. Turning a common symbol into a reference, because a later
1659 definition for the symbol is encountered. This is the same as
1660 the previous case, except that the symbols are encountered in a
1661 different order.
1662 <file>(<section>): warning: definition of `<symbol>'
1664 overriding common
1665 <file>(<section>): warning: common is here
1666 3. Merging a common symbol with a previous same-sized common
1668 symbol.
1669 <file>(<section>): warning: multiple common
1671 of `<symbol>'
1672 <file>(<section>): warning: previous common is here
1673 4. Merging a common symbol with a previous larger common symbol.
1675 <file>(<section>): warning: common of `<symbol>'
1677 overridden by larger common
1678 <file>(<section>): warning: larger common is here
1679 5. Merging a common symbol with a previous smaller common symbol.
1681 This is the same as the previous case, except that the symbols
1682 are encountered in a different order.
1683 <file>(<section>): warning: common of `<symbol>'
1685 overriding smaller common
1686 <file>(<section>): warning: smaller common is here
1687 --warn-constructors
1689 Warn if any global constructors are used. This is only useful for
1690 a few object file formats. For formats like COFF or ELF, the
1691 linker can not detect the use of global constructors.
1692 --warn-multiple-gp
1694 Warn if multiple global pointer values are required in the output
1695 file. This is only meaningful for certain processors, such as the
1696 Alpha. Specifically, some processors put large-valued constants in
1697 a special section. A special register (the global pointer) points
1698 into the middle of this section, so that constants can be loaded
1699 efficiently via a base-register relative addressing mode. Since
1700 the offset in base-register relative mode is fixed and relatively
1701 small (e.g., 16 bits), this limits the maximum size of the constant
1702 pool. Thus, in large programs, it is often necessary to use
1703 multiple global pointer values in order to be able to address all
1704 possible constants. This option causes a warning to be issued
1705 whenever this case occurs.
1706 --warn-once
1708 Only warn once for each undefined symbol, rather than once per
1709 module which refers to it.
1710 --warn-section-align
1712 Warn if the address of an output section is changed because of
1713 alignment. Typically, the alignment will be set by an input
1714 section. The address will only be changed if it not explicitly
1715 specified; that is, if the "SECTIONS" command does not specify a
1716 start address for the section.
1717 --warn-shared-textrel
1719 Warn if the linker adds a DT_TEXTREL to a shared object.
1720 --warn-alternate-em
1722 Warn if an object has alternate ELF machine code.
1723 --warn-unresolved-symbols
1725 If the linker is going to report an unresolved symbol (see the
1726 option --unresolved-symbols) it will normally generate an error.
1727 This option makes it generate a warning instead.
1728 --error-unresolved-symbols
1730 This restores the linker's default behaviour of generating errors
1731 when it is reporting unresolved symbols.
1732 --whole-archive
1734 For each archive mentioned on the command line after the
1735 --whole-archive option, include every object file in the archive in
1736 the link, rather than searching the archive for the required object
1737 files. This is normally used to turn an archive file into a shared
1738 library, forcing every object to be included in the resulting
1739 shared library. This option may be used more than once.
1740 Two notes when using this option from gcc: First, gcc doesn't know
1742 about this option, so you have to use -Wl,-whole-archive. Second,
1743 don't forget to use -Wl,-no-whole-archive after your list of
1744 archives, because gcc will add its own list of archives to your
1745 link and you may not want this flag to affect those as well.
1746 --wrap=symbol
1748 Use a wrapper function for symbol. Any undefined reference to
1749 symbol will be resolved to "__wrap_symbol". Any undefined
1750 reference to "__real_symbol" will be resolved to symbol.
1751 This can be used to provide a wrapper for a system function. The
1753 wrapper function should be called "__wrap_symbol". If it wishes to
1754 call the system function, it should call "__real_symbol".
1755 Here is a trivial example:
1757 void *
1759 __wrap_malloc (size_t c)
1760 {
1761 printf ("malloc called with %zu\n", c);
1762 return __real_malloc (c);
1763 }
1764 If you link other code with this file using --wrap malloc, then all
1766 calls to "malloc" will call the function "__wrap_malloc" instead.
1767 The call to "__real_malloc" in "__wrap_malloc" will call the real
1768 "malloc" function.
1769 You may wish to provide a "__real_malloc" function as well, so that
1771 links without the --wrap option will succeed. If you do this, you
1772 should not put the definition of "__real_malloc" in the same file
1773 as "__wrap_malloc"; if you do, the assembler may resolve the call
1774 before the linker has a chance to wrap it to "malloc".
1775 --eh-frame-hdr
1777 --no-eh-frame-hdr
1778 Request (--eh-frame-hdr) or suppress (--no-eh-frame-hdr) the
1779 creation of ".eh_frame_hdr" section and ELF "PT_GNU_EH_FRAME"
1780 segment header.
1781 --no-ld-generated-unwind-info
1783 Request creation of ".eh_frame" unwind info for linker generated
1784 code sections like PLT. This option is on by default if linker
1785 generated unwind info is supported.
1786 --enable-new-dtags
1788 --disable-new-dtags
1789 This linker can create the new dynamic tags in ELF. But the older
1790 ELF systems may not understand them. If you specify
1791 --enable-new-dtags, the new dynamic tags will be created as needed
1792 and older dynamic tags will be omitted. If you specify
1793 --disable-new-dtags, no new dynamic tags will be created. By
1794 default, the new dynamic tags are not created. Note that those
1795 options are only available for ELF systems.
1796 --hash-size=number
1798 Set the default size of the linker's hash tables to a prime number
1799 close to number. Increasing this value can reduce the length of
1800 time it takes the linker to perform its tasks, at the expense of
1801 increasing the linker's memory requirements. Similarly reducing
1802 this value can reduce the memory requirements at the expense of
1803 speed.
1804 --hash-style=style
1806 Set the type of linker's hash table(s). style can be either "sysv"
1807 for classic ELF ".hash" section, "gnu" for new style GNU
1808 ".gnu.hash" section or "both" for both the classic ELF ".hash" and
1809 new style GNU ".gnu.hash" hash tables. The default is "sysv".
1810 --compress-debug-sections=none
1812 --compress-debug-sections=zlib
1813 --compress-debug-sections=zlib-gnu
1814 --compress-debug-sections=zlib-gabi
1815 On ELF platforms, these options control how DWARF debug sections
1816 are compressed using zlib.
1817 --compress-debug-sections=none doesn't compress DWARF debug
1819 sections. --compress-debug-sections=zlib-gnu compresses DWARF
1820 debug sections and renames them to begin with .zdebug instead of
1821 .debug. --compress-debug-sections=zlib-gabi also compresses DWARF
1822 debug sections, but rather than renaming them it sets the
1823 SHF_COMPRESSED flag in the sections' headers.
1824 The --compress-debug-sections=zlib option is an alias for
1826 --compress-debug-sections=zlib-gabi.
1827 Note that this option overrides any compression in input debug
1829 sections, so if a binary is linked with
1830 --compress-debug-sections=none for example, then any compressed
1831 debug sections in input files will be uncompressed before they are
1832 copied into the output binary.
1833 The default compression behaviour varies depending upon the target
1835 involved and the configure options used to build the toolchain.
1836 The default can be determined by examining the output from the
1837 linker's --help option.
1838 --reduce-memory-overheads
1840 This option reduces memory requirements at ld runtime, at the
1841 expense of linking speed. This was introduced to select the old
1842 O(n^2) algorithm for link map file generation, rather than the new
1843 O(n) algorithm which uses about 40% more memory for symbol storage.
1844 Another effect of the switch is to set the default hash table size
1846 to 1021, which again saves memory at the cost of lengthening the
1847 linker's run time. This is not done however if the --hash-size
1848 switch has been used.
1849 The --reduce-memory-overheads switch may be also be used to enable
1851 other tradeoffs in future versions of the linker.
1852 --build-id
1854 --build-id=style
1855 Request the creation of a ".note.gnu.build-id" ELF note section or
1856 a ".buildid" COFF section. The contents of the note are unique
1857 bits identifying this linked file. style can be "uuid" to use 128
1858 random bits, "sha1" to use a 160-bit SHA1 hash on the normative
1859 parts of the output contents, "md5" to use a 128-bit MD5 hash on
1860 the normative parts of the output contents, or "0xhexstring" to use
1861 a chosen bit string specified as an even number of hexadecimal
1862 digits ("-" and ":" characters between digit pairs are ignored).
1863 If style is omitted, "sha1" is used.
1864 The "md5" and "sha1" styles produces an identifier that is always
1866 the same in an identical output file, but will be unique among all
1867 nonidentical output files. It is not intended to be compared as a
1868 checksum for the file's contents. A linked file may be changed
1869 later by other tools, but the build ID bit string identifying the
1870 original linked file does not change.
1871 Passing "none" for style disables the setting from any "--build-id"
1873 options earlier on the command line.
1874 The i386 PE linker supports the -shared option, which causes the output
1876 to be a dynamically linked library (DLL) instead of a normal
1877 executable. You should name the output "*.dll" when you use this
1878 option. In addition, the linker fully supports the standard "*.def"
1879 files, which may be specified on the linker command line like an object
1880 file (in fact, it should precede archives it exports symbols from, to
1881 ensure that they get linked in, just like a normal object file).
1882 In addition to the options common to all targets, the i386 PE linker
1884 support additional command line options that are specific to the i386
1885 PE target. Options that take values may be separated from their values
1886 by either a space or an equals sign.
1887 --add-stdcall-alias
1889 If given, symbols with a stdcall suffix (@nn) will be exported as-
1890 is and also with the suffix stripped. [This option is specific to
1891 the i386 PE targeted port of the linker]
1892 --base-file file
1894 Use file as the name of a file in which to save the base addresses
1895 of all the relocations needed for generating DLLs with dlltool.
1896 [This is an i386 PE specific option]
1897 --dll
1899 Create a DLL instead of a regular executable. You may also use
1900 -shared or specify a "LIBRARY" in a given ".def" file. [This
1901 option is specific to the i386 PE targeted port of the linker]
1902 --enable-long-section-names
1904 --disable-long-section-names
1905 The PE variants of the COFF object format add an extension that
1906 permits the use of section names longer than eight characters, the
1907 normal limit for COFF. By default, these names are only allowed in
1908 object files, as fully-linked executable images do not carry the
1909 COFF string table required to support the longer names. As a GNU
1910 extension, it is possible to allow their use in executable images
1911 as well, or to (probably pointlessly!) disallow it in object
1912 files, by using these two options. Executable images generated
1913 with these long section names are slightly non-standard, carrying
1914 as they do a string table, and may generate confusing output when
1915 examined with non-GNU PE-aware tools, such as file viewers and
1916 dumpers. However, GDB relies on the use of PE long section names
1917 to find Dwarf-2 debug information sections in an executable image
1918 at runtime, and so if neither option is specified on the command-
1919 line, ld will enable long section names, overriding the default and
1920 technically correct behaviour, when it finds the presence of debug
1921 information while linking an executable image and not stripping
1922 symbols. [This option is valid for all PE targeted ports of the
1923 linker]
1924 --enable-stdcall-fixup
1926 --disable-stdcall-fixup
1927 If the link finds a symbol that it cannot resolve, it will attempt
1928 to do "fuzzy linking" by looking for another defined symbol that
1929 differs only in the format of the symbol name (cdecl vs stdcall)
1930 and will resolve that symbol by linking to the match. For example,
1931 the undefined symbol "_foo" might be linked to the function
1932 "_foo@12", or the undefined symbol "_bar@16" might be linked to the
1933 function "_bar". When the linker does this, it prints a warning,
1934 since it normally should have failed to link, but sometimes import
1935 libraries generated from third-party dlls may need this feature to
1936 be usable. If you specify --enable-stdcall-fixup, this feature is
1937 fully enabled and warnings are not printed. If you specify
1938 --disable-stdcall-fixup, this feature is disabled and such
1939 mismatches are considered to be errors. [This option is specific
1940 to the i386 PE targeted port of the linker]
1941 --leading-underscore
1943 --no-leading-underscore
1944 For most targets default symbol-prefix is an underscore and is
1945 defined in target's description. By this option it is possible to
1946 disable/enable the default underscore symbol-prefix.
1947 --export-all-symbols
1949 If given, all global symbols in the objects used to build a DLL
1950 will be exported by the DLL. Note that this is the default if
1951 there otherwise wouldn't be any exported symbols. When symbols are
1952 explicitly exported via DEF files or implicitly exported via
1953 function attributes, the default is to not export anything else
1954 unless this option is given. Note that the symbols "DllMain@12",
1955 "DllEntryPoint@0", "DllMainCRTStartup@12", and "impure_ptr" will
1956 not be automatically exported. Also, symbols imported from other
1957 DLLs will not be re-exported, nor will symbols specifying the DLL's
1958 internal layout such as those beginning with "_head_" or ending
1959 with "_iname". In addition, no symbols from "libgcc", "libstd++",
1960 "libmingw32", or "crtX.o" will be exported. Symbols whose names
1961 begin with "__rtti_" or "__builtin_" will not be exported, to help
1962 with C++ DLLs. Finally, there is an extensive list of cygwin-
1963 private symbols that are not exported (obviously, this applies on
1964 when building DLLs for cygwin targets). These cygwin-excludes are:
1965 "_cygwin_dll_entry@12", "_cygwin_crt0_common@8",
1966 "_cygwin_noncygwin_dll_entry@12", "_fmode", "_impure_ptr",
1967 "cygwin_attach_dll", "cygwin_premain0", "cygwin_premain1",
1968 "cygwin_premain2", "cygwin_premain3", and "environ". [This option
1969 is specific to the i386 PE targeted port of the linker]
1970 --exclude-symbols symbol,symbol,...
1972 Specifies a list of symbols which should not be automatically
1973 exported. The symbol names may be delimited by commas or colons.
1974 [This option is specific to the i386 PE targeted port of the
1975 linker]
1976 --exclude-all-symbols
1978 Specifies no symbols should be automatically exported. [This
1979 option is specific to the i386 PE targeted port of the linker]
1980 --file-alignment
1982 Specify the file alignment. Sections in the file will always begin
1983 at file offsets which are multiples of this number. This defaults
1984 to 512. [This option is specific to the i386 PE targeted port of
1985 the linker]
1986 --heap reserve
1988 --heap reserve,commit
1989 Specify the number of bytes of memory to reserve (and optionally
1990 commit) to be used as heap for this program. The default is 1MB
1991 reserved, 4K committed. [This option is specific to the i386 PE
1992 targeted port of the linker]
1993 --image-base value
1995 Use value as the base address of your program or dll. This is the
1996 lowest memory location that will be used when your program or dll
1997 is loaded. To reduce the need to relocate and improve performance
1998 of your dlls, each should have a unique base address and not
1999 overlap any other dlls. The default is 0x400000 for executables,
2000 and 0x10000000 for dlls. [This option is specific to the i386 PE
2001 targeted port of the linker]
2002 --kill-at
2004 If given, the stdcall suffixes (@nn) will be stripped from symbols
2005 before they are exported. [This option is specific to the i386 PE
2006 targeted port of the linker]
2007 --large-address-aware
2009 If given, the appropriate bit in the "Characteristics" field of the
2010 COFF header is set to indicate that this executable supports
2011 virtual addresses greater than 2 gigabytes. This should be used in
2012 conjunction with the /3GB or /USERVA=value megabytes switch in the
2013 "[operating systems]" section of the BOOT.INI. Otherwise, this bit
2014 has no effect. [This option is specific to PE targeted ports of
2015 the linker]
2016 --disable-large-address-aware
2018 Reverts the effect of a previous --large-address-aware option.
2019 This is useful if --large-address-aware is always set by the
2020 compiler driver (e.g. Cygwin gcc) and the executable does not
2021 support virtual addresses greater than 2 gigabytes. [This option
2022 is specific to PE targeted ports of the linker]
2023 --major-image-version value
2025 Sets the major number of the "image version". Defaults to 1.
2026 [This option is specific to the i386 PE targeted port of the
2027 linker]
2028 --major-os-version value
2030 Sets the major number of the "os version". Defaults to 4. [This
2031 option is specific to the i386 PE targeted port of the linker]
2032 --major-subsystem-version value
2034 Sets the major number of the "subsystem version". Defaults to 4.
2035 [This option is specific to the i386 PE targeted port of the
2036 linker]
2037 --minor-image-version value
2039 Sets the minor number of the "image version". Defaults to 0.
2040 [This option is specific to the i386 PE targeted port of the
2041 linker]
2042 --minor-os-version value
2044 Sets the minor number of the "os version". Defaults to 0. [This
2045 option is specific to the i386 PE targeted port of the linker]
2046 --minor-subsystem-version value
2048 Sets the minor number of the "subsystem version". Defaults to 0.
2049 [This option is specific to the i386 PE targeted port of the
2050 linker]
2051 --output-def file
2053 The linker will create the file file which will contain a DEF file
2054 corresponding to the DLL the linker is generating. This DEF file
2055 (which should be called "*.def") may be used to create an import
2056 library with "dlltool" or may be used as a reference to
2057 automatically or implicitly exported symbols. [This option is
2058 specific to the i386 PE targeted port of the linker]
2059 --enable-auto-image-base
2061 --enable-auto-image-base=value
2062 Automatically choose the image base for DLLs, optionally starting
2063 with base value, unless one is specified using the "--image-base"
2064 argument. By using a hash generated from the dllname to create
2065 unique image bases for each DLL, in-memory collisions and
2066 relocations which can delay program execution are avoided. [This
2067 option is specific to the i386 PE targeted port of the linker]
2068 --disable-auto-image-base
2070 Do not automatically generate a unique image base. If there is no
2071 user-specified image base ("--image-base") then use the platform
2072 default. [This option is specific to the i386 PE targeted port of
2073 the linker]
2074 --dll-search-prefix string
2076 When linking dynamically to a dll without an import library, search
2077 for "<string><basename>.dll" in preference to "lib<basename>.dll".
2078 This behaviour allows easy distinction between DLLs built for the
2079 various "subplatforms": native, cygwin, uwin, pw, etc. For
2080 instance, cygwin DLLs typically use "--dll-search-prefix=cyg".
2081 [This option is specific to the i386 PE targeted port of the
2082 linker]
2083 --enable-auto-import
2085 Do sophisticated linking of "_symbol" to "__imp__symbol" for DATA
2086 imports from DLLs, thus making it possible to bypass the dllimport
2087 mechanism on the user side and to reference unmangled symbol names.
2088 [This option is specific to the i386 PE targeted port of the
2089 linker]
2090 The following remarks pertain to the original implementation of the
2092 feature and are obsolete nowadays for Cygwin and MinGW targets.
2093 Note: Use of the 'auto-import' extension will cause the text
2095 section of the image file to be made writable. This does not
2096 conform to the PE-COFF format specification published by Microsoft.
2097 Note - use of the 'auto-import' extension will also cause read only
2099 data which would normally be placed into the .rdata section to be
2100 placed into the .data section instead. This is in order to work
2101 around a problem with consts that is described here:
2102 http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
2103 Using 'auto-import' generally will 'just work' -- but sometimes you
2105 may see this message:
2106 "variable '<var>' can't be auto-imported. Please read the
2108 documentation for ld's "--enable-auto-import" for details."
2109 This message occurs when some (sub)expression accesses an address
2111 ultimately given by the sum of two constants (Win32 import tables
2112 only allow one). Instances where this may occur include accesses
2113 to member fields of struct variables imported from a DLL, as well
2114 as using a constant index into an array variable imported from a
2115 DLL. Any multiword variable (arrays, structs, long long, etc) may
2116 trigger this error condition. However, regardless of the exact
2117 data type of the offending exported variable, ld will always detect
2118 it, issue the warning, and exit.
2119 There are several ways to address this difficulty, regardless of
2121 the data type of the exported variable:
2122 One way is to use --enable-runtime-pseudo-reloc switch. This leaves
2124 the task of adjusting references in your client code for runtime
2125 environment, so this method works only when runtime environment
2126 supports this feature.
2127 A second solution is to force one of the 'constants' to be a
2129 variable -- that is, unknown and un-optimizable at compile time.
2130 For arrays, there are two possibilities: a) make the indexee (the
2131 array's address) a variable, or b) make the 'constant' index a
2132 variable. Thus:
2133 extern type extern_array[];
2135 extern_array[1] -->
2136 { volatile type *t=extern_array; t[1] }
2137 or
2139 extern type extern_array[];
2141 extern_array[1] -->
2142 { volatile int t=1; extern_array[t] }
2143 For structs (and most other multiword data types) the only option
2145 is to make the struct itself (or the long long, or the ...)
2146 variable:
2147 extern struct s extern_struct;
2149 extern_struct.field -->
2150 { volatile struct s *t=&extern_struct; t->field }
2151 or
2153 extern long long extern_ll;
2155 extern_ll -->
2156 { volatile long long * local_ll=&extern_ll; *local_ll }
2157 A third method of dealing with this difficulty is to abandon
2159 'auto-import' for the offending symbol and mark it with
2160 "__declspec(dllimport)". However, in practice that requires using
2161 compile-time #defines to indicate whether you are building a DLL,
2162 building client code that will link to the DLL, or merely
2163 building/linking to a static library. In making the choice
2164 between the various methods of resolving the 'direct address with
2165 constant offset' problem, you should consider typical real-world
2166 usage:
2167 Original:
2169 --foo.h
2171 extern int arr[];
2172 --foo.c
2173 #include "foo.h"
2174 void main(int argc, char **argv){
2175 printf("%d\n",arr[1]);
2176 }
2177 Solution 1:
2179 --foo.h
2181 extern int arr[];
2182 --foo.c
2183 #include "foo.h"
2184 void main(int argc, char **argv){
2185 /* This workaround is for win32 and cygwin; do not "optimize" */
2186 volatile int *parr = arr;
2187 printf("%d\n",parr[1]);
2188 }
2189 Solution 2:
2191 --foo.h
2193 /* Note: auto-export is assumed (no __declspec(dllexport)) */
2194 #if (defined(_WIN32) || defined(__CYGWIN__)) && \
2195 !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
2196 #define FOO_IMPORT __declspec(dllimport)
2197 #else
2198 #define FOO_IMPORT
2199 #endif
2200 extern FOO_IMPORT int arr[];
2201 --foo.c
2202 #include "foo.h"
2203 void main(int argc, char **argv){
2204 printf("%d\n",arr[1]);
2205 }
2206 A fourth way to avoid this problem is to re-code your library to
2208 use a functional interface rather than a data interface for the
2209 offending variables (e.g. set_foo() and get_foo() accessor
2210 functions).
2211 --disable-auto-import
2213 Do not attempt to do sophisticated linking of "_symbol" to
2214 "__imp__symbol" for DATA imports from DLLs. [This option is
2215 specific to the i386 PE targeted port of the linker]
2216 --enable-runtime-pseudo-reloc
2218 If your code contains expressions described in --enable-auto-import
2219 section, that is, DATA imports from DLL with non-zero offset, this
2220 switch will create a vector of 'runtime pseudo relocations' which
2221 can be used by runtime environment to adjust references to such
2222 data in your client code. [This option is specific to the i386 PE
2223 targeted port of the linker]
2224 --disable-runtime-pseudo-reloc
2226 Do not create pseudo relocations for non-zero offset DATA imports
2227 from DLLs. [This option is specific to the i386 PE targeted port
2228 of the linker]
2229 --enable-extra-pe-debug
2231 Show additional debug info related to auto-import symbol thunking.
2232 [This option is specific to the i386 PE targeted port of the
2233 linker]
2234 --section-alignment
2236 Sets the section alignment. Sections in memory will always begin
2237 at addresses which are a multiple of this number. Defaults to
2238 0x1000. [This option is specific to the i386 PE targeted port of
2239 the linker]
2240 --stack reserve
2242 --stack reserve,commit
2243 Specify the number of bytes of memory to reserve (and optionally
2244 commit) to be used as stack for this program. The default is 2MB
2245 reserved, 4K committed. [This option is specific to the i386 PE
2246 targeted port of the linker]
2247 --subsystem which
2249 --subsystem which:major
2250 --subsystem which:major.minor
2251 Specifies the subsystem under which your program will execute. The
2252 legal values for which are "native", "windows", "console", "posix",
2253 and "xbox". You may optionally set the subsystem version also.
2254 Numeric values are also accepted for which. [This option is
2255 specific to the i386 PE targeted port of the linker]
2256 The following options set flags in the "DllCharacteristics" field
2258 of the PE file header: [These options are specific to PE targeted
2259 ports of the linker]
2260 --high-entropy-va
2262 Image is compatible with 64-bit address space layout randomization
2263 (ASLR).
2264 --dynamicbase
2266 The image base address may be relocated using address space layout
2267 randomization (ASLR). This feature was introduced with MS Windows
2268 Vista for i386 PE targets.
2269 --forceinteg
2271 Code integrity checks are enforced.
2272 --nxcompat
2274 The image is compatible with the Data Execution Prevention. This
2275 feature was introduced with MS Windows XP SP2 for i386 PE targets.
2276 --no-isolation
2278 Although the image understands isolation, do not isolate the image.
2279 --no-seh
2281 The image does not use SEH. No SE handler may be called from this
2282 image.
2283 --no-bind
2285 Do not bind this image.
2286 --wdmdriver
2288 The driver uses the MS Windows Driver Model.
2289 --tsaware
2291 The image is Terminal Server aware.
2292 --insert-timestamp
2294 --no-insert-timestamp
2295 Insert a real timestamp into the image. This is the default
2296 behaviour as it matches legacy code and it means that the image
2297 will work with other, proprietary tools. The problem with this
2298 default is that it will result in slightly different images being
2299 produced each time the same sources are linked. The option
2300 --no-insert-timestamp can be used to insert a zero value for the
2301 timestamp, this ensuring that binaries produced from identical
2302 sources will compare identically.
2303 The C6X uClinux target uses a binary format called DSBT to support
2305 shared libraries. Each shared library in the system needs to have a
2306 unique index; all executables use an index of 0.
2307 --dsbt-size size
2309 This option sets the number of entries in the DSBT of the current
2310 executable or shared library to size. The default is to create a
2311 table with 64 entries.
2312 --dsbt-index index
2314 This option sets the DSBT index of the current executable or shared
2315 library to index. The default is 0, which is appropriate for
2316 generating executables. If a shared library is generated with a
2317 DSBT index of 0, the "R_C6000_DSBT_INDEX" relocs are copied into
2318 the output file.
2319 The --no-merge-exidx-entries switch disables the merging of
2321 adjacent exidx entries in frame unwind info.
2322 The 68HC11 and 68HC12 linkers support specific options to control the
2324 memory bank switching mapping and trampoline code generation.
2325 --no-trampoline
2327 This option disables the generation of trampoline. By default a
2328 trampoline is generated for each far function which is called using
2329 a "jsr" instruction (this happens when a pointer to a far function
2330 is taken).
2331 --bank-window name
2333 This option indicates to the linker the name of the memory region
2334 in the MEMORY specification that describes the memory bank window.
2335 The definition of such region is then used by the linker to compute
2336 paging and addresses within the memory window.
2337 The following options are supported to control handling of GOT
2339 generation when linking for 68K targets.
2340 --got=type
2342 This option tells the linker which GOT generation scheme to use.
2343 type should be one of single, negative, multigot or target. For
2344 more information refer to the Info entry for ld.
2345 The following options are supported to control microMIPS instruction
2347 generation and branch relocation checks for ISA mode transitions when
2348 linking for MIPS targets.
2349 --insn32
2351 --no-insn32
2352 These options control the choice of microMIPS instructions used in
2353 code generated by the linker, such as that in the PLT or lazy
2354 binding stubs, or in relaxation. If --insn32 is used, then the
2355 linker only uses 32-bit instruction encodings. By default or if
2356 --no-insn32 is used, all instruction encodings are used, including
2357 16-bit ones where possible.
2358 --ignore-branch-isa
2360 --no-ignore-branch-isa
2361 These options control branch relocation checks for invalid ISA mode
2362 transitions. If --ignore-branch-isa is used, then the linker
2363 accepts any branch relocations and any ISA mode transition required
2364 is lost in relocation calculation, except for some cases of "BAL"
2365 instructions which meet relaxation conditions and are converted to
2366 equivalent "JALX" instructions as the associated relocation is
2367 calculated. By default or if --no-ignore-branch-isa is used a
2368 check is made causing the loss of an ISA mode transition to produce
2369 an error.
2370
2372 You can change the behaviour of ld with the environment variables
2373 "GNUTARGET", "LDEMULATION" and "COLLECT_NO_DEMANGLE".
2374 "GNUTARGET" determines the input-file object format if you don't use -b
2376 (or its synonym --format). Its value should be one of the BFD names
2377 for an input format. If there is no "GNUTARGET" in the environment, ld
2378 uses the natural format of the target. If "GNUTARGET" is set to
2379 "default" then BFD attempts to discover the input format by examining
2380 binary input files; this method often succeeds, but there are potential
2381 ambiguities, since there is no method of ensuring that the magic number
2382 used to specify object-file formats is unique. However, the
2383 configuration procedure for BFD on each system places the conventional
2384 format for that system first in the search-list, so ambiguities are
2385 resolved in favor of convention.
2386 "LDEMULATION" determines the default emulation if you don't use the -m
2388 option. The emulation can affect various aspects of linker behaviour,
2389 particularly the default linker script. You can list the available
2390 emulations with the --verbose or -V options. If the -m option is not
2391 used, and the "LDEMULATION" environment variable is not defined, the
2392 default emulation depends upon how the linker was configured.
2393 Normally, the linker will default to demangling symbols. However, if
2395 "COLLECT_NO_DEMANGLE" is set in the environment, then it will default
2396 to not demangling symbols. This environment variable is used in a
2397 similar fashion by the "gcc" linker wrapper program. The default may
2398 be overridden by the --demangle and --no-demangle options.
2399
2401 ar(1), nm(1), objcopy(1), objdump(1), readelf(1) and the Info entries
2402 for binutils and ld.
2403
2405 Copyright (c) 1991-2018 Free Software Foundation, Inc.
2406 Permission is granted to copy, distribute and/or modify this document
2408 under the terms of the GNU Free Documentation License, Version 1.3 or
2409 any later version published by the Free Software Foundation; with no
2410 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
2411 Texts. A copy of the license is included in the section entitled "GNU
2412 Free Documentation License".
2413binutils-2.31.1 2019-05-27 LD(1)