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 -A architecture
156 --architecture=architecture
157 In the current release of ld, this option is useful only for the
158 Intel 960 family of architectures. In that ld configuration, the
159 architecture argument identifies the particular architecture in the
160 960 family, enabling some safeguards and modifying the archive-
161 library search path.
162 Future releases of ld may support similar functionality for other
164 architecture families.
165 -b input-format
167 --format=input-format
168 ld may be configured to support more than one kind of object file.
169 If your ld is configured this way, you can use the -b option to
170 specify the binary format for input object files that follow this
171 option on the command line. Even when ld is configured to support
172 alternative object formats, you don't usually need to specify this,
173 as ld should be configured to expect as a default input format the
174 most usual format on each machine. input-format is a text string,
175 the name of a particular format supported by the BFD libraries.
176 (You can list the available binary formats with objdump -i.)
177 You may want to use this option if you are linking files with an
179 unusual binary format. You can also use -b to switch formats
180 explicitly (when linking object files of different formats), by
181 including -b input-format before each group of object files in a
182 particular format.
183 The default format is taken from the environment variable
185 "GNUTARGET".
186 You can also define the input format from a script, using the
188 command "TARGET";
189 -c MRI-commandfile
191 --mri-script=MRI-commandfile
192 For compatibility with linkers produced by MRI, ld accepts script
193 files written in an alternate, restricted command language,
194 described in the MRI Compatible Script Files section of GNU ld
195 documentation. Introduce MRI script files with the option -c; use
196 the -T option to run linker scripts written in the general-purpose
197 ld scripting language. If MRI-cmdfile does not exist, ld looks for
198 it in the directories specified by any -L options.
199 -d
201 -dc
202 -dp These three options are equivalent; multiple forms are supported
203 for compatibility with other linkers. They assign space to common
204 symbols even if a relocatable output file is specified (with -r).
205 The script command "FORCE_COMMON_ALLOCATION" has the same effect.
206 --depaudit AUDITLIB
208 -P AUDITLIB
209 Adds AUDITLIB to the "DT_DEPAUDIT" entry of the dynamic section.
210 AUDITLIB is not checked for existence, nor will it use the
211 DT_SONAME specified in the library. If specified multiple times
212 "DT_DEPAUDIT" will contain a colon separated list of audit
213 interfaces to use. This option is only meaningful on ELF platforms
214 supporting the rtld-audit interface. The -P option is provided for
215 Solaris compatibility.
216 -e entry
218 --entry=entry
219 Use entry as the explicit symbol for beginning execution of your
220 program, rather than the default entry point. If there is no
221 symbol named entry, the linker will try to parse entry as a number,
222 and use that as the entry address (the number will be interpreted
223 in base 10; you may use a leading 0x for base 16, or a leading 0
224 for base 8).
225 --exclude-libs lib,lib,...
227 Specifies a list of archive libraries from which symbols should not
228 be automatically exported. The library names may be delimited by
229 commas or colons. Specifying "--exclude-libs ALL" excludes symbols
230 in all archive libraries from automatic export. This option is
231 available only for the i386 PE targeted port of the linker and for
232 ELF targeted ports. For i386 PE, symbols explicitly listed in a
233 .def file are still exported, regardless of this option. For ELF
234 targeted ports, symbols affected by this option will be treated as
235 hidden.
236 --exclude-modules-for-implib module,module,...
238 Specifies a list of object files or archive members, from which
239 symbols should not be automatically exported, but which should be
240 copied wholesale into the import library being generated during the
241 link. The module names may be delimited by commas or colons, and
242 must match exactly the filenames used by ld to open the files; for
243 archive members, this is simply the member name, but for object
244 files the name listed must include and match precisely any path
245 used to specify the input file on the linker's command-line. This
246 option is available only for the i386 PE targeted port of the
247 linker. Symbols explicitly listed in a .def file are still
248 exported, regardless of this option.
249 -E
251 --export-dynamic
252 --no-export-dynamic
253 When creating a dynamically linked executable, using the -E option
254 or the --export-dynamic option causes the linker to add all symbols
255 to the dynamic symbol table. The dynamic symbol table is the set
256 of symbols which are visible from dynamic objects at run time.
257 If you do not use either of these options (or use the
259 --no-export-dynamic option to restore the default behavior), the
260 dynamic symbol table will normally contain only those symbols which
261 are referenced by some dynamic object mentioned in the link.
262 If you use "dlopen" to load a dynamic object which needs to refer
264 back to the symbols defined by the program, rather than some other
265 dynamic object, then you will probably need to use this option when
266 linking the program itself.
267 You can also use the dynamic list to control what symbols should be
269 added to the dynamic symbol table if the output format supports it.
270 See the description of --dynamic-list.
271 Note that this option is specific to ELF targeted ports. PE
273 targets support a similar function to export all symbols from a DLL
274 or EXE; see the description of --export-all-symbols below.
275 -EB Link big-endian objects. This affects the default output format.
277 -EL Link little-endian objects. This affects the default output
279 format.
280 -f name
282 --auxiliary=name
283 When creating an ELF shared object, set the internal DT_AUXILIARY
284 field to the specified name. This tells the dynamic linker that
285 the symbol table of the shared object should be used as an
286 auxiliary filter on the symbol table of the shared object name.
287 If you later link a program against this filter object, then, when
289 you run the program, the dynamic linker will see the DT_AUXILIARY
290 field. If the dynamic linker resolves any symbols from the filter
291 object, it will first check whether there is a definition in the
292 shared object name. If there is one, it will be used instead of
293 the definition in the filter object. The shared object name need
294 not exist. Thus the shared object name may be used to provide an
295 alternative implementation of certain functions, perhaps for
296 debugging or for machine specific performance.
297 This option may be specified more than once. The DT_AUXILIARY
299 entries will be created in the order in which they appear on the
300 command line.
301 -F name
303 --filter=name
304 When creating an ELF shared object, set the internal DT_FILTER
305 field to the specified name. This tells the dynamic linker that
306 the symbol table of the shared object which is being created should
307 be used as a filter on the symbol table of the shared object name.
308 If you later link a program against this filter object, then, when
310 you run the program, the dynamic linker will see the DT_FILTER
311 field. The dynamic linker will resolve symbols according to the
312 symbol table of the filter object as usual, but it will actually
313 link to the definitions found in the shared object name. Thus the
314 filter object can be used to select a subset of the symbols
315 provided by the object name.
316 Some older linkers used the -F option throughout a compilation
318 toolchain for specifying object-file format for both input and
319 output object files. The GNU linker uses other mechanisms for this
320 purpose: the -b, --format, --oformat options, the "TARGET" command
321 in linker scripts, and the "GNUTARGET" environment variable. The
322 GNU linker will ignore the -F option when not creating an ELF
323 shared object.
324 -fini=name
326 When creating an ELF executable or shared object, call NAME when
327 the executable or shared object is unloaded, by setting DT_FINI to
328 the address of the function. By default, the linker uses "_fini"
329 as the function to call.
330 -g Ignored. Provided for compatibility with other tools.
332 -G value
334 --gpsize=value
335 Set the maximum size of objects to be optimized using the GP
336 register to size. This is only meaningful for object file formats
337 such as MIPS ELF that support putting large and small objects into
338 different sections. This is ignored for other object file formats.
339 -h name
341 -soname=name
342 When creating an ELF shared object, set the internal DT_SONAME
343 field to the specified name. When an executable is linked with a
344 shared object which has a DT_SONAME field, then when the executable
345 is run the dynamic linker will attempt to load the shared object
346 specified by the DT_SONAME field rather than the using the file
347 name given to the linker.
348 -i Perform an incremental link (same as option -r).
350 -init=name
352 When creating an ELF executable or shared object, call NAME when
353 the executable or shared object is loaded, by setting DT_INIT to
354 the address of the function. By default, the linker uses "_init"
355 as the function to call.
356 -l namespec
358 --library=namespec
359 Add the archive or object file specified by namespec to the list of
360 files to link. This option may be used any number of times. If
361 namespec is of the form :filename, ld will search the library path
362 for a file called filename, otherwise it will search the library
363 path for a file called libnamespec.a.
364 On systems which support shared libraries, ld may also search for
366 files other than libnamespec.a. Specifically, on ELF and SunOS
367 systems, ld will search a directory for a library called
368 libnamespec.so before searching for one called libnamespec.a. (By
369 convention, a ".so" extension indicates a shared library.) Note
370 that this behavior does not apply to :filename, which always
371 specifies a file called filename.
372 The linker will search an archive only once, at the location where
374 it is specified on the command line. If the archive defines a
375 symbol which was undefined in some object which appeared before the
376 archive on the command line, the linker will include the
377 appropriate file(s) from the archive. However, an undefined symbol
378 in an object appearing later on the command line will not cause the
379 linker to search the archive again.
380 See the -( option for a way to force the linker to search archives
382 multiple times.
383 You may list the same archive multiple times on the command line.
385 This type of archive searching is standard for Unix linkers.
387 However, if you are using ld on AIX, note that it is different from
388 the behaviour of the AIX linker.
389 -L searchdir
391 --library-path=searchdir
392 Add path searchdir to the list of paths that ld will search for
393 archive libraries and ld control scripts. You may use this option
394 any number of times. The directories are searched in the order in
395 which they are specified on the command line. Directories
396 specified on the command line are searched before the default
397 directories. All -L options apply to all -l options, regardless of
398 the order in which the options appear. -L options do not affect
399 how ld searches for a linker script unless -T option is specified.
400 If searchdir begins with "=" or $SYSROOT, then this prefix will be
402 replaced by the sysroot prefix, controlled by the --sysroot option,
403 or specified when the linker is configured.
404 The default set of paths searched (without being specified with -L)
406 depends on which emulation mode ld is using, and in some cases also
407 on how it was configured.
408 The paths can also be specified in a link script with the
410 "SEARCH_DIR" command. Directories specified this way are searched
411 at the point in which the linker script appears in the command
412 line.
413 -m emulation
415 Emulate the emulation linker. You can list the available
416 emulations with the --verbose or -V options.
417 If the -m option is not used, the emulation is taken from the
419 "LDEMULATION" environment variable, if that is defined.
420 Otherwise, the default emulation depends upon how the linker was
422 configured.
423 -M
425 --print-map
426 Print a link map to the standard output. A link map provides
427 information about the link, including the following:
428 · Where object files are mapped into memory.
430 · How common symbols are allocated.
432 · All archive members included in the link, with a mention of the
434 symbol which caused the archive member to be brought in.
435 · The values assigned to symbols.
437 Note - symbols whose values are computed by an expression which
439 involves a reference to a previous value of the same symbol may
440 not have correct result displayed in the link map. This is
441 because the linker discards intermediate results and only
442 retains the final value of an expression. Under such
443 circumstances the linker will display the final value enclosed
444 by square brackets. Thus for example a linker script
445 containing:
446 foo = 1
448 foo = foo * 4
449 foo = foo + 8
450 will produce the following output in the link map if the -M
452 option is used:
453 0x00000001 foo = 0x1
455 [0x0000000c] foo = (foo * 0x4)
456 [0x0000000c] foo = (foo + 0x8)
457 See Expressions for more information about expressions in
459 linker scripts.
460 -n
462 --nmagic
463 Turn off page alignment of sections, and disable linking against
464 shared libraries. If the output format supports Unix style magic
465 numbers, mark the output as "NMAGIC".
466 -N
468 --omagic
469 Set the text and data sections to be readable and writable. Also,
470 do not page-align the data segment, and disable linking against
471 shared libraries. If the output format supports Unix style magic
472 numbers, mark the output as "OMAGIC". Note: Although a writable
473 text section is allowed for PE-COFF targets, it does not conform to
474 the format specification published by Microsoft.
475 --no-omagic
477 This option negates most of the effects of the -N option. It sets
478 the text section to be read-only, and forces the data segment to be
479 page-aligned. Note - this option does not enable linking against
480 shared libraries. Use -Bdynamic for this.
481 -o output
483 --output=output
484 Use output as the name for the program produced by ld; if this
485 option is not specified, the name a.out is used by default. The
486 script command "OUTPUT" can also specify the output file name.
487 -O level
489 If level is a numeric values greater than zero ld optimizes the
490 output. This might take significantly longer and therefore
491 probably should only be enabled for the final binary. At the
492 moment this option only affects ELF shared library generation.
493 Future releases of the linker may make more use of this option.
494 Also currently there is no difference in the linker's behaviour for
495 different non-zero values of this option. Again this may change
496 with future releases.
497 -plugin name
499 Involve a plugin in the linking process. The name parameter is the
500 absolute filename of the plugin. Usually this parameter is
501 automatically added by the complier, when using link time
502 optimization, but users can also add their own plugins if they so
503 wish.
504 Note that the location of the compiler originated plugins is
506 different from the place where the ar, nm and ranlib programs
507 search for their plugins. In order for those commands to make use
508 of a compiler based plugin it must first be copied into the
509 ${libdir}/bfd-plugins directory. All gcc based linker plugins are
510 backward compatible, so it is sufficient to just copy in the newest
511 one.
512 --push-state
514 The --push-state allows to preserve the current state of the flags
515 which govern the input file handling so that they can all be
516 restored with one corresponding --pop-state option.
517 The option which are covered are: -Bdynamic, -Bstatic, -dn, -dy,
519 -call_shared, -non_shared, -static, -N, -n, --whole-archive,
520 --no-whole-archive, -r, -Ur, --copy-dt-needed-entries,
521 --no-copy-dt-needed-entries, --as-needed, --no-as-needed, and -a.
522 One target for this option are specifications for pkg-config. When
524 used with the --libs option all possibly needed libraries are
525 listed and then possibly linked with all the time. It is better to
526 return something as follows:
527 -Wl,--push-state,--as-needed -libone -libtwo -Wl,--pop-state
529 --pop-state
531 Undoes the effect of --push-state, restores the previous values of
532 the flags governing input file handling.
533 -q
535 --emit-relocs
536 Leave relocation sections and contents in fully linked executables.
537 Post link analysis and optimization tools may need this information
538 in order to perform correct modifications of executables. This
539 results in larger executables.
540 This option is currently only supported on ELF platforms.
542 --force-dynamic
544 Force the output file to have dynamic sections. This option is
545 specific to VxWorks targets.
546 -r
548 --relocatable
549 Generate relocatable output---i.e., generate an output file that
550 can in turn serve as input to ld. This is often called partial
551 linking. As a side effect, in environments that support standard
552 Unix magic numbers, this option also sets the output file's magic
553 number to "OMAGIC". If this option is not specified, an absolute
554 file is produced. When linking C++ programs, this option will not
555 resolve references to constructors; to do that, use -Ur.
556 When an input file does not have the same format as the output
558 file, partial linking is only supported if that input file does not
559 contain any relocations. Different output formats can have further
560 restrictions; for example some "a.out"-based formats do not support
561 partial linking with input files in other formats at all.
562 This option does the same thing as -i.
564 -R filename
566 --just-symbols=filename
567 Read symbol names and their addresses from filename, but do not
568 relocate it or include it in the output. This allows your output
569 file to refer symbolically to absolute locations of memory defined
570 in other programs. You may use this option more than once.
571 For compatibility with other ELF linkers, if the -R option is
573 followed by a directory name, rather than a file name, it is
574 treated as the -rpath option.
575 -s
577 --strip-all
578 Omit all symbol information from the output file.
579 -S
581 --strip-debug
582 Omit debugger symbol information (but not all symbols) from the
583 output file.
584 --strip-discarded
586 --no-strip-discarded
587 Omit (or do not omit) global symbols defined in discarded sections.
588 Enabled by default.
589 -t
591 --trace
592 Print the names of the input files as ld processes them.
593 -T scriptfile
595 --script=scriptfile
596 Use scriptfile as the linker script. This script replaces ld's
597 default linker script (rather than adding to it), so commandfile
598 must specify everything necessary to describe the output file.
599 If scriptfile does not exist in the current directory, "ld" looks
600 for it in the directories specified by any preceding -L options.
601 Multiple -T options accumulate.
602 -dT scriptfile
604 --default-script=scriptfile
605 Use scriptfile as the default linker script.
606 This option is similar to the --script option except that
608 processing of the script is delayed until after the rest of the
609 command line has been processed. This allows options placed after
610 the --default-script option on the command line to affect the
611 behaviour of the linker script, which can be important when the
612 linker command line cannot be directly controlled by the user. (eg
613 because the command line is being constructed by another tool, such
614 as gcc).
615 -u symbol
617 --undefined=symbol
618 Force symbol to be entered in the output file as an undefined
619 symbol. Doing this may, for example, trigger linking of additional
620 modules from standard libraries. -u may be repeated with different
621 option arguments to enter additional undefined symbols. This
622 option is equivalent to the "EXTERN" linker script command.
623 If this option is being used to force additional modules to be
625 pulled into the link, and if it is an error for the symbol to
626 remain undefined, then the option --require-defined should be used
627 instead.
628 --require-defined=symbol
630 Require that symbol is defined in the output file. This option is
631 the same as option --undefined except that if symbol is not defined
632 in the output file then the linker will issue an error and exit.
633 The same effect can be achieved in a linker script by using
634 "EXTERN", "ASSERT" and "DEFINED" together. This option can be used
635 multiple times to require additional symbols.
636 -Ur For anything other than C++ programs, this option is equivalent to
638 -r: it generates relocatable output---i.e., an output file that can
639 in turn serve as input to ld. When linking C++ programs, -Ur does
640 resolve references to constructors, unlike -r. It does not work to
641 use -Ur on files that were themselves linked with -Ur; once the
642 constructor table has been built, it cannot be added to. Use -Ur
643 only for the last partial link, and -r for the others.
644 --orphan-handling=MODE
646 Control how orphan sections are handled. An orphan section is one
647 not specifically mentioned in a linker script.
648 MODE can have any of the following values:
650 "place"
652 Orphan sections are placed into a suitable output section
653 following the strategy described in Orphan Sections. The
654 option --unique also affects how sections are placed.
655 "discard"
657 All orphan sections are discarded, by placing them in the
658 /DISCARD/ section.
659 "warn"
661 The linker will place the orphan section as for "place" and
662 also issue a warning.
663 "error"
665 The linker will exit with an error if any orphan section is
666 found.
667 The default if --orphan-handling is not given is "place".
669 --unique[=SECTION]
671 Creates a separate output section for every input section matching
672 SECTION, or if the optional wildcard SECTION argument is missing,
673 for every orphan input section. An orphan section is one not
674 specifically mentioned in a linker script. You may use this option
675 multiple times on the command line; It prevents the normal merging
676 of input sections with the same name, overriding output section
677 assignments in a linker script.
678 -v
680 --version
681 -V Display the version number for ld. The -V option also lists the
682 supported emulations.
683 -x
685 --discard-all
686 Delete all local symbols.
687 -X
689 --discard-locals
690 Delete all temporary local symbols. (These symbols start with
691 system-specific local label prefixes, typically .L for ELF systems
692 or L for traditional a.out systems.)
693 -y symbol
695 --trace-symbol=symbol
696 Print the name of each linked file in which symbol appears. This
697 option may be given any number of times. On many systems it is
698 necessary to prepend an underscore.
699 This option is useful when you have an undefined symbol in your
701 link but don't know where the reference is coming from.
702 -Y path
704 Add path to the default library search path. This option exists
705 for Solaris compatibility.
706 -z keyword
708 The recognized keywords are:
709 bndplt
711 Always generate BND prefix in PLT entries. Supported for
712 Linux/x86_64.
713 call-nop=prefix-addr
715 call-nop=suffix-nop
716 call-nop=prefix-byte
717 call-nop=suffix-byte
718 Specify the 1-byte "NOP" padding when transforming indirect
719 call to a locally defined function, foo, via its GOT slot.
720 call-nop=prefix-addr generates "0x67 call foo".
721 call-nop=suffix-nop generates "call foo 0x90".
722 call-nop=prefix-byte generates "byte call foo".
723 call-nop=suffix-byte generates "call foo byte". Supported for
724 i386 and x86_64.
725 combreloc
727 nocombreloc
728 Combine multiple dynamic relocation sections and sort to
729 improve dynamic symbol lookup caching. Do not do this if
730 nocombreloc.
731 common
733 nocommon
734 Generate common symbols with STT_COMMON type during a
735 relocatable link. Use STT_OBJECT type if nocommon.
736 common-page-size=value
738 Set the page size most commonly used to value. Memory image
739 layout will be optimized to minimize memory pages if the system
740 is using pages of this size.
741 defs
743 Report unresolved symbol references from regular object files.
744 This is done even if the linker is creating a non-symbolic
745 shared library. This option is the inverse of -z undefs.
746 dynamic-undefined-weak
748 nodynamic-undefined-weak
749 Make undefined weak symbols dynamic when building a dynamic
750 object, if they are referenced from a regular object file and
751 not forced local by symbol visibility or versioning. Do not
752 make them dynamic if nodynamic-undefined-weak. If neither
753 option is given, a target may default to either option being in
754 force, or make some other selection of undefined weak symbols
755 dynamic. Not all targets support these options.
756 execstack
758 Marks the object as requiring executable stack.
759 global
761 This option is only meaningful when building a shared object.
762 It makes the symbols defined by this shared object available
763 for symbol resolution of subsequently loaded libraries.
764 globalaudit
766 This option is only meaningful when building a dynamic
767 executable. This option marks the executable as requiring
768 global auditing by setting the "DF_1_GLOBAUDIT" bit in the
769 "DT_FLAGS_1" dynamic tag. Global auditing requires that any
770 auditing library defined via the --depaudit or -P command line
771 options be run for all dynamic objects loaded by the
772 application.
773 ibtplt
775 Generate Intel Indirect Branch Tracking (IBT) enabled PLT
776 entries. Supported for Linux/i386 and Linux/x86_64.
777 ibt Generate GNU_PROPERTY_X86_FEATURE_1_IBT in .note.gnu.property
779 section to indicate compatibility with IBT. This also implies
780 ibtplt. Supported for Linux/i386 and Linux/x86_64.
781 initfirst
783 This option is only meaningful when building a shared object.
784 It marks the object so that its runtime initialization will
785 occur before the runtime initialization of any other objects
786 brought into the process at the same time. Similarly the
787 runtime finalization of the object will occur after the runtime
788 finalization of any other objects.
789 interpose
791 Specify that the dynamic loader should modify its symbol search
792 order so that symbols in this shared library interpose all
793 other shared libraries not so marked.
794 lazy
796 When generating an executable or shared library, mark it to
797 tell the dynamic linker to defer function call resolution to
798 the point when the function is called (lazy binding), rather
799 than at load time. Lazy binding is the default.
800 loadfltr
802 Specify that the object's filters be processed immediately at
803 runtime.
804 max-page-size=value
806 Set the maximum memory page size supported to value.
807 muldefs
809 Allow multiple definitions.
810 nocopyreloc
812 Disable linker generated .dynbss variables used in place of
813 variables defined in shared libraries. May result in dynamic
814 text relocations.
815 nodefaultlib
817 Specify that the dynamic loader search for dependencies of this
818 object should ignore any default library search paths.
819 nodelete
821 Specify that the object shouldn't be unloaded at runtime.
822 nodlopen
824 Specify that the object is not available to "dlopen".
825 nodump
827 Specify that the object can not be dumped by "dldump".
828 noexecstack
830 Marks the object as not requiring executable stack.
831 noextern-protected-data
833 Don't treat protected data symbols as external when building a
834 shared library. This option overrides the linker backend
835 default. It can be used to work around incorrect relocations
836 against protected data symbols generated by compiler. Updates
837 on protected data symbols by another module aren't visible to
838 the resulting shared library. Supported for i386 and x86-64.
839 noreloc-overflow
841 Disable relocation overflow check. This can be used to disable
842 relocation overflow check if there will be no dynamic
843 relocation overflow at run-time. Supported for x86_64.
844 now When generating an executable or shared library, mark it to
846 tell the dynamic linker to resolve all symbols when the program
847 is started, or when the shared library is loaded by dlopen,
848 instead of deferring function call resolution to the point when
849 the function is first called.
850 origin
852 Specify that the object requires $ORIGIN handling in paths.
853 relro
855 norelro
856 Create an ELF "PT_GNU_RELRO" segment header in the object.
857 This specifies a memory segment that should be made read-only
858 after relocation, if supported. Specifying common-page-size
859 smaller than the system page size will render this protection
860 ineffective. Don't create an ELF "PT_GNU_RELRO" segment if
861 norelro.
862 separate-code
864 noseparate-code
865 Create separate code "PT_LOAD" segment header in the object.
866 This specifies a memory segment that should contain only
867 instructions and must be in wholly disjoint pages from any
868 other data. Don't create separate code "PT_LOAD" segment if
869 noseparate-code is used.
870 shstk
872 Generate GNU_PROPERTY_X86_FEATURE_1_SHSTK in .note.gnu.property
873 section to indicate compatibility with Intel Shadow Stack.
874 Supported for Linux/i386 and Linux/x86_64.
875 stack-size=value
877 Specify a stack size for an ELF "PT_GNU_STACK" segment.
878 Specifying zero will override any default non-zero sized
879 "PT_GNU_STACK" segment creation.
880 text
882 notext
883 textoff
884 Report an error if DT_TEXTREL is set, i.e., if the binary has
885 dynamic relocations in read-only sections. Don't report an
886 error if notext or textoff.
887 undefs
889 Do not report unresolved symbol references from regular object
890 files, either when creating an executable, or when creating a
891 shared library. This option is the inverse of -z defs.
892 Other keywords are ignored for Solaris compatibility.
894 -( archives -)
896 --start-group archives --end-group
897 The archives should be a list of archive files. They may be either
898 explicit file names, or -l options.
899 The specified archives are searched repeatedly until no new
901 undefined references are created. Normally, an archive is searched
902 only once in the order that it is specified on the command line.
903 If a symbol in that archive is needed to resolve an undefined
904 symbol referred to by an object in an archive that appears later on
905 the command line, the linker would not be able to resolve that
906 reference. By grouping the archives, they all be searched
907 repeatedly until all possible references are resolved.
908 Using this option has a significant performance cost. It is best
910 to use it only when there are unavoidable circular references
911 between two or more archives.
912 --accept-unknown-input-arch
914 --no-accept-unknown-input-arch
915 Tells the linker to accept input files whose architecture cannot be
916 recognised. The assumption is that the user knows what they are
917 doing and deliberately wants to link in these unknown input files.
918 This was the default behaviour of the linker, before release 2.14.
919 The default behaviour from release 2.14 onwards is to reject such
920 input files, and so the --accept-unknown-input-arch option has been
921 added to restore the old behaviour.
922 --as-needed
924 --no-as-needed
925 This option affects ELF DT_NEEDED tags for dynamic libraries
926 mentioned on the command line after the --as-needed option.
927 Normally the linker will add a DT_NEEDED tag for each dynamic
928 library mentioned on the command line, regardless of whether the
929 library is actually needed or not. --as-needed causes a DT_NEEDED
930 tag to only be emitted for a library that at that point in the link
931 satisfies a non-weak undefined symbol reference from a regular
932 object file or, if the library is not found in the DT_NEEDED lists
933 of other needed libraries, a non-weak undefined symbol reference
934 from another needed dynamic library. Object files or libraries
935 appearing on the command line after the library in question do not
936 affect whether the library is seen as needed. This is similar to
937 the rules for extraction of object files from archives.
938 --no-as-needed restores the default behaviour.
939 --add-needed
941 --no-add-needed
942 These two options have been deprecated because of the similarity of
943 their names to the --as-needed and --no-as-needed options. They
944 have been replaced by --copy-dt-needed-entries and
945 --no-copy-dt-needed-entries.
946 -assert keyword
948 This option is ignored for SunOS compatibility.
949 -Bdynamic
951 -dy
952 -call_shared
953 Link against dynamic libraries. This is only meaningful on
954 platforms for which shared libraries are supported. This option is
955 normally the default on such platforms. The different variants of
956 this option are for compatibility with various systems. You may
957 use this option multiple times on the command line: it affects
958 library searching for -l options which follow it.
959 -Bgroup
961 Set the "DF_1_GROUP" flag in the "DT_FLAGS_1" entry in the dynamic
962 section. This causes the runtime linker to handle lookups in this
963 object and its dependencies to be performed only inside the group.
964 --unresolved-symbols=report-all is implied. This option is only
965 meaningful on ELF platforms which support shared libraries.
966 -Bstatic
968 -dn
969 -non_shared
970 -static
971 Do not link against shared libraries. This is only meaningful on
972 platforms for which shared libraries are supported. The different
973 variants of this option are for compatibility with various systems.
974 You may use this option multiple times on the command line: it
975 affects library searching for -l options which follow it. This
976 option also implies --unresolved-symbols=report-all. This option
977 can be used with -shared. Doing so means that a shared library is
978 being created but that all of the library's external references
979 must be resolved by pulling in entries from static libraries.
980 -Bsymbolic
982 When creating a shared library, bind references to global symbols
983 to the definition within the shared library, if any. Normally, it
984 is possible for a program linked against a shared library to
985 override the definition within the shared library. This option can
986 also be used with the --export-dynamic option, when creating a
987 position independent executable, to bind references to global
988 symbols to the definition within the executable. This option is
989 only meaningful on ELF platforms which support shared libraries and
990 position independent executables.
991 -Bsymbolic-functions
993 When creating a shared library, bind references to global function
994 symbols to the definition within the shared library, if any. This
995 option can also be used with the --export-dynamic option, when
996 creating a position independent executable, to bind references to
997 global function symbols to the definition within the executable.
998 This option is only meaningful on ELF platforms which support
999 shared libraries and position independent executables.
1000 --dynamic-list=dynamic-list-file
1002 Specify the name of a dynamic list file to the linker. This is
1003 typically used when creating shared libraries to specify a list of
1004 global symbols whose references shouldn't be bound to the
1005 definition within the shared library, or creating dynamically
1006 linked executables to specify a list of symbols which should be
1007 added to the symbol table in the executable. This option is only
1008 meaningful on ELF platforms which support shared libraries.
1009 The format of the dynamic list is the same as the version node
1011 without scope and node name. See VERSION for more information.
1012 --dynamic-list-data
1014 Include all global data symbols to the dynamic list.
1015 --dynamic-list-cpp-new
1017 Provide the builtin dynamic list for C++ operator new and delete.
1018 It is mainly useful for building shared libstdc++.
1019 --dynamic-list-cpp-typeinfo
1021 Provide the builtin dynamic list for C++ runtime type
1022 identification.
1023 --check-sections
1025 --no-check-sections
1026 Asks the linker not to check section addresses after they have been
1027 assigned to see if there are any overlaps. Normally the linker
1028 will perform this check, and if it finds any overlaps it will
1029 produce suitable error messages. The linker does know about, and
1030 does make allowances for sections in overlays. The default
1031 behaviour can be restored by using the command line switch
1032 --check-sections. Section overlap is not usually checked for
1033 relocatable links. You can force checking in that case by using
1034 the --check-sections option.
1035 --copy-dt-needed-entries
1037 --no-copy-dt-needed-entries
1038 This option affects the treatment of dynamic libraries referred to
1039 by DT_NEEDED tags inside ELF dynamic libraries mentioned on the
1040 command line. Normally the linker won't add a DT_NEEDED tag to the
1041 output binary for each library mentioned in a DT_NEEDED tag in an
1042 input dynamic library. With --copy-dt-needed-entries specified on
1043 the command line however any dynamic libraries that follow it will
1044 have their DT_NEEDED entries added. The default behaviour can be
1045 restored with --no-copy-dt-needed-entries.
1046 This option also has an effect on the resolution of symbols in
1048 dynamic libraries. With --copy-dt-needed-entries dynamic libraries
1049 mentioned on the command line will be recursively searched,
1050 following their DT_NEEDED tags to other libraries, in order to
1051 resolve symbols required by the output binary. With the default
1052 setting however the searching of dynamic libraries that follow it
1053 will stop with the dynamic library itself. No DT_NEEDED links will
1054 be traversed to resolve symbols.
1055 --cref
1057 Output a cross reference table. If a linker map file is being
1058 generated, the cross reference table is printed to the map file.
1059 Otherwise, it is printed on the standard output.
1060 The format of the table is intentionally simple, so that it may be
1062 easily processed by a script if necessary. The symbols are printed
1063 out, sorted by name. For each symbol, a list of file names is
1064 given. If the symbol is defined, the first file listed is the
1065 location of the definition. If the symbol is defined as a common
1066 value then any files where this happens appear next. Finally any
1067 files that reference the symbol are listed.
1068 --no-define-common
1070 This option inhibits the assignment of addresses to common symbols.
1071 The script command "INHIBIT_COMMON_ALLOCATION" has the same effect.
1072 The --no-define-common option allows decoupling the decision to
1074 assign addresses to Common symbols from the choice of the output
1075 file type; otherwise a non-Relocatable output type forces assigning
1076 addresses to Common symbols. Using --no-define-common allows
1077 Common symbols that are referenced from a shared library to be
1078 assigned addresses only in the main program. This eliminates the
1079 unused duplicate space in the shared library, and also prevents any
1080 possible confusion over resolving to the wrong duplicate when there
1081 are many dynamic modules with specialized search paths for runtime
1082 symbol resolution.
1083 --force-group-allocation
1085 This option causes the linker to place section group members like
1086 normal input sections, and to delete the section groups. This is
1087 the default behaviour for a final link but this option can be used
1088 to change the behaviour of a relocatable link (-r). The script
1089 command "FORCE_GROUP_ALLOCATION" has the same effect.
1090 --defsym=symbol=expression
1092 Create a global symbol in the output file, containing the absolute
1093 address given by expression. You may use this option as many times
1094 as necessary to define multiple symbols in the command line. A
1095 limited form of arithmetic is supported for the expression in this
1096 context: you may give a hexadecimal constant or the name of an
1097 existing symbol, or use "+" and "-" to add or subtract hexadecimal
1098 constants or symbols. If you need more elaborate expressions,
1099 consider using the linker command language from a script. Note:
1100 there should be no white space between symbol, the equals sign
1101 ("="), and expression.
1102 --demangle[=style]
1104 --no-demangle
1105 These options control whether to demangle symbol names in error
1106 messages and other output. When the linker is told to demangle, it
1107 tries to present symbol names in a readable fashion: it strips
1108 leading underscores if they are used by the object file format, and
1109 converts C++ mangled symbol names into user readable names.
1110 Different compilers have different mangling styles. The optional
1111 demangling style argument can be used to choose an appropriate
1112 demangling style for your compiler. The linker will demangle by
1113 default unless the environment variable COLLECT_NO_DEMANGLE is set.
1114 These options may be used to override the default.
1115 -Ifile
1117 --dynamic-linker=file
1118 Set the name of the dynamic linker. This is only meaningful when
1119 generating dynamically linked ELF executables. The default dynamic
1120 linker is normally correct; don't use this unless you know what you
1121 are doing.
1122 --no-dynamic-linker
1124 When producing an executable file, omit the request for a dynamic
1125 linker to be used at load-time. This is only meaningful for ELF
1126 executables that contain dynamic relocations, and usually requires
1127 entry point code that is capable of processing these relocations.
1128 --embedded-relocs
1130 This option is similar to the --emit-relocs option except that the
1131 relocs are stored in a target specific section. This option is
1132 only supported by the BFIN, CR16 and M68K targets.
1133 --fatal-warnings
1135 --no-fatal-warnings
1136 Treat all warnings as errors. The default behaviour can be
1137 restored with the option --no-fatal-warnings.
1138 --force-exe-suffix
1140 Make sure that an output file has a .exe suffix.
1141 If a successfully built fully linked output file does not have a
1143 ".exe" or ".dll" suffix, this option forces the linker to copy the
1144 output file to one of the same name with a ".exe" suffix. This
1145 option is useful when using unmodified Unix makefiles on a
1146 Microsoft Windows host, since some versions of Windows won't run an
1147 image unless it ends in a ".exe" suffix.
1148 --gc-sections
1150 --no-gc-sections
1151 Enable garbage collection of unused input sections. It is ignored
1152 on targets that do not support this option. The default behaviour
1153 (of not performing this garbage collection) can be restored by
1154 specifying --no-gc-sections on the command line. Note that garbage
1155 collection for COFF and PE format targets is supported, but the
1156 implementation is currently considered to be experimental.
1157 --gc-sections decides which input sections are used by examining
1159 symbols and relocations. The section containing the entry symbol
1160 and all sections containing symbols undefined on the command-line
1161 will be kept, as will sections containing symbols referenced by
1162 dynamic objects. Note that when building shared libraries, the
1163 linker must assume that any visible symbol is referenced. Once
1164 this initial set of sections has been determined, the linker
1165 recursively marks as used any section referenced by their
1166 relocations. See --entry and --undefined.
1167 This option can be set when doing a partial link (enabled with
1169 option -r). In this case the root of symbols kept must be
1170 explicitly specified either by an --entry or --undefined option or
1171 by a "ENTRY" command in the linker script.
1172 --print-gc-sections
1174 --no-print-gc-sections
1175 List all sections removed by garbage collection. The listing is
1176 printed on stderr. This option is only effective if garbage
1177 collection has been enabled via the --gc-sections) option. The
1178 default behaviour (of not listing the sections that are removed)
1179 can be restored by specifying --no-print-gc-sections on the command
1180 line.
1181 --gc-keep-exported
1183 When --gc-sections is enabled, this option prevents garbage
1184 collection of unused input sections that contain global symbols
1185 having default or protected visibility. This option is intended to
1186 be used for executables where unreferenced sections would otherwise
1187 be garbage collected regardless of the external visibility of
1188 contained symbols. Note that this option has no effect when
1189 linking shared objects since it is already the default behaviour.
1190 This option is only supported for ELF format targets.
1191 --print-output-format
1193 Print the name of the default output format (perhaps influenced by
1194 other command-line options). This is the string that would appear
1195 in an "OUTPUT_FORMAT" linker script command.
1196 --print-memory-usage
1198 Print used size, total size and used size of memory regions created
1199 with the MEMORY command. This is useful on embedded targets to
1200 have a quick view of amount of free memory. The format of the
1201 output has one headline and one line per region. It is both human
1202 readable and easily parsable by tools. Here is an example of an
1203 output:
1204 Memory region Used Size Region Size %age Used
1206 ROM: 256 KB 1 MB 25.00%
1207 RAM: 32 B 2 GB 0.00%
1208 --help
1210 Print a summary of the command-line options on the standard output
1211 and exit.
1212 --target-help
1214 Print a summary of all target specific options on the standard
1215 output and exit.
1216 -Map=mapfile
1218 Print a link map to the file mapfile. See the description of the
1219 -M option, above.
1220 --no-keep-memory
1222 ld normally optimizes for speed over memory usage by caching the
1223 symbol tables of input files in memory. This option tells ld to
1224 instead optimize for memory usage, by rereading the symbol tables
1225 as necessary. This may be required if ld runs out of memory space
1226 while linking a large executable.
1227 --no-undefined
1229 -z defs
1230 Report unresolved symbol references from regular object files.
1231 This is done even if the linker is creating a non-symbolic shared
1232 library. The switch --[no-]allow-shlib-undefined controls the
1233 behaviour for reporting unresolved references found in shared
1234 libraries being linked in.
1235 The effects of this option can be reverted by using "-z undefs".
1237 --allow-multiple-definition
1239 -z muldefs
1240 Normally when a symbol is defined multiple times, the linker will
1241 report a fatal error. These options allow multiple definitions and
1242 the first definition will be used.
1243 --allow-shlib-undefined
1245 --no-allow-shlib-undefined
1246 Allows or disallows undefined symbols in shared libraries. This
1247 switch is similar to --no-undefined except that it determines the
1248 behaviour when the undefined symbols are in a shared library rather
1249 than a regular object file. It does not affect how undefined
1250 symbols in regular object files are handled.
1251 The default behaviour is to report errors for any undefined symbols
1253 referenced in shared libraries if the linker is being used to
1254 create an executable, but to allow them if the linker is being used
1255 to create a shared library.
1256 The reasons for allowing undefined symbol references in shared
1258 libraries specified at link time are that:
1259 · A shared library specified at link time may not be the same as
1261 the one that is available at load time, so the symbol might
1262 actually be resolvable at load time.
1263 · There are some operating systems, eg BeOS and HPPA, where
1265 undefined symbols in shared libraries are normal.
1266 The BeOS kernel for example patches shared libraries at load
1268 time to select whichever function is most appropriate for the
1269 current architecture. This is used, for example, to
1270 dynamically select an appropriate memset function.
1271 --no-undefined-version
1273 Normally when a symbol has an undefined version, the linker will
1274 ignore it. This option disallows symbols with undefined version and
1275 a fatal error will be issued instead.
1276 --default-symver
1278 Create and use a default symbol version (the soname) for
1279 unversioned exported symbols.
1280 --default-imported-symver
1282 Create and use a default symbol version (the soname) for
1283 unversioned imported symbols.
1284 --no-warn-mismatch
1286 Normally ld will give an error if you try to link together input
1287 files that are mismatched for some reason, perhaps because they
1288 have been compiled for different processors or for different
1289 endiannesses. This option tells ld that it should silently permit
1290 such possible errors. This option should only be used with care,
1291 in cases when you have taken some special action that ensures that
1292 the linker errors are inappropriate.
1293 --no-warn-search-mismatch
1295 Normally ld will give a warning if it finds an incompatible library
1296 during a library search. This option silences the warning.
1297 --no-whole-archive
1299 Turn off the effect of the --whole-archive option for subsequent
1300 archive files.
1301 --noinhibit-exec
1303 Retain the executable output file whenever it is still usable.
1304 Normally, the linker will not produce an output file if it
1305 encounters errors during the link process; it exits without writing
1306 an output file when it issues any error whatsoever.
1307 -nostdlib
1309 Only search library directories explicitly specified on the command
1310 line. Library directories specified in linker scripts (including
1311 linker scripts specified on the command line) are ignored.
1312 --oformat=output-format
1314 ld may be configured to support more than one kind of object file.
1315 If your ld is configured this way, you can use the --oformat option
1316 to specify the binary format for the output object file. Even when
1317 ld is configured to support alternative object formats, you don't
1318 usually need to specify this, as ld should be configured to produce
1319 as a default output format the most usual format on each machine.
1320 output-format is a text string, the name of a particular format
1321 supported by the BFD libraries. (You can list the available binary
1322 formats with objdump -i.) The script command "OUTPUT_FORMAT" can
1323 also specify the output format, but this option overrides it.
1324 --out-implib file
1326 Create an import library in file corresponding to the executable
1327 the linker is generating (eg. a DLL or ELF program). This import
1328 library (which should be called "*.dll.a" or "*.a" for DLLs) may be
1329 used to link clients against the generated executable; this
1330 behaviour makes it possible to skip a separate import library
1331 creation step (eg. "dlltool" for DLLs). This option is only
1332 available for the i386 PE and ELF targetted ports of the linker.
1333 -pie
1335 --pic-executable
1336 Create a position independent executable. This is currently only
1337 supported on ELF platforms. Position independent executables are
1338 similar to shared libraries in that they are relocated by the
1339 dynamic linker to the virtual address the OS chooses for them
1340 (which can vary between invocations). Like normal dynamically
1341 linked executables they can be executed and symbols defined in the
1342 executable cannot be overridden by shared libraries.
1343 -qmagic
1345 This option is ignored for Linux compatibility.
1346 -Qy This option is ignored for SVR4 compatibility.
1348 --relax
1350 --no-relax
1351 An option with machine dependent effects. This option is only
1352 supported on a few targets.
1353 On some platforms the --relax option performs target specific,
1355 global optimizations that become possible when the linker resolves
1356 addressing in the program, such as relaxing address modes,
1357 synthesizing new instructions, selecting shorter version of current
1358 instructions, and combining constant values.
1359 On some platforms these link time global optimizations may make
1361 symbolic debugging of the resulting executable impossible. This is
1362 known to be the case for the Matsushita MN10200 and MN10300 family
1363 of processors.
1364 On platforms where this is not supported, --relax is accepted, but
1366 ignored.
1367 On platforms where --relax is accepted the option --no-relax can be
1369 used to disable the feature.
1370 --retain-symbols-file=filename
1372 Retain only the symbols listed in the file filename, discarding all
1373 others. filename is simply a flat file, with one symbol name per
1374 line. This option is especially useful in environments (such as
1375 VxWorks) where a large global symbol table is accumulated
1376 gradually, to conserve run-time memory.
1377 --retain-symbols-file does not discard undefined symbols, or
1379 symbols needed for relocations.
1380 You may only specify --retain-symbols-file once in the command
1382 line. It overrides -s and -S.
1383 -rpath=dir
1385 Add a directory to the runtime library search path. This is used
1386 when linking an ELF executable with shared objects. All -rpath
1387 arguments are concatenated and passed to the runtime linker, which
1388 uses them to locate shared objects at runtime. The -rpath option
1389 is also used when locating shared objects which are needed by
1390 shared objects explicitly included in the link; see the description
1391 of the -rpath-link option. If -rpath is not used when linking an
1392 ELF executable, the contents of the environment variable
1393 "LD_RUN_PATH" will be used if it is defined.
1394 The -rpath option may also be used on SunOS. By default, on SunOS,
1396 the linker will form a runtime search path out of all the -L
1397 options it is given. If a -rpath option is used, the runtime
1398 search path will be formed exclusively using the -rpath options,
1399 ignoring the -L options. This can be useful when using gcc, which
1400 adds many -L options which may be on NFS mounted file systems.
1401 For compatibility with other ELF linkers, if the -R option is
1403 followed by a directory name, rather than a file name, it is
1404 treated as the -rpath option.
1405 -rpath-link=dir
1407 When using ELF or SunOS, one shared library may require another.
1408 This happens when an "ld -shared" link includes a shared library as
1409 one of the input files.
1410 When the linker encounters such a dependency when doing a non-
1412 shared, non-relocatable link, it will automatically try to locate
1413 the required shared library and include it in the link, if it is
1414 not included explicitly. In such a case, the -rpath-link option
1415 specifies the first set of directories to search. The -rpath-link
1416 option may specify a sequence of directory names either by
1417 specifying a list of names separated by colons, or by appearing
1418 multiple times.
1419 The tokens $ORIGIN and $LIB can appear in these search directories.
1421 They will be replaced by the full path to the directory containing
1422 the program or shared object in the case of $ORIGIN and either lib
1423 - for 32-bit binaries - or lib64 - for 64-bit binaries - in the
1424 case of $LIB.
1425 The alternative form of these tokens - ${ORIGIN} and ${LIB} can
1427 also be used. The token $PLATFORM is not supported.
1428 This option should be used with caution as it overrides the search
1430 path that may have been hard compiled into a shared library. In
1431 such a case it is possible to use unintentionally a different
1432 search path than the runtime linker would do.
1433 The linker uses the following search paths to locate required
1435 shared libraries:
1436 1. Any directories specified by -rpath-link options.
1438 2. Any directories specified by -rpath options. The difference
1440 between -rpath and -rpath-link is that directories specified by
1441 -rpath options are included in the executable and used at
1442 runtime, whereas the -rpath-link option is only effective at
1443 link time. Searching -rpath in this way is only supported by
1444 native linkers and cross linkers which have been configured
1445 with the --with-sysroot option.
1446 3. On an ELF system, for native linkers, if the -rpath and
1448 -rpath-link options were not used, search the contents of the
1449 environment variable "LD_RUN_PATH".
1450 4. On SunOS, if the -rpath option was not used, search any
1452 directories specified using -L options.
1453 5. For a native linker, search the contents of the environment
1455 variable "LD_LIBRARY_PATH".
1456 6. For a native ELF linker, the directories in "DT_RUNPATH" or
1458 "DT_RPATH" of a shared library are searched for shared
1459 libraries needed by it. The "DT_RPATH" entries are ignored if
1460 "DT_RUNPATH" entries exist.
1461 7. The default directories, normally /lib and /usr/lib.
1463 8. For a native linker on an ELF system, if the file
1465 /etc/ld.so.conf exists, the list of directories found in that
1466 file.
1467 If the required shared library is not found, the linker will issue
1469 a warning and continue with the link.
1470 -shared
1472 -Bshareable
1473 Create a shared library. This is currently only supported on ELF,
1474 XCOFF and SunOS platforms. On SunOS, the linker will automatically
1475 create a shared library if the -e option is not used and there are
1476 undefined symbols in the link.
1477 --sort-common
1479 --sort-common=ascending
1480 --sort-common=descending
1481 This option tells ld to sort the common symbols by alignment in
1482 ascending or descending order when it places them in the
1483 appropriate output sections. The symbol alignments considered are
1484 sixteen-byte or larger, eight-byte, four-byte, two-byte, and one-
1485 byte. This is to prevent gaps between symbols due to alignment
1486 constraints. If no sorting order is specified, then descending
1487 order is assumed.
1488 --sort-section=name
1490 This option will apply "SORT_BY_NAME" to all wildcard section
1491 patterns in the linker script.
1492 --sort-section=alignment
1494 This option will apply "SORT_BY_ALIGNMENT" to all wildcard section
1495 patterns in the linker script.
1496 --spare-dynamic-tags=count
1498 This option specifies the number of empty slots to leave in the
1499 .dynamic section of ELF shared objects. Empty slots may be needed
1500 by post processing tools, such as the prelinker. The default is 5.
1501 --split-by-file[=size]
1503 Similar to --split-by-reloc but creates a new output section for
1504 each input file when size is reached. size defaults to a size of 1
1505 if not given.
1506 --split-by-reloc[=count]
1508 Tries to creates extra sections in the output file so that no
1509 single output section in the file contains more than count
1510 relocations. This is useful when generating huge relocatable files
1511 for downloading into certain real time kernels with the COFF object
1512 file format; since COFF cannot represent more than 65535
1513 relocations in a single section. Note that this will fail to work
1514 with object file formats which do not support arbitrary sections.
1515 The linker will not split up individual input sections for
1516 redistribution, so if a single input section contains more than
1517 count relocations one output section will contain that many
1518 relocations. count defaults to a value of 32768.
1519 --stats
1521 Compute and display statistics about the operation of the linker,
1522 such as execution time and memory usage.
1523 --sysroot=directory
1525 Use directory as the location of the sysroot, overriding the
1526 configure-time default. This option is only supported by linkers
1527 that were configured using --with-sysroot.
1528 --task-link
1530 This is used by COFF/PE based targets to create a task-linked
1531 object file where all of the global symbols have been converted to
1532 statics.
1533 --traditional-format
1535 For some targets, the output of ld is different in some ways from
1536 the output of some existing linker. This switch requests ld to use
1537 the traditional format instead.
1538 For example, on SunOS, ld combines duplicate entries in the symbol
1540 string table. This can reduce the size of an output file with full
1541 debugging information by over 30 percent. Unfortunately, the SunOS
1542 "dbx" program can not read the resulting program ("gdb" has no
1543 trouble). The --traditional-format switch tells ld to not combine
1544 duplicate entries.
1545 --section-start=sectionname=org
1547 Locate a section in the output file at the absolute address given
1548 by org. You may use this option as many times as necessary to
1549 locate multiple sections in the command line. org must be a single
1550 hexadecimal integer; for compatibility with other linkers, you may
1551 omit the leading 0x usually associated with hexadecimal values.
1552 Note: there should be no white space between sectionname, the
1553 equals sign ("="), and org.
1554 -Tbss=org
1556 -Tdata=org
1557 -Ttext=org
1558 Same as --section-start, with ".bss", ".data" or ".text" as the
1559 sectionname.
1560 -Ttext-segment=org
1562 When creating an ELF executable, it will set the address of the
1563 first byte of the text segment.
1564 -Trodata-segment=org
1566 When creating an ELF executable or shared object for a target where
1567 the read-only data is in its own segment separate from the
1568 executable text, it will set the address of the first byte of the
1569 read-only data segment.
1570 -Tldata-segment=org
1572 When creating an ELF executable or shared object for x86-64 medium
1573 memory model, it will set the address of the first byte of the
1574 ldata segment.
1575 --unresolved-symbols=method
1577 Determine how to handle unresolved symbols. There are four
1578 possible values for method:
1579 ignore-all
1581 Do not report any unresolved symbols.
1582 report-all
1584 Report all unresolved symbols. This is the default.
1585 ignore-in-object-files
1587 Report unresolved symbols that are contained in shared
1588 libraries, but ignore them if they come from regular object
1589 files.
1590 ignore-in-shared-libs
1592 Report unresolved symbols that come from regular object files,
1593 but ignore them if they come from shared libraries. This can
1594 be useful when creating a dynamic binary and it is known that
1595 all the shared libraries that it should be referencing are
1596 included on the linker's command line.
1597 The behaviour for shared libraries on their own can also be
1599 controlled by the --[no-]allow-shlib-undefined option.
1600 Normally the linker will generate an error message for each
1602 reported unresolved symbol but the option --warn-unresolved-symbols
1603 can change this to a warning.
1604 --dll-verbose
1606 --verbose[=NUMBER]
1607 Display the version number for ld and list the linker emulations
1608 supported. Display which input files can and cannot be opened.
1609 Display the linker script being used by the linker. If the optional
1610 NUMBER argument > 1, plugin symbol status will also be displayed.
1611 --version-script=version-scriptfile
1613 Specify the name of a version script to the linker. This is
1614 typically used when creating shared libraries to specify additional
1615 information about the version hierarchy for the library being
1616 created. This option is only fully supported on ELF platforms
1617 which support shared libraries; see VERSION. It is partially
1618 supported on PE platforms, which can use version scripts to filter
1619 symbol visibility in auto-export mode: any symbols marked local in
1620 the version script will not be exported.
1621 --warn-common
1623 Warn when a common symbol is combined with another common symbol or
1624 with a symbol definition. Unix linkers allow this somewhat sloppy
1625 practice, but linkers on some other operating systems do not. This
1626 option allows you to find potential problems from combining global
1627 symbols. Unfortunately, some C libraries use this practice, so you
1628 may get some warnings about symbols in the libraries as well as in
1629 your programs.
1630 There are three kinds of global symbols, illustrated here by C
1632 examples:
1633 int i = 1;
1635 A definition, which goes in the initialized data section of the
1636 output file.
1637 extern int i;
1639 An undefined reference, which does not allocate space. There
1640 must be either a definition or a common symbol for the variable
1641 somewhere.
1642 int i;
1644 A common symbol. If there are only (one or more) common
1645 symbols for a variable, it goes in the uninitialized data area
1646 of the output file. The linker merges multiple common symbols
1647 for the same variable into a single symbol. If they are of
1648 different sizes, it picks the largest size. The linker turns a
1649 common symbol into a declaration, if there is a definition of
1650 the same variable.
1651 The --warn-common option can produce five kinds of warnings. Each
1653 warning consists of a pair of lines: the first describes the symbol
1654 just encountered, and the second describes the previous symbol
1655 encountered with the same name. One or both of the two symbols
1656 will be a common symbol.
1657 1. Turning a common symbol into a reference, because there is
1659 already a definition for the symbol.
1660 <file>(<section>): warning: common of `<symbol>'
1662 overridden by definition
1663 <file>(<section>): warning: defined here
1664 2. Turning a common symbol into a reference, because a later
1666 definition for the symbol is encountered. This is the same as
1667 the previous case, except that the symbols are encountered in a
1668 different order.
1669 <file>(<section>): warning: definition of `<symbol>'
1671 overriding common
1672 <file>(<section>): warning: common is here
1673 3. Merging a common symbol with a previous same-sized common
1675 symbol.
1676 <file>(<section>): warning: multiple common
1678 of `<symbol>'
1679 <file>(<section>): warning: previous common is here
1680 4. Merging a common symbol with a previous larger common symbol.
1682 <file>(<section>): warning: common of `<symbol>'
1684 overridden by larger common
1685 <file>(<section>): warning: larger common is here
1686 5. Merging a common symbol with a previous smaller common symbol.
1688 This is the same as the previous case, except that the symbols
1689 are encountered in a different order.
1690 <file>(<section>): warning: common of `<symbol>'
1692 overriding smaller common
1693 <file>(<section>): warning: smaller common is here
1694 --warn-constructors
1696 Warn if any global constructors are used. This is only useful for
1697 a few object file formats. For formats like COFF or ELF, the
1698 linker can not detect the use of global constructors.
1699 --warn-multiple-gp
1701 Warn if multiple global pointer values are required in the output
1702 file. This is only meaningful for certain processors, such as the
1703 Alpha. Specifically, some processors put large-valued constants in
1704 a special section. A special register (the global pointer) points
1705 into the middle of this section, so that constants can be loaded
1706 efficiently via a base-register relative addressing mode. Since
1707 the offset in base-register relative mode is fixed and relatively
1708 small (e.g., 16 bits), this limits the maximum size of the constant
1709 pool. Thus, in large programs, it is often necessary to use
1710 multiple global pointer values in order to be able to address all
1711 possible constants. This option causes a warning to be issued
1712 whenever this case occurs.
1713 --warn-once
1715 Only warn once for each undefined symbol, rather than once per
1716 module which refers to it.
1717 --warn-section-align
1719 Warn if the address of an output section is changed because of
1720 alignment. Typically, the alignment will be set by an input
1721 section. The address will only be changed if it not explicitly
1722 specified; that is, if the "SECTIONS" command does not specify a
1723 start address for the section.
1724 --warn-shared-textrel
1726 Warn if the linker adds a DT_TEXTREL to a shared object.
1727 --warn-alternate-em
1729 Warn if an object has alternate ELF machine code.
1730 --warn-unresolved-symbols
1732 If the linker is going to report an unresolved symbol (see the
1733 option --unresolved-symbols) it will normally generate an error.
1734 This option makes it generate a warning instead.
1735 --error-unresolved-symbols
1737 This restores the linker's default behaviour of generating errors
1738 when it is reporting unresolved symbols.
1739 --whole-archive
1741 For each archive mentioned on the command line after the
1742 --whole-archive option, include every object file in the archive in
1743 the link, rather than searching the archive for the required object
1744 files. This is normally used to turn an archive file into a shared
1745 library, forcing every object to be included in the resulting
1746 shared library. This option may be used more than once.
1747 Two notes when using this option from gcc: First, gcc doesn't know
1749 about this option, so you have to use -Wl,-whole-archive. Second,
1750 don't forget to use -Wl,-no-whole-archive after your list of
1751 archives, because gcc will add its own list of archives to your
1752 link and you may not want this flag to affect those as well.
1753 --wrap=symbol
1755 Use a wrapper function for symbol. Any undefined reference to
1756 symbol will be resolved to "__wrap_symbol". Any undefined
1757 reference to "__real_symbol" will be resolved to symbol.
1758 This can be used to provide a wrapper for a system function. The
1760 wrapper function should be called "__wrap_symbol". If it wishes to
1761 call the system function, it should call "__real_symbol".
1762 Here is a trivial example:
1764 void *
1766 __wrap_malloc (size_t c)
1767 {
1768 printf ("malloc called with %zu\n", c);
1769 return __real_malloc (c);
1770 }
1771 If you link other code with this file using --wrap malloc, then all
1773 calls to "malloc" will call the function "__wrap_malloc" instead.
1774 The call to "__real_malloc" in "__wrap_malloc" will call the real
1775 "malloc" function.
1776 You may wish to provide a "__real_malloc" function as well, so that
1778 links without the --wrap option will succeed. If you do this, you
1779 should not put the definition of "__real_malloc" in the same file
1780 as "__wrap_malloc"; if you do, the assembler may resolve the call
1781 before the linker has a chance to wrap it to "malloc".
1782 --eh-frame-hdr
1784 --no-eh-frame-hdr
1785 Request (--eh-frame-hdr) or suppress (--no-eh-frame-hdr) the
1786 creation of ".eh_frame_hdr" section and ELF "PT_GNU_EH_FRAME"
1787 segment header.
1788 --no-ld-generated-unwind-info
1790 Request creation of ".eh_frame" unwind info for linker generated
1791 code sections like PLT. This option is on by default if linker
1792 generated unwind info is supported.
1793 --enable-new-dtags
1795 --disable-new-dtags
1796 This linker can create the new dynamic tags in ELF. But the older
1797 ELF systems may not understand them. If you specify
1798 --enable-new-dtags, the new dynamic tags will be created as needed
1799 and older dynamic tags will be omitted. If you specify
1800 --disable-new-dtags, no new dynamic tags will be created. By
1801 default, the new dynamic tags are not created. Note that those
1802 options are only available for ELF systems.
1803 --hash-size=number
1805 Set the default size of the linker's hash tables to a prime number
1806 close to number. Increasing this value can reduce the length of
1807 time it takes the linker to perform its tasks, at the expense of
1808 increasing the linker's memory requirements. Similarly reducing
1809 this value can reduce the memory requirements at the expense of
1810 speed.
1811 --hash-style=style
1813 Set the type of linker's hash table(s). style can be either "sysv"
1814 for classic ELF ".hash" section, "gnu" for new style GNU
1815 ".gnu.hash" section or "both" for both the classic ELF ".hash" and
1816 new style GNU ".gnu.hash" hash tables. The default is "sysv".
1817 --compress-debug-sections=none
1819 --compress-debug-sections=zlib
1820 --compress-debug-sections=zlib-gnu
1821 --compress-debug-sections=zlib-gabi
1822 On ELF platforms, these options control how DWARF debug sections
1823 are compressed using zlib.
1824 --compress-debug-sections=none doesn't compress DWARF debug
1826 sections. --compress-debug-sections=zlib-gnu compresses DWARF
1827 debug sections and renames them to begin with .zdebug instead of
1828 .debug. --compress-debug-sections=zlib-gabi also compresses DWARF
1829 debug sections, but rather than renaming them it sets the
1830 SHF_COMPRESSED flag in the sections' headers.
1831 The --compress-debug-sections=zlib option is an alias for
1833 --compress-debug-sections=zlib-gabi.
1834 Note that this option overrides any compression in input debug
1836 sections, so if a binary is linked with
1837 --compress-debug-sections=none for example, then any compressed
1838 debug sections in input files will be uncompressed before they are
1839 copied into the output binary.
1840 The default compression behaviour varies depending upon the target
1842 involved and the configure options used to build the toolchain.
1843 The default can be determined by examining the output from the
1844 linker's --help option.
1845 --reduce-memory-overheads
1847 This option reduces memory requirements at ld runtime, at the
1848 expense of linking speed. This was introduced to select the old
1849 O(n^2) algorithm for link map file generation, rather than the new
1850 O(n) algorithm which uses about 40% more memory for symbol storage.
1851 Another effect of the switch is to set the default hash table size
1853 to 1021, which again saves memory at the cost of lengthening the
1854 linker's run time. This is not done however if the --hash-size
1855 switch has been used.
1856 The --reduce-memory-overheads switch may be also be used to enable
1858 other tradeoffs in future versions of the linker.
1859 --build-id
1861 --build-id=style
1862 Request the creation of a ".note.gnu.build-id" ELF note section or
1863 a ".buildid" COFF section. The contents of the note are unique
1864 bits identifying this linked file. style can be "uuid" to use 128
1865 random bits, "sha1" to use a 160-bit SHA1 hash on the normative
1866 parts of the output contents, "md5" to use a 128-bit MD5 hash on
1867 the normative parts of the output contents, or "0xhexstring" to use
1868 a chosen bit string specified as an even number of hexadecimal
1869 digits ("-" and ":" characters between digit pairs are ignored).
1870 If style is omitted, "sha1" is used.
1871 The "md5" and "sha1" styles produces an identifier that is always
1873 the same in an identical output file, but will be unique among all
1874 nonidentical output files. It is not intended to be compared as a
1875 checksum for the file's contents. A linked file may be changed
1876 later by other tools, but the build ID bit string identifying the
1877 original linked file does not change.
1878 Passing "none" for style disables the setting from any "--build-id"
1880 options earlier on the command line.
1881 The i386 PE linker supports the -shared option, which causes the output
1883 to be a dynamically linked library (DLL) instead of a normal
1884 executable. You should name the output "*.dll" when you use this
1885 option. In addition, the linker fully supports the standard "*.def"
1886 files, which may be specified on the linker command line like an object
1887 file (in fact, it should precede archives it exports symbols from, to
1888 ensure that they get linked in, just like a normal object file).
1889 In addition to the options common to all targets, the i386 PE linker
1891 support additional command line options that are specific to the i386
1892 PE target. Options that take values may be separated from their values
1893 by either a space or an equals sign.
1894 --add-stdcall-alias
1896 If given, symbols with a stdcall suffix (@nn) will be exported as-
1897 is and also with the suffix stripped. [This option is specific to
1898 the i386 PE targeted port of the linker]
1899 --base-file file
1901 Use file as the name of a file in which to save the base addresses
1902 of all the relocations needed for generating DLLs with dlltool.
1903 [This is an i386 PE specific option]
1904 --dll
1906 Create a DLL instead of a regular executable. You may also use
1907 -shared or specify a "LIBRARY" in a given ".def" file. [This
1908 option is specific to the i386 PE targeted port of the linker]
1909 --enable-long-section-names
1911 --disable-long-section-names
1912 The PE variants of the COFF object format add an extension that
1913 permits the use of section names longer than eight characters, the
1914 normal limit for COFF. By default, these names are only allowed in
1915 object files, as fully-linked executable images do not carry the
1916 COFF string table required to support the longer names. As a GNU
1917 extension, it is possible to allow their use in executable images
1918 as well, or to (probably pointlessly!) disallow it in object
1919 files, by using these two options. Executable images generated
1920 with these long section names are slightly non-standard, carrying
1921 as they do a string table, and may generate confusing output when
1922 examined with non-GNU PE-aware tools, such as file viewers and
1923 dumpers. However, GDB relies on the use of PE long section names
1924 to find Dwarf-2 debug information sections in an executable image
1925 at runtime, and so if neither option is specified on the command-
1926 line, ld will enable long section names, overriding the default and
1927 technically correct behaviour, when it finds the presence of debug
1928 information while linking an executable image and not stripping
1929 symbols. [This option is valid for all PE targeted ports of the
1930 linker]
1931 --enable-stdcall-fixup
1933 --disable-stdcall-fixup
1934 If the link finds a symbol that it cannot resolve, it will attempt
1935 to do "fuzzy linking" by looking for another defined symbol that
1936 differs only in the format of the symbol name (cdecl vs stdcall)
1937 and will resolve that symbol by linking to the match. For example,
1938 the undefined symbol "_foo" might be linked to the function
1939 "_foo@12", or the undefined symbol "_bar@16" might be linked to the
1940 function "_bar". When the linker does this, it prints a warning,
1941 since it normally should have failed to link, but sometimes import
1942 libraries generated from third-party dlls may need this feature to
1943 be usable. If you specify --enable-stdcall-fixup, this feature is
1944 fully enabled and warnings are not printed. If you specify
1945 --disable-stdcall-fixup, this feature is disabled and such
1946 mismatches are considered to be errors. [This option is specific
1947 to the i386 PE targeted port of the linker]
1948 --leading-underscore
1950 --no-leading-underscore
1951 For most targets default symbol-prefix is an underscore and is
1952 defined in target's description. By this option it is possible to
1953 disable/enable the default underscore symbol-prefix.
1954 --export-all-symbols
1956 If given, all global symbols in the objects used to build a DLL
1957 will be exported by the DLL. Note that this is the default if
1958 there otherwise wouldn't be any exported symbols. When symbols are
1959 explicitly exported via DEF files or implicitly exported via
1960 function attributes, the default is to not export anything else
1961 unless this option is given. Note that the symbols "DllMain@12",
1962 "DllEntryPoint@0", "DllMainCRTStartup@12", and "impure_ptr" will
1963 not be automatically exported. Also, symbols imported from other
1964 DLLs will not be re-exported, nor will symbols specifying the DLL's
1965 internal layout such as those beginning with "_head_" or ending
1966 with "_iname". In addition, no symbols from "libgcc", "libstd++",
1967 "libmingw32", or "crtX.o" will be exported. Symbols whose names
1968 begin with "__rtti_" or "__builtin_" will not be exported, to help
1969 with C++ DLLs. Finally, there is an extensive list of cygwin-
1970 private symbols that are not exported (obviously, this applies on
1971 when building DLLs for cygwin targets). These cygwin-excludes are:
1972 "_cygwin_dll_entry@12", "_cygwin_crt0_common@8",
1973 "_cygwin_noncygwin_dll_entry@12", "_fmode", "_impure_ptr",
1974 "cygwin_attach_dll", "cygwin_premain0", "cygwin_premain1",
1975 "cygwin_premain2", "cygwin_premain3", and "environ". [This option
1976 is specific to the i386 PE targeted port of the linker]
1977 --exclude-symbols symbol,symbol,...
1979 Specifies a list of symbols which should not be automatically
1980 exported. The symbol names may be delimited by commas or colons.
1981 [This option is specific to the i386 PE targeted port of the
1982 linker]
1983 --exclude-all-symbols
1985 Specifies no symbols should be automatically exported. [This
1986 option is specific to the i386 PE targeted port of the linker]
1987 --file-alignment
1989 Specify the file alignment. Sections in the file will always begin
1990 at file offsets which are multiples of this number. This defaults
1991 to 512. [This option is specific to the i386 PE targeted port of
1992 the linker]
1993 --heap reserve
1995 --heap reserve,commit
1996 Specify the number of bytes of memory to reserve (and optionally
1997 commit) to be used as heap for this program. The default is 1MB
1998 reserved, 4K committed. [This option is specific to the i386 PE
1999 targeted port of the linker]
2000 --image-base value
2002 Use value as the base address of your program or dll. This is the
2003 lowest memory location that will be used when your program or dll
2004 is loaded. To reduce the need to relocate and improve performance
2005 of your dlls, each should have a unique base address and not
2006 overlap any other dlls. The default is 0x400000 for executables,
2007 and 0x10000000 for dlls. [This option is specific to the i386 PE
2008 targeted port of the linker]
2009 --kill-at
2011 If given, the stdcall suffixes (@nn) will be stripped from symbols
2012 before they are exported. [This option is specific to the i386 PE
2013 targeted port of the linker]
2014 --large-address-aware
2016 If given, the appropriate bit in the "Characteristics" field of the
2017 COFF header is set to indicate that this executable supports
2018 virtual addresses greater than 2 gigabytes. This should be used in
2019 conjunction with the /3GB or /USERVA=value megabytes switch in the
2020 "[operating systems]" section of the BOOT.INI. Otherwise, this bit
2021 has no effect. [This option is specific to PE targeted ports of
2022 the linker]
2023 --disable-large-address-aware
2025 Reverts the effect of a previous --large-address-aware option.
2026 This is useful if --large-address-aware is always set by the
2027 compiler driver (e.g. Cygwin gcc) and the executable does not
2028 support virtual addresses greater than 2 gigabytes. [This option
2029 is specific to PE targeted ports of the linker]
2030 --major-image-version value
2032 Sets the major number of the "image version". Defaults to 1.
2033 [This option is specific to the i386 PE targeted port of the
2034 linker]
2035 --major-os-version value
2037 Sets the major number of the "os version". Defaults to 4. [This
2038 option is specific to the i386 PE targeted port of the linker]
2039 --major-subsystem-version value
2041 Sets the major number of the "subsystem version". Defaults to 4.
2042 [This option is specific to the i386 PE targeted port of the
2043 linker]
2044 --minor-image-version value
2046 Sets the minor number of the "image version". Defaults to 0.
2047 [This option is specific to the i386 PE targeted port of the
2048 linker]
2049 --minor-os-version value
2051 Sets the minor number of the "os version". Defaults to 0. [This
2052 option is specific to the i386 PE targeted port of the linker]
2053 --minor-subsystem-version value
2055 Sets the minor number of the "subsystem version". Defaults to 0.
2056 [This option is specific to the i386 PE targeted port of the
2057 linker]
2058 --output-def file
2060 The linker will create the file file which will contain a DEF file
2061 corresponding to the DLL the linker is generating. This DEF file
2062 (which should be called "*.def") may be used to create an import
2063 library with "dlltool" or may be used as a reference to
2064 automatically or implicitly exported symbols. [This option is
2065 specific to the i386 PE targeted port of the linker]
2066 --enable-auto-image-base
2068 --enable-auto-image-base=value
2069 Automatically choose the image base for DLLs, optionally starting
2070 with base value, unless one is specified using the "--image-base"
2071 argument. By using a hash generated from the dllname to create
2072 unique image bases for each DLL, in-memory collisions and
2073 relocations which can delay program execution are avoided. [This
2074 option is specific to the i386 PE targeted port of the linker]
2075 --disable-auto-image-base
2077 Do not automatically generate a unique image base. If there is no
2078 user-specified image base ("--image-base") then use the platform
2079 default. [This option is specific to the i386 PE targeted port of
2080 the linker]
2081 --dll-search-prefix string
2083 When linking dynamically to a dll without an import library, search
2084 for "<string><basename>.dll" in preference to "lib<basename>.dll".
2085 This behaviour allows easy distinction between DLLs built for the
2086 various "subplatforms": native, cygwin, uwin, pw, etc. For
2087 instance, cygwin DLLs typically use "--dll-search-prefix=cyg".
2088 [This option is specific to the i386 PE targeted port of the
2089 linker]
2090 --enable-auto-import
2092 Do sophisticated linking of "_symbol" to "__imp__symbol" for DATA
2093 imports from DLLs, and create the necessary thunking symbols when
2094 building the import libraries with those DATA exports. Note: Use of
2095 the 'auto-import' extension will cause the text section of the
2096 image file to be made writable. This does not conform to the PE-
2097 COFF format specification published by Microsoft.
2098 Note - use of the 'auto-import' extension will also cause read only
2100 data which would normally be placed into the .rdata section to be
2101 placed into the .data section instead. This is in order to work
2102 around a problem with consts that is described here:
2103 http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
2104 Using 'auto-import' generally will 'just work' -- but sometimes you
2106 may see this message:
2107 "variable '<var>' can't be auto-imported. Please read the
2109 documentation for ld's "--enable-auto-import" for details."
2110 This message occurs when some (sub)expression accesses an address
2112 ultimately given by the sum of two constants (Win32 import tables
2113 only allow one). Instances where this may occur include accesses
2114 to member fields of struct variables imported from a DLL, as well
2115 as using a constant index into an array variable imported from a
2116 DLL. Any multiword variable (arrays, structs, long long, etc) may
2117 trigger this error condition. However, regardless of the exact
2118 data type of the offending exported variable, ld will always detect
2119 it, issue the warning, and exit.
2120 There are several ways to address this difficulty, regardless of
2122 the data type of the exported variable:
2123 One way is to use --enable-runtime-pseudo-reloc switch. This leaves
2125 the task of adjusting references in your client code for runtime
2126 environment, so this method works only when runtime environment
2127 supports this feature.
2128 A second solution is to force one of the 'constants' to be a
2130 variable -- that is, unknown and un-optimizable at compile time.
2131 For arrays, there are two possibilities: a) make the indexee (the
2132 array's address) a variable, or b) make the 'constant' index a
2133 variable. Thus:
2134 extern type extern_array[];
2136 extern_array[1] -->
2137 { volatile type *t=extern_array; t[1] }
2138 or
2140 extern type extern_array[];
2142 extern_array[1] -->
2143 { volatile int t=1; extern_array[t] }
2144 For structs (and most other multiword data types) the only option
2146 is to make the struct itself (or the long long, or the ...)
2147 variable:
2148 extern struct s extern_struct;
2150 extern_struct.field -->
2151 { volatile struct s *t=&extern_struct; t->field }
2152 or
2154 extern long long extern_ll;
2156 extern_ll -->
2157 { volatile long long * local_ll=&extern_ll; *local_ll }
2158 A third method of dealing with this difficulty is to abandon
2160 'auto-import' for the offending symbol and mark it with
2161 "__declspec(dllimport)". However, in practice that requires using
2162 compile-time #defines to indicate whether you are building a DLL,
2163 building client code that will link to the DLL, or merely
2164 building/linking to a static library. In making the choice
2165 between the various methods of resolving the 'direct address with
2166 constant offset' problem, you should consider typical real-world
2167 usage:
2168 Original:
2170 --foo.h
2172 extern int arr[];
2173 --foo.c
2174 #include "foo.h"
2175 void main(int argc, char **argv){
2176 printf("%d\n",arr[1]);
2177 }
2178 Solution 1:
2180 --foo.h
2182 extern int arr[];
2183 --foo.c
2184 #include "foo.h"
2185 void main(int argc, char **argv){
2186 /* This workaround is for win32 and cygwin; do not "optimize" */
2187 volatile int *parr = arr;
2188 printf("%d\n",parr[1]);
2189 }
2190 Solution 2:
2192 --foo.h
2194 /* Note: auto-export is assumed (no __declspec(dllexport)) */
2195 #if (defined(_WIN32) || defined(__CYGWIN__)) && \
2196 !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
2197 #define FOO_IMPORT __declspec(dllimport)
2198 #else
2199 #define FOO_IMPORT
2200 #endif
2201 extern FOO_IMPORT int arr[];
2202 --foo.c
2203 #include "foo.h"
2204 void main(int argc, char **argv){
2205 printf("%d\n",arr[1]);
2206 }
2207 A fourth way to avoid this problem is to re-code your library to
2209 use a functional interface rather than a data interface for the
2210 offending variables (e.g. set_foo() and get_foo() accessor
2211 functions). [This option is specific to the i386 PE targeted port
2212 of the linker]
2213 --disable-auto-import
2215 Do not attempt to do sophisticated linking of "_symbol" to
2216 "__imp__symbol" for DATA imports from DLLs. [This option is
2217 specific to the i386 PE targeted port of the linker]
2218 --enable-runtime-pseudo-reloc
2220 If your code contains expressions described in --enable-auto-import
2221 section, that is, DATA imports from DLL with non-zero offset, this
2222 switch will create a vector of 'runtime pseudo relocations' which
2223 can be used by runtime environment to adjust references to such
2224 data in your client code. [This option is specific to the i386 PE
2225 targeted port of the linker]
2226 --disable-runtime-pseudo-reloc
2228 Do not create pseudo relocations for non-zero offset DATA imports
2229 from DLLs. [This option is specific to the i386 PE targeted port
2230 of the linker]
2231 --enable-extra-pe-debug
2233 Show additional debug info related to auto-import symbol thunking.
2234 [This option is specific to the i386 PE targeted port of the
2235 linker]
2236 --section-alignment
2238 Sets the section alignment. Sections in memory will always begin
2239 at addresses which are a multiple of this number. Defaults to
2240 0x1000. [This option is specific to the i386 PE targeted port of
2241 the linker]
2242 --stack reserve
2244 --stack reserve,commit
2245 Specify the number of bytes of memory to reserve (and optionally
2246 commit) to be used as stack for this program. The default is 2MB
2247 reserved, 4K committed. [This option is specific to the i386 PE
2248 targeted port of the linker]
2249 --subsystem which
2251 --subsystem which:major
2252 --subsystem which:major.minor
2253 Specifies the subsystem under which your program will execute. The
2254 legal values for which are "native", "windows", "console", "posix",
2255 and "xbox". You may optionally set the subsystem version also.
2256 Numeric values are also accepted for which. [This option is
2257 specific to the i386 PE targeted port of the linker]
2258 The following options set flags in the "DllCharacteristics" field
2260 of the PE file header: [These options are specific to PE targeted
2261 ports of the linker]
2262 --high-entropy-va
2264 Image is compatible with 64-bit address space layout randomization
2265 (ASLR).
2266 --dynamicbase
2268 The image base address may be relocated using address space layout
2269 randomization (ASLR). This feature was introduced with MS Windows
2270 Vista for i386 PE targets.
2271 --forceinteg
2273 Code integrity checks are enforced.
2274 --nxcompat
2276 The image is compatible with the Data Execution Prevention. This
2277 feature was introduced with MS Windows XP SP2 for i386 PE targets.
2278 --no-isolation
2280 Although the image understands isolation, do not isolate the image.
2281 --no-seh
2283 The image does not use SEH. No SE handler may be called from this
2284 image.
2285 --no-bind
2287 Do not bind this image.
2288 --wdmdriver
2290 The driver uses the MS Windows Driver Model.
2291 --tsaware
2293 The image is Terminal Server aware.
2294 --insert-timestamp
2296 --no-insert-timestamp
2297 Insert a real timestamp into the image. This is the default
2298 behaviour as it matches legacy code and it means that the image
2299 will work with other, proprietary tools. The problem with this
2300 default is that it will result in slightly different images being
2301 produced each time the same sources are linked. The option
2302 --no-insert-timestamp can be used to insert a zero value for the
2303 timestamp, this ensuring that binaries produced from identical
2304 sources will compare identically.
2305 The C6X uClinux target uses a binary format called DSBT to support
2307 shared libraries. Each shared library in the system needs to have a
2308 unique index; all executables use an index of 0.
2309 --dsbt-size size
2311 This option sets the number of entries in the DSBT of the current
2312 executable or shared library to size. The default is to create a
2313 table with 64 entries.
2314 --dsbt-index index
2316 This option sets the DSBT index of the current executable or shared
2317 library to index. The default is 0, which is appropriate for
2318 generating executables. If a shared library is generated with a
2319 DSBT index of 0, the "R_C6000_DSBT_INDEX" relocs are copied into
2320 the output file.
2321 The --no-merge-exidx-entries switch disables the merging of
2323 adjacent exidx entries in frame unwind info.
2324 The 68HC11 and 68HC12 linkers support specific options to control the
2326 memory bank switching mapping and trampoline code generation.
2327 --no-trampoline
2329 This option disables the generation of trampoline. By default a
2330 trampoline is generated for each far function which is called using
2331 a "jsr" instruction (this happens when a pointer to a far function
2332 is taken).
2333 --bank-window name
2335 This option indicates to the linker the name of the memory region
2336 in the MEMORY specification that describes the memory bank window.
2337 The definition of such region is then used by the linker to compute
2338 paging and addresses within the memory window.
2339 The following options are supported to control handling of GOT
2341 generation when linking for 68K targets.
2342 --got=type
2344 This option tells the linker which GOT generation scheme to use.
2345 type should be one of single, negative, multigot or target. For
2346 more information refer to the Info entry for ld.
2347 The following options are supported to control microMIPS instruction
2349 generation and branch relocation checks for ISA mode transitions when
2350 linking for MIPS targets.
2351 --insn32
2353 --no-insn32
2354 These options control the choice of microMIPS instructions used in
2355 code generated by the linker, such as that in the PLT or lazy
2356 binding stubs, or in relaxation. If --insn32 is used, then the
2357 linker only uses 32-bit instruction encodings. By default or if
2358 --no-insn32 is used, all instruction encodings are used, including
2359 16-bit ones where possible.
2360 --ignore-branch-isa
2362 --no-ignore-branch-isa
2363 These options control branch relocation checks for invalid ISA mode
2364 transitions. If --ignore-branch-isa is used, then the linker
2365 accepts any branch relocations and any ISA mode transition required
2366 is lost in relocation calculation, except for some cases of "BAL"
2367 instructions which meet relaxation conditions and are converted to
2368 equivalent "JALX" instructions as the associated relocation is
2369 calculated. By default or if --no-ignore-branch-isa is used a
2370 check is made causing the loss of an ISA mode transition to produce
2371 an error.
2372
2374 You can change the behaviour of ld with the environment variables
2375 "GNUTARGET", "LDEMULATION" and "COLLECT_NO_DEMANGLE".
2376 "GNUTARGET" determines the input-file object format if you don't use -b
2378 (or its synonym --format). Its value should be one of the BFD names
2379 for an input format. If there is no "GNUTARGET" in the environment, ld
2380 uses the natural format of the target. If "GNUTARGET" is set to
2381 "default" then BFD attempts to discover the input format by examining
2382 binary input files; this method often succeeds, but there are potential
2383 ambiguities, since there is no method of ensuring that the magic number
2384 used to specify object-file formats is unique. However, the
2385 configuration procedure for BFD on each system places the conventional
2386 format for that system first in the search-list, so ambiguities are
2387 resolved in favor of convention.
2388 "LDEMULATION" determines the default emulation if you don't use the -m
2390 option. The emulation can affect various aspects of linker behaviour,
2391 particularly the default linker script. You can list the available
2392 emulations with the --verbose or -V options. If the -m option is not
2393 used, and the "LDEMULATION" environment variable is not defined, the
2394 default emulation depends upon how the linker was configured.
2395 Normally, the linker will default to demangling symbols. However, if
2397 "COLLECT_NO_DEMANGLE" is set in the environment, then it will default
2398 to not demangling symbols. This environment variable is used in a
2399 similar fashion by the "gcc" linker wrapper program. The default may
2400 be overridden by the --demangle and --no-demangle options.
2401
2403 ar(1), nm(1), objcopy(1), objdump(1), readelf(1) and the Info entries
2404 for binutils and ld.
2405
2407 Copyright (c) 1991-2018 Free Software Foundation, Inc.
2408 Permission is granted to copy, distribute and/or modify this document
2410 under the terms of the GNU Free Documentation License, Version 1.3 or
2411 any later version published by the Free Software Foundation; with no
2412 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
2413 Texts. A copy of the license is included in the section entitled "GNU
2414 Free Documentation License".
2415binutils-2.30 2019-05-11 LD(1)