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 "=", then the "=" will be replaced by the
402 sysroot prefix, a path specified when the linker is configured.
403 The default set of paths searched (without being specified with -L)
405 depends on which emulation mode ld is using, and in some cases also
406 on how it was configured.
407 The paths can also be specified in a link script with the
409 "SEARCH_DIR" command. Directories specified this way are searched
410 at the point in which the linker script appears in the command
411 line.
412 -m emulation
414 Emulate the emulation linker. You can list the available
415 emulations with the --verbose or -V options.
416 If the -m option is not used, the emulation is taken from the
418 "LDEMULATION" environment variable, if that is defined.
419 Otherwise, the default emulation depends upon how the linker was
421 configured.
422 -M
424 --print-map
425 Print a link map to the standard output. A link map provides
426 information about the link, including the following:
427 · Where object files are mapped into memory.
429 · How common symbols are allocated.
431 · All archive members included in the link, with a mention of the
433 symbol which caused the archive member to be brought in.
434 · The values assigned to symbols.
436 Note - symbols whose values are computed by an expression which
438 involves a reference to a previous value of the same symbol may
439 not have correct result displayed in the link map. This is
440 because the linker discards intermediate results and only
441 retains the final value of an expression. Under such
442 circumstances the linker will display the final value enclosed
443 by square brackets. Thus for example a linker script
444 containing:
445 foo = 1
447 foo = foo * 4
448 foo = foo + 8
449 will produce the following output in the link map if the -M
451 option is used:
452 0x00000001 foo = 0x1
454 [0x0000000c] foo = (foo * 0x4)
455 [0x0000000c] foo = (foo + 0x8)
456 See Expressions for more information about expressions in
458 linker scripts.
459 -n
461 --nmagic
462 Turn off page alignment of sections, and disable linking against
463 shared libraries. If the output format supports Unix style magic
464 numbers, mark the output as "NMAGIC".
465 -N
467 --omagic
468 Set the text and data sections to be readable and writable. Also,
469 do not page-align the data segment, and disable linking against
470 shared libraries. If the output format supports Unix style magic
471 numbers, mark the output as "OMAGIC". Note: Although a writable
472 text section is allowed for PE-COFF targets, it does not conform to
473 the format specification published by Microsoft.
474 --no-omagic
476 This option negates most of the effects of the -N option. It sets
477 the text section to be read-only, and forces the data segment to be
478 page-aligned. Note - this option does not enable linking against
479 shared libraries. Use -Bdynamic for this.
480 -o output
482 --output=output
483 Use output as the name for the program produced by ld; if this
484 option is not specified, the name a.out is used by default. The
485 script command "OUTPUT" can also specify the output file name.
486 -O level
488 If level is a numeric values greater than zero ld optimizes the
489 output. This might take significantly longer and therefore
490 probably should only be enabled for the final binary. At the
491 moment this option only affects ELF shared library generation.
492 Future releases of the linker may make more use of this option.
493 Also currently there is no difference in the linker's behaviour for
494 different non-zero values of this option. Again this may change
495 with future releases.
496 -q
498 --emit-relocs
499 Leave relocation sections and contents in fully linked executables.
500 Post link analysis and optimization tools may need this information
501 in order to perform correct modifications of executables. This
502 results in larger executables.
503 This option is currently only supported on ELF platforms.
505 --force-dynamic
507 Force the output file to have dynamic sections. This option is
508 specific to VxWorks targets.
509 -r
511 --relocatable
512 Generate relocatable output---i.e., generate an output file that
513 can in turn serve as input to ld. This is often called partial
514 linking. As a side effect, in environments that support standard
515 Unix magic numbers, this option also sets the output file's magic
516 number to "OMAGIC". If this option is not specified, an absolute
517 file is produced. When linking C++ programs, this option will not
518 resolve references to constructors; to do that, use -Ur.
519 When an input file does not have the same format as the output
521 file, partial linking is only supported if that input file does not
522 contain any relocations. Different output formats can have further
523 restrictions; for example some "a.out"-based formats do not support
524 partial linking with input files in other formats at all.
525 This option does the same thing as -i.
527 -R filename
529 --just-symbols=filename
530 Read symbol names and their addresses from filename, but do not
531 relocate it or include it in the output. This allows your output
532 file to refer symbolically to absolute locations of memory defined
533 in other programs. You may use this option more than once.
534 For compatibility with other ELF linkers, if the -R option is
536 followed by a directory name, rather than a file name, it is
537 treated as the -rpath option.
538 -s
540 --strip-all
541 Omit all symbol information from the output file.
542 -S
544 --strip-debug
545 Omit debugger symbol information (but not all symbols) from the
546 output file.
547 -t
549 --trace
550 Print the names of the input files as ld processes them.
551 -T scriptfile
553 --script=scriptfile
554 Use scriptfile as the linker script. This script replaces ld's
555 default linker script (rather than adding to it), so commandfile
556 must specify everything necessary to describe the output file.
557 If scriptfile does not exist in the current directory, "ld" looks
558 for it in the directories specified by any preceding -L options.
559 Multiple -T options accumulate.
560 -dT scriptfile
562 --default-script=scriptfile
563 Use scriptfile as the default linker script.
564 This option is similar to the --script option except that
566 processing of the script is delayed until after the rest of the
567 command line has been processed. This allows options placed after
568 the --default-script option on the command line to affect the
569 behaviour of the linker script, which can be important when the
570 linker command line cannot be directly controlled by the user. (eg
571 because the command line is being constructed by another tool, such
572 as gcc).
573 -u symbol
575 --undefined=symbol
576 Force symbol to be entered in the output file as an undefined
577 symbol. Doing this may, for example, trigger linking of additional
578 modules from standard libraries. -u may be repeated with different
579 option arguments to enter additional undefined symbols. This
580 option is equivalent to the "EXTERN" linker script command.
581 -Ur For anything other than C++ programs, this option is equivalent to
583 -r: it generates relocatable output---i.e., an output file that can
584 in turn serve as input to ld. When linking C++ programs, -Ur does
585 resolve references to constructors, unlike -r. It does not work to
586 use -Ur on files that were themselves linked with -Ur; once the
587 constructor table has been built, it cannot be added to. Use -Ur
588 only for the last partial link, and -r for the others.
589 --unique[=SECTION]
591 Creates a separate output section for every input section matching
592 SECTION, or if the optional wildcard SECTION argument is missing,
593 for every orphan input section. An orphan section is one not
594 specifically mentioned in a linker script. You may use this option
595 multiple times on the command line; It prevents the normal merging
596 of input sections with the same name, overriding output section
597 assignments in a linker script.
598 -v
600 --version
601 -V Display the version number for ld. The -V option also lists the
602 supported emulations.
603 -x
605 --discard-all
606 Delete all local symbols.
607 -X
609 --discard-locals
610 Delete all temporary local symbols. (These symbols start with
611 system-specific local label prefixes, typically .L for ELF systems
612 or L for traditional a.out systems.)
613 -y symbol
615 --trace-symbol=symbol
616 Print the name of each linked file in which symbol appears. This
617 option may be given any number of times. On many systems it is
618 necessary to prepend an underscore.
619 This option is useful when you have an undefined symbol in your
621 link but don't know where the reference is coming from.
622 -Y path
624 Add path to the default library search path. This option exists
625 for Solaris compatibility.
626 -z keyword
628 The recognized keywords are:
629 combreloc
631 Combines multiple reloc sections and sorts them to make dynamic
632 symbol lookup caching possible.
633 defs
635 Disallows undefined symbols in object files. Undefined symbols
636 in shared libraries are still allowed.
637 execstack
639 Marks the object as requiring executable stack.
640 global
642 This option is only meaningful when building a shared object.
643 It makes the symbols defined by this shared object available
644 for symbol resolution of subsequently loaded libraries.
645 initfirst
647 This option is only meaningful when building a shared object.
648 It marks the object so that its runtime initialization will
649 occur before the runtime initialization of any other objects
650 brought into the process at the same time. Similarly the
651 runtime finalization of the object will occur after the runtime
652 finalization of any other objects.
653 interpose
655 Marks the object that its symbol table interposes before all
656 symbols but the primary executable.
657 lazy
659 When generating an executable or shared library, mark it to
660 tell the dynamic linker to defer function call resolution to
661 the point when the function is called (lazy binding), rather
662 than at load time. Lazy binding is the default.
663 loadfltr
665 Marks the object that its filters be processed immediately at
666 runtime.
667 muldefs
669 Allows multiple definitions.
670 nocombreloc
672 Disables multiple reloc sections combining.
673 nocopyreloc
675 Disables production of copy relocs.
676 nodefaultlib
678 Marks the object that the search for dependencies of this
679 object will ignore any default library search paths.
680 nodelete
682 Marks the object shouldn't be unloaded at runtime.
683 nodlopen
685 Marks the object not available to "dlopen".
686 nodump
688 Marks the object can not be dumped by "dldump".
689 noexecstack
691 Marks the object as not requiring executable stack.
692 norelro
694 Don't create an ELF "PT_GNU_RELRO" segment header in the
695 object.
696 now When generating an executable or shared library, mark it to
698 tell the dynamic linker to resolve all symbols when the program
699 is started, or when the shared library is linked to using
700 dlopen, instead of deferring function call resolution to the
701 point when the function is first called.
702 origin
704 Marks the object may contain $ORIGIN.
705 relro
707 Create an ELF "PT_GNU_RELRO" segment header in the object.
708 max-page-size=value
710 Set the emulation maximum page size to value.
711 common-page-size=value
713 Set the emulation common page size to value.
714 stack-size=value
716 Specify a stack size for in an ELF "PT_GNU_STACK" segment.
717 Specifying zero will override any default non-zero sized
718 "PT_GNU_STACK" segment creation.
719 Other keywords are ignored for Solaris compatibility.
721 -( archives -)
723 --start-group archives --end-group
724 The archives should be a list of archive files. They may be either
725 explicit file names, or -l options.
726 The specified archives are searched repeatedly until no new
728 undefined references are created. Normally, an archive is searched
729 only once in the order that it is specified on the command line.
730 If a symbol in that archive is needed to resolve an undefined
731 symbol referred to by an object in an archive that appears later on
732 the command line, the linker would not be able to resolve that
733 reference. By grouping the archives, they all be searched
734 repeatedly until all possible references are resolved.
735 Using this option has a significant performance cost. It is best
737 to use it only when there are unavoidable circular references
738 between two or more archives.
739 --accept-unknown-input-arch
741 --no-accept-unknown-input-arch
742 Tells the linker to accept input files whose architecture cannot be
743 recognised. The assumption is that the user knows what they are
744 doing and deliberately wants to link in these unknown input files.
745 This was the default behaviour of the linker, before release 2.14.
746 The default behaviour from release 2.14 onwards is to reject such
747 input files, and so the --accept-unknown-input-arch option has been
748 added to restore the old behaviour.
749 --as-needed
751 --no-as-needed
752 This option affects ELF DT_NEEDED tags for dynamic libraries
753 mentioned on the command line after the --as-needed option.
754 Normally the linker will add a DT_NEEDED tag for each dynamic
755 library mentioned on the command line, regardless of whether the
756 library is actually needed or not. --as-needed causes a DT_NEEDED
757 tag to only be emitted for a library that at that point in the link
758 satisfies a non-weak undefined symbol reference from a regular
759 object file or, if the library is not found in the DT_NEEDED lists
760 of other libraries, a non-weak undefined symbol reference from
761 another dynamic library. Object files or libraries appearing on
762 the command line after the library in question do not affect
763 whether the library is seen as needed. This is similar to the
764 rules for extraction of object files from archives. --no-as-needed
765 restores the default behaviour.
766 --add-needed
768 --no-add-needed
769 These two options have been deprecated because of the similarity of
770 their names to the --as-needed and --no-as-needed options. They
771 have been replaced by --copy-dt-needed-entries and
772 --no-copy-dt-needed-entries.
773 -assert keyword
775 This option is ignored for SunOS compatibility.
776 -Bdynamic
778 -dy
779 -call_shared
780 Link against dynamic libraries. This is only meaningful on
781 platforms for which shared libraries are supported. This option is
782 normally the default on such platforms. The different variants of
783 this option are for compatibility with various systems. You may
784 use this option multiple times on the command line: it affects
785 library searching for -l options which follow it.
786 -Bgroup
788 Set the "DF_1_GROUP" flag in the "DT_FLAGS_1" entry in the dynamic
789 section. This causes the runtime linker to handle lookups in this
790 object and its dependencies to be performed only inside the group.
791 --unresolved-symbols=report-all is implied. This option is only
792 meaningful on ELF platforms which support shared libraries.
793 -Bstatic
795 -dn
796 -non_shared
797 -static
798 Do not link against shared libraries. This is only meaningful on
799 platforms for which shared libraries are supported. The different
800 variants of this option are for compatibility with various systems.
801 You may use this option multiple times on the command line: it
802 affects library searching for -l options which follow it. This
803 option also implies --unresolved-symbols=report-all. This option
804 can be used with -shared. Doing so means that a shared library is
805 being created but that all of the library's external references
806 must be resolved by pulling in entries from static libraries.
807 -Bsymbolic
809 When creating a shared library, bind references to global symbols
810 to the definition within the shared library, if any. Normally, it
811 is possible for a program linked against a shared library to
812 override the definition within the shared library. This option is
813 only meaningful on ELF platforms which support shared libraries.
814 -Bsymbolic-functions
816 When creating a shared library, bind references to global function
817 symbols to the definition within the shared library, if any. This
818 option is only meaningful on ELF platforms which support shared
819 libraries.
820 --dynamic-list=dynamic-list-file
822 Specify the name of a dynamic list file to the linker. This is
823 typically used when creating shared libraries to specify a list of
824 global symbols whose references shouldn't be bound to the
825 definition within the shared library, or creating dynamically
826 linked executables to specify a list of symbols which should be
827 added to the symbol table in the executable. This option is only
828 meaningful on ELF platforms which support shared libraries.
829 The format of the dynamic list is the same as the version node
831 without scope and node name. See VERSION for more information.
832 --dynamic-list-data
834 Include all global data symbols to the dynamic list.
835 --dynamic-list-cpp-new
837 Provide the builtin dynamic list for C++ operator new and delete.
838 It is mainly useful for building shared libstdc++.
839 --dynamic-list-cpp-typeinfo
841 Provide the builtin dynamic list for C++ runtime type
842 identification.
843 --check-sections
845 --no-check-sections
846 Asks the linker not to check section addresses after they have been
847 assigned to see if there are any overlaps. Normally the linker
848 will perform this check, and if it finds any overlaps it will
849 produce suitable error messages. The linker does know about, and
850 does make allowances for sections in overlays. The default
851 behaviour can be restored by using the command line switch
852 --check-sections. Section overlap is not usually checked for
853 relocatable links. You can force checking in that case by using
854 the --check-sections option.
855 --copy-dt-needed-entries
857 --no-copy-dt-needed-entries
858 This option affects the treatment of dynamic libraries referred to
859 by DT_NEEDED tags inside ELF dynamic libraries mentioned on the
860 command line. Normally the linker won't add a DT_NEEDED tag to the
861 output binary for each library mentioned in a DT_NEEDED tag in an
862 input dynamic library. With --copy-dt-needed-entries specified on
863 the command line however any dynamic libraries that follow it will
864 have their DT_NEEDED entries added. The default behaviour can be
865 restored with --no-copy-dt-needed-entries.
866 This option also has an effect on the resolution of symbols in
868 dynamic libraries. With --copy-dt-needed-entries dynamic libraries
869 mentioned on the command line will be recursively searched,
870 following their DT_NEEDED tags to other libraries, in order to
871 resolve symbols required by the output binary. With the default
872 setting however the searching of dynamic libraries that follow it
873 will stop with the dynamic library itself. No DT_NEEDED links will
874 be traversed to resolve symbols.
875 --cref
877 Output a cross reference table. If a linker map file is being
878 generated, the cross reference table is printed to the map file.
879 Otherwise, it is printed on the standard output.
880 The format of the table is intentionally simple, so that it may be
882 easily processed by a script if necessary. The symbols are printed
883 out, sorted by name. For each symbol, a list of file names is
884 given. If the symbol is defined, the first file listed is the
885 location of the definition. If the symbol is defined as a common
886 value then any files where this happens appear next. Finally any
887 files that reference the symbol are listed.
888 --no-define-common
890 This option inhibits the assignment of addresses to common symbols.
891 The script command "INHIBIT_COMMON_ALLOCATION" has the same effect.
892 The --no-define-common option allows decoupling the decision to
894 assign addresses to Common symbols from the choice of the output
895 file type; otherwise a non-Relocatable output type forces assigning
896 addresses to Common symbols. Using --no-define-common allows
897 Common symbols that are referenced from a shared library to be
898 assigned addresses only in the main program. This eliminates the
899 unused duplicate space in the shared library, and also prevents any
900 possible confusion over resolving to the wrong duplicate when there
901 are many dynamic modules with specialized search paths for runtime
902 symbol resolution.
903 --defsym=symbol=expression
905 Create a global symbol in the output file, containing the absolute
906 address given by expression. You may use this option as many times
907 as necessary to define multiple symbols in the command line. A
908 limited form of arithmetic is supported for the expression in this
909 context: you may give a hexadecimal constant or the name of an
910 existing symbol, or use "+" and "-" to add or subtract hexadecimal
911 constants or symbols. If you need more elaborate expressions,
912 consider using the linker command language from a script. Note:
913 there should be no white space between symbol, the equals sign
914 ("="), and expression.
915 --demangle[=style]
917 --no-demangle
918 These options control whether to demangle symbol names in error
919 messages and other output. When the linker is told to demangle, it
920 tries to present symbol names in a readable fashion: it strips
921 leading underscores if they are used by the object file format, and
922 converts C++ mangled symbol names into user readable names.
923 Different compilers have different mangling styles. The optional
924 demangling style argument can be used to choose an appropriate
925 demangling style for your compiler. The linker will demangle by
926 default unless the environment variable COLLECT_NO_DEMANGLE is set.
927 These options may be used to override the default.
928 -Ifile
930 --dynamic-linker=file
931 Set the name of the dynamic linker. This is only meaningful when
932 generating dynamically linked ELF executables. The default dynamic
933 linker is normally correct; don't use this unless you know what you
934 are doing.
935 --fatal-warnings
937 --no-fatal-warnings
938 Treat all warnings as errors. The default behaviour can be
939 restored with the option --no-fatal-warnings.
940 --force-exe-suffix
942 Make sure that an output file has a .exe suffix.
943 If a successfully built fully linked output file does not have a
945 ".exe" or ".dll" suffix, this option forces the linker to copy the
946 output file to one of the same name with a ".exe" suffix. This
947 option is useful when using unmodified Unix makefiles on a
948 Microsoft Windows host, since some versions of Windows won't run an
949 image unless it ends in a ".exe" suffix.
950 --gc-sections
952 --no-gc-sections
953 Enable garbage collection of unused input sections. It is ignored
954 on targets that do not support this option. The default behaviour
955 (of not performing this garbage collection) can be restored by
956 specifying --no-gc-sections on the command line.
957 --gc-sections decides which input sections are used by examining
959 symbols and relocations. The section containing the entry symbol
960 and all sections containing symbols undefined on the command-line
961 will be kept, as will sections containing symbols referenced by
962 dynamic objects. Note that when building shared libraries, the
963 linker must assume that any visible symbol is referenced. Once
964 this initial set of sections has been determined, the linker
965 recursively marks as used any section referenced by their
966 relocations. See --entry and --undefined.
967 This option can be set when doing a partial link (enabled with
969 option -r). In this case the root of symbols kept must be
970 explicitly specified either by an --entry or --undefined option or
971 by a "ENTRY" command in the linker script.
972 --print-gc-sections
974 --no-print-gc-sections
975 List all sections removed by garbage collection. The listing is
976 printed on stderr. This option is only effective if garbage
977 collection has been enabled via the --gc-sections) option. The
978 default behaviour (of not listing the sections that are removed)
979 can be restored by specifying --no-print-gc-sections on the command
980 line.
981 --print-output-format
983 Print the name of the default output format (perhaps influenced by
984 other command-line options). This is the string that would appear
985 in an "OUTPUT_FORMAT" linker script command.
986 --help
988 Print a summary of the command-line options on the standard output
989 and exit.
990 --target-help
992 Print a summary of all target specific options on the standard
993 output and exit.
994 -Map=mapfile
996 Print a link map to the file mapfile. See the description of the
997 -M option, above.
998 --no-keep-memory
1000 ld normally optimizes for speed over memory usage by caching the
1001 symbol tables of input files in memory. This option tells ld to
1002 instead optimize for memory usage, by rereading the symbol tables
1003 as necessary. This may be required if ld runs out of memory space
1004 while linking a large executable.
1005 --no-undefined
1007 -z defs
1008 Report unresolved symbol references from regular object files.
1009 This is done even if the linker is creating a non-symbolic shared
1010 library. The switch --[no-]allow-shlib-undefined controls the
1011 behaviour for reporting unresolved references found in shared
1012 libraries being linked in.
1013 --allow-multiple-definition
1015 -z muldefs
1016 Normally when a symbol is defined multiple times, the linker will
1017 report a fatal error. These options allow multiple definitions and
1018 the first definition will be used.
1019 --allow-shlib-undefined
1021 --no-allow-shlib-undefined
1022 Allows or disallows undefined symbols in shared libraries. This
1023 switch is similar to --no-undefined except that it determines the
1024 behaviour when the undefined symbols are in a shared library rather
1025 than a regular object file. It does not affect how undefined
1026 symbols in regular object files are handled.
1027 The default behaviour is to report errors for any undefined symbols
1029 referenced in shared libraries if the linker is being used to
1030 create an executable, but to allow them if the linker is being used
1031 to create a shared library.
1032 The reasons for allowing undefined symbol references in shared
1034 libraries specified at link time are that:
1035 · A shared library specified at link time may not be the same as
1037 the one that is available at load time, so the symbol might
1038 actually be resolvable at load time.
1039 · There are some operating systems, eg BeOS and HPPA, where
1041 undefined symbols in shared libraries are normal.
1042 The BeOS kernel for example patches shared libraries at load
1044 time to select whichever function is most appropriate for the
1045 current architecture. This is used, for example, to
1046 dynamically select an appropriate memset function.
1047 --no-undefined-version
1049 Normally when a symbol has an undefined version, the linker will
1050 ignore it. This option disallows symbols with undefined version and
1051 a fatal error will be issued instead.
1052 --default-symver
1054 Create and use a default symbol version (the soname) for
1055 unversioned exported symbols.
1056 --default-imported-symver
1058 Create and use a default symbol version (the soname) for
1059 unversioned imported symbols.
1060 --no-warn-mismatch
1062 Normally ld will give an error if you try to link together input
1063 files that are mismatched for some reason, perhaps because they
1064 have been compiled for different processors or for different
1065 endiannesses. This option tells ld that it should silently permit
1066 such possible errors. This option should only be used with care,
1067 in cases when you have taken some special action that ensures that
1068 the linker errors are inappropriate.
1069 --no-warn-search-mismatch
1071 Normally ld will give a warning if it finds an incompatible library
1072 during a library search. This option silences the warning.
1073 --no-whole-archive
1075 Turn off the effect of the --whole-archive option for subsequent
1076 archive files.
1077 --noinhibit-exec
1079 Retain the executable output file whenever it is still usable.
1080 Normally, the linker will not produce an output file if it
1081 encounters errors during the link process; it exits without writing
1082 an output file when it issues any error whatsoever.
1083 -nostdlib
1085 Only search library directories explicitly specified on the command
1086 line. Library directories specified in linker scripts (including
1087 linker scripts specified on the command line) are ignored.
1088 --oformat=output-format
1090 ld may be configured to support more than one kind of object file.
1091 If your ld is configured this way, you can use the --oformat option
1092 to specify the binary format for the output object file. Even when
1093 ld is configured to support alternative object formats, you don't
1094 usually need to specify this, as ld should be configured to produce
1095 as a default output format the most usual format on each machine.
1096 output-format is a text string, the name of a particular format
1097 supported by the BFD libraries. (You can list the available binary
1098 formats with objdump -i.) The script command "OUTPUT_FORMAT" can
1099 also specify the output format, but this option overrides it.
1100 -pie
1102 --pic-executable
1103 Create a position independent executable. This is currently only
1104 supported on ELF platforms. Position independent executables are
1105 similar to shared libraries in that they are relocated by the
1106 dynamic linker to the virtual address the OS chooses for them
1107 (which can vary between invocations). Like normal dynamically
1108 linked executables they can be executed and symbols defined in the
1109 executable cannot be overridden by shared libraries.
1110 -qmagic
1112 This option is ignored for Linux compatibility.
1113 -Qy This option is ignored for SVR4 compatibility.
1115 --relax
1117 --no-relax
1118 An option with machine dependent effects. This option is only
1119 supported on a few targets.
1120 On some platforms the --relax option performs target specific,
1122 global optimizations that become possible when the linker resolves
1123 addressing in the program, such as relaxing address modes,
1124 synthesizing new instructions, selecting shorter version of current
1125 instructions, and combining constant values.
1126 On some platforms these link time global optimizations may make
1128 symbolic debugging of the resulting executable impossible. This is
1129 known to be the case for the Matsushita MN10200 and MN10300 family
1130 of processors.
1131 On platforms where this is not supported, --relax is accepted, but
1133 ignored.
1134 On platforms where --relax is accepted the option --no-relax can be
1136 used to disable the feature.
1137 --retain-symbols-file=filename
1139 Retain only the symbols listed in the file filename, discarding all
1140 others. filename is simply a flat file, with one symbol name per
1141 line. This option is especially useful in environments (such as
1142 VxWorks) where a large global symbol table is accumulated
1143 gradually, to conserve run-time memory.
1144 --retain-symbols-file does not discard undefined symbols, or
1146 symbols needed for relocations.
1147 You may only specify --retain-symbols-file once in the command
1149 line. It overrides -s and -S.
1150 -rpath=dir
1152 Add a directory to the runtime library search path. This is used
1153 when linking an ELF executable with shared objects. All -rpath
1154 arguments are concatenated and passed to the runtime linker, which
1155 uses them to locate shared objects at runtime. The -rpath option
1156 is also used when locating shared objects which are needed by
1157 shared objects explicitly included in the link; see the description
1158 of the -rpath-link option. If -rpath is not used when linking an
1159 ELF executable, the contents of the environment variable
1160 "LD_RUN_PATH" will be used if it is defined.
1161 The -rpath option may also be used on SunOS. By default, on SunOS,
1163 the linker will form a runtime search patch out of all the -L
1164 options it is given. If a -rpath option is used, the runtime
1165 search path will be formed exclusively using the -rpath options,
1166 ignoring the -L options. This can be useful when using gcc, which
1167 adds many -L options which may be on NFS mounted file systems.
1168 For compatibility with other ELF linkers, if the -R option is
1170 followed by a directory name, rather than a file name, it is
1171 treated as the -rpath option.
1172 -rpath-link=dir
1174 When using ELF or SunOS, one shared library may require another.
1175 This happens when an "ld -shared" link includes a shared library as
1176 one of the input files.
1177 When the linker encounters such a dependency when doing a non-
1179 shared, non-relocatable link, it will automatically try to locate
1180 the required shared library and include it in the link, if it is
1181 not included explicitly. In such a case, the -rpath-link option
1182 specifies the first set of directories to search. The -rpath-link
1183 option may specify a sequence of directory names either by
1184 specifying a list of names separated by colons, or by appearing
1185 multiple times.
1186 This option should be used with caution as it overrides the search
1188 path that may have been hard compiled into a shared library. In
1189 such a case it is possible to use unintentionally a different
1190 search path than the runtime linker would do.
1191 The linker uses the following search paths to locate required
1193 shared libraries:
1194 1. Any directories specified by -rpath-link options.
1196 2. Any directories specified by -rpath options. The difference
1198 between -rpath and -rpath-link is that directories specified by
1199 -rpath options are included in the executable and used at
1200 runtime, whereas the -rpath-link option is only effective at
1201 link time. Searching -rpath in this way is only supported by
1202 native linkers and cross linkers which have been configured
1203 with the --with-sysroot option.
1204 3. On an ELF system, for native linkers, if the -rpath and
1206 -rpath-link options were not used, search the contents of the
1207 environment variable "LD_RUN_PATH".
1208 4. On SunOS, if the -rpath option was not used, search any
1210 directories specified using -L options.
1211 5. For a native linker, search the contents of the environment
1213 variable "LD_LIBRARY_PATH".
1214 6. For a native ELF linker, the directories in "DT_RUNPATH" or
1216 "DT_RPATH" of a shared library are searched for shared
1217 libraries needed by it. The "DT_RPATH" entries are ignored if
1218 "DT_RUNPATH" entries exist.
1219 7. The default directories, normally /lib and /usr/lib.
1221 8. For a native linker on an ELF system, if the file
1223 /etc/ld.so.conf exists, the list of directories found in that
1224 file.
1225 If the required shared library is not found, the linker will issue
1227 a warning and continue with the link.
1228 -shared
1230 -Bshareable
1231 Create a shared library. This is currently only supported on ELF,
1232 XCOFF and SunOS platforms. On SunOS, the linker will automatically
1233 create a shared library if the -e option is not used and there are
1234 undefined symbols in the link.
1235 --sort-common
1237 --sort-common=ascending
1238 --sort-common=descending
1239 This option tells ld to sort the common symbols by alignment in
1240 ascending or descending order when it places them in the
1241 appropriate output sections. The symbol alignments considered are
1242 sixteen-byte or larger, eight-byte, four-byte, two-byte, and one-
1243 byte. This is to prevent gaps between symbols due to alignment
1244 constraints. If no sorting order is specified, then descending
1245 order is assumed.
1246 --sort-section=name
1248 This option will apply "SORT_BY_NAME" to all wildcard section
1249 patterns in the linker script.
1250 --sort-section=alignment
1252 This option will apply "SORT_BY_ALIGNMENT" to all wildcard section
1253 patterns in the linker script.
1254 --split-by-file[=size]
1256 Similar to --split-by-reloc but creates a new output section for
1257 each input file when size is reached. size defaults to a size of 1
1258 if not given.
1259 --split-by-reloc[=count]
1261 Tries to creates extra sections in the output file so that no
1262 single output section in the file contains more than count
1263 relocations. This is useful when generating huge relocatable files
1264 for downloading into certain real time kernels with the COFF object
1265 file format; since COFF cannot represent more than 65535
1266 relocations in a single section. Note that this will fail to work
1267 with object file formats which do not support arbitrary sections.
1268 The linker will not split up individual input sections for
1269 redistribution, so if a single input section contains more than
1270 count relocations one output section will contain that many
1271 relocations. count defaults to a value of 32768.
1272 --stats
1274 Compute and display statistics about the operation of the linker,
1275 such as execution time and memory usage.
1276 --sysroot=directory
1278 Use directory as the location of the sysroot, overriding the
1279 configure-time default. This option is only supported by linkers
1280 that were configured using --with-sysroot.
1281 --traditional-format
1283 For some targets, the output of ld is different in some ways from
1284 the output of some existing linker. This switch requests ld to use
1285 the traditional format instead.
1286 For example, on SunOS, ld combines duplicate entries in the symbol
1288 string table. This can reduce the size of an output file with full
1289 debugging information by over 30 percent. Unfortunately, the SunOS
1290 "dbx" program can not read the resulting program ("gdb" has no
1291 trouble). The --traditional-format switch tells ld to not combine
1292 duplicate entries.
1293 --section-start=sectionname=org
1295 Locate a section in the output file at the absolute address given
1296 by org. You may use this option as many times as necessary to
1297 locate multiple sections in the command line. org must be a single
1298 hexadecimal integer; for compatibility with other linkers, you may
1299 omit the leading 0x usually associated with hexadecimal values.
1300 Note: there should be no white space between sectionname, the
1301 equals sign ("="), and org.
1302 -Tbss=org
1304 -Tdata=org
1305 -Ttext=org
1306 Same as --section-start, with ".bss", ".data" or ".text" as the
1307 sectionname.
1308 -Ttext-segment=org
1310 When creating an ELF executable or shared object, it will set the
1311 address of the first byte of the text segment.
1312 -Trodata-segment=org
1314 When creating an ELF executable or shared object for a target where
1315 the read-only data is in its own segment separate from the
1316 executable text, it will set the address of the first byte of the
1317 read-only data segment.
1318 -Tldata-segment=org
1320 When creating an ELF executable or shared object for x86-64 medium
1321 memory model, it will set the address of the first byte of the
1322 ldata segment.
1323 --unresolved-symbols=method
1325 Determine how to handle unresolved symbols. There are four
1326 possible values for method:
1327 ignore-all
1329 Do not report any unresolved symbols.
1330 report-all
1332 Report all unresolved symbols. This is the default.
1333 ignore-in-object-files
1335 Report unresolved symbols that are contained in shared
1336 libraries, but ignore them if they come from regular object
1337 files.
1338 ignore-in-shared-libs
1340 Report unresolved symbols that come from regular object files,
1341 but ignore them if they come from shared libraries. This can
1342 be useful when creating a dynamic binary and it is known that
1343 all the shared libraries that it should be referencing are
1344 included on the linker's command line.
1345 The behaviour for shared libraries on their own can also be
1347 controlled by the --[no-]allow-shlib-undefined option.
1348 Normally the linker will generate an error message for each
1350 reported unresolved symbol but the option --warn-unresolved-symbols
1351 can change this to a warning.
1352 --dll-verbose
1354 --verbose[=NUMBER]
1355 Display the version number for ld and list the linker emulations
1356 supported. Display which input files can and cannot be opened.
1357 Display the linker script being used by the linker. If the optional
1358 NUMBER argument > 1, plugin symbol status will also be displayed.
1359 --version-script=version-scriptfile
1361 Specify the name of a version script to the linker. This is
1362 typically used when creating shared libraries to specify additional
1363 information about the version hierarchy for the library being
1364 created. This option is only fully supported on ELF platforms
1365 which support shared libraries; see VERSION. It is partially
1366 supported on PE platforms, which can use version scripts to filter
1367 symbol visibility in auto-export mode: any symbols marked local in
1368 the version script will not be exported.
1369 --warn-common
1371 Warn when a common symbol is combined with another common symbol or
1372 with a symbol definition. Unix linkers allow this somewhat sloppy
1373 practice, but linkers on some other operating systems do not. This
1374 option allows you to find potential problems from combining global
1375 symbols. Unfortunately, some C libraries use this practice, so you
1376 may get some warnings about symbols in the libraries as well as in
1377 your programs.
1378 There are three kinds of global symbols, illustrated here by C
1380 examples:
1381 int i = 1;
1383 A definition, which goes in the initialized data section of the
1384 output file.
1385 extern int i;
1387 An undefined reference, which does not allocate space. There
1388 must be either a definition or a common symbol for the variable
1389 somewhere.
1390 int i;
1392 A common symbol. If there are only (one or more) common
1393 symbols for a variable, it goes in the uninitialized data area
1394 of the output file. The linker merges multiple common symbols
1395 for the same variable into a single symbol. If they are of
1396 different sizes, it picks the largest size. The linker turns a
1397 common symbol into a declaration, if there is a definition of
1398 the same variable.
1399 The --warn-common option can produce five kinds of warnings. Each
1401 warning consists of a pair of lines: the first describes the symbol
1402 just encountered, and the second describes the previous symbol
1403 encountered with the same name. One or both of the two symbols
1404 will be a common symbol.
1405 1. Turning a common symbol into a reference, because there is
1407 already a definition for the symbol.
1408 <file>(<section>): warning: common of `<symbol>'
1410 overridden by definition
1411 <file>(<section>): warning: defined here
1412 2. Turning a common symbol into a reference, because a later
1414 definition for the symbol is encountered. This is the same as
1415 the previous case, except that the symbols are encountered in a
1416 different order.
1417 <file>(<section>): warning: definition of `<symbol>'
1419 overriding common
1420 <file>(<section>): warning: common is here
1421 3. Merging a common symbol with a previous same-sized common
1423 symbol.
1424 <file>(<section>): warning: multiple common
1426 of `<symbol>'
1427 <file>(<section>): warning: previous common is here
1428 4. Merging a common symbol with a previous larger common symbol.
1430 <file>(<section>): warning: common of `<symbol>'
1432 overridden by larger common
1433 <file>(<section>): warning: larger common is here
1434 5. Merging a common symbol with a previous smaller common symbol.
1436 This is the same as the previous case, except that the symbols
1437 are encountered in a different order.
1438 <file>(<section>): warning: common of `<symbol>'
1440 overriding smaller common
1441 <file>(<section>): warning: smaller common is here
1442 --warn-constructors
1444 Warn if any global constructors are used. This is only useful for
1445 a few object file formats. For formats like COFF or ELF, the
1446 linker can not detect the use of global constructors.
1447 --warn-multiple-gp
1449 Warn if multiple global pointer values are required in the output
1450 file. This is only meaningful for certain processors, such as the
1451 Alpha. Specifically, some processors put large-valued constants in
1452 a special section. A special register (the global pointer) points
1453 into the middle of this section, so that constants can be loaded
1454 efficiently via a base-register relative addressing mode. Since
1455 the offset in base-register relative mode is fixed and relatively
1456 small (e.g., 16 bits), this limits the maximum size of the constant
1457 pool. Thus, in large programs, it is often necessary to use
1458 multiple global pointer values in order to be able to address all
1459 possible constants. This option causes a warning to be issued
1460 whenever this case occurs.
1461 --warn-once
1463 Only warn once for each undefined symbol, rather than once per
1464 module which refers to it.
1465 --warn-section-align
1467 Warn if the address of an output section is changed because of
1468 alignment. Typically, the alignment will be set by an input
1469 section. The address will only be changed if it not explicitly
1470 specified; that is, if the "SECTIONS" command does not specify a
1471 start address for the section.
1472 --warn-shared-textrel
1474 Warn if the linker adds a DT_TEXTREL to a shared object.
1475 --warn-alternate-em
1477 Warn if an object has alternate ELF machine code.
1478 --warn-unresolved-symbols
1480 If the linker is going to report an unresolved symbol (see the
1481 option --unresolved-symbols) it will normally generate an error.
1482 This option makes it generate a warning instead.
1483 --error-unresolved-symbols
1485 This restores the linker's default behaviour of generating errors
1486 when it is reporting unresolved symbols.
1487 --whole-archive
1489 For each archive mentioned on the command line after the
1490 --whole-archive option, include every object file in the archive in
1491 the link, rather than searching the archive for the required object
1492 files. This is normally used to turn an archive file into a shared
1493 library, forcing every object to be included in the resulting
1494 shared library. This option may be used more than once.
1495 Two notes when using this option from gcc: First, gcc doesn't know
1497 about this option, so you have to use -Wl,-whole-archive. Second,
1498 don't forget to use -Wl,-no-whole-archive after your list of
1499 archives, because gcc will add its own list of archives to your
1500 link and you may not want this flag to affect those as well.
1501 --wrap=symbol
1503 Use a wrapper function for symbol. Any undefined reference to
1504 symbol will be resolved to "__wrap_symbol". Any undefined
1505 reference to "__real_symbol" will be resolved to symbol.
1506 This can be used to provide a wrapper for a system function. The
1508 wrapper function should be called "__wrap_symbol". If it wishes to
1509 call the system function, it should call "__real_symbol".
1510 Here is a trivial example:
1512 void *
1514 __wrap_malloc (size_t c)
1515 {
1516 printf ("malloc called with %zu\n", c);
1517 return __real_malloc (c);
1518 }
1519 If you link other code with this file using --wrap malloc, then all
1521 calls to "malloc" will call the function "__wrap_malloc" instead.
1522 The call to "__real_malloc" in "__wrap_malloc" will call the real
1523 "malloc" function.
1524 You may wish to provide a "__real_malloc" function as well, so that
1526 links without the --wrap option will succeed. If you do this, you
1527 should not put the definition of "__real_malloc" in the same file
1528 as "__wrap_malloc"; if you do, the assembler may resolve the call
1529 before the linker has a chance to wrap it to "malloc".
1530 --eh-frame-hdr
1532 Request creation of ".eh_frame_hdr" section and ELF
1533 "PT_GNU_EH_FRAME" segment header.
1534 --no-ld-generated-unwind-info
1536 Request creation of ".eh_frame" unwind info for linker generated
1537 code sections like PLT. This option is on by default if linker
1538 generated unwind info is supported.
1539 --enable-new-dtags
1541 --disable-new-dtags
1542 This linker can create the new dynamic tags in ELF. But the older
1543 ELF systems may not understand them. If you specify
1544 --enable-new-dtags, the new dynamic tags will be created as needed
1545 and older dynamic tags will be omitted. If you specify
1546 --disable-new-dtags, no new dynamic tags will be created. By
1547 default, the new dynamic tags are not created. Note that those
1548 options are only available for ELF systems.
1549 --hash-size=number
1551 Set the default size of the linker's hash tables to a prime number
1552 close to number. Increasing this value can reduce the length of
1553 time it takes the linker to perform its tasks, at the expense of
1554 increasing the linker's memory requirements. Similarly reducing
1555 this value can reduce the memory requirements at the expense of
1556 speed.
1557 --hash-style=style
1559 Set the type of linker's hash table(s). style can be either "sysv"
1560 for classic ELF ".hash" section, "gnu" for new style GNU
1561 ".gnu.hash" section or "both" for both the classic ELF ".hash" and
1562 new style GNU ".gnu.hash" hash tables. The default is "sysv".
1563 --reduce-memory-overheads
1565 This option reduces memory requirements at ld runtime, at the
1566 expense of linking speed. This was introduced to select the old
1567 O(n^2) algorithm for link map file generation, rather than the new
1568 O(n) algorithm which uses about 40% more memory for symbol storage.
1569 Another effect of the switch is to set the default hash table size
1571 to 1021, which again saves memory at the cost of lengthening the
1572 linker's run time. This is not done however if the --hash-size
1573 switch has been used.
1574 The --reduce-memory-overheads switch may be also be used to enable
1576 other tradeoffs in future versions of the linker.
1577 --build-id
1579 --build-id=style
1580 Request creation of ".note.gnu.build-id" ELF note section. The
1581 contents of the note are unique bits identifying this linked file.
1582 style can be "uuid" to use 128 random bits, "sha1" to use a 160-bit
1583 SHA1 hash on the normative parts of the output contents, "md5" to
1584 use a 128-bit MD5 hash on the normative parts of the output
1585 contents, or "0xhexstring" to use a chosen bit string specified as
1586 an even number of hexadecimal digits ("-" and ":" characters
1587 between digit pairs are ignored). If style is omitted, "sha1" is
1588 used.
1589 The "md5" and "sha1" styles produces an identifier that is always
1591 the same in an identical output file, but will be unique among all
1592 nonidentical output files. It is not intended to be compared as a
1593 checksum for the file's contents. A linked file may be changed
1594 later by other tools, but the build ID bit string identifying the
1595 original linked file does not change.
1596 Passing "none" for style disables the setting from any "--build-id"
1598 options earlier on the command line.
1599 The i386 PE linker supports the -shared option, which causes the output
1601 to be a dynamically linked library (DLL) instead of a normal
1602 executable. You should name the output "*.dll" when you use this
1603 option. In addition, the linker fully supports the standard "*.def"
1604 files, which may be specified on the linker command line like an object
1605 file (in fact, it should precede archives it exports symbols from, to
1606 ensure that they get linked in, just like a normal object file).
1607 In addition to the options common to all targets, the i386 PE linker
1609 support additional command line options that are specific to the i386
1610 PE target. Options that take values may be separated from their values
1611 by either a space or an equals sign.
1612 --add-stdcall-alias
1614 If given, symbols with a stdcall suffix (@nn) will be exported as-
1615 is and also with the suffix stripped. [This option is specific to
1616 the i386 PE targeted port of the linker]
1617 --base-file file
1619 Use file as the name of a file in which to save the base addresses
1620 of all the relocations needed for generating DLLs with dlltool.
1621 [This is an i386 PE specific option]
1622 --dll
1624 Create a DLL instead of a regular executable. You may also use
1625 -shared or specify a "LIBRARY" in a given ".def" file. [This
1626 option is specific to the i386 PE targeted port of the linker]
1627 --enable-long-section-names
1629 --disable-long-section-names
1630 The PE variants of the Coff object format add an extension that
1631 permits the use of section names longer than eight characters, the
1632 normal limit for Coff. By default, these names are only allowed in
1633 object files, as fully-linked executable images do not carry the
1634 Coff string table required to support the longer names. As a GNU
1635 extension, it is possible to allow their use in executable images
1636 as well, or to (probably pointlessly!) disallow it in object
1637 files, by using these two options. Executable images generated
1638 with these long section names are slightly non-standard, carrying
1639 as they do a string table, and may generate confusing output when
1640 examined with non-GNU PE-aware tools, such as file viewers and
1641 dumpers. However, GDB relies on the use of PE long section names
1642 to find Dwarf-2 debug information sections in an executable image
1643 at runtime, and so if neither option is specified on the command-
1644 line, ld will enable long section names, overriding the default and
1645 technically correct behaviour, when it finds the presence of debug
1646 information while linking an executable image and not stripping
1647 symbols. [This option is valid for all PE targeted ports of the
1648 linker]
1649 --enable-stdcall-fixup
1651 --disable-stdcall-fixup
1652 If the link finds a symbol that it cannot resolve, it will attempt
1653 to do "fuzzy linking" by looking for another defined symbol that
1654 differs only in the format of the symbol name (cdecl vs stdcall)
1655 and will resolve that symbol by linking to the match. For example,
1656 the undefined symbol "_foo" might be linked to the function
1657 "_foo@12", or the undefined symbol "_bar@16" might be linked to the
1658 function "_bar". When the linker does this, it prints a warning,
1659 since it normally should have failed to link, but sometimes import
1660 libraries generated from third-party dlls may need this feature to
1661 be usable. If you specify --enable-stdcall-fixup, this feature is
1662 fully enabled and warnings are not printed. If you specify
1663 --disable-stdcall-fixup, this feature is disabled and such
1664 mismatches are considered to be errors. [This option is specific
1665 to the i386 PE targeted port of the linker]
1666 --leading-underscore
1668 --no-leading-underscore
1669 For most targets default symbol-prefix is an underscore and is
1670 defined in target's description. By this option it is possible to
1671 disable/enable the default underscore symbol-prefix.
1672 --export-all-symbols
1674 If given, all global symbols in the objects used to build a DLL
1675 will be exported by the DLL. Note that this is the default if
1676 there otherwise wouldn't be any exported symbols. When symbols are
1677 explicitly exported via DEF files or implicitly exported via
1678 function attributes, the default is to not export anything else
1679 unless this option is given. Note that the symbols "DllMain@12",
1680 "DllEntryPoint@0", "DllMainCRTStartup@12", and "impure_ptr" will
1681 not be automatically exported. Also, symbols imported from other
1682 DLLs will not be re-exported, nor will symbols specifying the DLL's
1683 internal layout such as those beginning with "_head_" or ending
1684 with "_iname". In addition, no symbols from "libgcc", "libstd++",
1685 "libmingw32", or "crtX.o" will be exported. Symbols whose names
1686 begin with "__rtti_" or "__builtin_" will not be exported, to help
1687 with C++ DLLs. Finally, there is an extensive list of cygwin-
1688 private symbols that are not exported (obviously, this applies on
1689 when building DLLs for cygwin targets). These cygwin-excludes are:
1690 "_cygwin_dll_entry@12", "_cygwin_crt0_common@8",
1691 "_cygwin_noncygwin_dll_entry@12", "_fmode", "_impure_ptr",
1692 "cygwin_attach_dll", "cygwin_premain0", "cygwin_premain1",
1693 "cygwin_premain2", "cygwin_premain3", and "environ". [This option
1694 is specific to the i386 PE targeted port of the linker]
1695 --exclude-symbols symbol,symbol,...
1697 Specifies a list of symbols which should not be automatically
1698 exported. The symbol names may be delimited by commas or colons.
1699 [This option is specific to the i386 PE targeted port of the
1700 linker]
1701 --exclude-all-symbols
1703 Specifies no symbols should be automatically exported. [This
1704 option is specific to the i386 PE targeted port of the linker]
1705 --file-alignment
1707 Specify the file alignment. Sections in the file will always begin
1708 at file offsets which are multiples of this number. This defaults
1709 to 512. [This option is specific to the i386 PE targeted port of
1710 the linker]
1711 --heap reserve
1713 --heap reserve,commit
1714 Specify the number of bytes of memory to reserve (and optionally
1715 commit) to be used as heap for this program. The default is 1MB
1716 reserved, 4K committed. [This option is specific to the i386 PE
1717 targeted port of the linker]
1718 --image-base value
1720 Use value as the base address of your program or dll. This is the
1721 lowest memory location that will be used when your program or dll
1722 is loaded. To reduce the need to relocate and improve performance
1723 of your dlls, each should have a unique base address and not
1724 overlap any other dlls. The default is 0x400000 for executables,
1725 and 0x10000000 for dlls. [This option is specific to the i386 PE
1726 targeted port of the linker]
1727 --kill-at
1729 If given, the stdcall suffixes (@nn) will be stripped from symbols
1730 before they are exported. [This option is specific to the i386 PE
1731 targeted port of the linker]
1732 --large-address-aware
1734 If given, the appropriate bit in the "Characteristics" field of the
1735 COFF header is set to indicate that this executable supports
1736 virtual addresses greater than 2 gigabytes. This should be used in
1737 conjunction with the /3GB or /USERVA=value megabytes switch in the
1738 "[operating systems]" section of the BOOT.INI. Otherwise, this bit
1739 has no effect. [This option is specific to PE targeted ports of
1740 the linker]
1741 --disable-large-address-aware
1743 Reverts the effect of a previous --large-address-aware option.
1744 This is useful if --large-address-aware is always set by the
1745 compiler driver (e.g. Cygwin gcc) and the executable does not
1746 support virtual addresses greater than 2 gigabytes. [This option
1747 is specific to PE targeted ports of the linker]
1748 --major-image-version value
1750 Sets the major number of the "image version". Defaults to 1.
1751 [This option is specific to the i386 PE targeted port of the
1752 linker]
1753 --major-os-version value
1755 Sets the major number of the "os version". Defaults to 4. [This
1756 option is specific to the i386 PE targeted port of the linker]
1757 --major-subsystem-version value
1759 Sets the major number of the "subsystem version". Defaults to 4.
1760 [This option is specific to the i386 PE targeted port of the
1761 linker]
1762 --minor-image-version value
1764 Sets the minor number of the "image version". Defaults to 0.
1765 [This option is specific to the i386 PE targeted port of the
1766 linker]
1767 --minor-os-version value
1769 Sets the minor number of the "os version". Defaults to 0. [This
1770 option is specific to the i386 PE targeted port of the linker]
1771 --minor-subsystem-version value
1773 Sets the minor number of the "subsystem version". Defaults to 0.
1774 [This option is specific to the i386 PE targeted port of the
1775 linker]
1776 --output-def file
1778 The linker will create the file file which will contain a DEF file
1779 corresponding to the DLL the linker is generating. This DEF file
1780 (which should be called "*.def") may be used to create an import
1781 library with "dlltool" or may be used as a reference to
1782 automatically or implicitly exported symbols. [This option is
1783 specific to the i386 PE targeted port of the linker]
1784 --out-implib file
1786 The linker will create the file file which will contain an import
1787 lib corresponding to the DLL the linker is generating. This import
1788 lib (which should be called "*.dll.a" or "*.a" may be used to link
1789 clients against the generated DLL; this behaviour makes it possible
1790 to skip a separate "dlltool" import library creation step. [This
1791 option is specific to the i386 PE targeted port of the linker]
1792 --enable-auto-image-base
1794 Automatically choose the image base for DLLs, unless one is
1795 specified using the "--image-base" argument. By using a hash
1796 generated from the dllname to create unique image bases for each
1797 DLL, in-memory collisions and relocations which can delay program
1798 execution are avoided. [This option is specific to the i386 PE
1799 targeted port of the linker]
1800 --disable-auto-image-base
1802 Do not automatically generate a unique image base. If there is no
1803 user-specified image base ("--image-base") then use the platform
1804 default. [This option is specific to the i386 PE targeted port of
1805 the linker]
1806 --dll-search-prefix string
1808 When linking dynamically to a dll without an import library, search
1809 for "<string><basename>.dll" in preference to "lib<basename>.dll".
1810 This behaviour allows easy distinction between DLLs built for the
1811 various "subplatforms": native, cygwin, uwin, pw, etc. For
1812 instance, cygwin DLLs typically use "--dll-search-prefix=cyg".
1813 [This option is specific to the i386 PE targeted port of the
1814 linker]
1815 --enable-auto-import
1817 Do sophisticated linking of "_symbol" to "__imp__symbol" for DATA
1818 imports from DLLs, and create the necessary thunking symbols when
1819 building the import libraries with those DATA exports. Note: Use of
1820 the 'auto-import' extension will cause the text section of the
1821 image file to be made writable. This does not conform to the PE-
1822 COFF format specification published by Microsoft.
1823 Note - use of the 'auto-import' extension will also cause read only
1825 data which would normally be placed into the .rdata section to be
1826 placed into the .data section instead. This is in order to work
1827 around a problem with consts that is described here:
1828 http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
1829 Using 'auto-import' generally will 'just work' -- but sometimes you
1831 may see this message:
1832 "variable '<var>' can't be auto-imported. Please read the
1834 documentation for ld's "--enable-auto-import" for details."
1835 This message occurs when some (sub)expression accesses an address
1837 ultimately given by the sum of two constants (Win32 import tables
1838 only allow one). Instances where this may occur include accesses
1839 to member fields of struct variables imported from a DLL, as well
1840 as using a constant index into an array variable imported from a
1841 DLL. Any multiword variable (arrays, structs, long long, etc) may
1842 trigger this error condition. However, regardless of the exact
1843 data type of the offending exported variable, ld will always detect
1844 it, issue the warning, and exit.
1845 There are several ways to address this difficulty, regardless of
1847 the data type of the exported variable:
1848 One way is to use --enable-runtime-pseudo-reloc switch. This leaves
1850 the task of adjusting references in your client code for runtime
1851 environment, so this method works only when runtime environment
1852 supports this feature.
1853 A second solution is to force one of the 'constants' to be a
1855 variable -- that is, unknown and un-optimizable at compile time.
1856 For arrays, there are two possibilities: a) make the indexee (the
1857 array's address) a variable, or b) make the 'constant' index a
1858 variable. Thus:
1859 extern type extern_array[];
1861 extern_array[1] -->
1862 { volatile type *t=extern_array; t[1] }
1863 or
1865 extern type extern_array[];
1867 extern_array[1] -->
1868 { volatile int t=1; extern_array[t] }
1869 For structs (and most other multiword data types) the only option
1871 is to make the struct itself (or the long long, or the ...)
1872 variable:
1873 extern struct s extern_struct;
1875 extern_struct.field -->
1876 { volatile struct s *t=&extern_struct; t->field }
1877 or
1879 extern long long extern_ll;
1881 extern_ll -->
1882 { volatile long long * local_ll=&extern_ll; *local_ll }
1883 A third method of dealing with this difficulty is to abandon
1885 'auto-import' for the offending symbol and mark it with
1886 "__declspec(dllimport)". However, in practice that requires using
1887 compile-time #defines to indicate whether you are building a DLL,
1888 building client code that will link to the DLL, or merely
1889 building/linking to a static library. In making the choice
1890 between the various methods of resolving the 'direct address with
1891 constant offset' problem, you should consider typical real-world
1892 usage:
1893 Original:
1895 --foo.h
1897 extern int arr[];
1898 --foo.c
1899 #include "foo.h"
1900 void main(int argc, char **argv){
1901 printf("%d\n",arr[1]);
1902 }
1903 Solution 1:
1905 --foo.h
1907 extern int arr[];
1908 --foo.c
1909 #include "foo.h"
1910 void main(int argc, char **argv){
1911 /* This workaround is for win32 and cygwin; do not "optimize" */
1912 volatile int *parr = arr;
1913 printf("%d\n",parr[1]);
1914 }
1915 Solution 2:
1917 --foo.h
1919 /* Note: auto-export is assumed (no __declspec(dllexport)) */
1920 #if (defined(_WIN32) || defined(__CYGWIN__)) && \
1921 !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
1922 #define FOO_IMPORT __declspec(dllimport)
1923 #else
1924 #define FOO_IMPORT
1925 #endif
1926 extern FOO_IMPORT int arr[];
1927 --foo.c
1928 #include "foo.h"
1929 void main(int argc, char **argv){
1930 printf("%d\n",arr[1]);
1931 }
1932 A fourth way to avoid this problem is to re-code your library to
1934 use a functional interface rather than a data interface for the
1935 offending variables (e.g. set_foo() and get_foo() accessor
1936 functions). [This option is specific to the i386 PE targeted port
1937 of the linker]
1938 --disable-auto-import
1940 Do not attempt to do sophisticated linking of "_symbol" to
1941 "__imp__symbol" for DATA imports from DLLs. [This option is
1942 specific to the i386 PE targeted port of the linker]
1943 --enable-runtime-pseudo-reloc
1945 If your code contains expressions described in --enable-auto-import
1946 section, that is, DATA imports from DLL with non-zero offset, this
1947 switch will create a vector of 'runtime pseudo relocations' which
1948 can be used by runtime environment to adjust references to such
1949 data in your client code. [This option is specific to the i386 PE
1950 targeted port of the linker]
1951 --disable-runtime-pseudo-reloc
1953 Do not create pseudo relocations for non-zero offset DATA imports
1954 from DLLs. [This option is specific to the i386 PE targeted port
1955 of the linker]
1956 --enable-extra-pe-debug
1958 Show additional debug info related to auto-import symbol thunking.
1959 [This option is specific to the i386 PE targeted port of the
1960 linker]
1961 --section-alignment
1963 Sets the section alignment. Sections in memory will always begin
1964 at addresses which are a multiple of this number. Defaults to
1965 0x1000. [This option is specific to the i386 PE targeted port of
1966 the linker]
1967 --stack reserve
1969 --stack reserve,commit
1970 Specify the number of bytes of memory to reserve (and optionally
1971 commit) to be used as stack for this program. The default is 2MB
1972 reserved, 4K committed. [This option is specific to the i386 PE
1973 targeted port of the linker]
1974 --subsystem which
1976 --subsystem which:major
1977 --subsystem which:major.minor
1978 Specifies the subsystem under which your program will execute. The
1979 legal values for which are "native", "windows", "console", "posix",
1980 and "xbox". You may optionally set the subsystem version also.
1981 Numeric values are also accepted for which. [This option is
1982 specific to the i386 PE targeted port of the linker]
1983 The following options set flags in the "DllCharacteristics" field
1985 of the PE file header: [These options are specific to PE targeted
1986 ports of the linker]
1987 --dynamicbase
1989 The image base address may be relocated using address space layout
1990 randomization (ASLR). This feature was introduced with MS Windows
1991 Vista for i386 PE targets.
1992 --forceinteg
1994 Code integrity checks are enforced.
1995 --nxcompat
1997 The image is compatible with the Data Execution Prevention. This
1998 feature was introduced with MS Windows XP SP2 for i386 PE targets.
1999 --no-isolation
2001 Although the image understands isolation, do not isolate the image.
2002 --no-seh
2004 The image does not use SEH. No SE handler may be called from this
2005 image.
2006 --no-bind
2008 Do not bind this image.
2009 --wdmdriver
2011 The driver uses the MS Windows Driver Model.
2012 --tsaware
2014 The image is Terminal Server aware.
2015 --insert-timestamp
2017 Insert a real timestamp into the image, rather than the default
2018 value of zero. This will result in a slightly different results
2019 with each invocation, which could be helpful for distributing
2020 unique images.
2021 The C6X uClinux target uses a binary format called DSBT to support
2023 shared libraries. Each shared library in the system needs to have a
2024 unique index; all executables use an index of 0.
2025 --dsbt-size size
2027 This option sets the number of entires in the DSBT of the current
2028 executable or shared library to size. The default is to create a
2029 table with 64 entries.
2030 --dsbt-index index
2032 This option sets the DSBT index of the current executable or shared
2033 library to index. The default is 0, which is appropriate for
2034 generating executables. If a shared library is generated with a
2035 DSBT index of 0, the "R_C6000_DSBT_INDEX" relocs are copied into
2036 the output file.
2037 The --no-merge-exidx-entries switch disables the merging of
2039 adjacent exidx entries in frame unwind info.
2040 The 68HC11 and 68HC12 linkers support specific options to control the
2042 memory bank switching mapping and trampoline code generation.
2043 --no-trampoline
2045 This option disables the generation of trampoline. By default a
2046 trampoline is generated for each far function which is called using
2047 a "jsr" instruction (this happens when a pointer to a far function
2048 is taken).
2049 --bank-window name
2051 This option indicates to the linker the name of the memory region
2052 in the MEMORY specification that describes the memory bank window.
2053 The definition of such region is then used by the linker to compute
2054 paging and addresses within the memory window.
2055 The following options are supported to control handling of GOT
2057 generation when linking for 68K targets.
2058 --got=type
2060 This option tells the linker which GOT generation scheme to use.
2061 type should be one of single, negative, multigot or target. For
2062 more information refer to the Info entry for ld.
2063 The following options are supported to control microMIPS instruction
2065 generation when linking for MIPS targets.
2066 --insn32
2068 --no-insn32
2069 These options control the choice of microMIPS instructions used in
2070 code generated by the linker, such as that in the PLT or lazy
2071 binding stubs, or in relaxation. If --insn32 is used, then the
2072 linker only uses 32-bit instruction encodings. By default or if
2073 --no-insn32 is used, all instruction encodings are used, including
2074 16-bit ones where possible.
2075
2077 You can change the behaviour of ld with the environment variables
2078 "GNUTARGET", "LDEMULATION" and "COLLECT_NO_DEMANGLE".
2079 "GNUTARGET" determines the input-file object format if you don't use -b
2081 (or its synonym --format). Its value should be one of the BFD names
2082 for an input format. If there is no "GNUTARGET" in the environment, ld
2083 uses the natural format of the target. If "GNUTARGET" is set to
2084 "default" then BFD attempts to discover the input format by examining
2085 binary input files; this method often succeeds, but there are potential
2086 ambiguities, since there is no method of ensuring that the magic number
2087 used to specify object-file formats is unique. However, the
2088 configuration procedure for BFD on each system places the conventional
2089 format for that system first in the search-list, so ambiguities are
2090 resolved in favor of convention.
2091 "LDEMULATION" determines the default emulation if you don't use the -m
2093 option. The emulation can affect various aspects of linker behaviour,
2094 particularly the default linker script. You can list the available
2095 emulations with the --verbose or -V options. If the -m option is not
2096 used, and the "LDEMULATION" environment variable is not defined, the
2097 default emulation depends upon how the linker was configured.
2098 Normally, the linker will default to demangling symbols. However, if
2100 "COLLECT_NO_DEMANGLE" is set in the environment, then it will default
2101 to not demangling symbols. This environment variable is used in a
2102 similar fashion by the "gcc" linker wrapper program. The default may
2103 be overridden by the --demangle and --no-demangle options.
2104
2106 ar(1), nm(1), objcopy(1), objdump(1), readelf(1) and the Info entries
2107 for binutils and ld.
2108
2110 Copyright (c) 1991-2013 Free Software Foundation, Inc.
2111 Permission is granted to copy, distribute and/or modify this document
2113 under the terms of the GNU Free Documentation License, Version 1.3 or
2114 any later version published by the Free Software Foundation; with no
2115 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
2116 Texts. A copy of the license is included in the section entitled "GNU
2117 Free Documentation License".
2118binutils-2.24 2020-01-29 LD(1)