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,--startgroup foo.o bar.o -Wl,--endgroup
111 This is important, because otherwise the compiler driver program may
113 silently drop the linker options, resulting in a bad link.
114 Here is a table of the generic command line switches accepted by the
116 GNU linker:
117 @file
119 Read command-line options from file. The options read are inserted
120 in place of the original @file option. If file does not exist, or
121 cannot be read, then the option will be treated literally, and not
122 removed.
123 Options in file are separated by whitespace. A whitespace
125 character may be included in an option by surrounding the entire
126 option in either single or double quotes. Any character (including
127 a backslash) may be included by prefixing the character to be
128 included with a backslash. The file may itself contain additional
129 @file options; any such options will be processed recursively.
130 -akeyword
132 This option is supported for HP/UX compatibility. The keyword
133 argument must be one of the strings archive, shared, or default.
134 -aarchive is functionally equivalent to -Bstatic, and the other two
135 keywords are functionally equivalent to -Bdynamic. This option may
136 be used any number of times.
137 -Aarchitecture
139 --architecture=architecture
140 In the current release of ld, this option is useful only for the
141 Intel 960 family of architectures. In that ld configuration, the
142 architecture argument identifies the particular architecture in the
143 960 family, enabling some safeguards and modifying the archive-
144 library search path.
145 Future releases of ld may support similar functionality for other
147 architecture families.
148 -b input-format
150 --format=input-format
151 ld may be configured to support more than one kind of object file.
152 If your ld is configured this way, you can use the -b option to
153 specify the binary format for input object files that follow this
154 option on the command line. Even when ld is configured to support
155 alternative object formats, you don't usually need to specify this,
156 as ld should be configured to expect as a default input format the
157 most usual format on each machine. input-format is a text string,
158 the name of a particular format supported by the BFD libraries.
159 (You can list the available binary formats with objdump -i.)
160 You may want to use this option if you are linking files with an
162 unusual binary format. You can also use -b to switch formats
163 explicitly (when linking object files of different formats), by
164 including -b input-format before each group of object files in a
165 particular format.
166 The default format is taken from the environment variable
168 "GNUTARGET".
169 You can also define the input format from a script, using the
171 command "TARGET";
172 -c MRI-commandfile
174 --mri-script=MRI-commandfile
175 For compatibility with linkers produced by MRI, ld accepts script
176 files written in an alternate, restricted command language,
177 described in the MRI Compatible Script Files section of GNU ld
178 documentation. Introduce MRI script files with the option -c; use
179 the -T option to run linker scripts written in the general-purpose
180 ld scripting language. If MRI-cmdfile does not exist, ld looks for
181 it in the directories specified by any -L options.
182 -d
184 -dc
185 -dp These three options are equivalent; multiple forms are supported
186 for compatibility with other linkers. They assign space to common
187 symbols even if a relocatable output file is specified (with -r).
188 The script command "FORCE_COMMON_ALLOCATION" has the same effect.
189 -e entry
191 --entry=entry
192 Use entry as the explicit symbol for beginning execution of your
193 program, rather than the default entry point. If there is no
194 symbol named entry, the linker will try to parse entry as a number,
195 and use that as the entry address (the number will be interpreted
196 in base 10; you may use a leading 0x for base 16, or a leading 0
197 for base 8).
198 --exclude-libs lib,lib,...
200 Specifies a list of archive libraries from which symbols should not
201 be automatically exported. The library names may be delimited by
202 commas or colons. Specifying "--exclude-libs ALL" excludes symbols
203 in all archive libraries from automatic export. This option is
204 available only for the i386 PE targeted port of the linker and for
205 ELF targeted ports. For i386 PE, symbols explicitly listed in a
206 .def file are still exported, regardless of this option. For ELF
207 targeted ports, symbols affected by this option will be treated as
208 hidden.
209 -E
211 --export-dynamic
212 When creating a dynamically linked executable, add all symbols to
213 the dynamic symbol table. The dynamic symbol table is the set of
214 symbols which are visible from dynamic objects at run time.
215 If you do not use this option, the dynamic symbol table will
217 normally contain only those symbols which are referenced by some
218 dynamic object mentioned in the link.
219 If you use "dlopen" to load a dynamic object which needs to refer
221 back to the symbols defined by the program, rather than some other
222 dynamic object, then you will probably need to use this option when
223 linking the program itself.
224 You can also use the dynamic list to control what symbols should be
226 added to the dynamic symbol table if the output format supports it.
227 See the description of --dynamic-list.
228 -EB Link big-endian objects. This affects the default output format.
230 -EL Link little-endian objects. This affects the default output
232 format.
233 -f
235 --auxiliary name
236 When creating an ELF shared object, set the internal DT_AUXILIARY
237 field to the specified name. This tells the dynamic linker that
238 the symbol table of the shared object should be used as an
239 auxiliary filter on the symbol table of the shared object name.
240 If you later link a program against this filter object, then, when
242 you run the program, the dynamic linker will see the DT_AUXILIARY
243 field. If the dynamic linker resolves any symbols from the filter
244 object, it will first check whether there is a definition in the
245 shared object name. If there is one, it will be used instead of
246 the definition in the filter object. The shared object name need
247 not exist. Thus the shared object name may be used to provide an
248 alternative implementation of certain functions, perhaps for
249 debugging or for machine specific performance.
250 This option may be specified more than once. The DT_AUXILIARY
252 entries will be created in the order in which they appear on the
253 command line.
254 -F name
256 --filter name
257 When creating an ELF shared object, set the internal DT_FILTER
258 field to the specified name. This tells the dynamic linker that
259 the symbol table of the shared object which is being created should
260 be used as a filter on the symbol table of the shared object name.
261 If you later link a program against this filter object, then, when
263 you run the program, the dynamic linker will see the DT_FILTER
264 field. The dynamic linker will resolve symbols according to the
265 symbol table of the filter object as usual, but it will actually
266 link to the definitions found in the shared object name. Thus the
267 filter object can be used to select a subset of the symbols
268 provided by the object name.
269 Some older linkers used the -F option throughout a compilation
271 toolchain for specifying object-file format for both input and
272 output object files. The GNU linker uses other mechanisms for this
273 purpose: the -b, --format, --oformat options, the "TARGET" command
274 in linker scripts, and the "GNUTARGET" environment variable. The
275 GNU linker will ignore the -F option when not creating an ELF
276 shared object.
277 -fini name
279 When creating an ELF executable or shared object, call NAME when
280 the executable or shared object is unloaded, by setting DT_FINI to
281 the address of the function. By default, the linker uses "_fini"
282 as the function to call.
283 -g Ignored. Provided for compatibility with other tools.
285 -Gvalue
287 --gpsize=value
288 Set the maximum size of objects to be optimized using the GP
289 register to size. This is only meaningful for object file formats
290 such as MIPS ECOFF which supports putting large and small objects
291 into different sections. This is ignored for other object file
292 formats.
293 -hname
295 -soname=name
296 When creating an ELF shared object, set the internal DT_SONAME
297 field to the specified name. When an executable is linked with a
298 shared object which has a DT_SONAME field, then when the executable
299 is run the dynamic linker will attempt to load the shared object
300 specified by the DT_SONAME field rather than the using the file
301 name given to the linker.
302 -i Perform an incremental link (same as option -r).
304 -init name
306 When creating an ELF executable or shared object, call NAME when
307 the executable or shared object is loaded, by setting DT_INIT to
308 the address of the function. By default, the linker uses "_init"
309 as the function to call.
310 -lnamespec
312 --library=namespec
313 Add the archive or object file specified by namespec to the list of
314 files to link. This option may be used any number of times. If
315 namespec is of the form :filename, ld will search the library path
316 for a file called filename, otherise it will search the library
317 path for a file called libnamespec.a.
318 On systems which support shared libraries, ld may also search for
320 files other than libnamespec.a. Specifically, on ELF and SunOS
321 systems, ld will search a directory for a library called
322 libnamespec.so before searching for one called libnamespec.a. (By
323 convention, a ".so" extension indicates a shared library.) Note
324 that this behavior does not apply to :filename, which always
325 specifies a file called filename.
326 The linker will search an archive only once, at the location where
328 it is specified on the command line. If the archive defines a
329 symbol which was undefined in some object which appeared before the
330 archive on the command line, the linker will include the
331 appropriate file(s) from the archive. However, an undefined symbol
332 in an object appearing later on the command line will not cause the
333 linker to search the archive again.
334 See the -( option for a way to force the linker to search archives
336 multiple times.
337 You may list the same archive multiple times on the command line.
339 This type of archive searching is standard for Unix linkers.
341 However, if you are using ld on AIX, note that it is different from
342 the behaviour of the AIX linker.
343 -Lsearchdir
345 --library-path=searchdir
346 Add path searchdir to the list of paths that ld will search for
347 archive libraries and ld control scripts. You may use this option
348 any number of times. The directories are searched in the order in
349 which they are specified on the command line. Directories
350 specified on the command line are searched before the default
351 directories. All -L options apply to all -l options, regardless of
352 the order in which the options appear.
353 If searchdir begins with "=", then the "=" will be replaced by the
355 sysroot prefix, a path specified when the linker is configured.
356 The default set of paths searched (without being specified with -L)
358 depends on which emulation mode ld is using, and in some cases also
359 on how it was configured.
360 The paths can also be specified in a link script with the
362 "SEARCH_DIR" command. Directories specified this way are searched
363 at the point in which the linker script appears in the command
364 line.
365 -memulation
367 Emulate the emulation linker. You can list the available
368 emulations with the --verbose or -V options.
369 If the -m option is not used, the emulation is taken from the
371 "LDEMULATION" environment variable, if that is defined.
372 Otherwise, the default emulation depends upon how the linker was
374 configured.
375 -M
377 --print-map
378 Print a link map to the standard output. A link map provides
379 information about the link, including the following:
380 · Where object files are mapped into memory.
382 · How common symbols are allocated.
384 · All archive members included in the link, with a mention of the
386 symbol which caused the archive member to be brought in.
387 · The values assigned to symbols.
389 Note - symbols whose values are computed by an expression which
391 involves a reference to a previous value of the same symbol may
392 not have correct result displayed in the link map. This is
393 because the linker discards intermediate results and only
394 retains the final value of an expression. Under such
395 circumstances the linker will display the final value enclosed
396 by square brackets. Thus for example a linker script
397 containing:
398 foo = 1
400 foo = foo * 4
401 foo = foo + 8
402 will produce the following output in the link map if the -M
404 option is used:
405 0x00000001 foo = 0x1
407 [0x0000000c] foo = (foo * 0x4)
408 [0x0000000c] foo = (foo + 0x8)
409 See Expressions for more information about expressions in
411 linker scripts.
412 -n
414 --nmagic
415 Turn off page alignment of sections, and mark the output as
416 "NMAGIC" if possible.
417 -N
419 --omagic
420 Set the text and data sections to be readable and writable. Also,
421 do not page-align the data segment, and disable linking against
422 shared libraries. If the output format supports Unix style magic
423 numbers, mark the output as "OMAGIC". Note: Although a writable
424 text section is allowed for PE-COFF targets, it does not conform to
425 the format specification published by Microsoft.
426 --no-omagic
428 This option negates most of the effects of the -N option. It sets
429 the text section to be read-only, and forces the data segment to be
430 page-aligned. Note - this option does not enable linking against
431 shared libraries. Use -Bdynamic for this.
432 -o output
434 --output=output
435 Use output as the name for the program produced by ld; if this
436 option is not specified, the name a.out is used by default. The
437 script command "OUTPUT" can also specify the output file name.
438 -O level
440 If level is a numeric values greater than zero ld optimizes the
441 output. This might take significantly longer and therefore
442 probably should only be enabled for the final binary. At the
443 moment this option only affects ELF shared library generation.
444 Future releases of the linker may make more use of this option.
445 Also currently there is no difference in the linker's behaviour for
446 different non-zero values of this option. Again this may change
447 with future releases.
448 -q
450 --emit-relocs
451 Leave relocation sections and contents in fully linked executables.
452 Post link analysis and optimization tools may need this information
453 in order to perform correct modifications of executables. This
454 results in larger executables.
455 This option is currently only supported on ELF platforms.
457 --force-dynamic
459 Force the output file to have dynamic sections. This option is
460 specific to VxWorks targets.
461 -r
463 --relocatable
464 Generate relocatable output---i.e., generate an output file that
465 can in turn serve as input to ld. This is often called partial
466 linking. As a side effect, in environments that support standard
467 Unix magic numbers, this option also sets the output file's magic
468 number to "OMAGIC". If this option is not specified, an absolute
469 file is produced. When linking C++ programs, this option will not
470 resolve references to constructors; to do that, use -Ur.
471 When an input file does not have the same format as the output
473 file, partial linking is only supported if that input file does not
474 contain any relocations. Different output formats can have further
475 restrictions; for example some "a.out"-based formats do not support
476 partial linking with input files in other formats at all.
477 This option does the same thing as -i.
479 -R filename
481 --just-symbols=filename
482 Read symbol names and their addresses from filename, but do not
483 relocate it or include it in the output. This allows your output
484 file to refer symbolically to absolute locations of memory defined
485 in other programs. You may use this option more than once.
486 For compatibility with other ELF linkers, if the -R option is
488 followed by a directory name, rather than a file name, it is
489 treated as the -rpath option.
490 -s
492 --strip-all
493 Omit all symbol information from the output file.
494 -S
496 --strip-debug
497 Omit debugger symbol information (but not all symbols) from the
498 output file.
499 -t
501 --trace
502 Print the names of the input files as ld processes them.
503 -T scriptfile
505 --script=scriptfile
506 Use scriptfile as the linker script. This script replaces ld's
507 default linker script (rather than adding to it), so commandfile
508 must specify everything necessary to describe the output file.
509 If scriptfile does not exist in the current directory, "ld" looks
510 for it in the directories specified by any preceding -L options.
511 Multiple -T options accumulate.
512 -dT scriptfile
514 --default-script=scriptfile
515 Use scriptfile as the default linker script.
516 This option is similar to the --script option except that
518 processing of the script is delayed until after the rest of the
519 command line has been processed. This allows options placed after
520 the --default-script option on the command line to affect the
521 behaviour of the linker script, which can be important when the
522 linker command line cannot be directly controlled by the user. (eg
523 because the command line is being constructed by another tool, such
524 as gcc).
525 -u symbol
527 --undefined=symbol
528 Force symbol to be entered in the output file as an undefined
529 symbol. Doing this may, for example, trigger linking of additional
530 modules from standard libraries. -u may be repeated with different
531 option arguments to enter additional undefined symbols. This
532 option is equivalent to the "EXTERN" linker script command.
533 -Ur For anything other than C++ programs, this option is equivalent to
535 -r: it generates relocatable output---i.e., an output file that can
536 in turn serve as input to ld. When linking C++ programs, -Ur does
537 resolve references to constructors, unlike -r. It does not work to
538 use -Ur on files that were themselves linked with -Ur; once the
539 constructor table has been built, it cannot be added to. Use -Ur
540 only for the last partial link, and -r for the others.
541 --unique[=SECTION]
543 Creates a separate output section for every input section matching
544 SECTION, or if the optional wildcard SECTION argument is missing,
545 for every orphan input section. An orphan section is one not
546 specifically mentioned in a linker script. You may use this option
547 multiple times on the command line; It prevents the normal merging
548 of input sections with the same name, overriding output section
549 assignments in a linker script.
550 -v
552 --version
553 -V Display the version number for ld. The -V option also lists the
554 supported emulations.
555 -x
557 --discard-all
558 Delete all local symbols.
559 -X
561 --discard-locals
562 Delete all temporary local symbols. (These symbols start with
563 system-specific local label prefixes, typically .L for ELF systems
564 or L for traditional a.out systems.)
565 -y symbol
567 --trace-symbol=symbol
568 Print the name of each linked file in which symbol appears. This
569 option may be given any number of times. On many systems it is
570 necessary to prepend an underscore.
571 This option is useful when you have an undefined symbol in your
573 link but don't know where the reference is coming from.
574 -Y path
576 Add path to the default library search path. This option exists
577 for Solaris compatibility.
578 -z keyword
580 The recognized keywords are:
581 combreloc
583 Combines multiple reloc sections and sorts them to make dynamic
584 symbol lookup caching possible.
585 defs
587 Disallows undefined symbols in object files. Undefined symbols
588 in shared libraries are still allowed.
589 execstack
591 Marks the object as requiring executable stack.
592 initfirst
594 This option is only meaningful when building a shared object.
595 It marks the object so that its runtime initialization will
596 occur before the runtime initialization of any other objects
597 brought into the process at the same time. Similarly the
598 runtime finalization of the object will occur after the runtime
599 finalization of any other objects.
600 interpose
602 Marks the object that its symbol table interposes before all
603 symbols but the primary executable.
604 lazy
606 When generating an executable or shared library, mark it to
607 tell the dynamic linker to defer function call resolution to
608 the point when the function is called (lazy binding), rather
609 than at load time. Lazy binding is the default.
610 loadfltr
612 Marks the object that its filters be processed immediately at
613 runtime.
614 muldefs
616 Allows multiple definitions.
617 nocombreloc
619 Disables multiple reloc sections combining.
620 nocopyreloc
622 Disables production of copy relocs.
623 nodefaultlib
625 Marks the object that the search for dependencies of this
626 object will ignore any default library search paths.
627 nodelete
629 Marks the object shouldn't be unloaded at runtime.
630 nodlopen
632 Marks the object not available to "dlopen".
633 nodump
635 Marks the object can not be dumped by "dldump".
636 noexecstack
638 Marks the object as not requiring executable stack.
639 norelro
641 Don't create an ELF "PT_GNU_RELRO" segment header in the
642 object.
643 now When generating an executable or shared library, mark it to
645 tell the dynamic linker to resolve all symbols when the program
646 is started, or when the shared library is linked to using
647 dlopen, instead of deferring function call resolution to the
648 point when the function is first called.
649 origin
651 Marks the object may contain $ORIGIN.
652 relro
654 Create an ELF "PT_GNU_RELRO" segment header in the object.
655 max-page-size=value
657 Set the emulation maximum page size to value.
658 common-page-size=value
660 Set the emulation common page size to value.
661 Other keywords are ignored for Solaris compatibility.
663 -( archives -)
665 --start-group archives --end-group
666 The archives should be a list of archive files. They may be either
667 explicit file names, or -l options.
668 The specified archives are searched repeatedly until no new
670 undefined references are created. Normally, an archive is searched
671 only once in the order that it is specified on the command line.
672 If a symbol in that archive is needed to resolve an undefined
673 symbol referred to by an object in an archive that appears later on
674 the command line, the linker would not be able to resolve that
675 reference. By grouping the archives, they all be searched
676 repeatedly until all possible references are resolved.
677 Using this option has a significant performance cost. It is best
679 to use it only when there are unavoidable circular references
680 between two or more archives.
681 --accept-unknown-input-arch
683 --no-accept-unknown-input-arch
684 Tells the linker to accept input files whose architecture cannot be
685 recognised. The assumption is that the user knows what they are
686 doing and deliberately wants to link in these unknown input files.
687 This was the default behaviour of the linker, before release 2.14.
688 The default behaviour from release 2.14 onwards is to reject such
689 input files, and so the --accept-unknown-input-arch option has been
690 added to restore the old behaviour.
691 --as-needed
693 --no-as-needed
694 This option affects ELF DT_NEEDED tags for dynamic libraries
695 mentioned on the command line after the --as-needed option.
696 Normally, the linker will add a DT_NEEDED tag for each dynamic
697 library mentioned on the command line, regardless of whether the
698 library is actually needed. --as-needed causes DT_NEEDED tags to
699 only be emitted for libraries that satisfy some symbol reference
700 from regular objects which is undefined at the point that the
701 library was linked. --no-as-needed restores the default behaviour.
702 --add-needed
704 --no-add-needed
705 This option affects the treatment of dynamic libraries from ELF
706 DT_NEEDED tags in dynamic libraries mentioned on the command line
707 after the --no-add-needed option. Normally, the linker will add a
708 DT_NEEDED tag for each dynamic library from DT_NEEDED tags.
709 --no-add-needed causes DT_NEEDED tags will never be emitted for
710 those libraries from DT_NEEDED tags. --add-needed restores the
711 default behaviour.
712 -assert keyword
714 This option is ignored for SunOS compatibility.
715 -Bdynamic
717 -dy
718 -call_shared
719 Link against dynamic libraries. This is only meaningful on
720 platforms for which shared libraries are supported. This option is
721 normally the default on such platforms. The different variants of
722 this option are for compatibility with various systems. You may
723 use this option multiple times on the command line: it affects
724 library searching for -l options which follow it.
725 -Bgroup
727 Set the "DF_1_GROUP" flag in the "DT_FLAGS_1" entry in the dynamic
728 section. This causes the runtime linker to handle lookups in this
729 object and its dependencies to be performed only inside the group.
730 --unresolved-symbols=report-all is implied. This option is only
731 meaningful on ELF platforms which support shared libraries.
732 -Bstatic
734 -dn
735 -non_shared
736 -static
737 Do not link against shared libraries. This is only meaningful on
738 platforms for which shared libraries are supported. The different
739 variants of this option are for compatibility with various systems.
740 You may use this option multiple times on the command line: it
741 affects library searching for -l options which follow it. This
742 option also implies --unresolved-symbols=report-all. This option
743 can be used with -shared. Doing so means that a shared library is
744 being created but that all of the library's external references
745 must be resolved by pulling in entries from static libraries.
746 -Bsymbolic
748 When creating a shared library, bind references to global symbols
749 to the definition within the shared library, if any. Normally, it
750 is possible for a program linked against a shared library to
751 override the definition within the shared library. This option is
752 only meaningful on ELF platforms which support shared libraries.
753 -Bsymbolic-functions
755 When creating a shared library, bind references to global function
756 symbols to the definition within the shared library, if any. This
757 option is only meaningful on ELF platforms which support shared
758 libraries.
759 --dynamic-list=dynamic-list-file
761 Specify the name of a dynamic list file to the linker. This is
762 typically used when creating shared libraries to specify a list of
763 global symbols whose references shouldn't be bound to the
764 definition within the shared library, or creating dynamically
765 linked executables to specify a list of symbols which should be
766 added to the symbol table in the executable. This option is only
767 meaningful on ELF platforms which support shared libraries.
768 The format of the dynamic list is the same as the version node
770 without scope and node name. See VERSION for more information.
771 --dynamic-list-data
773 Include all global data symbols to the dynamic list.
774 --dynamic-list-cpp-new
776 Provide the builtin dynamic list for C++ operator new and delete.
777 It is mainly useful for building shared libstdc++.
778 --dynamic-list-cpp-typeinfo
780 Provide the builtin dynamic list for C++ runtime type
781 identification.
782 --check-sections
784 --no-check-sections
785 Asks the linker not to check section addresses after they have been
786 assigned to see if there are any overlaps. Normally the linker
787 will perform this check, and if it finds any overlaps it will
788 produce suitable error messages. The linker does know about, and
789 does make allowances for sections in overlays. The default
790 behaviour can be restored by using the command line switch
791 --check-sections.
792 --cref
794 Output a cross reference table. If a linker map file is being
795 generated, the cross reference table is printed to the map file.
796 Otherwise, it is printed on the standard output.
797 The format of the table is intentionally simple, so that it may be
799 easily processed by a script if necessary. The symbols are printed
800 out, sorted by name. For each symbol, a list of file names is
801 given. If the symbol is defined, the first file listed is the
802 location of the definition. The remaining files contain references
803 to the symbol.
804 --no-define-common
806 This option inhibits the assignment of addresses to common symbols.
807 The script command "INHIBIT_COMMON_ALLOCATION" has the same effect.
808 The --no-define-common option allows decoupling the decision to
810 assign addresses to Common symbols from the choice of the output
811 file type; otherwise a non-Relocatable output type forces assigning
812 addresses to Common symbols. Using --no-define-common allows
813 Common symbols that are referenced from a shared library to be
814 assigned addresses only in the main program. This eliminates the
815 unused duplicate space in the shared library, and also prevents any
816 possible confusion over resolving to the wrong duplicate when there
817 are many dynamic modules with specialized search paths for runtime
818 symbol resolution.
819 --defsym symbol=expression
821 Create a global symbol in the output file, containing the absolute
822 address given by expression. You may use this option as many times
823 as necessary to define multiple symbols in the command line. A
824 limited form of arithmetic is supported for the expression in this
825 context: you may give a hexadecimal constant or the name of an
826 existing symbol, or use "+" and "-" to add or subtract hexadecimal
827 constants or symbols. If you need more elaborate expressions,
828 consider using the linker command language from a script. Note:
829 there should be no white space between symbol, the equals sign
830 ("="), and expression.
831 --demangle[=style]
833 --no-demangle
834 These options control whether to demangle symbol names in error
835 messages and other output. When the linker is told to demangle, it
836 tries to present symbol names in a readable fashion: it strips
837 leading underscores if they are used by the object file format, and
838 converts C++ mangled symbol names into user readable names.
839 Different compilers have different mangling styles. The optional
840 demangling style argument can be used to choose an appropriate
841 demangling style for your compiler. The linker will demangle by
842 default unless the environment variable COLLECT_NO_DEMANGLE is set.
843 These options may be used to override the default.
844 --dynamic-linker file
846 Set the name of the dynamic linker. This is only meaningful when
847 generating dynamically linked ELF executables. The default dynamic
848 linker is normally correct; don't use this unless you know what you
849 are doing.
850 --fatal-warnings
852 --no-fatal-warnings
853 Treat all warnings as errors. The default behaviour can be
854 restored with the option --no-fatal-warnings.
855 --force-exe-suffix
857 Make sure that an output file has a .exe suffix.
858 If a successfully built fully linked output file does not have a
860 ".exe" or ".dll" suffix, this option forces the linker to copy the
861 output file to one of the same name with a ".exe" suffix. This
862 option is useful when using unmodified Unix makefiles on a
863 Microsoft Windows host, since some versions of Windows won't run an
864 image unless it ends in a ".exe" suffix.
865 --gc-sections
867 --no-gc-sections
868 Enable garbage collection of unused input sections. It is ignored
869 on targets that do not support this option. The default behaviour
870 (of not performing this garbage collection) can be restored by
871 specifying --no-gc-sections on the command line.
872 --gc-sections decides which input sections are used by examining
874 symbols and relocations. The section containing the entry symbol
875 and all sections containing symbols undefined on the command-line
876 will be kept, as will sections containing symbols referenced by
877 dynamic objects. Note that when building shared libraries, the
878 linker must assume that any visible symbol is referenced. Once
879 this initial set of sections has been determined, the linker
880 recursively marks as used any section referenced by their
881 relocations. See --entry and --undefined.
882 This option can be set when doing a partial link (enabled with
884 option -r). In this case the root of symbols kept must be
885 explicitely specified either by an --entry or --undefined option or
886 by a "ENTRY" command in the linker script.
887 --print-gc-sections
889 --no-print-gc-sections
890 List all sections removed by garbage collection. The listing is
891 printed on stderr. This option is only effective if garbage
892 collection has been enabled via the --gc-sections) option. The
893 default behaviour (of not listing the sections that are removed)
894 can be restored by specifying --no-print-gc-sections on the command
895 line.
896 --help
898 Print a summary of the command-line options on the standard output
899 and exit.
900 --target-help
902 Print a summary of all target specific options on the standard
903 output and exit.
904 -Map mapfile
906 Print a link map to the file mapfile. See the description of the
907 -M option, above.
908 --no-keep-memory
910 ld normally optimizes for speed over memory usage by caching the
911 symbol tables of input files in memory. This option tells ld to
912 instead optimize for memory usage, by rereading the symbol tables
913 as necessary. This may be required if ld runs out of memory space
914 while linking a large executable.
915 --no-undefined
917 -z defs
918 Report unresolved symbol references from regular object files.
919 This is done even if the linker is creating a non-symbolic shared
920 library. The switch --[no-]allow-shlib-undefined controls the
921 behaviour for reporting unresolved references found in shared
922 libraries being linked in.
923 --allow-multiple-definition
925 -z muldefs
926 Normally when a symbol is defined multiple times, the linker will
927 report a fatal error. These options allow multiple definitions and
928 the first definition will be used.
929 --allow-shlib-undefined
931 --no-allow-shlib-undefined
932 Allows (the default) or disallows undefined symbols in shared
933 libraries. This switch is similar to --no-undefined except that it
934 determines the behaviour when the undefined symbols are in a shared
935 library rather than a regular object file. It does not affect how
936 undefined symbols in regular object files are handled.
937 The reason that --allow-shlib-undefined is the default is that the
939 shared library being specified at link time may not be the same as
940 the one that is available at load time, so the symbols might
941 actually be resolvable at load time. Plus there are some systems,
942 (eg BeOS) where undefined symbols in shared libraries is normal.
943 (The kernel patches them at load time to select which function is
944 most appropriate for the current architecture. This is used for
945 example to dynamically select an appropriate memset function).
946 Apparently it is also normal for HPPA shared libraries to have
947 undefined symbols.
948 --no-undefined-version
950 Normally when a symbol has an undefined version, the linker will
951 ignore it. This option disallows symbols with undefined version and
952 a fatal error will be issued instead.
953 --default-symver
955 Create and use a default symbol version (the soname) for
956 unversioned exported symbols.
957 --default-imported-symver
959 Create and use a default symbol version (the soname) for
960 unversioned imported symbols.
961 --no-warn-mismatch
963 Normally ld will give an error if you try to link together input
964 files that are mismatched for some reason, perhaps because they
965 have been compiled for different processors or for different
966 endiannesses. This option tells ld that it should silently permit
967 such possible errors. This option should only be used with care,
968 in cases when you have taken some special action that ensures that
969 the linker errors are inappropriate.
970 --no-warn-search-mismatch
972 Normally ld will give a warning if it finds an incompatible library
973 during a library search. This option silences the warning.
974 --no-whole-archive
976 Turn off the effect of the --whole-archive option for subsequent
977 archive files.
978 --noinhibit-exec
980 Retain the executable output file whenever it is still usable.
981 Normally, the linker will not produce an output file if it
982 encounters errors during the link process; it exits without writing
983 an output file when it issues any error whatsoever.
984 -nostdlib
986 Only search library directories explicitly specified on the command
987 line. Library directories specified in linker scripts (including
988 linker scripts specified on the command line) are ignored.
989 --oformat output-format
991 ld may be configured to support more than one kind of object file.
992 If your ld is configured this way, you can use the --oformat option
993 to specify the binary format for the output object file. Even when
994 ld is configured to support alternative object formats, you don't
995 usually need to specify this, as ld should be configured to produce
996 as a default output format the most usual format on each machine.
997 output-format is a text string, the name of a particular format
998 supported by the BFD libraries. (You can list the available binary
999 formats with objdump -i.) The script command "OUTPUT_FORMAT" can
1000 also specify the output format, but this option overrides it.
1001 -pie
1003 --pic-executable
1004 Create a position independent executable. This is currently only
1005 supported on ELF platforms. Position independent executables are
1006 similar to shared libraries in that they are relocated by the
1007 dynamic linker to the virtual address the OS chooses for them
1008 (which can vary between invocations). Like normal dynamically
1009 linked executables they can be executed and symbols defined in the
1010 executable cannot be overridden by shared libraries.
1011 -qmagic
1013 This option is ignored for Linux compatibility.
1014 -Qy This option is ignored for SVR4 compatibility.
1016 --relax
1018 An option with machine dependent effects. This option is only
1019 supported on a few targets.
1020 On some platforms, the --relax option performs global optimizations
1022 that become possible when the linker resolves addressing in the
1023 program, such as relaxing address modes and synthesizing new
1024 instructions in the output object file.
1025 On some platforms these link time global optimizations may make
1027 symbolic debugging of the resulting executable impossible. This is
1028 known to be the case for the Matsushita MN10200 and MN10300 family
1029 of processors.
1030 On platforms where this is not supported, --relax is accepted, but
1032 ignored.
1033 --retain-symbols-file filename
1035 Retain only the symbols listed in the file filename, discarding all
1036 others. filename is simply a flat file, with one symbol name per
1037 line. This option is especially useful in environments (such as
1038 VxWorks) where a large global symbol table is accumulated
1039 gradually, to conserve run-time memory.
1040 --retain-symbols-file does not discard undefined symbols, or
1042 symbols needed for relocations.
1043 You may only specify --retain-symbols-file once in the command
1045 line. It overrides -s and -S.
1046 -rpath dir
1048 Add a directory to the runtime library search path. This is used
1049 when linking an ELF executable with shared objects. All -rpath
1050 arguments are concatenated and passed to the runtime linker, which
1051 uses them to locate shared objects at runtime. The -rpath option
1052 is also used when locating shared objects which are needed by
1053 shared objects explicitly included in the link; see the description
1054 of the -rpath-link option. If -rpath is not used when linking an
1055 ELF executable, the contents of the environment variable
1056 "LD_RUN_PATH" will be used if it is defined.
1057 The -rpath option may also be used on SunOS. By default, on SunOS,
1059 the linker will form a runtime search patch out of all the -L
1060 options it is given. If a -rpath option is used, the runtime
1061 search path will be formed exclusively using the -rpath options,
1062 ignoring the -L options. This can be useful when using gcc, which
1063 adds many -L options which may be on NFS mounted file systems.
1064 For compatibility with other ELF linkers, if the -R option is
1066 followed by a directory name, rather than a file name, it is
1067 treated as the -rpath option.
1068 -rpath-link DIR
1070 When using ELF or SunOS, one shared library may require another.
1071 This happens when an "ld -shared" link includes a shared library as
1072 one of the input files.
1073 When the linker encounters such a dependency when doing a non-
1075 shared, non-relocatable link, it will automatically try to locate
1076 the required shared library and include it in the link, if it is
1077 not included explicitly. In such a case, the -rpath-link option
1078 specifies the first set of directories to search. The -rpath-link
1079 option may specify a sequence of directory names either by
1080 specifying a list of names separated by colons, or by appearing
1081 multiple times.
1082 This option should be used with caution as it overrides the search
1084 path that may have been hard compiled into a shared library. In
1085 such a case it is possible to use unintentionally a different
1086 search path than the runtime linker would do.
1087 The linker uses the following search paths to locate required
1089 shared libraries:
1090 1. Any directories specified by -rpath-link options.
1092 2. Any directories specified by -rpath options. The difference
1094 between -rpath and -rpath-link is that directories specified by
1095 -rpath options are included in the executable and used at
1096 runtime, whereas the -rpath-link option is only effective at
1097 link time. Searching -rpath in this way is only supported by
1098 native linkers and cross linkers which have been configured
1099 with the --with-sysroot option.
1100 3. On an ELF system, for native linkers, if the -rpath and
1102 -rpath-link options were not used, search the contents of the
1103 environment variable "LD_RUN_PATH".
1104 4. On SunOS, if the -rpath option was not used, search any
1106 directories specified using -L options.
1107 5. For a native linker, the search the contents of the environment
1109 variable "LD_LIBRARY_PATH".
1110 6. For a native ELF linker, the directories in "DT_RUNPATH" or
1112 "DT_RPATH" of a shared library are searched for shared
1113 libraries needed by it. The "DT_RPATH" entries are ignored if
1114 "DT_RUNPATH" entries exist.
1115 7. The default directories, normally /lib and /usr/lib.
1117 8. For a native linker on an ELF system, if the file
1119 /etc/ld.so.conf exists, the list of directories found in that
1120 file.
1121 If the required shared library is not found, the linker will issue
1123 a warning and continue with the link.
1124 -shared
1126 -Bshareable
1127 Create a shared library. This is currently only supported on ELF,
1128 XCOFF and SunOS platforms. On SunOS, the linker will automatically
1129 create a shared library if the -e option is not used and there are
1130 undefined symbols in the link.
1131 --sort-common [= ascending | descending]
1133 This option tells ld to sort the common symbols by alignment in
1134 ascending or descending order when it places them in the
1135 appropriate output sections. The symbol alignments considered are
1136 sixteen-byte or larger, eight-byte, four-byte, two-byte, and one-
1137 byte. This is to prevent gaps between symbols due to alignment
1138 constraints. If no sorting order is specified, then descending
1139 order is assumed.
1140 --sort-section name
1142 This option will apply "SORT_BY_NAME" to all wildcard section
1143 patterns in the linker script.
1144 --sort-section alignment
1146 This option will apply "SORT_BY_ALIGNMENT" to all wildcard section
1147 patterns in the linker script.
1148 --split-by-file [size]
1150 Similar to --split-by-reloc but creates a new output section for
1151 each input file when size is reached. size defaults to a size of 1
1152 if not given.
1153 --split-by-reloc [count]
1155 Tries to creates extra sections in the output file so that no
1156 single output section in the file contains more than count
1157 relocations. This is useful when generating huge relocatable files
1158 for downloading into certain real time kernels with the COFF object
1159 file format; since COFF cannot represent more than 65535
1160 relocations in a single section. Note that this will fail to work
1161 with object file formats which do not support arbitrary sections.
1162 The linker will not split up individual input sections for
1163 redistribution, so if a single input section contains more than
1164 count relocations one output section will contain that many
1165 relocations. count defaults to a value of 32768.
1166 --stats
1168 Compute and display statistics about the operation of the linker,
1169 such as execution time and memory usage.
1170 --sysroot=directory
1172 Use directory as the location of the sysroot, overriding the
1173 configure-time default. This option is only supported by linkers
1174 that were configured using --with-sysroot.
1175 --traditional-format
1177 For some targets, the output of ld is different in some ways from
1178 the output of some existing linker. This switch requests ld to use
1179 the traditional format instead.
1180 For example, on SunOS, ld combines duplicate entries in the symbol
1182 string table. This can reduce the size of an output file with full
1183 debugging information by over 30 percent. Unfortunately, the SunOS
1184 "dbx" program can not read the resulting program ("gdb" has no
1185 trouble). The --traditional-format switch tells ld to not combine
1186 duplicate entries.
1187 --section-start sectionname=org
1189 Locate a section in the output file at the absolute address given
1190 by org. You may use this option as many times as necessary to
1191 locate multiple sections in the command line. org must be a single
1192 hexadecimal integer; for compatibility with other linkers, you may
1193 omit the leading 0x usually associated with hexadecimal values.
1194 Note: there should be no white space between sectionname, the
1195 equals sign ("="), and org.
1196 -Tbss org
1198 -Tdata org
1199 -Ttext org
1200 Same as --section-start, with ".bss", ".data" or ".text" as the
1201 sectionname.
1202 --unresolved-symbols=method
1204 Determine how to handle unresolved symbols. There are four
1205 possible values for method:
1206 ignore-all
1208 Do not report any unresolved symbols.
1209 report-all
1211 Report all unresolved symbols. This is the default.
1212 ignore-in-object-files
1214 Report unresolved symbols that are contained in shared
1215 libraries, but ignore them if they come from regular object
1216 files.
1217 ignore-in-shared-libs
1219 Report unresolved symbols that come from regular object files,
1220 but ignore them if they come from shared libraries. This can
1221 be useful when creating a dynamic binary and it is known that
1222 all the shared libraries that it should be referencing are
1223 included on the linker's command line.
1224 The behaviour for shared libraries on their own can also be
1226 controlled by the --[no-]allow-shlib-undefined option.
1227 Normally the linker will generate an error message for each
1229 reported unresolved symbol but the option --warn-unresolved-symbols
1230 can change this to a warning.
1231 --dll-verbose
1233 --verbose
1234 Display the version number for ld and list the linker emulations
1235 supported. Display which input files can and cannot be opened.
1236 Display the linker script being used by the linker.
1237 --version-script=version-scriptfile
1239 Specify the name of a version script to the linker. This is
1240 typically used when creating shared libraries to specify additional
1241 information about the version hierarchy for the library being
1242 created. This option is only meaningful on ELF platforms which
1243 support shared libraries.
1244 --warn-common
1246 Warn when a common symbol is combined with another common symbol or
1247 with a symbol definition. Unix linkers allow this somewhat sloppy
1248 practise, but linkers on some other operating systems do not. This
1249 option allows you to find potential problems from combining global
1250 symbols. Unfortunately, some C libraries use this practise, so you
1251 may get some warnings about symbols in the libraries as well as in
1252 your programs.
1253 There are three kinds of global symbols, illustrated here by C
1255 examples:
1256 int i = 1;
1258 A definition, which goes in the initialized data section of the
1259 output file.
1260 extern int i;
1262 An undefined reference, which does not allocate space. There
1263 must be either a definition or a common symbol for the variable
1264 somewhere.
1265 int i;
1267 A common symbol. If there are only (one or more) common
1268 symbols for a variable, it goes in the uninitialized data area
1269 of the output file. The linker merges multiple common symbols
1270 for the same variable into a single symbol. If they are of
1271 different sizes, it picks the largest size. The linker turns a
1272 common symbol into a declaration, if there is a definition of
1273 the same variable.
1274 The --warn-common option can produce five kinds of warnings. Each
1276 warning consists of a pair of lines: the first describes the symbol
1277 just encountered, and the second describes the previous symbol
1278 encountered with the same name. One or both of the two symbols
1279 will be a common symbol.
1280 1. Turning a common symbol into a reference, because there is
1282 already a definition for the symbol.
1283 <file>(<section>): warning: common of `<symbol>'
1285 overridden by definition
1286 <file>(<section>): warning: defined here
1287 2. Turning a common symbol into a reference, because a later
1289 definition for the symbol is encountered. This is the same as
1290 the previous case, except that the symbols are encountered in a
1291 different order.
1292 <file>(<section>): warning: definition of `<symbol>'
1294 overriding common
1295 <file>(<section>): warning: common is here
1296 3. Merging a common symbol with a previous same-sized common
1298 symbol.
1299 <file>(<section>): warning: multiple common
1301 of `<symbol>'
1302 <file>(<section>): warning: previous common is here
1303 4. Merging a common symbol with a previous larger common symbol.
1305 <file>(<section>): warning: common of `<symbol>'
1307 overridden by larger common
1308 <file>(<section>): warning: larger common is here
1309 5. Merging a common symbol with a previous smaller common symbol.
1311 This is the same as the previous case, except that the symbols
1312 are encountered in a different order.
1313 <file>(<section>): warning: common of `<symbol>'
1315 overriding smaller common
1316 <file>(<section>): warning: smaller common is here
1317 --warn-constructors
1319 Warn if any global constructors are used. This is only useful for
1320 a few object file formats. For formats like COFF or ELF, the
1321 linker can not detect the use of global constructors.
1322 --warn-multiple-gp
1324 Warn if multiple global pointer values are required in the output
1325 file. This is only meaningful for certain processors, such as the
1326 Alpha. Specifically, some processors put large-valued constants in
1327 a special section. A special register (the global pointer) points
1328 into the middle of this section, so that constants can be loaded
1329 efficiently via a base-register relative addressing mode. Since
1330 the offset in base-register relative mode is fixed and relatively
1331 small (e.g., 16 bits), this limits the maximum size of the constant
1332 pool. Thus, in large programs, it is often necessary to use
1333 multiple global pointer values in order to be able to address all
1334 possible constants. This option causes a warning to be issued
1335 whenever this case occurs.
1336 --warn-once
1338 Only warn once for each undefined symbol, rather than once per
1339 module which refers to it.
1340 --warn-section-align
1342 Warn if the address of an output section is changed because of
1343 alignment. Typically, the alignment will be set by an input
1344 section. The address will only be changed if it not explicitly
1345 specified; that is, if the "SECTIONS" command does not specify a
1346 start address for the section.
1347 --warn-shared-textrel
1349 Warn if the linker adds a DT_TEXTREL to a shared object.
1350 --warn-unresolved-symbols
1352 If the linker is going to report an unresolved symbol (see the
1353 option --unresolved-symbols) it will normally generate an error.
1354 This option makes it generate a warning instead.
1355 --error-unresolved-symbols
1357 This restores the linker's default behaviour of generating errors
1358 when it is reporting unresolved symbols.
1359 --whole-archive
1361 For each archive mentioned on the command line after the
1362 --whole-archive option, include every object file in the archive in
1363 the link, rather than searching the archive for the required object
1364 files. This is normally used to turn an archive file into a shared
1365 library, forcing every object to be included in the resulting
1366 shared library. This option may be used more than once.
1367 Two notes when using this option from gcc: First, gcc doesn't know
1369 about this option, so you have to use -Wl,-whole-archive. Second,
1370 don't forget to use -Wl,-no-whole-archive after your list of
1371 archives, because gcc will add its own list of archives to your
1372 link and you may not want this flag to affect those as well.
1373 --wrap symbol
1375 Use a wrapper function for symbol. Any undefined reference to
1376 symbol will be resolved to "__wrap_symbol". Any undefined
1377 reference to "__real_symbol" will be resolved to symbol.
1378 This can be used to provide a wrapper for a system function. The
1380 wrapper function should be called "__wrap_symbol". If it wishes to
1381 call the system function, it should call "__real_symbol".
1382 Here is a trivial example:
1384 void *
1386 __wrap_malloc (size_t c)
1387 {
1388 printf ("malloc called with %zu\n", c);
1389 return __real_malloc (c);
1390 }
1391 If you link other code with this file using --wrap malloc, then all
1393 calls to "malloc" will call the function "__wrap_malloc" instead.
1394 The call to "__real_malloc" in "__wrap_malloc" will call the real
1395 "malloc" function.
1396 You may wish to provide a "__real_malloc" function as well, so that
1398 links without the --wrap option will succeed. If you do this, you
1399 should not put the definition of "__real_malloc" in the same file
1400 as "__wrap_malloc"; if you do, the assembler may resolve the call
1401 before the linker has a chance to wrap it to "malloc".
1402 --eh-frame-hdr
1404 Request creation of ".eh_frame_hdr" section and ELF
1405 "PT_GNU_EH_FRAME" segment header.
1406 --enable-new-dtags
1408 --disable-new-dtags
1409 This linker can create the new dynamic tags in ELF. But the older
1410 ELF systems may not understand them. If you specify
1411 --enable-new-dtags, the dynamic tags will be created as needed. If
1412 you specify --disable-new-dtags, no new dynamic tags will be
1413 created. By default, the new dynamic tags are not created. Note
1414 that those options are only available for ELF systems.
1415 --hash-size=number
1417 Set the default size of the linker's hash tables to a prime number
1418 close to number. Increasing this value can reduce the length of
1419 time it takes the linker to perform its tasks, at the expense of
1420 increasing the linker's memory requirements. Similarly reducing
1421 this value can reduce the memory requirements at the expense of
1422 speed.
1423 --hash-style=style
1425 Set the type of linker's hash table(s). style can be either "sysv"
1426 for classic ELF ".hash" section, "gnu" for new style GNU
1427 ".gnu.hash" section or "both" for both the classic ELF ".hash" and
1428 new style GNU ".gnu.hash" hash tables. The default is "sysv".
1429 --reduce-memory-overheads
1431 This option reduces memory requirements at ld runtime, at the
1432 expense of linking speed. This was introduced to select the old
1433 O(n^2) algorithm for link map file generation, rather than the new
1434 O(n) algorithm which uses about 40% more memory for symbol storage.
1435 Another effect of the switch is to set the default hash table size
1437 to 1021, which again saves memory at the cost of lengthening the
1438 linker's run time. This is not done however if the --hash-size
1439 switch has been used.
1440 The --reduce-memory-overheads switch may be also be used to enable
1442 other tradeoffs in future versions of the linker.
1443 --build-id
1445 --build-id=style
1446 Request creation of ".note.gnu.build-id" ELF note section. The
1447 contents of the note are unique bits identifying this linked file.
1448 style can be "uuid" to use 128 random bits, "sha1" to use a 160-bit
1449 SHA1 hash on the normative parts of the output contents, "md5" to
1450 use a 128-bit MD5 hash on the normative parts of the output
1451 contents, or "0xhexstring" to use a chosen bit string specified as
1452 an even number of hexadecimal digits ("-" and ":" characters
1453 between digit pairs are ignored). If style is omitted, "sha1" is
1454 used.
1455 The "md5" and "sha1" styles produces an identifier that is always
1457 the same in an identical output file, but will be unique among all
1458 nonidentical output files. It is not intended to be compared as a
1459 checksum for the file's contents. A linked file may be changed
1460 later by other tools, but the build ID bit string identifying the
1461 original linked file does not change.
1462 Passing "none" for style disables the setting from any "--build-id"
1464 options earlier on the command line.
1465 The i386 PE linker supports the -shared option, which causes the output
1467 to be a dynamically linked library (DLL) instead of a normal
1468 executable. You should name the output "*.dll" when you use this
1469 option. In addition, the linker fully supports the standard "*.def"
1470 files, which may be specified on the linker command line like an object
1471 file (in fact, it should precede archives it exports symbols from, to
1472 ensure that they get linked in, just like a normal object file).
1473 In addition to the options common to all targets, the i386 PE linker
1475 support additional command line options that are specific to the i386
1476 PE target. Options that take values may be separated from their values
1477 by either a space or an equals sign.
1478 --add-stdcall-alias
1480 If given, symbols with a stdcall suffix (@nn) will be exported as-
1481 is and also with the suffix stripped. [This option is specific to
1482 the i386 PE targeted port of the linker]
1483 --base-file file
1485 Use file as the name of a file in which to save the base addresses
1486 of all the relocations needed for generating DLLs with dlltool.
1487 [This is an i386 PE specific option]
1488 --dll
1490 Create a DLL instead of a regular executable. You may also use
1491 -shared or specify a "LIBRARY" in a given ".def" file. [This
1492 option is specific to the i386 PE targeted port of the linker]
1493 --enable-stdcall-fixup
1495 --disable-stdcall-fixup
1496 If the link finds a symbol that it cannot resolve, it will attempt
1497 to do "fuzzy linking" by looking for another defined symbol that
1498 differs only in the format of the symbol name (cdecl vs stdcall)
1499 and will resolve that symbol by linking to the match. For example,
1500 the undefined symbol "_foo" might be linked to the function
1501 "_foo@12", or the undefined symbol "_bar@16" might be linked to the
1502 function "_bar". When the linker does this, it prints a warning,
1503 since it normally should have failed to link, but sometimes import
1504 libraries generated from third-party dlls may need this feature to
1505 be usable. If you specify --enable-stdcall-fixup, this feature is
1506 fully enabled and warnings are not printed. If you specify
1507 --disable-stdcall-fixup, this feature is disabled and such
1508 mismatches are considered to be errors. [This option is specific
1509 to the i386 PE targeted port of the linker]
1510 --export-all-symbols
1512 If given, all global symbols in the objects used to build a DLL
1513 will be exported by the DLL. Note that this is the default if
1514 there otherwise wouldn't be any exported symbols. When symbols are
1515 explicitly exported via DEF files or implicitly exported via
1516 function attributes, the default is to not export anything else
1517 unless this option is given. Note that the symbols "DllMain@12",
1518 "DllEntryPoint@0", "DllMainCRTStartup@12", and "impure_ptr" will
1519 not be automatically exported. Also, symbols imported from other
1520 DLLs will not be re-exported, nor will symbols specifying the DLL's
1521 internal layout such as those beginning with "_head_" or ending
1522 with "_iname". In addition, no symbols from "libgcc", "libstd++",
1523 "libmingw32", or "crtX.o" will be exported. Symbols whose names
1524 begin with "__rtti_" or "__builtin_" will not be exported, to help
1525 with C++ DLLs. Finally, there is an extensive list of cygwin-
1526 private symbols that are not exported (obviously, this applies on
1527 when building DLLs for cygwin targets). These cygwin-excludes are:
1528 "_cygwin_dll_entry@12", "_cygwin_crt0_common@8",
1529 "_cygwin_noncygwin_dll_entry@12", "_fmode", "_impure_ptr",
1530 "cygwin_attach_dll", "cygwin_premain0", "cygwin_premain1",
1531 "cygwin_premain2", "cygwin_premain3", and "environ". [This option
1532 is specific to the i386 PE targeted port of the linker]
1533 --exclude-symbols symbol,symbol,...
1535 Specifies a list of symbols which should not be automatically
1536 exported. The symbol names may be delimited by commas or colons.
1537 [This option is specific to the i386 PE targeted port of the
1538 linker]
1539 --file-alignment
1541 Specify the file alignment. Sections in the file will always begin
1542 at file offsets which are multiples of this number. This defaults
1543 to 512. [This option is specific to the i386 PE targeted port of
1544 the linker]
1545 --heap reserve
1547 --heap reserve,commit
1548 Specify the number of bytes of memory to reserve (and optionally
1549 commit) to be used as heap for this program. The default is 1Mb
1550 reserved, 4K committed. [This option is specific to the i386 PE
1551 targeted port of the linker]
1552 --image-base value
1554 Use value as the base address of your program or dll. This is the
1555 lowest memory location that will be used when your program or dll
1556 is loaded. To reduce the need to relocate and improve performance
1557 of your dlls, each should have a unique base address and not
1558 overlap any other dlls. The default is 0x400000 for executables,
1559 and 0x10000000 for dlls. [This option is specific to the i386 PE
1560 targeted port of the linker]
1561 --kill-at
1563 If given, the stdcall suffixes (@nn) will be stripped from symbols
1564 before they are exported. [This option is specific to the i386 PE
1565 targeted port of the linker]
1566 --large-address-aware
1568 If given, the appropriate bit in the "Characteristics" field of the
1569 COFF header is set to indicate that this executable supports
1570 virtual addresses greater than 2 gigabytes. This should be used in
1571 conjunction with the /3GB or /USERVA=value megabytes switch in the
1572 "[operating systems]" section of the BOOT.INI. Otherwise, this bit
1573 has no effect. [This option is specific to PE targeted ports of
1574 the linker]
1575 --major-image-version value
1577 Sets the major number of the "image version". Defaults to 1.
1578 [This option is specific to the i386 PE targeted port of the
1579 linker]
1580 --major-os-version value
1582 Sets the major number of the "os version". Defaults to 4. [This
1583 option is specific to the i386 PE targeted port of the linker]
1584 --major-subsystem-version value
1586 Sets the major number of the "subsystem version". Defaults to 4.
1587 [This option is specific to the i386 PE targeted port of the
1588 linker]
1589 --minor-image-version value
1591 Sets the minor number of the "image version". Defaults to 0.
1592 [This option is specific to the i386 PE targeted port of the
1593 linker]
1594 --minor-os-version value
1596 Sets the minor number of the "os version". Defaults to 0. [This
1597 option is specific to the i386 PE targeted port of the linker]
1598 --minor-subsystem-version value
1600 Sets the minor number of the "subsystem version". Defaults to 0.
1601 [This option is specific to the i386 PE targeted port of the
1602 linker]
1603 --output-def file
1605 The linker will create the file file which will contain a DEF file
1606 corresponding to the DLL the linker is generating. This DEF file
1607 (which should be called "*.def") may be used to create an import
1608 library with "dlltool" or may be used as a reference to
1609 automatically or implicitly exported symbols. [This option is
1610 specific to the i386 PE targeted port of the linker]
1611 --out-implib file
1613 The linker will create the file file which will contain an import
1614 lib corresponding to the DLL the linker is generating. This import
1615 lib (which should be called "*.dll.a" or "*.a" may be used to link
1616 clients against the generated DLL; this behaviour makes it possible
1617 to skip a separate "dlltool" import library creation step. [This
1618 option is specific to the i386 PE targeted port of the linker]
1619 --enable-auto-image-base
1621 Automatically choose the image base for DLLs, unless one is
1622 specified using the "--image-base" argument. By using a hash
1623 generated from the dllname to create unique image bases for each
1624 DLL, in-memory collisions and relocations which can delay program
1625 execution are avoided. [This option is specific to the i386 PE
1626 targeted port of the linker]
1627 --disable-auto-image-base
1629 Do not automatically generate a unique image base. If there is no
1630 user-specified image base ("--image-base") then use the platform
1631 default. [This option is specific to the i386 PE targeted port of
1632 the linker]
1633 --dll-search-prefix string
1635 When linking dynamically to a dll without an import library, search
1636 for "<string><basename>.dll" in preference to "lib<basename>.dll".
1637 This behaviour allows easy distinction between DLLs built for the
1638 various "subplatforms": native, cygwin, uwin, pw, etc. For
1639 instance, cygwin DLLs typically use "--dll-search-prefix=cyg".
1640 [This option is specific to the i386 PE targeted port of the
1641 linker]
1642 --enable-auto-import
1644 Do sophisticated linking of "_symbol" to "__imp__symbol" for DATA
1645 imports from DLLs, and create the necessary thunking symbols when
1646 building the import libraries with those DATA exports. Note: Use of
1647 the 'auto-import' extension will cause the text section of the
1648 image file to be made writable. This does not conform to the PE-
1649 COFF format specification published by Microsoft.
1650 Note - use of the 'auto-import' extension will also cause read only
1652 data which would normally be placed into the .rdata section to be
1653 placed into the .data section instead. This is in order to work
1654 around a problem with consts that is described here:
1655 http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
1656 Using 'auto-import' generally will 'just work' -- but sometimes you
1658 may see this message:
1659 "variable '<var>' can't be auto-imported. Please read the
1661 documentation for ld's "--enable-auto-import" for details."
1662 This message occurs when some (sub)expression accesses an address
1664 ultimately given by the sum of two constants (Win32 import tables
1665 only allow one). Instances where this may occur include accesses
1666 to member fields of struct variables imported from a DLL, as well
1667 as using a constant index into an array variable imported from a
1668 DLL. Any multiword variable (arrays, structs, long long, etc) may
1669 trigger this error condition. However, regardless of the exact
1670 data type of the offending exported variable, ld will always detect
1671 it, issue the warning, and exit.
1672 There are several ways to address this difficulty, regardless of
1674 the data type of the exported variable:
1675 One way is to use --enable-runtime-pseudo-reloc switch. This leaves
1677 the task of adjusting references in your client code for runtime
1678 environment, so this method works only when runtime environment
1679 supports this feature.
1680 A second solution is to force one of the 'constants' to be a
1682 variable -- that is, unknown and un-optimizable at compile time.
1683 For arrays, there are two possibilities: a) make the indexee (the
1684 array's address) a variable, or b) make the 'constant' index a
1685 variable. Thus:
1686 extern type extern_array[];
1688 extern_array[1] -->
1689 { volatile type *t=extern_array; t[1] }
1690 or
1692 extern type extern_array[];
1694 extern_array[1] -->
1695 { volatile int t=1; extern_array[t] }
1696 For structs (and most other multiword data types) the only option
1698 is to make the struct itself (or the long long, or the ...)
1699 variable:
1700 extern struct s extern_struct;
1702 extern_struct.field -->
1703 { volatile struct s *t=&extern_struct; t->field }
1704 or
1706 extern long long extern_ll;
1708 extern_ll -->
1709 { volatile long long * local_ll=&extern_ll; *local_ll }
1710 A third method of dealing with this difficulty is to abandon
1712 'auto-import' for the offending symbol and mark it with
1713 "__declspec(dllimport)". However, in practise that requires using
1714 compile-time #defines to indicate whether you are building a DLL,
1715 building client code that will link to the DLL, or merely
1716 building/linking to a static library. In making the choice
1717 between the various methods of resolving the 'direct address with
1718 constant offset' problem, you should consider typical real-world
1719 usage:
1720 Original:
1722 --foo.h
1724 extern int arr[];
1725 --foo.c
1726 #include "foo.h"
1727 void main(int argc, char **argv){
1728 printf("%d\n",arr[1]);
1729 }
1730 Solution 1:
1732 --foo.h
1734 extern int arr[];
1735 --foo.c
1736 #include "foo.h"
1737 void main(int argc, char **argv){
1738 /* This workaround is for win32 and cygwin; do not "optimize" */
1739 volatile int *parr = arr;
1740 printf("%d\n",parr[1]);
1741 }
1742 Solution 2:
1744 --foo.h
1746 /* Note: auto-export is assumed (no __declspec(dllexport)) */
1747 #if (defined(_WIN32) || defined(__CYGWIN__)) && \
1748 !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
1749 #define FOO_IMPORT __declspec(dllimport)
1750 #else
1751 #define FOO_IMPORT
1752 #endif
1753 extern FOO_IMPORT int arr[];
1754 --foo.c
1755 #include "foo.h"
1756 void main(int argc, char **argv){
1757 printf("%d\n",arr[1]);
1758 }
1759 A fourth way to avoid this problem is to re-code your library to
1761 use a functional interface rather than a data interface for the
1762 offending variables (e.g. set_foo() and get_foo() accessor
1763 functions). [This option is specific to the i386 PE targeted port
1764 of the linker]
1765 --disable-auto-import
1767 Do not attempt to do sophisticated linking of "_symbol" to
1768 "__imp__symbol" for DATA imports from DLLs. [This option is
1769 specific to the i386 PE targeted port of the linker]
1770 --enable-runtime-pseudo-reloc
1772 If your code contains expressions described in --enable-auto-import
1773 section, that is, DATA imports from DLL with non-zero offset, this
1774 switch will create a vector of 'runtime pseudo relocations' which
1775 can be used by runtime environment to adjust references to such
1776 data in your client code. [This option is specific to the i386 PE
1777 targeted port of the linker]
1778 --disable-runtime-pseudo-reloc
1780 Do not create pseudo relocations for non-zero offset DATA imports
1781 from DLLs. This is the default. [This option is specific to the
1782 i386 PE targeted port of the linker]
1783 --enable-extra-pe-debug
1785 Show additional debug info related to auto-import symbol thunking.
1786 [This option is specific to the i386 PE targeted port of the
1787 linker]
1788 --section-alignment
1790 Sets the section alignment. Sections in memory will always begin
1791 at addresses which are a multiple of this number. Defaults to
1792 0x1000. [This option is specific to the i386 PE targeted port of
1793 the linker]
1794 --stack reserve
1796 --stack reserve,commit
1797 Specify the number of bytes of memory to reserve (and optionally
1798 commit) to be used as stack for this program. The default is 2Mb
1799 reserved, 4K committed. [This option is specific to the i386 PE
1800 targeted port of the linker]
1801 --subsystem which
1803 --subsystem which:major
1804 --subsystem which:major.minor
1805 Specifies the subsystem under which your program will execute. The
1806 legal values for which are "native", "windows", "console", "posix",
1807 and "xbox". You may optionally set the subsystem version also.
1808 Numeric values are also accepted for which. [This option is
1809 specific to the i386 PE targeted port of the linker]
1810 The 68HC11 and 68HC12 linkers support specific options to control the
1812 memory bank switching mapping and trampoline code generation.
1813 --no-trampoline
1815 This option disables the generation of trampoline. By default a
1816 trampoline is generated for each far function which is called using
1817 a "jsr" instruction (this happens when a pointer to a far function
1818 is taken).
1819 --bank-window name
1821 This option indicates to the linker the name of the memory region
1822 in the MEMORY specification that describes the memory bank window.
1823 The definition of such region is then used by the linker to compute
1824 paging and addresses within the memory window.
1825 The following options are supported to control handling of GOT
1827 generation when linking for 68K targets.
1828 --got=type
1830 This option tells the linker which GOT generation scheme to use.
1831 type should be one of single, negative, multigot or target. For
1832 more information refer to the Info entry for ld.
1833
1835 You can change the behaviour of ld with the environment variables
1836 "GNUTARGET", "LDEMULATION" and "COLLECT_NO_DEMANGLE".
1837 "GNUTARGET" determines the input-file object format if you don't use -b
1839 (or its synonym --format). Its value should be one of the BFD names
1840 for an input format. If there is no "GNUTARGET" in the environment, ld
1841 uses the natural format of the target. If "GNUTARGET" is set to
1842 "default" then BFD attempts to discover the input format by examining
1843 binary input files; this method often succeeds, but there are potential
1844 ambiguities, since there is no method of ensuring that the magic number
1845 used to specify object-file formats is unique. However, the
1846 configuration procedure for BFD on each system places the conventional
1847 format for that system first in the search-list, so ambiguities are
1848 resolved in favor of convention.
1849 "LDEMULATION" determines the default emulation if you don't use the -m
1851 option. The emulation can affect various aspects of linker behaviour,
1852 particularly the default linker script. You can list the available
1853 emulations with the --verbose or -V options. If the -m option is not
1854 used, and the "LDEMULATION" environment variable is not defined, the
1855 default emulation depends upon how the linker was configured.
1856 Normally, the linker will default to demangling symbols. However, if
1858 "COLLECT_NO_DEMANGLE" is set in the environment, then it will default
1859 to not demangling symbols. This environment variable is used in a
1860 similar fashion by the "gcc" linker wrapper program. The default may
1861 be overridden by the --demangle and --no-demangle options.
1862
1864 ar(1), nm(1), objcopy(1), objdump(1), readelf(1) and the Info entries
1865 for binutils and ld.
1866
1868 Copyright (c) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
1869 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
1870 Permission is granted to copy, distribute and/or modify this document
1872 under the terms of the GNU Free Documentation License, Version 1.1 or
1873 any later version published by the Free Software Foundation; with no
1874 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
1875 Texts. A copy of the license is included in the section entitled "GNU
1876 Free Documentation License".
1877binutils-2.19.50.0.1 2009-07-28 LD(1)