1LD(1) GNU Development Tools LD(1)
2
6 ld - The GNU linker
7
9 ld [options] objfile ...
10
12 ld combines a number of object and archive files, relocates their data
13 and ties up symbol references. Usually the last step in compiling a
14 program is to run ld.
15 ld accepts Linker Command Language files written in a superset of
17 AT&T's Link Editor Command Language syntax, to provide explicit and
18 total control over the linking process.
19 This man page does not describe the command language; see the ld entry
21 in "info" for full details on the command language and on other aspects
22 of the GNU linker.
23 This version of ld uses the general purpose BFD libraries to operate on
25 object files. This allows ld to read, combine, and write object files
26 in many different formats---for example, COFF or "a.out". Different
27 formats may be linked together to produce any available kind of object
28 file.
29 Aside from its flexibility, the GNU linker is more helpful than other
31 linkers in providing diagnostic information. Many linkers abandon
32 execution immediately upon encountering an error; whenever possible, ld
33 continues executing, allowing you to identify other errors (or, in some
34 cases, to get an output file in spite of the error).
35 The GNU linker ld is meant to cover a broad range of situations, and to
37 be as compatible as possible with other linkers. As a result, you have
38 many choices to control its behavior.
39
41 The linker supports a plethora of command-line options, but in actual
42 practice few of them are used in any particular context. For instance,
43 a frequent use of ld is to link standard Unix object files on a
44 standard, supported Unix system. On such a system, to link a file
45 "hello.o":
46 ld -o <output> /lib/crt0.o hello.o -lc
48 This tells ld to produce a file called output as the result of linking
50 the file "/lib/crt0.o" with "hello.o" and the library "libc.a", which
51 will come from the standard search directories. (See the discussion of
52 the -l option below.)
53 Some of the command-line options to ld may be specified at any point in
55 the command line. However, options which refer to files, such as -l or
56 -T, cause the file to be read at the point at which the option appears
57 in the command line, relative to the object files and other file
58 options. Repeating non-file options with a different argument will
59 either have no further effect, or override prior occurrences (those
60 further to the left on the command line) of that option. Options which
61 may be meaningfully specified more than once are noted in the
62 descriptions below.
63 Non-option arguments are object files or archives which are to be
65 linked together. They may follow, precede, or be mixed in with
66 command-line options, except that an object file argument may not be
67 placed between an option and its argument.
68 Usually the linker is invoked with at least one object file, but you
70 can specify other forms of binary input files using -l, -R, and the
71 script command language. If no binary input files at all are
72 specified, the linker does not produce any output, and issues the
73 message No input files.
74 If the linker cannot recognize the format of an object file, it will
76 assume that it is a linker script. A script specified in this way
77 augments the main linker script used for the link (either the default
78 linker script or the one specified by using -T). This feature permits
79 the linker to link against a file which appears to be an object or an
80 archive, but actually merely defines some symbol values, or uses
81 "INPUT" or "GROUP" to load other objects. Specifying a script in this
82 way merely augments the main linker script, with the extra commands
83 placed after the main script; use the -T option to replace the default
84 linker script entirely, but note the effect of the "INSERT" command.
85 For options whose names are a single letter, option arguments must
87 either follow the option letter without intervening whitespace, or be
88 given as separate arguments immediately following the option that
89 requires them.
90 For options whose names are multiple letters, either one dash or two
92 can precede the option name; for example, -trace-symbol and
93 --trace-symbol are equivalent. Note---there is one exception to this
94 rule. Multiple letter options that start with a lower case 'o' can
95 only be preceded by two dashes. This is to reduce confusion with the
96 -o option. So for example -omagic sets the output file name to magic
97 whereas --omagic sets the NMAGIC flag on the output.
98 Arguments to multiple-letter options must either be separated from the
100 option name by an equals sign, or be given as separate arguments
101 immediately following the option that requires them. For example,
102 --trace-symbol foo and --trace-symbol=foo are equivalent. Unique
103 abbreviations of the names of multiple-letter options are accepted.
104 Note---if the linker is being invoked indirectly, via a compiler driver
106 (e.g. gcc) then all the linker command-line options should be prefixed
107 by -Wl, (or whatever is appropriate for the particular compiler driver)
108 like this:
109 gcc -Wl,--start-group foo.o bar.o -Wl,--end-group
111 This is important, because otherwise the compiler driver program may
113 silently drop the linker options, resulting in a bad link. Confusion
114 may also arise when passing options that require values through a
115 driver, as the use of a space between option and argument acts as a
116 separator, and causes the driver to pass only the option to the linker
117 and the argument to the compiler. In this case, it is simplest to use
118 the joined forms of both single- and multiple-letter options, such as:
119 gcc foo.o bar.o -Wl,-eENTRY -Wl,-Map=a.map
121 Here is a table of the generic command-line switches accepted by the
123 GNU linker:
124 @file
126 Read command-line options from file. The options read are inserted
127 in place of the original @file option. If file does not exist, or
128 cannot be read, then the option will be treated literally, and not
129 removed.
130 Options in file are separated by whitespace. A whitespace
132 character may be included in an option by surrounding the entire
133 option in either single or double quotes. Any character (including
134 a backslash) may be included by prefixing the character to be
135 included with a backslash. The file may itself contain additional
136 @file options; any such options will be processed recursively.
137 -a keyword
139 This option is supported for HP/UX compatibility. The keyword
140 argument must be one of the strings archive, shared, or default.
141 -aarchive is functionally equivalent to -Bstatic, and the other two
142 keywords are functionally equivalent to -Bdynamic. This option may
143 be used any number of times.
144 --audit AUDITLIB
146 Adds AUDITLIB to the "DT_AUDIT" entry of the dynamic section.
147 AUDITLIB is not checked for existence, nor will it use the
148 DT_SONAME specified in the library. If specified multiple times
149 "DT_AUDIT" will contain a colon separated list of audit interfaces
150 to use. If the linker finds an object with an audit entry while
151 searching for shared libraries, it will add a corresponding
152 "DT_DEPAUDIT" entry in the output file. This option is only
153 meaningful on ELF platforms supporting the rtld-audit interface.
154 -b input-format
156 --format=input-format
157 ld may be configured to support more than one kind of object file.
158 If your ld is configured this way, you can use the -b option to
159 specify the binary format for input object files that follow this
160 option on the command line. Even when ld is configured to support
161 alternative object formats, you don't usually need to specify this,
162 as ld should be configured to expect as a default input format the
163 most usual format on each machine. input-format is a text string,
164 the name of a particular format supported by the BFD libraries.
165 (You can list the available binary formats with objdump -i.)
166 You may want to use this option if you are linking files with an
168 unusual binary format. You can also use -b to switch formats
169 explicitly (when linking object files of different formats), by
170 including -b input-format before each group of object files in a
171 particular format.
172 The default format is taken from the environment variable
174 "GNUTARGET".
175 You can also define the input format from a script, using the
177 command "TARGET";
178 -c MRI-commandfile
180 --mri-script=MRI-commandfile
181 For compatibility with linkers produced by MRI, ld accepts script
182 files written in an alternate, restricted command language,
183 described in the MRI Compatible Script Files section of GNU ld
184 documentation. Introduce MRI script files with the option -c; use
185 the -T option to run linker scripts written in the general-purpose
186 ld scripting language. If MRI-cmdfile does not exist, ld looks for
187 it in the directories specified by any -L options.
188 -d
190 -dc
191 -dp These three options are equivalent; multiple forms are supported
192 for compatibility with other linkers. They assign space to common
193 symbols even if a relocatable output file is specified (with -r).
194 The script command "FORCE_COMMON_ALLOCATION" has the same effect.
195 --depaudit AUDITLIB
197 -P AUDITLIB
198 Adds AUDITLIB to the "DT_DEPAUDIT" entry of the dynamic section.
199 AUDITLIB is not checked for existence, nor will it use the
200 DT_SONAME specified in the library. If specified multiple times
201 "DT_DEPAUDIT" will contain a colon separated list of audit
202 interfaces to use. This option is only meaningful on ELF platforms
203 supporting the rtld-audit interface. The -P option is provided for
204 Solaris compatibility.
205 -e entry
207 --entry=entry
208 Use entry as the explicit symbol for beginning execution of your
209 program, rather than the default entry point. If there is no
210 symbol named entry, the linker will try to parse entry as a number,
211 and use that as the entry address (the number will be interpreted
212 in base 10; you may use a leading 0x for base 16, or a leading 0
213 for base 8).
214 --exclude-libs lib,lib,...
216 Specifies a list of archive libraries from which symbols should not
217 be automatically exported. The library names may be delimited by
218 commas or colons. Specifying "--exclude-libs ALL" excludes symbols
219 in all archive libraries from automatic export. This option is
220 available only for the i386 PE targeted port of the linker and for
221 ELF targeted ports. For i386 PE, symbols explicitly listed in a
222 .def file are still exported, regardless of this option. For ELF
223 targeted ports, symbols affected by this option will be treated as
224 hidden.
225 --exclude-modules-for-implib module,module,...
227 Specifies a list of object files or archive members, from which
228 symbols should not be automatically exported, but which should be
229 copied wholesale into the import library being generated during the
230 link. The module names may be delimited by commas or colons, and
231 must match exactly the filenames used by ld to open the files; for
232 archive members, this is simply the member name, but for object
233 files the name listed must include and match precisely any path
234 used to specify the input file on the linker's command-line. This
235 option is available only for the i386 PE targeted port of the
236 linker. Symbols explicitly listed in a .def file are still
237 exported, regardless of this option.
238 -E
240 --export-dynamic
241 --no-export-dynamic
242 When creating a dynamically linked executable, using the -E option
243 or the --export-dynamic option causes the linker to add all symbols
244 to the dynamic symbol table. The dynamic symbol table is the set
245 of symbols which are visible from dynamic objects at run time.
246 If you do not use either of these options (or use the
248 --no-export-dynamic option to restore the default behavior), the
249 dynamic symbol table will normally contain only those symbols which
250 are referenced by some dynamic object mentioned in the link.
251 If you use "dlopen" to load a dynamic object which needs to refer
253 back to the symbols defined by the program, rather than some other
254 dynamic object, then you will probably need to use this option when
255 linking the program itself.
256 You can also use the dynamic list to control what symbols should be
258 added to the dynamic symbol table if the output format supports it.
259 See the description of --dynamic-list.
260 Note that this option is specific to ELF targeted ports. PE
262 targets support a similar function to export all symbols from a DLL
263 or EXE; see the description of --export-all-symbols below.
264 -EB Link big-endian objects. This affects the default output format.
266 -EL Link little-endian objects. This affects the default output
268 format.
269 -f name
271 --auxiliary=name
272 When creating an ELF shared object, set the internal DT_AUXILIARY
273 field to the specified name. This tells the dynamic linker that
274 the symbol table of the shared object should be used as an
275 auxiliary filter on the symbol table of the shared object name.
276 If you later link a program against this filter object, then, when
278 you run the program, the dynamic linker will see the DT_AUXILIARY
279 field. If the dynamic linker resolves any symbols from the filter
280 object, it will first check whether there is a definition in the
281 shared object name. If there is one, it will be used instead of
282 the definition in the filter object. The shared object name need
283 not exist. Thus the shared object name may be used to provide an
284 alternative implementation of certain functions, perhaps for
285 debugging or for machine-specific performance.
286 This option may be specified more than once. The DT_AUXILIARY
288 entries will be created in the order in which they appear on the
289 command line.
290 -F name
292 --filter=name
293 When creating an ELF shared object, set the internal DT_FILTER
294 field to the specified name. This tells the dynamic linker that
295 the symbol table of the shared object which is being created should
296 be used as a filter on the symbol table of the shared object name.
297 If you later link a program against this filter object, then, when
299 you run the program, the dynamic linker will see the DT_FILTER
300 field. The dynamic linker will resolve symbols according to the
301 symbol table of the filter object as usual, but it will actually
302 link to the definitions found in the shared object name. Thus the
303 filter object can be used to select a subset of the symbols
304 provided by the object name.
305 Some older linkers used the -F option throughout a compilation
307 toolchain for specifying object-file format for both input and
308 output object files. The GNU linker uses other mechanisms for this
309 purpose: the -b, --format, --oformat options, the "TARGET" command
310 in linker scripts, and the "GNUTARGET" environment variable. The
311 GNU linker will ignore the -F option when not creating an ELF
312 shared object.
313 -fini=name
315 When creating an ELF executable or shared object, call NAME when
316 the executable or shared object is unloaded, by setting DT_FINI to
317 the address of the function. By default, the linker uses "_fini"
318 as the function to call.
319 -g Ignored. Provided for compatibility with other tools.
321 -G value
323 --gpsize=value
324 Set the maximum size of objects to be optimized using the GP
325 register to size. This is only meaningful for object file formats
326 such as MIPS ELF that support putting large and small objects into
327 different sections. This is ignored for other object file formats.
328 -h name
330 -soname=name
331 When creating an ELF shared object, set the internal DT_SONAME
332 field to the specified name. When an executable is linked with a
333 shared object which has a DT_SONAME field, then when the executable
334 is run the dynamic linker will attempt to load the shared object
335 specified by the DT_SONAME field rather than the using the file
336 name given to the linker.
337 -i Perform an incremental link (same as option -r).
339 -init=name
341 When creating an ELF executable or shared object, call NAME when
342 the executable or shared object is loaded, by setting DT_INIT to
343 the address of the function. By default, the linker uses "_init"
344 as the function to call.
345 -l namespec
347 --library=namespec
348 Add the archive or object file specified by namespec to the list of
349 files to link. This option may be used any number of times. If
350 namespec is of the form :filename, ld will search the library path
351 for a file called filename, otherwise it will search the library
352 path for a file called libnamespec.a.
353 On systems which support shared libraries, ld may also search for
355 files other than libnamespec.a. Specifically, on ELF and SunOS
356 systems, ld will search a directory for a library called
357 libnamespec.so before searching for one called libnamespec.a. (By
358 convention, a ".so" extension indicates a shared library.) Note
359 that this behavior does not apply to :filename, which always
360 specifies a file called filename.
361 The linker will search an archive only once, at the location where
363 it is specified on the command line. If the archive defines a
364 symbol which was undefined in some object which appeared before the
365 archive on the command line, the linker will include the
366 appropriate file(s) from the archive. However, an undefined symbol
367 in an object appearing later on the command line will not cause the
368 linker to search the archive again.
369 See the -( option for a way to force the linker to search archives
371 multiple times.
372 You may list the same archive multiple times on the command line.
374 This type of archive searching is standard for Unix linkers.
376 However, if you are using ld on AIX, note that it is different from
377 the behaviour of the AIX linker.
378 -L searchdir
380 --library-path=searchdir
381 Add path searchdir to the list of paths that ld will search for
382 archive libraries and ld control scripts. You may use this option
383 any number of times. The directories are searched in the order in
384 which they are specified on the command line. Directories
385 specified on the command line are searched before the default
386 directories. All -L options apply to all -l options, regardless of
387 the order in which the options appear. -L options do not affect
388 how ld searches for a linker script unless -T option is specified.
389 If searchdir begins with "=" or $SYSROOT, then this prefix will be
391 replaced by the sysroot prefix, controlled by the --sysroot option,
392 or specified when the linker is configured.
393 The default set of paths searched (without being specified with -L)
395 depends on which emulation mode ld is using, and in some cases also
396 on how it was configured.
397 The paths can also be specified in a link script with the
399 "SEARCH_DIR" command. Directories specified this way are searched
400 at the point in which the linker script appears in the command
401 line.
402 -m emulation
404 Emulate the emulation linker. You can list the available
405 emulations with the --verbose or -V options.
406 If the -m option is not used, the emulation is taken from the
408 "LDEMULATION" environment variable, if that is defined.
409 Otherwise, the default emulation depends upon how the linker was
411 configured.
412 -M
414 --print-map
415 Print a link map to the standard output. A link map provides
416 information about the link, including the following:
417 · Where object files are mapped into memory.
419 · How common symbols are allocated.
421 · All archive members included in the link, with a mention of the
423 symbol which caused the archive member to be brought in.
424 · The values assigned to symbols.
426 Note - symbols whose values are computed by an expression which
428 involves a reference to a previous value of the same symbol may
429 not have correct result displayed in the link map. This is
430 because the linker discards intermediate results and only
431 retains the final value of an expression. Under such
432 circumstances the linker will display the final value enclosed
433 by square brackets. Thus for example a linker script
434 containing:
435 foo = 1
437 foo = foo * 4
438 foo = foo + 8
439 will produce the following output in the link map if the -M
441 option is used:
442 0x00000001 foo = 0x1
444 [0x0000000c] foo = (foo * 0x4)
445 [0x0000000c] foo = (foo + 0x8)
446 See Expressions for more information about expressions in
448 linker scripts.
449 · How GNU properties are merged.
451 When the linker merges input .note.gnu.property sections into
453 one output .note.gnu.property section, some properties are
454 removed or updated. These actions are reported in the link
455 map. For example:
456 Removed property 0xc0000002 to merge foo.o (0x1) and bar.o (not found)
458 This indicates that property 0xc0000002 is removed from output
460 when merging properties in foo.o, whose property 0xc0000002
461 value is 0x1, and bar.o, which doesn't have property
462 0xc0000002.
463 Updated property 0xc0010001 (0x1) to merge foo.o (0x1) and bar.o (0x1)
465 This indicates that property 0xc0010001 value is updated to 0x1
467 in output when merging properties in foo.o, whose 0xc0010001
468 property value is 0x1, and bar.o, whose 0xc0010001 property
469 value is 0x1.
470 --print-map-discarded
472 --no-print-map-discarded
473 Print (or do not print) the list of discarded and garbage collected
474 sections in the link map. Enabled by default.
475 -n
477 --nmagic
478 Turn off page alignment of sections, and disable linking against
479 shared libraries. If the output format supports Unix style magic
480 numbers, mark the output as "NMAGIC".
481 -N
483 --omagic
484 Set the text and data sections to be readable and writable. Also,
485 do not page-align the data segment, and disable linking against
486 shared libraries. If the output format supports Unix style magic
487 numbers, mark the output as "OMAGIC". Note: Although a writable
488 text section is allowed for PE-COFF targets, it does not conform to
489 the format specification published by Microsoft.
490 --no-omagic
492 This option negates most of the effects of the -N option. It sets
493 the text section to be read-only, and forces the data segment to be
494 page-aligned. Note - this option does not enable linking against
495 shared libraries. Use -Bdynamic for this.
496 -o output
498 --output=output
499 Use output as the name for the program produced by ld; if this
500 option is not specified, the name a.out is used by default. The
501 script command "OUTPUT" can also specify the output file name.
502 -O level
504 If level is a numeric values greater than zero ld optimizes the
505 output. This might take significantly longer and therefore
506 probably should only be enabled for the final binary. At the
507 moment this option only affects ELF shared library generation.
508 Future releases of the linker may make more use of this option.
509 Also currently there is no difference in the linker's behaviour for
510 different non-zero values of this option. Again this may change
511 with future releases.
512 -plugin name
514 Involve a plugin in the linking process. The name parameter is the
515 absolute filename of the plugin. Usually this parameter is
516 automatically added by the complier, when using link time
517 optimization, but users can also add their own plugins if they so
518 wish.
519 Note that the location of the compiler originated plugins is
521 different from the place where the ar, nm and ranlib programs
522 search for their plugins. In order for those commands to make use
523 of a compiler based plugin it must first be copied into the
524 ${libdir}/bfd-plugins directory. All gcc based linker plugins are
525 backward compatible, so it is sufficient to just copy in the newest
526 one.
527 --push-state
529 The --push-state allows to preserve the current state of the flags
530 which govern the input file handling so that they can all be
531 restored with one corresponding --pop-state option.
532 The option which are covered are: -Bdynamic, -Bstatic, -dn, -dy,
534 -call_shared, -non_shared, -static, -N, -n, --whole-archive,
535 --no-whole-archive, -r, -Ur, --copy-dt-needed-entries,
536 --no-copy-dt-needed-entries, --as-needed, --no-as-needed, and -a.
537 One target for this option are specifications for pkg-config. When
539 used with the --libs option all possibly needed libraries are
540 listed and then possibly linked with all the time. It is better to
541 return something as follows:
542 -Wl,--push-state,--as-needed -libone -libtwo -Wl,--pop-state
544 --pop-state
546 Undoes the effect of --push-state, restores the previous values of
547 the flags governing input file handling.
548 -q
550 --emit-relocs
551 Leave relocation sections and contents in fully linked executables.
552 Post link analysis and optimization tools may need this information
553 in order to perform correct modifications of executables. This
554 results in larger executables.
555 This option is currently only supported on ELF platforms.
557 --force-dynamic
559 Force the output file to have dynamic sections. This option is
560 specific to VxWorks targets.
561 -r
563 --relocatable
564 Generate relocatable output---i.e., generate an output file that
565 can in turn serve as input to ld. This is often called partial
566 linking. As a side effect, in environments that support standard
567 Unix magic numbers, this option also sets the output file's magic
568 number to "OMAGIC". If this option is not specified, an absolute
569 file is produced. When linking C++ programs, this option will not
570 resolve references to constructors; to do that, use -Ur.
571 When an input file does not have the same format as the output
573 file, partial linking is only supported if that input file does not
574 contain any relocations. Different output formats can have further
575 restrictions; for example some "a.out"-based formats do not support
576 partial linking with input files in other formats at all.
577 This option does the same thing as -i.
579 -R filename
581 --just-symbols=filename
582 Read symbol names and their addresses from filename, but do not
583 relocate it or include it in the output. This allows your output
584 file to refer symbolically to absolute locations of memory defined
585 in other programs. You may use this option more than once.
586 For compatibility with other ELF linkers, if the -R option is
588 followed by a directory name, rather than a file name, it is
589 treated as the -rpath option.
590 -s
592 --strip-all
593 Omit all symbol information from the output file.
594 -S
596 --strip-debug
597 Omit debugger symbol information (but not all symbols) from the
598 output file.
599 --strip-discarded
601 --no-strip-discarded
602 Omit (or do not omit) global symbols defined in discarded sections.
603 Enabled by default.
604 -t
606 --trace
607 Print the names of the input files as ld processes them. If -t is
608 given twice then members within archives are also printed. -t
609 output is useful to generate a list of all the object files and
610 scripts involved in linking, for example, when packaging files for
611 a linker bug report.
612 -T scriptfile
614 --script=scriptfile
615 Use scriptfile as the linker script. This script replaces ld's
616 default linker script (rather than adding to it), so commandfile
617 must specify everything necessary to describe the output file.
618 If scriptfile does not exist in the current directory, "ld" looks
619 for it in the directories specified by any preceding -L options.
620 Multiple -T options accumulate.
621 -dT scriptfile
623 --default-script=scriptfile
624 Use scriptfile as the default linker script.
625 This option is similar to the --script option except that
627 processing of the script is delayed until after the rest of the
628 command line has been processed. This allows options placed after
629 the --default-script option on the command line to affect the
630 behaviour of the linker script, which can be important when the
631 linker command line cannot be directly controlled by the user. (eg
632 because the command line is being constructed by another tool, such
633 as gcc).
634 -u symbol
636 --undefined=symbol
637 Force symbol to be entered in the output file as an undefined
638 symbol. Doing this may, for example, trigger linking of additional
639 modules from standard libraries. -u may be repeated with different
640 option arguments to enter additional undefined symbols. This
641 option is equivalent to the "EXTERN" linker script command.
642 If this option is being used to force additional modules to be
644 pulled into the link, and if it is an error for the symbol to
645 remain undefined, then the option --require-defined should be used
646 instead.
647 --require-defined=symbol
649 Require that symbol is defined in the output file. This option is
650 the same as option --undefined except that if symbol is not defined
651 in the output file then the linker will issue an error and exit.
652 The same effect can be achieved in a linker script by using
653 "EXTERN", "ASSERT" and "DEFINED" together. This option can be used
654 multiple times to require additional symbols.
655 -Ur For anything other than C++ programs, this option is equivalent to
657 -r: it generates relocatable output---i.e., an output file that can
658 in turn serve as input to ld. When linking C++ programs, -Ur does
659 resolve references to constructors, unlike -r. It does not work to
660 use -Ur on files that were themselves linked with -Ur; once the
661 constructor table has been built, it cannot be added to. Use -Ur
662 only for the last partial link, and -r for the others.
663 --orphan-handling=MODE
665 Control how orphan sections are handled. An orphan section is one
666 not specifically mentioned in a linker script.
667 MODE can have any of the following values:
669 "place"
671 Orphan sections are placed into a suitable output section
672 following the strategy described in Orphan Sections. The
673 option --unique also affects how sections are placed.
674 "discard"
676 All orphan sections are discarded, by placing them in the
677 /DISCARD/ section.
678 "warn"
680 The linker will place the orphan section as for "place" and
681 also issue a warning.
682 "error"
684 The linker will exit with an error if any orphan section is
685 found.
686 The default if --orphan-handling is not given is "place".
688 --unique[=SECTION]
690 Creates a separate output section for every input section matching
691 SECTION, or if the optional wildcard SECTION argument is missing,
692 for every orphan input section. An orphan section is one not
693 specifically mentioned in a linker script. You may use this option
694 multiple times on the command line; It prevents the normal merging
695 of input sections with the same name, overriding output section
696 assignments in a linker script.
697 -v
699 --version
700 -V Display the version number for ld. The -V option also lists the
701 supported emulations.
702 -x
704 --discard-all
705 Delete all local symbols.
706 -X
708 --discard-locals
709 Delete all temporary local symbols. (These symbols start with
710 system-specific local label prefixes, typically .L for ELF systems
711 or L for traditional a.out systems.)
712 -y symbol
714 --trace-symbol=symbol
715 Print the name of each linked file in which symbol appears. This
716 option may be given any number of times. On many systems it is
717 necessary to prepend an underscore.
718 This option is useful when you have an undefined symbol in your
720 link but don't know where the reference is coming from.
721 -Y path
723 Add path to the default library search path. This option exists
724 for Solaris compatibility.
725 -z keyword
727 The recognized keywords are:
728 bndplt
730 Always generate BND prefix in PLT entries. Supported for
731 Linux/x86_64.
732 call-nop=prefix-addr
734 call-nop=suffix-nop
735 call-nop=prefix-byte
736 call-nop=suffix-byte
737 Specify the 1-byte "NOP" padding when transforming indirect
738 call to a locally defined function, foo, via its GOT slot.
739 call-nop=prefix-addr generates "0x67 call foo".
740 call-nop=suffix-nop generates "call foo 0x90".
741 call-nop=prefix-byte generates "byte call foo".
742 call-nop=suffix-byte generates "call foo byte". Supported for
743 i386 and x86_64.
744 cet-report=none
746 cet-report=warning
747 cet-report=error
748 Specify how to report the missing
749 GNU_PROPERTY_X86_FEATURE_1_IBT and
750 GNU_PROPERTY_X86_FEATURE_1_SHSTK properties in input
751 .note.gnu.property section. cet-report=none, which is the
752 default, will make the linker not report missing properties in
753 input files. cet-report=warning will make the linker issue a
754 warning for missing properties in input files.
755 cet-report=error will make the linker issue an error for
756 missing properties in input files. Note that ibt will turn off
757 the missing GNU_PROPERTY_X86_FEATURE_1_IBT property report and
758 shstk will turn off the missing
759 GNU_PROPERTY_X86_FEATURE_1_SHSTK property report. Supported
760 for Linux/i386 and Linux/x86_64.
761 combreloc
763 nocombreloc
764 Combine multiple dynamic relocation sections and sort to
765 improve dynamic symbol lookup caching. Do not do this if
766 nocombreloc.
767 common
769 nocommon
770 Generate common symbols with STT_COMMON type during a
771 relocatable link. Use STT_OBJECT type if nocommon.
772 common-page-size=value
774 Set the page size most commonly used to value. Memory image
775 layout will be optimized to minimize memory pages if the system
776 is using pages of this size.
777 defs
779 Report unresolved symbol references from regular object files.
780 This is done even if the linker is creating a non-symbolic
781 shared library. This option is the inverse of -z undefs.
782 dynamic-undefined-weak
784 nodynamic-undefined-weak
785 Make undefined weak symbols dynamic when building a dynamic
786 object, if they are referenced from a regular object file and
787 not forced local by symbol visibility or versioning. Do not
788 make them dynamic if nodynamic-undefined-weak. If neither
789 option is given, a target may default to either option being in
790 force, or make some other selection of undefined weak symbols
791 dynamic. Not all targets support these options.
792 execstack
794 Marks the object as requiring executable stack.
795 global
797 This option is only meaningful when building a shared object.
798 It makes the symbols defined by this shared object available
799 for symbol resolution of subsequently loaded libraries.
800 globalaudit
802 This option is only meaningful when building a dynamic
803 executable. This option marks the executable as requiring
804 global auditing by setting the "DF_1_GLOBAUDIT" bit in the
805 "DT_FLAGS_1" dynamic tag. Global auditing requires that any
806 auditing library defined via the --depaudit or -P command-line
807 options be run for all dynamic objects loaded by the
808 application.
809 ibtplt
811 Generate Intel Indirect Branch Tracking (IBT) enabled PLT
812 entries. Supported for Linux/i386 and Linux/x86_64.
813 ibt Generate GNU_PROPERTY_X86_FEATURE_1_IBT in .note.gnu.property
815 section to indicate compatibility with IBT. This also implies
816 ibtplt. Supported for Linux/i386 and Linux/x86_64.
817 initfirst
819 This option is only meaningful when building a shared object.
820 It marks the object so that its runtime initialization will
821 occur before the runtime initialization of any other objects
822 brought into the process at the same time. Similarly the
823 runtime finalization of the object will occur after the runtime
824 finalization of any other objects.
825 interpose
827 Specify that the dynamic loader should modify its symbol search
828 order so that symbols in this shared library interpose all
829 other shared libraries not so marked.
830 lazy
832 When generating an executable or shared library, mark it to
833 tell the dynamic linker to defer function call resolution to
834 the point when the function is called (lazy binding), rather
835 than at load time. Lazy binding is the default.
836 loadfltr
838 Specify that the object's filters be processed immediately at
839 runtime.
840 max-page-size=value
842 Set the maximum memory page size supported to value.
843 muldefs
845 Allow multiple definitions.
846 nocopyreloc
848 Disable linker generated .dynbss variables used in place of
849 variables defined in shared libraries. May result in dynamic
850 text relocations.
851 nodefaultlib
853 Specify that the dynamic loader search for dependencies of this
854 object should ignore any default library search paths.
855 nodelete
857 Specify that the object shouldn't be unloaded at runtime.
858 nodlopen
860 Specify that the object is not available to "dlopen".
861 nodump
863 Specify that the object can not be dumped by "dldump".
864 noexecstack
866 Marks the object as not requiring executable stack.
867 noextern-protected-data
869 Don't treat protected data symbols as external when building a
870 shared library. This option overrides the linker backend
871 default. It can be used to work around incorrect relocations
872 against protected data symbols generated by compiler. Updates
873 on protected data symbols by another module aren't visible to
874 the resulting shared library. Supported for i386 and x86-64.
875 noreloc-overflow
877 Disable relocation overflow check. This can be used to disable
878 relocation overflow check if there will be no dynamic
879 relocation overflow at run-time. Supported for x86_64.
880 now When generating an executable or shared library, mark it to
882 tell the dynamic linker to resolve all symbols when the program
883 is started, or when the shared library is loaded by dlopen,
884 instead of deferring function call resolution to the point when
885 the function is first called.
886 origin
888 Specify that the object requires $ORIGIN handling in paths.
889 relro
891 norelro
892 Create an ELF "PT_GNU_RELRO" segment header in the object.
893 This specifies a memory segment that should be made read-only
894 after relocation, if supported. Specifying common-page-size
895 smaller than the system page size will render this protection
896 ineffective. Don't create an ELF "PT_GNU_RELRO" segment if
897 norelro.
898 separate-code
900 noseparate-code
901 Create separate code "PT_LOAD" segment header in the object.
902 This specifies a memory segment that should contain only
903 instructions and must be in wholly disjoint pages from any
904 other data. Don't create separate code "PT_LOAD" segment if
905 noseparate-code is used.
906 shstk
908 Generate GNU_PROPERTY_X86_FEATURE_1_SHSTK in .note.gnu.property
909 section to indicate compatibility with Intel Shadow Stack.
910 Supported for Linux/i386 and Linux/x86_64.
911 stack-size=value
913 Specify a stack size for an ELF "PT_GNU_STACK" segment.
914 Specifying zero will override any default non-zero sized
915 "PT_GNU_STACK" segment creation.
916 text
918 notext
919 textoff
920 Report an error if DT_TEXTREL is set, i.e., if the binary has
921 dynamic relocations in read-only sections. Don't report an
922 error if notext or textoff.
923 undefs
925 Do not report unresolved symbol references from regular object
926 files, either when creating an executable, or when creating a
927 shared library. This option is the inverse of -z defs.
928 Other keywords are ignored for Solaris compatibility.
930 -( archives -)
932 --start-group archives --end-group
933 The archives should be a list of archive files. They may be either
934 explicit file names, or -l options.
935 The specified archives are searched repeatedly until no new
937 undefined references are created. Normally, an archive is searched
938 only once in the order that it is specified on the command line.
939 If a symbol in that archive is needed to resolve an undefined
940 symbol referred to by an object in an archive that appears later on
941 the command line, the linker would not be able to resolve that
942 reference. By grouping the archives, they will all be searched
943 repeatedly until all possible references are resolved.
944 Using this option has a significant performance cost. It is best
946 to use it only when there are unavoidable circular references
947 between two or more archives.
948 --accept-unknown-input-arch
950 --no-accept-unknown-input-arch
951 Tells the linker to accept input files whose architecture cannot be
952 recognised. The assumption is that the user knows what they are
953 doing and deliberately wants to link in these unknown input files.
954 This was the default behaviour of the linker, before release 2.14.
955 The default behaviour from release 2.14 onwards is to reject such
956 input files, and so the --accept-unknown-input-arch option has been
957 added to restore the old behaviour.
958 --as-needed
960 --no-as-needed
961 This option affects ELF DT_NEEDED tags for dynamic libraries
962 mentioned on the command line after the --as-needed option.
963 Normally the linker will add a DT_NEEDED tag for each dynamic
964 library mentioned on the command line, regardless of whether the
965 library is actually needed or not. --as-needed causes a DT_NEEDED
966 tag to only be emitted for a library that at that point in the link
967 satisfies a non-weak undefined symbol reference from a regular
968 object file or, if the library is not found in the DT_NEEDED lists
969 of other needed libraries, a non-weak undefined symbol reference
970 from another needed dynamic library. Object files or libraries
971 appearing on the command line after the library in question do not
972 affect whether the library is seen as needed. This is similar to
973 the rules for extraction of object files from archives.
974 --no-as-needed restores the default behaviour.
975 --add-needed
977 --no-add-needed
978 These two options have been deprecated because of the similarity of
979 their names to the --as-needed and --no-as-needed options. They
980 have been replaced by --copy-dt-needed-entries and
981 --no-copy-dt-needed-entries.
982 -assert keyword
984 This option is ignored for SunOS compatibility.
985 -Bdynamic
987 -dy
988 -call_shared
989 Link against dynamic libraries. This is only meaningful on
990 platforms for which shared libraries are supported. This option is
991 normally the default on such platforms. The different variants of
992 this option are for compatibility with various systems. You may
993 use this option multiple times on the command line: it affects
994 library searching for -l options which follow it.
995 -Bgroup
997 Set the "DF_1_GROUP" flag in the "DT_FLAGS_1" entry in the dynamic
998 section. This causes the runtime linker to handle lookups in this
999 object and its dependencies to be performed only inside the group.
1000 --unresolved-symbols=report-all is implied. This option is only
1001 meaningful on ELF platforms which support shared libraries.
1002 -Bstatic
1004 -dn
1005 -non_shared
1006 -static
1007 Do not link against shared libraries. This is only meaningful on
1008 platforms for which shared libraries are supported. The different
1009 variants of this option are for compatibility with various systems.
1010 You may use this option multiple times on the command line: it
1011 affects library searching for -l options which follow it. This
1012 option also implies --unresolved-symbols=report-all. This option
1013 can be used with -shared. Doing so means that a shared library is
1014 being created but that all of the library's external references
1015 must be resolved by pulling in entries from static libraries.
1016 -Bsymbolic
1018 When creating a shared library, bind references to global symbols
1019 to the definition within the shared library, if any. Normally, it
1020 is possible for a program linked against a shared library to
1021 override the definition within the shared library. This option is
1022 only meaningful on ELF platforms which support shared libraries.
1023 -Bsymbolic-functions
1025 When creating a shared library, bind references to global function
1026 symbols to the definition within the shared library, if any. This
1027 option is only meaningful on ELF platforms which support shared
1028 libraries.
1029 --dynamic-list=dynamic-list-file
1031 Specify the name of a dynamic list file to the linker. This is
1032 typically used when creating shared libraries to specify a list of
1033 global symbols whose references shouldn't be bound to the
1034 definition within the shared library, or creating dynamically
1035 linked executables to specify a list of symbols which should be
1036 added to the symbol table in the executable. This option is only
1037 meaningful on ELF platforms which support shared libraries.
1038 The format of the dynamic list is the same as the version node
1040 without scope and node name. See VERSION for more information.
1041 --dynamic-list-data
1043 Include all global data symbols to the dynamic list.
1044 --dynamic-list-cpp-new
1046 Provide the builtin dynamic list for C++ operator new and delete.
1047 It is mainly useful for building shared libstdc++.
1048 --dynamic-list-cpp-typeinfo
1050 Provide the builtin dynamic list for C++ runtime type
1051 identification.
1052 --check-sections
1054 --no-check-sections
1055 Asks the linker not to check section addresses after they have been
1056 assigned to see if there are any overlaps. Normally the linker
1057 will perform this check, and if it finds any overlaps it will
1058 produce suitable error messages. The linker does know about, and
1059 does make allowances for sections in overlays. The default
1060 behaviour can be restored by using the command-line switch
1061 --check-sections. Section overlap is not usually checked for
1062 relocatable links. You can force checking in that case by using
1063 the --check-sections option.
1064 --copy-dt-needed-entries
1066 --no-copy-dt-needed-entries
1067 This option affects the treatment of dynamic libraries referred to
1068 by DT_NEEDED tags inside ELF dynamic libraries mentioned on the
1069 command line. Normally the linker won't add a DT_NEEDED tag to the
1070 output binary for each library mentioned in a DT_NEEDED tag in an
1071 input dynamic library. With --copy-dt-needed-entries specified on
1072 the command line however any dynamic libraries that follow it will
1073 have their DT_NEEDED entries added. The default behaviour can be
1074 restored with --no-copy-dt-needed-entries.
1075 This option also has an effect on the resolution of symbols in
1077 dynamic libraries. With --copy-dt-needed-entries dynamic libraries
1078 mentioned on the command line will be recursively searched,
1079 following their DT_NEEDED tags to other libraries, in order to
1080 resolve symbols required by the output binary. With the default
1081 setting however the searching of dynamic libraries that follow it
1082 will stop with the dynamic library itself. No DT_NEEDED links will
1083 be traversed to resolve symbols.
1084 --cref
1086 Output a cross reference table. If a linker map file is being
1087 generated, the cross reference table is printed to the map file.
1088 Otherwise, it is printed on the standard output.
1089 The format of the table is intentionally simple, so that it may be
1091 easily processed by a script if necessary. The symbols are printed
1092 out, sorted by name. For each symbol, a list of file names is
1093 given. If the symbol is defined, the first file listed is the
1094 location of the definition. If the symbol is defined as a common
1095 value then any files where this happens appear next. Finally any
1096 files that reference the symbol are listed.
1097 --no-define-common
1099 This option inhibits the assignment of addresses to common symbols.
1100 The script command "INHIBIT_COMMON_ALLOCATION" has the same effect.
1101 The --no-define-common option allows decoupling the decision to
1103 assign addresses to Common symbols from the choice of the output
1104 file type; otherwise a non-Relocatable output type forces assigning
1105 addresses to Common symbols. Using --no-define-common allows
1106 Common symbols that are referenced from a shared library to be
1107 assigned addresses only in the main program. This eliminates the
1108 unused duplicate space in the shared library, and also prevents any
1109 possible confusion over resolving to the wrong duplicate when there
1110 are many dynamic modules with specialized search paths for runtime
1111 symbol resolution.
1112 --force-group-allocation
1114 This option causes the linker to place section group members like
1115 normal input sections, and to delete the section groups. This is
1116 the default behaviour for a final link but this option can be used
1117 to change the behaviour of a relocatable link (-r). The script
1118 command "FORCE_GROUP_ALLOCATION" has the same effect.
1119 --defsym=symbol=expression
1121 Create a global symbol in the output file, containing the absolute
1122 address given by expression. You may use this option as many times
1123 as necessary to define multiple symbols in the command line. A
1124 limited form of arithmetic is supported for the expression in this
1125 context: you may give a hexadecimal constant or the name of an
1126 existing symbol, or use "+" and "-" to add or subtract hexadecimal
1127 constants or symbols. If you need more elaborate expressions,
1128 consider using the linker command language from a script. Note:
1129 there should be no white space between symbol, the equals sign
1130 ("="), and expression.
1131 --demangle[=style]
1133 --no-demangle
1134 These options control whether to demangle symbol names in error
1135 messages and other output. When the linker is told to demangle, it
1136 tries to present symbol names in a readable fashion: it strips
1137 leading underscores if they are used by the object file format, and
1138 converts C++ mangled symbol names into user readable names.
1139 Different compilers have different mangling styles. The optional
1140 demangling style argument can be used to choose an appropriate
1141 demangling style for your compiler. The linker will demangle by
1142 default unless the environment variable COLLECT_NO_DEMANGLE is set.
1143 These options may be used to override the default.
1144 -Ifile
1146 --dynamic-linker=file
1147 Set the name of the dynamic linker. This is only meaningful when
1148 generating dynamically linked ELF executables. The default dynamic
1149 linker is normally correct; don't use this unless you know what you
1150 are doing.
1151 --no-dynamic-linker
1153 When producing an executable file, omit the request for a dynamic
1154 linker to be used at load-time. This is only meaningful for ELF
1155 executables that contain dynamic relocations, and usually requires
1156 entry point code that is capable of processing these relocations.
1157 --embedded-relocs
1159 This option is similar to the --emit-relocs option except that the
1160 relocs are stored in a target-specific section. This option is
1161 only supported by the BFIN, CR16 and M68K targets.
1162 --disable-multiple-abs-defs
1164 Do not allow multiple definitions with symbols included in filename
1165 invoked by -R or --just-symbols
1166 --fatal-warnings
1168 --no-fatal-warnings
1169 Treat all warnings as errors. The default behaviour can be
1170 restored with the option --no-fatal-warnings.
1171 --force-exe-suffix
1173 Make sure that an output file has a .exe suffix.
1174 If a successfully built fully linked output file does not have a
1176 ".exe" or ".dll" suffix, this option forces the linker to copy the
1177 output file to one of the same name with a ".exe" suffix. This
1178 option is useful when using unmodified Unix makefiles on a
1179 Microsoft Windows host, since some versions of Windows won't run an
1180 image unless it ends in a ".exe" suffix.
1181 --gc-sections
1183 --no-gc-sections
1184 Enable garbage collection of unused input sections. It is ignored
1185 on targets that do not support this option. The default behaviour
1186 (of not performing this garbage collection) can be restored by
1187 specifying --no-gc-sections on the command line. Note that garbage
1188 collection for COFF and PE format targets is supported, but the
1189 implementation is currently considered to be experimental.
1190 --gc-sections decides which input sections are used by examining
1192 symbols and relocations. The section containing the entry symbol
1193 and all sections containing symbols undefined on the command-line
1194 will be kept, as will sections containing symbols referenced by
1195 dynamic objects. Note that when building shared libraries, the
1196 linker must assume that any visible symbol is referenced. Once
1197 this initial set of sections has been determined, the linker
1198 recursively marks as used any section referenced by their
1199 relocations. See --entry, --undefined, and --gc-keep-exported.
1200 This option can be set when doing a partial link (enabled with
1202 option -r). In this case the root of symbols kept must be
1203 explicitly specified either by one of the options --entry,
1204 --undefined, or --gc-keep-exported or by a "ENTRY" command in the
1205 linker script.
1206 --print-gc-sections
1208 --no-print-gc-sections
1209 List all sections removed by garbage collection. The listing is
1210 printed on stderr. This option is only effective if garbage
1211 collection has been enabled via the --gc-sections) option. The
1212 default behaviour (of not listing the sections that are removed)
1213 can be restored by specifying --no-print-gc-sections on the command
1214 line.
1215 --gc-keep-exported
1217 When --gc-sections is enabled, this option prevents garbage
1218 collection of unused input sections that contain global symbols
1219 having default or protected visibility. This option is intended to
1220 be used for executables where unreferenced sections would otherwise
1221 be garbage collected regardless of the external visibility of
1222 contained symbols. Note that this option has no effect when
1223 linking shared objects since it is already the default behaviour.
1224 This option is only supported for ELF format targets.
1225 --print-output-format
1227 Print the name of the default output format (perhaps influenced by
1228 other command-line options). This is the string that would appear
1229 in an "OUTPUT_FORMAT" linker script command.
1230 --print-memory-usage
1232 Print used size, total size and used size of memory regions created
1233 with the MEMORY command. This is useful on embedded targets to
1234 have a quick view of amount of free memory. The format of the
1235 output has one headline and one line per region. It is both human
1236 readable and easily parsable by tools. Here is an example of an
1237 output:
1238 Memory region Used Size Region Size %age Used
1240 ROM: 256 KB 1 MB 25.00%
1241 RAM: 32 B 2 GB 0.00%
1242 --help
1244 Print a summary of the command-line options on the standard output
1245 and exit.
1246 --target-help
1248 Print a summary of all target-specific options on the standard
1249 output and exit.
1250 -Map=mapfile
1252 Print a link map to the file mapfile. See the description of the
1253 -M option, above.
1254 --no-keep-memory
1256 ld normally optimizes for speed over memory usage by caching the
1257 symbol tables of input files in memory. This option tells ld to
1258 instead optimize for memory usage, by rereading the symbol tables
1259 as necessary. This may be required if ld runs out of memory space
1260 while linking a large executable.
1261 --no-undefined
1263 -z defs
1264 Report unresolved symbol references from regular object files.
1265 This is done even if the linker is creating a non-symbolic shared
1266 library. The switch --[no-]allow-shlib-undefined controls the
1267 behaviour for reporting unresolved references found in shared
1268 libraries being linked in.
1269 The effects of this option can be reverted by using "-z undefs".
1271 --allow-multiple-definition
1273 -z muldefs
1274 Normally when a symbol is defined multiple times, the linker will
1275 report a fatal error. These options allow multiple definitions and
1276 the first definition will be used.
1277 --allow-shlib-undefined
1279 --no-allow-shlib-undefined
1280 Allows or disallows undefined symbols in shared libraries. This
1281 switch is similar to --no-undefined except that it determines the
1282 behaviour when the undefined symbols are in a shared library rather
1283 than a regular object file. It does not affect how undefined
1284 symbols in regular object files are handled.
1285 The default behaviour is to report errors for any undefined symbols
1287 referenced in shared libraries if the linker is being used to
1288 create an executable, but to allow them if the linker is being used
1289 to create a shared library.
1290 The reasons for allowing undefined symbol references in shared
1292 libraries specified at link time are that:
1293 · A shared library specified at link time may not be the same as
1295 the one that is available at load time, so the symbol might
1296 actually be resolvable at load time.
1297 · There are some operating systems, eg BeOS and HPPA, where
1299 undefined symbols in shared libraries are normal.
1300 The BeOS kernel for example patches shared libraries at load
1302 time to select whichever function is most appropriate for the
1303 current architecture. This is used, for example, to
1304 dynamically select an appropriate memset function.
1305 --no-undefined-version
1307 Normally when a symbol has an undefined version, the linker will
1308 ignore it. This option disallows symbols with undefined version and
1309 a fatal error will be issued instead.
1310 --default-symver
1312 Create and use a default symbol version (the soname) for
1313 unversioned exported symbols.
1314 --default-imported-symver
1316 Create and use a default symbol version (the soname) for
1317 unversioned imported symbols.
1318 --no-warn-mismatch
1320 Normally ld will give an error if you try to link together input
1321 files that are mismatched for some reason, perhaps because they
1322 have been compiled for different processors or for different
1323 endiannesses. This option tells ld that it should silently permit
1324 such possible errors. This option should only be used with care,
1325 in cases when you have taken some special action that ensures that
1326 the linker errors are inappropriate.
1327 --no-warn-search-mismatch
1329 Normally ld will give a warning if it finds an incompatible library
1330 during a library search. This option silences the warning.
1331 --no-whole-archive
1333 Turn off the effect of the --whole-archive option for subsequent
1334 archive files.
1335 --noinhibit-exec
1337 Retain the executable output file whenever it is still usable.
1338 Normally, the linker will not produce an output file if it
1339 encounters errors during the link process; it exits without writing
1340 an output file when it issues any error whatsoever.
1341 -nostdlib
1343 Only search library directories explicitly specified on the command
1344 line. Library directories specified in linker scripts (including
1345 linker scripts specified on the command line) are ignored.
1346 --oformat=output-format
1348 ld may be configured to support more than one kind of object file.
1349 If your ld is configured this way, you can use the --oformat option
1350 to specify the binary format for the output object file. Even when
1351 ld is configured to support alternative object formats, you don't
1352 usually need to specify this, as ld should be configured to produce
1353 as a default output format the most usual format on each machine.
1354 output-format is a text string, the name of a particular format
1355 supported by the BFD libraries. (You can list the available binary
1356 formats with objdump -i.) The script command "OUTPUT_FORMAT" can
1357 also specify the output format, but this option overrides it.
1358 --out-implib file
1360 Create an import library in file corresponding to the executable
1361 the linker is generating (eg. a DLL or ELF program). This import
1362 library (which should be called "*.dll.a" or "*.a" for DLLs) may be
1363 used to link clients against the generated executable; this
1364 behaviour makes it possible to skip a separate import library
1365 creation step (eg. "dlltool" for DLLs). This option is only
1366 available for the i386 PE and ELF targetted ports of the linker.
1367 -pie
1369 --pic-executable
1370 Create a position independent executable. This is currently only
1371 supported on ELF platforms. Position independent executables are
1372 similar to shared libraries in that they are relocated by the
1373 dynamic linker to the virtual address the OS chooses for them
1374 (which can vary between invocations). Like normal dynamically
1375 linked executables they can be executed and symbols defined in the
1376 executable cannot be overridden by shared libraries.
1377 -qmagic
1379 This option is ignored for Linux compatibility.
1380 -Qy This option is ignored for SVR4 compatibility.
1382 --relax
1384 --no-relax
1385 An option with machine dependent effects. This option is only
1386 supported on a few targets.
1387 On some platforms the --relax option performs target-specific,
1389 global optimizations that become possible when the linker resolves
1390 addressing in the program, such as relaxing address modes,
1391 synthesizing new instructions, selecting shorter version of current
1392 instructions, and combining constant values.
1393 On some platforms these link time global optimizations may make
1395 symbolic debugging of the resulting executable impossible. This is
1396 known to be the case for the Matsushita MN10200 and MN10300 family
1397 of processors.
1398 On platforms where this is not supported, --relax is accepted, but
1400 ignored.
1401 On platforms where --relax is accepted the option --no-relax can be
1403 used to disable the feature.
1404 --retain-symbols-file=filename
1406 Retain only the symbols listed in the file filename, discarding all
1407 others. filename is simply a flat file, with one symbol name per
1408 line. This option is especially useful in environments (such as
1409 VxWorks) where a large global symbol table is accumulated
1410 gradually, to conserve run-time memory.
1411 --retain-symbols-file does not discard undefined symbols, or
1413 symbols needed for relocations.
1414 You may only specify --retain-symbols-file once in the command
1416 line. It overrides -s and -S.
1417 -rpath=dir
1419 Add a directory to the runtime library search path. This is used
1420 when linking an ELF executable with shared objects. All -rpath
1421 arguments are concatenated and passed to the runtime linker, which
1422 uses them to locate shared objects at runtime.
1423 The -rpath option is also used when locating shared objects which
1425 are needed by shared objects explicitly included in the link; see
1426 the description of the -rpath-link option. Searching -rpath in
1427 this way is only supported by native linkers and cross linkers
1428 which have been configured with the --with-sysroot option.
1429 If -rpath is not used when linking an ELF executable, the contents
1431 of the environment variable "LD_RUN_PATH" will be used if it is
1432 defined.
1433 The -rpath option may also be used on SunOS. By default, on SunOS,
1435 the linker will form a runtime search path out of all the -L
1436 options it is given. If a -rpath option is used, the runtime
1437 search path will be formed exclusively using the -rpath options,
1438 ignoring the -L options. This can be useful when using gcc, which
1439 adds many -L options which may be on NFS mounted file systems.
1440 For compatibility with other ELF linkers, if the -R option is
1442 followed by a directory name, rather than a file name, it is
1443 treated as the -rpath option.
1444 -rpath-link=dir
1446 When using ELF or SunOS, one shared library may require another.
1447 This happens when an "ld -shared" link includes a shared library as
1448 one of the input files.
1449 When the linker encounters such a dependency when doing a non-
1451 shared, non-relocatable link, it will automatically try to locate
1452 the required shared library and include it in the link, if it is
1453 not included explicitly. In such a case, the -rpath-link option
1454 specifies the first set of directories to search. The -rpath-link
1455 option may specify a sequence of directory names either by
1456 specifying a list of names separated by colons, or by appearing
1457 multiple times.
1458 The tokens $ORIGIN and $LIB can appear in these search directories.
1460 They will be replaced by the full path to the directory containing
1461 the program or shared object in the case of $ORIGIN and either lib
1462 - for 32-bit binaries - or lib64 - for 64-bit binaries - in the
1463 case of $LIB.
1464 The alternative form of these tokens - ${ORIGIN} and ${LIB} can
1466 also be used. The token $PLATFORM is not supported.
1467 This option should be used with caution as it overrides the search
1469 path that may have been hard compiled into a shared library. In
1470 such a case it is possible to use unintentionally a different
1471 search path than the runtime linker would do.
1472 The linker uses the following search paths to locate required
1474 shared libraries:
1475 1. Any directories specified by -rpath-link options.
1477 2. Any directories specified by -rpath options. The difference
1479 between -rpath and -rpath-link is that directories specified by
1480 -rpath options are included in the executable and used at
1481 runtime, whereas the -rpath-link option is only effective at
1482 link time. Searching -rpath in this way is only supported by
1483 native linkers and cross linkers which have been configured
1484 with the --with-sysroot option.
1485 3. On an ELF system, for native linkers, if the -rpath and
1487 -rpath-link options were not used, search the contents of the
1488 environment variable "LD_RUN_PATH".
1489 4. On SunOS, if the -rpath option was not used, search any
1491 directories specified using -L options.
1492 5. For a native linker, search the contents of the environment
1494 variable "LD_LIBRARY_PATH".
1495 6. For a native ELF linker, the directories in "DT_RUNPATH" or
1497 "DT_RPATH" of a shared library are searched for shared
1498 libraries needed by it. The "DT_RPATH" entries are ignored if
1499 "DT_RUNPATH" entries exist.
1500 7. The default directories, normally /lib and /usr/lib.
1502 8. For a native linker on an ELF system, if the file
1504 /etc/ld.so.conf exists, the list of directories found in that
1505 file.
1506 If the required shared library is not found, the linker will issue
1508 a warning and continue with the link.
1509 -shared
1511 -Bshareable
1512 Create a shared library. This is currently only supported on ELF,
1513 XCOFF and SunOS platforms. On SunOS, the linker will automatically
1514 create a shared library if the -e option is not used and there are
1515 undefined symbols in the link.
1516 --sort-common
1518 --sort-common=ascending
1519 --sort-common=descending
1520 This option tells ld to sort the common symbols by alignment in
1521 ascending or descending order when it places them in the
1522 appropriate output sections. The symbol alignments considered are
1523 sixteen-byte or larger, eight-byte, four-byte, two-byte, and one-
1524 byte. This is to prevent gaps between symbols due to alignment
1525 constraints. If no sorting order is specified, then descending
1526 order is assumed.
1527 --sort-section=name
1529 This option will apply "SORT_BY_NAME" to all wildcard section
1530 patterns in the linker script.
1531 --sort-section=alignment
1533 This option will apply "SORT_BY_ALIGNMENT" to all wildcard section
1534 patterns in the linker script.
1535 --spare-dynamic-tags=count
1537 This option specifies the number of empty slots to leave in the
1538 .dynamic section of ELF shared objects. Empty slots may be needed
1539 by post processing tools, such as the prelinker. The default is 5.
1540 --split-by-file[=size]
1542 Similar to --split-by-reloc but creates a new output section for
1543 each input file when size is reached. size defaults to a size of 1
1544 if not given.
1545 --split-by-reloc[=count]
1547 Tries to creates extra sections in the output file so that no
1548 single output section in the file contains more than count
1549 relocations. This is useful when generating huge relocatable files
1550 for downloading into certain real time kernels with the COFF object
1551 file format; since COFF cannot represent more than 65535
1552 relocations in a single section. Note that this will fail to work
1553 with object file formats which do not support arbitrary sections.
1554 The linker will not split up individual input sections for
1555 redistribution, so if a single input section contains more than
1556 count relocations one output section will contain that many
1557 relocations. count defaults to a value of 32768.
1558 --stats
1560 Compute and display statistics about the operation of the linker,
1561 such as execution time and memory usage.
1562 --sysroot=directory
1564 Use directory as the location of the sysroot, overriding the
1565 configure-time default. This option is only supported by linkers
1566 that were configured using --with-sysroot.
1567 --task-link
1569 This is used by COFF/PE based targets to create a task-linked
1570 object file where all of the global symbols have been converted to
1571 statics.
1572 --traditional-format
1574 For some targets, the output of ld is different in some ways from
1575 the output of some existing linker. This switch requests ld to use
1576 the traditional format instead.
1577 For example, on SunOS, ld combines duplicate entries in the symbol
1579 string table. This can reduce the size of an output file with full
1580 debugging information by over 30 percent. Unfortunately, the SunOS
1581 "dbx" program can not read the resulting program ("gdb" has no
1582 trouble). The --traditional-format switch tells ld to not combine
1583 duplicate entries.
1584 --section-start=sectionname=org
1586 Locate a section in the output file at the absolute address given
1587 by org. You may use this option as many times as necessary to
1588 locate multiple sections in the command line. org must be a single
1589 hexadecimal integer; for compatibility with other linkers, you may
1590 omit the leading 0x usually associated with hexadecimal values.
1591 Note: there should be no white space between sectionname, the
1592 equals sign ("="), and org.
1593 -Tbss=org
1595 -Tdata=org
1596 -Ttext=org
1597 Same as --section-start, with ".bss", ".data" or ".text" as the
1598 sectionname.
1599 -Ttext-segment=org
1601 When creating an ELF executable, it will set the address of the
1602 first byte of the text segment.
1603 -Trodata-segment=org
1605 When creating an ELF executable or shared object for a target where
1606 the read-only data is in its own segment separate from the
1607 executable text, it will set the address of the first byte of the
1608 read-only data segment.
1609 -Tldata-segment=org
1611 When creating an ELF executable or shared object for x86-64 medium
1612 memory model, it will set the address of the first byte of the
1613 ldata segment.
1614 --unresolved-symbols=method
1616 Determine how to handle unresolved symbols. There are four
1617 possible values for method:
1618 ignore-all
1620 Do not report any unresolved symbols.
1621 report-all
1623 Report all unresolved symbols. This is the default.
1624 ignore-in-object-files
1626 Report unresolved symbols that are contained in shared
1627 libraries, but ignore them if they come from regular object
1628 files.
1629 ignore-in-shared-libs
1631 Report unresolved symbols that come from regular object files,
1632 but ignore them if they come from shared libraries. This can
1633 be useful when creating a dynamic binary and it is known that
1634 all the shared libraries that it should be referencing are
1635 included on the linker's command line.
1636 The behaviour for shared libraries on their own can also be
1638 controlled by the --[no-]allow-shlib-undefined option.
1639 Normally the linker will generate an error message for each
1641 reported unresolved symbol but the option --warn-unresolved-symbols
1642 can change this to a warning.
1643 --dll-verbose
1645 --verbose[=NUMBER]
1646 Display the version number for ld and list the linker emulations
1647 supported. Display which input files can and cannot be opened.
1648 Display the linker script being used by the linker. If the optional
1649 NUMBER argument > 1, plugin symbol status will also be displayed.
1650 --version-script=version-scriptfile
1652 Specify the name of a version script to the linker. This is
1653 typically used when creating shared libraries to specify additional
1654 information about the version hierarchy for the library being
1655 created. This option is only fully supported on ELF platforms
1656 which support shared libraries; see VERSION. It is partially
1657 supported on PE platforms, which can use version scripts to filter
1658 symbol visibility in auto-export mode: any symbols marked local in
1659 the version script will not be exported.
1660 --warn-common
1662 Warn when a common symbol is combined with another common symbol or
1663 with a symbol definition. Unix linkers allow this somewhat sloppy
1664 practice, but linkers on some other operating systems do not. This
1665 option allows you to find potential problems from combining global
1666 symbols. Unfortunately, some C libraries use this practice, so you
1667 may get some warnings about symbols in the libraries as well as in
1668 your programs.
1669 There are three kinds of global symbols, illustrated here by C
1671 examples:
1672 int i = 1;
1674 A definition, which goes in the initialized data section of the
1675 output file.
1676 extern int i;
1678 An undefined reference, which does not allocate space. There
1679 must be either a definition or a common symbol for the variable
1680 somewhere.
1681 int i;
1683 A common symbol. If there are only (one or more) common
1684 symbols for a variable, it goes in the uninitialized data area
1685 of the output file. The linker merges multiple common symbols
1686 for the same variable into a single symbol. If they are of
1687 different sizes, it picks the largest size. The linker turns a
1688 common symbol into a declaration, if there is a definition of
1689 the same variable.
1690 The --warn-common option can produce five kinds of warnings. Each
1692 warning consists of a pair of lines: the first describes the symbol
1693 just encountered, and the second describes the previous symbol
1694 encountered with the same name. One or both of the two symbols
1695 will be a common symbol.
1696 1. Turning a common symbol into a reference, because there is
1698 already a definition for the symbol.
1699 <file>(<section>): warning: common of `<symbol>'
1701 overridden by definition
1702 <file>(<section>): warning: defined here
1703 2. Turning a common symbol into a reference, because a later
1705 definition for the symbol is encountered. This is the same as
1706 the previous case, except that the symbols are encountered in a
1707 different order.
1708 <file>(<section>): warning: definition of `<symbol>'
1710 overriding common
1711 <file>(<section>): warning: common is here
1712 3. Merging a common symbol with a previous same-sized common
1714 symbol.
1715 <file>(<section>): warning: multiple common
1717 of `<symbol>'
1718 <file>(<section>): warning: previous common is here
1719 4. Merging a common symbol with a previous larger common symbol.
1721 <file>(<section>): warning: common of `<symbol>'
1723 overridden by larger common
1724 <file>(<section>): warning: larger common is here
1725 5. Merging a common symbol with a previous smaller common symbol.
1727 This is the same as the previous case, except that the symbols
1728 are encountered in a different order.
1729 <file>(<section>): warning: common of `<symbol>'
1731 overriding smaller common
1732 <file>(<section>): warning: smaller common is here
1733 --warn-constructors
1735 Warn if any global constructors are used. This is only useful for
1736 a few object file formats. For formats like COFF or ELF, the
1737 linker can not detect the use of global constructors.
1738 --warn-multiple-gp
1740 Warn if multiple global pointer values are required in the output
1741 file. This is only meaningful for certain processors, such as the
1742 Alpha. Specifically, some processors put large-valued constants in
1743 a special section. A special register (the global pointer) points
1744 into the middle of this section, so that constants can be loaded
1745 efficiently via a base-register relative addressing mode. Since
1746 the offset in base-register relative mode is fixed and relatively
1747 small (e.g., 16 bits), this limits the maximum size of the constant
1748 pool. Thus, in large programs, it is often necessary to use
1749 multiple global pointer values in order to be able to address all
1750 possible constants. This option causes a warning to be issued
1751 whenever this case occurs.
1752 --warn-once
1754 Only warn once for each undefined symbol, rather than once per
1755 module which refers to it.
1756 --warn-section-align
1758 Warn if the address of an output section is changed because of
1759 alignment. Typically, the alignment will be set by an input
1760 section. The address will only be changed if it not explicitly
1761 specified; that is, if the "SECTIONS" command does not specify a
1762 start address for the section.
1763 --warn-shared-textrel
1765 Warn if the linker adds a DT_TEXTREL to a shared object.
1766 --warn-alternate-em
1768 Warn if an object has alternate ELF machine code.
1769 --warn-unresolved-symbols
1771 If the linker is going to report an unresolved symbol (see the
1772 option --unresolved-symbols) it will normally generate an error.
1773 This option makes it generate a warning instead.
1774 --error-unresolved-symbols
1776 This restores the linker's default behaviour of generating errors
1777 when it is reporting unresolved symbols.
1778 --whole-archive
1780 For each archive mentioned on the command line after the
1781 --whole-archive option, include every object file in the archive in
1782 the link, rather than searching the archive for the required object
1783 files. This is normally used to turn an archive file into a shared
1784 library, forcing every object to be included in the resulting
1785 shared library. This option may be used more than once.
1786 Two notes when using this option from gcc: First, gcc doesn't know
1788 about this option, so you have to use -Wl,-whole-archive. Second,
1789 don't forget to use -Wl,-no-whole-archive after your list of
1790 archives, because gcc will add its own list of archives to your
1791 link and you may not want this flag to affect those as well.
1792 --wrap=symbol
1794 Use a wrapper function for symbol. Any undefined reference to
1795 symbol will be resolved to "__wrap_symbol". Any undefined
1796 reference to "__real_symbol" will be resolved to symbol.
1797 This can be used to provide a wrapper for a system function. The
1799 wrapper function should be called "__wrap_symbol". If it wishes to
1800 call the system function, it should call "__real_symbol".
1801 Here is a trivial example:
1803 void *
1805 __wrap_malloc (size_t c)
1806 {
1807 printf ("malloc called with %zu\n", c);
1808 return __real_malloc (c);
1809 }
1810 If you link other code with this file using --wrap malloc, then all
1812 calls to "malloc" will call the function "__wrap_malloc" instead.
1813 The call to "__real_malloc" in "__wrap_malloc" will call the real
1814 "malloc" function.
1815 You may wish to provide a "__real_malloc" function as well, so that
1817 links without the --wrap option will succeed. If you do this, you
1818 should not put the definition of "__real_malloc" in the same file
1819 as "__wrap_malloc"; if you do, the assembler may resolve the call
1820 before the linker has a chance to wrap it to "malloc".
1821 Only undefined references are replaced by the linker. So,
1823 translation unit internal references to symbol are not resolved to
1824 "__wrap_symbol". In the next example, the call to "f" in "g" is
1825 not resolved to "__wrap_f".
1826 int
1828 f (void)
1829 {
1830 return 123;
1831 }
1832 int
1834 g (void)
1835 {
1836 return f();
1837 }
1838 --eh-frame-hdr
1840 --no-eh-frame-hdr
1841 Request (--eh-frame-hdr) or suppress (--no-eh-frame-hdr) the
1842 creation of ".eh_frame_hdr" section and ELF "PT_GNU_EH_FRAME"
1843 segment header.
1844 --no-ld-generated-unwind-info
1846 Request creation of ".eh_frame" unwind info for linker generated
1847 code sections like PLT. This option is on by default if linker
1848 generated unwind info is supported.
1849 --enable-new-dtags
1851 --disable-new-dtags
1852 This linker can create the new dynamic tags in ELF. But the older
1853 ELF systems may not understand them. If you specify
1854 --enable-new-dtags, the new dynamic tags will be created as needed
1855 and older dynamic tags will be omitted. If you specify
1856 --disable-new-dtags, no new dynamic tags will be created. By
1857 default, the new dynamic tags are not created. Note that those
1858 options are only available for ELF systems.
1859 --hash-size=number
1861 Set the default size of the linker's hash tables to a prime number
1862 close to number. Increasing this value can reduce the length of
1863 time it takes the linker to perform its tasks, at the expense of
1864 increasing the linker's memory requirements. Similarly reducing
1865 this value can reduce the memory requirements at the expense of
1866 speed.
1867 --hash-style=style
1869 Set the type of linker's hash table(s). style can be either "sysv"
1870 for classic ELF ".hash" section, "gnu" for new style GNU
1871 ".gnu.hash" section or "both" for both the classic ELF ".hash" and
1872 new style GNU ".gnu.hash" hash tables. The default depends upon
1873 how the linker was configured, but for most Linux based systems it
1874 will be "both".
1875 --compress-debug-sections=none
1877 --compress-debug-sections=zlib
1878 --compress-debug-sections=zlib-gnu
1879 --compress-debug-sections=zlib-gabi
1880 On ELF platforms, these options control how DWARF debug sections
1881 are compressed using zlib.
1882 --compress-debug-sections=none doesn't compress DWARF debug
1884 sections. --compress-debug-sections=zlib-gnu compresses DWARF
1885 debug sections and renames them to begin with .zdebug instead of
1886 .debug. --compress-debug-sections=zlib-gabi also compresses DWARF
1887 debug sections, but rather than renaming them it sets the
1888 SHF_COMPRESSED flag in the sections' headers.
1889 The --compress-debug-sections=zlib option is an alias for
1891 --compress-debug-sections=zlib-gabi.
1892 Note that this option overrides any compression in input debug
1894 sections, so if a binary is linked with
1895 --compress-debug-sections=none for example, then any compressed
1896 debug sections in input files will be uncompressed before they are
1897 copied into the output binary.
1898 The default compression behaviour varies depending upon the target
1900 involved and the configure options used to build the toolchain.
1901 The default can be determined by examining the output from the
1902 linker's --help option.
1903 --reduce-memory-overheads
1905 This option reduces memory requirements at ld runtime, at the
1906 expense of linking speed. This was introduced to select the old
1907 O(n^2) algorithm for link map file generation, rather than the new
1908 O(n) algorithm which uses about 40% more memory for symbol storage.
1909 Another effect of the switch is to set the default hash table size
1911 to 1021, which again saves memory at the cost of lengthening the
1912 linker's run time. This is not done however if the --hash-size
1913 switch has been used.
1914 The --reduce-memory-overheads switch may be also be used to enable
1916 other tradeoffs in future versions of the linker.
1917 --build-id
1919 --build-id=style
1920 Request the creation of a ".note.gnu.build-id" ELF note section or
1921 a ".buildid" COFF section. The contents of the note are unique
1922 bits identifying this linked file. style can be "uuid" to use 128
1923 random bits, "sha1" to use a 160-bit SHA1 hash on the normative
1924 parts of the output contents, "md5" to use a 128-bit MD5 hash on
1925 the normative parts of the output contents, or "0xhexstring" to use
1926 a chosen bit string specified as an even number of hexadecimal
1927 digits ("-" and ":" characters between digit pairs are ignored).
1928 If style is omitted, "sha1" is used.
1929 The "md5" and "sha1" styles produces an identifier that is always
1931 the same in an identical output file, but will be unique among all
1932 nonidentical output files. It is not intended to be compared as a
1933 checksum for the file's contents. A linked file may be changed
1934 later by other tools, but the build ID bit string identifying the
1935 original linked file does not change.
1936 Passing "none" for style disables the setting from any "--build-id"
1938 options earlier on the command line.
1939 The i386 PE linker supports the -shared option, which causes the output
1941 to be a dynamically linked library (DLL) instead of a normal
1942 executable. You should name the output "*.dll" when you use this
1943 option. In addition, the linker fully supports the standard "*.def"
1944 files, which may be specified on the linker command line like an object
1945 file (in fact, it should precede archives it exports symbols from, to
1946 ensure that they get linked in, just like a normal object file).
1947 In addition to the options common to all targets, the i386 PE linker
1949 support additional command-line options that are specific to the i386
1950 PE target. Options that take values may be separated from their values
1951 by either a space or an equals sign.
1952 --add-stdcall-alias
1954 If given, symbols with a stdcall suffix (@nn) will be exported as-
1955 is and also with the suffix stripped. [This option is specific to
1956 the i386 PE targeted port of the linker]
1957 --base-file file
1959 Use file as the name of a file in which to save the base addresses
1960 of all the relocations needed for generating DLLs with dlltool.
1961 [This is an i386 PE specific option]
1962 --dll
1964 Create a DLL instead of a regular executable. You may also use
1965 -shared or specify a "LIBRARY" in a given ".def" file. [This
1966 option is specific to the i386 PE targeted port of the linker]
1967 --enable-long-section-names
1969 --disable-long-section-names
1970 The PE variants of the COFF object format add an extension that
1971 permits the use of section names longer than eight characters, the
1972 normal limit for COFF. By default, these names are only allowed in
1973 object files, as fully-linked executable images do not carry the
1974 COFF string table required to support the longer names. As a GNU
1975 extension, it is possible to allow their use in executable images
1976 as well, or to (probably pointlessly!) disallow it in object
1977 files, by using these two options. Executable images generated
1978 with these long section names are slightly non-standard, carrying
1979 as they do a string table, and may generate confusing output when
1980 examined with non-GNU PE-aware tools, such as file viewers and
1981 dumpers. However, GDB relies on the use of PE long section names
1982 to find Dwarf-2 debug information sections in an executable image
1983 at runtime, and so if neither option is specified on the command-
1984 line, ld will enable long section names, overriding the default and
1985 technically correct behaviour, when it finds the presence of debug
1986 information while linking an executable image and not stripping
1987 symbols. [This option is valid for all PE targeted ports of the
1988 linker]
1989 --enable-stdcall-fixup
1991 --disable-stdcall-fixup
1992 If the link finds a symbol that it cannot resolve, it will attempt
1993 to do "fuzzy linking" by looking for another defined symbol that
1994 differs only in the format of the symbol name (cdecl vs stdcall)
1995 and will resolve that symbol by linking to the match. For example,
1996 the undefined symbol "_foo" might be linked to the function
1997 "_foo@12", or the undefined symbol "_bar@16" might be linked to the
1998 function "_bar". When the linker does this, it prints a warning,
1999 since it normally should have failed to link, but sometimes import
2000 libraries generated from third-party dlls may need this feature to
2001 be usable. If you specify --enable-stdcall-fixup, this feature is
2002 fully enabled and warnings are not printed. If you specify
2003 --disable-stdcall-fixup, this feature is disabled and such
2004 mismatches are considered to be errors. [This option is specific
2005 to the i386 PE targeted port of the linker]
2006 --leading-underscore
2008 --no-leading-underscore
2009 For most targets default symbol-prefix is an underscore and is
2010 defined in target's description. By this option it is possible to
2011 disable/enable the default underscore symbol-prefix.
2012 --export-all-symbols
2014 If given, all global symbols in the objects used to build a DLL
2015 will be exported by the DLL. Note that this is the default if
2016 there otherwise wouldn't be any exported symbols. When symbols are
2017 explicitly exported via DEF files or implicitly exported via
2018 function attributes, the default is to not export anything else
2019 unless this option is given. Note that the symbols "DllMain@12",
2020 "DllEntryPoint@0", "DllMainCRTStartup@12", and "impure_ptr" will
2021 not be automatically exported. Also, symbols imported from other
2022 DLLs will not be re-exported, nor will symbols specifying the DLL's
2023 internal layout such as those beginning with "_head_" or ending
2024 with "_iname". In addition, no symbols from "libgcc", "libstd++",
2025 "libmingw32", or "crtX.o" will be exported. Symbols whose names
2026 begin with "__rtti_" or "__builtin_" will not be exported, to help
2027 with C++ DLLs. Finally, there is an extensive list of cygwin-
2028 private symbols that are not exported (obviously, this applies on
2029 when building DLLs for cygwin targets). These cygwin-excludes are:
2030 "_cygwin_dll_entry@12", "_cygwin_crt0_common@8",
2031 "_cygwin_noncygwin_dll_entry@12", "_fmode", "_impure_ptr",
2032 "cygwin_attach_dll", "cygwin_premain0", "cygwin_premain1",
2033 "cygwin_premain2", "cygwin_premain3", and "environ". [This option
2034 is specific to the i386 PE targeted port of the linker]
2035 --exclude-symbols symbol,symbol,...
2037 Specifies a list of symbols which should not be automatically
2038 exported. The symbol names may be delimited by commas or colons.
2039 [This option is specific to the i386 PE targeted port of the
2040 linker]
2041 --exclude-all-symbols
2043 Specifies no symbols should be automatically exported. [This
2044 option is specific to the i386 PE targeted port of the linker]
2045 --file-alignment
2047 Specify the file alignment. Sections in the file will always begin
2048 at file offsets which are multiples of this number. This defaults
2049 to 512. [This option is specific to the i386 PE targeted port of
2050 the linker]
2051 --heap reserve
2053 --heap reserve,commit
2054 Specify the number of bytes of memory to reserve (and optionally
2055 commit) to be used as heap for this program. The default is 1MB
2056 reserved, 4K committed. [This option is specific to the i386 PE
2057 targeted port of the linker]
2058 --image-base value
2060 Use value as the base address of your program or dll. This is the
2061 lowest memory location that will be used when your program or dll
2062 is loaded. To reduce the need to relocate and improve performance
2063 of your dlls, each should have a unique base address and not
2064 overlap any other dlls. The default is 0x400000 for executables,
2065 and 0x10000000 for dlls. [This option is specific to the i386 PE
2066 targeted port of the linker]
2067 --kill-at
2069 If given, the stdcall suffixes (@nn) will be stripped from symbols
2070 before they are exported. [This option is specific to the i386 PE
2071 targeted port of the linker]
2072 --large-address-aware
2074 If given, the appropriate bit in the "Characteristics" field of the
2075 COFF header is set to indicate that this executable supports
2076 virtual addresses greater than 2 gigabytes. This should be used in
2077 conjunction with the /3GB or /USERVA=value megabytes switch in the
2078 "[operating systems]" section of the BOOT.INI. Otherwise, this bit
2079 has no effect. [This option is specific to PE targeted ports of
2080 the linker]
2081 --disable-large-address-aware
2083 Reverts the effect of a previous --large-address-aware option.
2084 This is useful if --large-address-aware is always set by the
2085 compiler driver (e.g. Cygwin gcc) and the executable does not
2086 support virtual addresses greater than 2 gigabytes. [This option
2087 is specific to PE targeted ports of the linker]
2088 --major-image-version value
2090 Sets the major number of the "image version". Defaults to 1.
2091 [This option is specific to the i386 PE targeted port of the
2092 linker]
2093 --major-os-version value
2095 Sets the major number of the "os version". Defaults to 4. [This
2096 option is specific to the i386 PE targeted port of the linker]
2097 --major-subsystem-version value
2099 Sets the major number of the "subsystem version". Defaults to 4.
2100 [This option is specific to the i386 PE targeted port of the
2101 linker]
2102 --minor-image-version value
2104 Sets the minor number of the "image version". Defaults to 0.
2105 [This option is specific to the i386 PE targeted port of the
2106 linker]
2107 --minor-os-version value
2109 Sets the minor number of the "os version". Defaults to 0. [This
2110 option is specific to the i386 PE targeted port of the linker]
2111 --minor-subsystem-version value
2113 Sets the minor number of the "subsystem version". Defaults to 0.
2114 [This option is specific to the i386 PE targeted port of the
2115 linker]
2116 --output-def file
2118 The linker will create the file file which will contain a DEF file
2119 corresponding to the DLL the linker is generating. This DEF file
2120 (which should be called "*.def") may be used to create an import
2121 library with "dlltool" or may be used as a reference to
2122 automatically or implicitly exported symbols. [This option is
2123 specific to the i386 PE targeted port of the linker]
2124 --enable-auto-image-base
2126 --enable-auto-image-base=value
2127 Automatically choose the image base for DLLs, optionally starting
2128 with base value, unless one is specified using the "--image-base"
2129 argument. By using a hash generated from the dllname to create
2130 unique image bases for each DLL, in-memory collisions and
2131 relocations which can delay program execution are avoided. [This
2132 option is specific to the i386 PE targeted port of the linker]
2133 --disable-auto-image-base
2135 Do not automatically generate a unique image base. If there is no
2136 user-specified image base ("--image-base") then use the platform
2137 default. [This option is specific to the i386 PE targeted port of
2138 the linker]
2139 --dll-search-prefix string
2141 When linking dynamically to a dll without an import library, search
2142 for "<string><basename>.dll" in preference to "lib<basename>.dll".
2143 This behaviour allows easy distinction between DLLs built for the
2144 various "subplatforms": native, cygwin, uwin, pw, etc. For
2145 instance, cygwin DLLs typically use "--dll-search-prefix=cyg".
2146 [This option is specific to the i386 PE targeted port of the
2147 linker]
2148 --enable-auto-import
2150 Do sophisticated linking of "_symbol" to "__imp__symbol" for DATA
2151 imports from DLLs, thus making it possible to bypass the dllimport
2152 mechanism on the user side and to reference unmangled symbol names.
2153 [This option is specific to the i386 PE targeted port of the
2154 linker]
2155 The following remarks pertain to the original implementation of the
2157 feature and are obsolete nowadays for Cygwin and MinGW targets.
2158 Note: Use of the 'auto-import' extension will cause the text
2160 section of the image file to be made writable. This does not
2161 conform to the PE-COFF format specification published by Microsoft.
2162 Note - use of the 'auto-import' extension will also cause read only
2164 data which would normally be placed into the .rdata section to be
2165 placed into the .data section instead. This is in order to work
2166 around a problem with consts that is described here:
2167 http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
2168 Using 'auto-import' generally will 'just work' -- but sometimes you
2170 may see this message:
2171 "variable '<var>' can't be auto-imported. Please read the
2173 documentation for ld's "--enable-auto-import" for details."
2174 This message occurs when some (sub)expression accesses an address
2176 ultimately given by the sum of two constants (Win32 import tables
2177 only allow one). Instances where this may occur include accesses
2178 to member fields of struct variables imported from a DLL, as well
2179 as using a constant index into an array variable imported from a
2180 DLL. Any multiword variable (arrays, structs, long long, etc) may
2181 trigger this error condition. However, regardless of the exact
2182 data type of the offending exported variable, ld will always detect
2183 it, issue the warning, and exit.
2184 There are several ways to address this difficulty, regardless of
2186 the data type of the exported variable:
2187 One way is to use --enable-runtime-pseudo-reloc switch. This leaves
2189 the task of adjusting references in your client code for runtime
2190 environment, so this method works only when runtime environment
2191 supports this feature.
2192 A second solution is to force one of the 'constants' to be a
2194 variable -- that is, unknown and un-optimizable at compile time.
2195 For arrays, there are two possibilities: a) make the indexee (the
2196 array's address) a variable, or b) make the 'constant' index a
2197 variable. Thus:
2198 extern type extern_array[];
2200 extern_array[1] -->
2201 { volatile type *t=extern_array; t[1] }
2202 or
2204 extern type extern_array[];
2206 extern_array[1] -->
2207 { volatile int t=1; extern_array[t] }
2208 For structs (and most other multiword data types) the only option
2210 is to make the struct itself (or the long long, or the ...)
2211 variable:
2212 extern struct s extern_struct;
2214 extern_struct.field -->
2215 { volatile struct s *t=&extern_struct; t->field }
2216 or
2218 extern long long extern_ll;
2220 extern_ll -->
2221 { volatile long long * local_ll=&extern_ll; *local_ll }
2222 A third method of dealing with this difficulty is to abandon
2224 'auto-import' for the offending symbol and mark it with
2225 "__declspec(dllimport)". However, in practice that requires using
2226 compile-time #defines to indicate whether you are building a DLL,
2227 building client code that will link to the DLL, or merely
2228 building/linking to a static library. In making the choice
2229 between the various methods of resolving the 'direct address with
2230 constant offset' problem, you should consider typical real-world
2231 usage:
2232 Original:
2234 --foo.h
2236 extern int arr[];
2237 --foo.c
2238 #include "foo.h"
2239 void main(int argc, char **argv){
2240 printf("%d\n",arr[1]);
2241 }
2242 Solution 1:
2244 --foo.h
2246 extern int arr[];
2247 --foo.c
2248 #include "foo.h"
2249 void main(int argc, char **argv){
2250 /* This workaround is for win32 and cygwin; do not "optimize" */
2251 volatile int *parr = arr;
2252 printf("%d\n",parr[1]);
2253 }
2254 Solution 2:
2256 --foo.h
2258 /* Note: auto-export is assumed (no __declspec(dllexport)) */
2259 #if (defined(_WIN32) || defined(__CYGWIN__)) && \
2260 !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
2261 #define FOO_IMPORT __declspec(dllimport)
2262 #else
2263 #define FOO_IMPORT
2264 #endif
2265 extern FOO_IMPORT int arr[];
2266 --foo.c
2267 #include "foo.h"
2268 void main(int argc, char **argv){
2269 printf("%d\n",arr[1]);
2270 }
2271 A fourth way to avoid this problem is to re-code your library to
2273 use a functional interface rather than a data interface for the
2274 offending variables (e.g. set_foo() and get_foo() accessor
2275 functions).
2276 --disable-auto-import
2278 Do not attempt to do sophisticated linking of "_symbol" to
2279 "__imp__symbol" for DATA imports from DLLs. [This option is
2280 specific to the i386 PE targeted port of the linker]
2281 --enable-runtime-pseudo-reloc
2283 If your code contains expressions described in --enable-auto-import
2284 section, that is, DATA imports from DLL with non-zero offset, this
2285 switch will create a vector of 'runtime pseudo relocations' which
2286 can be used by runtime environment to adjust references to such
2287 data in your client code. [This option is specific to the i386 PE
2288 targeted port of the linker]
2289 --disable-runtime-pseudo-reloc
2291 Do not create pseudo relocations for non-zero offset DATA imports
2292 from DLLs. [This option is specific to the i386 PE targeted port
2293 of the linker]
2294 --enable-extra-pe-debug
2296 Show additional debug info related to auto-import symbol thunking.
2297 [This option is specific to the i386 PE targeted port of the
2298 linker]
2299 --section-alignment
2301 Sets the section alignment. Sections in memory will always begin
2302 at addresses which are a multiple of this number. Defaults to
2303 0x1000. [This option is specific to the i386 PE targeted port of
2304 the linker]
2305 --stack reserve
2307 --stack reserve,commit
2308 Specify the number of bytes of memory to reserve (and optionally
2309 commit) to be used as stack for this program. The default is 2MB
2310 reserved, 4K committed. [This option is specific to the i386 PE
2311 targeted port of the linker]
2312 --subsystem which
2314 --subsystem which:major
2315 --subsystem which:major.minor
2316 Specifies the subsystem under which your program will execute. The
2317 legal values for which are "native", "windows", "console", "posix",
2318 and "xbox". You may optionally set the subsystem version also.
2319 Numeric values are also accepted for which. [This option is
2320 specific to the i386 PE targeted port of the linker]
2321 The following options set flags in the "DllCharacteristics" field
2323 of the PE file header: [These options are specific to PE targeted
2324 ports of the linker]
2325 --high-entropy-va
2327 Image is compatible with 64-bit address space layout randomization
2328 (ASLR). This option also implies --dynamicbase and
2329 --enable-reloc-section.
2330 --dynamicbase
2332 The image base address may be relocated using address space layout
2333 randomization (ASLR). This feature was introduced with MS Windows
2334 Vista for i386 PE targets. This option also implies
2335 --enable-reloc-section.
2336 --forceinteg
2338 Code integrity checks are enforced.
2339 --nxcompat
2341 The image is compatible with the Data Execution Prevention. This
2342 feature was introduced with MS Windows XP SP2 for i386 PE targets.
2343 --no-isolation
2345 Although the image understands isolation, do not isolate the image.
2346 --no-seh
2348 The image does not use SEH. No SE handler may be called from this
2349 image.
2350 --no-bind
2352 Do not bind this image.
2353 --wdmdriver
2355 The driver uses the MS Windows Driver Model.
2356 --tsaware
2358 The image is Terminal Server aware.
2359 --insert-timestamp
2361 --no-insert-timestamp
2362 Insert a real timestamp into the image. This is the default
2363 behaviour as it matches legacy code and it means that the image
2364 will work with other, proprietary tools. The problem with this
2365 default is that it will result in slightly different images being
2366 produced each time the same sources are linked. The option
2367 --no-insert-timestamp can be used to insert a zero value for the
2368 timestamp, this ensuring that binaries produced from identical
2369 sources will compare identically.
2370 --enable-reloc-section
2372 Create the base relocation table, which is necessary if the image
2373 is loaded at a different image base than specified in the PE
2374 header.
2375 The C6X uClinux target uses a binary format called DSBT to support
2377 shared libraries. Each shared library in the system needs to have a
2378 unique index; all executables use an index of 0.
2379 --dsbt-size size
2381 This option sets the number of entries in the DSBT of the current
2382 executable or shared library to size. The default is to create a
2383 table with 64 entries.
2384 --dsbt-index index
2386 This option sets the DSBT index of the current executable or shared
2387 library to index. The default is 0, which is appropriate for
2388 generating executables. If a shared library is generated with a
2389 DSBT index of 0, the "R_C6000_DSBT_INDEX" relocs are copied into
2390 the output file.
2391 The --no-merge-exidx-entries switch disables the merging of
2393 adjacent exidx entries in frame unwind info.
2394 --branch-stub
2396 This option enables linker branch relaxation by inserting branch
2397 stub sections when needed to extend the range of branches. This
2398 option is usually not required since C-SKY supports branch and call
2399 instructions that can access the full memory range and branch
2400 relaxation is normally handled by the compiler or assembler.
2401 --stub-group-size=N
2403 This option allows finer control of linker branch stub creation.
2404 It sets the maximum size of a group of input sections that can be
2405 handled by one stub section. A negative value of N locates stub
2406 sections after their branches, while a positive value allows stub
2407 sections to appear either before or after the branches. Values of
2408 1 or -1 indicate that the linker should choose suitable defaults.
2409 The 68HC11 and 68HC12 linkers support specific options to control the
2411 memory bank switching mapping and trampoline code generation.
2412 --no-trampoline
2414 This option disables the generation of trampoline. By default a
2415 trampoline is generated for each far function which is called using
2416 a "jsr" instruction (this happens when a pointer to a far function
2417 is taken).
2418 --bank-window name
2420 This option indicates to the linker the name of the memory region
2421 in the MEMORY specification that describes the memory bank window.
2422 The definition of such region is then used by the linker to compute
2423 paging and addresses within the memory window.
2424 The following options are supported to control handling of GOT
2426 generation when linking for 68K targets.
2427 --got=type
2429 This option tells the linker which GOT generation scheme to use.
2430 type should be one of single, negative, multigot or target. For
2431 more information refer to the Info entry for ld.
2432 The following options are supported to control microMIPS instruction
2434 generation and branch relocation checks for ISA mode transitions when
2435 linking for MIPS targets.
2436 --insn32
2438 --no-insn32
2439 These options control the choice of microMIPS instructions used in
2440 code generated by the linker, such as that in the PLT or lazy
2441 binding stubs, or in relaxation. If --insn32 is used, then the
2442 linker only uses 32-bit instruction encodings. By default or if
2443 --no-insn32 is used, all instruction encodings are used, including
2444 16-bit ones where possible.
2445 --ignore-branch-isa
2447 --no-ignore-branch-isa
2448 These options control branch relocation checks for invalid ISA mode
2449 transitions. If --ignore-branch-isa is used, then the linker
2450 accepts any branch relocations and any ISA mode transition required
2451 is lost in relocation calculation, except for some cases of "BAL"
2452 instructions which meet relaxation conditions and are converted to
2453 equivalent "JALX" instructions as the associated relocation is
2454 calculated. By default or if --no-ignore-branch-isa is used a
2455 check is made causing the loss of an ISA mode transition to produce
2456 an error.
2457 --compact-branches
2459 --compact-branches
2460 These options control the generation of compact instructions by the
2461 linker in the PLT entries for MIPS R6.
2462
2464 You can change the behaviour of ld with the environment variables
2465 "GNUTARGET", "LDEMULATION" and "COLLECT_NO_DEMANGLE".
2466 "GNUTARGET" determines the input-file object format if you don't use -b
2468 (or its synonym --format). Its value should be one of the BFD names
2469 for an input format. If there is no "GNUTARGET" in the environment, ld
2470 uses the natural format of the target. If "GNUTARGET" is set to
2471 "default" then BFD attempts to discover the input format by examining
2472 binary input files; this method often succeeds, but there are potential
2473 ambiguities, since there is no method of ensuring that the magic number
2474 used to specify object-file formats is unique. However, the
2475 configuration procedure for BFD on each system places the conventional
2476 format for that system first in the search-list, so ambiguities are
2477 resolved in favor of convention.
2478 "LDEMULATION" determines the default emulation if you don't use the -m
2480 option. The emulation can affect various aspects of linker behaviour,
2481 particularly the default linker script. You can list the available
2482 emulations with the --verbose or -V options. If the -m option is not
2483 used, and the "LDEMULATION" environment variable is not defined, the
2484 default emulation depends upon how the linker was configured.
2485 Normally, the linker will default to demangling symbols. However, if
2487 "COLLECT_NO_DEMANGLE" is set in the environment, then it will default
2488 to not demangling symbols. This environment variable is used in a
2489 similar fashion by the "gcc" linker wrapper program. The default may
2490 be overridden by the --demangle and --no-demangle options.
2491
2493 ar(1), nm(1), objcopy(1), objdump(1), readelf(1) and the Info entries
2494 for binutils and ld.
2495
2497 Copyright (c) 1991-2020 Free Software Foundation, Inc.
2498 Permission is granted to copy, distribute and/or modify this document
2500 under the terms of the GNU Free Documentation License, Version 1.3 or
2501 any later version published by the Free Software Foundation; with no
2502 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
2503 Texts. A copy of the license is included in the section entitled "GNU
2504 Free Documentation License".
2505binutils-2.34 2020-02-01 LD(1)