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 --enable-linker-version
207 Enables the "LINKER_VERSION" linker script directive, described in
208 Output Section Data. If this directive is used in a linker script
209 and this option has been enabled then a string containing the
210 linker version will be inserted at the current point.
211 Note - this location of this option on the linker command line is
213 significant. It will only affect linker scripts that come after it
214 on the command line, or which are built into the linker.
215 --disable-linker-version
217 Disables the "LINKER_VERSION" linker script directive, so that it
218 does not insert a version string. This is the default.
219 --enable-non-contiguous-regions
221 This option avoids generating an error if an input section does not
222 fit a matching output section. The linker tries to allocate the
223 input section to subseque nt matching output sections, and
224 generates an error only if no output section is large enough. This
225 is useful when several non-contiguous memory regions are available
226 and the input section does not require a particular one. The order
227 in which input sections are evaluated does not change, for
228 instance:
229 MEMORY {
231 MEM1 (rwx) : ORIGIN = 0x1000, LENGTH = 0x14
232 MEM2 (rwx) : ORIGIN = 0x1000, LENGTH = 0x40
233 MEM3 (rwx) : ORIGIN = 0x2000, LENGTH = 0x40
234 }
235 SECTIONS {
236 mem1 : { *(.data.*); } > MEM1
237 mem2 : { *(.data.*); } > MEM2
238 mem3 : { *(.data.*); } > MEM3
239 }
240 with input sections:
242 .data.1: size 8
243 .data.2: size 0x10
244 .data.3: size 4
245 results in .data.1 affected to mem1, and .data.2 and .data.3
247 affected to mem2, even though .data.3 would fit in mem3.
248 This option is incompatible with INSERT statements because it
250 changes the way input sections are mapped to output sections.
251 --enable-non-contiguous-regions-warnings
253 This option enables warnings when "--enable-non-contiguous-regions"
254 allows possibly unexpected matches in sections mapping, potentially
255 leading to silently discarding a section instead of failing because
256 it does not fit any output region.
257 -e entry
259 --entry=entry
260 Use entry as the explicit symbol for beginning execution of your
261 program, rather than the default entry point. If there is no
262 symbol named entry, the linker will try to parse entry as a number,
263 and use that as the entry address (the number will be interpreted
264 in base 10; you may use a leading 0x for base 16, or a leading 0
265 for base 8).
266 --exclude-libs lib,lib,...
268 Specifies a list of archive libraries from which symbols should not
269 be automatically exported. The library names may be delimited by
270 commas or colons. Specifying "--exclude-libs ALL" excludes symbols
271 in all archive libraries from automatic export. This option is
272 available only for the i386 PE targeted port of the linker and for
273 ELF targeted ports. For i386 PE, symbols explicitly listed in a
274 .def file are still exported, regardless of this option. For ELF
275 targeted ports, symbols affected by this option will be treated as
276 hidden.
277 --exclude-modules-for-implib module,module,...
279 Specifies a list of object files or archive members, from which
280 symbols should not be automatically exported, but which should be
281 copied wholesale into the import library being generated during the
282 link. The module names may be delimited by commas or colons, and
283 must match exactly the filenames used by ld to open the files; for
284 archive members, this is simply the member name, but for object
285 files the name listed must include and match precisely any path
286 used to specify the input file on the linker's command-line. This
287 option is available only for the i386 PE targeted port of the
288 linker. Symbols explicitly listed in a .def file are still
289 exported, regardless of this option.
290 -E
292 --export-dynamic
293 --no-export-dynamic
294 When creating a dynamically linked executable, using the -E option
295 or the --export-dynamic option causes the linker to add all symbols
296 to the dynamic symbol table. The dynamic symbol table is the set
297 of symbols which are visible from dynamic objects at run time.
298 If you do not use either of these options (or use the
300 --no-export-dynamic option to restore the default behavior), the
301 dynamic symbol table will normally contain only those symbols which
302 are referenced by some dynamic object mentioned in the link.
303 If you use "dlopen" to load a dynamic object which needs to refer
305 back to the symbols defined by the program, rather than some other
306 dynamic object, then you will probably need to use this option when
307 linking the program itself.
308 You can also use the dynamic list to control what symbols should be
310 added to the dynamic symbol table if the output format supports it.
311 See the description of --dynamic-list.
312 Note that this option is specific to ELF targeted ports. PE
314 targets support a similar function to export all symbols from a DLL
315 or EXE; see the description of --export-all-symbols below.
316 --export-dynamic-symbol=glob
318 When creating a dynamically linked executable, symbols matching
319 glob will be added to the dynamic symbol table. When creating a
320 shared library, references to symbols matching glob will not be
321 bound to the definitions within the shared library. This option is
322 a no-op when creating a shared library and -Bsymbolic or
323 --dynamic-list are not specified. This option is only meaningful on
324 ELF platforms which support shared libraries.
325 --export-dynamic-symbol-list=file
327 Specify a --export-dynamic-symbol for each pattern in the file.
328 The format of the file is the same as the version node without
329 scope and node name. See VERSION for more information.
330 -EB Link big-endian objects. This affects the default output format.
332 -EL Link little-endian objects. This affects the default output
334 format.
335 -f name
337 --auxiliary=name
338 When creating an ELF shared object, set the internal DT_AUXILIARY
339 field to the specified name. This tells the dynamic linker that
340 the symbol table of the shared object should be used as an
341 auxiliary filter on the symbol table of the shared object name.
342 If you later link a program against this filter object, then, when
344 you run the program, the dynamic linker will see the DT_AUXILIARY
345 field. If the dynamic linker resolves any symbols from the filter
346 object, it will first check whether there is a definition in the
347 shared object name. If there is one, it will be used instead of
348 the definition in the filter object. The shared object name need
349 not exist. Thus the shared object name may be used to provide an
350 alternative implementation of certain functions, perhaps for
351 debugging or for machine-specific performance.
352 This option may be specified more than once. The DT_AUXILIARY
354 entries will be created in the order in which they appear on the
355 command line.
356 -F name
358 --filter=name
359 When creating an ELF shared object, set the internal DT_FILTER
360 field to the specified name. This tells the dynamic linker that
361 the symbol table of the shared object which is being created should
362 be used as a filter on the symbol table of the shared object name.
363 If you later link a program against this filter object, then, when
365 you run the program, the dynamic linker will see the DT_FILTER
366 field. The dynamic linker will resolve symbols according to the
367 symbol table of the filter object as usual, but it will actually
368 link to the definitions found in the shared object name. Thus the
369 filter object can be used to select a subset of the symbols
370 provided by the object name.
371 Some older linkers used the -F option throughout a compilation
373 toolchain for specifying object-file format for both input and
374 output object files. The GNU linker uses other mechanisms for this
375 purpose: the -b, --format, --oformat options, the "TARGET" command
376 in linker scripts, and the "GNUTARGET" environment variable. The
377 GNU linker will ignore the -F option when not creating an ELF
378 shared object.
379 -fini=name
381 When creating an ELF executable or shared object, call NAME when
382 the executable or shared object is unloaded, by setting DT_FINI to
383 the address of the function. By default, the linker uses "_fini"
384 as the function to call.
385 -g Ignored. Provided for compatibility with other tools.
387 -G value
389 --gpsize=value
390 Set the maximum size of objects to be optimized using the GP
391 register to size. This is only meaningful for object file formats
392 such as MIPS ELF that support putting large and small objects into
393 different sections. This is ignored for other object file formats.
394 -h name
396 -soname=name
397 When creating an ELF shared object, set the internal DT_SONAME
398 field to the specified name. When an executable is linked with a
399 shared object which has a DT_SONAME field, then when the executable
400 is run the dynamic linker will attempt to load the shared object
401 specified by the DT_SONAME field rather than using the file name
402 given to the linker.
403 -i Perform an incremental link (same as option -r).
405 -init=name
407 When creating an ELF executable or shared object, call NAME when
408 the executable or shared object is loaded, by setting DT_INIT to
409 the address of the function. By default, the linker uses "_init"
410 as the function to call.
411 -l namespec
413 --library=namespec
414 Add the archive or object file specified by namespec to the list of
415 files to link. This option may be used any number of times. If
416 namespec is of the form :filename, ld will search the library path
417 for a file called filename, otherwise it will search the library
418 path for a file called libnamespec.a.
419 On systems which support shared libraries, ld may also search for
421 files other than libnamespec.a. Specifically, on ELF and SunOS
422 systems, ld will search a directory for a library called
423 libnamespec.so before searching for one called libnamespec.a. (By
424 convention, a ".so" extension indicates a shared library.) Note
425 that this behavior does not apply to :filename, which always
426 specifies a file called filename.
427 The linker will search an archive only once, at the location where
429 it is specified on the command line. If the archive defines a
430 symbol which was undefined in some object which appeared before the
431 archive on the command line, the linker will include the
432 appropriate file(s) from the archive. However, an undefined symbol
433 in an object appearing later on the command line will not cause the
434 linker to search the archive again.
435 See the -( option for a way to force the linker to search archives
437 multiple times.
438 You may list the same archive multiple times on the command line.
440 This type of archive searching is standard for Unix linkers.
442 However, if you are using ld on AIX, note that it is different from
443 the behaviour of the AIX linker.
444 -L searchdir
446 --library-path=searchdir
447 Add path searchdir to the list of paths that ld will search for
448 archive libraries and ld control scripts. You may use this option
449 any number of times. The directories are searched in the order in
450 which they are specified on the command line. Directories
451 specified on the command line are searched before the default
452 directories. All -L options apply to all -l options, regardless of
453 the order in which the options appear. -L options do not affect
454 how ld searches for a linker script unless -T option is specified.
455 If searchdir begins with "=" or $SYSROOT, then this prefix will be
457 replaced by the sysroot prefix, controlled by the --sysroot option,
458 or specified when the linker is configured.
459 The default set of paths searched (without being specified with -L)
461 depends on which emulation mode ld is using, and in some cases also
462 on how it was configured.
463 The paths can also be specified in a link script with the
465 "SEARCH_DIR" command. Directories specified this way are searched
466 at the point in which the linker script appears in the command
467 line.
468 -m emulation
470 Emulate the emulation linker. You can list the available
471 emulations with the --verbose or -V options.
472 If the -m option is not used, the emulation is taken from the
474 "LDEMULATION" environment variable, if that is defined.
475 Otherwise, the default emulation depends upon how the linker was
477 configured.
478 --remap-inputs=pattern=filename
480 --remap-inputs-file=file
481 These options allow the names of input files to be changed before
482 the linker attempts to open them. The option
483 --remap-inputs=foo.o=bar.o will cause any attempt to load a file
484 called foo.o to instead try to load a file called bar.o. Wildcard
485 patterns are permitted in the first filename, so
486 --remap-inputs=foo*.o=bar.o will rename any input file that matches
487 foo*.o to bar.o.
488 An alternative form of the option --remap-inputs-file=filename
490 allows the remappings to be read from a file. Each line in the
491 file can contain a single remapping. Blank lines are ignored.
492 Anything from a hash character (#) to the end of a line is
493 considered to be a comment and is also ignored. The mapping
494 pattern can be separated from the filename by whitespace or an
495 equals (=) character.
496 The options can be specified multiple times. Their contents
498 accumulate. The remappings will be processed in the order in which
499 they occur on the command line, and if they come from a file, in
500 the order in which they occur in the file. If a match is made, no
501 further checking for that filename will be performed.
502 If the replacement filename is /dev/null or just NUL then the
504 remapping will actually cause the input file to be ignored. This
505 can be a convenient way to experiment with removing input files
506 from a complicated build environment.
507 Note that this option is position dependent and only affects
509 filenames that come after it on the command line. Thus:
510 ld foo.o --remap-inputs=foo.o=bar.o
512 Will have no effect, whereas:
514 ld --remap-inputs=foo.o=bar.o foo.o
516 Will rename the input file foo.o to bar.o.
518 Note - these options also affect files referenced by INPUT
520 statements in linker scripts. But since linker scripts are
521 processed after the entire command line is read, the position of
522 the remap options on the command line is not significant.
523 If the verbose option is enabled then any mappings that match will
525 be reported, although again the verbose option needs to be enabled
526 on the command line before the remaped filenames appear.
527 If the -Map or --print-map options are enabled then the remapping
529 list will be included in the map output.
530 -M
532 --print-map
533 Print a link map to the standard output. A link map provides
534 information about the link, including the following:
535 • Where object files are mapped into memory.
537 • How common symbols are allocated.
539 • All archive members included in the link, with a mention of the
541 symbol which caused the archive member to be brought in.
542 • The values assigned to symbols.
544 Note - symbols whose values are computed by an expression which
546 involves a reference to a previous value of the same symbol may
547 not have correct result displayed in the link map. This is
548 because the linker discards intermediate results and only
549 retains the final value of an expression. Under such
550 circumstances the linker will display the final value enclosed
551 by square brackets. Thus for example a linker script
552 containing:
553 foo = 1
555 foo = foo * 4
556 foo = foo + 8
557 will produce the following output in the link map if the -M
559 option is used:
560 0x00000001 foo = 0x1
562 [0x0000000c] foo = (foo * 0x4)
563 [0x0000000c] foo = (foo + 0x8)
564 See Expressions for more information about expressions in
566 linker scripts.
567 • How GNU properties are merged.
569 When the linker merges input .note.gnu.property sections into
571 one output .note.gnu.property section, some properties are
572 removed or updated. These actions are reported in the link
573 map. For example:
574 Removed property 0xc0000002 to merge foo.o (0x1) and bar.o (not found)
576 This indicates that property 0xc0000002 is removed from output
578 when merging properties in foo.o, whose property 0xc0000002
579 value is 0x1, and bar.o, which doesn't have property
580 0xc0000002.
581 Updated property 0xc0010001 (0x1) to merge foo.o (0x1) and bar.o (0x1)
583 This indicates that property 0xc0010001 value is updated to 0x1
585 in output when merging properties in foo.o, whose 0xc0010001
586 property value is 0x1, and bar.o, whose 0xc0010001 property
587 value is 0x1.
588 --print-map-discarded
590 --no-print-map-discarded
591 Print (or do not print) the list of discarded and garbage collected
592 sections in the link map. Enabled by default.
593 --print-map-locals
595 --no-print-map-locals
596 Print (or do not print) local symbols in the link map. Local
597 symbols will have the text (local) printed before their name, and
598 will be listed after all of the global symbols in a given section.
599 Temporary local symbols (typically those that start with .L) will
600 not be included in the output. Disabled by default.
601 -n
603 --nmagic
604 Turn off page alignment of sections, and disable linking against
605 shared libraries. If the output format supports Unix style magic
606 numbers, mark the output as "NMAGIC".
607 -N
609 --omagic
610 Set the text and data sections to be readable and writable. Also,
611 do not page-align the data segment, and disable linking against
612 shared libraries. If the output format supports Unix style magic
613 numbers, mark the output as "OMAGIC". Note: Although a writable
614 text section is allowed for PE-COFF targets, it does not conform to
615 the format specification published by Microsoft.
616 --no-omagic
618 This option negates most of the effects of the -N option. It sets
619 the text section to be read-only, and forces the data segment to be
620 page-aligned. Note - this option does not enable linking against
621 shared libraries. Use -Bdynamic for this.
622 -o output
624 --output=output
625 Use output as the name for the program produced by ld; if this
626 option is not specified, the name a.out is used by default. The
627 script command "OUTPUT" can also specify the output file name.
628 --dependency-file=depfile
630 Write a dependency file to depfile. This file contains a rule
631 suitable for "make" describing the output file and all the input
632 files that were read to produce it. The output is similar to the
633 compiler's output with -M -MP. Note that there is no option like
634 the compiler's -MM, to exclude "system files" (which is not a well-
635 specified concept in the linker, unlike "system headers" in the
636 compiler). So the output from --dependency-file is always specific
637 to the exact state of the installation where it was produced, and
638 should not be copied into distributed makefiles without careful
639 editing.
640 -O level
642 If level is a numeric values greater than zero ld optimizes the
643 output. This might take significantly longer and therefore
644 probably should only be enabled for the final binary. At the
645 moment this option only affects ELF shared library generation.
646 Future releases of the linker may make more use of this option.
647 Also currently there is no difference in the linker's behaviour for
648 different non-zero values of this option. Again this may change
649 with future releases.
650 -plugin name
652 Involve a plugin in the linking process. The name parameter is the
653 absolute filename of the plugin. Usually this parameter is
654 automatically added by the complier, when using link time
655 optimization, but users can also add their own plugins if they so
656 wish.
657 Note that the location of the compiler originated plugins is
659 different from the place where the ar, nm and ranlib programs
660 search for their plugins. In order for those commands to make use
661 of a compiler based plugin it must first be copied into the
662 ${libdir}/bfd-plugins directory. All gcc based linker plugins are
663 backward compatible, so it is sufficient to just copy in the newest
664 one.
665 --push-state
667 The --push-state allows one to preserve the current state of the
668 flags which govern the input file handling so that they can all be
669 restored with one corresponding --pop-state option.
670 The option which are covered are: -Bdynamic, -Bstatic, -dn, -dy,
672 -call_shared, -non_shared, -static, -N, -n, --whole-archive,
673 --no-whole-archive, -r, -Ur, --copy-dt-needed-entries,
674 --no-copy-dt-needed-entries, --as-needed, --no-as-needed, and -a.
675 One target for this option are specifications for pkg-config. When
677 used with the --libs option all possibly needed libraries are
678 listed and then possibly linked with all the time. It is better to
679 return something as follows:
680 -Wl,--push-state,--as-needed -libone -libtwo -Wl,--pop-state
682 --pop-state
684 Undoes the effect of --push-state, restores the previous values of
685 the flags governing input file handling.
686 -q
688 --emit-relocs
689 Leave relocation sections and contents in fully linked executables.
690 Post link analysis and optimization tools may need this information
691 in order to perform correct modifications of executables. This
692 results in larger executables.
693 This option is currently only supported on ELF platforms.
695 --force-dynamic
697 Force the output file to have dynamic sections. This option is
698 specific to VxWorks targets.
699 -r
701 --relocatable
702 Generate relocatable output---i.e., generate an output file that
703 can in turn serve as input to ld. This is often called partial
704 linking. As a side effect, in environments that support standard
705 Unix magic numbers, this option also sets the output file's magic
706 number to "OMAGIC". If this option is not specified, an absolute
707 file is produced. When linking C++ programs, this option will not
708 resolve references to constructors; to do that, use -Ur.
709 When an input file does not have the same format as the output
711 file, partial linking is only supported if that input file does not
712 contain any relocations. Different output formats can have further
713 restrictions; for example some "a.out"-based formats do not support
714 partial linking with input files in other formats at all.
715 This option does the same thing as -i.
717 -R filename
719 --just-symbols=filename
720 Read symbol names and their addresses from filename, but do not
721 relocate it or include it in the output. This allows your output
722 file to refer symbolically to absolute locations of memory defined
723 in other programs. You may use this option more than once.
724 For compatibility with other ELF linkers, if the -R option is
726 followed by a directory name, rather than a file name, it is
727 treated as the -rpath option.
728 -s
730 --strip-all
731 Omit all symbol information from the output file.
732 -S
734 --strip-debug
735 Omit debugger symbol information (but not all symbols) from the
736 output file.
737 --strip-discarded
739 --no-strip-discarded
740 Omit (or do not omit) global symbols defined in discarded sections.
741 Enabled by default.
742 -t
744 --trace
745 Print the names of the input files as ld processes them. If -t is
746 given twice then members within archives are also printed. -t
747 output is useful to generate a list of all the object files and
748 scripts involved in linking, for example, when packaging files for
749 a linker bug report.
750 -T scriptfile
752 --script=scriptfile
753 Use scriptfile as the linker script. This script replaces ld's
754 default linker script (rather than adding to it), unless the script
755 contains "INSERT", so commandfile must specify everything necessary
756 to describe the output file. If scriptfile does not exist in the
757 current directory, "ld" looks for it in the directories specified
758 by any preceding -L options. Multiple -T options accumulate.
759 -dT scriptfile
761 --default-script=scriptfile
762 Use scriptfile as the default linker script.
763 This option is similar to the --script option except that
765 processing of the script is delayed until after the rest of the
766 command line has been processed. This allows options placed after
767 the --default-script option on the command line to affect the
768 behaviour of the linker script, which can be important when the
769 linker command line cannot be directly controlled by the user. (eg
770 because the command line is being constructed by another tool, such
771 as gcc).
772 -u symbol
774 --undefined=symbol
775 Force symbol to be entered in the output file as an undefined
776 symbol. Doing this may, for example, trigger linking of additional
777 modules from standard libraries. -u may be repeated with different
778 option arguments to enter additional undefined symbols. This
779 option is equivalent to the "EXTERN" linker script command.
780 If this option is being used to force additional modules to be
782 pulled into the link, and if it is an error for the symbol to
783 remain undefined, then the option --require-defined should be used
784 instead.
785 --require-defined=symbol
787 Require that symbol is defined in the output file. This option is
788 the same as option --undefined except that if symbol is not defined
789 in the output file then the linker will issue an error and exit.
790 The same effect can be achieved in a linker script by using
791 "EXTERN", "ASSERT" and "DEFINED" together. This option can be used
792 multiple times to require additional symbols.
793 -Ur For programs that do not use constructors or destructors, or for
795 ELF based systems this option is equivalent to -r: it generates
796 relocatable output---i.e., an output file that can in turn serve as
797 input to ld. For other binaries however the -Ur option is similar
798 to -r but it also resolves references to constructors and
799 destructors.
800 For those systems where -r and -Ur behave differently, it does not
802 work to use -Ur on files that were themselves linked with -Ur; once
803 the constructor table has been built, it cannot be added to. Use
804 -Ur only for the last partial link, and -r for the others.
805 --orphan-handling=MODE
807 Control how orphan sections are handled. An orphan section is one
808 not specifically mentioned in a linker script.
809 MODE can have any of the following values:
811 "place"
813 Orphan sections are placed into a suitable output section
814 following the strategy described in Orphan Sections. The
815 option --unique also affects how sections are placed.
816 "discard"
818 All orphan sections are discarded, by placing them in the
819 /DISCARD/ section.
820 "warn"
822 The linker will place the orphan section as for "place" and
823 also issue a warning.
824 "error"
826 The linker will exit with an error if any orphan section is
827 found.
828 The default if --orphan-handling is not given is "place".
830 --unique[=SECTION]
832 Creates a separate output section for every input section matching
833 SECTION, or if the optional wildcard SECTION argument is missing,
834 for every orphan input section. An orphan section is one not
835 specifically mentioned in a linker script. You may use this option
836 multiple times on the command line; It prevents the normal merging
837 of input sections with the same name, overriding output section
838 assignments in a linker script.
839 -v
841 --version
842 -V Display the version number for ld. The -V option also lists the
843 supported emulations. See also the description of the
844 --enable-linker-version in Options,,Command-line Options which can
845 be used to insert the linker version string into a binary.
846 -x
848 --discard-all
849 Delete all local symbols.
850 -X
852 --discard-locals
853 Delete all temporary local symbols. (These symbols start with
854 system-specific local label prefixes, typically .L for ELF systems
855 or L for traditional a.out systems.)
856 -y symbol
858 --trace-symbol=symbol
859 Print the name of each linked file in which symbol appears. This
860 option may be given any number of times. On many systems it is
861 necessary to prepend an underscore.
862 This option is useful when you have an undefined symbol in your
864 link but don't know where the reference is coming from.
865 -Y path
867 Add path to the default library search path. This option exists
868 for Solaris compatibility.
869 -z keyword
871 The recognized keywords are:
872 call-nop=prefix-addr
874 call-nop=suffix-nop
875 call-nop=prefix-byte
876 call-nop=suffix-byte
877 Specify the 1-byte "NOP" padding when transforming indirect
878 call to a locally defined function, foo, via its GOT slot.
879 call-nop=prefix-addr generates "0x67 call foo".
880 call-nop=suffix-nop generates "call foo 0x90".
881 call-nop=prefix-byte generates "byte call foo".
882 call-nop=suffix-byte generates "call foo byte". Supported for
883 i386 and x86_64.
884 cet-report=none
886 cet-report=warning
887 cet-report=error
888 Specify how to report the missing
889 GNU_PROPERTY_X86_FEATURE_1_IBT and
890 GNU_PROPERTY_X86_FEATURE_1_SHSTK properties in input
891 .note.gnu.property section. cet-report=none, which is the
892 default, will make the linker not report missing properties in
893 input files. cet-report=warning will make the linker issue a
894 warning for missing properties in input files.
895 cet-report=error will make the linker issue an error for
896 missing properties in input files. Note that ibt will turn off
897 the missing GNU_PROPERTY_X86_FEATURE_1_IBT property report and
898 shstk will turn off the missing
899 GNU_PROPERTY_X86_FEATURE_1_SHSTK property report. Supported
900 for Linux/i386 and Linux/x86_64.
901 combreloc
903 nocombreloc
904 Combine multiple dynamic relocation sections and sort to
905 improve dynamic symbol lookup caching. Do not do this if
906 nocombreloc.
907 common
909 nocommon
910 Generate common symbols with STT_COMMON type during a
911 relocatable link. Use STT_OBJECT type if nocommon.
912 common-page-size=value
914 Set the page size most commonly used to value. Memory image
915 layout will be optimized to minimize memory pages if the system
916 is using pages of this size.
917 defs
919 Report unresolved symbol references from regular object files.
920 This is done even if the linker is creating a non-symbolic
921 shared library. This option is the inverse of -z undefs.
922 dynamic-undefined-weak
924 nodynamic-undefined-weak
925 Make undefined weak symbols dynamic when building a dynamic
926 object, if they are referenced from a regular object file and
927 not forced local by symbol visibility or versioning. Do not
928 make them dynamic if nodynamic-undefined-weak. If neither
929 option is given, a target may default to either option being in
930 force, or make some other selection of undefined weak symbols
931 dynamic. Not all targets support these options.
932 execstack
934 Marks the object as requiring executable stack.
935 global
937 This option is only meaningful when building a shared object.
938 It makes the symbols defined by this shared object available
939 for symbol resolution of subsequently loaded libraries.
940 globalaudit
942 This option is only meaningful when building a dynamic
943 executable. This option marks the executable as requiring
944 global auditing by setting the "DF_1_GLOBAUDIT" bit in the
945 "DT_FLAGS_1" dynamic tag. Global auditing requires that any
946 auditing library defined via the --depaudit or -P command-line
947 options be run for all dynamic objects loaded by the
948 application.
949 ibtplt
951 Generate Intel Indirect Branch Tracking (IBT) enabled PLT
952 entries. Supported for Linux/i386 and Linux/x86_64.
953 ibt Generate GNU_PROPERTY_X86_FEATURE_1_IBT in .note.gnu.property
955 section to indicate compatibility with IBT. This also implies
956 ibtplt. Supported for Linux/i386 and Linux/x86_64.
957 indirect-extern-access
959 noindirect-extern-access
960 Generate GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS in
961 .note.gnu.property section to indicate that object file
962 requires canonical function pointers and cannot be used with
963 copy relocation. This option also implies noextern-protected-
964 data and nocopyreloc. Supported for i386 and x86-64.
965 noindirect-extern-access removes
967 GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS from
968 .note.gnu.property section.
969 initfirst
971 This option is only meaningful when building a shared object.
972 It marks the object so that its runtime initialization will
973 occur before the runtime initialization of any other objects
974 brought into the process at the same time. Similarly the
975 runtime finalization of the object will occur after the runtime
976 finalization of any other objects.
977 interpose
979 Specify that the dynamic loader should modify its symbol search
980 order so that symbols in this shared library interpose all
981 other shared libraries not so marked.
982 unique
984 nounique
985 When generating a shared library or other dynamically loadable
986 ELF object mark it as one that should (by default) only ever be
987 loaded once, and only in the main namespace (when using
988 "dlmopen"). This is primarily used to mark fundamental
989 libraries such as libc, libpthread et al which do not usually
990 function correctly unless they are the sole instances of
991 themselves. This behaviour can be overridden by the "dlmopen"
992 caller and does not apply to certain loading mechanisms (such
993 as audit libraries).
994 lam-u48
996 Generate GNU_PROPERTY_X86_FEATURE_1_LAM_U48 in
997 .note.gnu.property section to indicate compatibility with Intel
998 LAM_U48. Supported for Linux/x86_64.
999 lam-u57
1001 Generate GNU_PROPERTY_X86_FEATURE_1_LAM_U57 in
1002 .note.gnu.property section to indicate compatibility with Intel
1003 LAM_U57. Supported for Linux/x86_64.
1004 lam-u48-report=none
1006 lam-u48-report=warning
1007 lam-u48-report=error
1008 Specify how to report the missing
1009 GNU_PROPERTY_X86_FEATURE_1_LAM_U48 property in input
1010 .note.gnu.property section. lam-u48-report=none, which is the
1011 default, will make the linker not report missing properties in
1012 input files. lam-u48-report=warning will make the linker issue
1013 a warning for missing properties in input files.
1014 lam-u48-report=error will make the linker issue an error for
1015 missing properties in input files. Supported for Linux/x86_64.
1016 lam-u57-report=none
1018 lam-u57-report=warning
1019 lam-u57-report=error
1020 Specify how to report the missing
1021 GNU_PROPERTY_X86_FEATURE_1_LAM_U57 property in input
1022 .note.gnu.property section. lam-u57-report=none, which is the
1023 default, will make the linker not report missing properties in
1024 input files. lam-u57-report=warning will make the linker issue
1025 a warning for missing properties in input files.
1026 lam-u57-report=error will make the linker issue an error for
1027 missing properties in input files. Supported for Linux/x86_64.
1028 lam-report=none
1030 lam-report=warning
1031 lam-report=error
1032 Specify how to report the missing
1033 GNU_PROPERTY_X86_FEATURE_1_LAM_U48 and
1034 GNU_PROPERTY_X86_FEATURE_1_LAM_U57 properties in input
1035 .note.gnu.property section. lam-report=none, which is the
1036 default, will make the linker not report missing properties in
1037 input files. lam-report=warning will make the linker issue a
1038 warning for missing properties in input files.
1039 lam-report=error will make the linker issue an error for
1040 missing properties in input files. Supported for Linux/x86_64.
1041 lazy
1043 When generating an executable or shared library, mark it to
1044 tell the dynamic linker to defer function call resolution to
1045 the point when the function is called (lazy binding), rather
1046 than at load time. Lazy binding is the default.
1047 loadfltr
1049 Specify that the object's filters be processed immediately at
1050 runtime.
1051 max-page-size=value
1053 Set the maximum memory page size supported to value.
1054 muldefs
1056 Allow multiple definitions.
1057 nocopyreloc
1059 Disable linker generated .dynbss variables used in place of
1060 variables defined in shared libraries. May result in dynamic
1061 text relocations.
1062 nodefaultlib
1064 Specify that the dynamic loader search for dependencies of this
1065 object should ignore any default library search paths.
1066 nodelete
1068 Specify that the object shouldn't be unloaded at runtime.
1069 nodlopen
1071 Specify that the object is not available to "dlopen".
1072 nodump
1074 Specify that the object can not be dumped by "dldump".
1075 noexecstack
1077 Marks the object as not requiring executable stack.
1078 noextern-protected-data
1080 Don't treat protected data symbols as external when building a
1081 shared library. This option overrides the linker backend
1082 default. It can be used to work around incorrect relocations
1083 against protected data symbols generated by compiler. Updates
1084 on protected data symbols by another module aren't visible to
1085 the resulting shared library. Supported for i386 and x86-64.
1086 noreloc-overflow
1088 Disable relocation overflow check. This can be used to disable
1089 relocation overflow check if there will be no dynamic
1090 relocation overflow at run-time. Supported for x86_64.
1091 now When generating an executable or shared library, mark it to
1093 tell the dynamic linker to resolve all symbols when the program
1094 is started, or when the shared library is loaded by dlopen,
1095 instead of deferring function call resolution to the point when
1096 the function is first called.
1097 origin
1099 Specify that the object requires $ORIGIN handling in paths.
1100 pack-relative-relocs
1102 nopack-relative-relocs
1103 Generate compact relative relocation in position-independent
1104 executable and shared library. It adds "DT_RELR", "DT_RELRSZ"
1105 and "DT_RELRENT" entries to the dynamic section. It is ignored
1106 when building position-dependent executable and relocatable
1107 output. nopack-relative-relocs is the default, which disables
1108 compact relative relocation. When linked against the GNU C
1109 Library, a GLIBC_ABI_DT_RELR symbol version dependency on the
1110 shared C Library is added to the output. Supported for i386
1111 and x86-64.
1112 relro
1114 norelro
1115 Create an ELF "PT_GNU_RELRO" segment header in the object.
1116 This specifies a memory segment that should be made read-only
1117 after relocation, if supported. Specifying common-page-size
1118 smaller than the system page size will render this protection
1119 ineffective. Don't create an ELF "PT_GNU_RELRO" segment if
1120 norelro.
1121 report-relative-reloc
1123 Report dynamic relative relocations generated by linker.
1124 Supported for Linux/i386 and Linux/x86_64.
1125 sectionheader
1127 nosectionheader
1128 Generate section header. Don't generate section header if
1129 nosectionheader is used. sectionheader is the default.
1130 separate-code
1132 noseparate-code
1133 Create separate code "PT_LOAD" segment header in the object.
1134 This specifies a memory segment that should contain only
1135 instructions and must be in wholly disjoint pages from any
1136 other data. Don't create separate code "PT_LOAD" segment if
1137 noseparate-code is used.
1138 shstk
1140 Generate GNU_PROPERTY_X86_FEATURE_1_SHSTK in .note.gnu.property
1141 section to indicate compatibility with Intel Shadow Stack.
1142 Supported for Linux/i386 and Linux/x86_64.
1143 stack-size=value
1145 Specify a stack size for an ELF "PT_GNU_STACK" segment.
1146 Specifying zero will override any default non-zero sized
1147 "PT_GNU_STACK" segment creation.
1148 start-stop-gc
1150 nostart-stop-gc
1151 When --gc-sections is in effect, a reference from a retained
1152 section to "__start_SECNAME" or "__stop_SECNAME" causes all
1153 input sections named "SECNAME" to also be retained, if
1154 "SECNAME" is representable as a C identifier and either
1155 "__start_SECNAME" or "__stop_SECNAME" is synthesized by the
1156 linker. -z start-stop-gc disables this effect, allowing
1157 sections to be garbage collected as if the special synthesized
1158 symbols were not defined. -z start-stop-gc has no effect on a
1159 definition of "__start_SECNAME" or "__stop_SECNAME" in an
1160 object file or linker script. Such a definition will prevent
1161 the linker providing a synthesized "__start_SECNAME" or
1162 "__stop_SECNAME" respectively, and therefore the special
1163 treatment by garbage collection for those references.
1164 start-stop-visibility=value
1166 Specify the ELF symbol visibility for synthesized
1167 "__start_SECNAME" and "__stop_SECNAME" symbols. value must be
1168 exactly default, internal, hidden, or protected. If no -z
1169 start-stop-visibility option is given, protected is used for
1170 compatibility with historical practice. However, it's highly
1171 recommended to use -z start-stop-visibility=hidden in new
1172 programs and shared libraries so that these symbols are not
1173 exported between shared objects, which is not usually what's
1174 intended.
1175 text
1177 notext
1178 textoff
1179 Report an error if DT_TEXTREL is set, i.e., if the position-
1180 independent or shared object has dynamic relocations in read-
1181 only sections. Don't report an error if notext or textoff.
1182 undefs
1184 Do not report unresolved symbol references from regular object
1185 files, either when creating an executable, or when creating a
1186 shared library. This option is the inverse of -z defs.
1187 unique-symbol
1189 nounique-symbol
1190 Avoid duplicated local symbol names in the symbol string table.
1191 Append "."number"" to duplicated local symbol names if unique-
1192 symbol is used. nounique-symbol is the default.
1193 x86-64-baseline
1195 x86-64-v2
1196 x86-64-v3
1197 x86-64-v4
1198 Specify the x86-64 ISA level needed in .note.gnu.property
1199 section. x86-64-baseline generates
1200 "GNU_PROPERTY_X86_ISA_1_BASELINE". x86-64-v2 generates
1201 "GNU_PROPERTY_X86_ISA_1_V2". x86-64-v3 generates
1202 "GNU_PROPERTY_X86_ISA_1_V3". x86-64-v4 generates
1203 "GNU_PROPERTY_X86_ISA_1_V4". Supported for Linux/i386 and
1204 Linux/x86_64.
1205 Other keywords are ignored for Solaris compatibility.
1207 -( archives -)
1209 --start-group archives --end-group
1210 The archives should be a list of archive files. They may be either
1211 explicit file names, or -l options.
1212 The specified archives are searched repeatedly until no new
1214 undefined references are created. Normally, an archive is searched
1215 only once in the order that it is specified on the command line.
1216 If a symbol in that archive is needed to resolve an undefined
1217 symbol referred to by an object in an archive that appears later on
1218 the command line, the linker would not be able to resolve that
1219 reference. By grouping the archives, they will all be searched
1220 repeatedly until all possible references are resolved.
1221 Using this option has a significant performance cost. It is best
1223 to use it only when there are unavoidable circular references
1224 between two or more archives.
1225 --accept-unknown-input-arch
1227 --no-accept-unknown-input-arch
1228 Tells the linker to accept input files whose architecture cannot be
1229 recognised. The assumption is that the user knows what they are
1230 doing and deliberately wants to link in these unknown input files.
1231 This was the default behaviour of the linker, before release 2.14.
1232 The default behaviour from release 2.14 onwards is to reject such
1233 input files, and so the --accept-unknown-input-arch option has been
1234 added to restore the old behaviour.
1235 --as-needed
1237 --no-as-needed
1238 This option affects ELF DT_NEEDED tags for dynamic libraries
1239 mentioned on the command line after the --as-needed option.
1240 Normally the linker will add a DT_NEEDED tag for each dynamic
1241 library mentioned on the command line, regardless of whether the
1242 library is actually needed or not. --as-needed causes a DT_NEEDED
1243 tag to only be emitted for a library that at that point in the link
1244 satisfies a non-weak undefined symbol reference from a regular
1245 object file or, if the library is not found in the DT_NEEDED lists
1246 of other needed libraries, a non-weak undefined symbol reference
1247 from another needed dynamic library. Object files or libraries
1248 appearing on the command line after the library in question do not
1249 affect whether the library is seen as needed. This is similar to
1250 the rules for extraction of object files from archives.
1251 --no-as-needed restores the default behaviour.
1252 Note: On Linux based systems the --as-needed option also has an
1254 affect on the behaviour of the --rpath and --rpath-link options.
1255 See the description of --rpath-link for more details.
1256 --add-needed
1258 --no-add-needed
1259 These two options have been deprecated because of the similarity of
1260 their names to the --as-needed and --no-as-needed options. They
1261 have been replaced by --copy-dt-needed-entries and
1262 --no-copy-dt-needed-entries.
1263 -assert keyword
1265 This option is ignored for SunOS compatibility.
1266 -Bdynamic
1268 -dy
1269 -call_shared
1270 Link against dynamic libraries. This is only meaningful on
1271 platforms for which shared libraries are supported. This option is
1272 normally the default on such platforms. The different variants of
1273 this option are for compatibility with various systems. You may
1274 use this option multiple times on the command line: it affects
1275 library searching for -l options which follow it.
1276 -Bgroup
1278 Set the "DF_1_GROUP" flag in the "DT_FLAGS_1" entry in the dynamic
1279 section. This causes the runtime linker to handle lookups in this
1280 object and its dependencies to be performed only inside the group.
1281 --unresolved-symbols=report-all is implied. This option is only
1282 meaningful on ELF platforms which support shared libraries.
1283 -Bstatic
1285 -dn
1286 -non_shared
1287 -static
1288 Do not link against shared libraries. This is only meaningful on
1289 platforms for which shared libraries are supported. The different
1290 variants of this option are for compatibility with various systems.
1291 You may use this option multiple times on the command line: it
1292 affects library searching for -l options which follow it. This
1293 option also implies --unresolved-symbols=report-all. This option
1294 can be used with -shared. Doing so means that a shared library is
1295 being created but that all of the library's external references
1296 must be resolved by pulling in entries from static libraries.
1297 -Bsymbolic
1299 When creating a shared library, bind references to global symbols
1300 to the definition within the shared library, if any. Normally, it
1301 is possible for a program linked against a shared library to
1302 override the definition within the shared library. This option is
1303 only meaningful on ELF platforms which support shared libraries.
1304 -Bsymbolic-functions
1306 When creating a shared library, bind references to global function
1307 symbols to the definition within the shared library, if any. This
1308 option is only meaningful on ELF platforms which support shared
1309 libraries.
1310 -Bno-symbolic
1312 This option can cancel previously specified -Bsymbolic and
1313 -Bsymbolic-functions.
1314 --dynamic-list=dynamic-list-file
1316 Specify the name of a dynamic list file to the linker. This is
1317 typically used when creating shared libraries to specify a list of
1318 global symbols whose references shouldn't be bound to the
1319 definition within the shared library, or creating dynamically
1320 linked executables to specify a list of symbols which should be
1321 added to the symbol table in the executable. This option is only
1322 meaningful on ELF platforms which support shared libraries.
1323 The format of the dynamic list is the same as the version node
1325 without scope and node name. See VERSION for more information.
1326 --dynamic-list-data
1328 Include all global data symbols to the dynamic list.
1329 --dynamic-list-cpp-new
1331 Provide the builtin dynamic list for C++ operator new and delete.
1332 It is mainly useful for building shared libstdc++.
1333 --dynamic-list-cpp-typeinfo
1335 Provide the builtin dynamic list for C++ runtime type
1336 identification.
1337 --check-sections
1339 --no-check-sections
1340 Asks the linker not to check section addresses after they have been
1341 assigned to see if there are any overlaps. Normally the linker
1342 will perform this check, and if it finds any overlaps it will
1343 produce suitable error messages. The linker does know about, and
1344 does make allowances for sections in overlays. The default
1345 behaviour can be restored by using the command-line switch
1346 --check-sections. Section overlap is not usually checked for
1347 relocatable links. You can force checking in that case by using
1348 the --check-sections option.
1349 --copy-dt-needed-entries
1351 --no-copy-dt-needed-entries
1352 This option affects the treatment of dynamic libraries referred to
1353 by DT_NEEDED tags inside ELF dynamic libraries mentioned on the
1354 command line. Normally the linker won't add a DT_NEEDED tag to the
1355 output binary for each library mentioned in a DT_NEEDED tag in an
1356 input dynamic library. With --copy-dt-needed-entries specified on
1357 the command line however any dynamic libraries that follow it will
1358 have their DT_NEEDED entries added. The default behaviour can be
1359 restored with --no-copy-dt-needed-entries.
1360 This option also has an effect on the resolution of symbols in
1362 dynamic libraries. With --copy-dt-needed-entries dynamic libraries
1363 mentioned on the command line will be recursively searched,
1364 following their DT_NEEDED tags to other libraries, in order to
1365 resolve symbols required by the output binary. With the default
1366 setting however the searching of dynamic libraries that follow it
1367 will stop with the dynamic library itself. No DT_NEEDED links will
1368 be traversed to resolve symbols.
1369 --cref
1371 Output a cross reference table. If a linker map file is being
1372 generated, the cross reference table is printed to the map file.
1373 Otherwise, it is printed on the standard output.
1374 The format of the table is intentionally simple, so that it may be
1376 easily processed by a script if necessary. The symbols are printed
1377 out, sorted by name. For each symbol, a list of file names is
1378 given. If the symbol is defined, the first file listed is the
1379 location of the definition. If the symbol is defined as a common
1380 value then any files where this happens appear next. Finally any
1381 files that reference the symbol are listed.
1382 --ctf-variables
1384 --no-ctf-variables
1385 The CTF debuginfo format supports a section which encodes the names
1386 and types of variables found in the program which do not appear in
1387 any symbol table. These variables clearly cannot be looked up by
1388 address by conventional debuggers, so the space used for their
1389 types and names is usually wasted: the types are usually small but
1390 the names are often not. --ctf-variables causes the generation of
1391 such a section. The default behaviour can be restored with
1392 --no-ctf-variables.
1393 --ctf-share-types=method
1395 Adjust the method used to share types between translation units in
1396 CTF.
1397 share-unconflicted
1399 Put all types that do not have ambiguous definitions into the
1400 shared dictionary, where debuggers can easily access them, even
1401 if they only occur in one translation unit. This is the
1402 default.
1403 share-duplicated
1405 Put only types that occur in multiple translation units into
1406 the shared dictionary: types with only one definition go into
1407 per-translation-unit dictionaries. Types with ambiguous
1408 definitions in multiple translation units always go into per-
1409 translation-unit dictionaries. This tends to make the CTF
1410 larger, but may reduce the amount of CTF in the shared
1411 dictionary. For very large projects this may speed up opening
1412 the CTF and save memory in the CTF consumer at runtime.
1413 --no-define-common
1415 This option inhibits the assignment of addresses to common symbols.
1416 The script command "INHIBIT_COMMON_ALLOCATION" has the same effect.
1417 The --no-define-common option allows decoupling the decision to
1419 assign addresses to Common symbols from the choice of the output
1420 file type; otherwise a non-Relocatable output type forces assigning
1421 addresses to Common symbols. Using --no-define-common allows
1422 Common symbols that are referenced from a shared library to be
1423 assigned addresses only in the main program. This eliminates the
1424 unused duplicate space in the shared library, and also prevents any
1425 possible confusion over resolving to the wrong duplicate when there
1426 are many dynamic modules with specialized search paths for runtime
1427 symbol resolution.
1428 --force-group-allocation
1430 This option causes the linker to place section group members like
1431 normal input sections, and to delete the section groups. This is
1432 the default behaviour for a final link but this option can be used
1433 to change the behaviour of a relocatable link (-r). The script
1434 command "FORCE_GROUP_ALLOCATION" has the same effect.
1435 --defsym=symbol=expression
1437 Create a global symbol in the output file, containing the absolute
1438 address given by expression. You may use this option as many times
1439 as necessary to define multiple symbols in the command line. A
1440 limited form of arithmetic is supported for the expression in this
1441 context: you may give a hexadecimal constant or the name of an
1442 existing symbol, or use "+" and "-" to add or subtract hexadecimal
1443 constants or symbols. If you need more elaborate expressions,
1444 consider using the linker command language from a script. Note:
1445 there should be no white space between symbol, the equals sign
1446 ("="), and expression.
1447 The linker processes --defsym arguments and -T arguments in order,
1449 placing --defsym before -T will define the symbol before the linker
1450 script from -T is processed, while placing --defsym after -T will
1451 define the symbol after the linker script has been processed. This
1452 difference has consequences for expressions within the linker
1453 script that use the --defsym symbols, which order is correct will
1454 depend on what you are trying to achieve.
1455 --demangle[=style]
1457 --no-demangle
1458 These options control whether to demangle symbol names in error
1459 messages and other output. When the linker is told to demangle, it
1460 tries to present symbol names in a readable fashion: it strips
1461 leading underscores if they are used by the object file format, and
1462 converts C++ mangled symbol names into user readable names.
1463 Different compilers have different mangling styles. The optional
1464 demangling style argument can be used to choose an appropriate
1465 demangling style for your compiler. The linker will demangle by
1466 default unless the environment variable COLLECT_NO_DEMANGLE is set.
1467 These options may be used to override the default.
1468 -Ifile
1470 --dynamic-linker=file
1471 Set the name of the dynamic linker. This is only meaningful when
1472 generating dynamically linked ELF executables. The default dynamic
1473 linker is normally correct; don't use this unless you know what you
1474 are doing.
1475 --no-dynamic-linker
1477 When producing an executable file, omit the request for a dynamic
1478 linker to be used at load-time. This is only meaningful for ELF
1479 executables that contain dynamic relocations, and usually requires
1480 entry point code that is capable of processing these relocations.
1481 --embedded-relocs
1483 This option is similar to the --emit-relocs option except that the
1484 relocs are stored in a target-specific section. This option is
1485 only supported by the BFIN, CR16 and M68K targets.
1486 --disable-multiple-abs-defs
1488 Do not allow multiple definitions with symbols included in filename
1489 invoked by -R or --just-symbols
1490 --fatal-warnings
1492 --no-fatal-warnings
1493 Treat all warnings as errors. The default behaviour can be
1494 restored with the option --no-fatal-warnings.
1495 -w
1497 --no-warnings
1498 Do not display any warning or error messages. This overrides
1499 --fatal-warnings if it has been enabled. This option can be used
1500 when it is known that the output binary will not work, but there is
1501 still a need to create it.
1502 --force-exe-suffix
1504 Make sure that an output file has a .exe suffix.
1505 If a successfully built fully linked output file does not have a
1507 ".exe" or ".dll" suffix, this option forces the linker to copy the
1508 output file to one of the same name with a ".exe" suffix. This
1509 option is useful when using unmodified Unix makefiles on a
1510 Microsoft Windows host, since some versions of Windows won't run an
1511 image unless it ends in a ".exe" suffix.
1512 --gc-sections
1514 --no-gc-sections
1515 Enable garbage collection of unused input sections. It is ignored
1516 on targets that do not support this option. The default behaviour
1517 (of not performing this garbage collection) can be restored by
1518 specifying --no-gc-sections on the command line. Note that garbage
1519 collection for COFF and PE format targets is supported, but the
1520 implementation is currently considered to be experimental.
1521 --gc-sections decides which input sections are used by examining
1523 symbols and relocations. The section containing the entry symbol
1524 and all sections containing symbols undefined on the command-line
1525 will be kept, as will sections containing symbols referenced by
1526 dynamic objects. Note that when building shared libraries, the
1527 linker must assume that any visible symbol is referenced. Once
1528 this initial set of sections has been determined, the linker
1529 recursively marks as used any section referenced by their
1530 relocations. See --entry, --undefined, and --gc-keep-exported.
1531 This option can be set when doing a partial link (enabled with
1533 option -r). In this case the root of symbols kept must be
1534 explicitly specified either by one of the options --entry,
1535 --undefined, or --gc-keep-exported or by a "ENTRY" command in the
1536 linker script.
1537 As a GNU extension, ELF input sections marked with the
1539 "SHF_GNU_RETAIN" flag will not be garbage collected.
1540 --print-gc-sections
1542 --no-print-gc-sections
1543 List all sections removed by garbage collection. The listing is
1544 printed on stderr. This option is only effective if garbage
1545 collection has been enabled via the --gc-sections) option. The
1546 default behaviour (of not listing the sections that are removed)
1547 can be restored by specifying --no-print-gc-sections on the command
1548 line.
1549 --gc-keep-exported
1551 When --gc-sections is enabled, this option prevents garbage
1552 collection of unused input sections that contain global symbols
1553 having default or protected visibility. This option is intended to
1554 be used for executables where unreferenced sections would otherwise
1555 be garbage collected regardless of the external visibility of
1556 contained symbols. Note that this option has no effect when
1557 linking shared objects since it is already the default behaviour.
1558 This option is only supported for ELF format targets.
1559 --print-output-format
1561 Print the name of the default output format (perhaps influenced by
1562 other command-line options). This is the string that would appear
1563 in an "OUTPUT_FORMAT" linker script command.
1564 --print-memory-usage
1566 Print used size, total size and used size of memory regions created
1567 with the MEMORY command. This is useful on embedded targets to
1568 have a quick view of amount of free memory. The format of the
1569 output has one headline and one line per region. It is both human
1570 readable and easily parsable by tools. Here is an example of an
1571 output:
1572 Memory region Used Size Region Size %age Used
1574 ROM: 256 KB 1 MB 25.00%
1575 RAM: 32 B 2 GB 0.00%
1576 --help
1578 Print a summary of the command-line options on the standard output
1579 and exit.
1580 --target-help
1582 Print a summary of all target-specific options on the standard
1583 output and exit.
1584 -Map=mapfile
1586 Print a link map to the file mapfile. See the description of the
1587 -M option, above. If mapfile is just the character "-" then the
1588 map will be written to stdout.
1589 Specifying a directory as mapfile causes the linker map to be
1591 written as a file inside the directory. Normally name of the file
1592 inside the directory is computed as the basename of the output file
1593 with ".map" appended. If however the special character "%" is
1594 used then this will be replaced by the full path of the output
1595 file. Additionally if there are any characters after the % symbol
1596 then ".map" will no longer be appended.
1597 -o foo.exe -Map=bar [Creates ./bar]
1599 -o ../dir/foo.exe -Map=bar [Creates ./bar]
1600 -o foo.exe -Map=../dir [Creates ../dir/foo.exe.map]
1601 -o ../dir2/foo.exe -Map=../dir [Creates ../dir/foo.exe.map]
1602 -o foo.exe -Map=% [Creates ./foo.exe.map]
1603 -o ../dir/foo.exe -Map=% [Creates ../dir/foo.exe.map]
1604 -o foo.exe -Map=%.bar [Creates ./foo.exe.bar]
1605 -o ../dir/foo.exe -Map=%.bar [Creates ../dir/foo.exe.bar]
1606 -o ../dir2/foo.exe -Map=../dir/% [Creates ../dir/../dir2/foo.exe.map]
1607 -o ../dir2/foo.exe -Map=../dir/%.bar [Creates ../dir/../dir2/foo.exe.bar]
1608 It is an error to specify more than one "%" character.
1610 If the map file already exists then it will be overwritten by this
1612 operation.
1613 --no-keep-memory
1615 ld normally optimizes for speed over memory usage by caching the
1616 symbol tables of input files in memory. This option tells ld to
1617 instead optimize for memory usage, by rereading the symbol tables
1618 as necessary. This may be required if ld runs out of memory space
1619 while linking a large executable.
1620 --no-undefined
1622 -z defs
1623 Report unresolved symbol references from regular object files.
1624 This is done even if the linker is creating a non-symbolic shared
1625 library. The switch --[no-]allow-shlib-undefined controls the
1626 behaviour for reporting unresolved references found in shared
1627 libraries being linked in.
1628 The effects of this option can be reverted by using "-z undefs".
1630 --allow-multiple-definition
1632 -z muldefs
1633 Normally when a symbol is defined multiple times, the linker will
1634 report a fatal error. These options allow multiple definitions and
1635 the first definition will be used.
1636 --allow-shlib-undefined
1638 --no-allow-shlib-undefined
1639 Allows or disallows undefined symbols in shared libraries. This
1640 switch is similar to --no-undefined except that it determines the
1641 behaviour when the undefined symbols are in a shared library rather
1642 than a regular object file. It does not affect how undefined
1643 symbols in regular object files are handled.
1644 The default behaviour is to report errors for any undefined symbols
1646 referenced in shared libraries if the linker is being used to
1647 create an executable, but to allow them if the linker is being used
1648 to create a shared library.
1649 The reasons for allowing undefined symbol references in shared
1651 libraries specified at link time are that:
1652 • A shared library specified at link time may not be the same as
1654 the one that is available at load time, so the symbol might
1655 actually be resolvable at load time.
1656 • There are some operating systems, eg BeOS and HPPA, where
1658 undefined symbols in shared libraries are normal.
1659 The BeOS kernel for example patches shared libraries at load
1661 time to select whichever function is most appropriate for the
1662 current architecture. This is used, for example, to
1663 dynamically select an appropriate memset function.
1664 --error-handling-script=scriptname
1666 If this option is provided then the linker will invoke scriptname
1667 whenever an error is encountered. Currently however only two kinds
1668 of error are supported: missing symbols and missing libraries. Two
1669 arguments will be passed to script: the keyword "undefined-symbol"
1670 or `missing-lib" and the name of the undefined symbol or missing
1671 library. The intention is that the script will provide suggestions
1672 to the user as to where the symbol or library might be found.
1673 After the script has finished then the normal linker error message
1674 will be displayed.
1675 The availability of this option is controlled by a configure time
1677 switch, so it may not be present in specific implementations.
1678 --no-undefined-version
1680 Normally when a symbol has an undefined version, the linker will
1681 ignore it. This option disallows symbols with undefined version and
1682 a fatal error will be issued instead.
1683 --default-symver
1685 Create and use a default symbol version (the soname) for
1686 unversioned exported symbols.
1687 --default-imported-symver
1689 Create and use a default symbol version (the soname) for
1690 unversioned imported symbols.
1691 --no-warn-mismatch
1693 Normally ld will give an error if you try to link together input
1694 files that are mismatched for some reason, perhaps because they
1695 have been compiled for different processors or for different
1696 endiannesses. This option tells ld that it should silently permit
1697 such possible errors. This option should only be used with care,
1698 in cases when you have taken some special action that ensures that
1699 the linker errors are inappropriate.
1700 --no-warn-search-mismatch
1702 Normally ld will give a warning if it finds an incompatible library
1703 during a library search. This option silences the warning.
1704 --no-whole-archive
1706 Turn off the effect of the --whole-archive option for subsequent
1707 archive files.
1708 --noinhibit-exec
1710 Retain the executable output file whenever it is still usable.
1711 Normally, the linker will not produce an output file if it
1712 encounters errors during the link process; it exits without writing
1713 an output file when it issues any error whatsoever.
1714 -nostdlib
1716 Only search library directories explicitly specified on the command
1717 line. Library directories specified in linker scripts (including
1718 linker scripts specified on the command line) are ignored.
1719 --oformat=output-format
1721 ld may be configured to support more than one kind of object file.
1722 If your ld is configured this way, you can use the --oformat option
1723 to specify the binary format for the output object file. Even when
1724 ld is configured to support alternative object formats, you don't
1725 usually need to specify this, as ld should be configured to produce
1726 as a default output format the most usual format on each machine.
1727 output-format is a text string, the name of a particular format
1728 supported by the BFD libraries. (You can list the available binary
1729 formats with objdump -i.) The script command "OUTPUT_FORMAT" can
1730 also specify the output format, but this option overrides it.
1731 --out-implib file
1733 Create an import library in file corresponding to the executable
1734 the linker is generating (eg. a DLL or ELF program). This import
1735 library (which should be called "*.dll.a" or "*.a" for DLLs) may be
1736 used to link clients against the generated executable; this
1737 behaviour makes it possible to skip a separate import library
1738 creation step (eg. "dlltool" for DLLs). This option is only
1739 available for the i386 PE and ELF targetted ports of the linker.
1740 -pie
1742 --pic-executable
1743 Create a position independent executable. This is currently only
1744 supported on ELF platforms. Position independent executables are
1745 similar to shared libraries in that they are relocated by the
1746 dynamic linker to the virtual address the OS chooses for them
1747 (which can vary between invocations). Like normal dynamically
1748 linked executables they can be executed and symbols defined in the
1749 executable cannot be overridden by shared libraries.
1750 -no-pie
1752 Create a position dependent executable. This is the default.
1753 -qmagic
1755 This option is ignored for Linux compatibility.
1756 -Qy This option is ignored for SVR4 compatibility.
1758 --relax
1760 --no-relax
1761 An option with machine dependent effects. This option is only
1762 supported on a few targets.
1763 On some platforms the --relax option performs target specific,
1765 global optimizations that become possible when the linker resolves
1766 addressing in the program, such as relaxing address modes,
1767 synthesizing new instructions, selecting shorter version of current
1768 instructions, and combining constant values.
1769 On some platforms these link time global optimizations may make
1771 symbolic debugging of the resulting executable impossible. This is
1772 known to be the case for the Matsushita MN10200 and MN10300 family
1773 of processors.
1774 On platforms where the feature is supported, the option --no-relax
1776 will disable it.
1777 On platforms where the feature is not supported, both --relax and
1779 --no-relax are accepted, but ignored.
1780 --retain-symbols-file=filename
1782 Retain only the symbols listed in the file filename, discarding all
1783 others. filename is simply a flat file, with one symbol name per
1784 line. This option is especially useful in environments (such as
1785 VxWorks) where a large global symbol table is accumulated
1786 gradually, to conserve run-time memory.
1787 --retain-symbols-file does not discard undefined symbols, or
1789 symbols needed for relocations.
1790 You may only specify --retain-symbols-file once in the command
1792 line. It overrides -s and -S.
1793 -rpath=dir
1795 Add a directory to the runtime library search path. This is used
1796 when linking an ELF executable with shared objects. All -rpath
1797 arguments are concatenated and passed to the runtime linker, which
1798 uses them to locate shared objects at runtime.
1799 The -rpath option is also used when locating shared objects which
1801 are needed by shared objects explicitly included in the link; see
1802 the description of the -rpath-link option. Searching -rpath in
1803 this way is only supported by native linkers and cross linkers
1804 which have been configured with the --with-sysroot option.
1805 If -rpath is not used when linking an ELF executable, the contents
1807 of the environment variable "LD_RUN_PATH" will be used if it is
1808 defined.
1809 The -rpath option may also be used on SunOS. By default, on SunOS,
1811 the linker will form a runtime search path out of all the -L
1812 options it is given. If a -rpath option is used, the runtime
1813 search path will be formed exclusively using the -rpath options,
1814 ignoring the -L options. This can be useful when using gcc, which
1815 adds many -L options which may be on NFS mounted file systems.
1816 For compatibility with other ELF linkers, if the -R option is
1818 followed by a directory name, rather than a file name, it is
1819 treated as the -rpath option.
1820 -rpath-link=dir
1822 When using ELF or SunOS, one shared library may require another.
1823 This happens when an "ld -shared" link includes a shared library as
1824 one of the input files.
1825 When the linker encounters such a dependency when doing a non-
1827 shared, non-relocatable link, it will automatically try to locate
1828 the required shared library and include it in the link, if it is
1829 not included explicitly. In such a case, the -rpath-link option
1830 specifies the first set of directories to search. The -rpath-link
1831 option may specify a sequence of directory names either by
1832 specifying a list of names separated by colons, or by appearing
1833 multiple times.
1834 The tokens $ORIGIN and $LIB can appear in these search directories.
1836 They will be replaced by the full path to the directory containing
1837 the program or shared object in the case of $ORIGIN and either lib
1838 - for 32-bit binaries - or lib64 - for 64-bit binaries - in the
1839 case of $LIB.
1840 The alternative form of these tokens - ${ORIGIN} and ${LIB} can
1842 also be used. The token $PLATFORM is not supported.
1843 This option should be used with caution as it overrides the search
1845 path that may have been hard compiled into a shared library. In
1846 such a case it is possible to use unintentionally a different
1847 search path than the runtime linker would do.
1848 The linker uses the following search paths to locate required
1850 shared libraries:
1851 1. Any directories specified by -rpath-link options.
1853 2. Any directories specified by -rpath options. The difference
1855 between -rpath and -rpath-link is that directories specified by
1856 -rpath options are included in the executable and used at
1857 runtime, whereas the -rpath-link option is only effective at
1858 link time. Searching -rpath in this way is only supported by
1859 native linkers and cross linkers which have been configured
1860 with the --with-sysroot option.
1861 3. On an ELF system, for native linkers, if the -rpath and
1863 -rpath-link options were not used, search the contents of the
1864 environment variable "LD_RUN_PATH".
1865 4. On SunOS, if the -rpath option was not used, search any
1867 directories specified using -L options.
1868 5. For a native linker, search the contents of the environment
1870 variable "LD_LIBRARY_PATH".
1871 6. For a native ELF linker, the directories in "DT_RUNPATH" or
1873 "DT_RPATH" of a shared library are searched for shared
1874 libraries needed by it. The "DT_RPATH" entries are ignored if
1875 "DT_RUNPATH" entries exist.
1876 7. For a linker for a Linux system, if the file /etc/ld.so.conf
1878 exists, the list of directories found in that file. Note: the
1879 path to this file is prefixed with the "sysroot" value, if that
1880 is defined, and then any "prefix" string if the linker was
1881 configured with the --prefix=<path> option.
1882 8. For a native linker on a FreeBSD system, any directories
1884 specified by the "_PATH_ELF_HINTS" macro defined in the
1885 elf-hints.h header file.
1886 9. Any directories specified by a "SEARCH_DIR" command in a linker
1888 script given on the command line, including scripts specified
1889 by -T (but not -dT).
1890 10. The default directories, normally /lib and /usr/lib.
1892 11. Any directories specified by a plugin
1894 LDPT_SET_EXTRA_LIBRARY_PATH.
1895 12. Any directories specified by a "SEARCH_DIR" command in a
1897 default linker script.
1898 Note however on Linux based systems there is an additional caveat:
1900 If the --as-needed option is active and a shared library is located
1901 which would normally satisfy the search and this library does not
1902 have DT_NEEDED tag for libc.so and there is a shared library later
1903 on in the set of search directories which also satisfies the search
1904 and this second shared library does have a DT_NEEDED tag for
1905 libc.so then the second library will be selected instead of the
1906 first.
1907 If the required shared library is not found, the linker will issue
1909 a warning and continue with the link.
1910 -shared
1912 -Bshareable
1913 Create a shared library. This is currently only supported on ELF,
1914 XCOFF and SunOS platforms. On SunOS, the linker will automatically
1915 create a shared library if the -e option is not used and there are
1916 undefined symbols in the link.
1917 --sort-common
1919 --sort-common=ascending
1920 --sort-common=descending
1921 This option tells ld to sort the common symbols by alignment in
1922 ascending or descending order when it places them in the
1923 appropriate output sections. The symbol alignments considered are
1924 sixteen-byte or larger, eight-byte, four-byte, two-byte, and one-
1925 byte. This is to prevent gaps between symbols due to alignment
1926 constraints. If no sorting order is specified, then descending
1927 order is assumed.
1928 --sort-section=name
1930 This option will apply "SORT_BY_NAME" to all wildcard section
1931 patterns in the linker script.
1932 --sort-section=alignment
1934 This option will apply "SORT_BY_ALIGNMENT" to all wildcard section
1935 patterns in the linker script.
1936 --spare-dynamic-tags=count
1938 This option specifies the number of empty slots to leave in the
1939 .dynamic section of ELF shared objects. Empty slots may be needed
1940 by post processing tools, such as the prelinker. The default is 5.
1941 --split-by-file[=size]
1943 Similar to --split-by-reloc but creates a new output section for
1944 each input file when size is reached. size defaults to a size of 1
1945 if not given.
1946 --split-by-reloc[=count]
1948 Tries to creates extra sections in the output file so that no
1949 single output section in the file contains more than count
1950 relocations. This is useful when generating huge relocatable files
1951 for downloading into certain real time kernels with the COFF object
1952 file format; since COFF cannot represent more than 65535
1953 relocations in a single section. Note that this will fail to work
1954 with object file formats which do not support arbitrary sections.
1955 The linker will not split up individual input sections for
1956 redistribution, so if a single input section contains more than
1957 count relocations one output section will contain that many
1958 relocations. count defaults to a value of 32768.
1959 --stats
1961 Compute and display statistics about the operation of the linker,
1962 such as execution time and memory usage.
1963 --sysroot=directory
1965 Use directory as the location of the sysroot, overriding the
1966 configure-time default. This option is only supported by linkers
1967 that were configured using --with-sysroot.
1968 --task-link
1970 This is used by COFF/PE based targets to create a task-linked
1971 object file where all of the global symbols have been converted to
1972 statics.
1973 --traditional-format
1975 For some targets, the output of ld is different in some ways from
1976 the output of some existing linker. This switch requests ld to use
1977 the traditional format instead.
1978 For example, on SunOS, ld combines duplicate entries in the symbol
1980 string table. This can reduce the size of an output file with full
1981 debugging information by over 30 percent. Unfortunately, the SunOS
1982 "dbx" program can not read the resulting program ("gdb" has no
1983 trouble). The --traditional-format switch tells ld to not combine
1984 duplicate entries.
1985 --section-start=sectionname=org
1987 Locate a section in the output file at the absolute address given
1988 by org. You may use this option as many times as necessary to
1989 locate multiple sections in the command line. org must be a single
1990 hexadecimal integer; for compatibility with other linkers, you may
1991 omit the leading 0x usually associated with hexadecimal values.
1992 Note: there should be no white space between sectionname, the
1993 equals sign ("="), and org.
1994 -Tbss=org
1996 -Tdata=org
1997 -Ttext=org
1998 Same as --section-start, with ".bss", ".data" or ".text" as the
1999 sectionname.
2000 -Ttext-segment=org
2002 When creating an ELF executable, it will set the address of the
2003 first byte of the text segment.
2004 -Trodata-segment=org
2006 When creating an ELF executable or shared object for a target where
2007 the read-only data is in its own segment separate from the
2008 executable text, it will set the address of the first byte of the
2009 read-only data segment.
2010 -Tldata-segment=org
2012 When creating an ELF executable or shared object for x86-64 medium
2013 memory model, it will set the address of the first byte of the
2014 ldata segment.
2015 --unresolved-symbols=method
2017 Determine how to handle unresolved symbols. There are four
2018 possible values for method:
2019 ignore-all
2021 Do not report any unresolved symbols.
2022 report-all
2024 Report all unresolved symbols. This is the default.
2025 ignore-in-object-files
2027 Report unresolved symbols that are contained in shared
2028 libraries, but ignore them if they come from regular object
2029 files.
2030 ignore-in-shared-libs
2032 Report unresolved symbols that come from regular object files,
2033 but ignore them if they come from shared libraries. This can
2034 be useful when creating a dynamic binary and it is known that
2035 all the shared libraries that it should be referencing are
2036 included on the linker's command line.
2037 The behaviour for shared libraries on their own can also be
2039 controlled by the --[no-]allow-shlib-undefined option.
2040 Normally the linker will generate an error message for each
2042 reported unresolved symbol but the option --warn-unresolved-symbols
2043 can change this to a warning.
2044 --dll-verbose
2046 --verbose[=NUMBER]
2047 Display the version number for ld and list the linker emulations
2048 supported. Display which input files can and cannot be opened.
2049 Display the linker script being used by the linker. If the optional
2050 NUMBER argument > 1, plugin symbol status will also be displayed.
2051 --version-script=version-scriptfile
2053 Specify the name of a version script to the linker. This is
2054 typically used when creating shared libraries to specify additional
2055 information about the version hierarchy for the library being
2056 created. This option is only fully supported on ELF platforms
2057 which support shared libraries; see VERSION. It is partially
2058 supported on PE platforms, which can use version scripts to filter
2059 symbol visibility in auto-export mode: any symbols marked local in
2060 the version script will not be exported.
2061 --warn-common
2063 Warn when a common symbol is combined with another common symbol or
2064 with a symbol definition. Unix linkers allow this somewhat sloppy
2065 practice, but linkers on some other operating systems do not. This
2066 option allows you to find potential problems from combining global
2067 symbols. Unfortunately, some C libraries use this practice, so you
2068 may get some warnings about symbols in the libraries as well as in
2069 your programs.
2070 There are three kinds of global symbols, illustrated here by C
2072 examples:
2073 int i = 1;
2075 A definition, which goes in the initialized data section of the
2076 output file.
2077 extern int i;
2079 An undefined reference, which does not allocate space. There
2080 must be either a definition or a common symbol for the variable
2081 somewhere.
2082 int i;
2084 A common symbol. If there are only (one or more) common
2085 symbols for a variable, it goes in the uninitialized data area
2086 of the output file. The linker merges multiple common symbols
2087 for the same variable into a single symbol. If they are of
2088 different sizes, it picks the largest size. The linker turns a
2089 common symbol into a declaration, if there is a definition of
2090 the same variable.
2091 The --warn-common option can produce five kinds of warnings. Each
2093 warning consists of a pair of lines: the first describes the symbol
2094 just encountered, and the second describes the previous symbol
2095 encountered with the same name. One or both of the two symbols
2096 will be a common symbol.
2097 1. Turning a common symbol into a reference, because there is
2099 already a definition for the symbol.
2100 <file>(<section>): warning: common of `<symbol>'
2102 overridden by definition
2103 <file>(<section>): warning: defined here
2104 2. Turning a common symbol into a reference, because a later
2106 definition for the symbol is encountered. This is the same as
2107 the previous case, except that the symbols are encountered in a
2108 different order.
2109 <file>(<section>): warning: definition of `<symbol>'
2111 overriding common
2112 <file>(<section>): warning: common is here
2113 3. Merging a common symbol with a previous same-sized common
2115 symbol.
2116 <file>(<section>): warning: multiple common
2118 of `<symbol>'
2119 <file>(<section>): warning: previous common is here
2120 4. Merging a common symbol with a previous larger common symbol.
2122 <file>(<section>): warning: common of `<symbol>'
2124 overridden by larger common
2125 <file>(<section>): warning: larger common is here
2126 5. Merging a common symbol with a previous smaller common symbol.
2128 This is the same as the previous case, except that the symbols
2129 are encountered in a different order.
2130 <file>(<section>): warning: common of `<symbol>'
2132 overriding smaller common
2133 <file>(<section>): warning: smaller common is here
2134 --warn-constructors
2136 Warn if any global constructors are used. This is only useful for
2137 a few object file formats. For formats like COFF or ELF, the
2138 linker can not detect the use of global constructors.
2139 --warn-execstack
2141 --no-warn-execstack
2142 On ELF platforms this option controls how the linker generates
2143 warning messages when it creates an output file with an executable
2144 stack. By default the linker will not warn if the -z execstack
2145 command line option has been used, but this behaviour can be
2146 overridden by the --warn-execstack option.
2147 On the other hand the linker will normally warn if the stack is
2149 made executable because one or more of the input files need an
2150 execuable stack and neither of the -z execstack or -z noexecstack
2151 command line options have been specified. This warning can be
2152 disabled via the --no-warn-execstack option.
2153 Note: ELF format input files specify that they need an executable
2155 stack by having a .note.GNU-stack section with the executable bit
2156 set in its section flags. They can specify that they do not need
2157 an executable stack by having that section, but without the
2158 executable flag bit set. If an input file does not have a
2159 .note.GNU-stack section present then the default behaviour is
2160 target specific. For some targets, then absence of such a section
2161 implies that an executable stack is required. This is often a
2162 problem for hand crafted assembler files.
2163 --warn-multiple-gp
2165 Warn if multiple global pointer values are required in the output
2166 file. This is only meaningful for certain processors, such as the
2167 Alpha. Specifically, some processors put large-valued constants in
2168 a special section. A special register (the global pointer) points
2169 into the middle of this section, so that constants can be loaded
2170 efficiently via a base-register relative addressing mode. Since
2171 the offset in base-register relative mode is fixed and relatively
2172 small (e.g., 16 bits), this limits the maximum size of the constant
2173 pool. Thus, in large programs, it is often necessary to use
2174 multiple global pointer values in order to be able to address all
2175 possible constants. This option causes a warning to be issued
2176 whenever this case occurs.
2177 --warn-once
2179 Only warn once for each undefined symbol, rather than once per
2180 module which refers to it.
2181 --warn-rwx-segments
2183 --no-warn-rwx-segments
2184 Warn if the linker creates a loadable, non-zero sized segment that
2185 has all three of the read, write and execute permission flags set.
2186 Such a segment represents a potential security vulnerability. In
2187 addition warnings will be generated if a thread local storage
2188 segment is created with the execute permission flag set, regardless
2189 of whether or not it has the read and/or write flags set.
2190 These warnings are enabled by default. They can be disabled via
2192 the --no-warn-rwx-segments option and re-enabled via the
2193 --warn-rwx-segments option.
2194 --warn-section-align
2196 Warn if the address of an output section is changed because of
2197 alignment. Typically, the alignment will be set by an input
2198 section. The address will only be changed if it not explicitly
2199 specified; that is, if the "SECTIONS" command does not specify a
2200 start address for the section.
2201 --warn-textrel
2203 Warn if the linker adds DT_TEXTREL to a position-independent
2204 executable or shared object.
2205 --warn-alternate-em
2207 Warn if an object has alternate ELF machine code.
2208 --warn-unresolved-symbols
2210 If the linker is going to report an unresolved symbol (see the
2211 option --unresolved-symbols) it will normally generate an error.
2212 This option makes it generate a warning instead.
2213 --error-unresolved-symbols
2215 This restores the linker's default behaviour of generating errors
2216 when it is reporting unresolved symbols.
2217 --whole-archive
2219 For each archive mentioned on the command line after the
2220 --whole-archive option, include every object file in the archive in
2221 the link, rather than searching the archive for the required object
2222 files. This is normally used to turn an archive file into a shared
2223 library, forcing every object to be included in the resulting
2224 shared library. This option may be used more than once.
2225 Two notes when using this option from gcc: First, gcc doesn't know
2227 about this option, so you have to use -Wl,-whole-archive. Second,
2228 don't forget to use -Wl,-no-whole-archive after your list of
2229 archives, because gcc will add its own list of archives to your
2230 link and you may not want this flag to affect those as well.
2231 --wrap=symbol
2233 Use a wrapper function for symbol. Any undefined reference to
2234 symbol will be resolved to "__wrap_symbol". Any undefined
2235 reference to "__real_symbol" will be resolved to symbol.
2236 This can be used to provide a wrapper for a system function. The
2238 wrapper function should be called "__wrap_symbol". If it wishes to
2239 call the system function, it should call "__real_symbol".
2240 Here is a trivial example:
2242 void *
2244 __wrap_malloc (size_t c)
2245 {
2246 printf ("malloc called with %zu\n", c);
2247 return __real_malloc (c);
2248 }
2249 If you link other code with this file using --wrap malloc, then all
2251 calls to "malloc" will call the function "__wrap_malloc" instead.
2252 The call to "__real_malloc" in "__wrap_malloc" will call the real
2253 "malloc" function.
2254 You may wish to provide a "__real_malloc" function as well, so that
2256 links without the --wrap option will succeed. If you do this, you
2257 should not put the definition of "__real_malloc" in the same file
2258 as "__wrap_malloc"; if you do, the assembler may resolve the call
2259 before the linker has a chance to wrap it to "malloc".
2260 Only undefined references are replaced by the linker. So,
2262 translation unit internal references to symbol are not resolved to
2263 "__wrap_symbol". In the next example, the call to "f" in "g" is
2264 not resolved to "__wrap_f".
2265 int
2267 f (void)
2268 {
2269 return 123;
2270 }
2271 int
2273 g (void)
2274 {
2275 return f();
2276 }
2277 --eh-frame-hdr
2279 --no-eh-frame-hdr
2280 Request (--eh-frame-hdr) or suppress (--no-eh-frame-hdr) the
2281 creation of ".eh_frame_hdr" section and ELF "PT_GNU_EH_FRAME"
2282 segment header.
2283 --no-ld-generated-unwind-info
2285 Request creation of ".eh_frame" unwind info for linker generated
2286 code sections like PLT. This option is on by default if linker
2287 generated unwind info is supported. This option also controls the
2288 generation of ".sframe" stack trace info for linker generated code
2289 sections like PLT.
2290 --enable-new-dtags
2292 --disable-new-dtags
2293 This linker can create the new dynamic tags in ELF. But the older
2294 ELF systems may not understand them. If you specify
2295 --enable-new-dtags, the new dynamic tags will be created as needed
2296 and older dynamic tags will be omitted. If you specify
2297 --disable-new-dtags, no new dynamic tags will be created. By
2298 default, the new dynamic tags are not created. Note that those
2299 options are only available for ELF systems.
2300 --hash-size=number
2302 Set the default size of the linker's hash tables to a prime number
2303 close to number. Increasing this value can reduce the length of
2304 time it takes the linker to perform its tasks, at the expense of
2305 increasing the linker's memory requirements. Similarly reducing
2306 this value can reduce the memory requirements at the expense of
2307 speed.
2308 --hash-style=style
2310 Set the type of linker's hash table(s). style can be either "sysv"
2311 for classic ELF ".hash" section, "gnu" for new style GNU
2312 ".gnu.hash" section or "both" for both the classic ELF ".hash" and
2313 new style GNU ".gnu.hash" hash tables. The default depends upon
2314 how the linker was configured, but for most Linux based systems it
2315 will be "both".
2316 --compress-debug-sections=none
2318 --compress-debug-sections=zlib
2319 --compress-debug-sections=zlib-gnu
2320 --compress-debug-sections=zlib-gabi
2321 --compress-debug-sections=zstd
2322 On ELF platforms, these options control how DWARF debug sections
2323 are compressed using zlib.
2324 --compress-debug-sections=none doesn't compress DWARF debug
2326 sections. --compress-debug-sections=zlib-gnu compresses DWARF
2327 debug sections and renames them to begin with .zdebug instead of
2328 .debug. --compress-debug-sections=zlib-gabi also compresses DWARF
2329 debug sections, but rather than renaming them it sets the
2330 SHF_COMPRESSED flag in the sections' headers.
2331 The --compress-debug-sections=zlib option is an alias for
2333 --compress-debug-sections=zlib-gabi.
2334 --compress-debug-sections=zstd compresses DWARF debug sections
2336 using zstd.
2337 Note that this option overrides any compression in input debug
2339 sections, so if a binary is linked with
2340 --compress-debug-sections=none for example, then any compressed
2341 debug sections in input files will be uncompressed before they are
2342 copied into the output binary.
2343 The default compression behaviour varies depending upon the target
2345 involved and the configure options used to build the toolchain.
2346 The default can be determined by examining the output from the
2347 linker's --help option.
2348 --reduce-memory-overheads
2350 This option reduces memory requirements at ld runtime, at the
2351 expense of linking speed. This was introduced to select the old
2352 O(n^2) algorithm for link map file generation, rather than the new
2353 O(n) algorithm which uses about 40% more memory for symbol storage.
2354 Another effect of the switch is to set the default hash table size
2356 to 1021, which again saves memory at the cost of lengthening the
2357 linker's run time. This is not done however if the --hash-size
2358 switch has been used.
2359 The --reduce-memory-overheads switch may be also be used to enable
2361 other tradeoffs in future versions of the linker.
2362 --max-cache-size=size
2364 ld normally caches the relocation information and symbol tables of
2365 input files in memory with the unlimited size. This option sets
2366 the maximum cache size to size.
2367 --build-id
2369 --build-id=style
2370 Request the creation of a ".note.gnu.build-id" ELF note section or
2371 a ".buildid" COFF section. The contents of the note are unique
2372 bits identifying this linked file. style can be "uuid" to use 128
2373 random bits, "sha1" to use a 160-bit SHA1 hash on the normative
2374 parts of the output contents, "md5" to use a 128-bit MD5 hash on
2375 the normative parts of the output contents, or "0xhexstring" to use
2376 a chosen bit string specified as an even number of hexadecimal
2377 digits ("-" and ":" characters between digit pairs are ignored).
2378 If style is omitted, "sha1" is used.
2379 The "md5" and "sha1" styles produces an identifier that is always
2381 the same in an identical output file, but will be unique among all
2382 nonidentical output files. It is not intended to be compared as a
2383 checksum for the file's contents. A linked file may be changed
2384 later by other tools, but the build ID bit string identifying the
2385 original linked file does not change.
2386 Passing "none" for style disables the setting from any "--build-id"
2388 options earlier on the command line.
2389 --package-metadata=JSON
2391 Request the creation of a ".note.package" ELF note section. The
2392 contents of the note are in JSON format, as per the package
2393 metadata specification. For more information see:
2394 https://systemd.io/ELF_PACKAGE_METADATA/ If the JSON argument is
2395 missing/empty then this will disable the creation of the metadata
2396 note, if one had been enabled by an earlier occurrence of the
2397 --package-metdata option. If the linker has been built with
2398 libjansson, then the JSON string will be validated.
2399 The i386 PE linker supports the -shared option, which causes the output
2401 to be a dynamically linked library (DLL) instead of a normal
2402 executable. You should name the output "*.dll" when you use this
2403 option. In addition, the linker fully supports the standard "*.def"
2404 files, which may be specified on the linker command line like an object
2405 file (in fact, it should precede archives it exports symbols from, to
2406 ensure that they get linked in, just like a normal object file).
2407 In addition to the options common to all targets, the i386 PE linker
2409 support additional command-line options that are specific to the i386
2410 PE target. Options that take values may be separated from their values
2411 by either a space or an equals sign.
2412 --add-stdcall-alias
2414 If given, symbols with a stdcall suffix (@nn) will be exported as-
2415 is and also with the suffix stripped. [This option is specific to
2416 the i386 PE targeted port of the linker]
2417 --base-file file
2419 Use file as the name of a file in which to save the base addresses
2420 of all the relocations needed for generating DLLs with dlltool.
2421 [This is an i386 PE specific option]
2422 --dll
2424 Create a DLL instead of a regular executable. You may also use
2425 -shared or specify a "LIBRARY" in a given ".def" file. [This
2426 option is specific to the i386 PE targeted port of the linker]
2427 --enable-long-section-names
2429 --disable-long-section-names
2430 The PE variants of the COFF object format add an extension that
2431 permits the use of section names longer than eight characters, the
2432 normal limit for COFF. By default, these names are only allowed in
2433 object files, as fully-linked executable images do not carry the
2434 COFF string table required to support the longer names. As a GNU
2435 extension, it is possible to allow their use in executable images
2436 as well, or to (probably pointlessly!) disallow it in object
2437 files, by using these two options. Executable images generated
2438 with these long section names are slightly non-standard, carrying
2439 as they do a string table, and may generate confusing output when
2440 examined with non-GNU PE-aware tools, such as file viewers and
2441 dumpers. However, GDB relies on the use of PE long section names
2442 to find Dwarf-2 debug information sections in an executable image
2443 at runtime, and so if neither option is specified on the command-
2444 line, ld will enable long section names, overriding the default and
2445 technically correct behaviour, when it finds the presence of debug
2446 information while linking an executable image and not stripping
2447 symbols. [This option is valid for all PE targeted ports of the
2448 linker]
2449 --enable-stdcall-fixup
2451 --disable-stdcall-fixup
2452 If the link finds a symbol that it cannot resolve, it will attempt
2453 to do "fuzzy linking" by looking for another defined symbol that
2454 differs only in the format of the symbol name (cdecl vs stdcall)
2455 and will resolve that symbol by linking to the match. For example,
2456 the undefined symbol "_foo" might be linked to the function
2457 "_foo@12", or the undefined symbol "_bar@16" might be linked to the
2458 function "_bar". When the linker does this, it prints a warning,
2459 since it normally should have failed to link, but sometimes import
2460 libraries generated from third-party dlls may need this feature to
2461 be usable. If you specify --enable-stdcall-fixup, this feature is
2462 fully enabled and warnings are not printed. If you specify
2463 --disable-stdcall-fixup, this feature is disabled and such
2464 mismatches are considered to be errors. [This option is specific
2465 to the i386 PE targeted port of the linker]
2466 --leading-underscore
2468 --no-leading-underscore
2469 For most targets default symbol-prefix is an underscore and is
2470 defined in target's description. By this option it is possible to
2471 disable/enable the default underscore symbol-prefix.
2472 --export-all-symbols
2474 If given, all global symbols in the objects used to build a DLL
2475 will be exported by the DLL. Note that this is the default if
2476 there otherwise wouldn't be any exported symbols. When symbols are
2477 explicitly exported via DEF files or implicitly exported via
2478 function attributes, the default is to not export anything else
2479 unless this option is given. Note that the symbols "DllMain@12",
2480 "DllEntryPoint@0", "DllMainCRTStartup@12", and "impure_ptr" will
2481 not be automatically exported. Also, symbols imported from other
2482 DLLs will not be re-exported, nor will symbols specifying the DLL's
2483 internal layout such as those beginning with "_head_" or ending
2484 with "_iname". In addition, no symbols from "libgcc", "libstd++",
2485 "libmingw32", or "crtX.o" will be exported. Symbols whose names
2486 begin with "__rtti_" or "__builtin_" will not be exported, to help
2487 with C++ DLLs. Finally, there is an extensive list of cygwin-
2488 private symbols that are not exported (obviously, this applies on
2489 when building DLLs for cygwin targets). These cygwin-excludes are:
2490 "_cygwin_dll_entry@12", "_cygwin_crt0_common@8",
2491 "_cygwin_noncygwin_dll_entry@12", "_fmode", "_impure_ptr",
2492 "cygwin_attach_dll", "cygwin_premain0", "cygwin_premain1",
2493 "cygwin_premain2", "cygwin_premain3", and "environ". [This option
2494 is specific to the i386 PE targeted port of the linker]
2495 --exclude-symbols symbol,symbol,...
2497 Specifies a list of symbols which should not be automatically
2498 exported. The symbol names may be delimited by commas or colons.
2499 [This option is specific to the i386 PE targeted port of the
2500 linker]
2501 --exclude-all-symbols
2503 Specifies no symbols should be automatically exported. [This
2504 option is specific to the i386 PE targeted port of the linker]
2505 --file-alignment
2507 Specify the file alignment. Sections in the file will always begin
2508 at file offsets which are multiples of this number. This defaults
2509 to 512. [This option is specific to the i386 PE targeted port of
2510 the linker]
2511 --heap reserve
2513 --heap reserve,commit
2514 Specify the number of bytes of memory to reserve (and optionally
2515 commit) to be used as heap for this program. The default is 1MB
2516 reserved, 4K committed. [This option is specific to the i386 PE
2517 targeted port of the linker]
2518 --image-base value
2520 Use value as the base address of your program or dll. This is the
2521 lowest memory location that will be used when your program or dll
2522 is loaded. To reduce the need to relocate and improve performance
2523 of your dlls, each should have a unique base address and not
2524 overlap any other dlls. The default is 0x400000 for executables,
2525 and 0x10000000 for dlls. [This option is specific to the i386 PE
2526 targeted port of the linker]
2527 --kill-at
2529 If given, the stdcall suffixes (@nn) will be stripped from symbols
2530 before they are exported. [This option is specific to the i386 PE
2531 targeted port of the linker]
2532 --large-address-aware
2534 If given, the appropriate bit in the "Characteristics" field of the
2535 COFF header is set to indicate that this executable supports
2536 virtual addresses greater than 2 gigabytes. This should be used in
2537 conjunction with the /3GB or /USERVA=value megabytes switch in the
2538 "[operating systems]" section of the BOOT.INI. Otherwise, this bit
2539 has no effect. [This option is specific to PE targeted ports of
2540 the linker]
2541 --disable-large-address-aware
2543 Reverts the effect of a previous --large-address-aware option.
2544 This is useful if --large-address-aware is always set by the
2545 compiler driver (e.g. Cygwin gcc) and the executable does not
2546 support virtual addresses greater than 2 gigabytes. [This option
2547 is specific to PE targeted ports of the linker]
2548 --major-image-version value
2550 Sets the major number of the "image version". Defaults to 1.
2551 [This option is specific to the i386 PE targeted port of the
2552 linker]
2553 --major-os-version value
2555 Sets the major number of the "os version". Defaults to 4. [This
2556 option is specific to the i386 PE targeted port of the linker]
2557 --major-subsystem-version value
2559 Sets the major number of the "subsystem version". Defaults to 4.
2560 [This option is specific to the i386 PE targeted port of the
2561 linker]
2562 --minor-image-version value
2564 Sets the minor number of the "image version". Defaults to 0.
2565 [This option is specific to the i386 PE targeted port of the
2566 linker]
2567 --minor-os-version value
2569 Sets the minor number of the "os version". Defaults to 0. [This
2570 option is specific to the i386 PE targeted port of the linker]
2571 --minor-subsystem-version value
2573 Sets the minor number of the "subsystem version". Defaults to 0.
2574 [This option is specific to the i386 PE targeted port of the
2575 linker]
2576 --output-def file
2578 The linker will create the file file which will contain a DEF file
2579 corresponding to the DLL the linker is generating. This DEF file
2580 (which should be called "*.def") may be used to create an import
2581 library with "dlltool" or may be used as a reference to
2582 automatically or implicitly exported symbols. [This option is
2583 specific to the i386 PE targeted port of the linker]
2584 --enable-auto-image-base
2586 --enable-auto-image-base=value
2587 Automatically choose the image base for DLLs, optionally starting
2588 with base value, unless one is specified using the "--image-base"
2589 argument. By using a hash generated from the dllname to create
2590 unique image bases for each DLL, in-memory collisions and
2591 relocations which can delay program execution are avoided. [This
2592 option is specific to the i386 PE targeted port of the linker]
2593 --disable-auto-image-base
2595 Do not automatically generate a unique image base. If there is no
2596 user-specified image base ("--image-base") then use the platform
2597 default. [This option is specific to the i386 PE targeted port of
2598 the linker]
2599 --dll-search-prefix string
2601 When linking dynamically to a dll without an import library, search
2602 for "<string><basename>.dll" in preference to "lib<basename>.dll".
2603 This behaviour allows easy distinction between DLLs built for the
2604 various "subplatforms": native, cygwin, uwin, pw, etc. For
2605 instance, cygwin DLLs typically use "--dll-search-prefix=cyg".
2606 [This option is specific to the i386 PE targeted port of the
2607 linker]
2608 --enable-auto-import
2610 Do sophisticated linking of "_symbol" to "__imp__symbol" for DATA
2611 imports from DLLs, thus making it possible to bypass the dllimport
2612 mechanism on the user side and to reference unmangled symbol names.
2613 [This option is specific to the i386 PE targeted port of the
2614 linker]
2615 The following remarks pertain to the original implementation of the
2617 feature and are obsolete nowadays for Cygwin and MinGW targets.
2618 Note: Use of the 'auto-import' extension will cause the text
2620 section of the image file to be made writable. This does not
2621 conform to the PE-COFF format specification published by Microsoft.
2622 Note - use of the 'auto-import' extension will also cause read only
2624 data which would normally be placed into the .rdata section to be
2625 placed into the .data section instead. This is in order to work
2626 around a problem with consts that is described here:
2627 http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
2628 Using 'auto-import' generally will 'just work' -- but sometimes you
2630 may see this message:
2631 "variable '<var>' can't be auto-imported. Please read the
2633 documentation for ld's "--enable-auto-import" for details."
2634 This message occurs when some (sub)expression accesses an address
2636 ultimately given by the sum of two constants (Win32 import tables
2637 only allow one). Instances where this may occur include accesses
2638 to member fields of struct variables imported from a DLL, as well
2639 as using a constant index into an array variable imported from a
2640 DLL. Any multiword variable (arrays, structs, long long, etc) may
2641 trigger this error condition. However, regardless of the exact
2642 data type of the offending exported variable, ld will always detect
2643 it, issue the warning, and exit.
2644 There are several ways to address this difficulty, regardless of
2646 the data type of the exported variable:
2647 One way is to use --enable-runtime-pseudo-reloc switch. This leaves
2649 the task of adjusting references in your client code for runtime
2650 environment, so this method works only when runtime environment
2651 supports this feature.
2652 A second solution is to force one of the 'constants' to be a
2654 variable -- that is, unknown and un-optimizable at compile time.
2655 For arrays, there are two possibilities: a) make the indexee (the
2656 array's address) a variable, or b) make the 'constant' index a
2657 variable. Thus:
2658 extern type extern_array[];
2660 extern_array[1] -->
2661 { volatile type *t=extern_array; t[1] }
2662 or
2664 extern type extern_array[];
2666 extern_array[1] -->
2667 { volatile int t=1; extern_array[t] }
2668 For structs (and most other multiword data types) the only option
2670 is to make the struct itself (or the long long, or the ...)
2671 variable:
2672 extern struct s extern_struct;
2674 extern_struct.field -->
2675 { volatile struct s *t=&extern_struct; t->field }
2676 or
2678 extern long long extern_ll;
2680 extern_ll -->
2681 { volatile long long * local_ll=&extern_ll; *local_ll }
2682 A third method of dealing with this difficulty is to abandon
2684 'auto-import' for the offending symbol and mark it with
2685 "__declspec(dllimport)". However, in practice that requires using
2686 compile-time #defines to indicate whether you are building a DLL,
2687 building client code that will link to the DLL, or merely
2688 building/linking to a static library. In making the choice
2689 between the various methods of resolving the 'direct address with
2690 constant offset' problem, you should consider typical real-world
2691 usage:
2692 Original:
2694 --foo.h
2696 extern int arr[];
2697 --foo.c
2698 #include "foo.h"
2699 void main(int argc, char **argv){
2700 printf("%d\n",arr[1]);
2701 }
2702 Solution 1:
2704 --foo.h
2706 extern int arr[];
2707 --foo.c
2708 #include "foo.h"
2709 void main(int argc, char **argv){
2710 /* This workaround is for win32 and cygwin; do not "optimize" */
2711 volatile int *parr = arr;
2712 printf("%d\n",parr[1]);
2713 }
2714 Solution 2:
2716 --foo.h
2718 /* Note: auto-export is assumed (no __declspec(dllexport)) */
2719 #if (defined(_WIN32) || defined(__CYGWIN__)) && \
2720 !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
2721 #define FOO_IMPORT __declspec(dllimport)
2722 #else
2723 #define FOO_IMPORT
2724 #endif
2725 extern FOO_IMPORT int arr[];
2726 --foo.c
2727 #include "foo.h"
2728 void main(int argc, char **argv){
2729 printf("%d\n",arr[1]);
2730 }
2731 A fourth way to avoid this problem is to re-code your library to
2733 use a functional interface rather than a data interface for the
2734 offending variables (e.g. set_foo() and get_foo() accessor
2735 functions).
2736 --disable-auto-import
2738 Do not attempt to do sophisticated linking of "_symbol" to
2739 "__imp__symbol" for DATA imports from DLLs. [This option is
2740 specific to the i386 PE targeted port of the linker]
2741 --enable-runtime-pseudo-reloc
2743 If your code contains expressions described in --enable-auto-import
2744 section, that is, DATA imports from DLL with non-zero offset, this
2745 switch will create a vector of 'runtime pseudo relocations' which
2746 can be used by runtime environment to adjust references to such
2747 data in your client code. [This option is specific to the i386 PE
2748 targeted port of the linker]
2749 --disable-runtime-pseudo-reloc
2751 Do not create pseudo relocations for non-zero offset DATA imports
2752 from DLLs. [This option is specific to the i386 PE targeted port
2753 of the linker]
2754 --enable-extra-pe-debug
2756 Show additional debug info related to auto-import symbol thunking.
2757 [This option is specific to the i386 PE targeted port of the
2758 linker]
2759 --section-alignment
2761 Sets the section alignment. Sections in memory will always begin
2762 at addresses which are a multiple of this number. Defaults to
2763 0x1000. [This option is specific to the i386 PE targeted port of
2764 the linker]
2765 --stack reserve
2767 --stack reserve,commit
2768 Specify the number of bytes of memory to reserve (and optionally
2769 commit) to be used as stack for this program. The default is 2MB
2770 reserved, 4K committed. [This option is specific to the i386 PE
2771 targeted port of the linker]
2772 --subsystem which
2774 --subsystem which:major
2775 --subsystem which:major.minor
2776 Specifies the subsystem under which your program will execute. The
2777 legal values for which are "native", "windows", "console", "posix",
2778 and "xbox". You may optionally set the subsystem version also.
2779 Numeric values are also accepted for which. [This option is
2780 specific to the i386 PE targeted port of the linker]
2781 The following options set flags in the "DllCharacteristics" field
2783 of the PE file header: [These options are specific to PE targeted
2784 ports of the linker]
2785 --high-entropy-va
2787 --disable-high-entropy-va
2788 Image is compatible with 64-bit address space layout randomization
2789 (ASLR). This option is enabled by default for 64-bit PE images.
2790 This option also implies --dynamicbase and --enable-reloc-section.
2792 --dynamicbase
2794 --disable-dynamicbase
2795 The image base address may be relocated using address space layout
2796 randomization (ASLR). This feature was introduced with MS Windows
2797 Vista for i386 PE targets. This option is enabled by default but
2798 can be disabled via the --disable-dynamicbase option. This option
2799 also implies --enable-reloc-section.
2800 --forceinteg
2802 --disable-forceinteg
2803 Code integrity checks are enforced. This option is disabled by
2804 default.
2805 --nxcompat
2807 --disable-nxcompat
2808 The image is compatible with the Data Execution Prevention. This
2809 feature was introduced with MS Windows XP SP2 for i386 PE targets.
2810 The option is enabled by default.
2811 --no-isolation
2813 --disable-no-isolation
2814 Although the image understands isolation, do not isolate the image.
2815 This option is disabled by default.
2816 --no-seh
2818 --disable-no-seh
2819 The image does not use SEH. No SE handler may be called from this
2820 image. This option is disabled by default.
2821 --no-bind
2823 --disable-no-bind
2824 Do not bind this image. This option is disabled by default.
2825 --wdmdriver
2827 --disable-wdmdriver
2828 The driver uses the MS Windows Driver Model. This option is
2829 disabled by default.
2830 --tsaware
2832 --disable-tsaware
2833 The image is Terminal Server aware. This option is disabled by
2834 default.
2835 --insert-timestamp
2837 --no-insert-timestamp
2838 Insert a real timestamp into the image. This is the default
2839 behaviour as it matches legacy code and it means that the image
2840 will work with other, proprietary tools. The problem with this
2841 default is that it will result in slightly different images being
2842 produced each time the same sources are linked. The option
2843 --no-insert-timestamp can be used to insert a zero value for the
2844 timestamp, this ensuring that binaries produced from identical
2845 sources will compare identically.
2846 --enable-reloc-section
2848 --disable-reloc-section
2849 Create the base relocation table, which is necessary if the image
2850 is loaded at a different image base than specified in the PE
2851 header. This option is enabled by default.
2852 The C6X uClinux target uses a binary format called DSBT to support
2854 shared libraries. Each shared library in the system needs to have a
2855 unique index; all executables use an index of 0.
2856 --dsbt-size size
2858 This option sets the number of entries in the DSBT of the current
2859 executable or shared library to size. The default is to create a
2860 table with 64 entries.
2861 --dsbt-index index
2863 This option sets the DSBT index of the current executable or shared
2864 library to index. The default is 0, which is appropriate for
2865 generating executables. If a shared library is generated with a
2866 DSBT index of 0, the "R_C6000_DSBT_INDEX" relocs are copied into
2867 the output file.
2868 The --no-merge-exidx-entries switch disables the merging of
2870 adjacent exidx entries in frame unwind info.
2871 --branch-stub
2873 This option enables linker branch relaxation by inserting branch
2874 stub sections when needed to extend the range of branches. This
2875 option is usually not required since C-SKY supports branch and call
2876 instructions that can access the full memory range and branch
2877 relaxation is normally handled by the compiler or assembler.
2878 --stub-group-size=N
2880 This option allows finer control of linker branch stub creation.
2881 It sets the maximum size of a group of input sections that can be
2882 handled by one stub section. A negative value of N locates stub
2883 sections after their branches, while a positive value allows stub
2884 sections to appear either before or after the branches. Values of
2885 1 or -1 indicate that the linker should choose suitable defaults.
2886 The 68HC11 and 68HC12 linkers support specific options to control the
2888 memory bank switching mapping and trampoline code generation.
2889 --no-trampoline
2891 This option disables the generation of trampoline. By default a
2892 trampoline is generated for each far function which is called using
2893 a "jsr" instruction (this happens when a pointer to a far function
2894 is taken).
2895 --bank-window name
2897 This option indicates to the linker the name of the memory region
2898 in the MEMORY specification that describes the memory bank window.
2899 The definition of such region is then used by the linker to compute
2900 paging and addresses within the memory window.
2901 The following options are supported to control handling of GOT
2903 generation when linking for 68K targets.
2904 --got=type
2906 This option tells the linker which GOT generation scheme to use.
2907 type should be one of single, negative, multigot or target. For
2908 more information refer to the Info entry for ld.
2909 The following options are supported to control microMIPS instruction
2911 generation and branch relocation checks for ISA mode transitions when
2912 linking for MIPS targets.
2913 --insn32
2915 --no-insn32
2916 These options control the choice of microMIPS instructions used in
2917 code generated by the linker, such as that in the PLT or lazy
2918 binding stubs, or in relaxation. If --insn32 is used, then the
2919 linker only uses 32-bit instruction encodings. By default or if
2920 --no-insn32 is used, all instruction encodings are used, including
2921 16-bit ones where possible.
2922 --ignore-branch-isa
2924 --no-ignore-branch-isa
2925 These options control branch relocation checks for invalid ISA mode
2926 transitions. If --ignore-branch-isa is used, then the linker
2927 accepts any branch relocations and any ISA mode transition required
2928 is lost in relocation calculation, except for some cases of "BAL"
2929 instructions which meet relaxation conditions and are converted to
2930 equivalent "JALX" instructions as the associated relocation is
2931 calculated. By default or if --no-ignore-branch-isa is used a
2932 check is made causing the loss of an ISA mode transition to produce
2933 an error.
2934 --compact-branches
2936 --no-compact-branches
2937 These options control the generation of compact instructions by the
2938 linker in the PLT entries for MIPS R6.
2939 For the pdp11-aout target, three variants of the output format can be
2941 produced as selected by the following options. The default variant for
2942 pdp11-aout is the --omagic option, whereas for other targets --nmagic
2943 is the default. The --imagic option is defined only for the pdp11-aout
2944 target, while the others are described here as they apply to the
2945 pdp11-aout target.
2946 -N
2948 --omagic
2949 Mark the output as "OMAGIC" (0407) in the a.out header to indicate
2950 that the text segment is not to be write-protected and shared.
2951 Since the text and data sections are both readable and writable,
2952 the data section is allocated immediately contiguous after the text
2953 segment. This is the oldest format for PDP11 executable programs
2954 and is the default for ld on PDP11 Unix systems from the beginning
2955 through 2.11BSD.
2956 -n
2958 --nmagic
2959 Mark the output as "NMAGIC" (0410) in the a.out header to indicate
2960 that when the output file is executed, the text portion will be
2961 read-only and shareable among all processes executing the same
2962 file. This involves moving the data areas up to the first possible
2963 8K byte page boundary following the end of the text. This option
2964 creates a pure executable format.
2965 -z
2967 --imagic
2968 Mark the output as "IMAGIC" (0411) in the a.out header to indicate
2969 that when the output file is executed, the program text and data
2970 areas will be loaded into separate address spaces using the split
2971 instruction and data space feature of the memory management unit in
2972 larger models of the PDP11. This doubles the address space
2973 available to the program. The text segment is again pure, write-
2974 protected, and shareable. The only difference in the output format
2975 between this option and the others, besides the magic number, is
2976 that both the text and data sections start at location 0. The -z
2977 option selected this format in 2.11BSD. This option creates a
2978 separate executable format.
2979 --no-omagic
2981 Equivalent to --nmagic for pdp11-aout.
2982
2984 You can change the behaviour of ld with the environment variables
2985 "GNUTARGET", "LDEMULATION" and "COLLECT_NO_DEMANGLE".
2986 "GNUTARGET" determines the input-file object format if you don't use -b
2988 (or its synonym --format). Its value should be one of the BFD names
2989 for an input format. If there is no "GNUTARGET" in the environment, ld
2990 uses the natural format of the target. If "GNUTARGET" is set to
2991 "default" then BFD attempts to discover the input format by examining
2992 binary input files; this method often succeeds, but there are potential
2993 ambiguities, since there is no method of ensuring that the magic number
2994 used to specify object-file formats is unique. However, the
2995 configuration procedure for BFD on each system places the conventional
2996 format for that system first in the search-list, so ambiguities are
2997 resolved in favor of convention.
2998 "LDEMULATION" determines the default emulation if you don't use the -m
3000 option. The emulation can affect various aspects of linker behaviour,
3001 particularly the default linker script. You can list the available
3002 emulations with the --verbose or -V options. If the -m option is not
3003 used, and the "LDEMULATION" environment variable is not defined, the
3004 default emulation depends upon how the linker was configured.
3005 Normally, the linker will default to demangling symbols. However, if
3007 "COLLECT_NO_DEMANGLE" is set in the environment, then it will default
3008 to not demangling symbols. This environment variable is used in a
3009 similar fashion by the "gcc" linker wrapper program. The default may
3010 be overridden by the --demangle and --no-demangle options.
3011
3013 ar(1), nm(1), objcopy(1), objdump(1), readelf(1) and the Info entries
3014 for binutils and ld.
3015
3017 Copyright (c) 1991-2023 Free Software Foundation, Inc.
3018 Permission is granted to copy, distribute and/or modify this document
3020 under the terms of the GNU Free Documentation License, Version 1.3 or
3021 any later version published by the Free Software Foundation; with no
3022 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
3023 Texts. A copy of the license is included in the section entitled "GNU
3024 Free Documentation License".
3025binutils-2.41 2023-07-30 LD(1)