1LD(1) GNU Development Tools LD(1)
2
6 ld - The GNU linker
7
9 ld [options] objfile ...
10
12 ld combines a number of object and archive files, relocates their data
13 and ties up symbol references. Usually the last step in compiling a
14 program is to run ld.
15 ld accepts Linker Command Language files written in a superset of
17 AT&T's Link Editor Command Language syntax, to provide explicit and
18 total control over the linking process.
19 This man page does not describe the command language; see the ld entry
21 in "info" for full details on the command language and on other aspects
22 of the GNU linker.
23 This version of ld uses the general purpose BFD libraries to operate on
25 object files. This allows ld to read, combine, and write object files
26 in many different formats---for example, COFF or "a.out". Different
27 formats may be linked together to produce any available kind of object
28 file.
29 Aside from its flexibility, the GNU linker is more helpful than other
31 linkers in providing diagnostic information. Many linkers abandon
32 execution immediately upon encountering an error; whenever possible, ld
33 continues executing, allowing you to identify other errors (or, in some
34 cases, to get an output file in spite of the error).
35 The GNU linker ld is meant to cover a broad range of situations, and to
37 be as compatible as possible with other linkers. As a result, you have
38 many choices to control its behavior.
39
41 The linker supports a plethora of command-line options, but in actual
42 practice few of them are used in any particular context. For instance,
43 a frequent use of ld is to link standard Unix object files on a
44 standard, supported Unix system. On such a system, to link a file
45 "hello.o":
46 ld -o <output> /lib/crt0.o hello.o -lc
48 This tells ld to produce a file called output as the result of linking
50 the file "/lib/crt0.o" with "hello.o" and the library "libc.a", which
51 will come from the standard search directories. (See the discussion of
52 the -l option below.)
53 Some of the command-line options to ld may be specified at any point in
55 the command line. However, options which refer to files, such as -l or
56 -T, cause the file to be read at the point at which the option appears
57 in the command line, relative to the object files and other file
58 options. Repeating non-file options with a different argument will
59 either have no further effect, or override prior occurrences (those
60 further to the left on the command line) of that option. Options which
61 may be meaningfully specified more than once are noted in the
62 descriptions below.
63 Non-option arguments are object files or archives which are to be
65 linked together. They may follow, precede, or be mixed in with
66 command-line options, except that an object file argument may not be
67 placed between an option and its argument.
68 Usually the linker is invoked with at least one object file, but you
70 can specify other forms of binary input files using -l, -R, and the
71 script command language. If no binary input files at all are
72 specified, the linker does not produce any output, and issues the
73 message No input files.
74 If the linker cannot recognize the format of an object file, it will
76 assume that it is a linker script. A script specified in this way
77 augments the main linker script used for the link (either the default
78 linker script or the one specified by using -T). This feature permits
79 the linker to link against a file which appears to be an object or an
80 archive, but actually merely defines some symbol values, or uses
81 "INPUT" or "GROUP" to load other objects. Specifying a script in this
82 way merely augments the main linker script, with the extra commands
83 placed after the main script; use the -T option to replace the default
84 linker script entirely, but note the effect of the "INSERT" command.
85 For options whose names are a single letter, option arguments must
87 either follow the option letter without intervening whitespace, or be
88 given as separate arguments immediately following the option that
89 requires them.
90 For options whose names are multiple letters, either one dash or two
92 can precede the option name; for example, -trace-symbol and
93 --trace-symbol are equivalent. Note---there is one exception to this
94 rule. Multiple letter options that start with a lower case 'o' can
95 only be preceded by two dashes. This is to reduce confusion with the
96 -o option. So for example -omagic sets the output file name to magic
97 whereas --omagic sets the NMAGIC flag on the output.
98 Arguments to multiple-letter options must either be separated from the
100 option name by an equals sign, or be given as separate arguments
101 immediately following the option that requires them. For example,
102 --trace-symbol foo and --trace-symbol=foo are equivalent. Unique
103 abbreviations of the names of multiple-letter options are accepted.
104 Note---if the linker is being invoked indirectly, via a compiler driver
106 (e.g. gcc) then all the linker command-line options should be prefixed
107 by -Wl, (or whatever is appropriate for the particular compiler driver)
108 like this:
109 gcc -Wl,--start-group foo.o bar.o -Wl,--end-group
111 This is important, because otherwise the compiler driver program may
113 silently drop the linker options, resulting in a bad link. Confusion
114 may also arise when passing options that require values through a
115 driver, as the use of a space between option and argument acts as a
116 separator, and causes the driver to pass only the option to the linker
117 and the argument to the compiler. In this case, it is simplest to use
118 the joined forms of both single- and multiple-letter options, such as:
119 gcc foo.o bar.o -Wl,-eENTRY -Wl,-Map=a.map
121 Here is a table of the generic command-line switches accepted by the
123 GNU linker:
124 @file
126 Read command-line options from file. The options read are inserted
127 in place of the original @file option. If file does not exist, or
128 cannot be read, then the option will be treated literally, and not
129 removed.
130 Options in file are separated by whitespace. A whitespace
132 character may be included in an option by surrounding the entire
133 option in either single or double quotes. Any character (including
134 a backslash) may be included by prefixing the character to be
135 included with a backslash. The file may itself contain additional
136 @file options; any such options will be processed recursively.
137 -a keyword
139 This option is supported for HP/UX compatibility. The keyword
140 argument must be one of the strings archive, shared, or default.
141 -aarchive is functionally equivalent to -Bstatic, and the other two
142 keywords are functionally equivalent to -Bdynamic. This option may
143 be used any number of times.
144 --audit AUDITLIB
146 Adds AUDITLIB to the "DT_AUDIT" entry of the dynamic section.
147 AUDITLIB is not checked for existence, nor will it use the
148 DT_SONAME specified in the library. If specified multiple times
149 "DT_AUDIT" will contain a colon separated list of audit interfaces
150 to use. If the linker finds an object with an audit entry while
151 searching for shared libraries, it will add a corresponding
152 "DT_DEPAUDIT" entry in the output file. This option is only
153 meaningful on ELF platforms supporting the rtld-audit interface.
154 -b input-format
156 --format=input-format
157 ld may be configured to support more than one kind of object file.
158 If your ld is configured this way, you can use the -b option to
159 specify the binary format for input object files that follow this
160 option on the command line. Even when ld is configured to support
161 alternative object formats, you don't usually need to specify this,
162 as ld should be configured to expect as a default input format the
163 most usual format on each machine. input-format is a text string,
164 the name of a particular format supported by the BFD libraries.
165 (You can list the available binary formats with objdump -i.)
166 You may want to use this option if you are linking files with an
168 unusual binary format. You can also use -b to switch formats
169 explicitly (when linking object files of different formats), by
170 including -b input-format before each group of object files in a
171 particular format.
172 The default format is taken from the environment variable
174 "GNUTARGET".
175 You can also define the input format from a script, using the
177 command "TARGET";
178 -c MRI-commandfile
180 --mri-script=MRI-commandfile
181 For compatibility with linkers produced by MRI, ld accepts script
182 files written in an alternate, restricted command language,
183 described in the MRI Compatible Script Files section of GNU ld
184 documentation. Introduce MRI script files with the option -c; use
185 the -T option to run linker scripts written in the general-purpose
186 ld scripting language. If MRI-cmdfile does not exist, ld looks for
187 it in the directories specified by any -L options.
188 -d
190 -dc
191 -dp These three options are equivalent; multiple forms are supported
192 for compatibility with other linkers. They assign space to common
193 symbols even if a relocatable output file is specified (with -r).
194 The script command "FORCE_COMMON_ALLOCATION" has the same effect.
195 --depaudit AUDITLIB
197 -P AUDITLIB
198 Adds AUDITLIB to the "DT_DEPAUDIT" entry of the dynamic section.
199 AUDITLIB is not checked for existence, nor will it use the
200 DT_SONAME specified in the library. If specified multiple times
201 "DT_DEPAUDIT" will contain a colon separated list of audit
202 interfaces to use. This option is only meaningful on ELF platforms
203 supporting the rtld-audit interface. The -P option is provided for
204 Solaris compatibility.
205 -e entry
207 --entry=entry
208 Use entry as the explicit symbol for beginning execution of your
209 program, rather than the default entry point. If there is no
210 symbol named entry, the linker will try to parse entry as a number,
211 and use that as the entry address (the number will be interpreted
212 in base 10; you may use a leading 0x for base 16, or a leading 0
213 for base 8).
214 --exclude-libs lib,lib,...
216 Specifies a list of archive libraries from which symbols should not
217 be automatically exported. The library names may be delimited by
218 commas or colons. Specifying "--exclude-libs ALL" excludes symbols
219 in all archive libraries from automatic export. This option is
220 available only for the i386 PE targeted port of the linker and for
221 ELF targeted ports. For i386 PE, symbols explicitly listed in a
222 .def file are still exported, regardless of this option. For ELF
223 targeted ports, symbols affected by this option will be treated as
224 hidden.
225 --exclude-modules-for-implib module,module,...
227 Specifies a list of object files or archive members, from which
228 symbols should not be automatically exported, but which should be
229 copied wholesale into the import library being generated during the
230 link. The module names may be delimited by commas or colons, and
231 must match exactly the filenames used by ld to open the files; for
232 archive members, this is simply the member name, but for object
233 files the name listed must include and match precisely any path
234 used to specify the input file on the linker's command-line. This
235 option is available only for the i386 PE targeted port of the
236 linker. Symbols explicitly listed in a .def file are still
237 exported, regardless of this option.
238 -E
240 --export-dynamic
241 --no-export-dynamic
242 When creating a dynamically linked executable, using the -E option
243 or the --export-dynamic option causes the linker to add all symbols
244 to the dynamic symbol table. The dynamic symbol table is the set
245 of symbols which are visible from dynamic objects at run time.
246 If you do not use either of these options (or use the
248 --no-export-dynamic option to restore the default behavior), the
249 dynamic symbol table will normally contain only those symbols which
250 are referenced by some dynamic object mentioned in the link.
251 If you use "dlopen" to load a dynamic object which needs to refer
253 back to the symbols defined by the program, rather than some other
254 dynamic object, then you will probably need to use this option when
255 linking the program itself.
256 You can also use the dynamic list to control what symbols should be
258 added to the dynamic symbol table if the output format supports it.
259 See the description of --dynamic-list.
260 Note that this option is specific to ELF targeted ports. PE
262 targets support a similar function to export all symbols from a DLL
263 or EXE; see the description of --export-all-symbols below.
264 -EB Link big-endian objects. This affects the default output format.
266 -EL Link little-endian objects. This affects the default output
268 format.
269 -f name
271 --auxiliary=name
272 When creating an ELF shared object, set the internal DT_AUXILIARY
273 field to the specified name. This tells the dynamic linker that
274 the symbol table of the shared object should be used as an
275 auxiliary filter on the symbol table of the shared object name.
276 If you later link a program against this filter object, then, when
278 you run the program, the dynamic linker will see the DT_AUXILIARY
279 field. If the dynamic linker resolves any symbols from the filter
280 object, it will first check whether there is a definition in the
281 shared object name. If there is one, it will be used instead of
282 the definition in the filter object. The shared object name need
283 not exist. Thus the shared object name may be used to provide an
284 alternative implementation of certain functions, perhaps for
285 debugging or for machine specific performance.
286 This option may be specified more than once. The DT_AUXILIARY
288 entries will be created in the order in which they appear on the
289 command line.
290 -F name
292 --filter=name
293 When creating an ELF shared object, set the internal DT_FILTER
294 field to the specified name. This tells the dynamic linker that
295 the symbol table of the shared object which is being created should
296 be used as a filter on the symbol table of the shared object name.
297 If you later link a program against this filter object, then, when
299 you run the program, the dynamic linker will see the DT_FILTER
300 field. The dynamic linker will resolve symbols according to the
301 symbol table of the filter object as usual, but it will actually
302 link to the definitions found in the shared object name. Thus the
303 filter object can be used to select a subset of the symbols
304 provided by the object name.
305 Some older linkers used the -F option throughout a compilation
307 toolchain for specifying object-file format for both input and
308 output object files. The GNU linker uses other mechanisms for this
309 purpose: the -b, --format, --oformat options, the "TARGET" command
310 in linker scripts, and the "GNUTARGET" environment variable. The
311 GNU linker will ignore the -F option when not creating an ELF
312 shared object.
313 -fini=name
315 When creating an ELF executable or shared object, call NAME when
316 the executable or shared object is unloaded, by setting DT_FINI to
317 the address of the function. By default, the linker uses "_fini"
318 as the function to call.
319 -g Ignored. Provided for compatibility with other tools.
321 -G value
323 --gpsize=value
324 Set the maximum size of objects to be optimized using the GP
325 register to size. This is only meaningful for object file formats
326 such as MIPS ELF that support putting large and small objects into
327 different sections. This is ignored for other object file formats.
328 -h name
330 -soname=name
331 When creating an ELF shared object, set the internal DT_SONAME
332 field to the specified name. When an executable is linked with a
333 shared object which has a DT_SONAME field, then when the executable
334 is run the dynamic linker will attempt to load the shared object
335 specified by the DT_SONAME field rather than the using the file
336 name given to the linker.
337 -i Perform an incremental link (same as option -r).
339 -init=name
341 When creating an ELF executable or shared object, call NAME when
342 the executable or shared object is loaded, by setting DT_INIT to
343 the address of the function. By default, the linker uses "_init"
344 as the function to call.
345 -l namespec
347 --library=namespec
348 Add the archive or object file specified by namespec to the list of
349 files to link. This option may be used any number of times. If
350 namespec is of the form :filename, ld will search the library path
351 for a file called filename, otherwise it will search the library
352 path for a file called libnamespec.a.
353 On systems which support shared libraries, ld may also search for
355 files other than libnamespec.a. Specifically, on ELF and SunOS
356 systems, ld will search a directory for a library called
357 libnamespec.so before searching for one called libnamespec.a. (By
358 convention, a ".so" extension indicates a shared library.) Note
359 that this behavior does not apply to :filename, which always
360 specifies a file called filename.
361 The linker will search an archive only once, at the location where
363 it is specified on the command line. If the archive defines a
364 symbol which was undefined in some object which appeared before the
365 archive on the command line, the linker will include the
366 appropriate file(s) from the archive. However, an undefined symbol
367 in an object appearing later on the command line will not cause the
368 linker to search the archive again.
369 See the -( option for a way to force the linker to search archives
371 multiple times.
372 You may list the same archive multiple times on the command line.
374 This type of archive searching is standard for Unix linkers.
376 However, if you are using ld on AIX, note that it is different from
377 the behaviour of the AIX linker.
378 -L searchdir
380 --library-path=searchdir
381 Add path searchdir to the list of paths that ld will search for
382 archive libraries and ld control scripts. You may use this option
383 any number of times. The directories are searched in the order in
384 which they are specified on the command line. Directories
385 specified on the command line are searched before the default
386 directories. All -L options apply to all -l options, regardless of
387 the order in which the options appear. -L options do not affect
388 how ld searches for a linker script unless -T option is specified.
389 If searchdir begins with "=" or $SYSROOT, then this prefix will be
391 replaced by the sysroot prefix, controlled by the --sysroot option,
392 or specified when the linker is configured.
393 The default set of paths searched (without being specified with -L)
395 depends on which emulation mode ld is using, and in some cases also
396 on how it was configured.
397 The paths can also be specified in a link script with the
399 "SEARCH_DIR" command. Directories specified this way are searched
400 at the point in which the linker script appears in the command
401 line.
402 -m emulation
404 Emulate the emulation linker. You can list the available
405 emulations with the --verbose or -V options.
406 If the -m option is not used, the emulation is taken from the
408 "LDEMULATION" environment variable, if that is defined.
409 Otherwise, the default emulation depends upon how the linker was
411 configured.
412 -M
414 --print-map
415 Print a link map to the standard output. A link map provides
416 information about the link, including the following:
417 · Where object files are mapped into memory.
419 · How common symbols are allocated.
421 · All archive members included in the link, with a mention of the
423 symbol which caused the archive member to be brought in.
424 · The values assigned to symbols.
426 Note - symbols whose values are computed by an expression which
428 involves a reference to a previous value of the same symbol may
429 not have correct result displayed in the link map. This is
430 because the linker discards intermediate results and only
431 retains the final value of an expression. Under such
432 circumstances the linker will display the final value enclosed
433 by square brackets. Thus for example a linker script
434 containing:
435 foo = 1
437 foo = foo * 4
438 foo = foo + 8
439 will produce the following output in the link map if the -M
441 option is used:
442 0x00000001 foo = 0x1
444 [0x0000000c] foo = (foo * 0x4)
445 [0x0000000c] foo = (foo + 0x8)
446 See Expressions for more information about expressions in
448 linker scripts.
449 · *<How GNU properties are merged.>
451 When linker merges input .note.gnu.property sections into one
453 output .note.gnu.property section, some properties are removed
454 or updated, which are reported in the link map as
455 Removed property 0xc0000002 to merge foo.o (0x1) and bar.o (not found)
457 It indicates that property 0xc0000002 is removed from output
459 when merging properties in foo.o, whose property 0xc0000002
460 value is 0x1, and bar.o, which doesn't have property
461 0xc0000002.
462 Updated property 0xc0000002 (0x1) to merge foo.o (0x1) and bar.o (0x1)
464 It indicates that property 0xc0010001 value is updated to 0x1
466 in output when merging properties in foo.o, whose 0xc0010001
467 property value is 0x1, and bar.o, whose 0xc0010001 property
468 value is 0x1.
469 -n
471 --nmagic
472 Turn off page alignment of sections, and disable linking against
473 shared libraries. If the output format supports Unix style magic
474 numbers, mark the output as "NMAGIC".
475 -N
477 --omagic
478 Set the text and data sections to be readable and writable. Also,
479 do not page-align the data segment, and disable linking against
480 shared libraries. If the output format supports Unix style magic
481 numbers, mark the output as "OMAGIC". Note: Although a writable
482 text section is allowed for PE-COFF targets, it does not conform to
483 the format specification published by Microsoft.
484 --no-omagic
486 This option negates most of the effects of the -N option. It sets
487 the text section to be read-only, and forces the data segment to be
488 page-aligned. Note - this option does not enable linking against
489 shared libraries. Use -Bdynamic for this.
490 -o output
492 --output=output
493 Use output as the name for the program produced by ld; if this
494 option is not specified, the name a.out is used by default. The
495 script command "OUTPUT" can also specify the output file name.
496 -O level
498 If level is a numeric values greater than zero ld optimizes the
499 output. This might take significantly longer and therefore
500 probably should only be enabled for the final binary. At the
501 moment this option only affects ELF shared library generation.
502 Future releases of the linker may make more use of this option.
503 Also currently there is no difference in the linker's behaviour for
504 different non-zero values of this option. Again this may change
505 with future releases.
506 -plugin name
508 Involve a plugin in the linking process. The name parameter is the
509 absolute filename of the plugin. Usually this parameter is
510 automatically added by the complier, when using link time
511 optimization, but users can also add their own plugins if they so
512 wish.
513 Note that the location of the compiler originated plugins is
515 different from the place where the ar, nm and ranlib programs
516 search for their plugins. In order for those commands to make use
517 of a compiler based plugin it must first be copied into the
518 ${libdir}/bfd-plugins directory. All gcc based linker plugins are
519 backward compatible, so it is sufficient to just copy in the newest
520 one.
521 --push-state
523 The --push-state allows to preserve the current state of the flags
524 which govern the input file handling so that they can all be
525 restored with one corresponding --pop-state option.
526 The option which are covered are: -Bdynamic, -Bstatic, -dn, -dy,
528 -call_shared, -non_shared, -static, -N, -n, --whole-archive,
529 --no-whole-archive, -r, -Ur, --copy-dt-needed-entries,
530 --no-copy-dt-needed-entries, --as-needed, --no-as-needed, and -a.
531 One target for this option are specifications for pkg-config. When
533 used with the --libs option all possibly needed libraries are
534 listed and then possibly linked with all the time. It is better to
535 return something as follows:
536 -Wl,--push-state,--as-needed -libone -libtwo -Wl,--pop-state
538 --pop-state
540 Undoes the effect of --push-state, restores the previous values of
541 the flags governing input file handling.
542 -q
544 --emit-relocs
545 Leave relocation sections and contents in fully linked executables.
546 Post link analysis and optimization tools may need this information
547 in order to perform correct modifications of executables. This
548 results in larger executables.
549 This option is currently only supported on ELF platforms.
551 --force-dynamic
553 Force the output file to have dynamic sections. This option is
554 specific to VxWorks targets.
555 -r
557 --relocatable
558 Generate relocatable output---i.e., generate an output file that
559 can in turn serve as input to ld. This is often called partial
560 linking. As a side effect, in environments that support standard
561 Unix magic numbers, this option also sets the output file's magic
562 number to "OMAGIC". If this option is not specified, an absolute
563 file is produced. When linking C++ programs, this option will not
564 resolve references to constructors; to do that, use -Ur.
565 When an input file does not have the same format as the output
567 file, partial linking is only supported if that input file does not
568 contain any relocations. Different output formats can have further
569 restrictions; for example some "a.out"-based formats do not support
570 partial linking with input files in other formats at all.
571 This option does the same thing as -i.
573 -R filename
575 --just-symbols=filename
576 Read symbol names and their addresses from filename, but do not
577 relocate it or include it in the output. This allows your output
578 file to refer symbolically to absolute locations of memory defined
579 in other programs. You may use this option more than once.
580 For compatibility with other ELF linkers, if the -R option is
582 followed by a directory name, rather than a file name, it is
583 treated as the -rpath option.
584 -s
586 --strip-all
587 Omit all symbol information from the output file.
588 -S
590 --strip-debug
591 Omit debugger symbol information (but not all symbols) from the
592 output file.
593 --strip-discarded
595 --no-strip-discarded
596 Omit (or do not omit) global symbols defined in discarded sections.
597 Enabled by default.
598 -t
600 --trace
601 Print the names of the input files as ld processes them. If -t is
602 given twice then members within archives are also printed. -t
603 output is useful to generate a list of all the object files and
604 scripts involved in linking, for example, when packaging files for
605 a linker bug report.
606 -T scriptfile
608 --script=scriptfile
609 Use scriptfile as the linker script. This script replaces ld's
610 default linker script (rather than adding to it), so commandfile
611 must specify everything necessary to describe the output file.
612 If scriptfile does not exist in the current directory, "ld" looks
613 for it in the directories specified by any preceding -L options.
614 Multiple -T options accumulate.
615 -dT scriptfile
617 --default-script=scriptfile
618 Use scriptfile as the default linker script.
619 This option is similar to the --script option except that
621 processing of the script is delayed until after the rest of the
622 command line has been processed. This allows options placed after
623 the --default-script option on the command line to affect the
624 behaviour of the linker script, which can be important when the
625 linker command line cannot be directly controlled by the user. (eg
626 because the command line is being constructed by another tool, such
627 as gcc).
628 -u symbol
630 --undefined=symbol
631 Force symbol to be entered in the output file as an undefined
632 symbol. Doing this may, for example, trigger linking of additional
633 modules from standard libraries. -u may be repeated with different
634 option arguments to enter additional undefined symbols. This
635 option is equivalent to the "EXTERN" linker script command.
636 If this option is being used to force additional modules to be
638 pulled into the link, and if it is an error for the symbol to
639 remain undefined, then the option --require-defined should be used
640 instead.
641 --require-defined=symbol
643 Require that symbol is defined in the output file. This option is
644 the same as option --undefined except that if symbol is not defined
645 in the output file then the linker will issue an error and exit.
646 The same effect can be achieved in a linker script by using
647 "EXTERN", "ASSERT" and "DEFINED" together. This option can be used
648 multiple times to require additional symbols.
649 -Ur For anything other than C++ programs, this option is equivalent to
651 -r: it generates relocatable output---i.e., an output file that can
652 in turn serve as input to ld. When linking C++ programs, -Ur does
653 resolve references to constructors, unlike -r. It does not work to
654 use -Ur on files that were themselves linked with -Ur; once the
655 constructor table has been built, it cannot be added to. Use -Ur
656 only for the last partial link, and -r for the others.
657 --orphan-handling=MODE
659 Control how orphan sections are handled. An orphan section is one
660 not specifically mentioned in a linker script.
661 MODE can have any of the following values:
663 "place"
665 Orphan sections are placed into a suitable output section
666 following the strategy described in Orphan Sections. The
667 option --unique also affects how sections are placed.
668 "discard"
670 All orphan sections are discarded, by placing them in the
671 /DISCARD/ section.
672 "warn"
674 The linker will place the orphan section as for "place" and
675 also issue a warning.
676 "error"
678 The linker will exit with an error if any orphan section is
679 found.
680 The default if --orphan-handling is not given is "place".
682 --unique[=SECTION]
684 Creates a separate output section for every input section matching
685 SECTION, or if the optional wildcard SECTION argument is missing,
686 for every orphan input section. An orphan section is one not
687 specifically mentioned in a linker script. You may use this option
688 multiple times on the command line; It prevents the normal merging
689 of input sections with the same name, overriding output section
690 assignments in a linker script.
691 -v
693 --version
694 -V Display the version number for ld. The -V option also lists the
695 supported emulations.
696 -x
698 --discard-all
699 Delete all local symbols.
700 -X
702 --discard-locals
703 Delete all temporary local symbols. (These symbols start with
704 system-specific local label prefixes, typically .L for ELF systems
705 or L for traditional a.out systems.)
706 -y symbol
708 --trace-symbol=symbol
709 Print the name of each linked file in which symbol appears. This
710 option may be given any number of times. On many systems it is
711 necessary to prepend an underscore.
712 This option is useful when you have an undefined symbol in your
714 link but don't know where the reference is coming from.
715 -Y path
717 Add path to the default library search path. This option exists
718 for Solaris compatibility.
719 -z keyword
721 The recognized keywords are:
722 bndplt
724 Always generate BND prefix in PLT entries. Supported for
725 Linux/x86_64.
726 call-nop=prefix-addr
728 call-nop=suffix-nop
729 call-nop=prefix-byte
730 call-nop=suffix-byte
731 Specify the 1-byte "NOP" padding when transforming indirect
732 call to a locally defined function, foo, via its GOT slot.
733 call-nop=prefix-addr generates "0x67 call foo".
734 call-nop=suffix-nop generates "call foo 0x90".
735 call-nop=prefix-byte generates "byte call foo".
736 call-nop=suffix-byte generates "call foo byte". Supported for
737 i386 and x86_64.
738 combreloc
740 nocombreloc
741 Combine multiple dynamic relocation sections and sort to
742 improve dynamic symbol lookup caching. Do not do this if
743 nocombreloc.
744 common
746 nocommon
747 Generate common symbols with STT_COMMON type during a
748 relocatable link. Use STT_OBJECT type if nocommon.
749 common-page-size=value
751 Set the page size most commonly used to value. Memory image
752 layout will be optimized to minimize memory pages if the system
753 is using pages of this size.
754 defs
756 Report unresolved symbol references from regular object files.
757 This is done even if the linker is creating a non-symbolic
758 shared library. This option is the inverse of -z undefs.
759 dynamic-undefined-weak
761 nodynamic-undefined-weak
762 Make undefined weak symbols dynamic when building a dynamic
763 object, if they are referenced from a regular object file and
764 not forced local by symbol visibility or versioning. Do not
765 make them dynamic if nodynamic-undefined-weak. If neither
766 option is given, a target may default to either option being in
767 force, or make some other selection of undefined weak symbols
768 dynamic. Not all targets support these options.
769 execstack
771 Marks the object as requiring executable stack.
772 global
774 This option is only meaningful when building a shared object.
775 It makes the symbols defined by this shared object available
776 for symbol resolution of subsequently loaded libraries.
777 globalaudit
779 This option is only meaningful when building a dynamic
780 executable. This option marks the executable as requiring
781 global auditing by setting the "DF_1_GLOBAUDIT" bit in the
782 "DT_FLAGS_1" dynamic tag. Global auditing requires that any
783 auditing library defined via the --depaudit or -P command-line
784 options be run for all dynamic objects loaded by the
785 application.
786 ibtplt
788 Generate Intel Indirect Branch Tracking (IBT) enabled PLT
789 entries. Supported for Linux/i386 and Linux/x86_64.
790 ibt Generate GNU_PROPERTY_X86_FEATURE_1_IBT in .note.gnu.property
792 section to indicate compatibility with IBT. This also implies
793 ibtplt. Supported for Linux/i386 and Linux/x86_64.
794 initfirst
796 This option is only meaningful when building a shared object.
797 It marks the object so that its runtime initialization will
798 occur before the runtime initialization of any other objects
799 brought into the process at the same time. Similarly the
800 runtime finalization of the object will occur after the runtime
801 finalization of any other objects.
802 interpose
804 Specify that the dynamic loader should modify its symbol search
805 order so that symbols in this shared library interpose all
806 other shared libraries not so marked.
807 lazy
809 When generating an executable or shared library, mark it to
810 tell the dynamic linker to defer function call resolution to
811 the point when the function is called (lazy binding), rather
812 than at load time. Lazy binding is the default.
813 loadfltr
815 Specify that the object's filters be processed immediately at
816 runtime.
817 max-page-size=value
819 Set the maximum memory page size supported to value.
820 muldefs
822 Allow multiple definitions.
823 nocopyreloc
825 Disable linker generated .dynbss variables used in place of
826 variables defined in shared libraries. May result in dynamic
827 text relocations.
828 nodefaultlib
830 Specify that the dynamic loader search for dependencies of this
831 object should ignore any default library search paths.
832 nodelete
834 Specify that the object shouldn't be unloaded at runtime.
835 nodlopen
837 Specify that the object is not available to "dlopen".
838 nodump
840 Specify that the object can not be dumped by "dldump".
841 noexecstack
843 Marks the object as not requiring executable stack.
844 noextern-protected-data
846 Don't treat protected data symbols as external when building a
847 shared library. This option overrides the linker backend
848 default. It can be used to work around incorrect relocations
849 against protected data symbols generated by compiler. Updates
850 on protected data symbols by another module aren't visible to
851 the resulting shared library. Supported for i386 and x86-64.
852 noreloc-overflow
854 Disable relocation overflow check. This can be used to disable
855 relocation overflow check if there will be no dynamic
856 relocation overflow at run-time. Supported for x86_64.
857 now When generating an executable or shared library, mark it to
859 tell the dynamic linker to resolve all symbols when the program
860 is started, or when the shared library is loaded by dlopen,
861 instead of deferring function call resolution to the point when
862 the function is first called.
863 origin
865 Specify that the object requires $ORIGIN handling in paths.
866 relro
868 norelro
869 Create an ELF "PT_GNU_RELRO" segment header in the object.
870 This specifies a memory segment that should be made read-only
871 after relocation, if supported. Specifying common-page-size
872 smaller than the system page size will render this protection
873 ineffective. Don't create an ELF "PT_GNU_RELRO" segment if
874 norelro.
875 separate-code
877 noseparate-code
878 Create separate code "PT_LOAD" segment header in the object.
879 This specifies a memory segment that should contain only
880 instructions and must be in wholly disjoint pages from any
881 other data. Don't create separate code "PT_LOAD" segment if
882 noseparate-code is used.
883 shstk
885 Generate GNU_PROPERTY_X86_FEATURE_1_SHSTK in .note.gnu.property
886 section to indicate compatibility with Intel Shadow Stack.
887 Supported for Linux/i386 and Linux/x86_64.
888 stack-size=value
890 Specify a stack size for an ELF "PT_GNU_STACK" segment.
891 Specifying zero will override any default non-zero sized
892 "PT_GNU_STACK" segment creation.
893 text
895 notext
896 textoff
897 Report an error if DT_TEXTREL is set, i.e., if the binary has
898 dynamic relocations in read-only sections. Don't report an
899 error if notext or textoff.
900 undefs
902 Do not report unresolved symbol references from regular object
903 files, either when creating an executable, or when creating a
904 shared library. This option is the inverse of -z defs.
905 Other keywords are ignored for Solaris compatibility.
907 -( archives -)
909 --start-group archives --end-group
910 The archives should be a list of archive files. They may be either
911 explicit file names, or -l options.
912 The specified archives are searched repeatedly until no new
914 undefined references are created. Normally, an archive is searched
915 only once in the order that it is specified on the command line.
916 If a symbol in that archive is needed to resolve an undefined
917 symbol referred to by an object in an archive that appears later on
918 the command line, the linker would not be able to resolve that
919 reference. By grouping the archives, they all be searched
920 repeatedly until all possible references are resolved.
921 Using this option has a significant performance cost. It is best
923 to use it only when there are unavoidable circular references
924 between two or more archives.
925 --accept-unknown-input-arch
927 --no-accept-unknown-input-arch
928 Tells the linker to accept input files whose architecture cannot be
929 recognised. The assumption is that the user knows what they are
930 doing and deliberately wants to link in these unknown input files.
931 This was the default behaviour of the linker, before release 2.14.
932 The default behaviour from release 2.14 onwards is to reject such
933 input files, and so the --accept-unknown-input-arch option has been
934 added to restore the old behaviour.
935 --as-needed
937 --no-as-needed
938 This option affects ELF DT_NEEDED tags for dynamic libraries
939 mentioned on the command line after the --as-needed option.
940 Normally the linker will add a DT_NEEDED tag for each dynamic
941 library mentioned on the command line, regardless of whether the
942 library is actually needed or not. --as-needed causes a DT_NEEDED
943 tag to only be emitted for a library that at that point in the link
944 satisfies a non-weak undefined symbol reference from a regular
945 object file or, if the library is not found in the DT_NEEDED lists
946 of other needed libraries, a non-weak undefined symbol reference
947 from another needed dynamic library. Object files or libraries
948 appearing on the command line after the library in question do not
949 affect whether the library is seen as needed. This is similar to
950 the rules for extraction of object files from archives.
951 --no-as-needed restores the default behaviour.
952 --add-needed
954 --no-add-needed
955 These two options have been deprecated because of the similarity of
956 their names to the --as-needed and --no-as-needed options. They
957 have been replaced by --copy-dt-needed-entries and
958 --no-copy-dt-needed-entries.
959 -assert keyword
961 This option is ignored for SunOS compatibility.
962 -Bdynamic
964 -dy
965 -call_shared
966 Link against dynamic libraries. This is only meaningful on
967 platforms for which shared libraries are supported. This option is
968 normally the default on such platforms. The different variants of
969 this option are for compatibility with various systems. You may
970 use this option multiple times on the command line: it affects
971 library searching for -l options which follow it.
972 -Bgroup
974 Set the "DF_1_GROUP" flag in the "DT_FLAGS_1" entry in the dynamic
975 section. This causes the runtime linker to handle lookups in this
976 object and its dependencies to be performed only inside the group.
977 --unresolved-symbols=report-all is implied. This option is only
978 meaningful on ELF platforms which support shared libraries.
979 -Bstatic
981 -dn
982 -non_shared
983 -static
984 Do not link against shared libraries. This is only meaningful on
985 platforms for which shared libraries are supported. The different
986 variants of this option are for compatibility with various systems.
987 You may use this option multiple times on the command line: it
988 affects library searching for -l options which follow it. This
989 option also implies --unresolved-symbols=report-all. This option
990 can be used with -shared. Doing so means that a shared library is
991 being created but that all of the library's external references
992 must be resolved by pulling in entries from static libraries.
993 -Bsymbolic
995 When creating a shared library, bind references to global symbols
996 to the definition within the shared library, if any. Normally, it
997 is possible for a program linked against a shared library to
998 override the definition within the shared library. This option can
999 also be used with the --export-dynamic option, when creating a
1000 position independent executable, to bind references to global
1001 symbols to the definition within the executable. This option is
1002 only meaningful on ELF platforms which support shared libraries and
1003 position independent executables.
1004 -Bsymbolic-functions
1006 When creating a shared library, bind references to global function
1007 symbols to the definition within the shared library, if any. This
1008 option can also be used with the --export-dynamic option, when
1009 creating a position independent executable, to bind references to
1010 global function symbols to the definition within the executable.
1011 This option is only meaningful on ELF platforms which support
1012 shared libraries and position independent executables.
1013 --dynamic-list=dynamic-list-file
1015 Specify the name of a dynamic list file to the linker. This is
1016 typically used when creating shared libraries to specify a list of
1017 global symbols whose references shouldn't be bound to the
1018 definition within the shared library, or creating dynamically
1019 linked executables to specify a list of symbols which should be
1020 added to the symbol table in the executable. This option is only
1021 meaningful on ELF platforms which support shared libraries.
1022 The format of the dynamic list is the same as the version node
1024 without scope and node name. See VERSION for more information.
1025 --dynamic-list-data
1027 Include all global data symbols to the dynamic list.
1028 --dynamic-list-cpp-new
1030 Provide the builtin dynamic list for C++ operator new and delete.
1031 It is mainly useful for building shared libstdc++.
1032 --dynamic-list-cpp-typeinfo
1034 Provide the builtin dynamic list for C++ runtime type
1035 identification.
1036 --check-sections
1038 --no-check-sections
1039 Asks the linker not to check section addresses after they have been
1040 assigned to see if there are any overlaps. Normally the linker
1041 will perform this check, and if it finds any overlaps it will
1042 produce suitable error messages. The linker does know about, and
1043 does make allowances for sections in overlays. The default
1044 behaviour can be restored by using the command-line switch
1045 --check-sections. Section overlap is not usually checked for
1046 relocatable links. You can force checking in that case by using
1047 the --check-sections option.
1048 --copy-dt-needed-entries
1050 --no-copy-dt-needed-entries
1051 This option affects the treatment of dynamic libraries referred to
1052 by DT_NEEDED tags inside ELF dynamic libraries mentioned on the
1053 command line. Normally the linker won't add a DT_NEEDED tag to the
1054 output binary for each library mentioned in a DT_NEEDED tag in an
1055 input dynamic library. With --copy-dt-needed-entries specified on
1056 the command line however any dynamic libraries that follow it will
1057 have their DT_NEEDED entries added. The default behaviour can be
1058 restored with --no-copy-dt-needed-entries.
1059 This option also has an effect on the resolution of symbols in
1061 dynamic libraries. With --copy-dt-needed-entries dynamic libraries
1062 mentioned on the command line will be recursively searched,
1063 following their DT_NEEDED tags to other libraries, in order to
1064 resolve symbols required by the output binary. With the default
1065 setting however the searching of dynamic libraries that follow it
1066 will stop with the dynamic library itself. No DT_NEEDED links will
1067 be traversed to resolve symbols.
1068 --cref
1070 Output a cross reference table. If a linker map file is being
1071 generated, the cross reference table is printed to the map file.
1072 Otherwise, it is printed on the standard output.
1073 The format of the table is intentionally simple, so that it may be
1075 easily processed by a script if necessary. The symbols are printed
1076 out, sorted by name. For each symbol, a list of file names is
1077 given. If the symbol is defined, the first file listed is the
1078 location of the definition. If the symbol is defined as a common
1079 value then any files where this happens appear next. Finally any
1080 files that reference the symbol are listed.
1081 --no-define-common
1083 This option inhibits the assignment of addresses to common symbols.
1084 The script command "INHIBIT_COMMON_ALLOCATION" has the same effect.
1085 The --no-define-common option allows decoupling the decision to
1087 assign addresses to Common symbols from the choice of the output
1088 file type; otherwise a non-Relocatable output type forces assigning
1089 addresses to Common symbols. Using --no-define-common allows
1090 Common symbols that are referenced from a shared library to be
1091 assigned addresses only in the main program. This eliminates the
1092 unused duplicate space in the shared library, and also prevents any
1093 possible confusion over resolving to the wrong duplicate when there
1094 are many dynamic modules with specialized search paths for runtime
1095 symbol resolution.
1096 --force-group-allocation
1098 This option causes the linker to place section group members like
1099 normal input sections, and to delete the section groups. This is
1100 the default behaviour for a final link but this option can be used
1101 to change the behaviour of a relocatable link (-r). The script
1102 command "FORCE_GROUP_ALLOCATION" has the same effect.
1103 --defsym=symbol=expression
1105 Create a global symbol in the output file, containing the absolute
1106 address given by expression. You may use this option as many times
1107 as necessary to define multiple symbols in the command line. A
1108 limited form of arithmetic is supported for the expression in this
1109 context: you may give a hexadecimal constant or the name of an
1110 existing symbol, or use "+" and "-" to add or subtract hexadecimal
1111 constants or symbols. If you need more elaborate expressions,
1112 consider using the linker command language from a script. Note:
1113 there should be no white space between symbol, the equals sign
1114 ("="), and expression.
1115 --demangle[=style]
1117 --no-demangle
1118 These options control whether to demangle symbol names in error
1119 messages and other output. When the linker is told to demangle, it
1120 tries to present symbol names in a readable fashion: it strips
1121 leading underscores if they are used by the object file format, and
1122 converts C++ mangled symbol names into user readable names.
1123 Different compilers have different mangling styles. The optional
1124 demangling style argument can be used to choose an appropriate
1125 demangling style for your compiler. The linker will demangle by
1126 default unless the environment variable COLLECT_NO_DEMANGLE is set.
1127 These options may be used to override the default.
1128 -Ifile
1130 --dynamic-linker=file
1131 Set the name of the dynamic linker. This is only meaningful when
1132 generating dynamically linked ELF executables. The default dynamic
1133 linker is normally correct; don't use this unless you know what you
1134 are doing.
1135 --no-dynamic-linker
1137 When producing an executable file, omit the request for a dynamic
1138 linker to be used at load-time. This is only meaningful for ELF
1139 executables that contain dynamic relocations, and usually requires
1140 entry point code that is capable of processing these relocations.
1141 --embedded-relocs
1143 This option is similar to the --emit-relocs option except that the
1144 relocs are stored in a target specific section. This option is
1145 only supported by the BFIN, CR16 and M68K targets.
1146 --disable-multiple-abs-defs
1148 Do not allow multiple definitions with symbols included in filename
1149 invoked by -R or --just-symbols
1150 --fatal-warnings
1152 --no-fatal-warnings
1153 Treat all warnings as errors. The default behaviour can be
1154 restored with the option --no-fatal-warnings.
1155 --force-exe-suffix
1157 Make sure that an output file has a .exe suffix.
1158 If a successfully built fully linked output file does not have a
1160 ".exe" or ".dll" suffix, this option forces the linker to copy the
1161 output file to one of the same name with a ".exe" suffix. This
1162 option is useful when using unmodified Unix makefiles on a
1163 Microsoft Windows host, since some versions of Windows won't run an
1164 image unless it ends in a ".exe" suffix.
1165 --gc-sections
1167 --no-gc-sections
1168 Enable garbage collection of unused input sections. It is ignored
1169 on targets that do not support this option. The default behaviour
1170 (of not performing this garbage collection) can be restored by
1171 specifying --no-gc-sections on the command line. Note that garbage
1172 collection for COFF and PE format targets is supported, but the
1173 implementation is currently considered to be experimental.
1174 --gc-sections decides which input sections are used by examining
1176 symbols and relocations. The section containing the entry symbol
1177 and all sections containing symbols undefined on the command-line
1178 will be kept, as will sections containing symbols referenced by
1179 dynamic objects. Note that when building shared libraries, the
1180 linker must assume that any visible symbol is referenced. Once
1181 this initial set of sections has been determined, the linker
1182 recursively marks as used any section referenced by their
1183 relocations. See --entry, --undefined, and --gc-keep-exported.
1184 This option can be set when doing a partial link (enabled with
1186 option -r). In this case the root of symbols kept must be
1187 explicitly specified either by one of the options --entry,
1188 --undefined, or --gc-keep-exported or by a "ENTRY" command in the
1189 linker script.
1190 --print-gc-sections
1192 --no-print-gc-sections
1193 List all sections removed by garbage collection. The listing is
1194 printed on stderr. This option is only effective if garbage
1195 collection has been enabled via the --gc-sections) option. The
1196 default behaviour (of not listing the sections that are removed)
1197 can be restored by specifying --no-print-gc-sections on the command
1198 line.
1199 --gc-keep-exported
1201 When --gc-sections is enabled, this option prevents garbage
1202 collection of unused input sections that contain global symbols
1203 having default or protected visibility. This option is intended to
1204 be used for executables where unreferenced sections would otherwise
1205 be garbage collected regardless of the external visibility of
1206 contained symbols. Note that this option has no effect when
1207 linking shared objects since it is already the default behaviour.
1208 This option is only supported for ELF format targets.
1209 --print-output-format
1211 Print the name of the default output format (perhaps influenced by
1212 other command-line options). This is the string that would appear
1213 in an "OUTPUT_FORMAT" linker script command.
1214 --print-memory-usage
1216 Print used size, total size and used size of memory regions created
1217 with the MEMORY command. This is useful on embedded targets to
1218 have a quick view of amount of free memory. The format of the
1219 output has one headline and one line per region. It is both human
1220 readable and easily parsable by tools. Here is an example of an
1221 output:
1222 Memory region Used Size Region Size %age Used
1224 ROM: 256 KB 1 MB 25.00%
1225 RAM: 32 B 2 GB 0.00%
1226 --help
1228 Print a summary of the command-line options on the standard output
1229 and exit.
1230 --target-help
1232 Print a summary of all target specific options on the standard
1233 output and exit.
1234 -Map=mapfile
1236 Print a link map to the file mapfile. See the description of the
1237 -M option, above.
1238 --no-keep-memory
1240 ld normally optimizes for speed over memory usage by caching the
1241 symbol tables of input files in memory. This option tells ld to
1242 instead optimize for memory usage, by rereading the symbol tables
1243 as necessary. This may be required if ld runs out of memory space
1244 while linking a large executable.
1245 --no-undefined
1247 -z defs
1248 Report unresolved symbol references from regular object files.
1249 This is done even if the linker is creating a non-symbolic shared
1250 library. The switch --[no-]allow-shlib-undefined controls the
1251 behaviour for reporting unresolved references found in shared
1252 libraries being linked in.
1253 The effects of this option can be reverted by using "-z undefs".
1255 --allow-multiple-definition
1257 -z muldefs
1258 Normally when a symbol is defined multiple times, the linker will
1259 report a fatal error. These options allow multiple definitions and
1260 the first definition will be used.
1261 --allow-shlib-undefined
1263 --no-allow-shlib-undefined
1264 Allows or disallows undefined symbols in shared libraries. This
1265 switch is similar to --no-undefined except that it determines the
1266 behaviour when the undefined symbols are in a shared library rather
1267 than a regular object file. It does not affect how undefined
1268 symbols in regular object files are handled.
1269 The default behaviour is to report errors for any undefined symbols
1271 referenced in shared libraries if the linker is being used to
1272 create an executable, but to allow them if the linker is being used
1273 to create a shared library.
1274 The reasons for allowing undefined symbol references in shared
1276 libraries specified at link time are that:
1277 · A shared library specified at link time may not be the same as
1279 the one that is available at load time, so the symbol might
1280 actually be resolvable at load time.
1281 · There are some operating systems, eg BeOS and HPPA, where
1283 undefined symbols in shared libraries are normal.
1284 The BeOS kernel for example patches shared libraries at load
1286 time to select whichever function is most appropriate for the
1287 current architecture. This is used, for example, to
1288 dynamically select an appropriate memset function.
1289 --no-undefined-version
1291 Normally when a symbol has an undefined version, the linker will
1292 ignore it. This option disallows symbols with undefined version and
1293 a fatal error will be issued instead.
1294 --default-symver
1296 Create and use a default symbol version (the soname) for
1297 unversioned exported symbols.
1298 --default-imported-symver
1300 Create and use a default symbol version (the soname) for
1301 unversioned imported symbols.
1302 --no-warn-mismatch
1304 Normally ld will give an error if you try to link together input
1305 files that are mismatched for some reason, perhaps because they
1306 have been compiled for different processors or for different
1307 endiannesses. This option tells ld that it should silently permit
1308 such possible errors. This option should only be used with care,
1309 in cases when you have taken some special action that ensures that
1310 the linker errors are inappropriate.
1311 --no-warn-search-mismatch
1313 Normally ld will give a warning if it finds an incompatible library
1314 during a library search. This option silences the warning.
1315 --no-whole-archive
1317 Turn off the effect of the --whole-archive option for subsequent
1318 archive files.
1319 --noinhibit-exec
1321 Retain the executable output file whenever it is still usable.
1322 Normally, the linker will not produce an output file if it
1323 encounters errors during the link process; it exits without writing
1324 an output file when it issues any error whatsoever.
1325 -nostdlib
1327 Only search library directories explicitly specified on the command
1328 line. Library directories specified in linker scripts (including
1329 linker scripts specified on the command line) are ignored.
1330 --oformat=output-format
1332 ld may be configured to support more than one kind of object file.
1333 If your ld is configured this way, you can use the --oformat option
1334 to specify the binary format for the output object file. Even when
1335 ld is configured to support alternative object formats, you don't
1336 usually need to specify this, as ld should be configured to produce
1337 as a default output format the most usual format on each machine.
1338 output-format is a text string, the name of a particular format
1339 supported by the BFD libraries. (You can list the available binary
1340 formats with objdump -i.) The script command "OUTPUT_FORMAT" can
1341 also specify the output format, but this option overrides it.
1342 --out-implib file
1344 Create an import library in file corresponding to the executable
1345 the linker is generating (eg. a DLL or ELF program). This import
1346 library (which should be called "*.dll.a" or "*.a" for DLLs) may be
1347 used to link clients against the generated executable; this
1348 behaviour makes it possible to skip a separate import library
1349 creation step (eg. "dlltool" for DLLs). This option is only
1350 available for the i386 PE and ELF targetted ports of the linker.
1351 -pie
1353 --pic-executable
1354 Create a position independent executable. This is currently only
1355 supported on ELF platforms. Position independent executables are
1356 similar to shared libraries in that they are relocated by the
1357 dynamic linker to the virtual address the OS chooses for them
1358 (which can vary between invocations). Like normal dynamically
1359 linked executables they can be executed and symbols defined in the
1360 executable cannot be overridden by shared libraries.
1361 -qmagic
1363 This option is ignored for Linux compatibility.
1364 -Qy This option is ignored for SVR4 compatibility.
1366 --relax
1368 --no-relax
1369 An option with machine dependent effects. This option is only
1370 supported on a few targets.
1371 On some platforms the --relax option performs target specific,
1373 global optimizations that become possible when the linker resolves
1374 addressing in the program, such as relaxing address modes,
1375 synthesizing new instructions, selecting shorter version of current
1376 instructions, and combining constant values.
1377 On some platforms these link time global optimizations may make
1379 symbolic debugging of the resulting executable impossible. This is
1380 known to be the case for the Matsushita MN10200 and MN10300 family
1381 of processors.
1382 On platforms where this is not supported, --relax is accepted, but
1384 ignored.
1385 On platforms where --relax is accepted the option --no-relax can be
1387 used to disable the feature.
1388 --retain-symbols-file=filename
1390 Retain only the symbols listed in the file filename, discarding all
1391 others. filename is simply a flat file, with one symbol name per
1392 line. This option is especially useful in environments (such as
1393 VxWorks) where a large global symbol table is accumulated
1394 gradually, to conserve run-time memory.
1395 --retain-symbols-file does not discard undefined symbols, or
1397 symbols needed for relocations.
1398 You may only specify --retain-symbols-file once in the command
1400 line. It overrides -s and -S.
1401 -rpath=dir
1403 Add a directory to the runtime library search path. This is used
1404 when linking an ELF executable with shared objects. All -rpath
1405 arguments are concatenated and passed to the runtime linker, which
1406 uses them to locate shared objects at runtime. The -rpath option
1407 is also used when locating shared objects which are needed by
1408 shared objects explicitly included in the link; see the description
1409 of the -rpath-link option. If -rpath is not used when linking an
1410 ELF executable, the contents of the environment variable
1411 "LD_RUN_PATH" will be used if it is defined.
1412 The -rpath option may also be used on SunOS. By default, on SunOS,
1414 the linker will form a runtime search path out of all the -L
1415 options it is given. If a -rpath option is used, the runtime
1416 search path will be formed exclusively using the -rpath options,
1417 ignoring the -L options. This can be useful when using gcc, which
1418 adds many -L options which may be on NFS mounted file systems.
1419 For compatibility with other ELF linkers, if the -R option is
1421 followed by a directory name, rather than a file name, it is
1422 treated as the -rpath option.
1423 -rpath-link=dir
1425 When using ELF or SunOS, one shared library may require another.
1426 This happens when an "ld -shared" link includes a shared library as
1427 one of the input files.
1428 When the linker encounters such a dependency when doing a non-
1430 shared, non-relocatable link, it will automatically try to locate
1431 the required shared library and include it in the link, if it is
1432 not included explicitly. In such a case, the -rpath-link option
1433 specifies the first set of directories to search. The -rpath-link
1434 option may specify a sequence of directory names either by
1435 specifying a list of names separated by colons, or by appearing
1436 multiple times.
1437 The tokens $ORIGIN and $LIB can appear in these search directories.
1439 They will be replaced by the full path to the directory containing
1440 the program or shared object in the case of $ORIGIN and either lib
1441 - for 32-bit binaries - or lib64 - for 64-bit binaries - in the
1442 case of $LIB.
1443 The alternative form of these tokens - ${ORIGIN} and ${LIB} can
1445 also be used. The token $PLATFORM is not supported.
1446 This option should be used with caution as it overrides the search
1448 path that may have been hard compiled into a shared library. In
1449 such a case it is possible to use unintentionally a different
1450 search path than the runtime linker would do.
1451 The linker uses the following search paths to locate required
1453 shared libraries:
1454 1. Any directories specified by -rpath-link options.
1456 2. Any directories specified by -rpath options. The difference
1458 between -rpath and -rpath-link is that directories specified by
1459 -rpath options are included in the executable and used at
1460 runtime, whereas the -rpath-link option is only effective at
1461 link time. Searching -rpath in this way is only supported by
1462 native linkers and cross linkers which have been configured
1463 with the --with-sysroot option.
1464 3. On an ELF system, for native linkers, if the -rpath and
1466 -rpath-link options were not used, search the contents of the
1467 environment variable "LD_RUN_PATH".
1468 4. On SunOS, if the -rpath option was not used, search any
1470 directories specified using -L options.
1471 5. For a native linker, search the contents of the environment
1473 variable "LD_LIBRARY_PATH".
1474 6. For a native ELF linker, the directories in "DT_RUNPATH" or
1476 "DT_RPATH" of a shared library are searched for shared
1477 libraries needed by it. The "DT_RPATH" entries are ignored if
1478 "DT_RUNPATH" entries exist.
1479 7. The default directories, normally /lib and /usr/lib.
1481 8. For a native linker on an ELF system, if the file
1483 /etc/ld.so.conf exists, the list of directories found in that
1484 file.
1485 If the required shared library is not found, the linker will issue
1487 a warning and continue with the link.
1488 -shared
1490 -Bshareable
1491 Create a shared library. This is currently only supported on ELF,
1492 XCOFF and SunOS platforms. On SunOS, the linker will automatically
1493 create a shared library if the -e option is not used and there are
1494 undefined symbols in the link.
1495 --sort-common
1497 --sort-common=ascending
1498 --sort-common=descending
1499 This option tells ld to sort the common symbols by alignment in
1500 ascending or descending order when it places them in the
1501 appropriate output sections. The symbol alignments considered are
1502 sixteen-byte or larger, eight-byte, four-byte, two-byte, and one-
1503 byte. This is to prevent gaps between symbols due to alignment
1504 constraints. If no sorting order is specified, then descending
1505 order is assumed.
1506 --sort-section=name
1508 This option will apply "SORT_BY_NAME" to all wildcard section
1509 patterns in the linker script.
1510 --sort-section=alignment
1512 This option will apply "SORT_BY_ALIGNMENT" to all wildcard section
1513 patterns in the linker script.
1514 --spare-dynamic-tags=count
1516 This option specifies the number of empty slots to leave in the
1517 .dynamic section of ELF shared objects. Empty slots may be needed
1518 by post processing tools, such as the prelinker. The default is 5.
1519 --split-by-file[=size]
1521 Similar to --split-by-reloc but creates a new output section for
1522 each input file when size is reached. size defaults to a size of 1
1523 if not given.
1524 --split-by-reloc[=count]
1526 Tries to creates extra sections in the output file so that no
1527 single output section in the file contains more than count
1528 relocations. This is useful when generating huge relocatable files
1529 for downloading into certain real time kernels with the COFF object
1530 file format; since COFF cannot represent more than 65535
1531 relocations in a single section. Note that this will fail to work
1532 with object file formats which do not support arbitrary sections.
1533 The linker will not split up individual input sections for
1534 redistribution, so if a single input section contains more than
1535 count relocations one output section will contain that many
1536 relocations. count defaults to a value of 32768.
1537 --stats
1539 Compute and display statistics about the operation of the linker,
1540 such as execution time and memory usage.
1541 --sysroot=directory
1543 Use directory as the location of the sysroot, overriding the
1544 configure-time default. This option is only supported by linkers
1545 that were configured using --with-sysroot.
1546 --task-link
1548 This is used by COFF/PE based targets to create a task-linked
1549 object file where all of the global symbols have been converted to
1550 statics.
1551 --traditional-format
1553 For some targets, the output of ld is different in some ways from
1554 the output of some existing linker. This switch requests ld to use
1555 the traditional format instead.
1556 For example, on SunOS, ld combines duplicate entries in the symbol
1558 string table. This can reduce the size of an output file with full
1559 debugging information by over 30 percent. Unfortunately, the SunOS
1560 "dbx" program can not read the resulting program ("gdb" has no
1561 trouble). The --traditional-format switch tells ld to not combine
1562 duplicate entries.
1563 --section-start=sectionname=org
1565 Locate a section in the output file at the absolute address given
1566 by org. You may use this option as many times as necessary to
1567 locate multiple sections in the command line. org must be a single
1568 hexadecimal integer; for compatibility with other linkers, you may
1569 omit the leading 0x usually associated with hexadecimal values.
1570 Note: there should be no white space between sectionname, the
1571 equals sign ("="), and org.
1572 -Tbss=org
1574 -Tdata=org
1575 -Ttext=org
1576 Same as --section-start, with ".bss", ".data" or ".text" as the
1577 sectionname.
1578 -Ttext-segment=org
1580 When creating an ELF executable, it will set the address of the
1581 first byte of the text segment.
1582 -Trodata-segment=org
1584 When creating an ELF executable or shared object for a target where
1585 the read-only data is in its own segment separate from the
1586 executable text, it will set the address of the first byte of the
1587 read-only data segment.
1588 -Tldata-segment=org
1590 When creating an ELF executable or shared object for x86-64 medium
1591 memory model, it will set the address of the first byte of the
1592 ldata segment.
1593 --unresolved-symbols=method
1595 Determine how to handle unresolved symbols. There are four
1596 possible values for method:
1597 ignore-all
1599 Do not report any unresolved symbols.
1600 report-all
1602 Report all unresolved symbols. This is the default.
1603 ignore-in-object-files
1605 Report unresolved symbols that are contained in shared
1606 libraries, but ignore them if they come from regular object
1607 files.
1608 ignore-in-shared-libs
1610 Report unresolved symbols that come from regular object files,
1611 but ignore them if they come from shared libraries. This can
1612 be useful when creating a dynamic binary and it is known that
1613 all the shared libraries that it should be referencing are
1614 included on the linker's command line.
1615 The behaviour for shared libraries on their own can also be
1617 controlled by the --[no-]allow-shlib-undefined option.
1618 Normally the linker will generate an error message for each
1620 reported unresolved symbol but the option --warn-unresolved-symbols
1621 can change this to a warning.
1622 --dll-verbose
1624 --verbose[=NUMBER]
1625 Display the version number for ld and list the linker emulations
1626 supported. Display which input files can and cannot be opened.
1627 Display the linker script being used by the linker. If the optional
1628 NUMBER argument > 1, plugin symbol status will also be displayed.
1629 --version-script=version-scriptfile
1631 Specify the name of a version script to the linker. This is
1632 typically used when creating shared libraries to specify additional
1633 information about the version hierarchy for the library being
1634 created. This option is only fully supported on ELF platforms
1635 which support shared libraries; see VERSION. It is partially
1636 supported on PE platforms, which can use version scripts to filter
1637 symbol visibility in auto-export mode: any symbols marked local in
1638 the version script will not be exported.
1639 --warn-common
1641 Warn when a common symbol is combined with another common symbol or
1642 with a symbol definition. Unix linkers allow this somewhat sloppy
1643 practice, but linkers on some other operating systems do not. This
1644 option allows you to find potential problems from combining global
1645 symbols. Unfortunately, some C libraries use this practice, so you
1646 may get some warnings about symbols in the libraries as well as in
1647 your programs.
1648 There are three kinds of global symbols, illustrated here by C
1650 examples:
1651 int i = 1;
1653 A definition, which goes in the initialized data section of the
1654 output file.
1655 extern int i;
1657 An undefined reference, which does not allocate space. There
1658 must be either a definition or a common symbol for the variable
1659 somewhere.
1660 int i;
1662 A common symbol. If there are only (one or more) common
1663 symbols for a variable, it goes in the uninitialized data area
1664 of the output file. The linker merges multiple common symbols
1665 for the same variable into a single symbol. If they are of
1666 different sizes, it picks the largest size. The linker turns a
1667 common symbol into a declaration, if there is a definition of
1668 the same variable.
1669 The --warn-common option can produce five kinds of warnings. Each
1671 warning consists of a pair of lines: the first describes the symbol
1672 just encountered, and the second describes the previous symbol
1673 encountered with the same name. One or both of the two symbols
1674 will be a common symbol.
1675 1. Turning a common symbol into a reference, because there is
1677 already a definition for the symbol.
1678 <file>(<section>): warning: common of `<symbol>'
1680 overridden by definition
1681 <file>(<section>): warning: defined here
1682 2. Turning a common symbol into a reference, because a later
1684 definition for the symbol is encountered. This is the same as
1685 the previous case, except that the symbols are encountered in a
1686 different order.
1687 <file>(<section>): warning: definition of `<symbol>'
1689 overriding common
1690 <file>(<section>): warning: common is here
1691 3. Merging a common symbol with a previous same-sized common
1693 symbol.
1694 <file>(<section>): warning: multiple common
1696 of `<symbol>'
1697 <file>(<section>): warning: previous common is here
1698 4. Merging a common symbol with a previous larger common symbol.
1700 <file>(<section>): warning: common of `<symbol>'
1702 overridden by larger common
1703 <file>(<section>): warning: larger common is here
1704 5. Merging a common symbol with a previous smaller common symbol.
1706 This is the same as the previous case, except that the symbols
1707 are encountered in a different order.
1708 <file>(<section>): warning: common of `<symbol>'
1710 overriding smaller common
1711 <file>(<section>): warning: smaller common is here
1712 --warn-constructors
1714 Warn if any global constructors are used. This is only useful for
1715 a few object file formats. For formats like COFF or ELF, the
1716 linker can not detect the use of global constructors.
1717 --warn-multiple-gp
1719 Warn if multiple global pointer values are required in the output
1720 file. This is only meaningful for certain processors, such as the
1721 Alpha. Specifically, some processors put large-valued constants in
1722 a special section. A special register (the global pointer) points
1723 into the middle of this section, so that constants can be loaded
1724 efficiently via a base-register relative addressing mode. Since
1725 the offset in base-register relative mode is fixed and relatively
1726 small (e.g., 16 bits), this limits the maximum size of the constant
1727 pool. Thus, in large programs, it is often necessary to use
1728 multiple global pointer values in order to be able to address all
1729 possible constants. This option causes a warning to be issued
1730 whenever this case occurs.
1731 --warn-once
1733 Only warn once for each undefined symbol, rather than once per
1734 module which refers to it.
1735 --warn-section-align
1737 Warn if the address of an output section is changed because of
1738 alignment. Typically, the alignment will be set by an input
1739 section. The address will only be changed if it not explicitly
1740 specified; that is, if the "SECTIONS" command does not specify a
1741 start address for the section.
1742 --warn-shared-textrel
1744 Warn if the linker adds a DT_TEXTREL to a shared object.
1745 --warn-alternate-em
1747 Warn if an object has alternate ELF machine code.
1748 --warn-unresolved-symbols
1750 If the linker is going to report an unresolved symbol (see the
1751 option --unresolved-symbols) it will normally generate an error.
1752 This option makes it generate a warning instead.
1753 --error-unresolved-symbols
1755 This restores the linker's default behaviour of generating errors
1756 when it is reporting unresolved symbols.
1757 --whole-archive
1759 For each archive mentioned on the command line after the
1760 --whole-archive option, include every object file in the archive in
1761 the link, rather than searching the archive for the required object
1762 files. This is normally used to turn an archive file into a shared
1763 library, forcing every object to be included in the resulting
1764 shared library. This option may be used more than once.
1765 Two notes when using this option from gcc: First, gcc doesn't know
1767 about this option, so you have to use -Wl,-whole-archive. Second,
1768 don't forget to use -Wl,-no-whole-archive after your list of
1769 archives, because gcc will add its own list of archives to your
1770 link and you may not want this flag to affect those as well.
1771 --wrap=symbol
1773 Use a wrapper function for symbol. Any undefined reference to
1774 symbol will be resolved to "__wrap_symbol". Any undefined
1775 reference to "__real_symbol" will be resolved to symbol.
1776 This can be used to provide a wrapper for a system function. The
1778 wrapper function should be called "__wrap_symbol". If it wishes to
1779 call the system function, it should call "__real_symbol".
1780 Here is a trivial example:
1782 void *
1784 __wrap_malloc (size_t c)
1785 {
1786 printf ("malloc called with %zu\n", c);
1787 return __real_malloc (c);
1788 }
1789 If you link other code with this file using --wrap malloc, then all
1791 calls to "malloc" will call the function "__wrap_malloc" instead.
1792 The call to "__real_malloc" in "__wrap_malloc" will call the real
1793 "malloc" function.
1794 You may wish to provide a "__real_malloc" function as well, so that
1796 links without the --wrap option will succeed. If you do this, you
1797 should not put the definition of "__real_malloc" in the same file
1798 as "__wrap_malloc"; if you do, the assembler may resolve the call
1799 before the linker has a chance to wrap it to "malloc".
1800 Only undefined references are replaced by the linker. So,
1802 translation unit internal references to symbol are not resolved to
1803 "__wrap_symbol". In the next example, the call to "f" in "g" is
1804 not resolved to "__wrap_f".
1805 int
1807 f (void)
1808 {
1809 return 123;
1810 }
1811 int
1813 g (void)
1814 {
1815 return f();
1816 }
1817 --eh-frame-hdr
1819 --no-eh-frame-hdr
1820 Request (--eh-frame-hdr) or suppress (--no-eh-frame-hdr) the
1821 creation of ".eh_frame_hdr" section and ELF "PT_GNU_EH_FRAME"
1822 segment header.
1823 --no-ld-generated-unwind-info
1825 Request creation of ".eh_frame" unwind info for linker generated
1826 code sections like PLT. This option is on by default if linker
1827 generated unwind info is supported.
1828 --enable-new-dtags
1830 --disable-new-dtags
1831 This linker can create the new dynamic tags in ELF. But the older
1832 ELF systems may not understand them. If you specify
1833 --enable-new-dtags, the new dynamic tags will be created as needed
1834 and older dynamic tags will be omitted. If you specify
1835 --disable-new-dtags, no new dynamic tags will be created. By
1836 default, the new dynamic tags are not created. Note that those
1837 options are only available for ELF systems.
1838 --hash-size=number
1840 Set the default size of the linker's hash tables to a prime number
1841 close to number. Increasing this value can reduce the length of
1842 time it takes the linker to perform its tasks, at the expense of
1843 increasing the linker's memory requirements. Similarly reducing
1844 this value can reduce the memory requirements at the expense of
1845 speed.
1846 --hash-style=style
1848 Set the type of linker's hash table(s). style can be either "sysv"
1849 for classic ELF ".hash" section, "gnu" for new style GNU
1850 ".gnu.hash" section or "both" for both the classic ELF ".hash" and
1851 new style GNU ".gnu.hash" hash tables. The default depends upon
1852 how the linker was configured, but for most Linux based systems it
1853 will be "both".
1854 --compress-debug-sections=none
1856 --compress-debug-sections=zlib
1857 --compress-debug-sections=zlib-gnu
1858 --compress-debug-sections=zlib-gabi
1859 On ELF platforms, these options control how DWARF debug sections
1860 are compressed using zlib.
1861 --compress-debug-sections=none doesn't compress DWARF debug
1863 sections. --compress-debug-sections=zlib-gnu compresses DWARF
1864 debug sections and renames them to begin with .zdebug instead of
1865 .debug. --compress-debug-sections=zlib-gabi also compresses DWARF
1866 debug sections, but rather than renaming them it sets the
1867 SHF_COMPRESSED flag in the sections' headers.
1868 The --compress-debug-sections=zlib option is an alias for
1870 --compress-debug-sections=zlib-gabi.
1871 Note that this option overrides any compression in input debug
1873 sections, so if a binary is linked with
1874 --compress-debug-sections=none for example, then any compressed
1875 debug sections in input files will be uncompressed before they are
1876 copied into the output binary.
1877 The default compression behaviour varies depending upon the target
1879 involved and the configure options used to build the toolchain.
1880 The default can be determined by examining the output from the
1881 linker's --help option.
1882 --reduce-memory-overheads
1884 This option reduces memory requirements at ld runtime, at the
1885 expense of linking speed. This was introduced to select the old
1886 O(n^2) algorithm for link map file generation, rather than the new
1887 O(n) algorithm which uses about 40% more memory for symbol storage.
1888 Another effect of the switch is to set the default hash table size
1890 to 1021, which again saves memory at the cost of lengthening the
1891 linker's run time. This is not done however if the --hash-size
1892 switch has been used.
1893 The --reduce-memory-overheads switch may be also be used to enable
1895 other tradeoffs in future versions of the linker.
1896 --build-id
1898 --build-id=style
1899 Request the creation of a ".note.gnu.build-id" ELF note section or
1900 a ".buildid" COFF section. The contents of the note are unique
1901 bits identifying this linked file. style can be "uuid" to use 128
1902 random bits, "sha1" to use a 160-bit SHA1 hash on the normative
1903 parts of the output contents, "md5" to use a 128-bit MD5 hash on
1904 the normative parts of the output contents, or "0xhexstring" to use
1905 a chosen bit string specified as an even number of hexadecimal
1906 digits ("-" and ":" characters between digit pairs are ignored).
1907 If style is omitted, "sha1" is used.
1908 The "md5" and "sha1" styles produces an identifier that is always
1910 the same in an identical output file, but will be unique among all
1911 nonidentical output files. It is not intended to be compared as a
1912 checksum for the file's contents. A linked file may be changed
1913 later by other tools, but the build ID bit string identifying the
1914 original linked file does not change.
1915 Passing "none" for style disables the setting from any "--build-id"
1917 options earlier on the command line.
1918 The i386 PE linker supports the -shared option, which causes the output
1920 to be a dynamically linked library (DLL) instead of a normal
1921 executable. You should name the output "*.dll" when you use this
1922 option. In addition, the linker fully supports the standard "*.def"
1923 files, which may be specified on the linker command line like an object
1924 file (in fact, it should precede archives it exports symbols from, to
1925 ensure that they get linked in, just like a normal object file).
1926 In addition to the options common to all targets, the i386 PE linker
1928 support additional command-line options that are specific to the i386
1929 PE target. Options that take values may be separated from their values
1930 by either a space or an equals sign.
1931 --add-stdcall-alias
1933 If given, symbols with a stdcall suffix (@nn) will be exported as-
1934 is and also with the suffix stripped. [This option is specific to
1935 the i386 PE targeted port of the linker]
1936 --base-file file
1938 Use file as the name of a file in which to save the base addresses
1939 of all the relocations needed for generating DLLs with dlltool.
1940 [This is an i386 PE specific option]
1941 --dll
1943 Create a DLL instead of a regular executable. You may also use
1944 -shared or specify a "LIBRARY" in a given ".def" file. [This
1945 option is specific to the i386 PE targeted port of the linker]
1946 --enable-long-section-names
1948 --disable-long-section-names
1949 The PE variants of the COFF object format add an extension that
1950 permits the use of section names longer than eight characters, the
1951 normal limit for COFF. By default, these names are only allowed in
1952 object files, as fully-linked executable images do not carry the
1953 COFF string table required to support the longer names. As a GNU
1954 extension, it is possible to allow their use in executable images
1955 as well, or to (probably pointlessly!) disallow it in object
1956 files, by using these two options. Executable images generated
1957 with these long section names are slightly non-standard, carrying
1958 as they do a string table, and may generate confusing output when
1959 examined with non-GNU PE-aware tools, such as file viewers and
1960 dumpers. However, GDB relies on the use of PE long section names
1961 to find Dwarf-2 debug information sections in an executable image
1962 at runtime, and so if neither option is specified on the command-
1963 line, ld will enable long section names, overriding the default and
1964 technically correct behaviour, when it finds the presence of debug
1965 information while linking an executable image and not stripping
1966 symbols. [This option is valid for all PE targeted ports of the
1967 linker]
1968 --enable-stdcall-fixup
1970 --disable-stdcall-fixup
1971 If the link finds a symbol that it cannot resolve, it will attempt
1972 to do "fuzzy linking" by looking for another defined symbol that
1973 differs only in the format of the symbol name (cdecl vs stdcall)
1974 and will resolve that symbol by linking to the match. For example,
1975 the undefined symbol "_foo" might be linked to the function
1976 "_foo@12", or the undefined symbol "_bar@16" might be linked to the
1977 function "_bar". When the linker does this, it prints a warning,
1978 since it normally should have failed to link, but sometimes import
1979 libraries generated from third-party dlls may need this feature to
1980 be usable. If you specify --enable-stdcall-fixup, this feature is
1981 fully enabled and warnings are not printed. If you specify
1982 --disable-stdcall-fixup, this feature is disabled and such
1983 mismatches are considered to be errors. [This option is specific
1984 to the i386 PE targeted port of the linker]
1985 --leading-underscore
1987 --no-leading-underscore
1988 For most targets default symbol-prefix is an underscore and is
1989 defined in target's description. By this option it is possible to
1990 disable/enable the default underscore symbol-prefix.
1991 --export-all-symbols
1993 If given, all global symbols in the objects used to build a DLL
1994 will be exported by the DLL. Note that this is the default if
1995 there otherwise wouldn't be any exported symbols. When symbols are
1996 explicitly exported via DEF files or implicitly exported via
1997 function attributes, the default is to not export anything else
1998 unless this option is given. Note that the symbols "DllMain@12",
1999 "DllEntryPoint@0", "DllMainCRTStartup@12", and "impure_ptr" will
2000 not be automatically exported. Also, symbols imported from other
2001 DLLs will not be re-exported, nor will symbols specifying the DLL's
2002 internal layout such as those beginning with "_head_" or ending
2003 with "_iname". In addition, no symbols from "libgcc", "libstd++",
2004 "libmingw32", or "crtX.o" will be exported. Symbols whose names
2005 begin with "__rtti_" or "__builtin_" will not be exported, to help
2006 with C++ DLLs. Finally, there is an extensive list of cygwin-
2007 private symbols that are not exported (obviously, this applies on
2008 when building DLLs for cygwin targets). These cygwin-excludes are:
2009 "_cygwin_dll_entry@12", "_cygwin_crt0_common@8",
2010 "_cygwin_noncygwin_dll_entry@12", "_fmode", "_impure_ptr",
2011 "cygwin_attach_dll", "cygwin_premain0", "cygwin_premain1",
2012 "cygwin_premain2", "cygwin_premain3", and "environ". [This option
2013 is specific to the i386 PE targeted port of the linker]
2014 --exclude-symbols symbol,symbol,...
2016 Specifies a list of symbols which should not be automatically
2017 exported. The symbol names may be delimited by commas or colons.
2018 [This option is specific to the i386 PE targeted port of the
2019 linker]
2020 --exclude-all-symbols
2022 Specifies no symbols should be automatically exported. [This
2023 option is specific to the i386 PE targeted port of the linker]
2024 --file-alignment
2026 Specify the file alignment. Sections in the file will always begin
2027 at file offsets which are multiples of this number. This defaults
2028 to 512. [This option is specific to the i386 PE targeted port of
2029 the linker]
2030 --heap reserve
2032 --heap reserve,commit
2033 Specify the number of bytes of memory to reserve (and optionally
2034 commit) to be used as heap for this program. The default is 1MB
2035 reserved, 4K committed. [This option is specific to the i386 PE
2036 targeted port of the linker]
2037 --image-base value
2039 Use value as the base address of your program or dll. This is the
2040 lowest memory location that will be used when your program or dll
2041 is loaded. To reduce the need to relocate and improve performance
2042 of your dlls, each should have a unique base address and not
2043 overlap any other dlls. The default is 0x400000 for executables,
2044 and 0x10000000 for dlls. [This option is specific to the i386 PE
2045 targeted port of the linker]
2046 --kill-at
2048 If given, the stdcall suffixes (@nn) will be stripped from symbols
2049 before they are exported. [This option is specific to the i386 PE
2050 targeted port of the linker]
2051 --large-address-aware
2053 If given, the appropriate bit in the "Characteristics" field of the
2054 COFF header is set to indicate that this executable supports
2055 virtual addresses greater than 2 gigabytes. This should be used in
2056 conjunction with the /3GB or /USERVA=value megabytes switch in the
2057 "[operating systems]" section of the BOOT.INI. Otherwise, this bit
2058 has no effect. [This option is specific to PE targeted ports of
2059 the linker]
2060 --disable-large-address-aware
2062 Reverts the effect of a previous --large-address-aware option.
2063 This is useful if --large-address-aware is always set by the
2064 compiler driver (e.g. Cygwin gcc) and the executable does not
2065 support virtual addresses greater than 2 gigabytes. [This option
2066 is specific to PE targeted ports of the linker]
2067 --major-image-version value
2069 Sets the major number of the "image version". Defaults to 1.
2070 [This option is specific to the i386 PE targeted port of the
2071 linker]
2072 --major-os-version value
2074 Sets the major number of the "os version". Defaults to 4. [This
2075 option is specific to the i386 PE targeted port of the linker]
2076 --major-subsystem-version value
2078 Sets the major number of the "subsystem version". Defaults to 4.
2079 [This option is specific to the i386 PE targeted port of the
2080 linker]
2081 --minor-image-version value
2083 Sets the minor number of the "image version". Defaults to 0.
2084 [This option is specific to the i386 PE targeted port of the
2085 linker]
2086 --minor-os-version value
2088 Sets the minor number of the "os version". Defaults to 0. [This
2089 option is specific to the i386 PE targeted port of the linker]
2090 --minor-subsystem-version value
2092 Sets the minor number of the "subsystem version". Defaults to 0.
2093 [This option is specific to the i386 PE targeted port of the
2094 linker]
2095 --output-def file
2097 The linker will create the file file which will contain a DEF file
2098 corresponding to the DLL the linker is generating. This DEF file
2099 (which should be called "*.def") may be used to create an import
2100 library with "dlltool" or may be used as a reference to
2101 automatically or implicitly exported symbols. [This option is
2102 specific to the i386 PE targeted port of the linker]
2103 --enable-auto-image-base
2105 --enable-auto-image-base=value
2106 Automatically choose the image base for DLLs, optionally starting
2107 with base value, unless one is specified using the "--image-base"
2108 argument. By using a hash generated from the dllname to create
2109 unique image bases for each DLL, in-memory collisions and
2110 relocations which can delay program execution are avoided. [This
2111 option is specific to the i386 PE targeted port of the linker]
2112 --disable-auto-image-base
2114 Do not automatically generate a unique image base. If there is no
2115 user-specified image base ("--image-base") then use the platform
2116 default. [This option is specific to the i386 PE targeted port of
2117 the linker]
2118 --dll-search-prefix string
2120 When linking dynamically to a dll without an import library, search
2121 for "<string><basename>.dll" in preference to "lib<basename>.dll".
2122 This behaviour allows easy distinction between DLLs built for the
2123 various "subplatforms": native, cygwin, uwin, pw, etc. For
2124 instance, cygwin DLLs typically use "--dll-search-prefix=cyg".
2125 [This option is specific to the i386 PE targeted port of the
2126 linker]
2127 --enable-auto-import
2129 Do sophisticated linking of "_symbol" to "__imp__symbol" for DATA
2130 imports from DLLs, thus making it possible to bypass the dllimport
2131 mechanism on the user side and to reference unmangled symbol names.
2132 [This option is specific to the i386 PE targeted port of the
2133 linker]
2134 The following remarks pertain to the original implementation of the
2136 feature and are obsolete nowadays for Cygwin and MinGW targets.
2137 Note: Use of the 'auto-import' extension will cause the text
2139 section of the image file to be made writable. This does not
2140 conform to the PE-COFF format specification published by Microsoft.
2141 Note - use of the 'auto-import' extension will also cause read only
2143 data which would normally be placed into the .rdata section to be
2144 placed into the .data section instead. This is in order to work
2145 around a problem with consts that is described here:
2146 http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
2147 Using 'auto-import' generally will 'just work' -- but sometimes you
2149 may see this message:
2150 "variable '<var>' can't be auto-imported. Please read the
2152 documentation for ld's "--enable-auto-import" for details."
2153 This message occurs when some (sub)expression accesses an address
2155 ultimately given by the sum of two constants (Win32 import tables
2156 only allow one). Instances where this may occur include accesses
2157 to member fields of struct variables imported from a DLL, as well
2158 as using a constant index into an array variable imported from a
2159 DLL. Any multiword variable (arrays, structs, long long, etc) may
2160 trigger this error condition. However, regardless of the exact
2161 data type of the offending exported variable, ld will always detect
2162 it, issue the warning, and exit.
2163 There are several ways to address this difficulty, regardless of
2165 the data type of the exported variable:
2166 One way is to use --enable-runtime-pseudo-reloc switch. This leaves
2168 the task of adjusting references in your client code for runtime
2169 environment, so this method works only when runtime environment
2170 supports this feature.
2171 A second solution is to force one of the 'constants' to be a
2173 variable -- that is, unknown and un-optimizable at compile time.
2174 For arrays, there are two possibilities: a) make the indexee (the
2175 array's address) a variable, or b) make the 'constant' index a
2176 variable. Thus:
2177 extern type extern_array[];
2179 extern_array[1] -->
2180 { volatile type *t=extern_array; t[1] }
2181 or
2183 extern type extern_array[];
2185 extern_array[1] -->
2186 { volatile int t=1; extern_array[t] }
2187 For structs (and most other multiword data types) the only option
2189 is to make the struct itself (or the long long, or the ...)
2190 variable:
2191 extern struct s extern_struct;
2193 extern_struct.field -->
2194 { volatile struct s *t=&extern_struct; t->field }
2195 or
2197 extern long long extern_ll;
2199 extern_ll -->
2200 { volatile long long * local_ll=&extern_ll; *local_ll }
2201 A third method of dealing with this difficulty is to abandon
2203 'auto-import' for the offending symbol and mark it with
2204 "__declspec(dllimport)". However, in practice that requires using
2205 compile-time #defines to indicate whether you are building a DLL,
2206 building client code that will link to the DLL, or merely
2207 building/linking to a static library. In making the choice
2208 between the various methods of resolving the 'direct address with
2209 constant offset' problem, you should consider typical real-world
2210 usage:
2211 Original:
2213 --foo.h
2215 extern int arr[];
2216 --foo.c
2217 #include "foo.h"
2218 void main(int argc, char **argv){
2219 printf("%d\n",arr[1]);
2220 }
2221 Solution 1:
2223 --foo.h
2225 extern int arr[];
2226 --foo.c
2227 #include "foo.h"
2228 void main(int argc, char **argv){
2229 /* This workaround is for win32 and cygwin; do not "optimize" */
2230 volatile int *parr = arr;
2231 printf("%d\n",parr[1]);
2232 }
2233 Solution 2:
2235 --foo.h
2237 /* Note: auto-export is assumed (no __declspec(dllexport)) */
2238 #if (defined(_WIN32) || defined(__CYGWIN__)) && \
2239 !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
2240 #define FOO_IMPORT __declspec(dllimport)
2241 #else
2242 #define FOO_IMPORT
2243 #endif
2244 extern FOO_IMPORT int arr[];
2245 --foo.c
2246 #include "foo.h"
2247 void main(int argc, char **argv){
2248 printf("%d\n",arr[1]);
2249 }
2250 A fourth way to avoid this problem is to re-code your library to
2252 use a functional interface rather than a data interface for the
2253 offending variables (e.g. set_foo() and get_foo() accessor
2254 functions).
2255 --disable-auto-import
2257 Do not attempt to do sophisticated linking of "_symbol" to
2258 "__imp__symbol" for DATA imports from DLLs. [This option is
2259 specific to the i386 PE targeted port of the linker]
2260 --enable-runtime-pseudo-reloc
2262 If your code contains expressions described in --enable-auto-import
2263 section, that is, DATA imports from DLL with non-zero offset, this
2264 switch will create a vector of 'runtime pseudo relocations' which
2265 can be used by runtime environment to adjust references to such
2266 data in your client code. [This option is specific to the i386 PE
2267 targeted port of the linker]
2268 --disable-runtime-pseudo-reloc
2270 Do not create pseudo relocations for non-zero offset DATA imports
2271 from DLLs. [This option is specific to the i386 PE targeted port
2272 of the linker]
2273 --enable-extra-pe-debug
2275 Show additional debug info related to auto-import symbol thunking.
2276 [This option is specific to the i386 PE targeted port of the
2277 linker]
2278 --section-alignment
2280 Sets the section alignment. Sections in memory will always begin
2281 at addresses which are a multiple of this number. Defaults to
2282 0x1000. [This option is specific to the i386 PE targeted port of
2283 the linker]
2284 --stack reserve
2286 --stack reserve,commit
2287 Specify the number of bytes of memory to reserve (and optionally
2288 commit) to be used as stack for this program. The default is 2MB
2289 reserved, 4K committed. [This option is specific to the i386 PE
2290 targeted port of the linker]
2291 --subsystem which
2293 --subsystem which:major
2294 --subsystem which:major.minor
2295 Specifies the subsystem under which your program will execute. The
2296 legal values for which are "native", "windows", "console", "posix",
2297 and "xbox". You may optionally set the subsystem version also.
2298 Numeric values are also accepted for which. [This option is
2299 specific to the i386 PE targeted port of the linker]
2300 The following options set flags in the "DllCharacteristics" field
2302 of the PE file header: [These options are specific to PE targeted
2303 ports of the linker]
2304 --high-entropy-va
2306 Image is compatible with 64-bit address space layout randomization
2307 (ASLR).
2308 --dynamicbase
2310 The image base address may be relocated using address space layout
2311 randomization (ASLR). This feature was introduced with MS Windows
2312 Vista for i386 PE targets.
2313 --forceinteg
2315 Code integrity checks are enforced.
2316 --nxcompat
2318 The image is compatible with the Data Execution Prevention. This
2319 feature was introduced with MS Windows XP SP2 for i386 PE targets.
2320 --no-isolation
2322 Although the image understands isolation, do not isolate the image.
2323 --no-seh
2325 The image does not use SEH. No SE handler may be called from this
2326 image.
2327 --no-bind
2329 Do not bind this image.
2330 --wdmdriver
2332 The driver uses the MS Windows Driver Model.
2333 --tsaware
2335 The image is Terminal Server aware.
2336 --insert-timestamp
2338 --no-insert-timestamp
2339 Insert a real timestamp into the image. This is the default
2340 behaviour as it matches legacy code and it means that the image
2341 will work with other, proprietary tools. The problem with this
2342 default is that it will result in slightly different images being
2343 produced each time the same sources are linked. The option
2344 --no-insert-timestamp can be used to insert a zero value for the
2345 timestamp, this ensuring that binaries produced from identical
2346 sources will compare identically.
2347 The C6X uClinux target uses a binary format called DSBT to support
2349 shared libraries. Each shared library in the system needs to have a
2350 unique index; all executables use an index of 0.
2351 --dsbt-size size
2353 This option sets the number of entries in the DSBT of the current
2354 executable or shared library to size. The default is to create a
2355 table with 64 entries.
2356 --dsbt-index index
2358 This option sets the DSBT index of the current executable or shared
2359 library to index. The default is 0, which is appropriate for
2360 generating executables. If a shared library is generated with a
2361 DSBT index of 0, the "R_C6000_DSBT_INDEX" relocs are copied into
2362 the output file.
2363 The --no-merge-exidx-entries switch disables the merging of
2365 adjacent exidx entries in frame unwind info.
2366 --branch-stub
2368 This option enables linker branch relaxation by inserting branch
2369 stub sections when needed to extend the range of branches. This
2370 option is usually not required since C-SKY supports branch and call
2371 instructions that can access the full memory range and branch
2372 relaxation is normally handled by the compiler or assembler.
2373 --stub-group-size=N
2375 This option allows finer control of linker branch stub creation.
2376 It sets the maximum size of a group of input sections that can be
2377 handled by one stub section. A negative value of N locates stub
2378 sections after their branches, while a positive value allows stub
2379 sections to appear either before or after the branches. Values of
2380 1 or -1 indicate that the linker should choose suitable defaults.
2381 The 68HC11 and 68HC12 linkers support specific options to control the
2383 memory bank switching mapping and trampoline code generation.
2384 --no-trampoline
2386 This option disables the generation of trampoline. By default a
2387 trampoline is generated for each far function which is called using
2388 a "jsr" instruction (this happens when a pointer to a far function
2389 is taken).
2390 --bank-window name
2392 This option indicates to the linker the name of the memory region
2393 in the MEMORY specification that describes the memory bank window.
2394 The definition of such region is then used by the linker to compute
2395 paging and addresses within the memory window.
2396 The following options are supported to control handling of GOT
2398 generation when linking for 68K targets.
2399 --got=type
2401 This option tells the linker which GOT generation scheme to use.
2402 type should be one of single, negative, multigot or target. For
2403 more information refer to the Info entry for ld.
2404 The following options are supported to control microMIPS instruction
2406 generation and branch relocation checks for ISA mode transitions when
2407 linking for MIPS targets.
2408 --insn32
2410 --no-insn32
2411 These options control the choice of microMIPS instructions used in
2412 code generated by the linker, such as that in the PLT or lazy
2413 binding stubs, or in relaxation. If --insn32 is used, then the
2414 linker only uses 32-bit instruction encodings. By default or if
2415 --no-insn32 is used, all instruction encodings are used, including
2416 16-bit ones where possible.
2417 --ignore-branch-isa
2419 --no-ignore-branch-isa
2420 These options control branch relocation checks for invalid ISA mode
2421 transitions. If --ignore-branch-isa is used, then the linker
2422 accepts any branch relocations and any ISA mode transition required
2423 is lost in relocation calculation, except for some cases of "BAL"
2424 instructions which meet relaxation conditions and are converted to
2425 equivalent "JALX" instructions as the associated relocation is
2426 calculated. By default or if --no-ignore-branch-isa is used a
2427 check is made causing the loss of an ISA mode transition to produce
2428 an error.
2429
2431 You can change the behaviour of ld with the environment variables
2432 "GNUTARGET", "LDEMULATION" and "COLLECT_NO_DEMANGLE".
2433 "GNUTARGET" determines the input-file object format if you don't use -b
2435 (or its synonym --format). Its value should be one of the BFD names
2436 for an input format. If there is no "GNUTARGET" in the environment, ld
2437 uses the natural format of the target. If "GNUTARGET" is set to
2438 "default" then BFD attempts to discover the input format by examining
2439 binary input files; this method often succeeds, but there are potential
2440 ambiguities, since there is no method of ensuring that the magic number
2441 used to specify object-file formats is unique. However, the
2442 configuration procedure for BFD on each system places the conventional
2443 format for that system first in the search-list, so ambiguities are
2444 resolved in favor of convention.
2445 "LDEMULATION" determines the default emulation if you don't use the -m
2447 option. The emulation can affect various aspects of linker behaviour,
2448 particularly the default linker script. You can list the available
2449 emulations with the --verbose or -V options. If the -m option is not
2450 used, and the "LDEMULATION" environment variable is not defined, the
2451 default emulation depends upon how the linker was configured.
2452 Normally, the linker will default to demangling symbols. However, if
2454 "COLLECT_NO_DEMANGLE" is set in the environment, then it will default
2455 to not demangling symbols. This environment variable is used in a
2456 similar fashion by the "gcc" linker wrapper program. The default may
2457 be overridden by the --demangle and --no-demangle options.
2458
2460 ar(1), nm(1), objcopy(1), objdump(1), readelf(1) and the Info entries
2461 for binutils and ld.
2462
2464 Copyright (c) 1991-2019 Free Software Foundation, Inc.
2465 Permission is granted to copy, distribute and/or modify this document
2467 under the terms of the GNU Free Documentation License, Version 1.3 or
2468 any later version published by the Free Software Foundation; with no
2469 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
2470 Texts. A copy of the license is included in the section entitled "GNU
2471 Free Documentation License".
2472binutils-2.32 2019-02-02 LD(1)