1LD(1) GNU Development Tools LD(1)
2
6 ld - The GNU linker
7
9 ld [options] objfile ...
10
12 ld combines a number of object and archive files, relocates their data
13 and ties up symbol references. Usually the last step in compiling a
14 program is to run ld.
15 ld accepts Linker Command Language files written in a superset of
17 AT&T's Link Editor Command Language syntax, to provide explicit and
18 total control over the linking process.
19 This man page does not describe the command language; see the ld entry
21 in "info" for full details on the command language and on other aspects
22 of the GNU linker.
23 This version of ld uses the general purpose BFD libraries to operate on
25 object files. This allows ld to read, combine, and write object files
26 in many different formats---for example, COFF or "a.out". Different
27 formats may be linked together to produce any available kind of object
28 file.
29 Aside from its flexibility, the GNU linker is more helpful than other
31 linkers in providing diagnostic information. Many linkers abandon
32 execution immediately upon encountering an error; whenever possible, ld
33 continues executing, allowing you to identify other errors (or, in some
34 cases, to get an output file in spite of the error).
35 The GNU linker ld is meant to cover a broad range of situations, and to
37 be as compatible as possible with other linkers. As a result, you have
38 many choices to control its behavior.
39
41 The linker supports a plethora of command-line options, but in actual
42 practice few of them are used in any particular context. For instance,
43 a frequent use of ld is to link standard Unix object files on a
44 standard, supported Unix system. On such a system, to link a file
45 "hello.o":
46 ld -o <output> /lib/crt0.o hello.o -lc
48 This tells ld to produce a file called output as the result of linking
50 the file "/lib/crt0.o" with "hello.o" and the library "libc.a", which
51 will come from the standard search directories. (See the discussion of
52 the -l option below.)
53 Some of the command-line options to ld may be specified at any point in
55 the command line. However, options which refer to files, such as -l or
56 -T, cause the file to be read at the point at which the option appears
57 in the command line, relative to the object files and other file
58 options. Repeating non-file options with a different argument will
59 either have no further effect, or override prior occurrences (those
60 further to the left on the command line) of that option. Options which
61 may be meaningfully specified more than once are noted in the
62 descriptions below.
63 Non-option arguments are object files or archives which are to be
65 linked together. They may follow, precede, or be mixed in with
66 command-line options, except that an object file argument may not be
67 placed between an option and its argument.
68 Usually the linker is invoked with at least one object file, but you
70 can specify other forms of binary input files using -l, -R, and the
71 script command language. If no binary input files at all are
72 specified, the linker does not produce any output, and issues the
73 message No input files.
74 If the linker cannot recognize the format of an object file, it will
76 assume that it is a linker script. A script specified in this way
77 augments the main linker script used for the link (either the default
78 linker script or the one specified by using -T). This feature permits
79 the linker to link against a file which appears to be an object or an
80 archive, but actually merely defines some symbol values, or uses
81 "INPUT" or "GROUP" to load other objects. Specifying a script in this
82 way merely augments the main linker script, with the extra commands
83 placed after the main script; use the -T option to replace the default
84 linker script entirely, but note the effect of the "INSERT" command.
85 For options whose names are a single letter, option arguments must
87 either follow the option letter without intervening whitespace, or be
88 given as separate arguments immediately following the option that
89 requires them.
90 For options whose names are multiple letters, either one dash or two
92 can precede the option name; for example, -trace-symbol and
93 --trace-symbol are equivalent. Note---there is one exception to this
94 rule. Multiple letter options that start with a lower case 'o' can
95 only be preceded by two dashes. This is to reduce confusion with the
96 -o option. So for example -omagic sets the output file name to magic
97 whereas --omagic sets the NMAGIC flag on the output.
98 Arguments to multiple-letter options must either be separated from the
100 option name by an equals sign, or be given as separate arguments
101 immediately following the option that requires them. For example,
102 --trace-symbol foo and --trace-symbol=foo are equivalent. Unique
103 abbreviations of the names of multiple-letter options are accepted.
104 Note---if the linker is being invoked indirectly, via a compiler driver
106 (e.g. gcc) then all the linker command-line options should be prefixed
107 by -Wl, (or whatever is appropriate for the particular compiler driver)
108 like this:
109 gcc -Wl,--start-group foo.o bar.o -Wl,--end-group
111 This is important, because otherwise the compiler driver program may
113 silently drop the linker options, resulting in a bad link. Confusion
114 may also arise when passing options that require values through a
115 driver, as the use of a space between option and argument acts as a
116 separator, and causes the driver to pass only the option to the linker
117 and the argument to the compiler. In this case, it is simplest to use
118 the joined forms of both single- and multiple-letter options, such as:
119 gcc foo.o bar.o -Wl,-eENTRY -Wl,-Map=a.map
121 Here is a table of the generic command-line switches accepted by the
123 GNU linker:
124 @file
126 Read command-line options from file. The options read are inserted
127 in place of the original @file option. If file does not exist, or
128 cannot be read, then the option will be treated literally, and not
129 removed.
130 Options in file are separated by whitespace. A whitespace
132 character may be included in an option by surrounding the entire
133 option in either single or double quotes. Any character (including
134 a backslash) may be included by prefixing the character to be
135 included with a backslash. The file may itself contain additional
136 @file options; any such options will be processed recursively.
137 -a keyword
139 This option is supported for HP/UX compatibility. The keyword
140 argument must be one of the strings archive, shared, or default.
141 -aarchive is functionally equivalent to -Bstatic, and the other two
142 keywords are functionally equivalent to -Bdynamic. This option may
143 be used any number of times.
144 --audit AUDITLIB
146 Adds AUDITLIB to the "DT_AUDIT" entry of the dynamic section.
147 AUDITLIB is not checked for existence, nor will it use the
148 DT_SONAME specified in the library. If specified multiple times
149 "DT_AUDIT" will contain a colon separated list of audit interfaces
150 to use. If the linker finds an object with an audit entry while
151 searching for shared libraries, it will add a corresponding
152 "DT_DEPAUDIT" entry in the output file. This option is only
153 meaningful on ELF platforms supporting the rtld-audit interface.
154 -b input-format
156 --format=input-format
157 ld may be configured to support more than one kind of object file.
158 If your ld is configured this way, you can use the -b option to
159 specify the binary format for input object files that follow this
160 option on the command line. Even when ld is configured to support
161 alternative object formats, you don't usually need to specify this,
162 as ld should be configured to expect as a default input format the
163 most usual format on each machine. input-format is a text string,
164 the name of a particular format supported by the BFD libraries.
165 (You can list the available binary formats with objdump -i.)
166 You may want to use this option if you are linking files with an
168 unusual binary format. You can also use -b to switch formats
169 explicitly (when linking object files of different formats), by
170 including -b input-format before each group of object files in a
171 particular format.
172 The default format is taken from the environment variable
174 "GNUTARGET".
175 You can also define the input format from a script, using the
177 command "TARGET";
178 -c MRI-commandfile
180 --mri-script=MRI-commandfile
181 For compatibility with linkers produced by MRI, ld accepts script
182 files written in an alternate, restricted command language,
183 described in the MRI Compatible Script Files section of GNU ld
184 documentation. Introduce MRI script files with the option -c; use
185 the -T option to run linker scripts written in the general-purpose
186 ld scripting language. If MRI-cmdfile does not exist, ld looks for
187 it in the directories specified by any -L options.
188 -d
190 -dc
191 -dp These three options are equivalent; multiple forms are supported
192 for compatibility with other linkers. They assign space to common
193 symbols even if a relocatable output file is specified (with -r).
194 The script command "FORCE_COMMON_ALLOCATION" has the same effect.
195 --depaudit AUDITLIB
197 -P AUDITLIB
198 Adds AUDITLIB to the "DT_DEPAUDIT" entry of the dynamic section.
199 AUDITLIB is not checked for existence, nor will it use the
200 DT_SONAME specified in the library. If specified multiple times
201 "DT_DEPAUDIT" will contain a colon separated list of audit
202 interfaces to use. This option is only meaningful on ELF platforms
203 supporting the rtld-audit interface. The -P option is provided for
204 Solaris compatibility.
205 --enable-non-contiguous-regions
207 This option avoids generating an error if an input section does not
208 fit a matching output section. The linker tries to allocate the
209 input section to subseque nt matching output sections, and
210 generates an error only if no output section is large enough. This
211 is useful when several non-contiguous memory regions are available
212 and the input section does not require a particular one. The order
213 in which input sections are evaluated does not change, for
214 instance:
215 MEMORY {
217 MEM1 (rwx) : ORIGIN : 0x1000, LENGTH = 0x14
218 MEM2 (rwx) : ORIGIN : 0x1000, LENGTH = 0x40
219 MEM3 (rwx) : ORIGIN : 0x2000, LENGTH = 0x40
220 }
221 SECTIONS {
222 mem1 : { *(.data.*); } > MEM1
223 mem2 : { *(.data.*); } > MEM2
224 mem3 : { *(.data.*); } > MEM2
225 }
226 with input sections:
228 .data.1: size 8
229 .data.2: size 0x10
230 .data.3: size 4
231 results in .data.1 affected to mem1, and .data.2 and .data.3
233 affected to mem2, even though .data.3 would fit in mem3.
234 This option is incompatible with INSERT statements because it
236 changes the way input sections are mapped to output sections.
237 --enable-non-contiguous-regions-warnings
239 This option enables warnings when "--enable-non-contiguous-regions"
240 allows possibly unexpected matches in sections mapping, potentially
241 leading to silently discarding a section instead of failing because
242 it does not fit any output region.
243 -e entry
245 --entry=entry
246 Use entry as the explicit symbol for beginning execution of your
247 program, rather than the default entry point. If there is no
248 symbol named entry, the linker will try to parse entry as a number,
249 and use that as the entry address (the number will be interpreted
250 in base 10; you may use a leading 0x for base 16, or a leading 0
251 for base 8).
252 --exclude-libs lib,lib,...
254 Specifies a list of archive libraries from which symbols should not
255 be automatically exported. The library names may be delimited by
256 commas or colons. Specifying "--exclude-libs ALL" excludes symbols
257 in all archive libraries from automatic export. This option is
258 available only for the i386 PE targeted port of the linker and for
259 ELF targeted ports. For i386 PE, symbols explicitly listed in a
260 .def file are still exported, regardless of this option. For ELF
261 targeted ports, symbols affected by this option will be treated as
262 hidden.
263 --exclude-modules-for-implib module,module,...
265 Specifies a list of object files or archive members, from which
266 symbols should not be automatically exported, but which should be
267 copied wholesale into the import library being generated during the
268 link. The module names may be delimited by commas or colons, and
269 must match exactly the filenames used by ld to open the files; for
270 archive members, this is simply the member name, but for object
271 files the name listed must include and match precisely any path
272 used to specify the input file on the linker's command-line. This
273 option is available only for the i386 PE targeted port of the
274 linker. Symbols explicitly listed in a .def file are still
275 exported, regardless of this option.
276 -E
278 --export-dynamic
279 --no-export-dynamic
280 When creating a dynamically linked executable, using the -E option
281 or the --export-dynamic option causes the linker to add all symbols
282 to the dynamic symbol table. The dynamic symbol table is the set
283 of symbols which are visible from dynamic objects at run time.
284 If you do not use either of these options (or use the
286 --no-export-dynamic option to restore the default behavior), the
287 dynamic symbol table will normally contain only those symbols which
288 are referenced by some dynamic object mentioned in the link.
289 If you use "dlopen" to load a dynamic object which needs to refer
291 back to the symbols defined by the program, rather than some other
292 dynamic object, then you will probably need to use this option when
293 linking the program itself.
294 You can also use the dynamic list to control what symbols should be
296 added to the dynamic symbol table if the output format supports it.
297 See the description of --dynamic-list.
298 Note that this option is specific to ELF targeted ports. PE
300 targets support a similar function to export all symbols from a DLL
301 or EXE; see the description of --export-all-symbols below.
302 --export-dynamic-symbol=glob
304 When creating a dynamically linked executable, symbols matching
305 glob will be added to the dynamic symbol table. When creating a
306 shared library, references to symbols matching glob will not be
307 bound to the definitions within the shared library. This option is
308 a no-op when creating a shared library and -Bsymbolic or
309 --dynamic-list are not specified. This option is only meaningful on
310 ELF platforms which support shared libraries.
311 --export-dynamic-symbol-list=file
313 Specify a --export-dynamic-symbol for each pattern in the file.
314 The format of the file is the same as the version node without
315 scope and node name. See VERSION for more information.
316 -EB Link big-endian objects. This affects the default output format.
318 -EL Link little-endian objects. This affects the default output
320 format.
321 -f name
323 --auxiliary=name
324 When creating an ELF shared object, set the internal DT_AUXILIARY
325 field to the specified name. This tells the dynamic linker that
326 the symbol table of the shared object should be used as an
327 auxiliary filter on the symbol table of the shared object name.
328 If you later link a program against this filter object, then, when
330 you run the program, the dynamic linker will see the DT_AUXILIARY
331 field. If the dynamic linker resolves any symbols from the filter
332 object, it will first check whether there is a definition in the
333 shared object name. If there is one, it will be used instead of
334 the definition in the filter object. The shared object name need
335 not exist. Thus the shared object name may be used to provide an
336 alternative implementation of certain functions, perhaps for
337 debugging or for machine-specific performance.
338 This option may be specified more than once. The DT_AUXILIARY
340 entries will be created in the order in which they appear on the
341 command line.
342 -F name
344 --filter=name
345 When creating an ELF shared object, set the internal DT_FILTER
346 field to the specified name. This tells the dynamic linker that
347 the symbol table of the shared object which is being created should
348 be used as a filter on the symbol table of the shared object name.
349 If you later link a program against this filter object, then, when
351 you run the program, the dynamic linker will see the DT_FILTER
352 field. The dynamic linker will resolve symbols according to the
353 symbol table of the filter object as usual, but it will actually
354 link to the definitions found in the shared object name. Thus the
355 filter object can be used to select a subset of the symbols
356 provided by the object name.
357 Some older linkers used the -F option throughout a compilation
359 toolchain for specifying object-file format for both input and
360 output object files. The GNU linker uses other mechanisms for this
361 purpose: the -b, --format, --oformat options, the "TARGET" command
362 in linker scripts, and the "GNUTARGET" environment variable. The
363 GNU linker will ignore the -F option when not creating an ELF
364 shared object.
365 -fini=name
367 When creating an ELF executable or shared object, call NAME when
368 the executable or shared object is unloaded, by setting DT_FINI to
369 the address of the function. By default, the linker uses "_fini"
370 as the function to call.
371 -g Ignored. Provided for compatibility with other tools.
373 -G value
375 --gpsize=value
376 Set the maximum size of objects to be optimized using the GP
377 register to size. This is only meaningful for object file formats
378 such as MIPS ELF that support putting large and small objects into
379 different sections. This is ignored for other object file formats.
380 -h name
382 -soname=name
383 When creating an ELF shared object, set the internal DT_SONAME
384 field to the specified name. When an executable is linked with a
385 shared object which has a DT_SONAME field, then when the executable
386 is run the dynamic linker will attempt to load the shared object
387 specified by the DT_SONAME field rather than using the file name
388 given to the linker.
389 -i Perform an incremental link (same as option -r).
391 -init=name
393 When creating an ELF executable or shared object, call NAME when
394 the executable or shared object is loaded, by setting DT_INIT to
395 the address of the function. By default, the linker uses "_init"
396 as the function to call.
397 -l namespec
399 --library=namespec
400 Add the archive or object file specified by namespec to the list of
401 files to link. This option may be used any number of times. If
402 namespec is of the form :filename, ld will search the library path
403 for a file called filename, otherwise it will search the library
404 path for a file called libnamespec.a.
405 On systems which support shared libraries, ld may also search for
407 files other than libnamespec.a. Specifically, on ELF and SunOS
408 systems, ld will search a directory for a library called
409 libnamespec.so before searching for one called libnamespec.a. (By
410 convention, a ".so" extension indicates a shared library.) Note
411 that this behavior does not apply to :filename, which always
412 specifies a file called filename.
413 The linker will search an archive only once, at the location where
415 it is specified on the command line. If the archive defines a
416 symbol which was undefined in some object which appeared before the
417 archive on the command line, the linker will include the
418 appropriate file(s) from the archive. However, an undefined symbol
419 in an object appearing later on the command line will not cause the
420 linker to search the archive again.
421 See the -( option for a way to force the linker to search archives
423 multiple times.
424 You may list the same archive multiple times on the command line.
426 This type of archive searching is standard for Unix linkers.
428 However, if you are using ld on AIX, note that it is different from
429 the behaviour of the AIX linker.
430 -L searchdir
432 --library-path=searchdir
433 Add path searchdir to the list of paths that ld will search for
434 archive libraries and ld control scripts. You may use this option
435 any number of times. The directories are searched in the order in
436 which they are specified on the command line. Directories
437 specified on the command line are searched before the default
438 directories. All -L options apply to all -l options, regardless of
439 the order in which the options appear. -L options do not affect
440 how ld searches for a linker script unless -T option is specified.
441 If searchdir begins with "=" or $SYSROOT, then this prefix will be
443 replaced by the sysroot prefix, controlled by the --sysroot option,
444 or specified when the linker is configured.
445 The default set of paths searched (without being specified with -L)
447 depends on which emulation mode ld is using, and in some cases also
448 on how it was configured.
449 The paths can also be specified in a link script with the
451 "SEARCH_DIR" command. Directories specified this way are searched
452 at the point in which the linker script appears in the command
453 line.
454 -m emulation
456 Emulate the emulation linker. You can list the available
457 emulations with the --verbose or -V options.
458 If the -m option is not used, the emulation is taken from the
460 "LDEMULATION" environment variable, if that is defined.
461 Otherwise, the default emulation depends upon how the linker was
463 configured.
464 -M
466 --print-map
467 Print a link map to the standard output. A link map provides
468 information about the link, including the following:
469 • Where object files are mapped into memory.
471 • How common symbols are allocated.
473 • All archive members included in the link, with a mention of the
475 symbol which caused the archive member to be brought in.
476 • The values assigned to symbols.
478 Note - symbols whose values are computed by an expression which
480 involves a reference to a previous value of the same symbol may
481 not have correct result displayed in the link map. This is
482 because the linker discards intermediate results and only
483 retains the final value of an expression. Under such
484 circumstances the linker will display the final value enclosed
485 by square brackets. Thus for example a linker script
486 containing:
487 foo = 1
489 foo = foo * 4
490 foo = foo + 8
491 will produce the following output in the link map if the -M
493 option is used:
494 0x00000001 foo = 0x1
496 [0x0000000c] foo = (foo * 0x4)
497 [0x0000000c] foo = (foo + 0x8)
498 See Expressions for more information about expressions in
500 linker scripts.
501 • How GNU properties are merged.
503 When the linker merges input .note.gnu.property sections into
505 one output .note.gnu.property section, some properties are
506 removed or updated. These actions are reported in the link
507 map. For example:
508 Removed property 0xc0000002 to merge foo.o (0x1) and bar.o (not found)
510 This indicates that property 0xc0000002 is removed from output
512 when merging properties in foo.o, whose property 0xc0000002
513 value is 0x1, and bar.o, which doesn't have property
514 0xc0000002.
515 Updated property 0xc0010001 (0x1) to merge foo.o (0x1) and bar.o (0x1)
517 This indicates that property 0xc0010001 value is updated to 0x1
519 in output when merging properties in foo.o, whose 0xc0010001
520 property value is 0x1, and bar.o, whose 0xc0010001 property
521 value is 0x1.
522 --print-map-discarded
524 --no-print-map-discarded
525 Print (or do not print) the list of discarded and garbage collected
526 sections in the link map. Enabled by default.
527 -n
529 --nmagic
530 Turn off page alignment of sections, and disable linking against
531 shared libraries. If the output format supports Unix style magic
532 numbers, mark the output as "NMAGIC".
533 -N
535 --omagic
536 Set the text and data sections to be readable and writable. Also,
537 do not page-align the data segment, and disable linking against
538 shared libraries. If the output format supports Unix style magic
539 numbers, mark the output as "OMAGIC". Note: Although a writable
540 text section is allowed for PE-COFF targets, it does not conform to
541 the format specification published by Microsoft.
542 --no-omagic
544 This option negates most of the effects of the -N option. It sets
545 the text section to be read-only, and forces the data segment to be
546 page-aligned. Note - this option does not enable linking against
547 shared libraries. Use -Bdynamic for this.
548 -o output
550 --output=output
551 Use output as the name for the program produced by ld; if this
552 option is not specified, the name a.out is used by default. The
553 script command "OUTPUT" can also specify the output file name.
554 --dependency-file=depfile
556 Write a dependency file to depfile. This file contains a rule
557 suitable for "make" describing the output file and all the input
558 files that were read to produce it. The output is similar to the
559 compiler's output with -M -MP. Note that there is no option like
560 the compiler's -MM, to exclude "system files" (which is not a well-
561 specified concept in the linker, unlike "system headers" in the
562 compiler). So the output from --dependency-file is always specific
563 to the exact state of the installation where it was produced, and
564 should not be copied into distributed makefiles without careful
565 editing.
566 -O level
568 If level is a numeric values greater than zero ld optimizes the
569 output. This might take significantly longer and therefore
570 probably should only be enabled for the final binary. At the
571 moment this option only affects ELF shared library generation.
572 Future releases of the linker may make more use of this option.
573 Also currently there is no difference in the linker's behaviour for
574 different non-zero values of this option. Again this may change
575 with future releases.
576 -plugin name
578 Involve a plugin in the linking process. The name parameter is the
579 absolute filename of the plugin. Usually this parameter is
580 automatically added by the complier, when using link time
581 optimization, but users can also add their own plugins if they so
582 wish.
583 Note that the location of the compiler originated plugins is
585 different from the place where the ar, nm and ranlib programs
586 search for their plugins. In order for those commands to make use
587 of a compiler based plugin it must first be copied into the
588 ${libdir}/bfd-plugins directory. All gcc based linker plugins are
589 backward compatible, so it is sufficient to just copy in the newest
590 one.
591 --push-state
593 The --push-state allows one to preserve the current state of the
594 flags which govern the input file handling so that they can all be
595 restored with one corresponding --pop-state option.
596 The option which are covered are: -Bdynamic, -Bstatic, -dn, -dy,
598 -call_shared, -non_shared, -static, -N, -n, --whole-archive,
599 --no-whole-archive, -r, -Ur, --copy-dt-needed-entries,
600 --no-copy-dt-needed-entries, --as-needed, --no-as-needed, and -a.
601 One target for this option are specifications for pkg-config. When
603 used with the --libs option all possibly needed libraries are
604 listed and then possibly linked with all the time. It is better to
605 return something as follows:
606 -Wl,--push-state,--as-needed -libone -libtwo -Wl,--pop-state
608 --pop-state
610 Undoes the effect of --push-state, restores the previous values of
611 the flags governing input file handling.
612 -q
614 --emit-relocs
615 Leave relocation sections and contents in fully linked executables.
616 Post link analysis and optimization tools may need this information
617 in order to perform correct modifications of executables. This
618 results in larger executables.
619 This option is currently only supported on ELF platforms.
621 --force-dynamic
623 Force the output file to have dynamic sections. This option is
624 specific to VxWorks targets.
625 -r
627 --relocatable
628 Generate relocatable output---i.e., generate an output file that
629 can in turn serve as input to ld. This is often called partial
630 linking. As a side effect, in environments that support standard
631 Unix magic numbers, this option also sets the output file's magic
632 number to "OMAGIC". If this option is not specified, an absolute
633 file is produced. When linking C++ programs, this option will not
634 resolve references to constructors; to do that, use -Ur.
635 When an input file does not have the same format as the output
637 file, partial linking is only supported if that input file does not
638 contain any relocations. Different output formats can have further
639 restrictions; for example some "a.out"-based formats do not support
640 partial linking with input files in other formats at all.
641 This option does the same thing as -i.
643 -R filename
645 --just-symbols=filename
646 Read symbol names and their addresses from filename, but do not
647 relocate it or include it in the output. This allows your output
648 file to refer symbolically to absolute locations of memory defined
649 in other programs. You may use this option more than once.
650 For compatibility with other ELF linkers, if the -R option is
652 followed by a directory name, rather than a file name, it is
653 treated as the -rpath option.
654 -s
656 --strip-all
657 Omit all symbol information from the output file.
658 -S
660 --strip-debug
661 Omit debugger symbol information (but not all symbols) from the
662 output file.
663 --strip-discarded
665 --no-strip-discarded
666 Omit (or do not omit) global symbols defined in discarded sections.
667 Enabled by default.
668 -t
670 --trace
671 Print the names of the input files as ld processes them. If -t is
672 given twice then members within archives are also printed. -t
673 output is useful to generate a list of all the object files and
674 scripts involved in linking, for example, when packaging files for
675 a linker bug report.
676 -T scriptfile
678 --script=scriptfile
679 Use scriptfile as the linker script. This script replaces ld's
680 default linker script (rather than adding to it), so commandfile
681 must specify everything necessary to describe the output file.
682 If scriptfile does not exist in the current directory, "ld" looks
683 for it in the directories specified by any preceding -L options.
684 Multiple -T options accumulate.
685 -dT scriptfile
687 --default-script=scriptfile
688 Use scriptfile as the default linker script.
689 This option is similar to the --script option except that
691 processing of the script is delayed until after the rest of the
692 command line has been processed. This allows options placed after
693 the --default-script option on the command line to affect the
694 behaviour of the linker script, which can be important when the
695 linker command line cannot be directly controlled by the user. (eg
696 because the command line is being constructed by another tool, such
697 as gcc).
698 -u symbol
700 --undefined=symbol
701 Force symbol to be entered in the output file as an undefined
702 symbol. Doing this may, for example, trigger linking of additional
703 modules from standard libraries. -u may be repeated with different
704 option arguments to enter additional undefined symbols. This
705 option is equivalent to the "EXTERN" linker script command.
706 If this option is being used to force additional modules to be
708 pulled into the link, and if it is an error for the symbol to
709 remain undefined, then the option --require-defined should be used
710 instead.
711 --require-defined=symbol
713 Require that symbol is defined in the output file. This option is
714 the same as option --undefined except that if symbol is not defined
715 in the output file then the linker will issue an error and exit.
716 The same effect can be achieved in a linker script by using
717 "EXTERN", "ASSERT" and "DEFINED" together. This option can be used
718 multiple times to require additional symbols.
719 -Ur For anything other than C++ programs, this option is equivalent to
721 -r: it generates relocatable output---i.e., an output file that can
722 in turn serve as input to ld. When linking C++ programs, -Ur does
723 resolve references to constructors, unlike -r. It does not work to
724 use -Ur on files that were themselves linked with -Ur; once the
725 constructor table has been built, it cannot be added to. Use -Ur
726 only for the last partial link, and -r for the others.
727 --orphan-handling=MODE
729 Control how orphan sections are handled. An orphan section is one
730 not specifically mentioned in a linker script.
731 MODE can have any of the following values:
733 "place"
735 Orphan sections are placed into a suitable output section
736 following the strategy described in Orphan Sections. The
737 option --unique also affects how sections are placed.
738 "discard"
740 All orphan sections are discarded, by placing them in the
741 /DISCARD/ section.
742 "warn"
744 The linker will place the orphan section as for "place" and
745 also issue a warning.
746 "error"
748 The linker will exit with an error if any orphan section is
749 found.
750 The default if --orphan-handling is not given is "place".
752 --unique[=SECTION]
754 Creates a separate output section for every input section matching
755 SECTION, or if the optional wildcard SECTION argument is missing,
756 for every orphan input section. An orphan section is one not
757 specifically mentioned in a linker script. You may use this option
758 multiple times on the command line; It prevents the normal merging
759 of input sections with the same name, overriding output section
760 assignments in a linker script.
761 -v
763 --version
764 -V Display the version number for ld. The -V option also lists the
765 supported emulations.
766 -x
768 --discard-all
769 Delete all local symbols.
770 -X
772 --discard-locals
773 Delete all temporary local symbols. (These symbols start with
774 system-specific local label prefixes, typically .L for ELF systems
775 or L for traditional a.out systems.)
776 -y symbol
778 --trace-symbol=symbol
779 Print the name of each linked file in which symbol appears. This
780 option may be given any number of times. On many systems it is
781 necessary to prepend an underscore.
782 This option is useful when you have an undefined symbol in your
784 link but don't know where the reference is coming from.
785 -Y path
787 Add path to the default library search path. This option exists
788 for Solaris compatibility.
789 -z keyword
791 The recognized keywords are:
792 bndplt
794 Always generate BND prefix in PLT entries. Supported for
795 Linux/x86_64.
796 call-nop=prefix-addr
798 call-nop=suffix-nop
799 call-nop=prefix-byte
800 call-nop=suffix-byte
801 Specify the 1-byte "NOP" padding when transforming indirect
802 call to a locally defined function, foo, via its GOT slot.
803 call-nop=prefix-addr generates "0x67 call foo".
804 call-nop=suffix-nop generates "call foo 0x90".
805 call-nop=prefix-byte generates "byte call foo".
806 call-nop=suffix-byte generates "call foo byte". Supported for
807 i386 and x86_64.
808 cet-report=none
810 cet-report=warning
811 cet-report=error
812 Specify how to report the missing
813 GNU_PROPERTY_X86_FEATURE_1_IBT and
814 GNU_PROPERTY_X86_FEATURE_1_SHSTK properties in input
815 .note.gnu.property section. cet-report=none, which is the
816 default, will make the linker not report missing properties in
817 input files. cet-report=warning will make the linker issue a
818 warning for missing properties in input files.
819 cet-report=error will make the linker issue an error for
820 missing properties in input files. Note that ibt will turn off
821 the missing GNU_PROPERTY_X86_FEATURE_1_IBT property report and
822 shstk will turn off the missing
823 GNU_PROPERTY_X86_FEATURE_1_SHSTK property report. Supported
824 for Linux/i386 and Linux/x86_64.
825 combreloc
827 nocombreloc
828 Combine multiple dynamic relocation sections and sort to
829 improve dynamic symbol lookup caching. Do not do this if
830 nocombreloc.
831 common
833 nocommon
834 Generate common symbols with STT_COMMON type during a
835 relocatable link. Use STT_OBJECT type if nocommon.
836 common-page-size=value
838 Set the page size most commonly used to value. Memory image
839 layout will be optimized to minimize memory pages if the system
840 is using pages of this size.
841 defs
843 Report unresolved symbol references from regular object files.
844 This is done even if the linker is creating a non-symbolic
845 shared library. This option is the inverse of -z undefs.
846 dynamic-undefined-weak
848 nodynamic-undefined-weak
849 Make undefined weak symbols dynamic when building a dynamic
850 object, if they are referenced from a regular object file and
851 not forced local by symbol visibility or versioning. Do not
852 make them dynamic if nodynamic-undefined-weak. If neither
853 option is given, a target may default to either option being in
854 force, or make some other selection of undefined weak symbols
855 dynamic. Not all targets support these options.
856 execstack
858 Marks the object as requiring executable stack.
859 global
861 This option is only meaningful when building a shared object.
862 It makes the symbols defined by this shared object available
863 for symbol resolution of subsequently loaded libraries.
864 globalaudit
866 This option is only meaningful when building a dynamic
867 executable. This option marks the executable as requiring
868 global auditing by setting the "DF_1_GLOBAUDIT" bit in the
869 "DT_FLAGS_1" dynamic tag. Global auditing requires that any
870 auditing library defined via the --depaudit or -P command-line
871 options be run for all dynamic objects loaded by the
872 application.
873 ibtplt
875 Generate Intel Indirect Branch Tracking (IBT) enabled PLT
876 entries. Supported for Linux/i386 and Linux/x86_64.
877 ibt Generate GNU_PROPERTY_X86_FEATURE_1_IBT in .note.gnu.property
879 section to indicate compatibility with IBT. This also implies
880 ibtplt. Supported for Linux/i386 and Linux/x86_64.
881 indirect-extern-access
883 noindirect-extern-access
884 Generate GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS in
885 .note.gnu.property section to indicate that object file
886 requires canonical function pointers and cannot be used with
887 copy relocation. This option also implies noextern-protected-
888 data and nocopyreloc. Supported for i386 and x86-64.
889 noindirect-extern-access removes
891 GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS from
892 .note.gnu.property section.
893 initfirst
895 This option is only meaningful when building a shared object.
896 It marks the object so that its runtime initialization will
897 occur before the runtime initialization of any other objects
898 brought into the process at the same time. Similarly the
899 runtime finalization of the object will occur after the runtime
900 finalization of any other objects.
901 interpose
903 Specify that the dynamic loader should modify its symbol search
904 order so that symbols in this shared library interpose all
905 other shared libraries not so marked.
906 unique
908 nounique
909 When generating a shared library or other dynamically loadable
910 ELF object mark it as one that should (by default) only ever be
911 loaded once, and only in the main namespace (when using
912 "dlmopen"). This is primarily used to mark fundamental
913 libraries such as libc, libpthread et al which do not usually
914 function correctly unless they are the sole instances of
915 themselves. This behaviour can be overridden by the "dlmopen"
916 caller and does not apply to certain loading mechanisms (such
917 as audit libraries).
918 lam-u48
920 Generate GNU_PROPERTY_X86_FEATURE_1_LAM_U48 in
921 .note.gnu.property section to indicate compatibility with Intel
922 LAM_U48. Supported for Linux/x86_64.
923 lam-u57
925 Generate GNU_PROPERTY_X86_FEATURE_1_LAM_U57 in
926 .note.gnu.property section to indicate compatibility with Intel
927 LAM_U57. Supported for Linux/x86_64.
928 lam-u48-report=none
930 lam-u48-report=warning
931 lam-u48-report=error
932 Specify how to report the missing
933 GNU_PROPERTY_X86_FEATURE_1_LAM_U48 property in input
934 .note.gnu.property section. lam-u48-report=none, which is the
935 default, will make the linker not report missing properties in
936 input files. lam-u48-report=warning will make the linker issue
937 a warning for missing properties in input files.
938 lam-u48-report=error will make the linker issue an error for
939 missing properties in input files. Supported for Linux/x86_64.
940 lam-u57-report=none
942 lam-u57-report=warning
943 lam-u57-report=error
944 Specify how to report the missing
945 GNU_PROPERTY_X86_FEATURE_1_LAM_U57 property in input
946 .note.gnu.property section. lam-u57-report=none, which is the
947 default, will make the linker not report missing properties in
948 input files. lam-u57-report=warning will make the linker issue
949 a warning for missing properties in input files.
950 lam-u57-report=error will make the linker issue an error for
951 missing properties in input files. Supported for Linux/x86_64.
952 lam-report=none
954 lam-report=warning
955 lam-report=error
956 Specify how to report the missing
957 GNU_PROPERTY_X86_FEATURE_1_LAM_U48 and
958 GNU_PROPERTY_X86_FEATURE_1_LAM_U57 properties in input
959 .note.gnu.property section. lam-report=none, which is the
960 default, will make the linker not report missing properties in
961 input files. lam-report=warning will make the linker issue a
962 warning for missing properties in input files.
963 lam-report=error will make the linker issue an error for
964 missing properties in input files. Supported for Linux/x86_64.
965 lazy
967 When generating an executable or shared library, mark it to
968 tell the dynamic linker to defer function call resolution to
969 the point when the function is called (lazy binding), rather
970 than at load time. Lazy binding is the default.
971 loadfltr
973 Specify that the object's filters be processed immediately at
974 runtime.
975 max-page-size=value
977 Set the maximum memory page size supported to value.
978 muldefs
980 Allow multiple definitions.
981 nocopyreloc
983 Disable linker generated .dynbss variables used in place of
984 variables defined in shared libraries. May result in dynamic
985 text relocations.
986 nodefaultlib
988 Specify that the dynamic loader search for dependencies of this
989 object should ignore any default library search paths.
990 nodelete
992 Specify that the object shouldn't be unloaded at runtime.
993 nodlopen
995 Specify that the object is not available to "dlopen".
996 nodump
998 Specify that the object can not be dumped by "dldump".
999 noexecstack
1001 Marks the object as not requiring executable stack.
1002 noextern-protected-data
1004 Don't treat protected data symbols as external when building a
1005 shared library. This option overrides the linker backend
1006 default. It can be used to work around incorrect relocations
1007 against protected data symbols generated by compiler. Updates
1008 on protected data symbols by another module aren't visible to
1009 the resulting shared library. Supported for i386 and x86-64.
1010 noreloc-overflow
1012 Disable relocation overflow check. This can be used to disable
1013 relocation overflow check if there will be no dynamic
1014 relocation overflow at run-time. Supported for x86_64.
1015 now When generating an executable or shared library, mark it to
1017 tell the dynamic linker to resolve all symbols when the program
1018 is started, or when the shared library is loaded by dlopen,
1019 instead of deferring function call resolution to the point when
1020 the function is first called.
1021 origin
1023 Specify that the object requires $ORIGIN handling in paths.
1024 pack-relative-relocs
1026 nopack-relative-relocs
1027 Generate compact relative relocation in position-independent
1028 executable and shared library. It adds "DT_RELR", "DT_RELRSZ"
1029 and "DT_RELRENT" entries to the dynamic section. It is ignored
1030 when building position-dependent executable and relocatable
1031 output. nopack-relative-relocs is the default, which disables
1032 compact relative relocation. When linked against the GNU C
1033 Library, a GLIBC_ABI_DT_RELR symbol version dependency on the
1034 shared C Library is added to the output. Supported for i386
1035 and x86-64.
1036 relro
1038 norelro
1039 Create an ELF "PT_GNU_RELRO" segment header in the object.
1040 This specifies a memory segment that should be made read-only
1041 after relocation, if supported. Specifying common-page-size
1042 smaller than the system page size will render this protection
1043 ineffective. Don't create an ELF "PT_GNU_RELRO" segment if
1044 norelro.
1045 report-relative-reloc
1047 Report dynamic relative relocations generated by linker.
1048 Supported for Linux/i386 and Linux/x86_64.
1049 separate-code
1051 noseparate-code
1052 Create separate code "PT_LOAD" segment header in the object.
1053 This specifies a memory segment that should contain only
1054 instructions and must be in wholly disjoint pages from any
1055 other data. Don't create separate code "PT_LOAD" segment if
1056 noseparate-code is used.
1057 shstk
1059 Generate GNU_PROPERTY_X86_FEATURE_1_SHSTK in .note.gnu.property
1060 section to indicate compatibility with Intel Shadow Stack.
1061 Supported for Linux/i386 and Linux/x86_64.
1062 stack-size=value
1064 Specify a stack size for an ELF "PT_GNU_STACK" segment.
1065 Specifying zero will override any default non-zero sized
1066 "PT_GNU_STACK" segment creation.
1067 start-stop-gc
1069 nostart-stop-gc
1070 When --gc-sections is in effect, a reference from a retained
1071 section to "__start_SECNAME" or "__stop_SECNAME" causes all
1072 input sections named "SECNAME" to also be retained, if
1073 "SECNAME" is representable as a C identifier and either
1074 "__start_SECNAME" or "__stop_SECNAME" is synthesized by the
1075 linker. -z start-stop-gc disables this effect, allowing
1076 sections to be garbage collected as if the special synthesized
1077 symbols were not defined. -z start-stop-gc has no effect on a
1078 definition of "__start_SECNAME" or "__stop_SECNAME" in an
1079 object file or linker script. Such a definition will prevent
1080 the linker providing a synthesized "__start_SECNAME" or
1081 "__stop_SECNAME" respectively, and therefore the special
1082 treatment by garbage collection for those references.
1083 start-stop-visibility=value
1085 Specify the ELF symbol visibility for synthesized
1086 "__start_SECNAME" and "__stop_SECNAME" symbols. value must be
1087 exactly default, internal, hidden, or protected. If no -z
1088 start-stop-visibility option is given, protected is used for
1089 compatibility with historical practice. However, it's highly
1090 recommended to use -z start-stop-visibility=hidden in new
1091 programs and shared libraries so that these symbols are not
1092 exported between shared objects, which is not usually what's
1093 intended.
1094 text
1096 notext
1097 textoff
1098 Report an error if DT_TEXTREL is set, i.e., if the position-
1099 independent or shared object has dynamic relocations in read-
1100 only sections. Don't report an error if notext or textoff.
1101 undefs
1103 Do not report unresolved symbol references from regular object
1104 files, either when creating an executable, or when creating a
1105 shared library. This option is the inverse of -z defs.
1106 unique-symbol
1108 nounique-symbol
1109 Avoid duplicated local symbol names in the symbol string table.
1110 Append "."number"" to duplicated local symbol names if unique-
1111 symbol is used. nounique-symbol is the default.
1112 x86-64-baseline
1114 x86-64-v2
1115 x86-64-v3
1116 x86-64-v4
1117 Specify the x86-64 ISA level needed in .note.gnu.property
1118 section. x86-64-baseline generates
1119 "GNU_PROPERTY_X86_ISA_1_BASELINE". x86-64-v2 generates
1120 "GNU_PROPERTY_X86_ISA_1_V2". x86-64-v3 generates
1121 "GNU_PROPERTY_X86_ISA_1_V3". x86-64-v4 generates
1122 "GNU_PROPERTY_X86_ISA_1_V4". Supported for Linux/i386 and
1123 Linux/x86_64.
1124 Other keywords are ignored for Solaris compatibility.
1126 -( archives -)
1128 --start-group archives --end-group
1129 The archives should be a list of archive files. They may be either
1130 explicit file names, or -l options.
1131 The specified archives are searched repeatedly until no new
1133 undefined references are created. Normally, an archive is searched
1134 only once in the order that it is specified on the command line.
1135 If a symbol in that archive is needed to resolve an undefined
1136 symbol referred to by an object in an archive that appears later on
1137 the command line, the linker would not be able to resolve that
1138 reference. By grouping the archives, they will all be searched
1139 repeatedly until all possible references are resolved.
1140 Using this option has a significant performance cost. It is best
1142 to use it only when there are unavoidable circular references
1143 between two or more archives.
1144 --accept-unknown-input-arch
1146 --no-accept-unknown-input-arch
1147 Tells the linker to accept input files whose architecture cannot be
1148 recognised. The assumption is that the user knows what they are
1149 doing and deliberately wants to link in these unknown input files.
1150 This was the default behaviour of the linker, before release 2.14.
1151 The default behaviour from release 2.14 onwards is to reject such
1152 input files, and so the --accept-unknown-input-arch option has been
1153 added to restore the old behaviour.
1154 --as-needed
1156 --no-as-needed
1157 This option affects ELF DT_NEEDED tags for dynamic libraries
1158 mentioned on the command line after the --as-needed option.
1159 Normally the linker will add a DT_NEEDED tag for each dynamic
1160 library mentioned on the command line, regardless of whether the
1161 library is actually needed or not. --as-needed causes a DT_NEEDED
1162 tag to only be emitted for a library that at that point in the link
1163 satisfies a non-weak undefined symbol reference from a regular
1164 object file or, if the library is not found in the DT_NEEDED lists
1165 of other needed libraries, a non-weak undefined symbol reference
1166 from another needed dynamic library. Object files or libraries
1167 appearing on the command line after the library in question do not
1168 affect whether the library is seen as needed. This is similar to
1169 the rules for extraction of object files from archives.
1170 --no-as-needed restores the default behaviour.
1171 Note: On Linux based systems the --as-needed option also has an
1173 affect on the behaviour of the --rpath and --rpath-link options.
1174 See the description of --rpath-link for more details.
1175 --add-needed
1177 --no-add-needed
1178 These two options have been deprecated because of the similarity of
1179 their names to the --as-needed and --no-as-needed options. They
1180 have been replaced by --copy-dt-needed-entries and
1181 --no-copy-dt-needed-entries.
1182 -assert keyword
1184 This option is ignored for SunOS compatibility.
1185 -Bdynamic
1187 -dy
1188 -call_shared
1189 Link against dynamic libraries. This is only meaningful on
1190 platforms for which shared libraries are supported. This option is
1191 normally the default on such platforms. The different variants of
1192 this option are for compatibility with various systems. You may
1193 use this option multiple times on the command line: it affects
1194 library searching for -l options which follow it.
1195 -Bgroup
1197 Set the "DF_1_GROUP" flag in the "DT_FLAGS_1" entry in the dynamic
1198 section. This causes the runtime linker to handle lookups in this
1199 object and its dependencies to be performed only inside the group.
1200 --unresolved-symbols=report-all is implied. This option is only
1201 meaningful on ELF platforms which support shared libraries.
1202 -Bstatic
1204 -dn
1205 -non_shared
1206 -static
1207 Do not link against shared libraries. This is only meaningful on
1208 platforms for which shared libraries are supported. The different
1209 variants of this option are for compatibility with various systems.
1210 You may use this option multiple times on the command line: it
1211 affects library searching for -l options which follow it. This
1212 option also implies --unresolved-symbols=report-all. This option
1213 can be used with -shared. Doing so means that a shared library is
1214 being created but that all of the library's external references
1215 must be resolved by pulling in entries from static libraries.
1216 -Bsymbolic
1218 When creating a shared library, bind references to global symbols
1219 to the definition within the shared library, if any. Normally, it
1220 is possible for a program linked against a shared library to
1221 override the definition within the shared library. This option is
1222 only meaningful on ELF platforms which support shared libraries.
1223 -Bsymbolic-functions
1225 When creating a shared library, bind references to global function
1226 symbols to the definition within the shared library, if any. This
1227 option is only meaningful on ELF platforms which support shared
1228 libraries.
1229 -Bno-symbolic
1231 This option can cancel previously specified -Bsymbolic and
1232 -Bsymbolic-functions.
1233 --dynamic-list=dynamic-list-file
1235 Specify the name of a dynamic list file to the linker. This is
1236 typically used when creating shared libraries to specify a list of
1237 global symbols whose references shouldn't be bound to the
1238 definition within the shared library, or creating dynamically
1239 linked executables to specify a list of symbols which should be
1240 added to the symbol table in the executable. This option is only
1241 meaningful on ELF platforms which support shared libraries.
1242 The format of the dynamic list is the same as the version node
1244 without scope and node name. See VERSION for more information.
1245 --dynamic-list-data
1247 Include all global data symbols to the dynamic list.
1248 --dynamic-list-cpp-new
1250 Provide the builtin dynamic list for C++ operator new and delete.
1251 It is mainly useful for building shared libstdc++.
1252 --dynamic-list-cpp-typeinfo
1254 Provide the builtin dynamic list for C++ runtime type
1255 identification.
1256 --check-sections
1258 --no-check-sections
1259 Asks the linker not to check section addresses after they have been
1260 assigned to see if there are any overlaps. Normally the linker
1261 will perform this check, and if it finds any overlaps it will
1262 produce suitable error messages. The linker does know about, and
1263 does make allowances for sections in overlays. The default
1264 behaviour can be restored by using the command-line switch
1265 --check-sections. Section overlap is not usually checked for
1266 relocatable links. You can force checking in that case by using
1267 the --check-sections option.
1268 --copy-dt-needed-entries
1270 --no-copy-dt-needed-entries
1271 This option affects the treatment of dynamic libraries referred to
1272 by DT_NEEDED tags inside ELF dynamic libraries mentioned on the
1273 command line. Normally the linker won't add a DT_NEEDED tag to the
1274 output binary for each library mentioned in a DT_NEEDED tag in an
1275 input dynamic library. With --copy-dt-needed-entries specified on
1276 the command line however any dynamic libraries that follow it will
1277 have their DT_NEEDED entries added. The default behaviour can be
1278 restored with --no-copy-dt-needed-entries.
1279 This option also has an effect on the resolution of symbols in
1281 dynamic libraries. With --copy-dt-needed-entries dynamic libraries
1282 mentioned on the command line will be recursively searched,
1283 following their DT_NEEDED tags to other libraries, in order to
1284 resolve symbols required by the output binary. With the default
1285 setting however the searching of dynamic libraries that follow it
1286 will stop with the dynamic library itself. No DT_NEEDED links will
1287 be traversed to resolve symbols.
1288 --cref
1290 Output a cross reference table. If a linker map file is being
1291 generated, the cross reference table is printed to the map file.
1292 Otherwise, it is printed on the standard output.
1293 The format of the table is intentionally simple, so that it may be
1295 easily processed by a script if necessary. The symbols are printed
1296 out, sorted by name. For each symbol, a list of file names is
1297 given. If the symbol is defined, the first file listed is the
1298 location of the definition. If the symbol is defined as a common
1299 value then any files where this happens appear next. Finally any
1300 files that reference the symbol are listed.
1301 --ctf-variables
1303 --no-ctf-variables
1304 The CTF debuginfo format supports a section which encodes the names
1305 and types of variables found in the program which do not appear in
1306 any symbol table. These variables clearly cannot be looked up by
1307 address by conventional debuggers, so the space used for their
1308 types and names is usually wasted: the types are usually small but
1309 the names are often not. --ctf-variables causes the generation of
1310 such a section. The default behaviour can be restored with
1311 --no-ctf-variables.
1312 --ctf-share-types=method
1314 Adjust the method used to share types between translation units in
1315 CTF.
1316 share-unconflicted
1318 Put all types that do not have ambiguous definitions into the
1319 shared dictionary, where debuggers can easily access them, even
1320 if they only occur in one translation unit. This is the
1321 default.
1322 share-duplicated
1324 Put only types that occur in multiple translation units into
1325 the shared dictionary: types with only one definition go into
1326 per-translation-unit dictionaries. Types with ambiguous
1327 definitions in multiple translation units always go into per-
1328 translation-unit dictionaries. This tends to make the CTF
1329 larger, but may reduce the amount of CTF in the shared
1330 dictionary. For very large projects this may speed up opening
1331 the CTF and save memory in the CTF consumer at runtime.
1332 --no-define-common
1334 This option inhibits the assignment of addresses to common symbols.
1335 The script command "INHIBIT_COMMON_ALLOCATION" has the same effect.
1336 The --no-define-common option allows decoupling the decision to
1338 assign addresses to Common symbols from the choice of the output
1339 file type; otherwise a non-Relocatable output type forces assigning
1340 addresses to Common symbols. Using --no-define-common allows
1341 Common symbols that are referenced from a shared library to be
1342 assigned addresses only in the main program. This eliminates the
1343 unused duplicate space in the shared library, and also prevents any
1344 possible confusion over resolving to the wrong duplicate when there
1345 are many dynamic modules with specialized search paths for runtime
1346 symbol resolution.
1347 --force-group-allocation
1349 This option causes the linker to place section group members like
1350 normal input sections, and to delete the section groups. This is
1351 the default behaviour for a final link but this option can be used
1352 to change the behaviour of a relocatable link (-r). The script
1353 command "FORCE_GROUP_ALLOCATION" has the same effect.
1354 --defsym=symbol=expression
1356 Create a global symbol in the output file, containing the absolute
1357 address given by expression. You may use this option as many times
1358 as necessary to define multiple symbols in the command line. A
1359 limited form of arithmetic is supported for the expression in this
1360 context: you may give a hexadecimal constant or the name of an
1361 existing symbol, or use "+" and "-" to add or subtract hexadecimal
1362 constants or symbols. If you need more elaborate expressions,
1363 consider using the linker command language from a script. Note:
1364 there should be no white space between symbol, the equals sign
1365 ("="), and expression.
1366 The linker processes --defsym arguments and -T arguments in order,
1368 placing --defsym before -T will define the symbol before the linker
1369 script from -T is processed, while placing --defsym after -T will
1370 define the symbol after the linker script has been processed. This
1371 difference has consequences for expressions within the linker
1372 script that use the --defsym symbols, which order is correct will
1373 depend on what you are trying to achieve.
1374 --demangle[=style]
1376 --no-demangle
1377 These options control whether to demangle symbol names in error
1378 messages and other output. When the linker is told to demangle, it
1379 tries to present symbol names in a readable fashion: it strips
1380 leading underscores if they are used by the object file format, and
1381 converts C++ mangled symbol names into user readable names.
1382 Different compilers have different mangling styles. The optional
1383 demangling style argument can be used to choose an appropriate
1384 demangling style for your compiler. The linker will demangle by
1385 default unless the environment variable COLLECT_NO_DEMANGLE is set.
1386 These options may be used to override the default.
1387 -Ifile
1389 --dynamic-linker=file
1390 Set the name of the dynamic linker. This is only meaningful when
1391 generating dynamically linked ELF executables. The default dynamic
1392 linker is normally correct; don't use this unless you know what you
1393 are doing.
1394 --no-dynamic-linker
1396 When producing an executable file, omit the request for a dynamic
1397 linker to be used at load-time. This is only meaningful for ELF
1398 executables that contain dynamic relocations, and usually requires
1399 entry point code that is capable of processing these relocations.
1400 --embedded-relocs
1402 This option is similar to the --emit-relocs option except that the
1403 relocs are stored in a target-specific section. This option is
1404 only supported by the BFIN, CR16 and M68K targets.
1405 --disable-multiple-abs-defs
1407 Do not allow multiple definitions with symbols included in filename
1408 invoked by -R or --just-symbols
1409 --fatal-warnings
1411 --no-fatal-warnings
1412 Treat all warnings as errors. The default behaviour can be
1413 restored with the option --no-fatal-warnings.
1414 --force-exe-suffix
1416 Make sure that an output file has a .exe suffix.
1417 If a successfully built fully linked output file does not have a
1419 ".exe" or ".dll" suffix, this option forces the linker to copy the
1420 output file to one of the same name with a ".exe" suffix. This
1421 option is useful when using unmodified Unix makefiles on a
1422 Microsoft Windows host, since some versions of Windows won't run an
1423 image unless it ends in a ".exe" suffix.
1424 --gc-sections
1426 --no-gc-sections
1427 Enable garbage collection of unused input sections. It is ignored
1428 on targets that do not support this option. The default behaviour
1429 (of not performing this garbage collection) can be restored by
1430 specifying --no-gc-sections on the command line. Note that garbage
1431 collection for COFF and PE format targets is supported, but the
1432 implementation is currently considered to be experimental.
1433 --gc-sections decides which input sections are used by examining
1435 symbols and relocations. The section containing the entry symbol
1436 and all sections containing symbols undefined on the command-line
1437 will be kept, as will sections containing symbols referenced by
1438 dynamic objects. Note that when building shared libraries, the
1439 linker must assume that any visible symbol is referenced. Once
1440 this initial set of sections has been determined, the linker
1441 recursively marks as used any section referenced by their
1442 relocations. See --entry, --undefined, and --gc-keep-exported.
1443 This option can be set when doing a partial link (enabled with
1445 option -r). In this case the root of symbols kept must be
1446 explicitly specified either by one of the options --entry,
1447 --undefined, or --gc-keep-exported or by a "ENTRY" command in the
1448 linker script.
1449 As a GNU extension, ELF input sections marked with the
1451 "SHF_GNU_RETAIN" flag will not be garbage collected.
1452 --print-gc-sections
1454 --no-print-gc-sections
1455 List all sections removed by garbage collection. The listing is
1456 printed on stderr. This option is only effective if garbage
1457 collection has been enabled via the --gc-sections) option. The
1458 default behaviour (of not listing the sections that are removed)
1459 can be restored by specifying --no-print-gc-sections on the command
1460 line.
1461 --gc-keep-exported
1463 When --gc-sections is enabled, this option prevents garbage
1464 collection of unused input sections that contain global symbols
1465 having default or protected visibility. This option is intended to
1466 be used for executables where unreferenced sections would otherwise
1467 be garbage collected regardless of the external visibility of
1468 contained symbols. Note that this option has no effect when
1469 linking shared objects since it is already the default behaviour.
1470 This option is only supported for ELF format targets.
1471 --print-output-format
1473 Print the name of the default output format (perhaps influenced by
1474 other command-line options). This is the string that would appear
1475 in an "OUTPUT_FORMAT" linker script command.
1476 --print-memory-usage
1478 Print used size, total size and used size of memory regions created
1479 with the MEMORY command. This is useful on embedded targets to
1480 have a quick view of amount of free memory. The format of the
1481 output has one headline and one line per region. It is both human
1482 readable and easily parsable by tools. Here is an example of an
1483 output:
1484 Memory region Used Size Region Size %age Used
1486 ROM: 256 KB 1 MB 25.00%
1487 RAM: 32 B 2 GB 0.00%
1488 --help
1490 Print a summary of the command-line options on the standard output
1491 and exit.
1492 --target-help
1494 Print a summary of all target-specific options on the standard
1495 output and exit.
1496 -Map=mapfile
1498 Print a link map to the file mapfile. See the description of the
1499 -M option, above. If mapfile is just the character "-" then the
1500 map will be written to stdout.
1501 Specifying a directory as mapfile causes the linker map to be
1503 written as a file inside the directory. Normally name of the file
1504 inside the directory is computed as the basename of the output file
1505 with ".map" appended. If however the special character "%" is
1506 used then this will be replaced by the full path of the output
1507 file. Additionally if there are any characters after the % symbol
1508 then ".map" will no longer be appended.
1509 -o foo.exe -Map=bar [Creates ./bar]
1511 -o ../dir/foo.exe -Map=bar [Creates ./bar]
1512 -o foo.exe -Map=../dir [Creates ../dir/foo.exe.map]
1513 -o ../dir2/foo.exe -Map=../dir [Creates ../dir/foo.exe.map]
1514 -o foo.exe -Map=% [Creates ./foo.exe.map]
1515 -o ../dir/foo.exe -Map=% [Creates ../dir/foo.exe.map]
1516 -o foo.exe -Map=%.bar [Creates ./foo.exe.bar]
1517 -o ../dir/foo.exe -Map=%.bar [Creates ../dir/foo.exe.bar]
1518 -o ../dir2/foo.exe -Map=../dir/% [Creates ../dir/../dir2/foo.exe.map]
1519 -o ../dir2/foo.exe -Map=../dir/%.bar [Creates ../dir/../dir2/foo.exe.bar]
1520 It is an error to specify more than one "%" character.
1522 If the map file already exists then it will be overwritten by this
1524 operation.
1525 --no-keep-memory
1527 ld normally optimizes for speed over memory usage by caching the
1528 symbol tables of input files in memory. This option tells ld to
1529 instead optimize for memory usage, by rereading the symbol tables
1530 as necessary. This may be required if ld runs out of memory space
1531 while linking a large executable.
1532 --no-undefined
1534 -z defs
1535 Report unresolved symbol references from regular object files.
1536 This is done even if the linker is creating a non-symbolic shared
1537 library. The switch --[no-]allow-shlib-undefined controls the
1538 behaviour for reporting unresolved references found in shared
1539 libraries being linked in.
1540 The effects of this option can be reverted by using "-z undefs".
1542 --allow-multiple-definition
1544 -z muldefs
1545 Normally when a symbol is defined multiple times, the linker will
1546 report a fatal error. These options allow multiple definitions and
1547 the first definition will be used.
1548 --allow-shlib-undefined
1550 --no-allow-shlib-undefined
1551 Allows or disallows undefined symbols in shared libraries. This
1552 switch is similar to --no-undefined except that it determines the
1553 behaviour when the undefined symbols are in a shared library rather
1554 than a regular object file. It does not affect how undefined
1555 symbols in regular object files are handled.
1556 The default behaviour is to report errors for any undefined symbols
1558 referenced in shared libraries if the linker is being used to
1559 create an executable, but to allow them if the linker is being used
1560 to create a shared library.
1561 The reasons for allowing undefined symbol references in shared
1563 libraries specified at link time are that:
1564 • A shared library specified at link time may not be the same as
1566 the one that is available at load time, so the symbol might
1567 actually be resolvable at load time.
1568 • There are some operating systems, eg BeOS and HPPA, where
1570 undefined symbols in shared libraries are normal.
1571 The BeOS kernel for example patches shared libraries at load
1573 time to select whichever function is most appropriate for the
1574 current architecture. This is used, for example, to
1575 dynamically select an appropriate memset function.
1576 --error-handling-script=scriptname
1578 If this option is provided then the linker will invoke scriptname
1579 whenever an error is encountered. Currently however only two kinds
1580 of error are supported: missing symbols and missing libraries. Two
1581 arguments will be passed to script: the keyword "undefined-symbol"
1582 or `missing-lib" and the name of the undefined symbol or missing
1583 library. The intention is that the script will provide suggestions
1584 to the user as to where the symbol or library might be found.
1585 After the script has finished then the normal linker error message
1586 will be displayed.
1587 The availability of this option is controlled by a configure time
1589 switch, so it may not be present in specific implementations.
1590 --no-undefined-version
1592 Normally when a symbol has an undefined version, the linker will
1593 ignore it. This option disallows symbols with undefined version and
1594 a fatal error will be issued instead.
1595 --default-symver
1597 Create and use a default symbol version (the soname) for
1598 unversioned exported symbols.
1599 --default-imported-symver
1601 Create and use a default symbol version (the soname) for
1602 unversioned imported symbols.
1603 --no-warn-mismatch
1605 Normally ld will give an error if you try to link together input
1606 files that are mismatched for some reason, perhaps because they
1607 have been compiled for different processors or for different
1608 endiannesses. This option tells ld that it should silently permit
1609 such possible errors. This option should only be used with care,
1610 in cases when you have taken some special action that ensures that
1611 the linker errors are inappropriate.
1612 --no-warn-search-mismatch
1614 Normally ld will give a warning if it finds an incompatible library
1615 during a library search. This option silences the warning.
1616 --no-whole-archive
1618 Turn off the effect of the --whole-archive option for subsequent
1619 archive files.
1620 --noinhibit-exec
1622 Retain the executable output file whenever it is still usable.
1623 Normally, the linker will not produce an output file if it
1624 encounters errors during the link process; it exits without writing
1625 an output file when it issues any error whatsoever.
1626 -nostdlib
1628 Only search library directories explicitly specified on the command
1629 line. Library directories specified in linker scripts (including
1630 linker scripts specified on the command line) are ignored.
1631 --oformat=output-format
1633 ld may be configured to support more than one kind of object file.
1634 If your ld is configured this way, you can use the --oformat option
1635 to specify the binary format for the output object file. Even when
1636 ld is configured to support alternative object formats, you don't
1637 usually need to specify this, as ld should be configured to produce
1638 as a default output format the most usual format on each machine.
1639 output-format is a text string, the name of a particular format
1640 supported by the BFD libraries. (You can list the available binary
1641 formats with objdump -i.) The script command "OUTPUT_FORMAT" can
1642 also specify the output format, but this option overrides it.
1643 --out-implib file
1645 Create an import library in file corresponding to the executable
1646 the linker is generating (eg. a DLL or ELF program). This import
1647 library (which should be called "*.dll.a" or "*.a" for DLLs) may be
1648 used to link clients against the generated executable; this
1649 behaviour makes it possible to skip a separate import library
1650 creation step (eg. "dlltool" for DLLs). This option is only
1651 available for the i386 PE and ELF targetted ports of the linker.
1652 -pie
1654 --pic-executable
1655 Create a position independent executable. This is currently only
1656 supported on ELF platforms. Position independent executables are
1657 similar to shared libraries in that they are relocated by the
1658 dynamic linker to the virtual address the OS chooses for them
1659 (which can vary between invocations). Like normal dynamically
1660 linked executables they can be executed and symbols defined in the
1661 executable cannot be overridden by shared libraries.
1662 -no-pie
1664 Create a position dependent executable. This is the default.
1665 -qmagic
1667 This option is ignored for Linux compatibility.
1668 -Qy This option is ignored for SVR4 compatibility.
1670 --relax
1672 --no-relax
1673 An option with machine dependent effects. This option is only
1674 supported on a few targets.
1675 On some platforms the --relax option performs target specific,
1677 global optimizations that become possible when the linker resolves
1678 addressing in the program, such as relaxing address modes,
1679 synthesizing new instructions, selecting shorter version of current
1680 instructions, and combining constant values.
1681 On some platforms these link time global optimizations may make
1683 symbolic debugging of the resulting executable impossible. This is
1684 known to be the case for the Matsushita MN10200 and MN10300 family
1685 of processors.
1686 On platforms where the feature is supported, the option --no-relax
1688 will disable it.
1689 On platforms where the feature is not supported, both --relax and
1691 --no-relax are accepted, but ignored.
1692 --retain-symbols-file=filename
1694 Retain only the symbols listed in the file filename, discarding all
1695 others. filename is simply a flat file, with one symbol name per
1696 line. This option is especially useful in environments (such as
1697 VxWorks) where a large global symbol table is accumulated
1698 gradually, to conserve run-time memory.
1699 --retain-symbols-file does not discard undefined symbols, or
1701 symbols needed for relocations.
1702 You may only specify --retain-symbols-file once in the command
1704 line. It overrides -s and -S.
1705 -rpath=dir
1707 Add a directory to the runtime library search path. This is used
1708 when linking an ELF executable with shared objects. All -rpath
1709 arguments are concatenated and passed to the runtime linker, which
1710 uses them to locate shared objects at runtime.
1711 The -rpath option is also used when locating shared objects which
1713 are needed by shared objects explicitly included in the link; see
1714 the description of the -rpath-link option. Searching -rpath in
1715 this way is only supported by native linkers and cross linkers
1716 which have been configured with the --with-sysroot option.
1717 If -rpath is not used when linking an ELF executable, the contents
1719 of the environment variable "LD_RUN_PATH" will be used if it is
1720 defined.
1721 The -rpath option may also be used on SunOS. By default, on SunOS,
1723 the linker will form a runtime search path out of all the -L
1724 options it is given. If a -rpath option is used, the runtime
1725 search path will be formed exclusively using the -rpath options,
1726 ignoring the -L options. This can be useful when using gcc, which
1727 adds many -L options which may be on NFS mounted file systems.
1728 For compatibility with other ELF linkers, if the -R option is
1730 followed by a directory name, rather than a file name, it is
1731 treated as the -rpath option.
1732 -rpath-link=dir
1734 When using ELF or SunOS, one shared library may require another.
1735 This happens when an "ld -shared" link includes a shared library as
1736 one of the input files.
1737 When the linker encounters such a dependency when doing a non-
1739 shared, non-relocatable link, it will automatically try to locate
1740 the required shared library and include it in the link, if it is
1741 not included explicitly. In such a case, the -rpath-link option
1742 specifies the first set of directories to search. The -rpath-link
1743 option may specify a sequence of directory names either by
1744 specifying a list of names separated by colons, or by appearing
1745 multiple times.
1746 The tokens $ORIGIN and $LIB can appear in these search directories.
1748 They will be replaced by the full path to the directory containing
1749 the program or shared object in the case of $ORIGIN and either lib
1750 - for 32-bit binaries - or lib64 - for 64-bit binaries - in the
1751 case of $LIB.
1752 The alternative form of these tokens - ${ORIGIN} and ${LIB} can
1754 also be used. The token $PLATFORM is not supported.
1755 This option should be used with caution as it overrides the search
1757 path that may have been hard compiled into a shared library. In
1758 such a case it is possible to use unintentionally a different
1759 search path than the runtime linker would do.
1760 The linker uses the following search paths to locate required
1762 shared libraries:
1763 1. Any directories specified by -rpath-link options.
1765 2. Any directories specified by -rpath options. The difference
1767 between -rpath and -rpath-link is that directories specified by
1768 -rpath options are included in the executable and used at
1769 runtime, whereas the -rpath-link option is only effective at
1770 link time. Searching -rpath in this way is only supported by
1771 native linkers and cross linkers which have been configured
1772 with the --with-sysroot option.
1773 3. On an ELF system, for native linkers, if the -rpath and
1775 -rpath-link options were not used, search the contents of the
1776 environment variable "LD_RUN_PATH".
1777 4. On SunOS, if the -rpath option was not used, search any
1779 directories specified using -L options.
1780 5. For a native linker, search the contents of the environment
1782 variable "LD_LIBRARY_PATH".
1783 6. For a native ELF linker, the directories in "DT_RUNPATH" or
1785 "DT_RPATH" of a shared library are searched for shared
1786 libraries needed by it. The "DT_RPATH" entries are ignored if
1787 "DT_RUNPATH" entries exist.
1788 7. For a linker for a Linux system, if the file /etc/ld.so.conf
1790 exists, the list of directories found in that file. Note: the
1791 path to this file is prefixed with the "sysroot" value, if that
1792 is defined, and then any "prefix" string if the linker was
1793 configured with the --prefix=<path> option.
1794 8. For a native linker on a FreeBSD system, any directories
1796 specified by the "_PATH_ELF_HINTS" macro defined in the
1797 elf-hints.h header file.
1798 9. Any directories specified by a "SEARCH_DIR" command in a linker
1800 script given on the command line, including scripts specified
1801 by -T (but not -dT).
1802 10. The default directories, normally /lib and /usr/lib.
1804 11. Any directories specified by a plugin
1806 LDPT_SET_EXTRA_LIBRARY_PATH.
1807 12. Any directories specified by a "SEARCH_DIR" command in a
1809 default linker script.
1810 Note however on Linux based systems there is an additional caveat:
1812 If the --as-needed option is active and a shared library is located
1813 which would normally satisfy the search and this library does not
1814 have DT_NEEDED tag for libc.so and there is a shared library later
1815 on in the set of search directories which also satisfies the search
1816 and this second shared library does have a DT_NEEDED tag for
1817 libc.so then the second library will be selected instead of the
1818 first.
1819 If the required shared library is not found, the linker will issue
1821 a warning and continue with the link.
1822 -shared
1824 -Bshareable
1825 Create a shared library. This is currently only supported on ELF,
1826 XCOFF and SunOS platforms. On SunOS, the linker will automatically
1827 create a shared library if the -e option is not used and there are
1828 undefined symbols in the link.
1829 --sort-common
1831 --sort-common=ascending
1832 --sort-common=descending
1833 This option tells ld to sort the common symbols by alignment in
1834 ascending or descending order when it places them in the
1835 appropriate output sections. The symbol alignments considered are
1836 sixteen-byte or larger, eight-byte, four-byte, two-byte, and one-
1837 byte. This is to prevent gaps between symbols due to alignment
1838 constraints. If no sorting order is specified, then descending
1839 order is assumed.
1840 --sort-section=name
1842 This option will apply "SORT_BY_NAME" to all wildcard section
1843 patterns in the linker script.
1844 --sort-section=alignment
1846 This option will apply "SORT_BY_ALIGNMENT" to all wildcard section
1847 patterns in the linker script.
1848 --spare-dynamic-tags=count
1850 This option specifies the number of empty slots to leave in the
1851 .dynamic section of ELF shared objects. Empty slots may be needed
1852 by post processing tools, such as the prelinker. The default is 5.
1853 --split-by-file[=size]
1855 Similar to --split-by-reloc but creates a new output section for
1856 each input file when size is reached. size defaults to a size of 1
1857 if not given.
1858 --split-by-reloc[=count]
1860 Tries to creates extra sections in the output file so that no
1861 single output section in the file contains more than count
1862 relocations. This is useful when generating huge relocatable files
1863 for downloading into certain real time kernels with the COFF object
1864 file format; since COFF cannot represent more than 65535
1865 relocations in a single section. Note that this will fail to work
1866 with object file formats which do not support arbitrary sections.
1867 The linker will not split up individual input sections for
1868 redistribution, so if a single input section contains more than
1869 count relocations one output section will contain that many
1870 relocations. count defaults to a value of 32768.
1871 --stats
1873 Compute and display statistics about the operation of the linker,
1874 such as execution time and memory usage.
1875 --sysroot=directory
1877 Use directory as the location of the sysroot, overriding the
1878 configure-time default. This option is only supported by linkers
1879 that were configured using --with-sysroot.
1880 --task-link
1882 This is used by COFF/PE based targets to create a task-linked
1883 object file where all of the global symbols have been converted to
1884 statics.
1885 --traditional-format
1887 For some targets, the output of ld is different in some ways from
1888 the output of some existing linker. This switch requests ld to use
1889 the traditional format instead.
1890 For example, on SunOS, ld combines duplicate entries in the symbol
1892 string table. This can reduce the size of an output file with full
1893 debugging information by over 30 percent. Unfortunately, the SunOS
1894 "dbx" program can not read the resulting program ("gdb" has no
1895 trouble). The --traditional-format switch tells ld to not combine
1896 duplicate entries.
1897 --section-start=sectionname=org
1899 Locate a section in the output file at the absolute address given
1900 by org. You may use this option as many times as necessary to
1901 locate multiple sections in the command line. org must be a single
1902 hexadecimal integer; for compatibility with other linkers, you may
1903 omit the leading 0x usually associated with hexadecimal values.
1904 Note: there should be no white space between sectionname, the
1905 equals sign ("="), and org.
1906 -Tbss=org
1908 -Tdata=org
1909 -Ttext=org
1910 Same as --section-start, with ".bss", ".data" or ".text" as the
1911 sectionname.
1912 -Ttext-segment=org
1914 When creating an ELF executable, it will set the address of the
1915 first byte of the text segment.
1916 -Trodata-segment=org
1918 When creating an ELF executable or shared object for a target where
1919 the read-only data is in its own segment separate from the
1920 executable text, it will set the address of the first byte of the
1921 read-only data segment.
1922 -Tldata-segment=org
1924 When creating an ELF executable or shared object for x86-64 medium
1925 memory model, it will set the address of the first byte of the
1926 ldata segment.
1927 --unresolved-symbols=method
1929 Determine how to handle unresolved symbols. There are four
1930 possible values for method:
1931 ignore-all
1933 Do not report any unresolved symbols.
1934 report-all
1936 Report all unresolved symbols. This is the default.
1937 ignore-in-object-files
1939 Report unresolved symbols that are contained in shared
1940 libraries, but ignore them if they come from regular object
1941 files.
1942 ignore-in-shared-libs
1944 Report unresolved symbols that come from regular object files,
1945 but ignore them if they come from shared libraries. This can
1946 be useful when creating a dynamic binary and it is known that
1947 all the shared libraries that it should be referencing are
1948 included on the linker's command line.
1949 The behaviour for shared libraries on their own can also be
1951 controlled by the --[no-]allow-shlib-undefined option.
1952 Normally the linker will generate an error message for each
1954 reported unresolved symbol but the option --warn-unresolved-symbols
1955 can change this to a warning.
1956 --dll-verbose
1958 --verbose[=NUMBER]
1959 Display the version number for ld and list the linker emulations
1960 supported. Display which input files can and cannot be opened.
1961 Display the linker script being used by the linker. If the optional
1962 NUMBER argument > 1, plugin symbol status will also be displayed.
1963 --version-script=version-scriptfile
1965 Specify the name of a version script to the linker. This is
1966 typically used when creating shared libraries to specify additional
1967 information about the version hierarchy for the library being
1968 created. This option is only fully supported on ELF platforms
1969 which support shared libraries; see VERSION. It is partially
1970 supported on PE platforms, which can use version scripts to filter
1971 symbol visibility in auto-export mode: any symbols marked local in
1972 the version script will not be exported.
1973 --warn-common
1975 Warn when a common symbol is combined with another common symbol or
1976 with a symbol definition. Unix linkers allow this somewhat sloppy
1977 practice, but linkers on some other operating systems do not. This
1978 option allows you to find potential problems from combining global
1979 symbols. Unfortunately, some C libraries use this practice, so you
1980 may get some warnings about symbols in the libraries as well as in
1981 your programs.
1982 There are three kinds of global symbols, illustrated here by C
1984 examples:
1985 int i = 1;
1987 A definition, which goes in the initialized data section of the
1988 output file.
1989 extern int i;
1991 An undefined reference, which does not allocate space. There
1992 must be either a definition or a common symbol for the variable
1993 somewhere.
1994 int i;
1996 A common symbol. If there are only (one or more) common
1997 symbols for a variable, it goes in the uninitialized data area
1998 of the output file. The linker merges multiple common symbols
1999 for the same variable into a single symbol. If they are of
2000 different sizes, it picks the largest size. The linker turns a
2001 common symbol into a declaration, if there is a definition of
2002 the same variable.
2003 The --warn-common option can produce five kinds of warnings. Each
2005 warning consists of a pair of lines: the first describes the symbol
2006 just encountered, and the second describes the previous symbol
2007 encountered with the same name. One or both of the two symbols
2008 will be a common symbol.
2009 1. Turning a common symbol into a reference, because there is
2011 already a definition for the symbol.
2012 <file>(<section>): warning: common of `<symbol>'
2014 overridden by definition
2015 <file>(<section>): warning: defined here
2016 2. Turning a common symbol into a reference, because a later
2018 definition for the symbol is encountered. This is the same as
2019 the previous case, except that the symbols are encountered in a
2020 different order.
2021 <file>(<section>): warning: definition of `<symbol>'
2023 overriding common
2024 <file>(<section>): warning: common is here
2025 3. Merging a common symbol with a previous same-sized common
2027 symbol.
2028 <file>(<section>): warning: multiple common
2030 of `<symbol>'
2031 <file>(<section>): warning: previous common is here
2032 4. Merging a common symbol with a previous larger common symbol.
2034 <file>(<section>): warning: common of `<symbol>'
2036 overridden by larger common
2037 <file>(<section>): warning: larger common is here
2038 5. Merging a common symbol with a previous smaller common symbol.
2040 This is the same as the previous case, except that the symbols
2041 are encountered in a different order.
2042 <file>(<section>): warning: common of `<symbol>'
2044 overriding smaller common
2045 <file>(<section>): warning: smaller common is here
2046 --warn-constructors
2048 Warn if any global constructors are used. This is only useful for
2049 a few object file formats. For formats like COFF or ELF, the
2050 linker can not detect the use of global constructors.
2051 --warn-execstack
2053 --no-warn-execstack
2054 On ELF platforms this option controls how the linker generates
2055 warning messages when it creates an output file with an executable
2056 stack. By default the linker will not warn if the -z execstack
2057 command line option has been used, but this behaviour can be
2058 overridden by the --warn-execstack option.
2059 On the other hand the linker will normally warn if the stack is
2061 made executable because one or more of the input files need an
2062 execuable stack and neither of the -z execstack or -z noexecstack
2063 command line options have been specified. This warning can be
2064 disabled via the --no-warn-execstack option.
2065 Note: ELF format input files specify that they need an executable
2067 stack by having a .note.GNU-stack section with the executable bit
2068 set in its section flags. They can specify that they do not need
2069 an executable stack by having that section, but without the
2070 executable flag bit set. If an input file does not have a
2071 .note.GNU-stack section present then the default behaviour is
2072 target specific. For some targets, then absence of such a section
2073 implies that an executable stack is required. This is often a
2074 problem for hand crafted assembler files.
2075 --warn-multiple-gp
2077 Warn if multiple global pointer values are required in the output
2078 file. This is only meaningful for certain processors, such as the
2079 Alpha. Specifically, some processors put large-valued constants in
2080 a special section. A special register (the global pointer) points
2081 into the middle of this section, so that constants can be loaded
2082 efficiently via a base-register relative addressing mode. Since
2083 the offset in base-register relative mode is fixed and relatively
2084 small (e.g., 16 bits), this limits the maximum size of the constant
2085 pool. Thus, in large programs, it is often necessary to use
2086 multiple global pointer values in order to be able to address all
2087 possible constants. This option causes a warning to be issued
2088 whenever this case occurs.
2089 --warn-once
2091 Only warn once for each undefined symbol, rather than once per
2092 module which refers to it.
2093 --warn-rwx-segments
2095 --no-warn-rwx-segments
2096 Warn if the linker creates a loadable, non-zero sized segment that
2097 has all three of the read, write and execute permission flags set.
2098 Such a segment represents a potential security vulnerability. In
2099 addition warnings will be generated if a thread local storage
2100 segment is created with the execute permission flag set, regardless
2101 of whether or not it has the read and/or write flags set.
2102 These warnings are enabled by default. They can be disabled via
2104 the --no-warn-rwx-segments option and re-enabled via the
2105 --warn-rwx-segments option.
2106 --warn-section-align
2108 Warn if the address of an output section is changed because of
2109 alignment. Typically, the alignment will be set by an input
2110 section. The address will only be changed if it not explicitly
2111 specified; that is, if the "SECTIONS" command does not specify a
2112 start address for the section.
2113 --warn-textrel
2115 Warn if the linker adds DT_TEXTREL to a position-independent
2116 executable or shared object.
2117 --warn-alternate-em
2119 Warn if an object has alternate ELF machine code.
2120 --warn-unresolved-symbols
2122 If the linker is going to report an unresolved symbol (see the
2123 option --unresolved-symbols) it will normally generate an error.
2124 This option makes it generate a warning instead.
2125 --error-unresolved-symbols
2127 This restores the linker's default behaviour of generating errors
2128 when it is reporting unresolved symbols.
2129 --whole-archive
2131 For each archive mentioned on the command line after the
2132 --whole-archive option, include every object file in the archive in
2133 the link, rather than searching the archive for the required object
2134 files. This is normally used to turn an archive file into a shared
2135 library, forcing every object to be included in the resulting
2136 shared library. This option may be used more than once.
2137 Two notes when using this option from gcc: First, gcc doesn't know
2139 about this option, so you have to use -Wl,-whole-archive. Second,
2140 don't forget to use -Wl,-no-whole-archive after your list of
2141 archives, because gcc will add its own list of archives to your
2142 link and you may not want this flag to affect those as well.
2143 --wrap=symbol
2145 Use a wrapper function for symbol. Any undefined reference to
2146 symbol will be resolved to "__wrap_symbol". Any undefined
2147 reference to "__real_symbol" will be resolved to symbol.
2148 This can be used to provide a wrapper for a system function. The
2150 wrapper function should be called "__wrap_symbol". If it wishes to
2151 call the system function, it should call "__real_symbol".
2152 Here is a trivial example:
2154 void *
2156 __wrap_malloc (size_t c)
2157 {
2158 printf ("malloc called with %zu\n", c);
2159 return __real_malloc (c);
2160 }
2161 If you link other code with this file using --wrap malloc, then all
2163 calls to "malloc" will call the function "__wrap_malloc" instead.
2164 The call to "__real_malloc" in "__wrap_malloc" will call the real
2165 "malloc" function.
2166 You may wish to provide a "__real_malloc" function as well, so that
2168 links without the --wrap option will succeed. If you do this, you
2169 should not put the definition of "__real_malloc" in the same file
2170 as "__wrap_malloc"; if you do, the assembler may resolve the call
2171 before the linker has a chance to wrap it to "malloc".
2172 Only undefined references are replaced by the linker. So,
2174 translation unit internal references to symbol are not resolved to
2175 "__wrap_symbol". In the next example, the call to "f" in "g" is
2176 not resolved to "__wrap_f".
2177 int
2179 f (void)
2180 {
2181 return 123;
2182 }
2183 int
2185 g (void)
2186 {
2187 return f();
2188 }
2189 --eh-frame-hdr
2191 --no-eh-frame-hdr
2192 Request (--eh-frame-hdr) or suppress (--no-eh-frame-hdr) the
2193 creation of ".eh_frame_hdr" section and ELF "PT_GNU_EH_FRAME"
2194 segment header.
2195 --no-ld-generated-unwind-info
2197 Request creation of ".eh_frame" unwind info for linker generated
2198 code sections like PLT. This option is on by default if linker
2199 generated unwind info is supported.
2200 --enable-new-dtags
2202 --disable-new-dtags
2203 This linker can create the new dynamic tags in ELF. But the older
2204 ELF systems may not understand them. If you specify
2205 --enable-new-dtags, the new dynamic tags will be created as needed
2206 and older dynamic tags will be omitted. If you specify
2207 --disable-new-dtags, no new dynamic tags will be created. By
2208 default, the new dynamic tags are not created. Note that those
2209 options are only available for ELF systems.
2210 --hash-size=number
2212 Set the default size of the linker's hash tables to a prime number
2213 close to number. Increasing this value can reduce the length of
2214 time it takes the linker to perform its tasks, at the expense of
2215 increasing the linker's memory requirements. Similarly reducing
2216 this value can reduce the memory requirements at the expense of
2217 speed.
2218 --hash-style=style
2220 Set the type of linker's hash table(s). style can be either "sysv"
2221 for classic ELF ".hash" section, "gnu" for new style GNU
2222 ".gnu.hash" section or "both" for both the classic ELF ".hash" and
2223 new style GNU ".gnu.hash" hash tables. The default depends upon
2224 how the linker was configured, but for most Linux based systems it
2225 will be "both".
2226 --compress-debug-sections=none
2228 --compress-debug-sections=zlib
2229 --compress-debug-sections=zlib-gnu
2230 --compress-debug-sections=zlib-gabi
2231 On ELF platforms, these options control how DWARF debug sections
2232 are compressed using zlib.
2233 --compress-debug-sections=none doesn't compress DWARF debug
2235 sections. --compress-debug-sections=zlib-gnu compresses DWARF
2236 debug sections and renames them to begin with .zdebug instead of
2237 .debug. --compress-debug-sections=zlib-gabi also compresses DWARF
2238 debug sections, but rather than renaming them it sets the
2239 SHF_COMPRESSED flag in the sections' headers.
2240 The --compress-debug-sections=zlib option is an alias for
2242 --compress-debug-sections=zlib-gabi.
2243 Note that this option overrides any compression in input debug
2245 sections, so if a binary is linked with
2246 --compress-debug-sections=none for example, then any compressed
2247 debug sections in input files will be uncompressed before they are
2248 copied into the output binary.
2249 The default compression behaviour varies depending upon the target
2251 involved and the configure options used to build the toolchain.
2252 The default can be determined by examining the output from the
2253 linker's --help option.
2254 --reduce-memory-overheads
2256 This option reduces memory requirements at ld runtime, at the
2257 expense of linking speed. This was introduced to select the old
2258 O(n^2) algorithm for link map file generation, rather than the new
2259 O(n) algorithm which uses about 40% more memory for symbol storage.
2260 Another effect of the switch is to set the default hash table size
2262 to 1021, which again saves memory at the cost of lengthening the
2263 linker's run time. This is not done however if the --hash-size
2264 switch has been used.
2265 The --reduce-memory-overheads switch may be also be used to enable
2267 other tradeoffs in future versions of the linker.
2268 --max-cache-size=size
2270 ld normally caches the relocation information and symbol tables of
2271 input files in memory with the unlimited size. This option sets
2272 the maximum cache size to size.
2273 --build-id
2275 --build-id=style
2276 Request the creation of a ".note.gnu.build-id" ELF note section or
2277 a ".buildid" COFF section. The contents of the note are unique
2278 bits identifying this linked file. style can be "uuid" to use 128
2279 random bits, "sha1" to use a 160-bit SHA1 hash on the normative
2280 parts of the output contents, "md5" to use a 128-bit MD5 hash on
2281 the normative parts of the output contents, or "0xhexstring" to use
2282 a chosen bit string specified as an even number of hexadecimal
2283 digits ("-" and ":" characters between digit pairs are ignored).
2284 If style is omitted, "sha1" is used.
2285 The "md5" and "sha1" styles produces an identifier that is always
2287 the same in an identical output file, but will be unique among all
2288 nonidentical output files. It is not intended to be compared as a
2289 checksum for the file's contents. A linked file may be changed
2290 later by other tools, but the build ID bit string identifying the
2291 original linked file does not change.
2292 Passing "none" for style disables the setting from any "--build-id"
2294 options earlier on the command line.
2295 --package-metadata=JSON
2297 Request the creation of a ".note.package" ELF note section. The
2298 contents of the note are in JSON format, as per the package
2299 metadata specification. For more information see:
2300 https://systemd.io/ELF_PACKAGE_METADATA/ If the JSON argument is
2301 missing/empty then this will disable the creation of the metadata
2302 note, if one had been enabled by an earlier occurrence of the
2303 --package-metdata option. If the linker has been built with
2304 libjansson, then the JSON string will be validated.
2305 The i386 PE linker supports the -shared option, which causes the output
2307 to be a dynamically linked library (DLL) instead of a normal
2308 executable. You should name the output "*.dll" when you use this
2309 option. In addition, the linker fully supports the standard "*.def"
2310 files, which may be specified on the linker command line like an object
2311 file (in fact, it should precede archives it exports symbols from, to
2312 ensure that they get linked in, just like a normal object file).
2313 In addition to the options common to all targets, the i386 PE linker
2315 support additional command-line options that are specific to the i386
2316 PE target. Options that take values may be separated from their values
2317 by either a space or an equals sign.
2318 --add-stdcall-alias
2320 If given, symbols with a stdcall suffix (@nn) will be exported as-
2321 is and also with the suffix stripped. [This option is specific to
2322 the i386 PE targeted port of the linker]
2323 --base-file file
2325 Use file as the name of a file in which to save the base addresses
2326 of all the relocations needed for generating DLLs with dlltool.
2327 [This is an i386 PE specific option]
2328 --dll
2330 Create a DLL instead of a regular executable. You may also use
2331 -shared or specify a "LIBRARY" in a given ".def" file. [This
2332 option is specific to the i386 PE targeted port of the linker]
2333 --enable-long-section-names
2335 --disable-long-section-names
2336 The PE variants of the COFF object format add an extension that
2337 permits the use of section names longer than eight characters, the
2338 normal limit for COFF. By default, these names are only allowed in
2339 object files, as fully-linked executable images do not carry the
2340 COFF string table required to support the longer names. As a GNU
2341 extension, it is possible to allow their use in executable images
2342 as well, or to (probably pointlessly!) disallow it in object
2343 files, by using these two options. Executable images generated
2344 with these long section names are slightly non-standard, carrying
2345 as they do a string table, and may generate confusing output when
2346 examined with non-GNU PE-aware tools, such as file viewers and
2347 dumpers. However, GDB relies on the use of PE long section names
2348 to find Dwarf-2 debug information sections in an executable image
2349 at runtime, and so if neither option is specified on the command-
2350 line, ld will enable long section names, overriding the default and
2351 technically correct behaviour, when it finds the presence of debug
2352 information while linking an executable image and not stripping
2353 symbols. [This option is valid for all PE targeted ports of the
2354 linker]
2355 --enable-stdcall-fixup
2357 --disable-stdcall-fixup
2358 If the link finds a symbol that it cannot resolve, it will attempt
2359 to do "fuzzy linking" by looking for another defined symbol that
2360 differs only in the format of the symbol name (cdecl vs stdcall)
2361 and will resolve that symbol by linking to the match. For example,
2362 the undefined symbol "_foo" might be linked to the function
2363 "_foo@12", or the undefined symbol "_bar@16" might be linked to the
2364 function "_bar". When the linker does this, it prints a warning,
2365 since it normally should have failed to link, but sometimes import
2366 libraries generated from third-party dlls may need this feature to
2367 be usable. If you specify --enable-stdcall-fixup, this feature is
2368 fully enabled and warnings are not printed. If you specify
2369 --disable-stdcall-fixup, this feature is disabled and such
2370 mismatches are considered to be errors. [This option is specific
2371 to the i386 PE targeted port of the linker]
2372 --leading-underscore
2374 --no-leading-underscore
2375 For most targets default symbol-prefix is an underscore and is
2376 defined in target's description. By this option it is possible to
2377 disable/enable the default underscore symbol-prefix.
2378 --export-all-symbols
2380 If given, all global symbols in the objects used to build a DLL
2381 will be exported by the DLL. Note that this is the default if
2382 there otherwise wouldn't be any exported symbols. When symbols are
2383 explicitly exported via DEF files or implicitly exported via
2384 function attributes, the default is to not export anything else
2385 unless this option is given. Note that the symbols "DllMain@12",
2386 "DllEntryPoint@0", "DllMainCRTStartup@12", and "impure_ptr" will
2387 not be automatically exported. Also, symbols imported from other
2388 DLLs will not be re-exported, nor will symbols specifying the DLL's
2389 internal layout such as those beginning with "_head_" or ending
2390 with "_iname". In addition, no symbols from "libgcc", "libstd++",
2391 "libmingw32", or "crtX.o" will be exported. Symbols whose names
2392 begin with "__rtti_" or "__builtin_" will not be exported, to help
2393 with C++ DLLs. Finally, there is an extensive list of cygwin-
2394 private symbols that are not exported (obviously, this applies on
2395 when building DLLs for cygwin targets). These cygwin-excludes are:
2396 "_cygwin_dll_entry@12", "_cygwin_crt0_common@8",
2397 "_cygwin_noncygwin_dll_entry@12", "_fmode", "_impure_ptr",
2398 "cygwin_attach_dll", "cygwin_premain0", "cygwin_premain1",
2399 "cygwin_premain2", "cygwin_premain3", and "environ". [This option
2400 is specific to the i386 PE targeted port of the linker]
2401 --exclude-symbols symbol,symbol,...
2403 Specifies a list of symbols which should not be automatically
2404 exported. The symbol names may be delimited by commas or colons.
2405 [This option is specific to the i386 PE targeted port of the
2406 linker]
2407 --exclude-all-symbols
2409 Specifies no symbols should be automatically exported. [This
2410 option is specific to the i386 PE targeted port of the linker]
2411 --file-alignment
2413 Specify the file alignment. Sections in the file will always begin
2414 at file offsets which are multiples of this number. This defaults
2415 to 512. [This option is specific to the i386 PE targeted port of
2416 the linker]
2417 --heap reserve
2419 --heap reserve,commit
2420 Specify the number of bytes of memory to reserve (and optionally
2421 commit) to be used as heap for this program. The default is 1MB
2422 reserved, 4K committed. [This option is specific to the i386 PE
2423 targeted port of the linker]
2424 --image-base value
2426 Use value as the base address of your program or dll. This is the
2427 lowest memory location that will be used when your program or dll
2428 is loaded. To reduce the need to relocate and improve performance
2429 of your dlls, each should have a unique base address and not
2430 overlap any other dlls. The default is 0x400000 for executables,
2431 and 0x10000000 for dlls. [This option is specific to the i386 PE
2432 targeted port of the linker]
2433 --kill-at
2435 If given, the stdcall suffixes (@nn) will be stripped from symbols
2436 before they are exported. [This option is specific to the i386 PE
2437 targeted port of the linker]
2438 --large-address-aware
2440 If given, the appropriate bit in the "Characteristics" field of the
2441 COFF header is set to indicate that this executable supports
2442 virtual addresses greater than 2 gigabytes. This should be used in
2443 conjunction with the /3GB or /USERVA=value megabytes switch in the
2444 "[operating systems]" section of the BOOT.INI. Otherwise, this bit
2445 has no effect. [This option is specific to PE targeted ports of
2446 the linker]
2447 --disable-large-address-aware
2449 Reverts the effect of a previous --large-address-aware option.
2450 This is useful if --large-address-aware is always set by the
2451 compiler driver (e.g. Cygwin gcc) and the executable does not
2452 support virtual addresses greater than 2 gigabytes. [This option
2453 is specific to PE targeted ports of the linker]
2454 --major-image-version value
2456 Sets the major number of the "image version". Defaults to 1.
2457 [This option is specific to the i386 PE targeted port of the
2458 linker]
2459 --major-os-version value
2461 Sets the major number of the "os version". Defaults to 4. [This
2462 option is specific to the i386 PE targeted port of the linker]
2463 --major-subsystem-version value
2465 Sets the major number of the "subsystem version". Defaults to 4.
2466 [This option is specific to the i386 PE targeted port of the
2467 linker]
2468 --minor-image-version value
2470 Sets the minor number of the "image version". Defaults to 0.
2471 [This option is specific to the i386 PE targeted port of the
2472 linker]
2473 --minor-os-version value
2475 Sets the minor number of the "os version". Defaults to 0. [This
2476 option is specific to the i386 PE targeted port of the linker]
2477 --minor-subsystem-version value
2479 Sets the minor number of the "subsystem version". Defaults to 0.
2480 [This option is specific to the i386 PE targeted port of the
2481 linker]
2482 --output-def file
2484 The linker will create the file file which will contain a DEF file
2485 corresponding to the DLL the linker is generating. This DEF file
2486 (which should be called "*.def") may be used to create an import
2487 library with "dlltool" or may be used as a reference to
2488 automatically or implicitly exported symbols. [This option is
2489 specific to the i386 PE targeted port of the linker]
2490 --enable-auto-image-base
2492 --enable-auto-image-base=value
2493 Automatically choose the image base for DLLs, optionally starting
2494 with base value, unless one is specified using the "--image-base"
2495 argument. By using a hash generated from the dllname to create
2496 unique image bases for each DLL, in-memory collisions and
2497 relocations which can delay program execution are avoided. [This
2498 option is specific to the i386 PE targeted port of the linker]
2499 --disable-auto-image-base
2501 Do not automatically generate a unique image base. If there is no
2502 user-specified image base ("--image-base") then use the platform
2503 default. [This option is specific to the i386 PE targeted port of
2504 the linker]
2505 --dll-search-prefix string
2507 When linking dynamically to a dll without an import library, search
2508 for "<string><basename>.dll" in preference to "lib<basename>.dll".
2509 This behaviour allows easy distinction between DLLs built for the
2510 various "subplatforms": native, cygwin, uwin, pw, etc. For
2511 instance, cygwin DLLs typically use "--dll-search-prefix=cyg".
2512 [This option is specific to the i386 PE targeted port of the
2513 linker]
2514 --enable-auto-import
2516 Do sophisticated linking of "_symbol" to "__imp__symbol" for DATA
2517 imports from DLLs, thus making it possible to bypass the dllimport
2518 mechanism on the user side and to reference unmangled symbol names.
2519 [This option is specific to the i386 PE targeted port of the
2520 linker]
2521 The following remarks pertain to the original implementation of the
2523 feature and are obsolete nowadays for Cygwin and MinGW targets.
2524 Note: Use of the 'auto-import' extension will cause the text
2526 section of the image file to be made writable. This does not
2527 conform to the PE-COFF format specification published by Microsoft.
2528 Note - use of the 'auto-import' extension will also cause read only
2530 data which would normally be placed into the .rdata section to be
2531 placed into the .data section instead. This is in order to work
2532 around a problem with consts that is described here:
2533 http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
2534 Using 'auto-import' generally will 'just work' -- but sometimes you
2536 may see this message:
2537 "variable '<var>' can't be auto-imported. Please read the
2539 documentation for ld's "--enable-auto-import" for details."
2540 This message occurs when some (sub)expression accesses an address
2542 ultimately given by the sum of two constants (Win32 import tables
2543 only allow one). Instances where this may occur include accesses
2544 to member fields of struct variables imported from a DLL, as well
2545 as using a constant index into an array variable imported from a
2546 DLL. Any multiword variable (arrays, structs, long long, etc) may
2547 trigger this error condition. However, regardless of the exact
2548 data type of the offending exported variable, ld will always detect
2549 it, issue the warning, and exit.
2550 There are several ways to address this difficulty, regardless of
2552 the data type of the exported variable:
2553 One way is to use --enable-runtime-pseudo-reloc switch. This leaves
2555 the task of adjusting references in your client code for runtime
2556 environment, so this method works only when runtime environment
2557 supports this feature.
2558 A second solution is to force one of the 'constants' to be a
2560 variable -- that is, unknown and un-optimizable at compile time.
2561 For arrays, there are two possibilities: a) make the indexee (the
2562 array's address) a variable, or b) make the 'constant' index a
2563 variable. Thus:
2564 extern type extern_array[];
2566 extern_array[1] -->
2567 { volatile type *t=extern_array; t[1] }
2568 or
2570 extern type extern_array[];
2572 extern_array[1] -->
2573 { volatile int t=1; extern_array[t] }
2574 For structs (and most other multiword data types) the only option
2576 is to make the struct itself (or the long long, or the ...)
2577 variable:
2578 extern struct s extern_struct;
2580 extern_struct.field -->
2581 { volatile struct s *t=&extern_struct; t->field }
2582 or
2584 extern long long extern_ll;
2586 extern_ll -->
2587 { volatile long long * local_ll=&extern_ll; *local_ll }
2588 A third method of dealing with this difficulty is to abandon
2590 'auto-import' for the offending symbol and mark it with
2591 "__declspec(dllimport)". However, in practice that requires using
2592 compile-time #defines to indicate whether you are building a DLL,
2593 building client code that will link to the DLL, or merely
2594 building/linking to a static library. In making the choice
2595 between the various methods of resolving the 'direct address with
2596 constant offset' problem, you should consider typical real-world
2597 usage:
2598 Original:
2600 --foo.h
2602 extern int arr[];
2603 --foo.c
2604 #include "foo.h"
2605 void main(int argc, char **argv){
2606 printf("%d\n",arr[1]);
2607 }
2608 Solution 1:
2610 --foo.h
2612 extern int arr[];
2613 --foo.c
2614 #include "foo.h"
2615 void main(int argc, char **argv){
2616 /* This workaround is for win32 and cygwin; do not "optimize" */
2617 volatile int *parr = arr;
2618 printf("%d\n",parr[1]);
2619 }
2620 Solution 2:
2622 --foo.h
2624 /* Note: auto-export is assumed (no __declspec(dllexport)) */
2625 #if (defined(_WIN32) || defined(__CYGWIN__)) && \
2626 !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
2627 #define FOO_IMPORT __declspec(dllimport)
2628 #else
2629 #define FOO_IMPORT
2630 #endif
2631 extern FOO_IMPORT int arr[];
2632 --foo.c
2633 #include "foo.h"
2634 void main(int argc, char **argv){
2635 printf("%d\n",arr[1]);
2636 }
2637 A fourth way to avoid this problem is to re-code your library to
2639 use a functional interface rather than a data interface for the
2640 offending variables (e.g. set_foo() and get_foo() accessor
2641 functions).
2642 --disable-auto-import
2644 Do not attempt to do sophisticated linking of "_symbol" to
2645 "__imp__symbol" for DATA imports from DLLs. [This option is
2646 specific to the i386 PE targeted port of the linker]
2647 --enable-runtime-pseudo-reloc
2649 If your code contains expressions described in --enable-auto-import
2650 section, that is, DATA imports from DLL with non-zero offset, this
2651 switch will create a vector of 'runtime pseudo relocations' which
2652 can be used by runtime environment to adjust references to such
2653 data in your client code. [This option is specific to the i386 PE
2654 targeted port of the linker]
2655 --disable-runtime-pseudo-reloc
2657 Do not create pseudo relocations for non-zero offset DATA imports
2658 from DLLs. [This option is specific to the i386 PE targeted port
2659 of the linker]
2660 --enable-extra-pe-debug
2662 Show additional debug info related to auto-import symbol thunking.
2663 [This option is specific to the i386 PE targeted port of the
2664 linker]
2665 --section-alignment
2667 Sets the section alignment. Sections in memory will always begin
2668 at addresses which are a multiple of this number. Defaults to
2669 0x1000. [This option is specific to the i386 PE targeted port of
2670 the linker]
2671 --stack reserve
2673 --stack reserve,commit
2674 Specify the number of bytes of memory to reserve (and optionally
2675 commit) to be used as stack for this program. The default is 2MB
2676 reserved, 4K committed. [This option is specific to the i386 PE
2677 targeted port of the linker]
2678 --subsystem which
2680 --subsystem which:major
2681 --subsystem which:major.minor
2682 Specifies the subsystem under which your program will execute. The
2683 legal values for which are "native", "windows", "console", "posix",
2684 and "xbox". You may optionally set the subsystem version also.
2685 Numeric values are also accepted for which. [This option is
2686 specific to the i386 PE targeted port of the linker]
2687 The following options set flags in the "DllCharacteristics" field
2689 of the PE file header: [These options are specific to PE targeted
2690 ports of the linker]
2691 --high-entropy-va
2693 --disable-high-entropy-va
2694 Image is compatible with 64-bit address space layout randomization
2695 (ASLR). This option is enabled by default for 64-bit PE images.
2696 This option also implies --dynamicbase and --enable-reloc-section.
2698 --dynamicbase
2700 --disable-dynamicbase
2701 The image base address may be relocated using address space layout
2702 randomization (ASLR). This feature was introduced with MS Windows
2703 Vista for i386 PE targets. This option is enabled by default but
2704 can be disabled via the --disable-dynamicbase option. This option
2705 also implies --enable-reloc-section.
2706 --forceinteg
2708 --disable-forceinteg
2709 Code integrity checks are enforced. This option is disabled by
2710 default.
2711 --nxcompat
2713 --disable-nxcompat
2714 The image is compatible with the Data Execution Prevention. This
2715 feature was introduced with MS Windows XP SP2 for i386 PE targets.
2716 The option is enabled by default.
2717 --no-isolation
2719 --disable-no-isolation
2720 Although the image understands isolation, do not isolate the image.
2721 This option is disabled by default.
2722 --no-seh
2724 --disable-no-seh
2725 The image does not use SEH. No SE handler may be called from this
2726 image. This option is disabled by default.
2727 --no-bind
2729 --disable-no-bind
2730 Do not bind this image. This option is disabled by default.
2731 --wdmdriver
2733 --disable-wdmdriver
2734 The driver uses the MS Windows Driver Model. This option is
2735 disabled by default.
2736 --tsaware
2738 --disable-tsaware
2739 The image is Terminal Server aware. This option is disabled by
2740 default.
2741 --insert-timestamp
2743 --no-insert-timestamp
2744 Insert a real timestamp into the image. This is the default
2745 behaviour as it matches legacy code and it means that the image
2746 will work with other, proprietary tools. The problem with this
2747 default is that it will result in slightly different images being
2748 produced each time the same sources are linked. The option
2749 --no-insert-timestamp can be used to insert a zero value for the
2750 timestamp, this ensuring that binaries produced from identical
2751 sources will compare identically.
2752 --enable-reloc-section
2754 --disable-reloc-section
2755 Create the base relocation table, which is necessary if the image
2756 is loaded at a different image base than specified in the PE
2757 header. This option is enabled by default.
2758 The C6X uClinux target uses a binary format called DSBT to support
2760 shared libraries. Each shared library in the system needs to have a
2761 unique index; all executables use an index of 0.
2762 --dsbt-size size
2764 This option sets the number of entries in the DSBT of the current
2765 executable or shared library to size. The default is to create a
2766 table with 64 entries.
2767 --dsbt-index index
2769 This option sets the DSBT index of the current executable or shared
2770 library to index. The default is 0, which is appropriate for
2771 generating executables. If a shared library is generated with a
2772 DSBT index of 0, the "R_C6000_DSBT_INDEX" relocs are copied into
2773 the output file.
2774 The --no-merge-exidx-entries switch disables the merging of
2776 adjacent exidx entries in frame unwind info.
2777 --branch-stub
2779 This option enables linker branch relaxation by inserting branch
2780 stub sections when needed to extend the range of branches. This
2781 option is usually not required since C-SKY supports branch and call
2782 instructions that can access the full memory range and branch
2783 relaxation is normally handled by the compiler or assembler.
2784 --stub-group-size=N
2786 This option allows finer control of linker branch stub creation.
2787 It sets the maximum size of a group of input sections that can be
2788 handled by one stub section. A negative value of N locates stub
2789 sections after their branches, while a positive value allows stub
2790 sections to appear either before or after the branches. Values of
2791 1 or -1 indicate that the linker should choose suitable defaults.
2792 The 68HC11 and 68HC12 linkers support specific options to control the
2794 memory bank switching mapping and trampoline code generation.
2795 --no-trampoline
2797 This option disables the generation of trampoline. By default a
2798 trampoline is generated for each far function which is called using
2799 a "jsr" instruction (this happens when a pointer to a far function
2800 is taken).
2801 --bank-window name
2803 This option indicates to the linker the name of the memory region
2804 in the MEMORY specification that describes the memory bank window.
2805 The definition of such region is then used by the linker to compute
2806 paging and addresses within the memory window.
2807 The following options are supported to control handling of GOT
2809 generation when linking for 68K targets.
2810 --got=type
2812 This option tells the linker which GOT generation scheme to use.
2813 type should be one of single, negative, multigot or target. For
2814 more information refer to the Info entry for ld.
2815 The following options are supported to control microMIPS instruction
2817 generation and branch relocation checks for ISA mode transitions when
2818 linking for MIPS targets.
2819 --insn32
2821 --no-insn32
2822 These options control the choice of microMIPS instructions used in
2823 code generated by the linker, such as that in the PLT or lazy
2824 binding stubs, or in relaxation. If --insn32 is used, then the
2825 linker only uses 32-bit instruction encodings. By default or if
2826 --no-insn32 is used, all instruction encodings are used, including
2827 16-bit ones where possible.
2828 --ignore-branch-isa
2830 --no-ignore-branch-isa
2831 These options control branch relocation checks for invalid ISA mode
2832 transitions. If --ignore-branch-isa is used, then the linker
2833 accepts any branch relocations and any ISA mode transition required
2834 is lost in relocation calculation, except for some cases of "BAL"
2835 instructions which meet relaxation conditions and are converted to
2836 equivalent "JALX" instructions as the associated relocation is
2837 calculated. By default or if --no-ignore-branch-isa is used a
2838 check is made causing the loss of an ISA mode transition to produce
2839 an error.
2840 --compact-branches
2842 --no-compact-branches
2843 These options control the generation of compact instructions by the
2844 linker in the PLT entries for MIPS R6.
2845 For the pdp11-aout target, three variants of the output format can be
2847 produced as selected by the following options. The default variant for
2848 pdp11-aout is the --omagic option, whereas for other targets --nmagic
2849 is the default. The --imagic option is defined only for the pdp11-aout
2850 target, while the others are described here as they apply to the
2851 pdp11-aout target.
2852 -N
2854 --omagic
2855 Mark the output as "OMAGIC" (0407) in the a.out header to indicate
2856 that the text segment is not to be write-protected and shared.
2857 Since the text and data sections are both readable and writable,
2858 the data section is allocated immediately contiguous after the text
2859 segment. This is the oldest format for PDP11 executable programs
2860 and is the default for ld on PDP11 Unix systems from the beginning
2861 through 2.11BSD.
2862 -n
2864 --nmagic
2865 Mark the output as "NMAGIC" (0410) in the a.out header to indicate
2866 that when the output file is executed, the text portion will be
2867 read-only and shareable among all processes executing the same
2868 file. This involves moving the data areas up to the first possible
2869 8K byte page boundary following the end of the text. This option
2870 creates a pure executable format.
2871 -z
2873 --imagic
2874 Mark the output as "IMAGIC" (0411) in the a.out header to indicate
2875 that when the output file is executed, the program text and data
2876 areas will be loaded into separate address spaces using the split
2877 instruction and data space feature of the memory management unit in
2878 larger models of the PDP11. This doubles the address space
2879 available to the program. The text segment is again pure, write-
2880 protected, and shareable. The only difference in the output format
2881 between this option and the others, besides the magic number, is
2882 that both the text and data sections start at location 0. The -z
2883 option selected this format in 2.11BSD. This option creates a
2884 separate executable format.
2885 --no-omagic
2887 Equivalent to --nmagic for pdp11-aout.
2888
2890 You can change the behaviour of ld with the environment variables
2891 "GNUTARGET", "LDEMULATION" and "COLLECT_NO_DEMANGLE".
2892 "GNUTARGET" determines the input-file object format if you don't use -b
2894 (or its synonym --format). Its value should be one of the BFD names
2895 for an input format. If there is no "GNUTARGET" in the environment, ld
2896 uses the natural format of the target. If "GNUTARGET" is set to
2897 "default" then BFD attempts to discover the input format by examining
2898 binary input files; this method often succeeds, but there are potential
2899 ambiguities, since there is no method of ensuring that the magic number
2900 used to specify object-file formats is unique. However, the
2901 configuration procedure for BFD on each system places the conventional
2902 format for that system first in the search-list, so ambiguities are
2903 resolved in favor of convention.
2904 "LDEMULATION" determines the default emulation if you don't use the -m
2906 option. The emulation can affect various aspects of linker behaviour,
2907 particularly the default linker script. You can list the available
2908 emulations with the --verbose or -V options. If the -m option is not
2909 used, and the "LDEMULATION" environment variable is not defined, the
2910 default emulation depends upon how the linker was configured.
2911 Normally, the linker will default to demangling symbols. However, if
2913 "COLLECT_NO_DEMANGLE" is set in the environment, then it will default
2914 to not demangling symbols. This environment variable is used in a
2915 similar fashion by the "gcc" linker wrapper program. The default may
2916 be overridden by the --demangle and --no-demangle options.
2917
2919 ar(1), nm(1), objcopy(1), objdump(1), readelf(1) and the Info entries
2920 for binutils and ld.
2921
2923 Copyright (c) 1991-2022 Free Software Foundation, Inc.
2924 Permission is granted to copy, distribute and/or modify this document
2926 under the terms of the GNU Free Documentation License, Version 1.3 or
2927 any later version published by the Free Software Foundation; with no
2928 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
2929 Texts. A copy of the license is included in the section entitled "GNU
2930 Free Documentation License".
2931binutils-2.39 2022-08-05 LD(1)