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132 .\" ========================================================================
135 .TH LD 1 "2002-05-11" "binutils-2.12.1" "GNU Development Tools"
138 ld \- Using \s-1LD\s0, the \s-1GNU\s0 linker
140 .IX Header "SYNOPSIS"
141 ld [\fBoptions\fR] \fIobjfile\fR ...
143 .IX Header "DESCRIPTION"
144 \&\fBld\fR combines a number of object and archive files, relocates
145 their data and ties up symbol references. Usually the last step in
146 compiling a program is to run \fBld\fR.
148 \&\fBld\fR accepts Linker Command Language files written in
149 a superset of \s-1AT&T\s0's Link Editor Command Language syntax,
150 to provide explicit and total control over the linking process.
152 This man page does not describe the command language; see the
153 \&\fBld\fR entry in \f(CW\*(C`info\*(C'\fR, or the manual
154 ld: the \s-1GNU\s0 linker, for full details on the command language and
155 on other aspects of the \s-1GNU\s0 linker.
157 This version of \fBld\fR uses the general purpose \s-1BFD\s0 libraries
158 to operate on object files. This allows \fBld\fR to read, combine, and
159 write object files in many different formats\-\-\-for example, \s-1COFF\s0 or
160 \&\f(CW\*(C`a.out\*(C'\fR. Different formats may be linked together to produce any
161 available kind of object file.
163 Aside from its flexibility, the \s-1GNU\s0 linker is more helpful than other
164 linkers in providing diagnostic information. Many linkers abandon
165 execution immediately upon encountering an error; whenever possible,
166 \&\fBld\fR continues executing, allowing you to identify other errors
167 (or, in some cases, to get an output file in spite of the error).
169 The \s-1GNU\s0 linker \fBld\fR is meant to cover a broad range of situations,
170 and to be as compatible as possible with other linkers. As a result,
171 you have many choices to control its behavior.
174 The linker supports a plethora of command-line options, but in actual
175 practice few of them are used in any particular context.
176 For instance, a frequent use of \fBld\fR is to link standard Unix
177 object files on a standard, supported Unix system. On such a system, to
178 link a file \f(CW\*(C`hello.o\*(C'\fR:
181 \& ld -o I<output> /lib/crt0.o hello.o -lc
183 This tells \fBld\fR to produce a file called \fIoutput\fR as the
184 result of linking the file \f(CW\*(C`/lib/crt0.o\*(C'\fR with \f(CW\*(C`hello.o\*(C'\fR and
185 the library \f(CW\*(C`libc.a\*(C'\fR, which will come from the standard search
186 directories. (See the discussion of the \fB\-l\fR option below.)
188 Some of the command-line options to \fBld\fR may be specified at any
189 point in the command line. However, options which refer to files, such
190 as \fB\-l\fR or \fB\-T\fR, cause the file to be read at the point at
191 which the option appears in the command line, relative to the object
192 files and other file options. Repeating non-file options with a
193 different argument will either have no further effect, or override prior
194 occurrences (those further to the left on the command line) of that
195 option. Options which may be meaningfully specified more than once are
196 noted in the descriptions below.
198 Non-option arguments are object files or archives which are to be linked
199 together. They may follow, precede, or be mixed in with command-line
200 options, except that an object file argument may not be placed between
201 an option and its argument.
203 Usually the linker is invoked with at least one object file, but you can
204 specify other forms of binary input files using \fB\-l\fR, \fB\-R\fR,
205 and the script command language. If \fIno\fR binary input files at all
206 are specified, the linker does not produce any output, and issues the
207 message \fBNo input files\fR.
209 If the linker can not recognize the format of an object file, it will
210 assume that it is a linker script. A script specified in this way
211 augments the main linker script used for the link (either the default
212 linker script or the one specified by using \fB\-T\fR). This feature
213 permits the linker to link against a file which appears to be an object
214 or an archive, but actually merely defines some symbol values, or uses
215 \&\f(CW\*(C`INPUT\*(C'\fR or \f(CW\*(C`GROUP\*(C'\fR to load other objects. Note that
216 specifying a script in this way merely augments the main linker script;
217 use the \fB\-T\fR option to replace the default linker script entirely.
219 For options whose names are a single letter,
220 option arguments must either follow the option letter without intervening
221 whitespace, or be given as separate arguments immediately following the
222 option that requires them.
224 For options whose names are multiple letters, either one dash or two can
225 precede the option name; for example, \fB\-trace\-symbol\fR and
226 \&\fB\-\-trace\-symbol\fR are equivalent. Note \- there is one exception to
227 this rule. Multiple letter options that start with a lower case 'o' can
228 only be preceeded by two dashes. This is to reduce confusion with the
229 \&\fB\-o\fR option. So for example \fB\-omagic\fR sets the output file
230 name to \fBmagic\fR whereas \fB\-\-omagic\fR sets the \s-1NMAGIC\s0 flag on the
233 Arguments to multiple-letter options must either be separated from the
234 option name by an equals sign, or be given as separate arguments
235 immediately following the option that requires them. For example,
236 \&\fB\-\-trace\-symbol foo\fR and \fB\-\-trace\-symbol=foo\fR are equivalent.
237 Unique abbreviations of the names of multiple-letter options are
240 Note \- if the linker is being invoked indirectly, via a compiler driver
241 (eg \fBgcc\fR) then all the linker command line options should be
242 prefixed by \fB\-Wl,\fR (or whatever is appropriate for the particular
243 compiler driver) like this:
246 \& gcc -Wl,--startgroup foo.o bar.o -Wl,--endgroup
248 This is important, because otherwise the compiler driver program may
249 silently drop the linker options, resulting in a bad link.
251 Here is a table of the generic command line switches accepted by the \s-1GNU\s0
253 .IP "\fB\-a\fR\fIkeyword\fR" 4
255 This option is supported for \s-1HP/UX\s0 compatibility. The \fIkeyword\fR
256 argument must be one of the strings \fBarchive\fR, \fBshared\fR, or
257 \&\fBdefault\fR. \fB\-aarchive\fR is functionally equivalent to
258 \&\fB\-Bstatic\fR, and the other two keywords are functionally equivalent
259 to \fB\-Bdynamic\fR. This option may be used any number of times.
260 .IP "\fB\-A\fR\fIarchitecture\fR" 4
261 .IX Item "-Aarchitecture"
263 .IP "\fB\-\-architecture=\fR\fIarchitecture\fR" 4
264 .IX Item "--architecture=architecture"
266 In the current release of \fBld\fR, this option is useful only for the
267 Intel 960 family of architectures. In that \fBld\fR configuration, the
268 \&\fIarchitecture\fR argument identifies the particular architecture in
269 the 960 family, enabling some safeguards and modifying the
270 archive-library search path.
272 Future releases of \fBld\fR may support similar functionality for
273 other architecture families.
274 .IP "\fB\-b\fR \fIinput-format\fR" 4
275 .IX Item "-b input-format"
277 .IP "\fB\-\-format=\fR\fIinput-format\fR" 4
278 .IX Item "--format=input-format"
280 \&\fBld\fR may be configured to support more than one kind of object
281 file. If your \fBld\fR is configured this way, you can use the
282 \&\fB\-b\fR option to specify the binary format for input object files
283 that follow this option on the command line. Even when \fBld\fR is
284 configured to support alternative object formats, you don't usually need
285 to specify this, as \fBld\fR should be configured to expect as a
286 default input format the most usual format on each machine.
287 \&\fIinput-format\fR is a text string, the name of a particular format
288 supported by the \s-1BFD\s0 libraries. (You can list the available binary
289 formats with \fBobjdump \-i\fR.)
291 You may want to use this option if you are linking files with an unusual
292 binary format. You can also use \fB\-b\fR to switch formats explicitly (when
293 linking object files of different formats), by including
294 \&\fB\-b\fR \fIinput-format\fR before each group of object files in a
297 The default format is taken from the environment variable
298 \&\f(CW\*(C`GNUTARGET\*(C'\fR.
300 You can also define the input format from a script, using the command
301 \&\f(CW\*(C`TARGET\*(C'\fR;
302 .IP "\fB\-c\fR \fIMRI-commandfile\fR" 4
303 .IX Item "-c MRI-commandfile"
305 .IP "\fB\-\-mri\-script=\fR\fIMRI-commandfile\fR" 4
306 .IX Item "--mri-script=MRI-commandfile"
308 For compatibility with linkers produced by \s-1MRI\s0, \fBld\fR accepts script
309 files written in an alternate, restricted command language, described in
310 the \s-1MRI\s0 Compatible Script Files section of \s-1GNU\s0 ld documentation.
311 Introduce \s-1MRI\s0 script files with
312 the option \fB\-c\fR; use the \fB\-T\fR option to run linker
313 scripts written in the general-purpose \fBld\fR scripting language.
314 If \fIMRI-cmdfile\fR does not exist, \fBld\fR looks for it in the directories
315 specified by any \fB\-L\fR options.
324 These three options are equivalent; multiple forms are supported for
325 compatibility with other linkers. They assign space to common symbols
326 even if a relocatable output file is specified (with \fB\-r\fR). The
327 script command \f(CW\*(C`FORCE_COMMON_ALLOCATION\*(C'\fR has the same effect.
328 .IP "\fB\-e\fR \fIentry\fR" 4
331 .IP "\fB\-\-entry=\fR\fIentry\fR" 4
332 .IX Item "--entry=entry"
334 Use \fIentry\fR as the explicit symbol for beginning execution of your
335 program, rather than the default entry point. If there is no symbol
336 named \fIentry\fR, the linker will try to parse \fIentry\fR as a number,
337 and use that as the entry address (the number will be interpreted in
338 base 10; you may use a leading \fB0x\fR for base 16, or a leading
339 \&\fB0\fR for base 8).
343 .IP "\fB\-\-export\-dynamic\fR" 4
344 .IX Item "--export-dynamic"
346 When creating a dynamically linked executable, add all symbols to the
347 dynamic symbol table. The dynamic symbol table is the set of symbols
348 which are visible from dynamic objects at run time.
350 If you do not use this option, the dynamic symbol table will normally
351 contain only those symbols which are referenced by some dynamic object
352 mentioned in the link.
354 If you use \f(CW\*(C`dlopen\*(C'\fR to load a dynamic object which needs to refer
355 back to the symbols defined by the program, rather than some other
356 dynamic object, then you will probably need to use this option when
357 linking the program itself.
359 You can also use the version script to control what symbols should
360 be added to the dynamic symbol table if the output format supports it.
361 See the description of \fB\-\-version\-script\fR in \f(CW@ref\fR{\s-1VERSION\s0}.
364 Link big-endian objects. This affects the default output format.
367 Link little-endian objects. This affects the default output format.
371 .IP "\fB\-\-auxiliary\fR \fIname\fR" 4
372 .IX Item "--auxiliary name"
374 When creating an \s-1ELF\s0 shared object, set the internal \s-1DT_AUXILIARY\s0 field
375 to the specified name. This tells the dynamic linker that the symbol
376 table of the shared object should be used as an auxiliary filter on the
377 symbol table of the shared object \fIname\fR.
379 If you later link a program against this filter object, then, when you
380 run the program, the dynamic linker will see the \s-1DT_AUXILIARY\s0 field. If
381 the dynamic linker resolves any symbols from the filter object, it will
382 first check whether there is a definition in the shared object
383 \&\fIname\fR. If there is one, it will be used instead of the definition
384 in the filter object. The shared object \fIname\fR need not exist.
385 Thus the shared object \fIname\fR may be used to provide an alternative
386 implementation of certain functions, perhaps for debugging or for
387 machine specific performance.
389 This option may be specified more than once. The \s-1DT_AUXILIARY\s0 entries
390 will be created in the order in which they appear on the command line.
391 .IP "\fB\-F\fR \fIname\fR" 4
394 .IP "\fB\-\-filter\fR \fIname\fR" 4
395 .IX Item "--filter name"
397 When creating an \s-1ELF\s0 shared object, set the internal \s-1DT_FILTER\s0 field to
398 the specified name. This tells the dynamic linker that the symbol table
399 of the shared object which is being created should be used as a filter
400 on the symbol table of the shared object \fIname\fR.
402 If you later link a program against this filter object, then, when you
403 run the program, the dynamic linker will see the \s-1DT_FILTER\s0 field. The
404 dynamic linker will resolve symbols according to the symbol table of the
405 filter object as usual, but it will actually link to the definitions
406 found in the shared object \fIname\fR. Thus the filter object can be
407 used to select a subset of the symbols provided by the object
410 Some older linkers used the \fB\-F\fR option throughout a compilation
411 toolchain for specifying object-file format for both input and output
412 object files. The \s-1GNU\s0 linker uses other mechanisms for this
413 purpose: the \fB\-b\fR, \fB\-\-format\fR, \fB\-\-oformat\fR options, the
414 \&\f(CW\*(C`TARGET\*(C'\fR command in linker scripts, and the \f(CW\*(C`GNUTARGET\*(C'\fR
415 environment variable. The \s-1GNU\s0 linker will ignore the \fB\-F\fR
416 option when not creating an \s-1ELF\s0 shared object.
417 .IP "\fB\-fini\fR \fIname\fR" 4
418 .IX Item "-fini name"
419 When creating an \s-1ELF\s0 executable or shared object, call \s-1NAME\s0 when the
420 executable or shared object is unloaded, by setting \s-1DT_FINI\s0 to the
421 address of the function. By default, the linker uses \f(CW\*(C`_fini\*(C'\fR as
422 the function to call.
425 Ignored. Provided for compatibility with other tools.
426 .IP "\fB\-G\fR\fIvalue\fR" 4
429 .IP "\fB\-\-gpsize=\fR\fIvalue\fR" 4
430 .IX Item "--gpsize=value"
432 Set the maximum size of objects to be optimized using the \s-1GP\s0 register to
433 \&\fIsize\fR. This is only meaningful for object file formats such as
434 \&\s-1MIPS\s0 \s-1ECOFF\s0 which supports putting large and small objects into different
435 sections. This is ignored for other object file formats.
436 .IP "\fB\-h\fR\fIname\fR" 4
439 .IP "\fB\-soname=\fR\fIname\fR" 4
440 .IX Item "-soname=name"
442 When creating an \s-1ELF\s0 shared object, set the internal \s-1DT_SONAME\s0 field to
443 the specified name. When an executable is linked with a shared object
444 which has a \s-1DT_SONAME\s0 field, then when the executable is run the dynamic
445 linker will attempt to load the shared object specified by the \s-1DT_SONAME\s0
446 field rather than the using the file name given to the linker.
449 Perform an incremental link (same as option \fB\-r\fR).
450 .IP "\fB\-init\fR \fIname\fR" 4
451 .IX Item "-init name"
452 When creating an \s-1ELF\s0 executable or shared object, call \s-1NAME\s0 when the
453 executable or shared object is loaded, by setting \s-1DT_INIT\s0 to the address
454 of the function. By default, the linker uses \f(CW\*(C`_init\*(C'\fR as the
456 .IP "\fB\-l\fR\fIarchive\fR" 4
459 .IP "\fB\-\-library=\fR\fIarchive\fR" 4
460 .IX Item "--library=archive"
462 Add archive file \fIarchive\fR to the list of files to link. This
463 option may be used any number of times. \fBld\fR will search its
464 path-list for occurrences of \f(CW\*(C`lib\f(CIarchive\f(CW.a\*(C'\fR for every
465 \&\fIarchive\fR specified.
467 On systems which support shared libraries, \fBld\fR may also search for
468 libraries with extensions other than \f(CW\*(C`.a\*(C'\fR. Specifically, on \s-1ELF\s0
469 and SunOS systems, \fBld\fR will search a directory for a library with
470 an extension of \f(CW\*(C`.so\*(C'\fR before searching for one with an extension of
471 \&\f(CW\*(C`.a\*(C'\fR. By convention, a \f(CW\*(C`.so\*(C'\fR extension indicates a shared
474 The linker will search an archive only once, at the location where it is
475 specified on the command line. If the archive defines a symbol which
476 was undefined in some object which appeared before the archive on the
477 command line, the linker will include the appropriate file(s) from the
478 archive. However, an undefined symbol in an object appearing later on
479 the command line will not cause the linker to search the archive again.
481 See the \fB\-(\fR option for a way to force the linker to search
482 archives multiple times.
484 You may list the same archive multiple times on the command line.
486 This type of archive searching is standard for Unix linkers. However,
487 if you are using \fBld\fR on \s-1AIX\s0, note that it is different from the
488 behaviour of the \s-1AIX\s0 linker.
489 .IP "\fB\-L\fR\fIsearchdir\fR" 4
490 .IX Item "-Lsearchdir"
492 .IP "\fB\-\-library\-path=\fR\fIsearchdir\fR" 4
493 .IX Item "--library-path=searchdir"
495 Add path \fIsearchdir\fR to the list of paths that \fBld\fR will search
496 for archive libraries and \fBld\fR control scripts. You may use this
497 option any number of times. The directories are searched in the order
498 in which they are specified on the command line. Directories specified
499 on the command line are searched before the default directories. All
500 \&\fB\-L\fR options apply to all \fB\-l\fR options, regardless of the
501 order in which the options appear.
503 The default set of paths searched (without being specified with
504 \&\fB\-L\fR) depends on which emulation mode \fBld\fR is using, and in
505 some cases also on how it was configured.
507 The paths can also be specified in a link script with the
508 \&\f(CW\*(C`SEARCH_DIR\*(C'\fR command. Directories specified this way are searched
509 at the point in which the linker script appears in the command line.
510 .IP "\fB\-m\fR\fIemulation\fR" 4
511 .IX Item "-memulation"
512 Emulate the \fIemulation\fR linker. You can list the available
513 emulations with the \fB\-\-verbose\fR or \fB\-V\fR options.
515 If the \fB\-m\fR option is not used, the emulation is taken from the
516 \&\f(CW\*(C`LDEMULATION\*(C'\fR environment variable, if that is defined.
518 Otherwise, the default emulation depends upon how the linker was
523 .IP "\fB\-\-print\-map\fR" 4
524 .IX Item "--print-map"
526 Print a link map to the standard output. A link map provides
527 information about the link, including the following:
530 Where object files and symbols are mapped into memory.
532 How common symbols are allocated.
534 All archive members included in the link, with a mention of the symbol
535 which caused the archive member to be brought in.
542 .IP "\fB\-\-nmagic\fR" 4
545 Turn off page alignment of sections, and mark the output as
546 \&\f(CW\*(C`NMAGIC\*(C'\fR if possible.
550 .IP "\fB\-\-omagic\fR" 4
553 Set the text and data sections to be readable and writable. Also, do
554 not page-align the data segment. If the output format supports Unix
555 style magic numbers, mark the output as \f(CW\*(C`OMAGIC\*(C'\fR.
556 .IP "\fB\-o\fR \fIoutput\fR" 4
559 .IP "\fB\-\-output=\fR\fIoutput\fR" 4
560 .IX Item "--output=output"
562 Use \fIoutput\fR as the name for the program produced by \fBld\fR; if this
563 option is not specified, the name \fIa.out\fR is used by default. The
564 script command \f(CW\*(C`OUTPUT\*(C'\fR can also specify the output file name.
565 .IP "\fB\-O\fR \fIlevel\fR" 4
567 If \fIlevel\fR is a numeric values greater than zero \fBld\fR optimizes
568 the output. This might take significantly longer and therefore probably
569 should only be enabled for the final binary.
573 .IP "\fB\-\-emit\-relocs\fR" 4
574 .IX Item "--emit-relocs"
576 Leave relocation sections and contents in fully linked exececutables.
577 Post link analysis and optimization tools may need this information in
578 order to perform correct modifications of executables. This results
579 in larger executables.
581 This option is currently only supported on \s-1ELF\s0 platforms.
585 .IP "\fB\-\-relocateable\fR" 4
586 .IX Item "--relocateable"
588 Generate relocatable output\-\-\-i.e., generate an output file that can in
589 turn serve as input to \fBld\fR. This is often called \fIpartial
590 linking\fR. As a side effect, in environments that support standard Unix
591 magic numbers, this option also sets the output file's magic number to
592 \&\f(CW\*(C`OMAGIC\*(C'\fR.
593 If this option is not specified, an absolute file is produced. When
594 linking \*(C+ programs, this option \fIwill not\fR resolve references to
595 constructors; to do that, use \fB\-Ur\fR.
597 When an input file does not have the same format as the output file,
598 partial linking is only supported if that input file does not contain any
599 relocations. Different output formats can have further restrictions; for
600 example some \f(CW\*(C`a.out\*(C'\fR\-based formats do not support partial linking
601 with input files in other formats at all.
603 This option does the same thing as \fB\-i\fR.
604 .IP "\fB\-R\fR \fIfilename\fR" 4
605 .IX Item "-R filename"
607 .IP "\fB\-\-just\-symbols=\fR\fIfilename\fR" 4
608 .IX Item "--just-symbols=filename"
610 Read symbol names and their addresses from \fIfilename\fR, but do not
611 relocate it or include it in the output. This allows your output file
612 to refer symbolically to absolute locations of memory defined in other
613 programs. You may use this option more than once.
615 For compatibility with other \s-1ELF\s0 linkers, if the \fB\-R\fR option is
616 followed by a directory name, rather than a file name, it is treated as
617 the \fB\-rpath\fR option.
621 .IP "\fB\-\-strip\-all\fR" 4
622 .IX Item "--strip-all"
624 Omit all symbol information from the output file.
628 .IP "\fB\-\-strip\-debug\fR" 4
629 .IX Item "--strip-debug"
631 Omit debugger symbol information (but not all symbols) from the output file.
635 .IP "\fB\-\-trace\fR" 4
638 Print the names of the input files as \fBld\fR processes them.
639 .IP "\fB\-T\fR \fIscriptfile\fR" 4
640 .IX Item "-T scriptfile"
642 .IP "\fB\-\-script=\fR\fIscriptfile\fR" 4
643 .IX Item "--script=scriptfile"
645 Use \fIscriptfile\fR as the linker script. This script replaces
646 \&\fBld\fR's default linker script (rather than adding to it), so
647 \&\fIcommandfile\fR must specify everything necessary to describe the
648 output file. If \fIscriptfile\fR does not exist in
649 the current directory, \f(CW\*(C`ld\*(C'\fR looks for it in the directories
650 specified by any preceding \fB\-L\fR options. Multiple \fB\-T\fR
652 .IP "\fB\-u\fR \fIsymbol\fR" 4
655 .IP "\fB\-\-undefined=\fR\fIsymbol\fR" 4
656 .IX Item "--undefined=symbol"
658 Force \fIsymbol\fR to be entered in the output file as an undefined
659 symbol. Doing this may, for example, trigger linking of additional
660 modules from standard libraries. \fB\-u\fR may be repeated with
661 different option arguments to enter additional undefined symbols. This
662 option is equivalent to the \f(CW\*(C`EXTERN\*(C'\fR linker script command.
665 For anything other than \*(C+ programs, this option is equivalent to
666 \&\fB\-r\fR: it generates relocatable output\-\-\-i.e., an output file that can in
667 turn serve as input to \fBld\fR. When linking \*(C+ programs, \fB\-Ur\fR
668 \&\fIdoes\fR resolve references to constructors, unlike \fB\-r\fR.
669 It does not work to use \fB\-Ur\fR on files that were themselves linked
670 with \fB\-Ur\fR; once the constructor table has been built, it cannot
671 be added to. Use \fB\-Ur\fR only for the last partial link, and
672 \&\fB\-r\fR for the others.
673 .IP "\fB\-\-unique[=\fR\fI\s-1SECTION\s0\fR\fB]\fR" 4
674 .IX Item "--unique[=SECTION]"
675 Creates a separate output section for every input section matching
676 \&\fI\s-1SECTION\s0\fR, or if the optional wildcard \fI\s-1SECTION\s0\fR argument is
677 missing, for every orphan input section. An orphan section is one not
678 specifically mentioned in a linker script. You may use this option
679 multiple times on the command line; It prevents the normal merging of
680 input sections with the same name, overriding output section assignments
685 .IP "\fB\-\-version\fR" 4
690 Display the version number for \fBld\fR. The \fB\-V\fR option also
691 lists the supported emulations.
695 .IP "\fB\-\-discard\-all\fR" 4
696 .IX Item "--discard-all"
698 Delete all local symbols.
702 .IP "\fB\-\-discard\-locals\fR" 4
703 .IX Item "--discard-locals"
705 Delete all temporary local symbols. For most targets, this is all local
706 symbols whose names begin with \fBL\fR.
707 .IP "\fB\-y\fR \fIsymbol\fR" 4
710 .IP "\fB\-\-trace\-symbol=\fR\fIsymbol\fR" 4
711 .IX Item "--trace-symbol=symbol"
713 Print the name of each linked file in which \fIsymbol\fR appears. This
714 option may be given any number of times. On many systems it is necessary
715 to prepend an underscore.
717 This option is useful when you have an undefined symbol in your link but
718 don't know where the reference is coming from.
719 .IP "\fB\-Y\fR \fIpath\fR" 4
721 Add \fIpath\fR to the default library search path. This option exists
722 for Solaris compatibility.
723 .IP "\fB\-z\fR \fIkeyword\fR" 4
724 .IX Item "-z keyword"
725 The recognized keywords are \f(CW\*(C`initfirst\*(C'\fR, \f(CW\*(C`interpose\*(C'\fR,
726 \&\f(CW\*(C`loadfltr\*(C'\fR, \f(CW\*(C`nodefaultlib\*(C'\fR, \f(CW\*(C`nodelete\*(C'\fR, \f(CW\*(C`nodlopen\*(C'\fR,
727 \&\f(CW\*(C`nodump\*(C'\fR, \f(CW\*(C`now\*(C'\fR, \f(CW\*(C`origin\*(C'\fR, \f(CW\*(C`combreloc\*(C'\fR, \f(CW\*(C`nocombreloc\*(C'\fR
728 and \f(CW\*(C`nocopyreloc\*(C'\fR.
729 The other keywords are
730 ignored for Solaris compatibility. \f(CW\*(C`initfirst\*(C'\fR marks the object
731 to be initialized first at runtime before any other objects.
732 \&\f(CW\*(C`interpose\*(C'\fR marks the object that its symbol table interposes
733 before all symbols but the primary executable. \f(CW\*(C`loadfltr\*(C'\fR marks
734 the object that its filtees be processed immediately at runtime.
735 \&\f(CW\*(C`nodefaultlib\*(C'\fR marks the object that the search for dependencies
736 of this object will ignore any default library search paths.
737 \&\f(CW\*(C`nodelete\*(C'\fR marks the object shouldn't be unloaded at runtime.
738 \&\f(CW\*(C`nodlopen\*(C'\fR marks the object not available to \f(CW\*(C`dlopen\*(C'\fR.
739 \&\f(CW\*(C`nodump\*(C'\fR marks the object can not be dumped by \f(CW\*(C`dldump\*(C'\fR.
740 \&\f(CW\*(C`now\*(C'\fR marks the object with the non-lazy runtime binding.
741 \&\f(CW\*(C`origin\*(C'\fR marks the object may contain \f(CW$ORIGIN\fR.
742 \&\f(CW\*(C`defs\*(C'\fR disallows undefined symbols.
743 \&\f(CW\*(C`combreloc\*(C'\fR combines multiple reloc sections and sorts them
744 to make dynamic symbol lookup caching possible.
745 \&\f(CW\*(C`nocombreloc\*(C'\fR disables multiple reloc sections combining.
746 \&\f(CW\*(C`nocopyreloc\*(C'\fR disables production of copy relocs.
747 .IP "\fB\-(\fR \fIarchives\fR \fB\-)\fR" 4
748 .IX Item "-( archives -)"
750 .IP "\fB\-\-start\-group\fR \fIarchives\fR \fB\-\-end\-group\fR" 4
751 .IX Item "--start-group archives --end-group"
753 The \fIarchives\fR should be a list of archive files. They may be
754 either explicit file names, or \fB\-l\fR options.
756 The specified archives are searched repeatedly until no new undefined
757 references are created. Normally, an archive is searched only once in
758 the order that it is specified on the command line. If a symbol in that
759 archive is needed to resolve an undefined symbol referred to by an
760 object in an archive that appears later on the command line, the linker
761 would not be able to resolve that reference. By grouping the archives,
762 they all be searched repeatedly until all possible references are
765 Using this option has a significant performance cost. It is best to use
766 it only when there are unavoidable circular references between two or
768 .IP "\fB\-assert\fR \fIkeyword\fR" 4
769 .IX Item "-assert keyword"
770 This option is ignored for SunOS compatibility.
771 .IP "\fB\-Bdynamic\fR" 4
776 .IP "\fB\-call_shared\fR" 4
777 .IX Item "-call_shared"
779 Link against dynamic libraries. This is only meaningful on platforms
780 for which shared libraries are supported. This option is normally the
781 default on such platforms. The different variants of this option are
782 for compatibility with various systems. You may use this option
783 multiple times on the command line: it affects library searching for
784 \&\fB\-l\fR options which follow it.
785 .IP "\fB\-Bgroup\fR" 4
787 Set the \f(CW\*(C`DF_1_GROUP\*(C'\fR flag in the \f(CW\*(C`DT_FLAGS_1\*(C'\fR entry in the dynamic
788 section. This causes the runtime linker to handle lookups in this
789 object and its dependencies to be performed only inside the group.
790 \&\fB\-\-no\-undefined\fR is implied. This option is only meaningful on \s-1ELF\s0
791 platforms which support shared libraries.
792 .IP "\fB\-Bstatic\fR" 4
797 .IP "\fB\-non_shared\fR" 4
798 .IX Item "-non_shared"
799 .IP "\fB\-static\fR" 4
802 Do not link against shared libraries. This is only meaningful on
803 platforms for which shared libraries are supported. The different
804 variants of this option are for compatibility with various systems. You
805 may use this option multiple times on the command line: it affects
806 library searching for \fB\-l\fR options which follow it.
807 .IP "\fB\-Bsymbolic\fR" 4
808 .IX Item "-Bsymbolic"
809 When creating a shared library, bind references to global symbols to the
810 definition within the shared library, if any. Normally, it is possible
811 for a program linked against a shared library to override the definition
812 within the shared library. This option is only meaningful on \s-1ELF\s0
813 platforms which support shared libraries.
814 .IP "\fB\-\-check\-sections\fR" 4
815 .IX Item "--check-sections"
817 .IP "\fB\-\-no\-check\-sections\fR" 4
818 .IX Item "--no-check-sections"
820 Asks the linker \fInot\fR to check section addresses after they have
821 been assigned to see if there any overlaps. Normally the linker will
822 perform this check, and if it finds any overlaps it will produce
823 suitable error messages. The linker does know about, and does make
824 allowances for sections in overlays. The default behaviour can be
825 restored by using the command line switch \fB\-\-check\-sections\fR.
826 .IP "\fB\-\-cref\fR" 4
828 Output a cross reference table. If a linker map file is being
829 generated, the cross reference table is printed to the map file.
830 Otherwise, it is printed on the standard output.
832 The format of the table is intentionally simple, so that it may be
833 easily processed by a script if necessary. The symbols are printed out,
834 sorted by name. For each symbol, a list of file names is given. If the
835 symbol is defined, the first file listed is the location of the
836 definition. The remaining files contain references to the symbol.
837 .IP "\fB\-\-no\-define\-common\fR" 4
838 .IX Item "--no-define-common"
839 This option inhibits the assignment of addresses to common symbols.
840 The script command \f(CW\*(C`INHIBIT_COMMON_ALLOCATION\*(C'\fR has the same effect.
842 The \fB\-\-no\-define\-common\fR option allows decoupling
843 the decision to assign addresses to Common symbols from the choice
844 of the output file type; otherwise a non-Relocatable output type
845 forces assigning addresses to Common symbols.
846 Using \fB\-\-no\-define\-common\fR allows Common symbols that are referenced
847 from a shared library to be assigned addresses only in the main program.
848 This eliminates the unused duplicate space in the shared library,
849 and also prevents any possible confusion over resolving to the wrong
850 duplicate when there are many dynamic modules with specialized search
851 paths for runtime symbol resolution.
852 .IP "\fB\-\-defsym\fR \fIsymbol\fR\fB=\fR\fIexpression\fR" 4
853 .IX Item "--defsym symbol=expression"
854 Create a global symbol in the output file, containing the absolute
855 address given by \fIexpression\fR. You may use this option as many
856 times as necessary to define multiple symbols in the command line. A
857 limited form of arithmetic is supported for the \fIexpression\fR in this
858 context: you may give a hexadecimal constant or the name of an existing
859 symbol, or use \f(CW\*(C`+\*(C'\fR and \f(CW\*(C`\-\*(C'\fR to add or subtract hexadecimal
860 constants or symbols. If you need more elaborate expressions, consider
861 using the linker command language from a script. \fINote:\fR there should be no white
862 space between \fIsymbol\fR, the equals sign (``\fB=\fR''), and
864 .IP "\fB\-\-demangle[=\fR\fIstyle\fR\fB]\fR" 4
865 .IX Item "--demangle[=style]"
867 .IP "\fB\-\-no\-demangle\fR" 4
868 .IX Item "--no-demangle"
870 These options control whether to demangle symbol names in error messages
871 and other output. When the linker is told to demangle, it tries to
872 present symbol names in a readable fashion: it strips leading
873 underscores if they are used by the object file format, and converts \*(C+
874 mangled symbol names into user readable names. Different compilers have
875 different mangling styles. The optional demangling style argument can be used
876 to choose an appropriate demangling style for your compiler. The linker will
877 demangle by default unless the environment variable \fB\s-1COLLECT_NO_DEMANGLE\s0\fR
878 is set. These options may be used to override the default.
879 .IP "\fB\-\-dynamic\-linker\fR \fIfile\fR" 4
880 .IX Item "--dynamic-linker file"
881 Set the name of the dynamic linker. This is only meaningful when
882 generating dynamically linked \s-1ELF\s0 executables. The default dynamic
883 linker is normally correct; don't use this unless you know what you are
885 .IP "\fB\-\-embedded\-relocs\fR" 4
886 .IX Item "--embedded-relocs"
887 This option is only meaningful when linking \s-1MIPS\s0 embedded \s-1PIC\s0 code,
888 generated by the \-membedded\-pic option to the \s-1GNU\s0 compiler and
889 assembler. It causes the linker to create a table which may be used at
890 runtime to relocate any data which was statically initialized to pointer
891 values. See the code in testsuite/ld\-empic for details.
892 .IP "\fB\-\-fatal\-warnings\fR" 4
893 .IX Item "--fatal-warnings"
894 Treat all warnings as errors.
895 .IP "\fB\-\-force\-exe\-suffix\fR" 4
896 .IX Item "--force-exe-suffix"
897 Make sure that an output file has a .exe suffix.
899 If a successfully built fully linked output file does not have a
900 \&\f(CW\*(C`.exe\*(C'\fR or \f(CW\*(C`.dll\*(C'\fR suffix, this option forces the linker to copy
901 the output file to one of the same name with a \f(CW\*(C`.exe\*(C'\fR suffix. This
902 option is useful when using unmodified Unix makefiles on a Microsoft
903 Windows host, since some versions of Windows won't run an image unless
904 it ends in a \f(CW\*(C`.exe\*(C'\fR suffix.
905 .IP "\fB\-\-no\-gc\-sections\fR" 4
906 .IX Item "--no-gc-sections"
908 .IP "\fB\-\-gc\-sections\fR" 4
909 .IX Item "--gc-sections"
911 Enable garbage collection of unused input sections. It is ignored on
912 targets that do not support this option. This option is not compatible
913 with \fB\-r\fR, nor should it be used with dynamic linking. The default
914 behaviour (of not performing this garbage collection) can be restored by
915 specifying \fB\-\-no\-gc\-sections\fR on the command line.
916 .IP "\fB\-\-help\fR" 4
918 Print a summary of the command-line options on the standard output and exit.
919 .IP "\fB\-\-target\-help\fR" 4
920 .IX Item "--target-help"
921 Print a summary of all target specific options on the standard output and exit.
922 .IP "\fB\-Map\fR \fImapfile\fR" 4
923 .IX Item "-Map mapfile"
924 Print a link map to the file \fImapfile\fR. See the description of the
925 \&\fB\-M\fR option, above.
926 .IP "\fB\-\-no\-keep\-memory\fR" 4
927 .IX Item "--no-keep-memory"
928 \&\fBld\fR normally optimizes for speed over memory usage by caching the
929 symbol tables of input files in memory. This option tells \fBld\fR to
930 instead optimize for memory usage, by rereading the symbol tables as
931 necessary. This may be required if \fBld\fR runs out of memory space
932 while linking a large executable.
933 .IP "\fB\-\-no\-undefined\fR" 4
934 .IX Item "--no-undefined"
936 .IP "\fB\-z defs\fR" 4
939 Normally when creating a non-symbolic shared library, undefined symbols
940 are allowed and left to be resolved by the runtime loader. These options
941 disallows such undefined symbols.
942 .IP "\fB\-\-allow\-shlib\-undefined\fR" 4
943 .IX Item "--allow-shlib-undefined"
944 Allow undefined symbols in shared objects even when \-\-no\-undefined is
945 set. The net result will be that undefined symbols in regular objects
946 will still trigger an error, but undefined symbols in shared objects
947 will be ignored. The implementation of no_undefined makes the
948 assumption that the runtime linker will choke on undefined symbols.
949 However there is at least one system (BeOS) where undefined symbols in
950 shared libraries is normal since the kernel patches them at load time to
951 select which function is most appropriate for the current architecture.
952 I.E. dynamically select an appropriate memset function. Apparently it
953 is also normal for \s-1HPPA\s0 shared libraries to have undefined symbols.
954 .IP "\fB\-\-no\-warn\-mismatch\fR" 4
955 .IX Item "--no-warn-mismatch"
956 Normally \fBld\fR will give an error if you try to link together input
957 files that are mismatched for some reason, perhaps because they have
958 been compiled for different processors or for different endiannesses.
959 This option tells \fBld\fR that it should silently permit such possible
960 errors. This option should only be used with care, in cases when you
961 have taken some special action that ensures that the linker errors are
963 .IP "\fB\-\-no\-whole\-archive\fR" 4
964 .IX Item "--no-whole-archive"
965 Turn off the effect of the \fB\-\-whole\-archive\fR option for subsequent
967 .IP "\fB\-\-noinhibit\-exec\fR" 4
968 .IX Item "--noinhibit-exec"
969 Retain the executable output file whenever it is still usable.
970 Normally, the linker will not produce an output file if it encounters
971 errors during the link process; it exits without writing an output file
972 when it issues any error whatsoever.
973 .IP "\fB\-nostdlib\fR" 4
975 Only search library directories explicitly specified on the
976 command line. Library directories specified in linker scripts
977 (including linker scripts specified on the command line) are ignored.
978 .IP "\fB\-\-oformat\fR \fIoutput-format\fR" 4
979 .IX Item "--oformat output-format"
980 \&\fBld\fR may be configured to support more than one kind of object
981 file. If your \fBld\fR is configured this way, you can use the
982 \&\fB\-\-oformat\fR option to specify the binary format for the output
983 object file. Even when \fBld\fR is configured to support alternative
984 object formats, you don't usually need to specify this, as \fBld\fR
985 should be configured to produce as a default output format the most
986 usual format on each machine. \fIoutput-format\fR is a text string, the
987 name of a particular format supported by the \s-1BFD\s0 libraries. (You can
988 list the available binary formats with \fBobjdump \-i\fR.) The script
989 command \f(CW\*(C`OUTPUT_FORMAT\*(C'\fR can also specify the output format, but
990 this option overrides it.
991 .IP "\fB\-qmagic\fR" 4
993 This option is ignored for Linux compatibility.
996 This option is ignored for \s-1SVR4\s0 compatibility.
997 .IP "\fB\-\-relax\fR" 4
999 An option with machine dependent effects.
1000 This option is only supported on a few targets.
1002 On some platforms, the \fB\-\-relax\fR option performs global
1003 optimizations that become possible when the linker resolves addressing
1004 in the program, such as relaxing address modes and synthesizing new
1005 instructions in the output object file.
1007 On some platforms these link time global optimizations may make symbolic
1008 debugging of the resulting executable impossible.
1010 the case for the Matsushita \s-1MN10200\s0 and \s-1MN10300\s0 family of processors.
1012 On platforms where this is not supported, \fB\-\-relax\fR is accepted,
1014 .IP "\fB\-\-retain\-symbols\-file\fR \fIfilename\fR" 4
1015 .IX Item "--retain-symbols-file filename"
1016 Retain \fIonly\fR the symbols listed in the file \fIfilename\fR,
1017 discarding all others. \fIfilename\fR is simply a flat file, with one
1018 symbol name per line. This option is especially useful in environments
1020 where a large global symbol table is accumulated gradually, to conserve
1023 \&\fB\-\-retain\-symbols\-file\fR does \fInot\fR discard undefined symbols,
1024 or symbols needed for relocations.
1026 You may only specify \fB\-\-retain\-symbols\-file\fR once in the command
1027 line. It overrides \fB\-s\fR and \fB\-S\fR.
1028 .IP "\fB\-rpath\fR \fIdir\fR" 4
1029 .IX Item "-rpath dir"
1030 Add a directory to the runtime library search path. This is used when
1031 linking an \s-1ELF\s0 executable with shared objects. All \fB\-rpath\fR
1032 arguments are concatenated and passed to the runtime linker, which uses
1033 them to locate shared objects at runtime. The \fB\-rpath\fR option is
1034 also used when locating shared objects which are needed by shared
1035 objects explicitly included in the link; see the description of the
1036 \&\fB\-rpath\-link\fR option. If \fB\-rpath\fR is not used when linking an
1037 \&\s-1ELF\s0 executable, the contents of the environment variable
1038 \&\f(CW\*(C`LD_RUN_PATH\*(C'\fR will be used if it is defined.
1040 The \fB\-rpath\fR option may also be used on SunOS. By default, on
1041 SunOS, the linker will form a runtime search patch out of all the
1042 \&\fB\-L\fR options it is given. If a \fB\-rpath\fR option is used, the
1043 runtime search path will be formed exclusively using the \fB\-rpath\fR
1044 options, ignoring the \fB\-L\fR options. This can be useful when using
1045 gcc, which adds many \fB\-L\fR options which may be on \s-1NFS\s0 mounted
1048 For compatibility with other \s-1ELF\s0 linkers, if the \fB\-R\fR option is
1049 followed by a directory name, rather than a file name, it is treated as
1050 the \fB\-rpath\fR option.
1051 .IP "\fB\-rpath\-link\fR \fI\s-1DIR\s0\fR" 4
1052 .IX Item "-rpath-link DIR"
1053 When using \s-1ELF\s0 or SunOS, one shared library may require another. This
1054 happens when an \f(CW\*(C`ld \-shared\*(C'\fR link includes a shared library as one
1057 When the linker encounters such a dependency when doing a non\-shared,
1058 non-relocatable link, it will automatically try to locate the required
1059 shared library and include it in the link, if it is not included
1060 explicitly. In such a case, the \fB\-rpath\-link\fR option
1061 specifies the first set of directories to search. The
1062 \&\fB\-rpath\-link\fR option may specify a sequence of directory names
1063 either by specifying a list of names separated by colons, or by
1064 appearing multiple times.
1066 This option should be used with caution as it overrides the search path
1067 that may have been hard compiled into a shared library. In such a case it
1068 is possible to use unintentionally a different search path than the
1069 runtime linker would do.
1071 The linker uses the following search paths to locate required shared
1075 Any directories specified by \fB\-rpath\-link\fR options.
1077 Any directories specified by \fB\-rpath\fR options. The difference
1078 between \fB\-rpath\fR and \fB\-rpath\-link\fR is that directories
1079 specified by \fB\-rpath\fR options are included in the executable and
1080 used at runtime, whereas the \fB\-rpath\-link\fR option is only effective
1081 at link time. It is for the native linker only.
1083 On an \s-1ELF\s0 system, if the \fB\-rpath\fR and \f(CW\*(C`rpath\-link\*(C'\fR options
1084 were not used, search the contents of the environment variable
1085 \&\f(CW\*(C`LD_RUN_PATH\*(C'\fR. It is for the native linker only.
1087 On SunOS, if the \fB\-rpath\fR option was not used, search any
1088 directories specified using \fB\-L\fR options.
1090 For a native linker, the contents of the environment variable
1091 \&\f(CW\*(C`LD_LIBRARY_PATH\*(C'\fR.
1093 For a native \s-1ELF\s0 linker, the directories in \f(CW\*(C`DT_RUNPATH\*(C'\fR or
1094 \&\f(CW\*(C`DT_RPATH\*(C'\fR of a shared library are searched for shared
1095 libraries needed by it. The \f(CW\*(C`DT_RPATH\*(C'\fR entries are ignored if
1096 \&\f(CW\*(C`DT_RUNPATH\*(C'\fR entries exist.
1098 The default directories, normally \fI/lib\fR and \fI/usr/lib\fR.
1100 For a native linker on an \s-1ELF\s0 system, if the file \fI/etc/ld.so.conf\fR
1101 exists, the list of directories found in that file.
1105 If the required shared library is not found, the linker will issue a
1106 warning and continue with the link.
1108 .IP "\fB\-shared\fR" 4
1111 .IP "\fB\-Bshareable\fR" 4
1112 .IX Item "-Bshareable"
1114 Create a shared library. This is currently only supported on \s-1ELF\s0, \s-1XCOFF\s0
1115 and SunOS platforms. On SunOS, the linker will automatically create a
1116 shared library if the \fB\-e\fR option is not used and there are
1117 undefined symbols in the link.
1118 .IP "\fB\-\-sort\-common\fR" 4
1119 .IX Item "--sort-common"
1120 This option tells \fBld\fR to sort the common symbols by size when it
1121 places them in the appropriate output sections. First come all the one
1122 byte symbols, then all the two byte, then all the four byte, and then
1123 everything else. This is to prevent gaps between symbols due to
1124 alignment constraints.
1125 .IP "\fB\-\-split\-by\-file [\fR\fIsize\fR\fB]\fR" 4
1126 .IX Item "--split-by-file [size]"
1127 Similar to \fB\-\-split\-by\-reloc\fR but creates a new output section for
1128 each input file when \fIsize\fR is reached. \fIsize\fR defaults to a
1129 size of 1 if not given.
1130 .IP "\fB\-\-split\-by\-reloc [\fR\fIcount\fR\fB]\fR" 4
1131 .IX Item "--split-by-reloc [count]"
1132 Tries to creates extra sections in the output file so that no single
1133 output section in the file contains more than \fIcount\fR relocations.
1134 This is useful when generating huge relocatable files for downloading into
1135 certain real time kernels with the \s-1COFF\s0 object file format; since \s-1COFF\s0
1136 cannot represent more than 65535 relocations in a single section. Note
1137 that this will fail to work with object file formats which do not
1138 support arbitrary sections. The linker will not split up individual
1139 input sections for redistribution, so if a single input section contains
1140 more than \fIcount\fR relocations one output section will contain that
1141 many relocations. \fIcount\fR defaults to a value of 32768.
1142 .IP "\fB\-\-stats\fR" 4
1144 Compute and display statistics about the operation of the linker, such
1145 as execution time and memory usage.
1146 .IP "\fB\-\-traditional\-format\fR" 4
1147 .IX Item "--traditional-format"
1148 For some targets, the output of \fBld\fR is different in some ways from
1149 the output of some existing linker. This switch requests \fBld\fR to
1150 use the traditional format instead.
1152 For example, on SunOS, \fBld\fR combines duplicate entries in the
1153 symbol string table. This can reduce the size of an output file with
1154 full debugging information by over 30 percent. Unfortunately, the SunOS
1155 \&\f(CW\*(C`dbx\*(C'\fR program can not read the resulting program (\f(CW\*(C`gdb\*(C'\fR has no
1156 trouble). The \fB\-\-traditional\-format\fR switch tells \fBld\fR to not
1157 combine duplicate entries.
1158 .IP "\fB\-\-section\-start\fR \fIsectionname\fR\fB=\fR\fIorg\fR" 4
1159 .IX Item "--section-start sectionname=org"
1160 Locate a section in the output file at the absolute
1161 address given by \fIorg\fR. You may use this option as many
1162 times as necessary to locate multiple sections in the command
1164 \&\fIorg\fR must be a single hexadecimal integer;
1165 for compatibility with other linkers, you may omit the leading
1166 \&\fB0x\fR usually associated with hexadecimal values. \fINote:\fR there
1167 should be no white space between \fIsectionname\fR, the equals
1168 sign (``\fB=\fR''), and \fIorg\fR.
1169 .IP "\fB\-Tbss\fR \fIorg\fR" 4
1170 .IX Item "-Tbss org"
1172 .IP "\fB\-Tdata\fR \fIorg\fR" 4
1173 .IX Item "-Tdata org"
1174 .IP "\fB\-Ttext\fR \fIorg\fR" 4
1175 .IX Item "-Ttext org"
1177 Use \fIorg\fR as the starting address for\-\-\-respectively\-\-\-the
1178 \&\f(CW\*(C`bss\*(C'\fR, \f(CW\*(C`data\*(C'\fR, or the \f(CW\*(C`text\*(C'\fR segment of the output file.
1179 \&\fIorg\fR must be a single hexadecimal integer;
1180 for compatibility with other linkers, you may omit the leading
1181 \&\fB0x\fR usually associated with hexadecimal values.
1182 .IP "\fB\-\-dll\-verbose\fR" 4
1183 .IX Item "--dll-verbose"
1185 .IP "\fB\-\-verbose\fR" 4
1186 .IX Item "--verbose"
1188 Display the version number for \fBld\fR and list the linker emulations
1189 supported. Display which input files can and cannot be opened. Display
1190 the linker script being used by the linker.
1191 .IP "\fB\-\-version\-script=\fR\fIversion-scriptfile\fR" 4
1192 .IX Item "--version-script=version-scriptfile"
1193 Specify the name of a version script to the linker. This is typically
1194 used when creating shared libraries to specify additional information
1195 about the version heirarchy for the library being created. This option
1196 is only meaningful on \s-1ELF\s0 platforms which support shared libraries.
1197 .IP "\fB\-\-warn\-common\fR" 4
1198 .IX Item "--warn-common"
1199 Warn when a common symbol is combined with another common symbol or with
1200 a symbol definition. Unix linkers allow this somewhat sloppy practice,
1201 but linkers on some other operating systems do not. This option allows
1202 you to find potential problems from combining global symbols.
1203 Unfortunately, some C libraries use this practice, so you may get some
1204 warnings about symbols in the libraries as well as in your programs.
1206 There are three kinds of global symbols, illustrated here by C examples:
1208 .IP "\fBint i = 1;\fR" 4
1209 .IX Item "int i = 1;"
1210 A definition, which goes in the initialized data section of the output
1212 .IP "\fBextern int i;\fR" 4
1213 .IX Item "extern int i;"
1214 An undefined reference, which does not allocate space.
1215 There must be either a definition or a common symbol for the
1217 .IP "\fBint i;\fR" 4
1219 A common symbol. If there are only (one or more) common symbols for a
1220 variable, it goes in the uninitialized data area of the output file.
1221 The linker merges multiple common symbols for the same variable into a
1222 single symbol. If they are of different sizes, it picks the largest
1223 size. The linker turns a common symbol into a declaration, if there is
1224 a definition of the same variable.
1228 The \fB\-\-warn\-common\fR option can produce five kinds of warnings.
1229 Each warning consists of a pair of lines: the first describes the symbol
1230 just encountered, and the second describes the previous symbol
1231 encountered with the same name. One or both of the two symbols will be
1234 Turning a common symbol into a reference, because there is already a
1235 definition for the symbol.
1238 \& I<file>(I<section>): warning: common of `I<symbol>'
1239 \& overridden by definition
1240 \& I<file>(I<section>): warning: defined here
1243 Turning a common symbol into a reference, because a later definition for
1244 the symbol is encountered. This is the same as the previous case,
1245 except that the symbols are encountered in a different order.
1248 \& I<file>(I<section>): warning: definition of `I<symbol>'
1249 \& overriding common
1250 \& I<file>(I<section>): warning: common is here
1253 Merging a common symbol with a previous same-sized common symbol.
1256 \& I<file>(I<section>): warning: multiple common
1258 \& I<file>(I<section>): warning: previous common is here
1261 Merging a common symbol with a previous larger common symbol.
1264 \& I<file>(I<section>): warning: common of `I<symbol>'
1265 \& overridden by larger common
1266 \& I<file>(I<section>): warning: larger common is here
1269 Merging a common symbol with a previous smaller common symbol. This is
1270 the same as the previous case, except that the symbols are
1271 encountered in a different order.
1274 \& I<file>(I<section>): warning: common of `I<symbol>'
1275 \& overriding smaller common
1276 \& I<file>(I<section>): warning: smaller common is here
1281 .IP "\fB\-\-warn\-constructors\fR" 4
1282 .IX Item "--warn-constructors"
1283 Warn if any global constructors are used. This is only useful for a few
1284 object file formats. For formats like \s-1COFF\s0 or \s-1ELF\s0, the linker can not
1285 detect the use of global constructors.
1286 .IP "\fB\-\-warn\-multiple\-gp\fR" 4
1287 .IX Item "--warn-multiple-gp"
1288 Warn if multiple global pointer values are required in the output file.
1289 This is only meaningful for certain processors, such as the Alpha.
1290 Specifically, some processors put large-valued constants in a special
1291 section. A special register (the global pointer) points into the middle
1292 of this section, so that constants can be loaded efficiently via a
1293 base-register relative addressing mode. Since the offset in
1294 base-register relative mode is fixed and relatively small (e.g., 16
1295 bits), this limits the maximum size of the constant pool. Thus, in
1296 large programs, it is often necessary to use multiple global pointer
1297 values in order to be able to address all possible constants. This
1298 option causes a warning to be issued whenever this case occurs.
1299 .IP "\fB\-\-warn\-once\fR" 4
1300 .IX Item "--warn-once"
1301 Only warn once for each undefined symbol, rather than once per module
1303 .IP "\fB\-\-warn\-section\-align\fR" 4
1304 .IX Item "--warn-section-align"
1305 Warn if the address of an output section is changed because of
1306 alignment. Typically, the alignment will be set by an input section.
1307 The address will only be changed if it not explicitly specified; that
1308 is, if the \f(CW\*(C`SECTIONS\*(C'\fR command does not specify a start address for
1310 .IP "\fB\-\-whole\-archive\fR" 4
1311 .IX Item "--whole-archive"
1312 For each archive mentioned on the command line after the
1313 \&\fB\-\-whole\-archive\fR option, include every object file in the archive
1314 in the link, rather than searching the archive for the required object
1315 files. This is normally used to turn an archive file into a shared
1316 library, forcing every object to be included in the resulting shared
1317 library. This option may be used more than once.
1319 Two notes when using this option from gcc: First, gcc doesn't know
1320 about this option, so you have to use \fB\-Wl,\-whole\-archive\fR.
1321 Second, don't forget to use \fB\-Wl,\-no\-whole\-archive\fR after your
1322 list of archives, because gcc will add its own list of archives to
1323 your link and you may not want this flag to affect those as well.
1324 .IP "\fB\-\-wrap\fR \fIsymbol\fR" 4
1325 .IX Item "--wrap symbol"
1326 Use a wrapper function for \fIsymbol\fR. Any undefined reference to
1327 \&\fIsymbol\fR will be resolved to \f(CW\*(C`_\|_wrap_\f(CIsymbol\f(CW\*(C'\fR. Any
1328 undefined reference to \f(CW\*(C`_\|_real_\f(CIsymbol\f(CW\*(C'\fR will be resolved to
1331 This can be used to provide a wrapper for a system function. The
1332 wrapper function should be called \f(CW\*(C`_\|_wrap_\f(CIsymbol\f(CW\*(C'\fR. If it
1333 wishes to call the system function, it should call
1334 \&\f(CW\*(C`_\|_real_\f(CIsymbol\f(CW\*(C'\fR.
1336 Here is a trivial example:
1340 \& __wrap_malloc (int c)
1342 \& printf ("malloc called with %ld\en", c);
1343 \& return __real_malloc (c);
1346 If you link other code with this file using \fB\-\-wrap malloc\fR, then
1347 all calls to \f(CW\*(C`malloc\*(C'\fR will call the function \f(CW\*(C`_\|_wrap_malloc\*(C'\fR
1348 instead. The call to \f(CW\*(C`_\|_real_malloc\*(C'\fR in \f(CW\*(C`_\|_wrap_malloc\*(C'\fR will
1349 call the real \f(CW\*(C`malloc\*(C'\fR function.
1351 You may wish to provide a \f(CW\*(C`_\|_real_malloc\*(C'\fR function as well, so that
1352 links without the \fB\-\-wrap\fR option will succeed. If you do this,
1353 you should not put the definition of \f(CW\*(C`_\|_real_malloc\*(C'\fR in the same
1354 file as \f(CW\*(C`_\|_wrap_malloc\*(C'\fR; if you do, the assembler may resolve the
1355 call before the linker has a chance to wrap it to \f(CW\*(C`malloc\*(C'\fR.
1356 .IP "\fB\-\-enable\-new\-dtags\fR" 4
1357 .IX Item "--enable-new-dtags"
1359 .IP "\fB\-\-disable\-new\-dtags\fR" 4
1360 .IX Item "--disable-new-dtags"
1362 This linker can create the new dynamic tags in \s-1ELF\s0. But the older \s-1ELF\s0
1363 systems may not understand them. If you specify
1364 \&\fB\-\-enable\-new\-dtags\fR, the dynamic tags will be created as needed.
1365 If you specify \fB\-\-disable\-new\-dtags\fR, no new dynamic tags will be
1366 created. By default, the new dynamic tags are not created. Note that
1367 those options are only available for \s-1ELF\s0 systems.
1369 The i386 \s-1PE\s0 linker supports the \fB\-shared\fR option, which causes
1370 the output to be a dynamically linked library (\s-1DLL\s0) instead of a
1371 normal executable. You should name the output \f(CW\*(C`*.dll\*(C'\fR when you
1372 use this option. In addition, the linker fully supports the standard
1373 \&\f(CW\*(C`*.def\*(C'\fR files, which may be specified on the linker command line
1374 like an object file (in fact, it should precede archives it exports
1375 symbols from, to ensure that they get linked in, just like a normal
1378 In addition to the options common to all targets, the i386 \s-1PE\s0 linker
1379 support additional command line options that are specific to the i386
1380 \&\s-1PE\s0 target. Options that take values may be separated from their
1381 values by either a space or an equals sign.
1382 .IP "\fB\-\-add\-stdcall\-alias\fR" 4
1383 .IX Item "--add-stdcall-alias"
1384 If given, symbols with a stdcall suffix (@\fInn\fR) will be exported
1385 as-is and also with the suffix stripped.
1386 .IP "\fB\-\-base\-file\fR \fIfile\fR" 4
1387 .IX Item "--base-file file"
1388 Use \fIfile\fR as the name of a file in which to save the base
1389 addresses of all the relocations needed for generating DLLs with
1391 .IP "\fB\-\-dll\fR" 4
1393 Create a \s-1DLL\s0 instead of a regular executable. You may also use
1394 \&\fB\-shared\fR or specify a \f(CW\*(C`LIBRARY\*(C'\fR in a given \f(CW\*(C`.def\*(C'\fR
1396 .IP "\fB\-\-enable\-stdcall\-fixup\fR" 4
1397 .IX Item "--enable-stdcall-fixup"
1399 .IP "\fB\-\-disable\-stdcall\-fixup\fR" 4
1400 .IX Item "--disable-stdcall-fixup"
1402 If the link finds a symbol that it cannot resolve, it will attempt to
1403 do \*(L"fuzzy linking\*(R" by looking for another defined symbol that differs
1404 only in the format of the symbol name (cdecl vs stdcall) and will
1405 resolve that symbol by linking to the match. For example, the
1406 undefined symbol \f(CW\*(C`_foo\*(C'\fR might be linked to the function
1407 \&\f(CW\*(C`_foo@12\*(C'\fR, or the undefined symbol \f(CW\*(C`_bar@16\*(C'\fR might be linked
1408 to the function \f(CW\*(C`_bar\*(C'\fR. When the linker does this, it prints a
1409 warning, since it normally should have failed to link, but sometimes
1410 import libraries generated from third-party dlls may need this feature
1411 to be usable. If you specify \fB\-\-enable\-stdcall\-fixup\fR, this
1412 feature is fully enabled and warnings are not printed. If you specify
1413 \&\fB\-\-disable\-stdcall\-fixup\fR, this feature is disabled and such
1414 mismatches are considered to be errors.
1415 .IP "\fB\-\-export\-all\-symbols\fR" 4
1416 .IX Item "--export-all-symbols"
1417 If given, all global symbols in the objects used to build a \s-1DLL\s0 will
1418 be exported by the \s-1DLL\s0. Note that this is the default if there
1419 otherwise wouldn't be any exported symbols. When symbols are
1420 explicitly exported via \s-1DEF\s0 files or implicitly exported via function
1421 attributes, the default is to not export anything else unless this
1422 option is given. Note that the symbols \f(CW\*(C`DllMain@12\*(C'\fR,
1423 \&\f(CW\*(C`DllEntryPoint@0\*(C'\fR, \f(CW\*(C`DllMainCRTStartup@12\*(C'\fR, and
1424 \&\f(CW\*(C`impure_ptr\*(C'\fR will not be automatically
1425 exported. Also, symbols imported from other DLLs will not be
1426 re\-exported, nor will symbols specifying the \s-1DLL\s0's internal layout
1427 such as those beginning with \f(CW\*(C`_head_\*(C'\fR or ending with
1428 \&\f(CW\*(C`_iname\*(C'\fR. In addition, no symbols from \f(CW\*(C`libgcc\*(C'\fR,
1429 \&\f(CW\*(C`libstd++\*(C'\fR, \f(CW\*(C`libmingw32\*(C'\fR, or \f(CW\*(C`crtX.o\*(C'\fR will be exported.
1430 Symbols whose names begin with \f(CW\*(C`_\|_rtti_\*(C'\fR or \f(CW\*(C`_\|_builtin_\*(C'\fR will
1431 not be exported, to help with \*(C+ DLLs. Finally, there is an
1432 extensive list of cygwin-private symbols that are not exported
1433 (obviously, this applies on when building DLLs for cygwin targets).
1434 These cygwin-excludes are: \f(CW\*(C`_cygwin_dll_entry@12\*(C'\fR,
1435 \&\f(CW\*(C`_cygwin_crt0_common@8\*(C'\fR, \f(CW\*(C`_cygwin_noncygwin_dll_entry@12\*(C'\fR,
1436 \&\f(CW\*(C`_fmode\*(C'\fR, \f(CW\*(C`_impure_ptr\*(C'\fR, \f(CW\*(C`cygwin_attach_dll\*(C'\fR,
1437 \&\f(CW\*(C`cygwin_premain0\*(C'\fR, \f(CW\*(C`cygwin_premain1\*(C'\fR, \f(CW\*(C`cygwin_premain2\*(C'\fR,
1438 \&\f(CW\*(C`cygwin_premain3\*(C'\fR, and \f(CW\*(C`environ\*(C'\fR.
1439 .IP "\fB\-\-exclude\-symbols\fR \fIsymbol\fR\fB,\fR\fIsymbol\fR\fB,...\fR" 4
1440 .IX Item "--exclude-symbols symbol,symbol,..."
1441 Specifies a list of symbols which should not be automatically
1442 exported. The symbol names may be delimited by commas or colons.
1443 .IP "\fB\-\-file\-alignment\fR" 4
1444 .IX Item "--file-alignment"
1445 Specify the file alignment. Sections in the file will always begin at
1446 file offsets which are multiples of this number. This defaults to
1448 .IP "\fB\-\-heap\fR \fIreserve\fR" 4
1449 .IX Item "--heap reserve"
1451 .IP "\fB\-\-heap\fR \fIreserve\fR\fB,\fR\fIcommit\fR" 4
1452 .IX Item "--heap reserve,commit"
1454 Specify the amount of memory to reserve (and optionally commit) to be
1455 used as heap for this program. The default is 1Mb reserved, 4K
1457 .IP "\fB\-\-image\-base\fR \fIvalue\fR" 4
1458 .IX Item "--image-base value"
1459 Use \fIvalue\fR as the base address of your program or dll. This is
1460 the lowest memory location that will be used when your program or dll
1461 is loaded. To reduce the need to relocate and improve performance of
1462 your dlls, each should have a unique base address and not overlap any
1463 other dlls. The default is 0x400000 for executables, and 0x10000000
1465 .IP "\fB\-\-kill\-at\fR" 4
1466 .IX Item "--kill-at"
1467 If given, the stdcall suffixes (@\fInn\fR) will be stripped from
1468 symbols before they are exported.
1469 .IP "\fB\-\-major\-image\-version\fR \fIvalue\fR" 4
1470 .IX Item "--major-image-version value"
1471 Sets the major number of the \*(L"image version\*(R". Defaults to 1.
1472 .IP "\fB\-\-major\-os\-version\fR \fIvalue\fR" 4
1473 .IX Item "--major-os-version value"
1474 Sets the major number of the \*(L"os version\*(R". Defaults to 4.
1475 .IP "\fB\-\-major\-subsystem\-version\fR \fIvalue\fR" 4
1476 .IX Item "--major-subsystem-version value"
1477 Sets the major number of the \*(L"subsystem version\*(R". Defaults to 4.
1478 .IP "\fB\-\-minor\-image\-version\fR \fIvalue\fR" 4
1479 .IX Item "--minor-image-version value"
1480 Sets the minor number of the \*(L"image version\*(R". Defaults to 0.
1481 .IP "\fB\-\-minor\-os\-version\fR \fIvalue\fR" 4
1482 .IX Item "--minor-os-version value"
1483 Sets the minor number of the \*(L"os version\*(R". Defaults to 0.
1484 .IP "\fB\-\-minor\-subsystem\-version\fR \fIvalue\fR" 4
1485 .IX Item "--minor-subsystem-version value"
1486 Sets the minor number of the \*(L"subsystem version\*(R". Defaults to 0.
1487 .IP "\fB\-\-output\-def\fR \fIfile\fR" 4
1488 .IX Item "--output-def file"
1489 The linker will create the file \fIfile\fR which will contain a \s-1DEF\s0
1490 file corresponding to the \s-1DLL\s0 the linker is generating. This \s-1DEF\s0 file
1491 (which should be called \f(CW\*(C`*.def\*(C'\fR) may be used to create an import
1492 library with \f(CW\*(C`dlltool\*(C'\fR or may be used as a reference to
1493 automatically or implicitly exported symbols.
1494 .IP "\fB\-\-out\-implib\fR \fIfile\fR" 4
1495 .IX Item "--out-implib file"
1496 The linker will create the file \fIfile\fR which will contain an
1497 import lib corresponding to the \s-1DLL\s0 the linker is generating. This
1498 import lib (which should be called \f(CW\*(C`*.dll.a\*(C'\fR or \f(CW\*(C`*.a\*(C'\fR
1499 may be used to link clients against the generated \s-1DLL\s0; this behavior
1500 makes it possible to skip a separate \f(CW\*(C`dlltool\*(C'\fR import library
1502 .IP "\fB\-\-enable\-auto\-image\-base\fR" 4
1503 .IX Item "--enable-auto-image-base"
1504 Automatically choose the image base for DLLs, unless one is specified
1505 using the \f(CW\*(C`\-\-image\-base\*(C'\fR argument. By using a hash generated
1506 from the dllname to create unique image bases for each \s-1DLL\s0, in-memory
1507 collisions and relocations which can delay program execution are
1509 .IP "\fB\-\-disable\-auto\-image\-base\fR" 4
1510 .IX Item "--disable-auto-image-base"
1511 Do not automatically generate a unique image base. If there is no
1512 user-specified image base (\f(CW\*(C`\-\-image\-base\*(C'\fR) then use the platform
1514 .IP "\fB\-\-dll\-search\-prefix\fR \fIstring\fR" 4
1515 .IX Item "--dll-search-prefix string"
1516 When linking dynamically to a dll without an import library, i
1517 search for \f(CW\*(C`<string><basename>.dll\*(C'\fR in preference to
1518 \&\f(CW\*(C`lib<basename>.dll\*(C'\fR. This behavior allows easy distinction
1519 between DLLs built for the various \*(L"subplatforms\*(R": native, cygwin,
1520 uwin, pw, etc. For instance, cygwin DLLs typically use
1521 \&\f(CW\*(C`\-\-dll\-search\-prefix=cyg\*(C'\fR.
1522 .IP "\fB\-\-enable\-auto\-import\fR" 4
1523 .IX Item "--enable-auto-import"
1524 Do sophisticated linking of \f(CW\*(C`_symbol\*(C'\fR to \f(CW\*(C`_\|_imp_\|_symbol\*(C'\fR for
1525 \&\s-1DATA\s0 imports from DLLs, and create the necessary thunking symbols when
1526 building the DLLs with those \s-1DATA\s0 exports. This generally will 'just
1527 work' \*(-- but sometimes you may see this message:
1529 "variable '<var>' can't be auto\-imported. Please read the
1530 documentation for ld's \f(CW\*(C`\-\-enable\-auto\-import\*(C'\fR for details."
1532 This message occurs when some (sub)expression accesses an address
1533 ultimately given by the sum of two constants (Win32 import tables only
1534 allow one). Instances where this may occur include accesses to member
1535 fields of struct variables imported from a \s-1DLL\s0, as well as using a
1536 constant index into an array variable imported from a \s-1DLL\s0. Any
1537 multiword variable (arrays, structs, long long, etc) may trigger
1538 this error condition. However, regardless of the exact data type
1539 of the offending exported variable, ld will always detect it, issue
1540 the warning, and exit.
1542 There are several ways to address this difficulty, regardless of the
1543 data type of the exported variable:
1545 One solution is to force one of the 'constants' to be a variable \*(--
1546 that is, unknown and un-optimizable at compile time. For arrays,
1547 there are two possibilities: a) make the indexee (the array's address)
1548 a variable, or b) make the 'constant' index a variable. Thus:
1551 \& extern type extern_array[];
1552 \& extern_array[1] -->
1553 \& { volatile type *t=extern_array; t[1] }
1558 \& extern type extern_array[];
1559 \& extern_array[1] -->
1560 \& { volatile int t=1; extern_array[t] }
1562 For structs (and most other multiword data types) the only option
1563 is to make the struct itself (or the long long, or the ...) variable:
1566 \& extern struct s extern_struct;
1567 \& extern_struct.field -->
1568 \& { volatile struct s *t=&extern_struct; t->field }
1573 \& extern long long extern_ll;
1575 \& { volatile long long * local_ll=&extern_ll; *local_ll }
1577 A second method of dealing with this difficulty is to abandon
1578 \&'auto\-import' for the offending symbol and mark it with
1579 \&\f(CW\*(C`_\|_declspec(dllimport)\*(C'\fR. However, in practice that
1580 requires using compile-time #defines to indicate whether you are
1581 building a \s-1DLL\s0, building client code that will link to the \s-1DLL\s0, or
1582 merely building/linking to a static library. In making the choice
1583 between the various methods of resolving the 'direct address with
1584 constant offset' problem, you should consider typical real-world usage:
1590 \& extern int arr[];
1593 \& void main(int argc, char **argv){
1594 \& printf("%d\en",arr[1]);
1601 \& extern int arr[];
1604 \& void main(int argc, char **argv){
1605 \& /* This workaround is for win32 and cygwin; do not "optimize" */
1606 \& volatile int *parr = arr;
1607 \& printf("%d\en",parr[1]);
1614 \& /* Note: auto-export is assumed (no __declspec(dllexport)) */
1615 \& #if (defined(_WIN32) || defined(__CYGWIN__)) && \e
1616 \& !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
1617 \& #define FOO_IMPORT __declspec(dllimport)
1619 \& #define FOO_IMPORT
1621 \& extern FOO_IMPORT int arr[];
1624 \& void main(int argc, char **argv){
1625 \& printf("%d\en",arr[1]);
1628 A third way to avoid this problem is to re-code your
1629 library to use a functional interface rather than a data interface
1630 for the offending variables (e.g. \fIset_foo()\fR and \fIget_foo()\fR accessor
1632 .IP "\fB\-\-disable\-auto\-import\fR" 4
1633 .IX Item "--disable-auto-import"
1634 Do not attempt to do sophisticalted linking of \f(CW\*(C`_symbol\*(C'\fR to
1635 \&\f(CW\*(C`_\|_imp_\|_symbol\*(C'\fR for \s-1DATA\s0 imports from DLLs.
1636 .IP "\fB\-\-enable\-extra\-pe\-debug\fR" 4
1637 .IX Item "--enable-extra-pe-debug"
1638 Show additional debug info related to auto-import symbol thunking.
1639 .IP "\fB\-\-section\-alignment\fR" 4
1640 .IX Item "--section-alignment"
1641 Sets the section alignment. Sections in memory will always begin at
1642 addresses which are a multiple of this number. Defaults to 0x1000.
1643 .IP "\fB\-\-stack\fR \fIreserve\fR" 4
1644 .IX Item "--stack reserve"
1646 .IP "\fB\-\-stack\fR \fIreserve\fR\fB,\fR\fIcommit\fR" 4
1647 .IX Item "--stack reserve,commit"
1649 Specify the amount of memory to reserve (and optionally commit) to be
1650 used as stack for this program. The default is 2Mb reserved, 4K
1652 .IP "\fB\-\-subsystem\fR \fIwhich\fR" 4
1653 .IX Item "--subsystem which"
1655 .IP "\fB\-\-subsystem\fR \fIwhich\fR\fB:\fR\fImajor\fR" 4
1656 .IX Item "--subsystem which:major"
1657 .IP "\fB\-\-subsystem\fR \fIwhich\fR\fB:\fR\fImajor\fR\fB.\fR\fIminor\fR" 4
1658 .IX Item "--subsystem which:major.minor"
1660 Specifies the subsystem under which your program will execute. The
1661 legal values for \fIwhich\fR are \f(CW\*(C`native\*(C'\fR, \f(CW\*(C`windows\*(C'\fR,
1662 \&\f(CW\*(C`console\*(C'\fR, and \f(CW\*(C`posix\*(C'\fR. You may optionally set the
1663 subsystem version also.
1665 .IX Header "ENVIRONMENT"
1666 You can change the behavior of \fBld\fR with the environment variables
1667 \&\f(CW\*(C`GNUTARGET\*(C'\fR, \f(CW\*(C`LDEMULATION\*(C'\fR, and \f(CW\*(C`COLLECT_NO_DEMANGLE\*(C'\fR.
1669 \&\f(CW\*(C`GNUTARGET\*(C'\fR determines the input-file object format if you don't
1670 use \fB\-b\fR (or its synonym \fB\-\-format\fR). Its value should be one
1671 of the \s-1BFD\s0 names for an input format. If there is no
1672 \&\f(CW\*(C`GNUTARGET\*(C'\fR in the environment, \fBld\fR uses the natural format
1673 of the target. If \f(CW\*(C`GNUTARGET\*(C'\fR is set to \f(CW\*(C`default\*(C'\fR then \s-1BFD\s0
1674 attempts to discover the input format by examining binary input files;
1675 this method often succeeds, but there are potential ambiguities, since
1676 there is no method of ensuring that the magic number used to specify
1677 object-file formats is unique. However, the configuration procedure for
1678 \&\s-1BFD\s0 on each system places the conventional format for that system first
1679 in the search\-list, so ambiguities are resolved in favor of convention.
1681 \&\f(CW\*(C`LDEMULATION\*(C'\fR determines the default emulation if you don't use the
1682 \&\fB\-m\fR option. The emulation can affect various aspects of linker
1683 behaviour, particularly the default linker script. You can list the
1684 available emulations with the \fB\-\-verbose\fR or \fB\-V\fR options. If
1685 the \fB\-m\fR option is not used, and the \f(CW\*(C`LDEMULATION\*(C'\fR environment
1686 variable is not defined, the default emulation depends upon how the
1687 linker was configured.
1689 Normally, the linker will default to demangling symbols. However, if
1690 \&\f(CW\*(C`COLLECT_NO_DEMANGLE\*(C'\fR is set in the environment, then it will
1691 default to not demangling symbols. This environment variable is used in
1692 a similar fashion by the \f(CW\*(C`gcc\*(C'\fR linker wrapper program. The default
1693 may be overridden by the \fB\-\-demangle\fR and \fB\-\-no\-demangle\fR
1696 .IX Header "SEE ALSO"
1697 \&\fIar\fR\|(1), \fInm\fR\|(1), \fIobjcopy\fR\|(1), \fIobjdump\fR\|(1), \fIreadelf\fR\|(1) and
1698 the Info entries for \fIbinutils\fR and
1701 .IX Header "COPYRIGHT"
1702 Copyright (c) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001 Free Software Foundation, Inc.
1704 Permission is granted to copy, distribute and/or modify this document
1705 under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.1
1706 or any later version published by the Free Software Foundation;
1707 with no Invariant Sections, with no Front-Cover Texts, and with no
1708 Back-Cover Texts. A copy of the license is included in the
1709 section entitled \*(L"\s-1GNU\s0 Free Documentation License\*(R".
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