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140 .TH LD 1 "binutils-2.16.91" "2006-01-20" "GNU Development Tools"
143 ld \- Using \s-1LD\s0, the \s-1GNU\s0 linker
145 .IX Header "SYNOPSIS"
146 ld [\fBoptions\fR] \fIobjfile\fR ...
148 .IX Header "DESCRIPTION"
149 \&\fBld\fR combines a number of object and archive files, relocates
150 their data and ties up symbol references. Usually the last step in
151 compiling a program is to run \fBld\fR.
153 \&\fBld\fR accepts Linker Command Language files written in
154 a superset of \s-1AT&T\s0's Link Editor Command Language syntax,
155 to provide explicit and total control over the linking process.
157 This man page does not describe the command language; see the
158 \&\fBld\fR entry in \f(CW\*(C`info\*(C'\fR, or the manual
159 ld: the \s-1GNU\s0 linker, for full details on the command language and
160 on other aspects of the \s-1GNU\s0 linker.
162 This version of \fBld\fR uses the general purpose \s-1BFD\s0 libraries
163 to operate on object files. This allows \fBld\fR to read, combine, and
164 write object files in many different formats\-\-\-for example, \s-1COFF\s0 or
165 \&\f(CW\*(C`a.out\*(C'\fR. Different formats may be linked together to produce any
166 available kind of object file.
168 Aside from its flexibility, the \s-1GNU\s0 linker is more helpful than other
169 linkers in providing diagnostic information. Many linkers abandon
170 execution immediately upon encountering an error; whenever possible,
171 \&\fBld\fR continues executing, allowing you to identify other errors
172 (or, in some cases, to get an output file in spite of the error).
174 The \s-1GNU\s0 linker \fBld\fR is meant to cover a broad range of situations,
175 and to be as compatible as possible with other linkers. As a result,
176 you have many choices to control its behavior.
179 The linker supports a plethora of command-line options, but in actual
180 practice few of them are used in any particular context.
181 For instance, a frequent use of \fBld\fR is to link standard Unix
182 object files on a standard, supported Unix system. On such a system, to
183 link a file \f(CW\*(C`hello.o\*(C'\fR:
186 \& ld -o <output> /lib/crt0.o hello.o -lc
188 This tells \fBld\fR to produce a file called \fIoutput\fR as the
189 result of linking the file \f(CW\*(C`/lib/crt0.o\*(C'\fR with \f(CW\*(C`hello.o\*(C'\fR and
190 the library \f(CW\*(C`libc.a\*(C'\fR, which will come from the standard search
191 directories. (See the discussion of the \fB\-l\fR option below.)
193 Some of the command-line options to \fBld\fR may be specified at any
194 point in the command line. However, options which refer to files, such
195 as \fB\-l\fR or \fB\-T\fR, cause the file to be read at the point at
196 which the option appears in the command line, relative to the object
197 files and other file options. Repeating non-file options with a
198 different argument will either have no further effect, or override prior
199 occurrences (those further to the left on the command line) of that
200 option. Options which may be meaningfully specified more than once are
201 noted in the descriptions below.
203 Non-option arguments are object files or archives which are to be linked
204 together. They may follow, precede, or be mixed in with command-line
205 options, except that an object file argument may not be placed between
206 an option and its argument.
208 Usually the linker is invoked with at least one object file, but you can
209 specify other forms of binary input files using \fB\-l\fR, \fB\-R\fR,
210 and the script command language. If \fIno\fR binary input files at all
211 are specified, the linker does not produce any output, and issues the
212 message \fBNo input files\fR.
214 If the linker cannot recognize the format of an object file, it will
215 assume that it is a linker script. A script specified in this way
216 augments the main linker script used for the link (either the default
217 linker script or the one specified by using \fB\-T\fR). This feature
218 permits the linker to link against a file which appears to be an object
219 or an archive, but actually merely defines some symbol values, or uses
220 \&\f(CW\*(C`INPUT\*(C'\fR or \f(CW\*(C`GROUP\*(C'\fR to load other objects. Note that
221 specifying a script in this way merely augments the main linker script;
222 use the \fB\-T\fR option to replace the default linker script entirely.
224 For options whose names are a single letter,
225 option arguments must either follow the option letter without intervening
226 whitespace, or be given as separate arguments immediately following the
227 option that requires them.
229 For options whose names are multiple letters, either one dash or two can
230 precede the option name; for example, \fB\-trace-symbol\fR and
231 \&\fB\*(--trace-symbol\fR are equivalent. Note\-\-\-there is one exception to
232 this rule. Multiple letter options that start with a lower case 'o' can
233 only be preceeded by two dashes. This is to reduce confusion with the
234 \&\fB\-o\fR option. So for example \fB\-omagic\fR sets the output file
235 name to \fBmagic\fR whereas \fB\*(--omagic\fR sets the \s-1NMAGIC\s0 flag on the
238 Arguments to multiple-letter options must either be separated from the
239 option name by an equals sign, or be given as separate arguments
240 immediately following the option that requires them. For example,
241 \&\fB\*(--trace-symbol foo\fR and \fB\*(--trace-symbol=foo\fR are equivalent.
242 Unique abbreviations of the names of multiple-letter options are
245 Note\-\-\-if the linker is being invoked indirectly, via a compiler driver
246 (e.g. \fBgcc\fR) then all the linker command line options should be
247 prefixed by \fB\-Wl,\fR (or whatever is appropriate for the particular
248 compiler driver) like this:
251 \& gcc -Wl,--startgroup foo.o bar.o -Wl,--endgroup
253 This is important, because otherwise the compiler driver program may
254 silently drop the linker options, resulting in a bad link.
256 Here is a table of the generic command line switches accepted by the \s-1GNU\s0
258 .Ip "\fB@\fR\fIfile\fR" 4
260 Read command-line options from \fIfile\fR. The options read are
261 inserted in place of the original @\fIfile\fR option. If \fIfile\fR
262 does not exist, or cannot be read, then the option will be treated
263 literally, and not removed.
265 Options in \fIfile\fR are separated by whitespace. A whitespace
266 character may be included in an option by surrounding the entire
267 option in either single or double quotes. Any character (including a
268 backslash) may be included by prefixing the character to be included
269 with a backslash. The \fIfile\fR may itself contain additional
270 @\fIfile\fR options; any such options will be processed recursively.
271 .Ip "\fB\-a\fR\fIkeyword\fR" 4
273 This option is supported for \s-1HP/UX\s0 compatibility. The \fIkeyword\fR
274 argument must be one of the strings \fBarchive\fR, \fBshared\fR, or
275 \&\fBdefault\fR. \fB\-aarchive\fR is functionally equivalent to
276 \&\fB\-Bstatic\fR, and the other two keywords are functionally equivalent
277 to \fB\-Bdynamic\fR. This option may be used any number of times.
278 .Ip "\fB\-A\fR\fIarchitecture\fR" 4
279 .IX Item "-Aarchitecture"
281 .Ip "\fB\*(--architecture=\fR\fIarchitecture\fR" 4
282 .IX Item "architecture=architecture"
284 In the current release of \fBld\fR, this option is useful only for the
285 Intel 960 family of architectures. In that \fBld\fR configuration, the
286 \&\fIarchitecture\fR argument identifies the particular architecture in
287 the 960 family, enabling some safeguards and modifying the
288 archive-library search path.
290 Future releases of \fBld\fR may support similar functionality for
291 other architecture families.
292 .Ip "\fB\-b\fR \fIinput-format\fR" 4
293 .IX Item "-b input-format"
295 .Ip "\fB\*(--format=\fR\fIinput-format\fR" 4
296 .IX Item "format=input-format"
298 \&\fBld\fR may be configured to support more than one kind of object
299 file. If your \fBld\fR is configured this way, you can use the
300 \&\fB\-b\fR option to specify the binary format for input object files
301 that follow this option on the command line. Even when \fBld\fR is
302 configured to support alternative object formats, you don't usually need
303 to specify this, as \fBld\fR should be configured to expect as a
304 default input format the most usual format on each machine.
305 \&\fIinput-format\fR is a text string, the name of a particular format
306 supported by the \s-1BFD\s0 libraries. (You can list the available binary
307 formats with \fBobjdump \-i\fR.)
309 You may want to use this option if you are linking files with an unusual
310 binary format. You can also use \fB\-b\fR to switch formats explicitly (when
311 linking object files of different formats), by including
312 \&\fB\-b\fR \fIinput-format\fR before each group of object files in a
315 The default format is taken from the environment variable
316 \&\f(CW\*(C`GNUTARGET\*(C'\fR.
318 You can also define the input format from a script, using the command
319 \&\f(CW\*(C`TARGET\*(C'\fR;
320 .Ip "\fB\-c\fR \fIMRI-commandfile\fR" 4
321 .IX Item "-c MRI-commandfile"
323 .Ip "\fB\*(--mri-script=\fR\fIMRI-commandfile\fR" 4
324 .IX Item "mri-script=MRI-commandfile"
326 For compatibility with linkers produced by \s-1MRI\s0, \fBld\fR accepts script
327 files written in an alternate, restricted command language, described in
328 the \s-1MRI\s0 Compatible Script Files section of \s-1GNU\s0 ld documentation.
329 Introduce \s-1MRI\s0 script files with
330 the option \fB\-c\fR; use the \fB\-T\fR option to run linker
331 scripts written in the general-purpose \fBld\fR scripting language.
332 If \fIMRI-cmdfile\fR does not exist, \fBld\fR looks for it in the directories
333 specified by any \fB\-L\fR options.
342 These three options are equivalent; multiple forms are supported for
343 compatibility with other linkers. They assign space to common symbols
344 even if a relocatable output file is specified (with \fB\-r\fR). The
345 script command \f(CW\*(C`FORCE_COMMON_ALLOCATION\*(C'\fR has the same effect.
346 .Ip "\fB\-e\fR \fIentry\fR" 4
349 .Ip "\fB\*(--entry=\fR\fIentry\fR" 4
350 .IX Item "entry=entry"
352 Use \fIentry\fR as the explicit symbol for beginning execution of your
353 program, rather than the default entry point. If there is no symbol
354 named \fIentry\fR, the linker will try to parse \fIentry\fR as a number,
355 and use that as the entry address (the number will be interpreted in
356 base 10; you may use a leading \fB0x\fR for base 16, or a leading
357 \&\fB0\fR for base 8).
358 .Ip "\fB\*(--exclude-libs\fR \fIlib\fR\fB,\fR\fIlib\fR\fB,...\fR" 4
359 .IX Item "exclude-libs lib,lib,..."
360 Specifies a list of archive libraries from which symbols should not be automatically
361 exported. The library names may be delimited by commas or colons. Specifying
362 \&\f(CW\*(C`\-\-exclude\-libs ALL\*(C'\fR excludes symbols in all archive libraries from
363 automatic export. This option is available only for the i386 \s-1PE\s0 targeted
364 port of the linker and for \s-1ELF\s0 targeted ports. For i386 \s-1PE\s0, symbols
365 explicitly listed in a .def file are still exported, regardless of this
366 option. For \s-1ELF\s0 targeted ports, symbols affected by this option will
367 be treated as hidden.
371 .Ip "\fB\*(--export-dynamic\fR" 4
372 .IX Item "export-dynamic"
374 When creating a dynamically linked executable, add all symbols to the
375 dynamic symbol table. The dynamic symbol table is the set of symbols
376 which are visible from dynamic objects at run time.
378 If you do not use this option, the dynamic symbol table will normally
379 contain only those symbols which are referenced by some dynamic object
380 mentioned in the link.
382 If you use \f(CW\*(C`dlopen\*(C'\fR to load a dynamic object which needs to refer
383 back to the symbols defined by the program, rather than some other
384 dynamic object, then you will probably need to use this option when
385 linking the program itself.
387 You can also use the version script to control what symbols should
388 be added to the dynamic symbol table if the output format supports it.
389 See the description of \fB\*(--version-script\fR in \fB\s-1VERSION\s0\fR.
392 Link big-endian objects. This affects the default output format.
395 Link little-endian objects. This affects the default output format.
399 .Ip "\fB\*(--auxiliary\fR \fIname\fR" 4
400 .IX Item "auxiliary name"
402 When creating an \s-1ELF\s0 shared object, set the internal \s-1DT_AUXILIARY\s0 field
403 to the specified name. This tells the dynamic linker that the symbol
404 table of the shared object should be used as an auxiliary filter on the
405 symbol table of the shared object \fIname\fR.
407 If you later link a program against this filter object, then, when you
408 run the program, the dynamic linker will see the \s-1DT_AUXILIARY\s0 field. If
409 the dynamic linker resolves any symbols from the filter object, it will
410 first check whether there is a definition in the shared object
411 \&\fIname\fR. If there is one, it will be used instead of the definition
412 in the filter object. The shared object \fIname\fR need not exist.
413 Thus the shared object \fIname\fR may be used to provide an alternative
414 implementation of certain functions, perhaps for debugging or for
415 machine specific performance.
417 This option may be specified more than once. The \s-1DT_AUXILIARY\s0 entries
418 will be created in the order in which they appear on the command line.
419 .Ip "\fB\-F\fR \fIname\fR" 4
422 .Ip "\fB\*(--filter\fR \fIname\fR" 4
423 .IX Item "filter name"
425 When creating an \s-1ELF\s0 shared object, set the internal \s-1DT_FILTER\s0 field to
426 the specified name. This tells the dynamic linker that the symbol table
427 of the shared object which is being created should be used as a filter
428 on the symbol table of the shared object \fIname\fR.
430 If you later link a program against this filter object, then, when you
431 run the program, the dynamic linker will see the \s-1DT_FILTER\s0 field. The
432 dynamic linker will resolve symbols according to the symbol table of the
433 filter object as usual, but it will actually link to the definitions
434 found in the shared object \fIname\fR. Thus the filter object can be
435 used to select a subset of the symbols provided by the object
438 Some older linkers used the \fB\-F\fR option throughout a compilation
439 toolchain for specifying object-file format for both input and output
441 The \s-1GNU\s0 linker uses other mechanisms for this purpose: the
442 \&\fB\-b\fR, \fB\*(--format\fR, \fB\*(--oformat\fR options, the
443 \&\f(CW\*(C`TARGET\*(C'\fR command in linker scripts, and the \f(CW\*(C`GNUTARGET\*(C'\fR
444 environment variable.
445 The \s-1GNU\s0 linker will ignore the \fB\-F\fR option when not
446 creating an \s-1ELF\s0 shared object.
447 .Ip "\fB\-fini\fR \fIname\fR" 4
448 .IX Item "-fini name"
449 When creating an \s-1ELF\s0 executable or shared object, call \s-1NAME\s0 when the
450 executable or shared object is unloaded, by setting \s-1DT_FINI\s0 to the
451 address of the function. By default, the linker uses \f(CW\*(C`_fini\*(C'\fR as
452 the function to call.
455 Ignored. Provided for compatibility with other tools.
456 .Ip "\fB\-G\fR\fIvalue\fR" 4
459 .Ip "\fB\*(--gpsize=\fR\fIvalue\fR" 4
460 .IX Item "gpsize=value"
462 Set the maximum size of objects to be optimized using the \s-1GP\s0 register to
463 \&\fIsize\fR. This is only meaningful for object file formats such as
464 \&\s-1MIPS\s0 \s-1ECOFF\s0 which supports putting large and small objects into different
465 sections. This is ignored for other object file formats.
466 .Ip "\fB\-h\fR\fIname\fR" 4
469 .Ip "\fB\-soname=\fR\fIname\fR" 4
470 .IX Item "-soname=name"
472 When creating an \s-1ELF\s0 shared object, set the internal \s-1DT_SONAME\s0 field to
473 the specified name. When an executable is linked with a shared object
474 which has a \s-1DT_SONAME\s0 field, then when the executable is run the dynamic
475 linker will attempt to load the shared object specified by the \s-1DT_SONAME\s0
476 field rather than the using the file name given to the linker.
479 Perform an incremental link (same as option \fB\-r\fR).
480 .Ip "\fB\-init\fR \fIname\fR" 4
481 .IX Item "-init name"
482 When creating an \s-1ELF\s0 executable or shared object, call \s-1NAME\s0 when the
483 executable or shared object is loaded, by setting \s-1DT_INIT\s0 to the address
484 of the function. By default, the linker uses \f(CW\*(C`_init\*(C'\fR as the
486 .Ip "\fB\-l\fR\fIarchive\fR" 4
489 .Ip "\fB\*(--library=\fR\fIarchive\fR" 4
490 .IX Item "library=archive"
492 Add archive file \fIarchive\fR to the list of files to link. This
493 option may be used any number of times. \fBld\fR will search its
494 path-list for occurrences of \f(CW\*(C`lib\f(CIarchive\f(CW.a\*(C'\fR for every
495 \&\fIarchive\fR specified.
497 On systems which support shared libraries, \fBld\fR may also search for
498 libraries with extensions other than \f(CW\*(C`.a\*(C'\fR. Specifically, on \s-1ELF\s0
499 and SunOS systems, \fBld\fR will search a directory for a library with
500 an extension of \f(CW\*(C`.so\*(C'\fR before searching for one with an extension of
501 \&\f(CW\*(C`.a\*(C'\fR. By convention, a \f(CW\*(C`.so\*(C'\fR extension indicates a shared
504 The linker will search an archive only once, at the location where it is
505 specified on the command line. If the archive defines a symbol which
506 was undefined in some object which appeared before the archive on the
507 command line, the linker will include the appropriate \fIfile\fR\|(s) from the
508 archive. However, an undefined symbol in an object appearing later on
509 the command line will not cause the linker to search the archive again.
511 See the \fB\-(\fR option for a way to force the linker to search
512 archives multiple times.
514 You may list the same archive multiple times on the command line.
516 This type of archive searching is standard for Unix linkers. However,
517 if you are using \fBld\fR on \s-1AIX\s0, note that it is different from the
518 behaviour of the \s-1AIX\s0 linker.
519 .Ip "\fB\-L\fR\fIsearchdir\fR" 4
520 .IX Item "-Lsearchdir"
522 .Ip "\fB\*(--library-path=\fR\fIsearchdir\fR" 4
523 .IX Item "library-path=searchdir"
525 Add path \fIsearchdir\fR to the list of paths that \fBld\fR will search
526 for archive libraries and \fBld\fR control scripts. You may use this
527 option any number of times. The directories are searched in the order
528 in which they are specified on the command line. Directories specified
529 on the command line are searched before the default directories. All
530 \&\fB\-L\fR options apply to all \fB\-l\fR options, regardless of the
531 order in which the options appear.
533 If \fIsearchdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
534 by the \fIsysroot prefix\fR, a path specified when the linker is configured.
536 The default set of paths searched (without being specified with
537 \&\fB\-L\fR) depends on which emulation mode \fBld\fR is using, and in
538 some cases also on how it was configured.
540 The paths can also be specified in a link script with the
541 \&\f(CW\*(C`SEARCH_DIR\*(C'\fR command. Directories specified this way are searched
542 at the point in which the linker script appears in the command line.
543 .Ip "\fB\-m\fR\fIemulation\fR" 4
544 .IX Item "-memulation"
545 Emulate the \fIemulation\fR linker. You can list the available
546 emulations with the \fB\*(--verbose\fR or \fB\-V\fR options.
548 If the \fB\-m\fR option is not used, the emulation is taken from the
549 \&\f(CW\*(C`LDEMULATION\*(C'\fR environment variable, if that is defined.
551 Otherwise, the default emulation depends upon how the linker was
556 .Ip "\fB\*(--print-map\fR" 4
559 Print a link map to the standard output. A link map provides
560 information about the link, including the following:
563 Where object files are mapped into memory.
565 How common symbols are allocated.
567 All archive members included in the link, with a mention of the symbol
568 which caused the archive member to be brought in.
570 The values assigned to symbols.
572 Note \- symbols whose values are computed by an expression which
573 involves a reference to a previous value of the same symbol may not
574 have correct result displayed in the link map. This is because the
575 linker discards intermediate results and only retains the final value
576 of an expression. Under such circumstances the linker will display
577 the final value enclosed by square brackets. Thus for example a
578 linker script containing:
585 will produce the following output in the link map if the \fB\-M\fR
589 \& 0x00000001 foo = 0x1
590 \& [0x0000000c] foo = (foo * 0x4)
591 \& [0x0000000c] foo = (foo + 0x8)
593 See \fBExpressions\fR for more information about expressions in linker
601 .Ip "\fB\*(--nmagic\fR" 4
604 Turn off page alignment of sections, and mark the output as
605 \&\f(CW\*(C`NMAGIC\*(C'\fR if possible.
609 .Ip "\fB\*(--omagic\fR" 4
612 Set the text and data sections to be readable and writable. Also, do
613 not page-align the data segment, and disable linking against shared
614 libraries. If the output format supports Unix style magic numbers,
615 mark the output as \f(CW\*(C`OMAGIC\*(C'\fR. Note: Although a writable text section
616 is allowed for \s-1PE-COFF\s0 targets, it does not conform to the format
617 specification published by Microsoft.
618 .Ip "\fB\*(--no-omagic\fR" 4
620 This option negates most of the effects of the \fB\-N\fR option. It
621 sets the text section to be read-only, and forces the data segment to
622 be page-aligned. Note \- this option does not enable linking against
623 shared libraries. Use \fB\-Bdynamic\fR for this.
624 .Ip "\fB\-o\fR \fIoutput\fR" 4
627 .Ip "\fB\*(--output=\fR\fIoutput\fR" 4
628 .IX Item "output=output"
630 Use \fIoutput\fR as the name for the program produced by \fBld\fR; if this
631 option is not specified, the name \fIa.out\fR is used by default. The
632 script command \f(CW\*(C`OUTPUT\*(C'\fR can also specify the output file name.
633 .Ip "\fB\-O\fR \fIlevel\fR" 4
635 If \fIlevel\fR is a numeric values greater than zero \fBld\fR optimizes
636 the output. This might take significantly longer and therefore probably
637 should only be enabled for the final binary.
641 .Ip "\fB\*(--emit-relocs\fR" 4
642 .IX Item "emit-relocs"
644 Leave relocation sections and contents in fully linked exececutables.
645 Post link analysis and optimization tools may need this information in
646 order to perform correct modifications of executables. This results
647 in larger executables.
649 This option is currently only supported on \s-1ELF\s0 platforms.
653 .Ip "\fB\*(--relocatable\fR" 4
654 .IX Item "relocatable"
656 Generate relocatable output\-\-\-i.e., generate an output file that can in
657 turn serve as input to \fBld\fR. This is often called \fIpartial
658 linking\fR. As a side effect, in environments that support standard Unix
659 magic numbers, this option also sets the output file's magic number to
660 \&\f(CW\*(C`OMAGIC\*(C'\fR.
661 If this option is not specified, an absolute file is produced. When
662 linking \*(C+ programs, this option \fIwill not\fR resolve references to
663 constructors; to do that, use \fB\-Ur\fR.
665 When an input file does not have the same format as the output file,
666 partial linking is only supported if that input file does not contain any
667 relocations. Different output formats can have further restrictions; for
668 example some \f(CW\*(C`a.out\*(C'\fR\-based formats do not support partial linking
669 with input files in other formats at all.
671 This option does the same thing as \fB\-i\fR.
672 .Ip "\fB\-R\fR \fIfilename\fR" 4
673 .IX Item "-R filename"
675 .Ip "\fB\*(--just-symbols=\fR\fIfilename\fR" 4
676 .IX Item "just-symbols=filename"
678 Read symbol names and their addresses from \fIfilename\fR, but do not
679 relocate it or include it in the output. This allows your output file
680 to refer symbolically to absolute locations of memory defined in other
681 programs. You may use this option more than once.
683 For compatibility with other \s-1ELF\s0 linkers, if the \fB\-R\fR option is
684 followed by a directory name, rather than a file name, it is treated as
685 the \fB\-rpath\fR option.
689 .Ip "\fB\*(--strip-all\fR" 4
692 Omit all symbol information from the output file.
696 .Ip "\fB\*(--strip-debug\fR" 4
697 .IX Item "strip-debug"
699 Omit debugger symbol information (but not all symbols) from the output file.
703 .Ip "\fB\*(--trace\fR" 4
706 Print the names of the input files as \fBld\fR processes them.
707 .Ip "\fB\-T\fR \fIscriptfile\fR" 4
708 .IX Item "-T scriptfile"
710 .Ip "\fB\*(--script=\fR\fIscriptfile\fR" 4
711 .IX Item "script=scriptfile"
713 Use \fIscriptfile\fR as the linker script. This script replaces
714 \&\fBld\fR's default linker script (rather than adding to it), so
715 \&\fIcommandfile\fR must specify everything necessary to describe the
716 output file. If \fIscriptfile\fR does not exist in
717 the current directory, \f(CW\*(C`ld\*(C'\fR looks for it in the directories
718 specified by any preceding \fB\-L\fR options. Multiple \fB\-T\fR
720 .Ip "\fB\-u\fR \fIsymbol\fR" 4
723 .Ip "\fB\*(--undefined=\fR\fIsymbol\fR" 4
724 .IX Item "undefined=symbol"
726 Force \fIsymbol\fR to be entered in the output file as an undefined
727 symbol. Doing this may, for example, trigger linking of additional
728 modules from standard libraries. \fB\-u\fR may be repeated with
729 different option arguments to enter additional undefined symbols. This
730 option is equivalent to the \f(CW\*(C`EXTERN\*(C'\fR linker script command.
733 For anything other than \*(C+ programs, this option is equivalent to
734 \&\fB\-r\fR: it generates relocatable output\-\-\-i.e., an output file that can in
735 turn serve as input to \fBld\fR. When linking \*(C+ programs, \fB\-Ur\fR
736 \&\fIdoes\fR resolve references to constructors, unlike \fB\-r\fR.
737 It does not work to use \fB\-Ur\fR on files that were themselves linked
738 with \fB\-Ur\fR; once the constructor table has been built, it cannot
739 be added to. Use \fB\-Ur\fR only for the last partial link, and
740 \&\fB\-r\fR for the others.
741 .Ip "\fB\*(--unique[=\fR\fI\s-1SECTION\s0\fR\fB]\fR" 4
742 .IX Item "unique[=SECTION]"
743 Creates a separate output section for every input section matching
744 \&\fI\s-1SECTION\s0\fR, or if the optional wildcard \fI\s-1SECTION\s0\fR argument is
745 missing, for every orphan input section. An orphan section is one not
746 specifically mentioned in a linker script. You may use this option
747 multiple times on the command line; It prevents the normal merging of
748 input sections with the same name, overriding output section assignments
753 .Ip "\fB\*(--version\fR" 4
758 Display the version number for \fBld\fR. The \fB\-V\fR option also
759 lists the supported emulations.
763 .Ip "\fB\*(--discard-all\fR" 4
764 .IX Item "discard-all"
766 Delete all local symbols.
770 .Ip "\fB\*(--discard-locals\fR" 4
771 .IX Item "discard-locals"
773 Delete all temporary local symbols. For most targets, this is all local
774 symbols whose names begin with \fBL\fR.
775 .Ip "\fB\-y\fR \fIsymbol\fR" 4
778 .Ip "\fB\*(--trace-symbol=\fR\fIsymbol\fR" 4
779 .IX Item "trace-symbol=symbol"
781 Print the name of each linked file in which \fIsymbol\fR appears. This
782 option may be given any number of times. On many systems it is necessary
783 to prepend an underscore.
785 This option is useful when you have an undefined symbol in your link but
786 don't know where the reference is coming from.
787 .Ip "\fB\-Y\fR \fIpath\fR" 4
789 Add \fIpath\fR to the default library search path. This option exists
790 for Solaris compatibility.
791 .Ip "\fB\-z\fR \fIkeyword\fR" 4
792 .IX Item "-z keyword"
793 The recognized keywords are:
795 .Ip "\fBcombreloc\fR" 4
797 Combines multiple reloc sections and sorts them to make dynamic symbol
798 lookup caching possible.
801 Disallows undefined symbols in object files. Undefined symbols in
802 shared libraries are still allowed.
803 .Ip "\fBexecstack\fR" 4
805 Marks the object as requiring executable stack.
806 .Ip "\fBinitfirst\fR" 4
808 This option is only meaningful when building a shared object.
809 It marks the object so that its runtime initialization will occur
810 before the runtime initialization of any other objects brought into
811 the process at the same time. Similarly the runtime finalization of
812 the object will occur after the runtime finalization of any other
814 .Ip "\fBinterpose\fR" 4
816 Marks the object that its symbol table interposes before all symbols
817 but the primary executable.
818 .Ip "\fBloadfltr\fR" 4
820 Marks the object that its filters be processed immediately at
822 .Ip "\fBmuldefs\fR" 4
824 Allows multiple definitions.
825 .Ip "\fBnocombreloc\fR" 4
826 .IX Item "nocombreloc"
827 Disables multiple reloc sections combining.
828 .Ip "\fBnocopyreloc\fR" 4
829 .IX Item "nocopyreloc"
830 Disables production of copy relocs.
831 .Ip "\fBnodefaultlib\fR" 4
832 .IX Item "nodefaultlib"
833 Marks the object that the search for dependencies of this object will
834 ignore any default library search paths.
835 .Ip "\fBnodelete\fR" 4
837 Marks the object shouldn't be unloaded at runtime.
838 .Ip "\fBnodlopen\fR" 4
840 Marks the object not available to \f(CW\*(C`dlopen\*(C'\fR.
843 Marks the object can not be dumped by \f(CW\*(C`dldump\*(C'\fR.
844 .Ip "\fBnoexecstack\fR" 4
845 .IX Item "noexecstack"
846 Marks the object as not requiring executable stack.
847 .Ip "\fBnorelro\fR" 4
849 Don't create an \s-1ELF\s0 \f(CW\*(C`PT_GNU_RELRO\*(C'\fR segment header in the object.
852 When generating an executable or shared library, mark it to tell the
853 dynamic linker to resolve all symbols when the program is started, or
854 when the shared library is linked to using dlopen, instead of
855 deferring function call resolution to the point when the function is
859 Marks the object may contain \f(CW$ORIGIN\fR.
862 Create an \s-1ELF\s0 \f(CW\*(C`PT_GNU_RELRO\*(C'\fR segment header in the object.
866 Other keywords are ignored for Solaris compatibility.
868 .Ip "\fB\-(\fR \fIarchives\fR \fB\-)\fR" 4
869 .IX Item "-( archives -)"
871 .Ip "\fB\*(--start-group\fR \fIarchives\fR \fB\*(--end-group\fR" 4
872 .IX Item "start-group archives end-group"
874 The \fIarchives\fR should be a list of archive files. They may be
875 either explicit file names, or \fB\-l\fR options.
877 The specified archives are searched repeatedly until no new undefined
878 references are created. Normally, an archive is searched only once in
879 the order that it is specified on the command line. If a symbol in that
880 archive is needed to resolve an undefined symbol referred to by an
881 object in an archive that appears later on the command line, the linker
882 would not be able to resolve that reference. By grouping the archives,
883 they all be searched repeatedly until all possible references are
886 Using this option has a significant performance cost. It is best to use
887 it only when there are unavoidable circular references between two or
889 .Ip "\fB\*(--accept-unknown-input-arch\fR" 4
890 .IX Item "accept-unknown-input-arch"
892 .Ip "\fB\*(--no-accept-unknown-input-arch\fR" 4
893 .IX Item "no-accept-unknown-input-arch"
895 Tells the linker to accept input files whose architecture cannot be
896 recognised. The assumption is that the user knows what they are doing
897 and deliberately wants to link in these unknown input files. This was
898 the default behaviour of the linker, before release 2.14. The default
899 behaviour from release 2.14 onwards is to reject such input files, and
900 so the \fB\*(--accept-unknown-input-arch\fR option has been added to
901 restore the old behaviour.
902 .Ip "\fB\*(--as-needed\fR" 4
905 .Ip "\fB\*(--no-as-needed\fR" 4
906 .IX Item "no-as-needed"
908 This option affects \s-1ELF\s0 \s-1DT_NEEDED\s0 tags for dynamic libraries mentioned
909 on the command line after the \fB\*(--as-needed\fR option. Normally,
910 the linker will add a \s-1DT_NEEDED\s0 tag for each dynamic library mentioned
911 on the command line, regardless of whether the library is actually
912 needed. \fB\*(--as-needed\fR causes \s-1DT_NEEDED\s0 tags to only be emitted
913 for libraries that satisfy some symbol reference from regular objects
914 which is undefined at the point that the library was linked.
915 \&\fB\*(--no-as-needed\fR restores the default behaviour.
916 .Ip "\fB\*(--add-needed\fR" 4
917 .IX Item "add-needed"
919 .Ip "\fB\*(--no-add-needed\fR" 4
920 .IX Item "no-add-needed"
922 This option affects the treatment of dynamic libraries from \s-1ELF\s0
923 \&\s-1DT_NEEDED\s0 tags in dynamic libraries mentioned on the command line after
924 the \fB\*(--no-add-needed\fR option. Normally, the linker will add
925 a \s-1DT_NEEDED\s0 tag for each dynamic library from \s-1DT_NEEDED\s0 tags.
926 \&\fB\*(--no-add-needed\fR causes \s-1DT_NEEDED\s0 tags will never be emitted
927 for those libraries from \s-1DT_NEEDED\s0 tags. \fB\*(--add-needed\fR restores
928 the default behaviour.
929 .Ip "\fB\-assert\fR \fIkeyword\fR" 4
930 .IX Item "-assert keyword"
931 This option is ignored for SunOS compatibility.
932 .Ip "\fB\-Bdynamic\fR" 4
937 .Ip "\fB\-call_shared\fR" 4
938 .IX Item "-call_shared"
940 Link against dynamic libraries. This is only meaningful on platforms
941 for which shared libraries are supported. This option is normally the
942 default on such platforms. The different variants of this option are
943 for compatibility with various systems. You may use this option
944 multiple times on the command line: it affects library searching for
945 \&\fB\-l\fR options which follow it.
946 .Ip "\fB\-Bgroup\fR" 4
948 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
949 section. This causes the runtime linker to handle lookups in this
950 object and its dependencies to be performed only inside the group.
951 \&\fB\*(--unresolved-symbols=report-all\fR is implied. This option is
952 only meaningful on \s-1ELF\s0 platforms which support shared libraries.
953 .Ip "\fB\-Bstatic\fR" 4
958 .Ip "\fB\-non_shared\fR" 4
959 .IX Item "-non_shared"
960 .Ip "\fB\-static\fR" 4
963 Do not link against shared libraries. This is only meaningful on
964 platforms for which shared libraries are supported. The different
965 variants of this option are for compatibility with various systems. You
966 may use this option multiple times on the command line: it affects
967 library searching for \fB\-l\fR options which follow it. This
968 option also implies \fB\*(--unresolved-symbols=report-all\fR. This
969 option can be used with \fB\-shared\fR. Doing so means that a
970 shared library is being created but that all of the library's external
971 references must be resolved by pulling in entries from static
973 .Ip "\fB\-Bsymbolic\fR" 4
974 .IX Item "-Bsymbolic"
975 When creating a shared library, bind references to global symbols to the
976 definition within the shared library, if any. Normally, it is possible
977 for a program linked against a shared library to override the definition
978 within the shared library. This option is only meaningful on \s-1ELF\s0
979 platforms which support shared libraries.
980 .Ip "\fB\*(--check-sections\fR" 4
981 .IX Item "check-sections"
983 .Ip "\fB\*(--no-check-sections\fR" 4
984 .IX Item "no-check-sections"
986 Asks the linker \fInot\fR to check section addresses after they have
987 been assigned to see if there any overlaps. Normally the linker will
988 perform this check, and if it finds any overlaps it will produce
989 suitable error messages. The linker does know about, and does make
990 allowances for sections in overlays. The default behaviour can be
991 restored by using the command line switch \fB\*(--check-sections\fR.
992 .Ip "\fB\*(--cref\fR" 4
994 Output a cross reference table. If a linker map file is being
995 generated, the cross reference table is printed to the map file.
996 Otherwise, it is printed on the standard output.
998 The format of the table is intentionally simple, so that it may be
999 easily processed by a script if necessary. The symbols are printed out,
1000 sorted by name. For each symbol, a list of file names is given. If the
1001 symbol is defined, the first file listed is the location of the
1002 definition. The remaining files contain references to the symbol.
1003 .Ip "\fB\*(--no-define-common\fR" 4
1004 .IX Item "no-define-common"
1005 This option inhibits the assignment of addresses to common symbols.
1006 The script command \f(CW\*(C`INHIBIT_COMMON_ALLOCATION\*(C'\fR has the same effect.
1008 The \fB\*(--no-define-common\fR option allows decoupling
1009 the decision to assign addresses to Common symbols from the choice
1010 of the output file type; otherwise a non-Relocatable output type
1011 forces assigning addresses to Common symbols.
1012 Using \fB\*(--no-define-common\fR allows Common symbols that are referenced
1013 from a shared library to be assigned addresses only in the main program.
1014 This eliminates the unused duplicate space in the shared library,
1015 and also prevents any possible confusion over resolving to the wrong
1016 duplicate when there are many dynamic modules with specialized search
1017 paths for runtime symbol resolution.
1018 .Ip "\fB\*(--defsym\fR \fIsymbol\fR\fB=\fR\fIexpression\fR" 4
1019 .IX Item "defsym symbol=expression"
1020 Create a global symbol in the output file, containing the absolute
1021 address given by \fIexpression\fR. You may use this option as many
1022 times as necessary to define multiple symbols in the command line. A
1023 limited form of arithmetic is supported for the \fIexpression\fR in this
1024 context: you may give a hexadecimal constant or the name of an existing
1025 symbol, or use \f(CW\*(C`+\*(C'\fR and \f(CW\*(C`\-\*(C'\fR to add or subtract hexadecimal
1026 constants or symbols. If you need more elaborate expressions, consider
1027 using the linker command language from a script. \fINote:\fR there should be no white
1028 space between \fIsymbol\fR, the equals sign ("\fB=\fR"), and
1030 .Ip "\fB\*(--demangle[=\fR\fIstyle\fR\fB]\fR" 4
1031 .IX Item "demangle[=style]"
1033 .Ip "\fB\*(--no-demangle\fR" 4
1034 .IX Item "no-demangle"
1036 These options control whether to demangle symbol names in error messages
1037 and other output. When the linker is told to demangle, it tries to
1038 present symbol names in a readable fashion: it strips leading
1039 underscores if they are used by the object file format, and converts \*(C+
1040 mangled symbol names into user readable names. Different compilers have
1041 different mangling styles. The optional demangling style argument can be used
1042 to choose an appropriate demangling style for your compiler. The linker will
1043 demangle by default unless the environment variable \fB\s-1COLLECT_NO_DEMANGLE\s0\fR
1044 is set. These options may be used to override the default.
1045 .Ip "\fB\*(--dynamic-linker\fR \fIfile\fR" 4
1046 .IX Item "dynamic-linker file"
1047 Set the name of the dynamic linker. This is only meaningful when
1048 generating dynamically linked \s-1ELF\s0 executables. The default dynamic
1049 linker is normally correct; don't use this unless you know what you are
1051 .Ip "\fB\*(--fatal-warnings\fR" 4
1052 .IX Item "fatal-warnings"
1053 Treat all warnings as errors.
1054 .Ip "\fB\*(--force-exe-suffix\fR" 4
1055 .IX Item "force-exe-suffix"
1056 Make sure that an output file has a .exe suffix.
1058 If a successfully built fully linked output file does not have a
1059 \&\f(CW\*(C`.exe\*(C'\fR or \f(CW\*(C`.dll\*(C'\fR suffix, this option forces the linker to copy
1060 the output file to one of the same name with a \f(CW\*(C`.exe\*(C'\fR suffix. This
1061 option is useful when using unmodified Unix makefiles on a Microsoft
1062 Windows host, since some versions of Windows won't run an image unless
1063 it ends in a \f(CW\*(C`.exe\*(C'\fR suffix.
1064 .Ip "\fB\*(--no-gc-sections\fR" 4
1065 .IX Item "no-gc-sections"
1067 .Ip "\fB\*(--gc-sections\fR" 4
1068 .IX Item "gc-sections"
1070 Enable garbage collection of unused input sections. It is ignored on
1071 targets that do not support this option. This option is not compatible
1072 with \fB\-r\fR. The default behaviour (of not performing this garbage
1073 collection) can be restored by specifying \fB\*(--no-gc-sections\fR on
1075 .Ip "\fB\*(--help\fR" 4
1077 Print a summary of the command-line options on the standard output and exit.
1078 .Ip "\fB\*(--target-help\fR" 4
1079 .IX Item "target-help"
1080 Print a summary of all target specific options on the standard output and exit.
1081 .Ip "\fB\-Map\fR \fImapfile\fR" 4
1082 .IX Item "-Map mapfile"
1083 Print a link map to the file \fImapfile\fR. See the description of the
1084 \&\fB\-M\fR option, above.
1085 .Ip "\fB\*(--no-keep-memory\fR" 4
1086 .IX Item "no-keep-memory"
1087 \&\fBld\fR normally optimizes for speed over memory usage by caching the
1088 symbol tables of input files in memory. This option tells \fBld\fR to
1089 instead optimize for memory usage, by rereading the symbol tables as
1090 necessary. This may be required if \fBld\fR runs out of memory space
1091 while linking a large executable.
1092 .Ip "\fB\*(--no-undefined\fR" 4
1093 .IX Item "no-undefined"
1095 .Ip "\fB\-z defs\fR" 4
1098 Report unresolved symbol references from regular object files. This
1099 is done even if the linker is creating a non-symbolic shared library.
1100 The switch \fB\-\-[no-]allow-shlib-undefined\fR controls the
1101 behaviour for reporting unresolved references found in shared
1102 libraries being linked in.
1103 .Ip "\fB\*(--allow-multiple-definition\fR" 4
1104 .IX Item "allow-multiple-definition"
1106 .Ip "\fB\-z muldefs\fR" 4
1107 .IX Item "-z muldefs"
1109 Normally when a symbol is defined multiple times, the linker will
1110 report a fatal error. These options allow multiple definitions and the
1111 first definition will be used.
1112 .Ip "\fB\*(--allow-shlib-undefined\fR" 4
1113 .IX Item "allow-shlib-undefined"
1115 .Ip "\fB\*(--no-allow-shlib-undefined\fR" 4
1116 .IX Item "no-allow-shlib-undefined"
1118 Allows (the default) or disallows undefined symbols in shared libraries.
1119 This switch is similar to \fB\*(--no-undefined\fR except that it
1120 determines the behaviour when the undefined symbols are in a
1121 shared library rather than a regular object file. It does not affect
1122 how undefined symbols in regular object files are handled.
1124 The reason that \fB\*(--allow-shlib-undefined\fR is the default is that
1125 the shared library being specified at link time may not be the same as
1126 the one that is available at load time, so the symbols might actually be
1127 resolvable at load time. Plus there are some systems, (eg BeOS) where
1128 undefined symbols in shared libraries is normal. (The kernel patches
1129 them at load time to select which function is most appropriate
1130 for the current architecture. This is used for example to dynamically
1131 select an appropriate memset function). Apparently it is also normal
1132 for \s-1HPPA\s0 shared libraries to have undefined symbols.
1133 .Ip "\fB\*(--no-undefined-version\fR" 4
1134 .IX Item "no-undefined-version"
1135 Normally when a symbol has an undefined version, the linker will ignore
1136 it. This option disallows symbols with undefined version and a fatal error
1137 will be issued instead.
1138 .Ip "\fB\*(--default-symver\fR" 4
1139 .IX Item "default-symver"
1140 Create and use a default symbol version (the soname) for unversioned
1142 .Ip "\fB\*(--default-imported-symver\fR" 4
1143 .IX Item "default-imported-symver"
1144 Create and use a default symbol version (the soname) for unversioned
1146 .Ip "\fB\*(--no-warn-mismatch\fR" 4
1147 .IX Item "no-warn-mismatch"
1148 Normally \fBld\fR will give an error if you try to link together input
1149 files that are mismatched for some reason, perhaps because they have
1150 been compiled for different processors or for different endiannesses.
1151 This option tells \fBld\fR that it should silently permit such possible
1152 errors. This option should only be used with care, in cases when you
1153 have taken some special action that ensures that the linker errors are
1155 .Ip "\fB\*(--no-whole-archive\fR" 4
1156 .IX Item "no-whole-archive"
1157 Turn off the effect of the \fB\*(--whole-archive\fR option for subsequent
1159 .Ip "\fB\*(--noinhibit-exec\fR" 4
1160 .IX Item "noinhibit-exec"
1161 Retain the executable output file whenever it is still usable.
1162 Normally, the linker will not produce an output file if it encounters
1163 errors during the link process; it exits without writing an output file
1164 when it issues any error whatsoever.
1165 .Ip "\fB\-nostdlib\fR" 4
1166 .IX Item "-nostdlib"
1167 Only search library directories explicitly specified on the
1168 command line. Library directories specified in linker scripts
1169 (including linker scripts specified on the command line) are ignored.
1170 .Ip "\fB\*(--oformat\fR \fIoutput-format\fR" 4
1171 .IX Item "oformat output-format"
1172 \&\fBld\fR may be configured to support more than one kind of object
1173 file. If your \fBld\fR is configured this way, you can use the
1174 \&\fB\*(--oformat\fR option to specify the binary format for the output
1175 object file. Even when \fBld\fR is configured to support alternative
1176 object formats, you don't usually need to specify this, as \fBld\fR
1177 should be configured to produce as a default output format the most
1178 usual format on each machine. \fIoutput-format\fR is a text string, the
1179 name of a particular format supported by the \s-1BFD\s0 libraries. (You can
1180 list the available binary formats with \fBobjdump \-i\fR.) The script
1181 command \f(CW\*(C`OUTPUT_FORMAT\*(C'\fR can also specify the output format, but
1182 this option overrides it.
1186 .Ip "\fB\*(--pic-executable\fR" 4
1187 .IX Item "pic-executable"
1189 Create a position independent executable. This is currently only supported on
1190 \&\s-1ELF\s0 platforms. Position independent executables are similar to shared
1191 libraries in that they are relocated by the dynamic linker to the virtual
1192 address the \s-1OS\s0 chooses for them (which can vary between invocations). Like
1193 normal dynamically linked executables they can be executed and symbols
1194 defined in the executable cannot be overridden by shared libraries.
1195 .Ip "\fB\-qmagic\fR" 4
1197 This option is ignored for Linux compatibility.
1200 This option is ignored for \s-1SVR4\s0 compatibility.
1201 .Ip "\fB\*(--relax\fR" 4
1203 An option with machine dependent effects.
1204 This option is only supported on a few targets.
1206 On some platforms, the \fB\*(--relax\fR option performs global
1207 optimizations that become possible when the linker resolves addressing
1208 in the program, such as relaxing address modes and synthesizing new
1209 instructions in the output object file.
1211 On some platforms these link time global optimizations may make symbolic
1212 debugging of the resulting executable impossible.
1214 the case for the Matsushita \s-1MN10200\s0 and \s-1MN10300\s0 family of processors.
1216 On platforms where this is not supported, \fB\*(--relax\fR is accepted,
1218 .Ip "\fB\*(--retain-symbols-file\fR \fIfilename\fR" 4
1219 .IX Item "retain-symbols-file filename"
1220 Retain \fIonly\fR the symbols listed in the file \fIfilename\fR,
1221 discarding all others. \fIfilename\fR is simply a flat file, with one
1222 symbol name per line. This option is especially useful in environments
1224 where a large global symbol table is accumulated gradually, to conserve
1227 \&\fB\*(--retain-symbols-file\fR does \fInot\fR discard undefined symbols,
1228 or symbols needed for relocations.
1230 You may only specify \fB\*(--retain-symbols-file\fR once in the command
1231 line. It overrides \fB\-s\fR and \fB\-S\fR.
1232 .Ip "\fB\-rpath\fR \fIdir\fR" 4
1233 .IX Item "-rpath dir"
1234 Add a directory to the runtime library search path. This is used when
1235 linking an \s-1ELF\s0 executable with shared objects. All \fB\-rpath\fR
1236 arguments are concatenated and passed to the runtime linker, which uses
1237 them to locate shared objects at runtime. The \fB\-rpath\fR option is
1238 also used when locating shared objects which are needed by shared
1239 objects explicitly included in the link; see the description of the
1240 \&\fB\-rpath-link\fR option. If \fB\-rpath\fR is not used when linking an
1241 \&\s-1ELF\s0 executable, the contents of the environment variable
1242 \&\f(CW\*(C`LD_RUN_PATH\*(C'\fR will be used if it is defined.
1244 The \fB\-rpath\fR option may also be used on SunOS. By default, on
1245 SunOS, the linker will form a runtime search patch out of all the
1246 \&\fB\-L\fR options it is given. If a \fB\-rpath\fR option is used, the
1247 runtime search path will be formed exclusively using the \fB\-rpath\fR
1248 options, ignoring the \fB\-L\fR options. This can be useful when using
1249 gcc, which adds many \fB\-L\fR options which may be on \s-1NFS\s0 mounted
1252 For compatibility with other \s-1ELF\s0 linkers, if the \fB\-R\fR option is
1253 followed by a directory name, rather than a file name, it is treated as
1254 the \fB\-rpath\fR option.
1255 .Ip "\fB\-rpath-link\fR \fI\s-1DIR\s0\fR" 4
1256 .IX Item "-rpath-link DIR"
1257 When using \s-1ELF\s0 or SunOS, one shared library may require another. This
1258 happens when an \f(CW\*(C`ld \-shared\*(C'\fR link includes a shared library as one
1261 When the linker encounters such a dependency when doing a non-shared,
1262 non-relocatable link, it will automatically try to locate the required
1263 shared library and include it in the link, if it is not included
1264 explicitly. In such a case, the \fB\-rpath-link\fR option
1265 specifies the first set of directories to search. The
1266 \&\fB\-rpath-link\fR option may specify a sequence of directory names
1267 either by specifying a list of names separated by colons, or by
1268 appearing multiple times.
1270 This option should be used with caution as it overrides the search path
1271 that may have been hard compiled into a shared library. In such a case it
1272 is possible to use unintentionally a different search path than the
1273 runtime linker would do.
1275 The linker uses the following search paths to locate required shared
1279 Any directories specified by \fB\-rpath-link\fR options.
1281 Any directories specified by \fB\-rpath\fR options. The difference
1282 between \fB\-rpath\fR and \fB\-rpath-link\fR is that directories
1283 specified by \fB\-rpath\fR options are included in the executable and
1284 used at runtime, whereas the \fB\-rpath-link\fR option is only effective
1285 at link time. It is for the native linker only.
1287 On an \s-1ELF\s0 system, if the \fB\-rpath\fR and \f(CW\*(C`rpath\-link\*(C'\fR options
1288 were not used, search the contents of the environment variable
1289 \&\f(CW\*(C`LD_RUN_PATH\*(C'\fR. It is for the native linker only.
1291 On SunOS, if the \fB\-rpath\fR option was not used, search any
1292 directories specified using \fB\-L\fR options.
1294 For a native linker, the contents of the environment variable
1295 \&\f(CW\*(C`LD_LIBRARY_PATH\*(C'\fR.
1297 For a native \s-1ELF\s0 linker, the directories in \f(CW\*(C`DT_RUNPATH\*(C'\fR or
1298 \&\f(CW\*(C`DT_RPATH\*(C'\fR of a shared library are searched for shared
1299 libraries needed by it. The \f(CW\*(C`DT_RPATH\*(C'\fR entries are ignored if
1300 \&\f(CW\*(C`DT_RUNPATH\*(C'\fR entries exist.
1302 The default directories, normally \fI/lib\fR and \fI/usr/lib\fR.
1304 For a native linker on an \s-1ELF\s0 system, if the file \fI/etc/ld.so.conf\fR
1305 exists, the list of directories found in that file.
1309 If the required shared library is not found, the linker will issue a
1310 warning and continue with the link.
1312 .Ip "\fB\-shared\fR" 4
1315 .Ip "\fB\-Bshareable\fR" 4
1316 .IX Item "-Bshareable"
1318 Create a shared library. This is currently only supported on \s-1ELF\s0, \s-1XCOFF\s0
1319 and SunOS platforms. On SunOS, the linker will automatically create a
1320 shared library if the \fB\-e\fR option is not used and there are
1321 undefined symbols in the link.
1322 .Ip "\fB\*(--sort-common\fR" 4
1323 .IX Item "sort-common"
1324 This option tells \fBld\fR to sort the common symbols by size when it
1325 places them in the appropriate output sections. First come all the one
1326 byte symbols, then all the two byte, then all the four byte, and then
1327 everything else. This is to prevent gaps between symbols due to
1328 alignment constraints.
1329 .Ip "\fB\*(--sort-section name\fR" 4
1330 .IX Item "sort-section name"
1331 This option will apply \f(CW\*(C`SORT_BY_NAME\*(C'\fR to all wildcard section
1332 patterns in the linker script.
1333 .Ip "\fB\*(--sort-section alignment\fR" 4
1334 .IX Item "sort-section alignment"
1335 This option will apply \f(CW\*(C`SORT_BY_ALIGNMENT\*(C'\fR to all wildcard section
1336 patterns in the linker script.
1337 .Ip "\fB\*(--split-by-file [\fR\fIsize\fR\fB]\fR" 4
1338 .IX Item "split-by-file [size]"
1339 Similar to \fB\*(--split-by-reloc\fR but creates a new output section for
1340 each input file when \fIsize\fR is reached. \fIsize\fR defaults to a
1341 size of 1 if not given.
1342 .Ip "\fB\*(--split-by-reloc [\fR\fIcount\fR\fB]\fR" 4
1343 .IX Item "split-by-reloc [count]"
1344 Tries to creates extra sections in the output file so that no single
1345 output section in the file contains more than \fIcount\fR relocations.
1346 This is useful when generating huge relocatable files for downloading into
1347 certain real time kernels with the \s-1COFF\s0 object file format; since \s-1COFF\s0
1348 cannot represent more than 65535 relocations in a single section. Note
1349 that this will fail to work with object file formats which do not
1350 support arbitrary sections. The linker will not split up individual
1351 input sections for redistribution, so if a single input section contains
1352 more than \fIcount\fR relocations one output section will contain that
1353 many relocations. \fIcount\fR defaults to a value of 32768.
1354 .Ip "\fB\*(--stats\fR" 4
1356 Compute and display statistics about the operation of the linker, such
1357 as execution time and memory usage.
1358 .Ip "\fB\*(--sysroot=\fR\fIdirectory\fR" 4
1359 .IX Item "sysroot=directory"
1360 Use \fIdirectory\fR as the location of the sysroot, overriding the
1361 configure-time default. This option is only supported by linkers
1362 that were configured using \fB\*(--with-sysroot\fR.
1363 .Ip "\fB\*(--traditional-format\fR" 4
1364 .IX Item "traditional-format"
1365 For some targets, the output of \fBld\fR is different in some ways from
1366 the output of some existing linker. This switch requests \fBld\fR to
1367 use the traditional format instead.
1369 For example, on SunOS, \fBld\fR combines duplicate entries in the
1370 symbol string table. This can reduce the size of an output file with
1371 full debugging information by over 30 percent. Unfortunately, the SunOS
1372 \&\f(CW\*(C`dbx\*(C'\fR program can not read the resulting program (\f(CW\*(C`gdb\*(C'\fR has no
1373 trouble). The \fB\*(--traditional-format\fR switch tells \fBld\fR to not
1374 combine duplicate entries.
1375 .Ip "\fB\*(--section-start\fR \fIsectionname\fR\fB=\fR\fIorg\fR" 4
1376 .IX Item "section-start sectionname=org"
1377 Locate a section in the output file at the absolute
1378 address given by \fIorg\fR. You may use this option as many
1379 times as necessary to locate multiple sections in the command
1381 \&\fIorg\fR must be a single hexadecimal integer;
1382 for compatibility with other linkers, you may omit the leading
1383 \&\fB0x\fR usually associated with hexadecimal values. \fINote:\fR there
1384 should be no white space between \fIsectionname\fR, the equals
1385 sign ("\fB=\fR"), and \fIorg\fR.
1386 .Ip "\fB\-Tbss\fR \fIorg\fR" 4
1387 .IX Item "-Tbss org"
1389 .Ip "\fB\-Tdata\fR \fIorg\fR" 4
1390 .IX Item "-Tdata org"
1391 .Ip "\fB\-Ttext\fR \fIorg\fR" 4
1392 .IX Item "-Ttext org"
1394 Same as \-\-section-start, with \f(CW\*(C`.bss\*(C'\fR, \f(CW\*(C`.data\*(C'\fR or
1395 \&\f(CW\*(C`.text\*(C'\fR as the \fIsectionname\fR.
1396 .Ip "\fB\*(--unresolved-symbols=\fR\fImethod\fR" 4
1397 .IX Item "unresolved-symbols=method"
1398 Determine how to handle unresolved symbols. There are four possible
1399 values for \fBmethod\fR:
1401 .Ip "\fBignore-all\fR" 4
1402 .IX Item "ignore-all"
1403 Do not report any unresolved symbols.
1404 .Ip "\fBreport-all\fR" 4
1405 .IX Item "report-all"
1406 Report all unresolved symbols. This is the default.
1407 .Ip "\fBignore-in-object-files\fR" 4
1408 .IX Item "ignore-in-object-files"
1409 Report unresolved symbols that are contained in shared libraries, but
1410 ignore them if they come from regular object files.
1411 .Ip "\fBignore-in-shared-libs\fR" 4
1412 .IX Item "ignore-in-shared-libs"
1413 Report unresolved symbols that come from regular object files, but
1414 ignore them if they come from shared libraries. This can be useful
1415 when creating a dynamic binary and it is known that all the shared
1416 libraries that it should be referencing are included on the linker's
1421 The behaviour for shared libraries on their own can also be controlled
1422 by the \fB\-\-[no-]allow-shlib-undefined\fR option.
1424 Normally the linker will generate an error message for each reported
1425 unresolved symbol but the option \fB\*(--warn-unresolved-symbols\fR
1426 can change this to a warning.
1428 .Ip "\fB\*(--dll-verbose\fR" 4
1429 .IX Item "dll-verbose"
1431 .Ip "\fB\*(--verbose\fR" 4
1434 Display the version number for \fBld\fR and list the linker emulations
1435 supported. Display which input files can and cannot be opened. Display
1436 the linker script being used by the linker.
1437 .Ip "\fB\*(--version-script=\fR\fIversion-scriptfile\fR" 4
1438 .IX Item "version-script=version-scriptfile"
1439 Specify the name of a version script to the linker. This is typically
1440 used when creating shared libraries to specify additional information
1441 about the version hierarchy for the library being created. This option
1442 is only meaningful on \s-1ELF\s0 platforms which support shared libraries.
1443 .Ip "\fB\*(--warn-common\fR" 4
1444 .IX Item "warn-common"
1445 Warn when a common symbol is combined with another common symbol or with
1446 a symbol definition. Unix linkers allow this somewhat sloppy practise,
1447 but linkers on some other operating systems do not. This option allows
1448 you to find potential problems from combining global symbols.
1449 Unfortunately, some C libraries use this practise, so you may get some
1450 warnings about symbols in the libraries as well as in your programs.
1452 There are three kinds of global symbols, illustrated here by C examples:
1454 .Ip "\fBint i = 1;\fR" 4
1455 .IX Item "int i = 1;"
1456 A definition, which goes in the initialized data section of the output
1458 .Ip "\fBextern int i;\fR" 4
1459 .IX Item "extern int i;"
1460 An undefined reference, which does not allocate space.
1461 There must be either a definition or a common symbol for the
1463 .Ip "\fBint i;\fR" 4
1465 A common symbol. If there are only (one or more) common symbols for a
1466 variable, it goes in the uninitialized data area of the output file.
1467 The linker merges multiple common symbols for the same variable into a
1468 single symbol. If they are of different sizes, it picks the largest
1469 size. The linker turns a common symbol into a declaration, if there is
1470 a definition of the same variable.
1474 The \fB\*(--warn-common\fR option can produce five kinds of warnings.
1475 Each warning consists of a pair of lines: the first describes the symbol
1476 just encountered, and the second describes the previous symbol
1477 encountered with the same name. One or both of the two symbols will be
1482 Turning a common symbol into a reference, because there is already a
1483 definition for the symbol.
1486 \& <file>(<section>): warning: common of `<symbol>'
1487 \& overridden by definition
1488 \& <file>(<section>): warning: defined here
1491 Turning a common symbol into a reference, because a later definition for
1492 the symbol is encountered. This is the same as the previous case,
1493 except that the symbols are encountered in a different order.
1496 \& <file>(<section>): warning: definition of `<symbol>'
1497 \& overriding common
1498 \& <file>(<section>): warning: common is here
1501 Merging a common symbol with a previous same-sized common symbol.
1504 \& <file>(<section>): warning: multiple common
1506 \& <file>(<section>): warning: previous common is here
1509 Merging a common symbol with a previous larger common symbol.
1512 \& <file>(<section>): warning: common of `<symbol>'
1513 \& overridden by larger common
1514 \& <file>(<section>): warning: larger common is here
1517 Merging a common symbol with a previous smaller common symbol. This is
1518 the same as the previous case, except that the symbols are
1519 encountered in a different order.
1522 \& <file>(<section>): warning: common of `<symbol>'
1523 \& overriding smaller common
1524 \& <file>(<section>): warning: smaller common is here
1529 .Ip "\fB\*(--warn-constructors\fR" 4
1530 .IX Item "warn-constructors"
1531 Warn if any global constructors are used. This is only useful for a few
1532 object file formats. For formats like \s-1COFF\s0 or \s-1ELF\s0, the linker can not
1533 detect the use of global constructors.
1534 .Ip "\fB\*(--warn-multiple-gp\fR" 4
1535 .IX Item "warn-multiple-gp"
1536 Warn if multiple global pointer values are required in the output file.
1537 This is only meaningful for certain processors, such as the Alpha.
1538 Specifically, some processors put large-valued constants in a special
1539 section. A special register (the global pointer) points into the middle
1540 of this section, so that constants can be loaded efficiently via a
1541 base-register relative addressing mode. Since the offset in
1542 base-register relative mode is fixed and relatively small (e.g., 16
1543 bits), this limits the maximum size of the constant pool. Thus, in
1544 large programs, it is often necessary to use multiple global pointer
1545 values in order to be able to address all possible constants. This
1546 option causes a warning to be issued whenever this case occurs.
1547 .Ip "\fB\*(--warn-once\fR" 4
1548 .IX Item "warn-once"
1549 Only warn once for each undefined symbol, rather than once per module
1551 .Ip "\fB\*(--warn-section-align\fR" 4
1552 .IX Item "warn-section-align"
1553 Warn if the address of an output section is changed because of
1554 alignment. Typically, the alignment will be set by an input section.
1555 The address will only be changed if it not explicitly specified; that
1556 is, if the \f(CW\*(C`SECTIONS\*(C'\fR command does not specify a start address for
1558 .Ip "\fB\*(--warn-shared-textrel\fR" 4
1559 .IX Item "warn-shared-textrel"
1560 Warn if the linker adds a \s-1DT_TEXTREL\s0 to a shared object.
1561 .Ip "\fB\*(--warn-unresolved-symbols\fR" 4
1562 .IX Item "warn-unresolved-symbols"
1563 If the linker is going to report an unresolved symbol (see the option
1564 \&\fB\*(--unresolved-symbols\fR) it will normally generate an error.
1565 This option makes it generate a warning instead.
1566 .Ip "\fB\*(--error-unresolved-symbols\fR" 4
1567 .IX Item "error-unresolved-symbols"
1568 This restores the linker's default behaviour of generating errors when
1569 it is reporting unresolved symbols.
1570 .Ip "\fB\*(--whole-archive\fR" 4
1571 .IX Item "whole-archive"
1572 For each archive mentioned on the command line after the
1573 \&\fB\*(--whole-archive\fR option, include every object file in the archive
1574 in the link, rather than searching the archive for the required object
1575 files. This is normally used to turn an archive file into a shared
1576 library, forcing every object to be included in the resulting shared
1577 library. This option may be used more than once.
1579 Two notes when using this option from gcc: First, gcc doesn't know
1580 about this option, so you have to use \fB\-Wl,\-whole-archive\fR.
1581 Second, don't forget to use \fB\-Wl,\-no-whole-archive\fR after your
1582 list of archives, because gcc will add its own list of archives to
1583 your link and you may not want this flag to affect those as well.
1584 .Ip "\fB\*(--wrap\fR \fIsymbol\fR" 4
1585 .IX Item "wrap symbol"
1586 Use a wrapper function for \fIsymbol\fR. Any undefined reference to
1587 \&\fIsymbol\fR will be resolved to \f(CW\*(C`_\|_wrap_\f(CIsymbol\f(CW\*(C'\fR. Any
1588 undefined reference to \f(CW\*(C`_\|_real_\f(CIsymbol\f(CW\*(C'\fR will be resolved to
1591 This can be used to provide a wrapper for a system function. The
1592 wrapper function should be called \f(CW\*(C`_\|_wrap_\f(CIsymbol\f(CW\*(C'\fR. If it
1593 wishes to call the system function, it should call
1594 \&\f(CW\*(C`_\|_real_\f(CIsymbol\f(CW\*(C'\fR.
1596 Here is a trivial example:
1600 \& __wrap_malloc (size_t c)
1602 \& printf ("malloc called with %zu\en", c);
1603 \& return __real_malloc (c);
1606 If you link other code with this file using \fB\*(--wrap malloc\fR, then
1607 all calls to \f(CW\*(C`malloc\*(C'\fR will call the function \f(CW\*(C`_\|_wrap_malloc\*(C'\fR
1608 instead. The call to \f(CW\*(C`_\|_real_malloc\*(C'\fR in \f(CW\*(C`_\|_wrap_malloc\*(C'\fR will
1609 call the real \f(CW\*(C`malloc\*(C'\fR function.
1611 You may wish to provide a \f(CW\*(C`_\|_real_malloc\*(C'\fR function as well, so that
1612 links without the \fB\*(--wrap\fR option will succeed. If you do this,
1613 you should not put the definition of \f(CW\*(C`_\|_real_malloc\*(C'\fR in the same
1614 file as \f(CW\*(C`_\|_wrap_malloc\*(C'\fR; if you do, the assembler may resolve the
1615 call before the linker has a chance to wrap it to \f(CW\*(C`malloc\*(C'\fR.
1616 .Ip "\fB\*(--eh-frame-hdr\fR" 4
1617 .IX Item "eh-frame-hdr"
1618 Request creation of \f(CW\*(C`.eh_frame_hdr\*(C'\fR section and \s-1ELF\s0
1619 \&\f(CW\*(C`PT_GNU_EH_FRAME\*(C'\fR segment header.
1620 .Ip "\fB\*(--enable-new-dtags\fR" 4
1621 .IX Item "enable-new-dtags"
1623 .Ip "\fB\*(--disable-new-dtags\fR" 4
1624 .IX Item "disable-new-dtags"
1626 This linker can create the new dynamic tags in \s-1ELF\s0. But the older \s-1ELF\s0
1627 systems may not understand them. If you specify
1628 \&\fB\*(--enable-new-dtags\fR, the dynamic tags will be created as needed.
1629 If you specify \fB\*(--disable-new-dtags\fR, no new dynamic tags will be
1630 created. By default, the new dynamic tags are not created. Note that
1631 those options are only available for \s-1ELF\s0 systems.
1632 .Ip "\fB\*(--hash-size=\fR\fInumber\fR" 4
1633 .IX Item "hash-size=number"
1634 Set the default size of the linker's hash tables to a prime number
1635 close to \fInumber\fR. Increasing this value can reduce the length of
1636 time it takes the linker to perform its tasks, at the expense of
1637 increasing the linker's memory requirements. Similarly reducing this
1638 value can reduce the memory requirements at the expense of speed.
1639 .Ip "\fB\*(--reduce-memory-overheads\fR" 4
1640 .IX Item "reduce-memory-overheads"
1641 This option reduces memory requirements at ld runtime, at the expense of
1642 linking speed. This was introduced to select the old O(n^2) algorithm
1643 for link map file generation, rather than the new O(n) algorithm which uses
1644 about 40% more memory for symbol storage.
1646 Another effect of the switch is to set the default hash table size to
1647 1021, which again saves memory at the cost of lengthening the linker's
1648 run time. This is not done however if the \fB\*(--hash-size\fR switch
1651 The \fB\*(--reduce-memory-overheads\fR switch may be also be used to
1652 enable other tradeoffs in future versions of the linker.
1654 The i386 \s-1PE\s0 linker supports the \fB\-shared\fR option, which causes
1655 the output to be a dynamically linked library (\s-1DLL\s0) instead of a
1656 normal executable. You should name the output \f(CW\*(C`*.dll\*(C'\fR when you
1657 use this option. In addition, the linker fully supports the standard
1658 \&\f(CW\*(C`*.def\*(C'\fR files, which may be specified on the linker command line
1659 like an object file (in fact, it should precede archives it exports
1660 symbols from, to ensure that they get linked in, just like a normal
1663 The \fB\-shared\fR option creates a relocatable \s-1DLL\s0. To convert a
1664 relocatable \s-1DLL\s0 to a non-relocatable one, strip the \f(CW\*(C`.reloc\*(C'\fR section
1668 \& strip -R .reloc <foo.dll>
1670 In addition to the options common to all targets, the i386 \s-1PE\s0 linker
1671 support additional command line options that are specific to the i386
1672 \&\s-1PE\s0 target. Options that take values may be separated from their
1673 values by either a space or an equals sign.
1674 .Ip "\fB\*(--add-stdcall-alias\fR" 4
1675 .IX Item "add-stdcall-alias"
1676 If given, symbols with a stdcall suffix (@\fInn\fR) will be exported
1677 as-is and also with the suffix stripped.
1678 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1679 .Ip "\fB\*(--base-file\fR \fIfile\fR" 4
1680 .IX Item "base-file file"
1681 Use \fIfile\fR as the name of a file in which to save the base
1682 addresses of all the relocations needed for generating DLLs with
1684 [This is an i386 \s-1PE\s0 specific option]
1685 .Ip "\fB\*(--dll\fR" 4
1687 Create a \s-1DLL\s0 instead of a regular executable. You may also use
1688 \&\fB\-shared\fR or specify a \f(CW\*(C`LIBRARY\*(C'\fR in a given \f(CW\*(C`.def\*(C'\fR
1690 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1691 .Ip "\fB\*(--enable-stdcall-fixup\fR" 4
1692 .IX Item "enable-stdcall-fixup"
1694 .Ip "\fB\*(--disable-stdcall-fixup\fR" 4
1695 .IX Item "disable-stdcall-fixup"
1697 If the link finds a symbol that it cannot resolve, it will attempt to
1698 do \*(L"fuzzy linking\*(R" by looking for another defined symbol that differs
1699 only in the format of the symbol name (cdecl vs stdcall) and will
1700 resolve that symbol by linking to the match. For example, the
1701 undefined symbol \f(CW\*(C`_foo\*(C'\fR might be linked to the function
1702 \&\f(CW\*(C`_foo@12\*(C'\fR, or the undefined symbol \f(CW\*(C`_bar@16\*(C'\fR might be linked
1703 to the function \f(CW\*(C`_bar\*(C'\fR. When the linker does this, it prints a
1704 warning, since it normally should have failed to link, but sometimes
1705 import libraries generated from third-party dlls may need this feature
1706 to be usable. If you specify \fB\*(--enable-stdcall-fixup\fR, this
1707 feature is fully enabled and warnings are not printed. If you specify
1708 \&\fB\*(--disable-stdcall-fixup\fR, this feature is disabled and such
1709 mismatches are considered to be errors.
1710 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1711 .Ip "\fB\*(--export-all-symbols\fR" 4
1712 .IX Item "export-all-symbols"
1713 If given, all global symbols in the objects used to build a \s-1DLL\s0 will
1714 be exported by the \s-1DLL\s0. Note that this is the default if there
1715 otherwise wouldn't be any exported symbols. When symbols are
1716 explicitly exported via \s-1DEF\s0 files or implicitly exported via function
1717 attributes, the default is to not export anything else unless this
1718 option is given. Note that the symbols \f(CW\*(C`DllMain@12\*(C'\fR,
1719 \&\f(CW\*(C`DllEntryPoint@0\*(C'\fR, \f(CW\*(C`DllMainCRTStartup@12\*(C'\fR, and
1720 \&\f(CW\*(C`impure_ptr\*(C'\fR will not be automatically
1721 exported. Also, symbols imported from other DLLs will not be
1722 re-exported, nor will symbols specifying the \s-1DLL\s0's internal layout
1723 such as those beginning with \f(CW\*(C`_head_\*(C'\fR or ending with
1724 \&\f(CW\*(C`_iname\*(C'\fR. In addition, no symbols from \f(CW\*(C`libgcc\*(C'\fR,
1725 \&\f(CW\*(C`libstd++\*(C'\fR, \f(CW\*(C`libmingw32\*(C'\fR, or \f(CW\*(C`crtX.o\*(C'\fR will be exported.
1726 Symbols whose names begin with \f(CW\*(C`_\|_rtti_\*(C'\fR or \f(CW\*(C`_\|_builtin_\*(C'\fR will
1727 not be exported, to help with \*(C+ DLLs. Finally, there is an
1728 extensive list of cygwin-private symbols that are not exported
1729 (obviously, this applies on when building DLLs for cygwin targets).
1730 These cygwin-excludes are: \f(CW\*(C`_cygwin_dll_entry@12\*(C'\fR,
1731 \&\f(CW\*(C`_cygwin_crt0_common@8\*(C'\fR, \f(CW\*(C`_cygwin_noncygwin_dll_entry@12\*(C'\fR,
1732 \&\f(CW\*(C`_fmode\*(C'\fR, \f(CW\*(C`_impure_ptr\*(C'\fR, \f(CW\*(C`cygwin_attach_dll\*(C'\fR,
1733 \&\f(CW\*(C`cygwin_premain0\*(C'\fR, \f(CW\*(C`cygwin_premain1\*(C'\fR, \f(CW\*(C`cygwin_premain2\*(C'\fR,
1734 \&\f(CW\*(C`cygwin_premain3\*(C'\fR, and \f(CW\*(C`environ\*(C'\fR.
1735 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1736 .Ip "\fB\*(--exclude-symbols\fR \fIsymbol\fR\fB,\fR\fIsymbol\fR\fB,...\fR" 4
1737 .IX Item "exclude-symbols symbol,symbol,..."
1738 Specifies a list of symbols which should not be automatically
1739 exported. The symbol names may be delimited by commas or colons.
1740 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1741 .Ip "\fB\*(--file-alignment\fR" 4
1742 .IX Item "file-alignment"
1743 Specify the file alignment. Sections in the file will always begin at
1744 file offsets which are multiples of this number. This defaults to
1746 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1747 .Ip "\fB\*(--heap\fR \fIreserve\fR" 4
1748 .IX Item "heap reserve"
1750 .Ip "\fB\*(--heap\fR \fIreserve\fR\fB,\fR\fIcommit\fR" 4
1751 .IX Item "heap reserve,commit"
1753 Specify the amount of memory to reserve (and optionally commit) to be
1754 used as heap for this program. The default is 1Mb reserved, 4K
1756 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1757 .Ip "\fB\*(--image-base\fR \fIvalue\fR" 4
1758 .IX Item "image-base value"
1759 Use \fIvalue\fR as the base address of your program or dll. This is
1760 the lowest memory location that will be used when your program or dll
1761 is loaded. To reduce the need to relocate and improve performance of
1762 your dlls, each should have a unique base address and not overlap any
1763 other dlls. The default is 0x400000 for executables, and 0x10000000
1765 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1766 .Ip "\fB\*(--kill-at\fR" 4
1768 If given, the stdcall suffixes (@\fInn\fR) will be stripped from
1769 symbols before they are exported.
1770 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1771 .Ip "\fB\*(--large-address-aware\fR" 4
1772 .IX Item "large-address-aware"
1773 If given, the appropriate bit in the \*(L"Charateristics\*(R" field of the \s-1COFF\s0
1774 header is set to indicate that this executable supports virtual addresses
1775 greater than 2 gigabytes. This should be used in conjuction with the /3GB
1776 or /USERVA=\fIvalue\fR megabytes switch in the \*(L"[operating systems]\*(R"
1777 section of the \s-1BOOT\s0.INI. Otherwise, this bit has no effect.
1778 [This option is specific to \s-1PE\s0 targeted ports of the linker]
1779 .Ip "\fB\*(--major-image-version\fR \fIvalue\fR" 4
1780 .IX Item "major-image-version value"
1781 Sets the major number of the \*(L"image version\*(R". Defaults to 1.
1782 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1783 .Ip "\fB\*(--major-os-version\fR \fIvalue\fR" 4
1784 .IX Item "major-os-version value"
1785 Sets the major number of the \*(L"os version\*(R". Defaults to 4.
1786 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1787 .Ip "\fB\*(--major-subsystem-version\fR \fIvalue\fR" 4
1788 .IX Item "major-subsystem-version value"
1789 Sets the major number of the \*(L"subsystem version\*(R". Defaults to 4.
1790 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1791 .Ip "\fB\*(--minor-image-version\fR \fIvalue\fR" 4
1792 .IX Item "minor-image-version value"
1793 Sets the minor number of the \*(L"image version\*(R". Defaults to 0.
1794 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1795 .Ip "\fB\*(--minor-os-version\fR \fIvalue\fR" 4
1796 .IX Item "minor-os-version value"
1797 Sets the minor number of the \*(L"os version\*(R". Defaults to 0.
1798 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1799 .Ip "\fB\*(--minor-subsystem-version\fR \fIvalue\fR" 4
1800 .IX Item "minor-subsystem-version value"
1801 Sets the minor number of the \*(L"subsystem version\*(R". Defaults to 0.
1802 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1803 .Ip "\fB\*(--output-def\fR \fIfile\fR" 4
1804 .IX Item "output-def file"
1805 The linker will create the file \fIfile\fR which will contain a \s-1DEF\s0
1806 file corresponding to the \s-1DLL\s0 the linker is generating. This \s-1DEF\s0 file
1807 (which should be called \f(CW\*(C`*.def\*(C'\fR) may be used to create an import
1808 library with \f(CW\*(C`dlltool\*(C'\fR or may be used as a reference to
1809 automatically or implicitly exported symbols.
1810 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1811 .Ip "\fB\*(--out-implib\fR \fIfile\fR" 4
1812 .IX Item "out-implib file"
1813 The linker will create the file \fIfile\fR which will contain an
1814 import lib corresponding to the \s-1DLL\s0 the linker is generating. This
1815 import lib (which should be called \f(CW\*(C`*.dll.a\*(C'\fR or \f(CW\*(C`*.a\*(C'\fR
1816 may be used to link clients against the generated \s-1DLL\s0; this behaviour
1817 makes it possible to skip a separate \f(CW\*(C`dlltool\*(C'\fR import library
1819 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1820 .Ip "\fB\*(--enable-auto-image-base\fR" 4
1821 .IX Item "enable-auto-image-base"
1822 Automatically choose the image base for DLLs, unless one is specified
1823 using the \f(CW\*(C`\-\-image\-base\*(C'\fR argument. By using a hash generated
1824 from the dllname to create unique image bases for each \s-1DLL\s0, in-memory
1825 collisions and relocations which can delay program execution are
1827 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1828 .Ip "\fB\*(--disable-auto-image-base\fR" 4
1829 .IX Item "disable-auto-image-base"
1830 Do not automatically generate a unique image base. If there is no
1831 user-specified image base (\f(CW\*(C`\-\-image\-base\*(C'\fR) then use the platform
1833 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1834 .Ip "\fB\*(--dll-search-prefix\fR \fIstring\fR" 4
1835 .IX Item "dll-search-prefix string"
1836 When linking dynamically to a dll without an import library,
1837 search for \f(CW\*(C`<string><basename>.dll\*(C'\fR in preference to
1838 \&\f(CW\*(C`lib<basename>.dll\*(C'\fR. This behaviour allows easy distinction
1839 between DLLs built for the various \*(L"subplatforms\*(R": native, cygwin,
1840 uwin, pw, etc. For instance, cygwin DLLs typically use
1841 \&\f(CW\*(C`\-\-dll\-search\-prefix=cyg\*(C'\fR.
1842 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1843 .Ip "\fB\*(--enable-auto-import\fR" 4
1844 .IX Item "enable-auto-import"
1845 Do sophisticated linking of \f(CW\*(C`_symbol\*(C'\fR to \f(CW\*(C`_\|_imp_\|_symbol\*(C'\fR for
1846 \&\s-1DATA\s0 imports from DLLs, and create the necessary thunking symbols when
1847 building the import libraries with those \s-1DATA\s0 exports. Note: Use of the
1848 \&'auto-import' extension will cause the text section of the image file
1849 to be made writable. This does not conform to the \s-1PE-COFF\s0 format
1850 specification published by Microsoft.
1852 Using 'auto-import' generally will 'just work' \*(-- but sometimes you may
1855 "variable '<var>' can't be auto-imported. Please read the
1856 documentation for ld's \f(CW\*(C`\-\-enable\-auto\-import\*(C'\fR for details."
1858 This message occurs when some (sub)expression accesses an address
1859 ultimately given by the sum of two constants (Win32 import tables only
1860 allow one). Instances where this may occur include accesses to member
1861 fields of struct variables imported from a \s-1DLL\s0, as well as using a
1862 constant index into an array variable imported from a \s-1DLL\s0. Any
1863 multiword variable (arrays, structs, long long, etc) may trigger
1864 this error condition. However, regardless of the exact data type
1865 of the offending exported variable, ld will always detect it, issue
1866 the warning, and exit.
1868 There are several ways to address this difficulty, regardless of the
1869 data type of the exported variable:
1871 One way is to use \-\-enable-runtime-pseudo-reloc switch. This leaves the task
1872 of adjusting references in your client code for runtime environment, so
1873 this method works only when runtime environment supports this feature.
1875 A second solution is to force one of the 'constants' to be a variable \*(--
1876 that is, unknown and un-optimizable at compile time. For arrays,
1877 there are two possibilities: a) make the indexee (the array's address)
1878 a variable, or b) make the 'constant' index a variable. Thus:
1881 \& extern type extern_array[];
1882 \& extern_array[1] -->
1883 \& { volatile type *t=extern_array; t[1] }
1888 \& extern type extern_array[];
1889 \& extern_array[1] -->
1890 \& { volatile int t=1; extern_array[t] }
1892 For structs (and most other multiword data types) the only option
1893 is to make the struct itself (or the long long, or the ...) variable:
1896 \& extern struct s extern_struct;
1897 \& extern_struct.field -->
1898 \& { volatile struct s *t=&extern_struct; t->field }
1903 \& extern long long extern_ll;
1905 \& { volatile long long * local_ll=&extern_ll; *local_ll }
1907 A third method of dealing with this difficulty is to abandon
1908 \&'auto-import' for the offending symbol and mark it with
1909 \&\f(CW\*(C`_\|_declspec(dllimport)\*(C'\fR. However, in practise that
1910 requires using compile-time #defines to indicate whether you are
1911 building a \s-1DLL\s0, building client code that will link to the \s-1DLL\s0, or
1912 merely building/linking to a static library. In making the choice
1913 between the various methods of resolving the 'direct address with
1914 constant offset' problem, you should consider typical real-world usage:
1920 \& extern int arr[];
1923 \& void main(int argc, char **argv){
1924 \& printf("%d\en",arr[1]);
1931 \& extern int arr[];
1934 \& void main(int argc, char **argv){
1935 \& /* This workaround is for win32 and cygwin; do not "optimize" */
1936 \& volatile int *parr = arr;
1937 \& printf("%d\en",parr[1]);
1944 \& /* Note: auto-export is assumed (no __declspec(dllexport)) */
1945 \& #if (defined(_WIN32) || defined(__CYGWIN__)) && \e
1946 \& !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
1947 \& #define FOO_IMPORT __declspec(dllimport)
1949 \& #define FOO_IMPORT
1951 \& extern FOO_IMPORT int arr[];
1954 \& void main(int argc, char **argv){
1955 \& printf("%d\en",arr[1]);
1958 A fourth way to avoid this problem is to re-code your
1959 library to use a functional interface rather than a data interface
1960 for the offending variables (e.g. \fIset_foo()\fR and \fIget_foo()\fR accessor
1962 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1963 .Ip "\fB\*(--disable-auto-import\fR" 4
1964 .IX Item "disable-auto-import"
1965 Do not attempt to do sophisticated linking of \f(CW\*(C`_symbol\*(C'\fR to
1966 \&\f(CW\*(C`_\|_imp_\|_symbol\*(C'\fR for \s-1DATA\s0 imports from DLLs.
1967 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1968 .Ip "\fB\*(--enable-runtime-pseudo-reloc\fR" 4
1969 .IX Item "enable-runtime-pseudo-reloc"
1970 If your code contains expressions described in \-\-enable-auto-import section,
1971 that is, \s-1DATA\s0 imports from \s-1DLL\s0 with non-zero offset, this switch will create
1972 a vector of 'runtime pseudo relocations' which can be used by runtime
1973 environment to adjust references to such data in your client code.
1974 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1975 .Ip "\fB\*(--disable-runtime-pseudo-reloc\fR" 4
1976 .IX Item "disable-runtime-pseudo-reloc"
1977 Do not create pseudo relocations for non-zero offset \s-1DATA\s0 imports from
1978 DLLs. This is the default.
1979 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1980 .Ip "\fB\*(--enable-extra-pe-debug\fR" 4
1981 .IX Item "enable-extra-pe-debug"
1982 Show additional debug info related to auto-import symbol thunking.
1983 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1984 .Ip "\fB\*(--section-alignment\fR" 4
1985 .IX Item "section-alignment"
1986 Sets the section alignment. Sections in memory will always begin at
1987 addresses which are a multiple of this number. Defaults to 0x1000.
1988 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1989 .Ip "\fB\*(--stack\fR \fIreserve\fR" 4
1990 .IX Item "stack reserve"
1992 .Ip "\fB\*(--stack\fR \fIreserve\fR\fB,\fR\fIcommit\fR" 4
1993 .IX Item "stack reserve,commit"
1995 Specify the amount of memory to reserve (and optionally commit) to be
1996 used as stack for this program. The default is 2Mb reserved, 4K
1998 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1999 .Ip "\fB\*(--subsystem\fR \fIwhich\fR" 4
2000 .IX Item "subsystem which"
2002 .Ip "\fB\*(--subsystem\fR \fIwhich\fR\fB:\fR\fImajor\fR" 4
2003 .IX Item "subsystem which:major"
2004 .Ip "\fB\*(--subsystem\fR \fIwhich\fR\fB:\fR\fImajor\fR\fB.\fR\fIminor\fR" 4
2005 .IX Item "subsystem which:major.minor"
2007 Specifies the subsystem under which your program will execute. The
2008 legal values for \fIwhich\fR are \f(CW\*(C`native\*(C'\fR, \f(CW\*(C`windows\*(C'\fR,
2009 \&\f(CW\*(C`console\*(C'\fR, \f(CW\*(C`posix\*(C'\fR, and \f(CW\*(C`xbox\*(C'\fR. You may optionally set
2010 the subsystem version also. Numeric values are also accepted for
2012 [This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2014 The 68HC11 and 68HC12 linkers support specific options to control the
2015 memory bank switching mapping and trampoline code generation.
2016 .Ip "\fB\*(--no-trampoline\fR" 4
2017 .IX Item "no-trampoline"
2018 This option disables the generation of trampoline. By default a trampoline
2019 is generated for each far function which is called using a \f(CW\*(C`jsr\*(C'\fR
2020 instruction (this happens when a pointer to a far function is taken).
2021 .Ip "\fB\*(--bank-window\fR \fIname\fR" 4
2022 .IX Item "bank-window name"
2023 This option indicates to the linker the name of the memory region in
2024 the \fB\s-1MEMORY\s0\fR specification that describes the memory bank window.
2025 The definition of such region is then used by the linker to compute
2026 paging and addresses within the memory window.
2028 .IX Header "ENVIRONMENT"
2029 You can change the behaviour of \fBld\fR with the environment variables
2030 \&\f(CW\*(C`GNUTARGET\*(C'\fR,
2031 \&\f(CW\*(C`LDEMULATION\*(C'\fR and \f(CW\*(C`COLLECT_NO_DEMANGLE\*(C'\fR.
2033 \&\f(CW\*(C`GNUTARGET\*(C'\fR determines the input-file object format if you don't
2034 use \fB\-b\fR (or its synonym \fB\*(--format\fR). Its value should be one
2035 of the \s-1BFD\s0 names for an input format. If there is no
2036 \&\f(CW\*(C`GNUTARGET\*(C'\fR in the environment, \fBld\fR uses the natural format
2037 of the target. If \f(CW\*(C`GNUTARGET\*(C'\fR is set to \f(CW\*(C`default\*(C'\fR then \s-1BFD\s0
2038 attempts to discover the input format by examining binary input files;
2039 this method often succeeds, but there are potential ambiguities, since
2040 there is no method of ensuring that the magic number used to specify
2041 object-file formats is unique. However, the configuration procedure for
2042 \&\s-1BFD\s0 on each system places the conventional format for that system first
2043 in the search-list, so ambiguities are resolved in favor of convention.
2045 \&\f(CW\*(C`LDEMULATION\*(C'\fR determines the default emulation if you don't use the
2046 \&\fB\-m\fR option. The emulation can affect various aspects of linker
2047 behaviour, particularly the default linker script. You can list the
2048 available emulations with the \fB\*(--verbose\fR or \fB\-V\fR options. If
2049 the \fB\-m\fR option is not used, and the \f(CW\*(C`LDEMULATION\*(C'\fR environment
2050 variable is not defined, the default emulation depends upon how the
2051 linker was configured.
2053 Normally, the linker will default to demangling symbols. However, if
2054 \&\f(CW\*(C`COLLECT_NO_DEMANGLE\*(C'\fR is set in the environment, then it will
2055 default to not demangling symbols. This environment variable is used in
2056 a similar fashion by the \f(CW\*(C`gcc\*(C'\fR linker wrapper program. The default
2057 may be overridden by the \fB\*(--demangle\fR and \fB\*(--no-demangle\fR
2060 .IX Header "SEE ALSO"
2061 \&\fIar\fR\|(1), \fInm\fR\|(1), \fIobjcopy\fR\|(1), \fIobjdump\fR\|(1), \fIreadelf\fR\|(1) and
2062 the Info entries for \fIbinutils\fR and
2065 .IX Header "COPYRIGHT"
2066 Copyright (c) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001,
2067 2002, 2003, 2004 Free Software Foundation, Inc.
2069 Permission is granted to copy, distribute and/or modify this document
2070 under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.1
2071 or any later version published by the Free Software Foundation;
2072 with no Invariant Sections, with no Front-Cover Texts, and with no
2073 Back-Cover Texts. A copy of the license is included in the
2074 section entitled \*(L"\s-1GNU\s0 Free Documentation License\*(R".