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.\" ========================================================================
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.\"
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.IX Title "LD 1"
135
.TH LD 1 "2009-10-16" "binutils-2.20" "GNU Development Tools"
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.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.\" way too many mistakes in technical documents.
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.if n .ad l
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.nh
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.SH "NAME"
141
ld \- The GNU linker
142
.SH "SYNOPSIS"
143
.IX Header "SYNOPSIS"
144
ld [\fBoptions\fR] \fIobjfile\fR ...
145
.SH "DESCRIPTION"
146
.IX Header "DESCRIPTION"
147
\&\fBld\fR combines a number of object and archive files, relocates
148
their data and ties up symbol references. Usually the last step in
149
compiling a program is to run \fBld\fR.
150
.PP
151
\&\fBld\fR accepts Linker Command Language files written in
152
a superset of \s-1AT&T\s0's Link Editor Command Language syntax,
153
to provide explicit and total control over the linking process.
154
.PP
155
This man page does not describe the command language; see the
156
\&\fBld\fR entry in \f(CW\*(C`info\*(C'\fR for full details on the command
157
language and on other aspects of the \s-1GNU\s0 linker.
158
.PP
159
This version of \fBld\fR uses the general purpose \s-1BFD\s0 libraries
160
to operate on object files. This allows \fBld\fR to read, combine, and
161
write object files in many different formats\-\-\-for example, \s-1COFF\s0 or
162
\&\f(CW\*(C`a.out\*(C'\fR.  Different formats may be linked together to produce any
163
available kind of object file.
164
.PP
165
Aside from its flexibility, the \s-1GNU\s0 linker is more helpful than other
166
linkers in providing diagnostic information.  Many linkers abandon
167
execution immediately upon encountering an error; whenever possible,
168
\&\fBld\fR continues executing, allowing you to identify other errors
169
(or, in some cases, to get an output file in spite of the error).
170
.PP
171
The \s-1GNU\s0 linker \fBld\fR is meant to cover a broad range of situations,
172
and to be as compatible as possible with other linkers.  As a result,
173
you have many choices to control its behavior.
174
.SH "OPTIONS"
175
.IX Header "OPTIONS"
176
The linker supports a plethora of command-line options, but in actual
177
practice few of them are used in any particular context.
178
For instance, a frequent use of \fBld\fR is to link standard Unix
179
object files on a standard, supported Unix system.  On such a system, to
180
link a file \f(CW\*(C`hello.o\*(C'\fR:
181
.PP
182
.Vb 1
183
\&        ld \-o  /lib/crt0.o hello.o \-lc
184
.Ve
185
.PP
186
This tells \fBld\fR to produce a file called \fIoutput\fR as the
187
result of linking the file \f(CW\*(C`/lib/crt0.o\*(C'\fR with \f(CW\*(C`hello.o\*(C'\fR and
188
the library \f(CW\*(C`libc.a\*(C'\fR, which will come from the standard search
189
directories.  (See the discussion of the \fB\-l\fR option below.)
190
.PP
191
Some of the command-line options to \fBld\fR may be specified at any
192
point in the command line.  However, options which refer to files, such
193
as \fB\-l\fR or \fB\-T\fR, cause the file to be read at the point at
194
which the option appears in the command line, relative to the object
195
files and other file options.  Repeating non-file options with a
196
different argument will either have no further effect, or override prior
197
occurrences (those further to the left on the command line) of that
198
option.  Options which may be meaningfully specified more than once are
199
noted in the descriptions below.
200
.PP
201
Non-option arguments are object files or archives which are to be linked
202
together.  They may follow, precede, or be mixed in with command-line
203
options, except that an object file argument may not be placed between
204
an option and its argument.
205
.PP
206
Usually the linker is invoked with at least one object file, but you can
207
specify other forms of binary input files using \fB\-l\fR, \fB\-R\fR,
208
and the script command language.  If \fIno\fR binary input files at all
209
are specified, the linker does not produce any output, and issues the
210
message \fBNo input files\fR.
211
.PP
212
If the linker cannot recognize the format of an object file, it will
213
assume that it is a linker script.  A script specified in this way
214
augments the main linker script used for the link (either the default
215
linker script or the one specified by using \fB\-T\fR).  This feature
216
permits the linker to link against a file which appears to be an object
217
or an archive, but actually merely defines some symbol values, or uses
218
\&\f(CW\*(C`INPUT\*(C'\fR or \f(CW\*(C`GROUP\*(C'\fR to load other objects.  Specifying a
219
script in this way merely augments the main linker script, with the
220
extra commands placed after the main script; use the \fB\-T\fR option
221
to replace the default linker script entirely, but note the effect of
222
the \f(CW\*(C`INSERT\*(C'\fR command.
223
.PP
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.
228
.PP
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 preceded 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
236
output.
237
.PP
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
243
accepted.
244
.PP
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:
249
.PP
250
.Vb 1
251
\&          gcc \-Wl,\-\-start\-group foo.o bar.o \-Wl,\-\-end\-group
252
.Ve
253
.PP
254
This is important, because otherwise the compiler driver program may
255
silently drop the linker options, resulting in a bad link.  Confusion
256
may also arise when passing options that require values through a
257
driver, as the use of a space between option and argument acts as
258
a separator, and causes the driver to pass only the option to the linker
259
and the argument to the compiler.  In this case, it is simplest to use
260
the joined forms of both single\- and multiple-letter options, such as:
261
.PP
262
.Vb 1
263
\&          gcc foo.o bar.o \-Wl,\-eENTRY \-Wl,\-Map=a.map
264
.Ve
265
.PP
266
Here is a table of the generic command line switches accepted by the \s-1GNU\s0
267
linker:
268
.IP "\fB@\fR\fIfile\fR" 4
269
.IX Item "@file"
270
Read command-line options from \fIfile\fR.  The options read are
271
inserted in place of the original @\fIfile\fR option.  If \fIfile\fR
272
does not exist, or cannot be read, then the option will be treated
273
literally, and not removed.
274
.Sp
275
Options in \fIfile\fR are separated by whitespace.  A whitespace
276
character may be included in an option by surrounding the entire
277
option in either single or double quotes.  Any character (including a
278
backslash) may be included by prefixing the character to be included
279
with a backslash.  The \fIfile\fR may itself contain additional
280
@\fIfile\fR options; any such options will be processed recursively.
281
.IP "\fB\-a\fR \fIkeyword\fR" 4
282
.IX Item "-a keyword"
283
This option is supported for \s-1HP/UX\s0 compatibility.  The \fIkeyword\fR
284
argument must be one of the strings \fBarchive\fR, \fBshared\fR, or
285
\&\fBdefault\fR.  \fB\-aarchive\fR is functionally equivalent to
286
\&\fB\-Bstatic\fR, and the other two keywords are functionally equivalent
287
to \fB\-Bdynamic\fR.  This option may be used any number of times.
288
.IP "\fB\-A\fR \fIarchitecture\fR" 4
289
.IX Item "-A architecture"
290
.PD 0
291
.IP "\fB\-\-architecture=\fR\fIarchitecture\fR" 4
292
.IX Item "--architecture=architecture"
293
.PD
294
In the current release of \fBld\fR, this option is useful only for the
295
Intel 960 family of architectures.  In that \fBld\fR configuration, the
296
\&\fIarchitecture\fR argument identifies the particular architecture in
297
the 960 family, enabling some safeguards and modifying the
298
archive-library search path.
299
.Sp
300
Future releases of \fBld\fR may support similar functionality for
301
other architecture families.
302
.IP "\fB\-b\fR \fIinput-format\fR" 4
303
.IX Item "-b input-format"
304
.PD 0
305
.IP "\fB\-\-format=\fR\fIinput-format\fR" 4
306
.IX Item "--format=input-format"
307
.PD
308
\&\fBld\fR may be configured to support more than one kind of object
309
file.  If your \fBld\fR is configured this way, you can use the
310
\&\fB\-b\fR option to specify the binary format for input object files
311
that follow this option on the command line.  Even when \fBld\fR is
312
configured to support alternative object formats, you don't usually need
313
to specify this, as \fBld\fR should be configured to expect as a
314
default input format the most usual format on each machine.
315
\&\fIinput-format\fR is a text string, the name of a particular format
316
supported by the \s-1BFD\s0 libraries.  (You can list the available binary
317
formats with \fBobjdump \-i\fR.)
318
.Sp
319
You may want to use this option if you are linking files with an unusual
320
binary format.  You can also use \fB\-b\fR to switch formats explicitly (when
321
linking object files of different formats), by including
322
\&\fB\-b\fR \fIinput-format\fR before each group of object files in a
323
particular format.
324
.Sp
325
The default format is taken from the environment variable
326
\&\f(CW\*(C`GNUTARGET\*(C'\fR.
327
.Sp
328
You can also define the input format from a script, using the command
329
\&\f(CW\*(C`TARGET\*(C'\fR;
330
.IP "\fB\-c\fR \fIMRI-commandfile\fR" 4
331
.IX Item "-c MRI-commandfile"
332
.PD 0
333
.IP "\fB\-\-mri\-script=\fR\fIMRI-commandfile\fR" 4
334
.IX Item "--mri-script=MRI-commandfile"
335
.PD
336
For compatibility with linkers produced by \s-1MRI\s0, \fBld\fR accepts script
337
files written in an alternate, restricted command language, described in
338
the \s-1MRI\s0 Compatible Script Files section of \s-1GNU\s0 ld documentation.
339
Introduce \s-1MRI\s0 script files with
340
the option \fB\-c\fR; use the \fB\-T\fR option to run linker
341
scripts written in the general-purpose \fBld\fR scripting language.
342
If \fIMRI-cmdfile\fR does not exist, \fBld\fR looks for it in the directories
343
specified by any \fB\-L\fR options.
344
.IP "\fB\-d\fR" 4
345
.IX Item "-d"
346
.PD 0
347
.IP "\fB\-dc\fR" 4
348
.IX Item "-dc"
349
.IP "\fB\-dp\fR" 4
350
.IX Item "-dp"
351
.PD
352
These three options are equivalent; multiple forms are supported for
353
compatibility with other linkers.  They assign space to common symbols
354
even if a relocatable output file is specified (with \fB\-r\fR).  The
355
script command \f(CW\*(C`FORCE_COMMON_ALLOCATION\*(C'\fR has the same effect.
356
.IP "\fB\-e\fR \fIentry\fR" 4
357
.IX Item "-e entry"
358
.PD 0
359
.IP "\fB\-\-entry=\fR\fIentry\fR" 4
360
.IX Item "--entry=entry"
361
.PD
362
Use \fIentry\fR as the explicit symbol for beginning execution of your
363
program, rather than the default entry point.  If there is no symbol
364
named \fIentry\fR, the linker will try to parse \fIentry\fR as a number,
365
and use that as the entry address (the number will be interpreted in
366
base 10; you may use a leading \fB0x\fR for base 16, or a leading
367
\&\fB0\fR for base 8).
368
.IP "\fB\-\-exclude\-libs\fR \fIlib\fR\fB,\fR\fIlib\fR\fB,...\fR" 4
369
.IX Item "--exclude-libs lib,lib,..."
370
Specifies a list of archive libraries from which symbols should not be automatically
371
exported.  The library names may be delimited by commas or colons.  Specifying
372
\&\f(CW\*(C`\-\-exclude\-libs ALL\*(C'\fR excludes symbols in all archive libraries from
373
automatic export.  This option is available only for the i386 \s-1PE\s0 targeted
374
port of the linker and for \s-1ELF\s0 targeted ports.  For i386 \s-1PE\s0, symbols
375
explicitly listed in a .def file are still exported, regardless of this
376
option.  For \s-1ELF\s0 targeted ports, symbols affected by this option will
377
be treated as hidden.
378
.IP "\fB\-\-exclude\-modules\-for\-implib\fR \fImodule\fR\fB,\fR\fImodule\fR\fB,...\fR" 4
379
.IX Item "--exclude-modules-for-implib module,module,..."
380
Specifies a list of object files or archive members, from which symbols
381
should not be automatically exported, but which should be copied wholesale
382
into the import library being generated during the link.  The module names
383
may be delimited by commas or colons, and must match exactly the filenames
384
used by \fBld\fR to open the files; for archive members, this is simply
385
the member name, but for object files the name listed must include and
386
match precisely any path used to specify the input file on the linker's
387
command-line.  This option is available only for the i386 \s-1PE\s0 targeted port
388
of the linker.  Symbols explicitly listed in a .def file are still exported,
389
regardless of this option.
390
.IP "\fB\-E\fR" 4
391
.IX Item "-E"
392
.PD 0
393
.IP "\fB\-\-export\-dynamic\fR" 4
394
.IX Item "--export-dynamic"
395
.IP "\fB\-\-no\-export\-dynamic\fR" 4
396
.IX Item "--no-export-dynamic"
397
.PD
398
When creating a dynamically linked executable, using the \fB\-E\fR
399
option or the \fB\-\-export\-dynamic\fR option causes the linker to add
400
all symbols to the dynamic symbol table.  The dynamic symbol table is the
401
set of symbols which are visible from dynamic objects at run time.
402
.Sp
403
If you do not use either of these options (or use the
404
\&\fB\-\-no\-export\-dynamic\fR option to restore the default behavior), the
405
dynamic symbol table will normally contain only those symbols which are
406
referenced by some dynamic object mentioned in the link.
407
.Sp
408
If you use \f(CW\*(C`dlopen\*(C'\fR to load a dynamic object which needs to refer
409
back to the symbols defined by the program, rather than some other
410
dynamic object, then you will probably need to use this option when
411
linking the program itself.
412
.Sp
413
You can also use the dynamic list to control what symbols should
414
be added to the dynamic symbol table if the output format supports it.
415
See the description of \fB\-\-dynamic\-list\fR.
416
.Sp
417
Note that this option is specific to \s-1ELF\s0 targeted ports.  \s-1PE\s0 targets
418
support a similar function to export all symbols from a \s-1DLL\s0 or \s-1EXE\s0; see
419
the description of \fB\-\-export\-all\-symbols\fR below.
420
.IP "\fB\-EB\fR" 4
421
.IX Item "-EB"
422
Link big-endian objects.  This affects the default output format.
423
.IP "\fB\-EL\fR" 4
424
.IX Item "-EL"
425
Link little-endian objects.  This affects the default output format.
426
.IP "\fB\-f\fR \fIname\fR" 4
427
.IX Item "-f name"
428
.PD 0
429
.IP "\fB\-\-auxiliary=\fR\fIname\fR" 4
430
.IX Item "--auxiliary=name"
431
.PD
432
When creating an \s-1ELF\s0 shared object, set the internal \s-1DT_AUXILIARY\s0 field
433
to the specified name.  This tells the dynamic linker that the symbol
434
table of the shared object should be used as an auxiliary filter on the
435
symbol table of the shared object \fIname\fR.
436
.Sp
437
If you later link a program against this filter object, then, when you
438
run the program, the dynamic linker will see the \s-1DT_AUXILIARY\s0 field.  If
439
the dynamic linker resolves any symbols from the filter object, it will
440
first check whether there is a definition in the shared object
441
\&\fIname\fR.  If there is one, it will be used instead of the definition
442
in the filter object.  The shared object \fIname\fR need not exist.
443
Thus the shared object \fIname\fR may be used to provide an alternative
444
implementation of certain functions, perhaps for debugging or for
445
machine specific performance.
446
.Sp
447
This option may be specified more than once.  The \s-1DT_AUXILIARY\s0 entries
448
will be created in the order in which they appear on the command line.
449
.IP "\fB\-F\fR \fIname\fR" 4
450
.IX Item "-F name"
451
.PD 0
452
.IP "\fB\-\-filter=\fR\fIname\fR" 4
453
.IX Item "--filter=name"
454
.PD
455
When creating an \s-1ELF\s0 shared object, set the internal \s-1DT_FILTER\s0 field to
456
the specified name.  This tells the dynamic linker that the symbol table
457
of the shared object which is being created should be used as a filter
458
on the symbol table of the shared object \fIname\fR.
459
.Sp
460
If you later link a program against this filter object, then, when you
461
run the program, the dynamic linker will see the \s-1DT_FILTER\s0 field.  The
462
dynamic linker will resolve symbols according to the symbol table of the
463
filter object as usual, but it will actually link to the definitions
464
found in the shared object \fIname\fR.  Thus the filter object can be
465
used to select a subset of the symbols provided by the object
466
\&\fIname\fR.
467
.Sp
468
Some older linkers used the \fB\-F\fR option throughout a compilation
469
toolchain for specifying object-file format for both input and output
470
object files.
471
The \s-1GNU\s0 linker uses other mechanisms for this purpose: the
472
\&\fB\-b\fR, \fB\-\-format\fR, \fB\-\-oformat\fR options, the
473
\&\f(CW\*(C`TARGET\*(C'\fR command in linker scripts, and the \f(CW\*(C`GNUTARGET\*(C'\fR
474
environment variable.
475
The \s-1GNU\s0 linker will ignore the \fB\-F\fR option when not
476
creating an \s-1ELF\s0 shared object.
477
.IP "\fB\-fini=\fR\fIname\fR" 4
478
.IX Item "-fini=name"
479
When creating an \s-1ELF\s0 executable or shared object, call \s-1NAME\s0 when the
480
executable or shared object is unloaded, by setting \s-1DT_FINI\s0 to the
481
address of the function.  By default, the linker uses \f(CW\*(C`_fini\*(C'\fR as
482
the function to call.
483
.IP "\fB\-g\fR" 4
484
.IX Item "-g"
485
Ignored.  Provided for compatibility with other tools.
486
.IP "\fB\-G\fR \fIvalue\fR" 4
487
.IX Item "-G value"
488
.PD 0
489
.IP "\fB\-\-gpsize=\fR\fIvalue\fR" 4
490
.IX Item "--gpsize=value"
491
.PD
492
Set the maximum size of objects to be optimized using the \s-1GP\s0 register to
493
\&\fIsize\fR.  This is only meaningful for object file formats such as
494
\&\s-1MIPS\s0 \s-1ECOFF\s0 which supports putting large and small objects into different
495
sections.  This is ignored for other object file formats.
496
.IP "\fB\-h\fR \fIname\fR" 4
497
.IX Item "-h name"
498
.PD 0
499
.IP "\fB\-soname=\fR\fIname\fR" 4
500
.IX Item "-soname=name"
501
.PD
502
When creating an \s-1ELF\s0 shared object, set the internal \s-1DT_SONAME\s0 field to
503
the specified name.  When an executable is linked with a shared object
504
which has a \s-1DT_SONAME\s0 field, then when the executable is run the dynamic
505
linker will attempt to load the shared object specified by the \s-1DT_SONAME\s0
506
field rather than the using the file name given to the linker.
507
.IP "\fB\-i\fR" 4
508
.IX Item "-i"
509
Perform an incremental link (same as option \fB\-r\fR).
510
.IP "\fB\-init=\fR\fIname\fR" 4
511
.IX Item "-init=name"
512
When creating an \s-1ELF\s0 executable or shared object, call \s-1NAME\s0 when the
513
executable or shared object is loaded, by setting \s-1DT_INIT\s0 to the address
514
of the function.  By default, the linker uses \f(CW\*(C`_init\*(C'\fR as the
515
function to call.
516
.IP "\fB\-l\fR \fInamespec\fR" 4
517
.IX Item "-l namespec"
518
.PD 0
519
.IP "\fB\-\-library=\fR\fInamespec\fR" 4
520
.IX Item "--library=namespec"
521
.PD
522
Add the archive or object file specified by \fInamespec\fR to the
523
list of files to link.  This option may be used any number of times.
524
If \fInamespec\fR is of the form \fI:\fIfilename\fI\fR, \fBld\fR
525
will search the library path for a file called \fIfilename\fR, otherwise it
526
will search the library path for a file called \fIlib\fInamespec\fI.a\fR.
527
.Sp
528
On systems which support shared libraries, \fBld\fR may also search for
529
files other than \fIlib\fInamespec\fI.a\fR.  Specifically, on \s-1ELF\s0
530
and SunOS systems, \fBld\fR will search a directory for a library
531
called \fIlib\fInamespec\fI.so\fR before searching for one called
532
\&\fIlib\fInamespec\fI.a\fR.  (By convention, a \f(CW\*(C`.so\*(C'\fR extension
533
indicates a shared library.)  Note that this behavior does not apply
534
to \fI:\fIfilename\fI\fR, which always specifies a file called
535
\&\fIfilename\fR.
536
.Sp
537
The linker will search an archive only once, at the location where it is
538
specified on the command line.  If the archive defines a symbol which
539
was undefined in some object which appeared before the archive on the
540
command line, the linker will include the appropriate file(s) from the
541
archive.  However, an undefined symbol in an object appearing later on
542
the command line will not cause the linker to search the archive again.
543
.Sp
544
See the \fB\-(\fR option for a way to force the linker to search
545
archives multiple times.
546
.Sp
547
You may list the same archive multiple times on the command line.
548
.Sp
549
This type of archive searching is standard for Unix linkers.  However,
550
if you are using \fBld\fR on \s-1AIX\s0, note that it is different from the
551
behaviour of the \s-1AIX\s0 linker.
552
.IP "\fB\-L\fR \fIsearchdir\fR" 4
553
.IX Item "-L searchdir"
554
.PD 0
555
.IP "\fB\-\-library\-path=\fR\fIsearchdir\fR" 4
556
.IX Item "--library-path=searchdir"
557
.PD
558
Add path \fIsearchdir\fR to the list of paths that \fBld\fR will search
559
for archive libraries and \fBld\fR control scripts.  You may use this
560
option any number of times.  The directories are searched in the order
561
in which they are specified on the command line.  Directories specified
562
on the command line are searched before the default directories.  All
563
\&\fB\-L\fR options apply to all \fB\-l\fR options, regardless of the
564
order in which the options appear.  \fB\-L\fR options do not affect
565
how \fBld\fR searches for a linker script unless \fB\-T\fR
566
option is specified.
567
.Sp
568
If \fIsearchdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
569
by the \fIsysroot prefix\fR, a path specified when the linker is configured.
570
.Sp
571
The default set of paths searched (without being specified with
572
\&\fB\-L\fR) depends on which emulation mode \fBld\fR is using, and in
573
some cases also on how it was configured.
574
.Sp
575
The paths can also be specified in a link script with the
576
\&\f(CW\*(C`SEARCH_DIR\*(C'\fR command.  Directories specified this way are searched
577
at the point in which the linker script appears in the command line.
578
.IP "\fB\-m\fR \fIemulation\fR" 4
579
.IX Item "-m emulation"
580
Emulate the \fIemulation\fR linker.  You can list the available
581
emulations with the \fB\-\-verbose\fR or \fB\-V\fR options.
582
.Sp
583
If the \fB\-m\fR option is not used, the emulation is taken from the
584
\&\f(CW\*(C`LDEMULATION\*(C'\fR environment variable, if that is defined.
585
.Sp
586
Otherwise, the default emulation depends upon how the linker was
587
configured.
588
.IP "\fB\-M\fR" 4
589
.IX Item "-M"
590
.PD 0
591
.IP "\fB\-\-print\-map\fR" 4
592
.IX Item "--print-map"
593
.PD
594
Print a link map to the standard output.  A link map provides
595
information about the link, including the following:
596
.RS 4
597
.IP "\(bu" 4
598
Where object files are mapped into memory.
599
.IP "\(bu" 4
600
How common symbols are allocated.
601
.IP "\(bu" 4
602
All archive members included in the link, with a mention of the symbol
603
which caused the archive member to be brought in.
604
.IP "\(bu" 4
605
The values assigned to symbols.
606
.Sp
607
Note \- symbols whose values are computed by an expression which
608
involves a reference to a previous value of the same symbol may not
609
have correct result displayed in the link map.  This is because the
610
linker discards intermediate results and only retains the final value
611
of an expression.  Under such circumstances the linker will display
612
the final value enclosed by square brackets.  Thus for example a
613
linker script containing:
614
.Sp
615
.Vb 3
616
\&           foo = 1
617
\&           foo = foo * 4
618
\&           foo = foo + 8
619
.Ve
620
.Sp
621
will produce the following output in the link map if the \fB\-M\fR
622
option is used:
623
.Sp
624
.Vb 3
625
\&           0x00000001                foo = 0x1
626
\&           [0x0000000c]                foo = (foo * 0x4)
627
\&           [0x0000000c]                foo = (foo + 0x8)
628
.Ve
629
.Sp
630
See \fBExpressions\fR for more information about expressions in linker
631
scripts.
632
.RE
633
.RS 4
634
.RE
635
.IP "\fB\-n\fR" 4
636
.IX Item "-n"
637
.PD 0
638
.IP "\fB\-\-nmagic\fR" 4
639
.IX Item "--nmagic"
640
.PD
641
Turn off page alignment of sections, and mark the output as
642
\&\f(CW\*(C`NMAGIC\*(C'\fR if possible.
643
.IP "\fB\-N\fR" 4
644
.IX Item "-N"
645
.PD 0
646
.IP "\fB\-\-omagic\fR" 4
647
.IX Item "--omagic"
648
.PD
649
Set the text and data sections to be readable and writable.  Also, do
650
not page-align the data segment, and disable linking against shared
651
libraries.  If the output format supports Unix style magic numbers,
652
mark the output as \f(CW\*(C`OMAGIC\*(C'\fR. Note: Although a writable text section
653
is allowed for PE-COFF targets, it does not conform to the format
654
specification published by Microsoft.
655
.IP "\fB\-\-no\-omagic\fR" 4
656
.IX Item "--no-omagic"
657
This option negates most of the effects of the \fB\-N\fR option.  It
658
sets the text section to be read-only, and forces the data segment to
659
be page-aligned.  Note \- this option does not enable linking against
660
shared libraries.  Use \fB\-Bdynamic\fR for this.
661
.IP "\fB\-o\fR \fIoutput\fR" 4
662
.IX Item "-o output"
663
.PD 0
664
.IP "\fB\-\-output=\fR\fIoutput\fR" 4
665
.IX Item "--output=output"
666
.PD
667
Use \fIoutput\fR as the name for the program produced by \fBld\fR; if this
668
option is not specified, the name \fIa.out\fR is used by default.  The
669
script command \f(CW\*(C`OUTPUT\*(C'\fR can also specify the output file name.
670
.IP "\fB\-O\fR \fIlevel\fR" 4
671
.IX Item "-O level"
672
If \fIlevel\fR is a numeric values greater than zero \fBld\fR optimizes
673
the output.  This might take significantly longer and therefore probably
674
should only be enabled for the final binary.  At the moment this
675
option only affects \s-1ELF\s0 shared library generation.  Future releases of
676
the linker may make more use of this option.  Also currently there is
677
no difference in the linker's behaviour for different non-zero values
678
of this option.  Again this may change with future releases.
679
.IP "\fB\-q\fR" 4
680
.IX Item "-q"
681
.PD 0
682
.IP "\fB\-\-emit\-relocs\fR" 4
683
.IX Item "--emit-relocs"
684
.PD
685
Leave relocation sections and contents in fully linked executables.
686
Post link analysis and optimization tools may need this information in
687
order to perform correct modifications of executables.  This results
688
in larger executables.
689
.Sp
690
This option is currently only supported on \s-1ELF\s0 platforms.
691
.IP "\fB\-\-force\-dynamic\fR" 4
692
.IX Item "--force-dynamic"
693
Force the output file to have dynamic sections.  This option is specific
694
to VxWorks targets.
695
.IP "\fB\-r\fR" 4
696
.IX Item "-r"
697
.PD 0
698
.IP "\fB\-\-relocatable\fR" 4
699
.IX Item "--relocatable"
700
.PD
701
Generate relocatable output\-\-\-i.e., generate an output file that can in
702
turn serve as input to \fBld\fR.  This is often called \fIpartial
703
linking\fR.  As a side effect, in environments that support standard Unix
704
magic numbers, this option also sets the output file's magic number to
705
\&\f(CW\*(C`OMAGIC\*(C'\fR.
706
If this option is not specified, an absolute file is produced.  When
707
linking \*(C+ programs, this option \fIwill not\fR resolve references to
708
constructors; to do that, use \fB\-Ur\fR.
709
.Sp
710
When an input file does not have the same format as the output file,
711
partial linking is only supported if that input file does not contain any
712
relocations.  Different output formats can have further restrictions; for
713
example some \f(CW\*(C`a.out\*(C'\fR\-based formats do not support partial linking
714
with input files in other formats at all.
715
.Sp
716
This option does the same thing as \fB\-i\fR.
717
.IP "\fB\-R\fR \fIfilename\fR" 4
718
.IX Item "-R filename"
719
.PD 0
720
.IP "\fB\-\-just\-symbols=\fR\fIfilename\fR" 4
721
.IX Item "--just-symbols=filename"
722
.PD
723
Read symbol names and their addresses from \fIfilename\fR, but do not
724
relocate it or include it in the output.  This allows your output file
725
to refer symbolically to absolute locations of memory defined in other
726
programs.  You may use this option more than once.
727
.Sp
728
For compatibility with other \s-1ELF\s0 linkers, if the \fB\-R\fR option is
729
followed by a directory name, rather than a file name, it is treated as
730
the \fB\-rpath\fR option.
731
.IP "\fB\-s\fR" 4
732
.IX Item "-s"
733
.PD 0
734
.IP "\fB\-\-strip\-all\fR" 4
735
.IX Item "--strip-all"
736
.PD
737
Omit all symbol information from the output file.
738
.IP "\fB\-S\fR" 4
739
.IX Item "-S"
740
.PD 0
741
.IP "\fB\-\-strip\-debug\fR" 4
742
.IX Item "--strip-debug"
743
.PD
744
Omit debugger symbol information (but not all symbols) from the output file.
745
.IP "\fB\-t\fR" 4
746
.IX Item "-t"
747
.PD 0
748
.IP "\fB\-\-trace\fR" 4
749
.IX Item "--trace"
750
.PD
751
Print the names of the input files as \fBld\fR processes them.
752
.IP "\fB\-T\fR \fIscriptfile\fR" 4
753
.IX Item "-T scriptfile"
754
.PD 0
755
.IP "\fB\-\-script=\fR\fIscriptfile\fR" 4
756
.IX Item "--script=scriptfile"
757
.PD
758
Use \fIscriptfile\fR as the linker script.  This script replaces
759
\&\fBld\fR's default linker script (rather than adding to it), so
760
\&\fIcommandfile\fR must specify everything necessary to describe the
761
output file.    If \fIscriptfile\fR does not exist in
762
the current directory, \f(CW\*(C`ld\*(C'\fR looks for it in the directories
763
specified by any preceding \fB\-L\fR options.  Multiple \fB\-T\fR
764
options accumulate.
765
.IP "\fB\-dT\fR \fIscriptfile\fR" 4
766
.IX Item "-dT scriptfile"
767
.PD 0
768
.IP "\fB\-\-default\-script=\fR\fIscriptfile\fR" 4
769
.IX Item "--default-script=scriptfile"
770
.PD
771
Use \fIscriptfile\fR as the default linker script.
772
.Sp
773
This option is similar to the \fB\-\-script\fR option except that
774
processing of the script is delayed until after the rest of the
775
command line has been processed.  This allows options placed after the
776
\&\fB\-\-default\-script\fR option on the command line to affect the
777
behaviour of the linker script, which can be important when the linker
778
command line cannot be directly controlled by the user.  (eg because
779
the command line is being constructed by another tool, such as
780
\&\fBgcc\fR).
781
.IP "\fB\-u\fR \fIsymbol\fR" 4
782
.IX Item "-u symbol"
783
.PD 0
784
.IP "\fB\-\-undefined=\fR\fIsymbol\fR" 4
785
.IX Item "--undefined=symbol"
786
.PD
787
Force \fIsymbol\fR to be entered in the output file as an undefined
788
symbol.  Doing this may, for example, trigger linking of additional
789
modules from standard libraries.  \fB\-u\fR may be repeated with
790
different option arguments to enter additional undefined symbols.  This
791
option is equivalent to the \f(CW\*(C`EXTERN\*(C'\fR linker script command.
792
.IP "\fB\-Ur\fR" 4
793
.IX Item "-Ur"
794
For anything other than \*(C+ programs, this option is equivalent to
795
\&\fB\-r\fR: it generates relocatable output\-\-\-i.e., an output file that can in
796
turn serve as input to \fBld\fR.  When linking \*(C+ programs, \fB\-Ur\fR
797
\&\fIdoes\fR resolve references to constructors, unlike \fB\-r\fR.
798
It does not work to use \fB\-Ur\fR on files that were themselves linked
799
with \fB\-Ur\fR; once the constructor table has been built, it cannot
800
be added to.  Use \fB\-Ur\fR only for the last partial link, and
801
\&\fB\-r\fR for the others.
802
.IP "\fB\-\-unique[=\fR\fI\s-1SECTION\s0\fR\fB]\fR" 4
803
.IX Item "--unique[=SECTION]"
804
Creates a separate output section for every input section matching
805
\&\fI\s-1SECTION\s0\fR, or if the optional wildcard \fI\s-1SECTION\s0\fR argument is
806
missing, for every orphan input section.  An orphan section is one not
807
specifically mentioned in a linker script.  You may use this option
808
multiple times on the command line;  It prevents the normal merging of
809
input sections with the same name, overriding output section assignments
810
in a linker script.
811
.IP "\fB\-v\fR" 4
812
.IX Item "-v"
813
.PD 0
814
.IP "\fB\-\-version\fR" 4
815
.IX Item "--version"
816
.IP "\fB\-V\fR" 4
817
.IX Item "-V"
818
.PD
819
Display the version number for \fBld\fR.  The \fB\-V\fR option also
820
lists the supported emulations.
821
.IP "\fB\-x\fR" 4
822
.IX Item "-x"
823
.PD 0
824
.IP "\fB\-\-discard\-all\fR" 4
825
.IX Item "--discard-all"
826
.PD
827
Delete all local symbols.
828
.IP "\fB\-X\fR" 4
829
.IX Item "-X"
830
.PD 0
831
.IP "\fB\-\-discard\-locals\fR" 4
832
.IX Item "--discard-locals"
833
.PD
834
Delete all temporary local symbols.  (These symbols start with
835
system-specific local label prefixes, typically \fB.L\fR for \s-1ELF\s0 systems
836
or \fBL\fR for traditional a.out systems.)
837
.IP "\fB\-y\fR \fIsymbol\fR" 4
838
.IX Item "-y symbol"
839
.PD 0
840
.IP "\fB\-\-trace\-symbol=\fR\fIsymbol\fR" 4
841
.IX Item "--trace-symbol=symbol"
842
.PD
843
Print the name of each linked file in which \fIsymbol\fR appears.  This
844
option may be given any number of times.  On many systems it is necessary
845
to prepend an underscore.
846
.Sp
847
This option is useful when you have an undefined symbol in your link but
848
don't know where the reference is coming from.
849
.IP "\fB\-Y\fR \fIpath\fR" 4
850
.IX Item "-Y path"
851
Add \fIpath\fR to the default library search path.  This option exists
852
for Solaris compatibility.
853
.IP "\fB\-z\fR \fIkeyword\fR" 4
854
.IX Item "-z keyword"
855
The recognized keywords are:
856
.RS 4
857
.IP "\fBcombreloc\fR" 4
858
.IX Item "combreloc"
859
Combines multiple reloc sections and sorts them to make dynamic symbol
860
lookup caching possible.
861
.IP "\fBdefs\fR" 4
862
.IX Item "defs"
863
Disallows undefined symbols in object files.  Undefined symbols in
864
shared libraries are still allowed.
865
.IP "\fBexecstack\fR" 4
866
.IX Item "execstack"
867
Marks the object as requiring executable stack.
868
.IP "\fBinitfirst\fR" 4
869
.IX Item "initfirst"
870
This option is only meaningful when building a shared object.
871
It marks the object so that its runtime initialization will occur
872
before the runtime initialization of any other objects brought into
873
the process at the same time.  Similarly the runtime finalization of
874
the object will occur after the runtime finalization of any other
875
objects.
876
.IP "\fBinterpose\fR" 4
877
.IX Item "interpose"
878
Marks the object that its symbol table interposes before all symbols
879
but the primary executable.
880
.IP "\fBlazy\fR" 4
881
.IX Item "lazy"
882
When generating an executable or shared library, mark it to tell the
883
dynamic linker to defer function call resolution to the point when
884
the function is called (lazy binding), rather than at load time.
885
Lazy binding is the default.
886
.IP "\fBloadfltr\fR" 4
887
.IX Item "loadfltr"
888
Marks  the object that its filters be processed immediately at
889
runtime.
890
.IP "\fBmuldefs\fR" 4
891
.IX Item "muldefs"
892
Allows multiple definitions.
893
.IP "\fBnocombreloc\fR" 4
894
.IX Item "nocombreloc"
895
Disables multiple reloc sections combining.
896
.IP "\fBnocopyreloc\fR" 4
897
.IX Item "nocopyreloc"
898
Disables production of copy relocs.
899
.IP "\fBnodefaultlib\fR" 4
900
.IX Item "nodefaultlib"
901
Marks the object that the search for dependencies of this object will
902
ignore any default library search paths.
903
.IP "\fBnodelete\fR" 4
904
.IX Item "nodelete"
905
Marks the object shouldn't be unloaded at runtime.
906
.IP "\fBnodlopen\fR" 4
907
.IX Item "nodlopen"
908
Marks the object not available to \f(CW\*(C`dlopen\*(C'\fR.
909
.IP "\fBnodump\fR" 4
910
.IX Item "nodump"
911
Marks the object can not be dumped by \f(CW\*(C`dldump\*(C'\fR.
912
.IP "\fBnoexecstack\fR" 4
913
.IX Item "noexecstack"
914
Marks the object as not requiring executable stack.
915
.IP "\fBnorelro\fR" 4
916
.IX Item "norelro"
917
Don't create an \s-1ELF\s0 \f(CW\*(C`PT_GNU_RELRO\*(C'\fR segment header in the object.
918
.IP "\fBnow\fR" 4
919
.IX Item "now"
920
When generating an executable or shared library, mark it to tell the
921
dynamic linker to resolve all symbols when the program is started, or
922
when the shared library is linked to using dlopen, instead of
923
deferring function call resolution to the point when the function is
924
first called.
925
.IP "\fBorigin\fR" 4
926
.IX Item "origin"
927
Marks the object may contain \f(CW$ORIGIN\fR.
928
.IP "\fBrelro\fR" 4
929
.IX Item "relro"
930
Create an \s-1ELF\s0 \f(CW\*(C`PT_GNU_RELRO\*(C'\fR segment header in the object.
931
.IP "\fBmax\-page\-size=\fR\fIvalue\fR" 4
932
.IX Item "max-page-size=value"
933
Set the emulation maximum page size to \fIvalue\fR.
934
.IP "\fBcommon\-page\-size=\fR\fIvalue\fR" 4
935
.IX Item "common-page-size=value"
936
Set the emulation common page size to \fIvalue\fR.
937
.RE
938
.RS 4
939
.Sp
940
Other keywords are ignored for Solaris compatibility.
941
.RE
942
.IP "\fB\-(\fR \fIarchives\fR \fB\-)\fR" 4
943
.IX Item "-( archives -)"
944
.PD 0
945
.IP "\fB\-\-start\-group\fR \fIarchives\fR \fB\-\-end\-group\fR" 4
946
.IX Item "--start-group archives --end-group"
947
.PD
948
The \fIarchives\fR should be a list of archive files.  They may be
949
either explicit file names, or \fB\-l\fR options.
950
.Sp
951
The specified archives are searched repeatedly until no new undefined
952
references are created.  Normally, an archive is searched only once in
953
the order that it is specified on the command line.  If a symbol in that
954
archive is needed to resolve an undefined symbol referred to by an
955
object in an archive that appears later on the command line, the linker
956
would not be able to resolve that reference.  By grouping the archives,
957
they all be searched repeatedly until all possible references are
958
resolved.
959
.Sp
960
Using this option has a significant performance cost.  It is best to use
961
it only when there are unavoidable circular references between two or
962
more archives.
963
.IP "\fB\-\-accept\-unknown\-input\-arch\fR" 4
964
.IX Item "--accept-unknown-input-arch"
965
.PD 0
966
.IP "\fB\-\-no\-accept\-unknown\-input\-arch\fR" 4
967
.IX Item "--no-accept-unknown-input-arch"
968
.PD
969
Tells the linker to accept input files whose architecture cannot be
970
recognised.  The assumption is that the user knows what they are doing
971
and deliberately wants to link in these unknown input files.  This was
972
the default behaviour of the linker, before release 2.14.  The default
973
behaviour from release 2.14 onwards is to reject such input files, and
974
so the \fB\-\-accept\-unknown\-input\-arch\fR option has been added to
975
restore the old behaviour.
976
.IP "\fB\-\-as\-needed\fR" 4
977
.IX Item "--as-needed"
978
.PD 0
979
.IP "\fB\-\-no\-as\-needed\fR" 4
980
.IX Item "--no-as-needed"
981
.PD
982
This option affects \s-1ELF\s0 \s-1DT_NEEDED\s0 tags for dynamic libraries mentioned
983
on the command line after the \fB\-\-as\-needed\fR option.  Normally,
984
the linker will add a \s-1DT_NEEDED\s0 tag for each dynamic library mentioned
985
on the command line, regardless of whether the library is actually
986
needed.  \fB\-\-as\-needed\fR causes a \s-1DT_NEEDED\s0 tag to only be emitted
987
for a library that satisfies a symbol reference from regular objects
988
which is undefined at the point that the library was linked, or, if
989
the library is not found in the \s-1DT_NEEDED\s0 lists of other libraries
990
linked up to that point, a reference from another dynamic library.
991
\&\fB\-\-no\-as\-needed\fR restores the default behaviour.
992
.IP "\fB\-\-add\-needed\fR" 4
993
.IX Item "--add-needed"
994
.PD 0
995
.IP "\fB\-\-no\-add\-needed\fR" 4
996
.IX Item "--no-add-needed"
997
.PD
998
This option affects the treatment of dynamic libraries from \s-1ELF\s0
999
\&\s-1DT_NEEDED\s0 tags in dynamic libraries mentioned on the command line after
1000
the \fB\-\-no\-add\-needed\fR option.  Normally, the linker will add
1001
a \s-1DT_NEEDED\s0 tag for each dynamic library from \s-1DT_NEEDED\s0 tags.
1002
\&\fB\-\-no\-add\-needed\fR causes \s-1DT_NEEDED\s0 tags will never be emitted
1003
for those libraries from \s-1DT_NEEDED\s0 tags. \fB\-\-add\-needed\fR restores
1004
the default behaviour.
1005
.IP "\fB\-assert\fR \fIkeyword\fR" 4
1006
.IX Item "-assert keyword"
1007
This option is ignored for SunOS compatibility.
1008
.IP "\fB\-Bdynamic\fR" 4
1009
.IX Item "-Bdynamic"
1010
.PD 0
1011
.IP "\fB\-dy\fR" 4
1012
.IX Item "-dy"
1013
.IP "\fB\-call_shared\fR" 4
1014
.IX Item "-call_shared"
1015
.PD
1016
Link against dynamic libraries.  This is only meaningful on platforms
1017
for which shared libraries are supported.  This option is normally the
1018
default on such platforms.  The different variants of this option are
1019
for compatibility with various systems.  You may use this option
1020
multiple times on the command line: it affects library searching for
1021
\&\fB\-l\fR options which follow it.
1022
.IP "\fB\-Bgroup\fR" 4
1023
.IX Item "-Bgroup"
1024
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
1025
section.  This causes the runtime linker to handle lookups in this
1026
object and its dependencies to be performed only inside the group.
1027
\&\fB\-\-unresolved\-symbols=report\-all\fR is implied.  This option is
1028
only meaningful on \s-1ELF\s0 platforms which support shared libraries.
1029
.IP "\fB\-Bstatic\fR" 4
1030
.IX Item "-Bstatic"
1031
.PD 0
1032
.IP "\fB\-dn\fR" 4
1033
.IX Item "-dn"
1034
.IP "\fB\-non_shared\fR" 4
1035
.IX Item "-non_shared"
1036
.IP "\fB\-static\fR" 4
1037
.IX Item "-static"
1038
.PD
1039
Do not link against shared libraries.  This is only meaningful on
1040
platforms for which shared libraries are supported.  The different
1041
variants of this option are for compatibility with various systems.  You
1042
may use this option multiple times on the command line: it affects
1043
library searching for \fB\-l\fR options which follow it.  This
1044
option also implies \fB\-\-unresolved\-symbols=report\-all\fR.  This
1045
option can be used with \fB\-shared\fR.  Doing so means that a
1046
shared library is being created but that all of the library's external
1047
references must be resolved by pulling in entries from static
1048
libraries.
1049
.IP "\fB\-Bsymbolic\fR" 4
1050
.IX Item "-Bsymbolic"
1051
When creating a shared library, bind references to global symbols to the
1052
definition within the shared library, if any.  Normally, it is possible
1053
for a program linked against a shared library to override the definition
1054
within the shared library.  This option is only meaningful on \s-1ELF\s0
1055
platforms which support shared libraries.
1056
.IP "\fB\-Bsymbolic\-functions\fR" 4
1057
.IX Item "-Bsymbolic-functions"
1058
When creating a shared library, bind references to global function
1059
symbols to the definition within the shared library, if any.
1060
This option is only meaningful on \s-1ELF\s0 platforms which support shared
1061
libraries.
1062
.IP "\fB\-\-dynamic\-list=\fR\fIdynamic-list-file\fR" 4
1063
.IX Item "--dynamic-list=dynamic-list-file"
1064
Specify the name of a dynamic list file to the linker.  This is
1065
typically used when creating shared libraries to specify a list of
1066
global symbols whose references shouldn't be bound to the definition
1067
within the shared library, or creating dynamically linked executables
1068
to specify a list of symbols which should be added to the symbol table
1069
in the executable.  This option is only meaningful on \s-1ELF\s0 platforms
1070
which support shared libraries.
1071
.Sp
1072
The format of the dynamic list is the same as the version node without
1073
scope and node name.  See \fB\s-1VERSION\s0\fR for more information.
1074
.IP "\fB\-\-dynamic\-list\-data\fR" 4
1075
.IX Item "--dynamic-list-data"
1076
Include all global data symbols to the dynamic list.
1077
.IP "\fB\-\-dynamic\-list\-cpp\-new\fR" 4
1078
.IX Item "--dynamic-list-cpp-new"
1079
Provide the builtin dynamic list for \*(C+ operator new and delete.  It
1080
is mainly useful for building shared libstdc++.
1081
.IP "\fB\-\-dynamic\-list\-cpp\-typeinfo\fR" 4
1082
.IX Item "--dynamic-list-cpp-typeinfo"
1083
Provide the builtin dynamic list for \*(C+ runtime type identification.
1084
.IP "\fB\-\-check\-sections\fR" 4
1085
.IX Item "--check-sections"
1086
.PD 0
1087
.IP "\fB\-\-no\-check\-sections\fR" 4
1088
.IX Item "--no-check-sections"
1089
.PD
1090
Asks the linker \fInot\fR to check section addresses after they have
1091
been assigned to see if there are any overlaps.  Normally the linker will
1092
perform this check, and if it finds any overlaps it will produce
1093
suitable error messages.  The linker does know about, and does make
1094
allowances for sections in overlays.  The default behaviour can be
1095
restored by using the command line switch \fB\-\-check\-sections\fR.
1096
Section overlap is not usually checked for relocatable links.  You can
1097
force checking in that case by using the \fB\-\-check\-sections\fR
1098
option.
1099
.IP "\fB\-\-cref\fR" 4
1100
.IX Item "--cref"
1101
Output a cross reference table.  If a linker map file is being
1102
generated, the cross reference table is printed to the map file.
1103
Otherwise, it is printed on the standard output.
1104
.Sp
1105
The format of the table is intentionally simple, so that it may be
1106
easily processed by a script if necessary.  The symbols are printed out,
1107
sorted by name.  For each symbol, a list of file names is given.  If the
1108
symbol is defined, the first file listed is the location of the
1109
definition.  The remaining files contain references to the symbol.
1110
.IP "\fB\-\-no\-define\-common\fR" 4
1111
.IX Item "--no-define-common"
1112
This option inhibits the assignment of addresses to common symbols.
1113
The script command \f(CW\*(C`INHIBIT_COMMON_ALLOCATION\*(C'\fR has the same effect.
1114
.Sp
1115
The \fB\-\-no\-define\-common\fR option allows decoupling
1116
the decision to assign addresses to Common symbols from the choice
1117
of the output file type; otherwise a non-Relocatable output type
1118
forces assigning addresses to Common symbols.
1119
Using \fB\-\-no\-define\-common\fR allows Common symbols that are referenced
1120
from a shared library to be assigned addresses only in the main program.
1121
This eliminates the unused duplicate space in the shared library,
1122
and also prevents any possible confusion over resolving to the wrong
1123
duplicate when there are many dynamic modules with specialized search
1124
paths for runtime symbol resolution.
1125
.IP "\fB\-\-defsym=\fR\fIsymbol\fR\fB=\fR\fIexpression\fR" 4
1126
.IX Item "--defsym=symbol=expression"
1127
Create a global symbol in the output file, containing the absolute
1128
address given by \fIexpression\fR.  You may use this option as many
1129
times as necessary to define multiple symbols in the command line.  A
1130
limited form of arithmetic is supported for the \fIexpression\fR in this
1131
context: you may give a hexadecimal constant or the name of an existing
1132
symbol, or use \f(CW\*(C`+\*(C'\fR and \f(CW\*(C`\-\*(C'\fR to add or subtract hexadecimal
1133
constants or symbols.  If you need more elaborate expressions, consider
1134
using the linker command language from a script.  \fINote:\fR there should be no white
1135
space between \fIsymbol\fR, the equals sign ("\fB=\fR"), and
1136
\&\fIexpression\fR.
1137
.IP "\fB\-\-demangle[=\fR\fIstyle\fR\fB]\fR" 4
1138
.IX Item "--demangle[=style]"
1139
.PD 0
1140
.IP "\fB\-\-no\-demangle\fR" 4
1141
.IX Item "--no-demangle"
1142
.PD
1143
These options control whether to demangle symbol names in error messages
1144
and other output.  When the linker is told to demangle, it tries to
1145
present symbol names in a readable fashion: it strips leading
1146
underscores if they are used by the object file format, and converts \*(C+
1147
mangled symbol names into user readable names.  Different compilers have
1148
different mangling styles.  The optional demangling style argument can be used
1149
to choose an appropriate demangling style for your compiler.  The linker will
1150
demangle by default unless the environment variable \fB\s-1COLLECT_NO_DEMANGLE\s0\fR
1151
is set.  These options may be used to override the default.
1152
.IP "\fB\-I\fR\fIfile\fR" 4
1153
.IX Item "-Ifile"
1154
.PD 0
1155
.IP "\fB\-\-dynamic\-linker=\fR\fIfile\fR" 4
1156
.IX Item "--dynamic-linker=file"
1157
.PD
1158
Set the name of the dynamic linker.  This is only meaningful when
1159
generating dynamically linked \s-1ELF\s0 executables.  The default dynamic
1160
linker is normally correct; don't use this unless you know what you are
1161
doing.
1162
.IP "\fB\-\-fatal\-warnings\fR" 4
1163
.IX Item "--fatal-warnings"
1164
.PD 0
1165
.IP "\fB\-\-no\-fatal\-warnings\fR" 4
1166
.IX Item "--no-fatal-warnings"
1167
.PD
1168
Treat all warnings as errors.  The default behaviour can be restored
1169
with the option \fB\-\-no\-fatal\-warnings\fR.
1170
.IP "\fB\-\-force\-exe\-suffix\fR" 4
1171
.IX Item "--force-exe-suffix"
1172
Make sure that an output file has a .exe suffix.
1173
.Sp
1174
If a successfully built fully linked output file does not have a
1175
\&\f(CW\*(C`.exe\*(C'\fR or \f(CW\*(C`.dll\*(C'\fR suffix, this option forces the linker to copy
1176
the output file to one of the same name with a \f(CW\*(C`.exe\*(C'\fR suffix. This
1177
option is useful when using unmodified Unix makefiles on a Microsoft
1178
Windows host, since some versions of Windows won't run an image unless
1179
it ends in a \f(CW\*(C`.exe\*(C'\fR suffix.
1180
.IP "\fB\-\-gc\-sections\fR" 4
1181
.IX Item "--gc-sections"
1182
.PD 0
1183
.IP "\fB\-\-no\-gc\-sections\fR" 4
1184
.IX Item "--no-gc-sections"
1185
.PD
1186
Enable garbage collection of unused input sections.  It is ignored on
1187
targets that do not support this option.  The default behaviour (of not
1188
performing this garbage collection) can be restored by specifying
1189
\&\fB\-\-no\-gc\-sections\fR on the command line.
1190
.Sp
1191
\&\fB\-\-gc\-sections\fR decides which input sections are used by
1192
examining symbols and relocations.  The section containing the entry
1193
symbol and all sections containing symbols undefined on the
1194
command-line will be kept, as will sections containing symbols
1195
referenced by dynamic objects.  Note that when building shared
1196
libraries, the linker must assume that any visible symbol is
1197
referenced.  Once this initial set of sections has been determined,
1198
the linker recursively marks as used any section referenced by their
1199
relocations.  See \fB\-\-entry\fR and \fB\-\-undefined\fR.
1200
.Sp
1201
This option can be set when doing a partial link (enabled with option
1202
\&\fB\-r\fR).  In this case the root of symbols kept must be explicitely
1203
specified either by an \fB\-\-entry\fR or \fB\-\-undefined\fR option or by
1204
a \f(CW\*(C`ENTRY\*(C'\fR command in the linker script.
1205
.IP "\fB\-\-print\-gc\-sections\fR" 4
1206
.IX Item "--print-gc-sections"
1207
.PD 0
1208
.IP "\fB\-\-no\-print\-gc\-sections\fR" 4
1209
.IX Item "--no-print-gc-sections"
1210
.PD
1211
List all sections removed by garbage collection.  The listing is
1212
printed on stderr.  This option is only effective if garbage
1213
collection has been enabled via the \fB\-\-gc\-sections\fR) option.  The
1214
default behaviour (of not listing the sections that are removed) can
1215
be restored by specifying \fB\-\-no\-print\-gc\-sections\fR on the command
1216
line.
1217
.IP "\fB\-\-help\fR" 4
1218
.IX Item "--help"
1219
Print a summary of the command-line options on the standard output and exit.
1220
.IP "\fB\-\-target\-help\fR" 4
1221
.IX Item "--target-help"
1222
Print a summary of all target specific options on the standard output and exit.
1223
.IP "\fB\-Map=\fR\fImapfile\fR" 4
1224
.IX Item "-Map=mapfile"
1225
Print a link map to the file \fImapfile\fR.  See the description of the
1226
\&\fB\-M\fR option, above.
1227
.IP "\fB\-\-no\-keep\-memory\fR" 4
1228
.IX Item "--no-keep-memory"
1229
\&\fBld\fR normally optimizes for speed over memory usage by caching the
1230
symbol tables of input files in memory.  This option tells \fBld\fR to
1231
instead optimize for memory usage, by rereading the symbol tables as
1232
necessary.  This may be required if \fBld\fR runs out of memory space
1233
while linking a large executable.
1234
.IP "\fB\-\-no\-undefined\fR" 4
1235
.IX Item "--no-undefined"
1236
.PD 0
1237
.IP "\fB\-z defs\fR" 4
1238
.IX Item "-z defs"
1239
.PD
1240
Report unresolved symbol references from regular object files.  This
1241
is done even if the linker is creating a non-symbolic shared library.
1242
The switch \fB\-\-[no\-]allow\-shlib\-undefined\fR controls the
1243
behaviour for reporting unresolved references found in shared
1244
libraries being linked in.
1245
.IP "\fB\-\-allow\-multiple\-definition\fR" 4
1246
.IX Item "--allow-multiple-definition"
1247
.PD 0
1248
.IP "\fB\-z muldefs\fR" 4
1249
.IX Item "-z muldefs"
1250
.PD
1251
Normally when a symbol is defined multiple times, the linker will
1252
report a fatal error. These options allow multiple definitions and the
1253
first definition will be used.
1254
.IP "\fB\-\-allow\-shlib\-undefined\fR" 4
1255
.IX Item "--allow-shlib-undefined"
1256
.PD 0
1257
.IP "\fB\-\-no\-allow\-shlib\-undefined\fR" 4
1258
.IX Item "--no-allow-shlib-undefined"
1259
.PD
1260
Allows or disallows undefined symbols in shared libraries.
1261
This switch is similar to \fB\-\-no\-undefined\fR except that it
1262
determines the behaviour when the undefined symbols are in a
1263
shared library rather than a regular object file.  It does not affect
1264
how undefined symbols in regular object files are handled.
1265
.Sp
1266
The default behaviour is to report errors for any undefined symbols
1267
referenced in shared libraries if the linker is being used to create
1268
an executable, but to allow them if the linker is being used to create
1269
a shared library.
1270
.Sp
1271
The reasons for allowing undefined symbol references in shared
1272
libraries specified at link time are that:
1273
.RS 4
1274
.IP "\(bu" 4
1275
A shared library specified at link time may not be the same as the one
1276
that is available at load time, so the symbol might actually be
1277
resolvable at load time.
1278
.IP "\(bu" 4
1279
There are some operating systems, eg BeOS and \s-1HPPA\s0, where undefined
1280
symbols in shared libraries are normal.
1281
.Sp
1282
The BeOS kernel for example patches shared libraries at load time to
1283
select whichever function is most appropriate for the current
1284
architecture.  This is used, for example, to dynamically select an
1285
appropriate memset function.
1286
.RE
1287
.RS 4
1288
.RE
1289
.IP "\fB\-\-no\-undefined\-version\fR" 4
1290
.IX Item "--no-undefined-version"
1291
Normally when a symbol has an undefined version, the linker will ignore
1292
it. This option disallows symbols with undefined version and a fatal error
1293
will be issued instead.
1294
.IP "\fB\-\-default\-symver\fR" 4
1295
.IX Item "--default-symver"
1296
Create and use a default symbol version (the soname) for unversioned
1297
exported symbols.
1298
.IP "\fB\-\-default\-imported\-symver\fR" 4
1299
.IX Item "--default-imported-symver"
1300
Create and use a default symbol version (the soname) for unversioned
1301
imported symbols.
1302
.IP "\fB\-\-no\-warn\-mismatch\fR" 4
1303
.IX Item "--no-warn-mismatch"
1304
Normally \fBld\fR will give an error if you try to link together input
1305
files that are mismatched for some reason, perhaps because they have
1306
been compiled for different processors or for different endiannesses.
1307
This option tells \fBld\fR that it should silently permit such possible
1308
errors.  This option should only be used with care, in cases when you
1309
have taken some special action that ensures that the linker errors are
1310
inappropriate.
1311
.IP "\fB\-\-no\-warn\-search\-mismatch\fR" 4
1312
.IX Item "--no-warn-search-mismatch"
1313
Normally \fBld\fR will give a warning if it finds an incompatible
1314
library during a library search.  This option silences the warning.
1315
.IP "\fB\-\-no\-whole\-archive\fR" 4
1316
.IX Item "--no-whole-archive"
1317
Turn off the effect of the \fB\-\-whole\-archive\fR option for subsequent
1318
archive files.
1319
.IP "\fB\-\-noinhibit\-exec\fR" 4
1320
.IX Item "--noinhibit-exec"
1321
Retain the executable output file whenever it is still usable.
1322
Normally, the linker will not produce an output file if it encounters
1323
errors during the link process; it exits without writing an output file
1324
when it issues any error whatsoever.
1325
.IP "\fB\-nostdlib\fR" 4
1326
.IX Item "-nostdlib"
1327
Only search library directories explicitly specified on the
1328
command line.  Library directories specified in linker scripts
1329
(including linker scripts specified on the command line) are ignored.
1330
.IP "\fB\-\-oformat=\fR\fIoutput-format\fR" 4
1331
.IX Item "--oformat=output-format"
1332
\&\fBld\fR may be configured to support more than one kind of object
1333
file.  If your \fBld\fR is configured this way, you can use the
1334
\&\fB\-\-oformat\fR option to specify the binary format for the output
1335
object file.  Even when \fBld\fR is configured to support alternative
1336
object formats, you don't usually need to specify this, as \fBld\fR
1337
should be configured to produce as a default output format the most
1338
usual format on each machine.  \fIoutput-format\fR is a text string, the
1339
name of a particular format supported by the \s-1BFD\s0 libraries.  (You can
1340
list the available binary formats with \fBobjdump \-i\fR.)  The script
1341
command \f(CW\*(C`OUTPUT_FORMAT\*(C'\fR can also specify the output format, but
1342
this option overrides it.
1343
.IP "\fB\-pie\fR" 4
1344
.IX Item "-pie"
1345
.PD 0
1346
.IP "\fB\-\-pic\-executable\fR" 4
1347
.IX Item "--pic-executable"
1348
.PD
1349
Create a position independent executable.  This is currently only supported on
1350
\&\s-1ELF\s0 platforms.  Position independent executables are similar to shared
1351
libraries in that they are relocated by the dynamic linker to the virtual
1352
address the \s-1OS\s0 chooses for them (which can vary between invocations).  Like
1353
normal dynamically linked executables they can be executed and symbols
1354
defined in the executable cannot be overridden by shared libraries.
1355
.IP "\fB\-qmagic\fR" 4
1356
.IX Item "-qmagic"
1357
This option is ignored for Linux compatibility.
1358
.IP "\fB\-Qy\fR" 4
1359
.IX Item "-Qy"
1360
This option is ignored for \s-1SVR4\s0 compatibility.
1361
.IP "\fB\-\-relax\fR" 4
1362
.IX Item "--relax"
1363
An option with machine dependent effects.
1364
This option is only supported on a few targets.
1365
.Sp
1366
On some platforms, the \fB\-\-relax\fR option performs global
1367
optimizations that become possible when the linker resolves addressing
1368
in the program, such as relaxing address modes and synthesizing new
1369
instructions in the output object file.
1370
.Sp
1371
On some platforms these link time global optimizations may make symbolic
1372
debugging of the resulting executable impossible.
1373
This is known to be
1374
the case for the Matsushita \s-1MN10200\s0 and \s-1MN10300\s0 family of processors.
1375
.Sp
1376
On platforms where this is not supported, \fB\-\-relax\fR is accepted,
1377
but ignored.
1378
.IP "\fB\-\-retain\-symbols\-file=\fR\fIfilename\fR" 4
1379
.IX Item "--retain-symbols-file=filename"
1380
Retain \fIonly\fR the symbols listed in the file \fIfilename\fR,
1381
discarding all others.  \fIfilename\fR is simply a flat file, with one
1382
symbol name per line.  This option is especially useful in environments
1383
(such as VxWorks)
1384
where a large global symbol table is accumulated gradually, to conserve
1385
run-time memory.
1386
.Sp
1387
\&\fB\-\-retain\-symbols\-file\fR does \fInot\fR discard undefined symbols,
1388
or symbols needed for relocations.
1389
.Sp
1390
You may only specify \fB\-\-retain\-symbols\-file\fR once in the command
1391
line.  It overrides \fB\-s\fR and \fB\-S\fR.
1392
.IP "\fB\-rpath=\fR\fIdir\fR" 4
1393
.IX Item "-rpath=dir"
1394
Add a directory to the runtime library search path.  This is used when
1395
linking an \s-1ELF\s0 executable with shared objects.  All \fB\-rpath\fR
1396
arguments are concatenated and passed to the runtime linker, which uses
1397
them to locate shared objects at runtime.  The \fB\-rpath\fR option is
1398
also used when locating shared objects which are needed by shared
1399
objects explicitly included in the link; see the description of the
1400
\&\fB\-rpath\-link\fR option.  If \fB\-rpath\fR is not used when linking an
1401
\&\s-1ELF\s0 executable, the contents of the environment variable
1402
\&\f(CW\*(C`LD_RUN_PATH\*(C'\fR will be used if it is defined.
1403
.Sp
1404
The \fB\-rpath\fR option may also be used on SunOS.  By default, on
1405
SunOS, the linker will form a runtime search patch out of all the
1406
\&\fB\-L\fR options it is given.  If a \fB\-rpath\fR option is used, the
1407
runtime search path will be formed exclusively using the \fB\-rpath\fR
1408
options, ignoring the \fB\-L\fR options.  This can be useful when using
1409
gcc, which adds many \fB\-L\fR options which may be on \s-1NFS\s0 mounted
1410
file systems.
1411
.Sp
1412
For compatibility with other \s-1ELF\s0 linkers, if the \fB\-R\fR option is
1413
followed by a directory name, rather than a file name, it is treated as
1414
the \fB\-rpath\fR option.
1415
.IP "\fB\-rpath\-link=\fR\fIdir\fR" 4
1416
.IX Item "-rpath-link=dir"
1417
When using \s-1ELF\s0 or SunOS, one shared library may require another.  This
1418
happens when an \f(CW\*(C`ld \-shared\*(C'\fR link includes a shared library as one
1419
of the input files.
1420
.Sp
1421
When the linker encounters such a dependency when doing a non-shared,
1422
non-relocatable link, it will automatically try to locate the required
1423
shared library and include it in the link, if it is not included
1424
explicitly.  In such a case, the \fB\-rpath\-link\fR option
1425
specifies the first set of directories to search.  The
1426
\&\fB\-rpath\-link\fR option may specify a sequence of directory names
1427
either by specifying a list of names separated by colons, or by
1428
appearing multiple times.
1429
.Sp
1430
This option should be used with caution as it overrides the search path
1431
that may have been hard compiled into a shared library. In such a case it
1432
is possible to use unintentionally a different search path than the
1433
runtime linker would do.
1434
.Sp
1435
The linker uses the following search paths to locate required shared
1436
libraries:
1437
.RS 4
1438
.IP "1." 4
1439
Any directories specified by \fB\-rpath\-link\fR options.
1440
.IP "2." 4
1441
Any directories specified by \fB\-rpath\fR options.  The difference
1442
between \fB\-rpath\fR and \fB\-rpath\-link\fR is that directories
1443
specified by \fB\-rpath\fR options are included in the executable and
1444
used at runtime, whereas the \fB\-rpath\-link\fR option is only effective
1445
at link time. Searching \fB\-rpath\fR in this way is only supported
1446
by native linkers and cross linkers which have been configured with
1447
the \fB\-\-with\-sysroot\fR option.
1448
.IP "3." 4
1449
On an \s-1ELF\s0 system, for native linkers, if the \fB\-rpath\fR and
1450
\&\fB\-rpath\-link\fR options were not used, search the contents of the
1451
environment variable \f(CW\*(C`LD_RUN_PATH\*(C'\fR.
1452
.IP "4." 4
1453
On SunOS, if the \fB\-rpath\fR option was not used, search any
1454
directories specified using \fB\-L\fR options.
1455
.IP "5." 4
1456
For a native linker, the search the contents of the environment
1457
variable \f(CW\*(C`LD_LIBRARY_PATH\*(C'\fR.
1458
.IP "6." 4
1459
For a native \s-1ELF\s0 linker, the directories in \f(CW\*(C`DT_RUNPATH\*(C'\fR or
1460
\&\f(CW\*(C`DT_RPATH\*(C'\fR of a shared library are searched for shared
1461
libraries needed by it. The \f(CW\*(C`DT_RPATH\*(C'\fR entries are ignored if
1462
\&\f(CW\*(C`DT_RUNPATH\*(C'\fR entries exist.
1463
.IP "7." 4
1464
The default directories, normally \fI/lib\fR and \fI/usr/lib\fR.
1465
.IP "8." 4
1466
For a native linker on an \s-1ELF\s0 system, if the file \fI/etc/ld.so.conf\fR
1467
exists, the list of directories found in that file.
1468
.RE
1469
.RS 4
1470
.Sp
1471
If the required shared library is not found, the linker will issue a
1472
warning and continue with the link.
1473
.RE
1474
.IP "\fB\-shared\fR" 4
1475
.IX Item "-shared"
1476
.PD 0
1477
.IP "\fB\-Bshareable\fR" 4
1478
.IX Item "-Bshareable"
1479
.PD
1480
Create a shared library.  This is currently only supported on \s-1ELF\s0, \s-1XCOFF\s0
1481
and SunOS platforms.  On SunOS, the linker will automatically create a
1482
shared library if the \fB\-e\fR option is not used and there are
1483
undefined symbols in the link.
1484
.IP "\fB\-\-sort\-common\fR" 4
1485
.IX Item "--sort-common"
1486
.PD 0
1487
.IP "\fB\-\-sort\-common=ascending\fR" 4
1488
.IX Item "--sort-common=ascending"
1489
.IP "\fB\-\-sort\-common=descending\fR" 4
1490
.IX Item "--sort-common=descending"
1491
.PD
1492
This option tells \fBld\fR to sort the common symbols by alignment in
1493
ascending or descending order when it places them in the appropriate output
1494
sections.  The symbol alignments considered are sixteen-byte or larger,
1495
eight-byte, four-byte, two-byte, and one-byte. This is to prevent gaps
1496
between symbols due to alignment constraints.  If no sorting order is
1497
specified, then descending order is assumed.
1498
.IP "\fB\-\-sort\-section=name\fR" 4
1499
.IX Item "--sort-section=name"
1500
This option will apply \f(CW\*(C`SORT_BY_NAME\*(C'\fR to all wildcard section
1501
patterns in the linker script.
1502
.IP "\fB\-\-sort\-section=alignment\fR" 4
1503
.IX Item "--sort-section=alignment"
1504
This option will apply \f(CW\*(C`SORT_BY_ALIGNMENT\*(C'\fR to all wildcard section
1505
patterns in the linker script.
1506
.IP "\fB\-\-split\-by\-file[=\fR\fIsize\fR\fB]\fR" 4
1507
.IX Item "--split-by-file[=size]"
1508
Similar to \fB\-\-split\-by\-reloc\fR but creates a new output section for
1509
each input file when \fIsize\fR is reached.  \fIsize\fR defaults to a
1510
size of 1 if not given.
1511
.IP "\fB\-\-split\-by\-reloc[=\fR\fIcount\fR\fB]\fR" 4
1512
.IX Item "--split-by-reloc[=count]"
1513
Tries to creates extra sections in the output file so that no single
1514
output section in the file contains more than \fIcount\fR relocations.
1515
This is useful when generating huge relocatable files for downloading into
1516
certain real time kernels with the \s-1COFF\s0 object file format; since \s-1COFF\s0
1517
cannot represent more than 65535 relocations in a single section.  Note
1518
that this will fail to work with object file formats which do not
1519
support arbitrary sections.  The linker will not split up individual
1520
input sections for redistribution, so if a single input section contains
1521
more than \fIcount\fR relocations one output section will contain that
1522
many relocations.  \fIcount\fR defaults to a value of 32768.
1523
.IP "\fB\-\-stats\fR" 4
1524
.IX Item "--stats"
1525
Compute and display statistics about the operation of the linker, such
1526
as execution time and memory usage.
1527
.IP "\fB\-\-sysroot=\fR\fIdirectory\fR" 4
1528
.IX Item "--sysroot=directory"
1529
Use \fIdirectory\fR as the location of the sysroot, overriding the
1530
configure-time default.  This option is only supported by linkers
1531
that were configured using \fB\-\-with\-sysroot\fR.
1532
.IP "\fB\-\-traditional\-format\fR" 4
1533
.IX Item "--traditional-format"
1534
For some targets, the output of \fBld\fR is different in some ways from
1535
the output of some existing linker.  This switch requests \fBld\fR to
1536
use the traditional format instead.
1537
.Sp
1538
For example, on SunOS, \fBld\fR combines duplicate entries in the
1539
symbol string table.  This can reduce the size of an output file with
1540
full debugging information by over 30 percent.  Unfortunately, the SunOS
1541
\&\f(CW\*(C`dbx\*(C'\fR program can not read the resulting program (\f(CW\*(C`gdb\*(C'\fR has no
1542
trouble).  The \fB\-\-traditional\-format\fR switch tells \fBld\fR to not
1543
combine duplicate entries.
1544
.IP "\fB\-\-section\-start=\fR\fIsectionname\fR\fB=\fR\fIorg\fR" 4
1545
.IX Item "--section-start=sectionname=org"
1546
Locate a section in the output file at the absolute
1547
address given by \fIorg\fR.  You may use this option as many
1548
times as necessary to locate multiple sections in the command
1549
line.
1550
\&\fIorg\fR must be a single hexadecimal integer;
1551
for compatibility with other linkers, you may omit the leading
1552
\&\fB0x\fR usually associated with hexadecimal values.  \fINote:\fR there
1553
should be no white space between \fIsectionname\fR, the equals
1554
sign ("\fB=\fR"), and \fIorg\fR.
1555
.IP "\fB\-Tbss=\fR\fIorg\fR" 4
1556
.IX Item "-Tbss=org"
1557
.PD 0
1558
.IP "\fB\-Tdata=\fR\fIorg\fR" 4
1559
.IX Item "-Tdata=org"
1560
.IP "\fB\-Ttext=\fR\fIorg\fR" 4
1561
.IX Item "-Ttext=org"
1562
.PD
1563
Same as \fB\-\-section\-start\fR, with \f(CW\*(C`.bss\*(C'\fR, \f(CW\*(C`.data\*(C'\fR or
1564
\&\f(CW\*(C`.text\*(C'\fR as the \fIsectionname\fR.
1565
.IP "\fB\-Ttext\-segment=\fR\fIorg\fR" 4
1566
.IX Item "-Ttext-segment=org"
1567
When creating an \s-1ELF\s0 executable or shared object, it will set the address
1568
of the first byte of the text segment.
1569
.IP "\fB\-\-unresolved\-symbols=\fR\fImethod\fR" 4
1570
.IX Item "--unresolved-symbols=method"
1571
Determine how to handle unresolved symbols.  There are four possible
1572
values for \fBmethod\fR:
1573
.RS 4
1574
.IP "\fBignore-all\fR" 4
1575
.IX Item "ignore-all"
1576
Do not report any unresolved symbols.
1577
.IP "\fBreport-all\fR" 4
1578
.IX Item "report-all"
1579
Report all unresolved symbols.  This is the default.
1580
.IP "\fBignore-in-object-files\fR" 4
1581
.IX Item "ignore-in-object-files"
1582
Report unresolved symbols that are contained in shared libraries, but
1583
ignore them if they come from regular object files.
1584
.IP "\fBignore-in-shared-libs\fR" 4
1585
.IX Item "ignore-in-shared-libs"
1586
Report unresolved symbols that come from regular object files, but
1587
ignore them if they come from shared libraries.  This can be useful
1588
when creating a dynamic binary and it is known that all the shared
1589
libraries that it should be referencing are included on the linker's
1590
command line.
1591
.RE
1592
.RS 4
1593
.Sp
1594
The behaviour for shared libraries on their own can also be controlled
1595
by the \fB\-\-[no\-]allow\-shlib\-undefined\fR option.
1596
.Sp
1597
Normally the linker will generate an error message for each reported
1598
unresolved symbol but the option \fB\-\-warn\-unresolved\-symbols\fR
1599
can change this to a warning.
1600
.RE
1601
.IP "\fB\-\-dll\-verbose\fR" 4
1602
.IX Item "--dll-verbose"
1603
.PD 0
1604
.IP "\fB\-\-verbose\fR" 4
1605
.IX Item "--verbose"
1606
.PD
1607
Display the version number for \fBld\fR and list the linker emulations
1608
supported.  Display which input files can and cannot be opened.  Display
1609
the linker script being used by the linker.
1610
.IP "\fB\-\-version\-script=\fR\fIversion-scriptfile\fR" 4
1611
.IX Item "--version-script=version-scriptfile"
1612
Specify the name of a version script to the linker.  This is typically
1613
used when creating shared libraries to specify additional information
1614
about the version hierarchy for the library being created.  This option
1615
is only fully supported on \s-1ELF\s0 platforms which support shared libraries;
1616
see \fB\s-1VERSION\s0\fR.  It is partially supported on \s-1PE\s0 platforms, which can
1617
use version scripts to filter symbol visibility in auto-export mode: any
1618
symbols marked \fBlocal\fR in the version script will not be exported.
1619
.IP "\fB\-\-warn\-common\fR" 4
1620
.IX Item "--warn-common"
1621
Warn when a common symbol is combined with another common symbol or with
1622
a symbol definition.  Unix linkers allow this somewhat sloppy practise,
1623
but linkers on some other operating systems do not.  This option allows
1624
you to find potential problems from combining global symbols.
1625
Unfortunately, some C libraries use this practise, so you may get some
1626
warnings about symbols in the libraries as well as in your programs.
1627
.Sp
1628
There are three kinds of global symbols, illustrated here by C examples:
1629
.RS 4
1630
.IP "\fBint i = 1;\fR" 4
1631
.IX Item "int i = 1;"
1632
A definition, which goes in the initialized data section of the output
1633
file.
1634
.IP "\fBextern int i;\fR" 4
1635
.IX Item "extern int i;"
1636
An undefined reference, which does not allocate space.
1637
There must be either a definition or a common symbol for the
1638
variable somewhere.
1639
.IP "\fBint i;\fR" 4
1640
.IX Item "int i;"
1641
A common symbol.  If there are only (one or more) common symbols for a
1642
variable, it goes in the uninitialized data area of the output file.
1643
The linker merges multiple common symbols for the same variable into a
1644
single symbol.  If they are of different sizes, it picks the largest
1645
size.  The linker turns a common symbol into a declaration, if there is
1646
a definition of the same variable.
1647
.RE
1648
.RS 4
1649
.Sp
1650
The \fB\-\-warn\-common\fR option can produce five kinds of warnings.
1651
Each warning consists of a pair of lines: the first describes the symbol
1652
just encountered, and the second describes the previous symbol
1653
encountered with the same name.  One or both of the two symbols will be
1654
a common symbol.
1655
.IP "1." 4
1656
Turning a common symbol into a reference, because there is already a
1657
definition for the symbol.
1658
.Sp
1659
.Vb 3
1660
\&        (
): warning: common of \`\*(Aq
1661
\&           overridden by definition
1662
\&        (
): warning: defined here
1663
.Ve
1664
.IP "2." 4
1665
Turning a common symbol into a reference, because a later definition for
1666
the symbol is encountered.  This is the same as the previous case,
1667
except that the symbols are encountered in a different order.
1668
.Sp
1669
.Vb 3
1670
\&        (
): warning: definition of \`\*(Aq
1671
\&           overriding common
1672
\&        (
): warning: common is here
1673
.Ve
1674
.IP "3." 4
1675
Merging a common symbol with a previous same-sized common symbol.
1676
.Sp
1677
.Vb 3
1678
\&        (
): warning: multiple common
1679
\&           of \`\*(Aq
1680
\&        (
): warning: previous common is here
1681
.Ve
1682
.IP "4." 4
1683
Merging a common symbol with a previous larger common symbol.
1684
.Sp
1685
.Vb 3
1686
\&        (
): warning: common of \`\*(Aq
1687
\&           overridden by larger common
1688
\&        (
): warning: larger common is here
1689
.Ve
1690
.IP "5." 4
1691
Merging a common symbol with a previous smaller common symbol.  This is
1692
the same as the previous case, except that the symbols are
1693
encountered in a different order.
1694
.Sp
1695
.Vb 3
1696
\&        (
): warning: common of \`\*(Aq
1697
\&           overriding smaller common
1698
\&        (
): warning: smaller common is here
1699
.Ve
1700
.RE
1701
.RS 4
1702
.RE
1703
.IP "\fB\-\-warn\-constructors\fR" 4
1704
.IX Item "--warn-constructors"
1705
Warn if any global constructors are used.  This is only useful for a few
1706
object file formats.  For formats like \s-1COFF\s0 or \s-1ELF\s0, the linker can not
1707
detect the use of global constructors.
1708
.IP "\fB\-\-warn\-multiple\-gp\fR" 4
1709
.IX Item "--warn-multiple-gp"
1710
Warn if multiple global pointer values are required in the output file.
1711
This is only meaningful for certain processors, such as the Alpha.
1712
Specifically, some processors put large-valued constants in a special
1713
section.  A special register (the global pointer) points into the middle
1714
of this section, so that constants can be loaded efficiently via a
1715
base-register relative addressing mode.  Since the offset in
1716
base-register relative mode is fixed and relatively small (e.g., 16
1717
bits), this limits the maximum size of the constant pool.  Thus, in
1718
large programs, it is often necessary to use multiple global pointer
1719
values in order to be able to address all possible constants.  This
1720
option causes a warning to be issued whenever this case occurs.
1721
.IP "\fB\-\-warn\-once\fR" 4
1722
.IX Item "--warn-once"
1723
Only warn once for each undefined symbol, rather than once per module
1724
which refers to it.
1725
.IP "\fB\-\-warn\-section\-align\fR" 4
1726
.IX Item "--warn-section-align"
1727
Warn if the address of an output section is changed because of
1728
alignment.  Typically, the alignment will be set by an input section.
1729
The address will only be changed if it not explicitly specified; that
1730
is, if the \f(CW\*(C`SECTIONS\*(C'\fR command does not specify a start address for
1731
the section.
1732
.IP "\fB\-\-warn\-shared\-textrel\fR" 4
1733
.IX Item "--warn-shared-textrel"
1734
Warn if the linker adds a \s-1DT_TEXTREL\s0 to a shared object.
1735
.IP "\fB\-\-warn\-alternate\-em\fR" 4
1736
.IX Item "--warn-alternate-em"
1737
Warn if an object has alternate \s-1ELF\s0 machine code.
1738
.IP "\fB\-\-warn\-unresolved\-symbols\fR" 4
1739
.IX Item "--warn-unresolved-symbols"
1740
If the linker is going to report an unresolved symbol (see the option
1741
\&\fB\-\-unresolved\-symbols\fR) it will normally generate an error.
1742
This option makes it generate a warning instead.
1743
.IP "\fB\-\-error\-unresolved\-symbols\fR" 4
1744
.IX Item "--error-unresolved-symbols"
1745
This restores the linker's default behaviour of generating errors when
1746
it is reporting unresolved symbols.
1747
.IP "\fB\-\-whole\-archive\fR" 4
1748
.IX Item "--whole-archive"
1749
For each archive mentioned on the command line after the
1750
\&\fB\-\-whole\-archive\fR option, include every object file in the archive
1751
in the link, rather than searching the archive for the required object
1752
files.  This is normally used to turn an archive file into a shared
1753
library, forcing every object to be included in the resulting shared
1754
library.  This option may be used more than once.
1755
.Sp
1756
Two notes when using this option from gcc: First, gcc doesn't know
1757
about this option, so you have to use \fB\-Wl,\-whole\-archive\fR.
1758
Second, don't forget to use \fB\-Wl,\-no\-whole\-archive\fR after your
1759
list of archives, because gcc will add its own list of archives to
1760
your link and you may not want this flag to affect those as well.
1761
.IP "\fB\-\-wrap=\fR\fIsymbol\fR" 4
1762
.IX Item "--wrap=symbol"
1763
Use a wrapper function for \fIsymbol\fR.  Any undefined reference to
1764
\&\fIsymbol\fR will be resolved to \f(CW\*(C`_\|_wrap_\f(CIsymbol\f(CW\*(C'\fR.  Any
1765
undefined reference to \f(CW\*(C`_\|_real_\f(CIsymbol\f(CW\*(C'\fR will be resolved to
1766
\&\fIsymbol\fR.
1767
.Sp
1768
This can be used to provide a wrapper for a system function.  The
1769
wrapper function should be called \f(CW\*(C`_\|_wrap_\f(CIsymbol\f(CW\*(C'\fR.  If it
1770
wishes to call the system function, it should call
1771
\&\f(CW\*(C`_\|_real_\f(CIsymbol\f(CW\*(C'\fR.
1772
.Sp
1773
Here is a trivial example:
1774
.Sp
1775
.Vb 6
1776
\&        void *
1777
\&        _\|_wrap_malloc (size_t c)
1778
\&        {
1779
\&          printf ("malloc called with %zu\en", c);
1780
\&          return _\|_real_malloc (c);
1781
\&        }
1782
.Ve
1783
.Sp
1784
If you link other code with this file using \fB\-\-wrap malloc\fR, then
1785
all calls to \f(CW\*(C`malloc\*(C'\fR will call the function \f(CW\*(C`_\|_wrap_malloc\*(C'\fR
1786
instead.  The call to \f(CW\*(C`_\|_real_malloc\*(C'\fR in \f(CW\*(C`_\|_wrap_malloc\*(C'\fR will
1787
call the real \f(CW\*(C`malloc\*(C'\fR function.
1788
.Sp
1789
You may wish to provide a \f(CW\*(C`_\|_real_malloc\*(C'\fR function as well, so that
1790
links without the \fB\-\-wrap\fR option will succeed.  If you do this,
1791
you should not put the definition of \f(CW\*(C`_\|_real_malloc\*(C'\fR in the same
1792
file as \f(CW\*(C`_\|_wrap_malloc\*(C'\fR; if you do, the assembler may resolve the
1793
call before the linker has a chance to wrap it to \f(CW\*(C`malloc\*(C'\fR.
1794
.IP "\fB\-\-eh\-frame\-hdr\fR" 4
1795
.IX Item "--eh-frame-hdr"
1796
Request creation of \f(CW\*(C`.eh_frame_hdr\*(C'\fR section and \s-1ELF\s0
1797
\&\f(CW\*(C`PT_GNU_EH_FRAME\*(C'\fR segment header.
1798
.IP "\fB\-\-enable\-new\-dtags\fR" 4
1799
.IX Item "--enable-new-dtags"
1800
.PD 0
1801
.IP "\fB\-\-disable\-new\-dtags\fR" 4
1802
.IX Item "--disable-new-dtags"
1803
.PD
1804
This linker can create the new dynamic tags in \s-1ELF\s0. But the older \s-1ELF\s0
1805
systems may not understand them. If you specify
1806
\&\fB\-\-enable\-new\-dtags\fR, the dynamic tags will be created as needed.
1807
If you specify \fB\-\-disable\-new\-dtags\fR, no new dynamic tags will be
1808
created. By default, the new dynamic tags are not created. Note that
1809
those options are only available for \s-1ELF\s0 systems.
1810
.IP "\fB\-\-hash\-size=\fR\fInumber\fR" 4
1811
.IX Item "--hash-size=number"
1812
Set the default size of the linker's hash tables to a prime number
1813
close to \fInumber\fR.  Increasing this value can reduce the length of
1814
time it takes the linker to perform its tasks, at the expense of
1815
increasing the linker's memory requirements.  Similarly reducing this
1816
value can reduce the memory requirements at the expense of speed.
1817
.IP "\fB\-\-hash\-style=\fR\fIstyle\fR" 4
1818
.IX Item "--hash-style=style"
1819
Set the type of linker's hash table(s).  \fIstyle\fR can be either
1820
\&\f(CW\*(C`sysv\*(C'\fR for classic \s-1ELF\s0 \f(CW\*(C`.hash\*(C'\fR section, \f(CW\*(C`gnu\*(C'\fR for
1821
new style \s-1GNU\s0 \f(CW\*(C`.gnu.hash\*(C'\fR section or \f(CW\*(C`both\*(C'\fR for both
1822
the classic \s-1ELF\s0 \f(CW\*(C`.hash\*(C'\fR and new style \s-1GNU\s0 \f(CW\*(C`.gnu.hash\*(C'\fR
1823
hash tables.  The default is \f(CW\*(C`sysv\*(C'\fR.
1824
.IP "\fB\-\-reduce\-memory\-overheads\fR" 4
1825
.IX Item "--reduce-memory-overheads"
1826
This option reduces memory requirements at ld runtime, at the expense of
1827
linking speed.  This was introduced to select the old O(n^2) algorithm
1828
for link map file generation, rather than the new O(n) algorithm which uses
1829
about 40% more memory for symbol storage.
1830
.Sp
1831
Another effect of the switch is to set the default hash table size to
1832
1021, which again saves memory at the cost of lengthening the linker's
1833
run time.  This is not done however if the \fB\-\-hash\-size\fR switch
1834
has been used.
1835
.Sp
1836
The \fB\-\-reduce\-memory\-overheads\fR switch may be also be used to
1837
enable other tradeoffs in future versions of the linker.
1838
.IP "\fB\-\-build\-id\fR" 4
1839
.IX Item "--build-id"
1840
.PD 0
1841
.IP "\fB\-\-build\-id=\fR\fIstyle\fR" 4
1842
.IX Item "--build-id=style"
1843
.PD
1844
Request creation of \f(CW\*(C`.note.gnu.build\-id\*(C'\fR \s-1ELF\s0 note section.
1845
The contents of the note are unique bits identifying this linked
1846
file.  \fIstyle\fR can be \f(CW\*(C`uuid\*(C'\fR to use 128 random bits,
1847
\&\f(CW\*(C`sha1\*(C'\fR to use a 160\-bit \s-1SHA1\s0 hash on the normative
1848
parts of the output contents, \f(CW\*(C`md5\*(C'\fR to use a 128\-bit
1849
\&\s-1MD5\s0 hash on the normative parts of the output contents, or
1850
\&\f(CW\*(C`0x\f(CIhexstring\f(CW\*(C'\fR to use a chosen bit string specified as
1851
an even number of hexadecimal digits (\f(CW\*(C`\-\*(C'\fR and \f(CW\*(C`:\*(C'\fR
1852
characters between digit pairs are ignored).  If \fIstyle\fR is
1853
omitted, \f(CW\*(C`sha1\*(C'\fR is used.
1854
.Sp
1855
The \f(CW\*(C`md5\*(C'\fR and \f(CW\*(C`sha1\*(C'\fR styles produces an identifier
1856
that is always the same in an identical output file, but will be
1857
unique among all nonidentical output files.  It is not intended
1858
to be compared as a checksum for the file's contents.  A linked
1859
file may be changed later by other tools, but the build \s-1ID\s0 bit
1860
string identifying the original linked file does not change.
1861
.Sp
1862
Passing \f(CW\*(C`none\*(C'\fR for \fIstyle\fR disables the setting from any
1863
\&\f(CW\*(C`\-\-build\-id\*(C'\fR options earlier on the command line.
1864
.PP
1865
The i386 \s-1PE\s0 linker supports the \fB\-shared\fR option, which causes
1866
the output to be a dynamically linked library (\s-1DLL\s0) instead of a
1867
normal executable.  You should name the output \f(CW\*(C`*.dll\*(C'\fR when you
1868
use this option.  In addition, the linker fully supports the standard
1869
\&\f(CW\*(C`*.def\*(C'\fR files, which may be specified on the linker command line
1870
like an object file (in fact, it should precede archives it exports
1871
symbols from, to ensure that they get linked in, just like a normal
1872
object file).
1873
.PP
1874
In addition to the options common to all targets, the i386 \s-1PE\s0 linker
1875
support additional command line options that are specific to the i386
1876
\&\s-1PE\s0 target.  Options that take values may be separated from their
1877
values by either a space or an equals sign.
1878
.IP "\fB\-\-add\-stdcall\-alias\fR" 4
1879
.IX Item "--add-stdcall-alias"
1880
If given, symbols with a stdcall suffix (@\fInn\fR) will be exported
1881
as-is and also with the suffix stripped.
1882
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1883
.IP "\fB\-\-base\-file\fR \fIfile\fR" 4
1884
.IX Item "--base-file file"
1885
Use \fIfile\fR as the name of a file in which to save the base
1886
addresses of all the relocations needed for generating DLLs with
1887
\&\fIdlltool\fR.
1888
[This is an i386 \s-1PE\s0 specific option]
1889
.IP "\fB\-\-dll\fR" 4
1890
.IX Item "--dll"
1891
Create a \s-1DLL\s0 instead of a regular executable.  You may also use
1892
\&\fB\-shared\fR or specify a \f(CW\*(C`LIBRARY\*(C'\fR in a given \f(CW\*(C`.def\*(C'\fR
1893
file.
1894
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1895
.IP "\fB\-\-enable\-long\-section\-names\fR" 4
1896
.IX Item "--enable-long-section-names"
1897
.PD 0
1898
.IP "\fB\-\-disable\-long\-section\-names\fR" 4
1899
.IX Item "--disable-long-section-names"
1900
.PD
1901
The \s-1PE\s0 variants of the Coff object format add an extension that permits
1902
the use of section names longer than eight characters, the normal limit
1903
for Coff.  By default, these names are only allowed in object files, as
1904
fully-linked executable images do not carry the Coff string table required
1905
to support the longer names.  As a \s-1GNU\s0 extension, it is possible to
1906
allow their use in executable images as well, or to (probably pointlessly!)
1907
disallow it in object files, by using these two options.  Executable images
1908
generated with these long section names are slightly non-standard, carrying
1909
as they do a string table, and may generate confusing output when examined
1910
with non-GNU PE-aware tools, such as file viewers and dumpers.  However,
1911
\&\s-1GDB\s0 relies on the use of \s-1PE\s0 long section names to find Dwarf\-2 debug
1912
information sections in an executable image at runtime, and so if neither
1913
option is specified on the command-line, \fBld\fR will enable long
1914
section names, overriding the default and technically correct behaviour,
1915
when it finds the presence of debug information while linking an executable
1916
image and not stripping symbols.
1917
[This option is valid for all \s-1PE\s0 targeted ports of the linker]
1918
.IP "\fB\-\-enable\-stdcall\-fixup\fR" 4
1919
.IX Item "--enable-stdcall-fixup"
1920
.PD 0
1921
.IP "\fB\-\-disable\-stdcall\-fixup\fR" 4
1922
.IX Item "--disable-stdcall-fixup"
1923
.PD
1924
If the link finds a symbol that it cannot resolve, it will attempt to
1925
do \*(L"fuzzy linking\*(R" by looking for another defined symbol that differs
1926
only in the format of the symbol name (cdecl vs stdcall) and will
1927
resolve that symbol by linking to the match.  For example, the
1928
undefined symbol \f(CW\*(C`_foo\*(C'\fR might be linked to the function
1929
\&\f(CW\*(C`_foo@12\*(C'\fR, or the undefined symbol \f(CW\*(C`_bar@16\*(C'\fR might be linked
1930
to the function \f(CW\*(C`_bar\*(C'\fR.  When the linker does this, it prints a
1931
warning, since it normally should have failed to link, but sometimes
1932
import libraries generated from third-party dlls may need this feature
1933
to be usable.  If you specify \fB\-\-enable\-stdcall\-fixup\fR, this
1934
feature is fully enabled and warnings are not printed.  If you specify
1935
\&\fB\-\-disable\-stdcall\-fixup\fR, this feature is disabled and such
1936
mismatches are considered to be errors.
1937
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1938
.IP "\fB\-\-export\-all\-symbols\fR" 4
1939
.IX Item "--export-all-symbols"
1940
If given, all global symbols in the objects used to build a \s-1DLL\s0 will
1941
be exported by the \s-1DLL\s0.  Note that this is the default if there
1942
otherwise wouldn't be any exported symbols.  When symbols are
1943
explicitly exported via \s-1DEF\s0 files or implicitly exported via function
1944
attributes, the default is to not export anything else unless this
1945
option is given.  Note that the symbols \f(CW\*(C`DllMain@12\*(C'\fR,
1946
\&\f(CW\*(C`DllEntryPoint@0\*(C'\fR, \f(CW\*(C`DllMainCRTStartup@12\*(C'\fR, and
1947
\&\f(CW\*(C`impure_ptr\*(C'\fR will not be automatically
1948
exported.  Also, symbols imported from other DLLs will not be
1949
re-exported, nor will symbols specifying the \s-1DLL\s0's internal layout
1950
such as those beginning with \f(CW\*(C`_head_\*(C'\fR or ending with
1951
\&\f(CW\*(C`_iname\*(C'\fR.  In addition, no symbols from \f(CW\*(C`libgcc\*(C'\fR,
1952
\&\f(CW\*(C`libstd++\*(C'\fR, \f(CW\*(C`libmingw32\*(C'\fR, or \f(CW\*(C`crtX.o\*(C'\fR will be exported.
1953
Symbols whose names begin with \f(CW\*(C`_\|_rtti_\*(C'\fR or \f(CW\*(C`_\|_builtin_\*(C'\fR will
1954
not be exported, to help with \*(C+ DLLs.  Finally, there is an
1955
extensive list of cygwin-private symbols that are not exported
1956
(obviously, this applies on when building DLLs for cygwin targets).
1957
These cygwin-excludes are: \f(CW\*(C`_cygwin_dll_entry@12\*(C'\fR,
1958
\&\f(CW\*(C`_cygwin_crt0_common@8\*(C'\fR, \f(CW\*(C`_cygwin_noncygwin_dll_entry@12\*(C'\fR,
1959
\&\f(CW\*(C`_fmode\*(C'\fR, \f(CW\*(C`_impure_ptr\*(C'\fR, \f(CW\*(C`cygwin_attach_dll\*(C'\fR,
1960
\&\f(CW\*(C`cygwin_premain0\*(C'\fR, \f(CW\*(C`cygwin_premain1\*(C'\fR, \f(CW\*(C`cygwin_premain2\*(C'\fR,
1961
\&\f(CW\*(C`cygwin_premain3\*(C'\fR, and \f(CW\*(C`environ\*(C'\fR.
1962
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1963
.IP "\fB\-\-exclude\-symbols\fR \fIsymbol\fR\fB,\fR\fIsymbol\fR\fB,...\fR" 4
1964
.IX Item "--exclude-symbols symbol,symbol,..."
1965
Specifies a list of symbols which should not be automatically
1966
exported.  The symbol names may be delimited by commas or colons.
1967
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1968
.IP "\fB\-\-file\-alignment\fR" 4
1969
.IX Item "--file-alignment"
1970
Specify the file alignment.  Sections in the file will always begin at
1971
file offsets which are multiples of this number.  This defaults to
1972
512.
1973
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1974
.IP "\fB\-\-heap\fR \fIreserve\fR" 4
1975
.IX Item "--heap reserve"
1976
.PD 0
1977
.IP "\fB\-\-heap\fR \fIreserve\fR\fB,\fR\fIcommit\fR" 4
1978
.IX Item "--heap reserve,commit"
1979
.PD
1980
Specify the number of bytes of memory to reserve (and optionally commit)
1981
to be used as heap for this program.  The default is 1Mb reserved, 4K
1982
committed.
1983
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1984
.IP "\fB\-\-image\-base\fR \fIvalue\fR" 4
1985
.IX Item "--image-base value"
1986
Use \fIvalue\fR as the base address of your program or dll.  This is
1987
the lowest memory location that will be used when your program or dll
1988
is loaded.  To reduce the need to relocate and improve performance of
1989
your dlls, each should have a unique base address and not overlap any
1990
other dlls.  The default is 0x400000 for executables, and 0x10000000
1991
for dlls.
1992
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1993
.IP "\fB\-\-kill\-at\fR" 4
1994
.IX Item "--kill-at"
1995
If given, the stdcall suffixes (@\fInn\fR) will be stripped from
1996
symbols before they are exported.
1997
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
1998
.IP "\fB\-\-large\-address\-aware\fR" 4
1999
.IX Item "--large-address-aware"
2000
If given, the appropriate bit in the \*(L"Characteristics\*(R" field of the \s-1COFF\s0
2001
header is set to indicate that this executable supports virtual addresses
2002
greater than 2 gigabytes.  This should be used in conjunction with the /3GB
2003
or /USERVA=\fIvalue\fR megabytes switch in the \*(L"[operating systems]\*(R"
2004
section of the \s-1BOOT\s0.INI.  Otherwise, this bit has no effect.
2005
[This option is specific to \s-1PE\s0 targeted ports of the linker]
2006
.IP "\fB\-\-major\-image\-version\fR \fIvalue\fR" 4
2007
.IX Item "--major-image-version value"
2008
Sets the major number of the \*(L"image version\*(R".  Defaults to 1.
2009
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2010
.IP "\fB\-\-major\-os\-version\fR \fIvalue\fR" 4
2011
.IX Item "--major-os-version value"
2012
Sets the major number of the \*(L"os version\*(R".  Defaults to 4.
2013
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2014
.IP "\fB\-\-major\-subsystem\-version\fR \fIvalue\fR" 4
2015
.IX Item "--major-subsystem-version value"
2016
Sets the major number of the \*(L"subsystem version\*(R".  Defaults to 4.
2017
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2018
.IP "\fB\-\-minor\-image\-version\fR \fIvalue\fR" 4
2019
.IX Item "--minor-image-version value"
2020
Sets the minor number of the \*(L"image version\*(R".  Defaults to 0.
2021
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2022
.IP "\fB\-\-minor\-os\-version\fR \fIvalue\fR" 4
2023
.IX Item "--minor-os-version value"
2024
Sets the minor number of the \*(L"os version\*(R".  Defaults to 0.
2025
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2026
.IP "\fB\-\-minor\-subsystem\-version\fR \fIvalue\fR" 4
2027
.IX Item "--minor-subsystem-version value"
2028
Sets the minor number of the \*(L"subsystem version\*(R".  Defaults to 0.
2029
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2030
.IP "\fB\-\-output\-def\fR \fIfile\fR" 4
2031
.IX Item "--output-def file"
2032
The linker will create the file \fIfile\fR which will contain a \s-1DEF\s0
2033
file corresponding to the \s-1DLL\s0 the linker is generating.  This \s-1DEF\s0 file
2034
(which should be called \f(CW\*(C`*.def\*(C'\fR) may be used to create an import
2035
library with \f(CW\*(C`dlltool\*(C'\fR or may be used as a reference to
2036
automatically or implicitly exported symbols.
2037
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2038
.IP "\fB\-\-out\-implib\fR \fIfile\fR" 4
2039
.IX Item "--out-implib file"
2040
The linker will create the file \fIfile\fR which will contain an
2041
import lib corresponding to the \s-1DLL\s0 the linker is generating. This
2042
import lib (which should be called \f(CW\*(C`*.dll.a\*(C'\fR or \f(CW\*(C`*.a\*(C'\fR
2043
may be used to link clients against the generated \s-1DLL\s0; this behaviour
2044
makes it possible to skip a separate \f(CW\*(C`dlltool\*(C'\fR import library
2045
creation step.
2046
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2047
.IP "\fB\-\-enable\-auto\-image\-base\fR" 4
2048
.IX Item "--enable-auto-image-base"
2049
Automatically choose the image base for DLLs, unless one is specified
2050
using the \f(CW\*(C`\-\-image\-base\*(C'\fR argument.  By using a hash generated
2051
from the dllname to create unique image bases for each \s-1DLL\s0, in-memory
2052
collisions and relocations which can delay program execution are
2053
avoided.
2054
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2055
.IP "\fB\-\-disable\-auto\-image\-base\fR" 4
2056
.IX Item "--disable-auto-image-base"
2057
Do not automatically generate a unique image base.  If there is no
2058
user-specified image base (\f(CW\*(C`\-\-image\-base\*(C'\fR) then use the platform
2059
default.
2060
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2061
.IP "\fB\-\-dll\-search\-prefix\fR \fIstring\fR" 4
2062
.IX Item "--dll-search-prefix string"
2063
When linking dynamically to a dll without an import library,
2064
search for \f(CW\*(C`.dll\*(C'\fR in preference to
2065
\&\f(CW\*(C`lib.dll\*(C'\fR. This behaviour allows easy distinction
2066
between DLLs built for the various \*(L"subplatforms\*(R": native, cygwin,
2067
uwin, pw, etc.  For instance, cygwin DLLs typically use
2068
\&\f(CW\*(C`\-\-dll\-search\-prefix=cyg\*(C'\fR.
2069
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2070
.IP "\fB\-\-enable\-auto\-import\fR" 4
2071
.IX Item "--enable-auto-import"
2072
Do sophisticated linking of \f(CW\*(C`_symbol\*(C'\fR to \f(CW\*(C`_\|_imp_\|_symbol\*(C'\fR for
2073
\&\s-1DATA\s0 imports from DLLs, and create the necessary thunking symbols when
2074
building the import libraries with those \s-1DATA\s0 exports. Note: Use of the
2075
\&'auto\-import' extension will cause the text section of the image file
2076
to be made writable. This does not conform to the PE-COFF format
2077
specification published by Microsoft.
2078
.Sp
2079
Note \- use of the 'auto\-import' extension will also cause read only
2080
data which would normally be placed into the .rdata section to be
2081
placed into the .data section instead.  This is in order to work
2082
around a problem with consts that is described here:
2083
http://www.cygwin.com/ml/cygwin/2004\-09/msg01101.html
2084
.Sp
2085
Using 'auto\-import' generally will 'just work' \*(-- but sometimes you may
2086
see this message:
2087
.Sp
2088
"variable '' can't be auto-imported. Please read the
2089
documentation for ld's \f(CW\*(C`\-\-enable\-auto\-import\*(C'\fR for details."
2090
.Sp
2091
This message occurs when some (sub)expression accesses an address
2092
ultimately given by the sum of two constants (Win32 import tables only
2093
allow one).  Instances where this may occur include accesses to member
2094
fields of struct variables imported from a \s-1DLL\s0, as well as using a
2095
constant index into an array variable imported from a \s-1DLL\s0.  Any
2096
multiword variable (arrays, structs, long long, etc) may trigger
2097
this error condition.  However, regardless of the exact data type
2098
of the offending exported variable, ld will always detect it, issue
2099
the warning, and exit.
2100
.Sp
2101
There are several ways to address this difficulty, regardless of the
2102
data type of the exported variable:
2103
.Sp
2104
One way is to use \-\-enable\-runtime\-pseudo\-reloc switch. This leaves the task
2105
of adjusting references in your client code for runtime environment, so
2106
this method works only when runtime environment supports this feature.
2107
.Sp
2108
A second solution is to force one of the 'constants' to be a variable \*(--
2109
that is, unknown and un-optimizable at compile time.  For arrays,
2110
there are two possibilities: a) make the indexee (the array's address)
2111
a variable, or b) make the 'constant' index a variable.  Thus:
2112
.Sp
2113
.Vb 3
2114
\&        extern type extern_array[];
2115
\&        extern_array[1] \-\->
2116
\&           { volatile type *t=extern_array; t[1] }
2117
.Ve
2118
.Sp
2119
or
2120
.Sp
2121
.Vb 3
2122
\&        extern type extern_array[];
2123
\&        extern_array[1] \-\->
2124
\&           { volatile int t=1; extern_array[t] }
2125
.Ve
2126
.Sp
2127
For structs (and most other multiword data types) the only option
2128
is to make the struct itself (or the long long, or the ...) variable:
2129
.Sp
2130
.Vb 3
2131
\&        extern struct s extern_struct;
2132
\&        extern_struct.field \-\->
2133
\&           { volatile struct s *t=&extern_struct; t\->field }
2134
.Ve
2135
.Sp
2136
or
2137
.Sp
2138
.Vb 3
2139
\&        extern long long extern_ll;
2140
\&        extern_ll \-\->
2141
\&          { volatile long long * local_ll=&extern_ll; *local_ll }
2142
.Ve
2143
.Sp
2144
A third method of dealing with this difficulty is to abandon
2145
\&'auto\-import' for the offending symbol and mark it with
2146
\&\f(CW\*(C`_\|_declspec(dllimport)\*(C'\fR.  However, in practise that
2147
requires using compile-time #defines to indicate whether you are
2148
building a \s-1DLL\s0, building client code that will link to the \s-1DLL\s0, or
2149
merely building/linking to a static library.   In making the choice
2150
between the various methods of resolving the 'direct address with
2151
constant offset' problem, you should consider typical real-world usage:
2152
.Sp
2153
Original:
2154
.Sp
2155
.Vb 7
2156
\&        \-\-foo.h
2157
\&        extern int arr[];
2158
\&        \-\-foo.c
2159
\&        #include "foo.h"
2160
\&        void main(int argc, char **argv){
2161
\&          printf("%d\en",arr[1]);
2162
\&        }
2163
.Ve
2164
.Sp
2165
Solution 1:
2166
.Sp
2167
.Vb 9
2168
\&        \-\-foo.h
2169
\&        extern int arr[];
2170
\&        \-\-foo.c
2171
\&        #include "foo.h"
2172
\&        void main(int argc, char **argv){
2173
\&          /* This workaround is for win32 and cygwin; do not "optimize" */
2174
\&          volatile int *parr = arr;
2175
\&          printf("%d\en",parr[1]);
2176
\&        }
2177
.Ve
2178
.Sp
2179
Solution 2:
2180
.Sp
2181
.Vb 10
2182
\&        \-\-foo.h
2183
\&        /* Note: auto\-export is assumed (no _\|_declspec(dllexport)) */
2184
\&        #if (defined(_WIN32) || defined(_\|_CYGWIN_\|_)) && \e
2185
\&          !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
2186
\&        #define FOO_IMPORT _\|_declspec(dllimport)
2187
\&        #else
2188
\&        #define FOO_IMPORT
2189
\&        #endif
2190
\&        extern FOO_IMPORT int arr[];
2191
\&        \-\-foo.c
2192
\&        #include "foo.h"
2193
\&        void main(int argc, char **argv){
2194
\&          printf("%d\en",arr[1]);
2195
\&        }
2196
.Ve
2197
.Sp
2198
A fourth way to avoid this problem is to re-code your
2199
library to use a functional interface rather than a data interface
2200
for the offending variables (e.g. \fIset_foo()\fR and \fIget_foo()\fR accessor
2201
functions).
2202
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2203
.IP "\fB\-\-disable\-auto\-import\fR" 4
2204
.IX Item "--disable-auto-import"
2205
Do not attempt to do sophisticated linking of \f(CW\*(C`_symbol\*(C'\fR to
2206
\&\f(CW\*(C`_\|_imp_\|_symbol\*(C'\fR for \s-1DATA\s0 imports from DLLs.
2207
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2208
.IP "\fB\-\-enable\-runtime\-pseudo\-reloc\fR" 4
2209
.IX Item "--enable-runtime-pseudo-reloc"
2210
If your code contains expressions described in \-\-enable\-auto\-import section,
2211
that is, \s-1DATA\s0 imports from \s-1DLL\s0 with non-zero offset, this switch will create
2212
a vector of 'runtime pseudo relocations' which can be used by runtime
2213
environment to adjust references to such data in your client code.
2214
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2215
.IP "\fB\-\-disable\-runtime\-pseudo\-reloc\fR" 4
2216
.IX Item "--disable-runtime-pseudo-reloc"
2217
Do not create pseudo relocations for non-zero offset \s-1DATA\s0 imports from
2218
DLLs.  This is the default.
2219
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2220
.IP "\fB\-\-enable\-extra\-pe\-debug\fR" 4
2221
.IX Item "--enable-extra-pe-debug"
2222
Show additional debug info related to auto-import symbol thunking.
2223
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2224
.IP "\fB\-\-section\-alignment\fR" 4
2225
.IX Item "--section-alignment"
2226
Sets the section alignment.  Sections in memory will always begin at
2227
addresses which are a multiple of this number.  Defaults to 0x1000.
2228
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2229
.IP "\fB\-\-stack\fR \fIreserve\fR" 4
2230
.IX Item "--stack reserve"
2231
.PD 0
2232
.IP "\fB\-\-stack\fR \fIreserve\fR\fB,\fR\fIcommit\fR" 4
2233
.IX Item "--stack reserve,commit"
2234
.PD
2235
Specify the number of bytes of memory to reserve (and optionally commit)
2236
to be used as stack for this program.  The default is 2Mb reserved, 4K
2237
committed.
2238
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2239
.IP "\fB\-\-subsystem\fR \fIwhich\fR" 4
2240
.IX Item "--subsystem which"
2241
.PD 0
2242
.IP "\fB\-\-subsystem\fR \fIwhich\fR\fB:\fR\fImajor\fR" 4
2243
.IX Item "--subsystem which:major"
2244
.IP "\fB\-\-subsystem\fR \fIwhich\fR\fB:\fR\fImajor\fR\fB.\fR\fIminor\fR" 4
2245
.IX Item "--subsystem which:major.minor"
2246
.PD
2247
Specifies the subsystem under which your program will execute.  The
2248
legal values for \fIwhich\fR are \f(CW\*(C`native\*(C'\fR, \f(CW\*(C`windows\*(C'\fR,
2249
\&\f(CW\*(C`console\*(C'\fR, \f(CW\*(C`posix\*(C'\fR, and \f(CW\*(C`xbox\*(C'\fR.  You may optionally set
2250
the subsystem version also.  Numeric values are also accepted for
2251
\&\fIwhich\fR.
2252
[This option is specific to the i386 \s-1PE\s0 targeted port of the linker]
2253
.Sp
2254
The following options set flags in the \f(CW\*(C`DllCharacteristics\*(C'\fR field
2255
of the \s-1PE\s0 file header:
2256
[These options are specific to \s-1PE\s0 targeted ports of the linker]
2257
.IP "\fB\-\-dynamicbase\fR" 4
2258
.IX Item "--dynamicbase"
2259
The image base address may be relocated using address space layout
2260
randomization (\s-1ASLR\s0).  This feature was introduced with \s-1MS\s0 Windows
2261
Vista for i386 \s-1PE\s0 targets.
2262
.IP "\fB\-\-forceinteg\fR" 4
2263
.IX Item "--forceinteg"
2264
Code integrity checks are enforced.
2265
.IP "\fB\-\-nxcompat\fR" 4
2266
.IX Item "--nxcompat"
2267
The image is compatible with the Data Execution Prevention.
2268
This feature was introduced with \s-1MS\s0 Windows \s-1XP\s0 \s-1SP2\s0 for i386 \s-1PE\s0 targets.
2269
.IP "\fB\-\-no\-isolation\fR" 4
2270
.IX Item "--no-isolation"
2271
Although the image understands isolation, do not isolate the image.
2272
.IP "\fB\-\-no\-seh\fR" 4
2273
.IX Item "--no-seh"
2274
The image does not use \s-1SEH\s0. No \s-1SE\s0 handler may be called from
2275
this image.
2276
.IP "\fB\-\-no\-bind\fR" 4
2277
.IX Item "--no-bind"
2278
Do not bind this image.
2279
.IP "\fB\-\-wdmdriver\fR" 4
2280
.IX Item "--wdmdriver"
2281
The driver uses the \s-1MS\s0 Windows Driver Model.
2282
.IP "\fB\-\-tsaware\fR" 4
2283
.IX Item "--tsaware"
2284
The image is Terminal Server aware.
2285
.PP
2286
The 68HC11 and 68HC12 linkers support specific options to control the
2287
memory bank switching mapping and trampoline code generation.
2288
.IP "\fB\-\-no\-trampoline\fR" 4
2289
.IX Item "--no-trampoline"
2290
This option disables the generation of trampoline. By default a trampoline
2291
is generated for each far function which is called using a \f(CW\*(C`jsr\*(C'\fR
2292
instruction (this happens when a pointer to a far function is taken).
2293
.IP "\fB\-\-bank\-window\fR \fIname\fR" 4
2294
.IX Item "--bank-window name"
2295
This option indicates to the linker the name of the memory region in
2296
the \fB\s-1MEMORY\s0\fR specification that describes the memory bank window.
2297
The definition of such region is then used by the linker to compute
2298
paging and addresses within the memory window.
2299
.PP
2300
The following options are supported to control handling of \s-1GOT\s0 generation
2301
when linking for 68K targets.
2302
.IP "\fB\-\-got=\fR\fItype\fR" 4
2303
.IX Item "--got=type"
2304
This option tells the linker which \s-1GOT\s0 generation scheme to use.
2305
\&\fItype\fR should be one of \fBsingle\fR, \fBnegative\fR,
2306
\&\fBmultigot\fR or \fBtarget\fR.  For more information refer to the
2307
Info entry for \fIld\fR.
2308
.SH "ENVIRONMENT"
2309
.IX Header "ENVIRONMENT"
2310
You can change the behaviour of \fBld\fR with the environment variables
2311
\&\f(CW\*(C`GNUTARGET\*(C'\fR,
2312
\&\f(CW\*(C`LDEMULATION\*(C'\fR and \f(CW\*(C`COLLECT_NO_DEMANGLE\*(C'\fR.
2313
.PP
2314
\&\f(CW\*(C`GNUTARGET\*(C'\fR determines the input-file object format if you don't
2315
use \fB\-b\fR (or its synonym \fB\-\-format\fR).  Its value should be one
2316
of the \s-1BFD\s0 names for an input format.  If there is no
2317
\&\f(CW\*(C`GNUTARGET\*(C'\fR in the environment, \fBld\fR uses the natural format
2318
of the target. If \f(CW\*(C`GNUTARGET\*(C'\fR is set to \f(CW\*(C`default\*(C'\fR then \s-1BFD\s0
2319
attempts to discover the input format by examining binary input files;
2320
this method often succeeds, but there are potential ambiguities, since
2321
there is no method of ensuring that the magic number used to specify
2322
object-file formats is unique.  However, the configuration procedure for
2323
\&\s-1BFD\s0 on each system places the conventional format for that system first
2324
in the search-list, so ambiguities are resolved in favor of convention.
2325
.PP
2326
\&\f(CW\*(C`LDEMULATION\*(C'\fR determines the default emulation if you don't use the
2327
\&\fB\-m\fR option.  The emulation can affect various aspects of linker
2328
behaviour, particularly the default linker script.  You can list the
2329
available emulations with the \fB\-\-verbose\fR or \fB\-V\fR options.  If
2330
the \fB\-m\fR option is not used, and the \f(CW\*(C`LDEMULATION\*(C'\fR environment
2331
variable is not defined, the default emulation depends upon how the
2332
linker was configured.
2333
.PP
2334
Normally, the linker will default to demangling symbols.  However, if
2335
\&\f(CW\*(C`COLLECT_NO_DEMANGLE\*(C'\fR is set in the environment, then it will
2336
default to not demangling symbols.  This environment variable is used in
2337
a similar fashion by the \f(CW\*(C`gcc\*(C'\fR linker wrapper program.  The default
2338
may be overridden by the \fB\-\-demangle\fR and \fB\-\-no\-demangle\fR
2339
options.
2340
.SH "SEE ALSO"
2341
.IX Header "SEE ALSO"
2342
\&\fIar\fR\|(1), \fInm\fR\|(1), \fIobjcopy\fR\|(1), \fIobjdump\fR\|(1), \fIreadelf\fR\|(1) and
2343
the Info entries for \fIbinutils\fR and
2344
\&\fIld\fR.
2345
.SH "COPYRIGHT"
2346
.IX Header "COPYRIGHT"
2347
Copyright (c) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001,
2348
2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
2349
.PP
2350
Permission is granted to copy, distribute and/or modify this document
2351
under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.3
2352
or any later version published by the Free Software Foundation;
2353
with no Invariant Sections, with no Front-Cover Texts, and with no
2354
Back-Cover Texts.  A copy of the license is included in the
2355
section entitled \*(L"\s-1GNU\s0 Free Documentation License\*(R".

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