1LD(1)                        GNU Development Tools                       LD(1)
2
3
4

NAME

6       ld - The GNU linker
7

SYNOPSIS

9       ld [options] objfile ...
10

DESCRIPTION

12       ld combines a number of object and archive files, relocates their data
13       and ties up symbol references. Usually the last step in compiling a
14       program is to run ld.
15
16       ld accepts Linker Command Language files written in a superset of
17       AT&T's Link Editor Command Language syntax, to provide explicit and
18       total control over the linking process.
19
20       This man page does not describe the command language; see the ld entry
21       in "info" for full details on the command language and on other aspects
22       of the GNU linker.
23
24       This version of ld uses the general purpose BFD libraries to operate on
25       object files. This allows ld to read, combine, and write object files
26       in many different formats---for example, COFF or "a.out".  Different
27       formats may be linked together to produce any available kind of object
28       file.
29
30       Aside from its flexibility, the GNU linker is more helpful than other
31       linkers in providing diagnostic information.  Many linkers abandon
32       execution immediately upon encountering an error; whenever possible, ld
33       continues executing, allowing you to identify other errors (or, in some
34       cases, to get an output file in spite of the error).
35
36       The GNU linker ld is meant to cover a broad range of situations, and to
37       be as compatible as possible with other linkers.  As a result, you have
38       many choices to control its behavior.
39

OPTIONS

41       The linker supports a plethora of command-line options, but in actual
42       practice few of them are used in any particular context.  For instance,
43       a frequent use of ld is to link standard Unix object files on a
44       standard, supported Unix system.  On such a system, to link a file
45       "hello.o":
46
47               ld -o <output> /lib/crt0.o hello.o -lc
48
49       This tells ld to produce a file called output as the result of linking
50       the file "/lib/crt0.o" with "hello.o" and the library "libc.a", which
51       will come from the standard search directories.  (See the discussion of
52       the -l option below.)
53
54       Some of the command-line options to ld may be specified at any point in
55       the command line.  However, options which refer to files, such as -l or
56       -T, cause the file to be read at the point at which the option appears
57       in the command line, relative to the object files and other file
58       options.  Repeating non-file options with a different argument will
59       either have no further effect, or override prior occurrences (those
60       further to the left on the command line) of that option.  Options which
61       may be meaningfully specified more than once are noted in the
62       descriptions below.
63
64       Non-option arguments are object files or archives which are to be
65       linked together.  They may follow, precede, or be mixed in with
66       command-line options, except that an object file argument may not be
67       placed between an option and its argument.
68
69       Usually the linker is invoked with at least one object file, but you
70       can specify other forms of binary input files using -l, -R, and the
71       script command language.  If no binary input files at all are
72       specified, the linker does not produce any output, and issues the
73       message No input files.
74
75       If the linker cannot recognize the format of an object file, it will
76       assume that it is a linker script.  A script specified in this way
77       augments the main linker script used for the link (either the default
78       linker script or the one specified by using -T).  This feature permits
79       the linker to link against a file which appears to be an object or an
80       archive, but actually merely defines some symbol values, or uses
81       "INPUT" or "GROUP" to load other objects.  Specifying a script in this
82       way merely augments the main linker script, with the extra commands
83       placed after the main script; use the -T option to replace the default
84       linker script entirely, but note the effect of the "INSERT" command.
85
86       For options whose names are a single letter, option arguments must
87       either follow the option letter without intervening whitespace, or be
88       given as separate arguments immediately following the option that
89       requires them.
90
91       For options whose names are multiple letters, either one dash or two
92       can precede the option name; for example, -trace-symbol and
93       --trace-symbol are equivalent.  Note---there is one exception to this
94       rule.  Multiple letter options that start with a lower case 'o' can
95       only be preceded by two dashes.  This is to reduce confusion with the
96       -o option.  So for example -omagic sets the output file name to magic
97       whereas --omagic sets the NMAGIC flag on the output.
98
99       Arguments to multiple-letter options must either be separated from the
100       option name by an equals sign, or be given as separate arguments
101       immediately following the option that requires them.  For example,
102       --trace-symbol foo and --trace-symbol=foo are equivalent.  Unique
103       abbreviations of the names of multiple-letter options are accepted.
104
105       Note---if the linker is being invoked indirectly, via a compiler driver
106       (e.g. gcc) then all the linker command line options should be prefixed
107       by -Wl, (or whatever is appropriate for the particular compiler driver)
108       like this:
109
110                 gcc -Wl,--start-group foo.o bar.o -Wl,--end-group
111
112       This is important, because otherwise the compiler driver program may
113       silently drop the linker options, resulting in a bad link.  Confusion
114       may also arise when passing options that require values through a
115       driver, as the use of a space between option and argument acts as a
116       separator, and causes the driver to pass only the option to the linker
117       and the argument to the compiler.  In this case, it is simplest to use
118       the joined forms of both single- and multiple-letter options, such as:
119
120                 gcc foo.o bar.o -Wl,-eENTRY -Wl,-Map=a.map
121
122       Here is a table of the generic command line switches accepted by the
123       GNU linker:
124
125       @file
126           Read command-line options from file.  The options read are inserted
127           in place of the original @file option.  If file does not exist, or
128           cannot be read, then the option will be treated literally, and not
129           removed.
130
131           Options in file are separated by whitespace.  A whitespace
132           character may be included in an option by surrounding the entire
133           option in either single or double quotes.  Any character (including
134           a backslash) may be included by prefixing the character to be
135           included with a backslash.  The file may itself contain additional
136           @file options; any such options will be processed recursively.
137
138       -a keyword
139           This option is supported for HP/UX compatibility.  The keyword
140           argument must be one of the strings archive, shared, or default.
141           -aarchive is functionally equivalent to -Bstatic, and the other two
142           keywords are functionally equivalent to -Bdynamic.  This option may
143           be used any number of times.
144
145       --audit AUDITLIB
146           Adds AUDITLIB to the "DT_AUDIT" entry of the dynamic section.
147           AUDITLIB is not checked for existence, nor will it use the
148           DT_SONAME specified in the library.  If specified multiple times
149           "DT_AUDIT" will contain a colon separated list of audit interfaces
150           to use. If the linker finds an object with an audit entry while
151           searching for shared libraries, it will add a corresponding
152           "DT_DEPAUDIT" entry in the output file.  This option is only
153           meaningful on ELF platforms supporting the rtld-audit interface.
154
155       -A architecture
156       --architecture=architecture
157           In the current release of ld, this option is useful only for the
158           Intel 960 family of architectures.  In that ld configuration, the
159           architecture argument identifies the particular architecture in the
160           960 family, enabling some safeguards and modifying the archive-
161           library search path.
162
163           Future releases of ld may support similar functionality for other
164           architecture families.
165
166       -b input-format
167       --format=input-format
168           ld may be configured to support more than one kind of object file.
169           If your ld is configured this way, you can use the -b option to
170           specify the binary format for input object files that follow this
171           option on the command line.  Even when ld is configured to support
172           alternative object formats, you don't usually need to specify this,
173           as ld should be configured to expect as a default input format the
174           most usual format on each machine.  input-format is a text string,
175           the name of a particular format supported by the BFD libraries.
176           (You can list the available binary formats with objdump -i.)
177
178           You may want to use this option if you are linking files with an
179           unusual binary format.  You can also use -b to switch formats
180           explicitly (when linking object files of different formats), by
181           including -b input-format before each group of object files in a
182           particular format.
183
184           The default format is taken from the environment variable
185           "GNUTARGET".
186
187           You can also define the input format from a script, using the
188           command "TARGET";
189
190       -c MRI-commandfile
191       --mri-script=MRI-commandfile
192           For compatibility with linkers produced by MRI, ld accepts script
193           files written in an alternate, restricted command language,
194           described in the MRI Compatible Script Files section of GNU ld
195           documentation.  Introduce MRI script files with the option -c; use
196           the -T option to run linker scripts written in the general-purpose
197           ld scripting language.  If MRI-cmdfile does not exist, ld looks for
198           it in the directories specified by any -L options.
199
200       -d
201       -dc
202       -dp These three options are equivalent; multiple forms are supported
203           for compatibility with other linkers.  They assign space to common
204           symbols even if a relocatable output file is specified (with -r).
205           The script command "FORCE_COMMON_ALLOCATION" has the same effect.
206
207       --depaudit AUDITLIB
208       -P AUDITLIB
209           Adds AUDITLIB to the "DT_DEPAUDIT" entry of the dynamic section.
210           AUDITLIB is not checked for existence, nor will it use the
211           DT_SONAME specified in the library.  If specified multiple times
212           "DT_DEPAUDIT" will contain a colon separated list of audit
213           interfaces to use.  This option is only meaningful on ELF platforms
214           supporting the rtld-audit interface.  The -P option is provided for
215           Solaris compatibility.
216
217       -e entry
218       --entry=entry
219           Use entry as the explicit symbol for beginning execution of your
220           program, rather than the default entry point.  If there is no
221           symbol named entry, the linker will try to parse entry as a number,
222           and use that as the entry address (the number will be interpreted
223           in base 10; you may use a leading 0x for base 16, or a leading 0
224           for base 8).
225
226       --exclude-libs lib,lib,...
227           Specifies a list of archive libraries from which symbols should not
228           be automatically exported.  The library names may be delimited by
229           commas or colons.  Specifying "--exclude-libs ALL" excludes symbols
230           in all archive libraries from automatic export.  This option is
231           available only for the i386 PE targeted port of the linker and for
232           ELF targeted ports.  For i386 PE, symbols explicitly listed in a
233           .def file are still exported, regardless of this option.  For ELF
234           targeted ports, symbols affected by this option will be treated as
235           hidden.
236
237       --exclude-modules-for-implib module,module,...
238           Specifies a list of object files or archive members, from which
239           symbols should not be automatically exported, but which should be
240           copied wholesale into the import library being generated during the
241           link.  The module names may be delimited by commas or colons, and
242           must match exactly the filenames used by ld to open the files; for
243           archive members, this is simply the member name, but for object
244           files the name listed must include and match precisely any path
245           used to specify the input file on the linker's command-line.  This
246           option is available only for the i386 PE targeted port of the
247           linker.  Symbols explicitly listed in a .def file are still
248           exported, regardless of this option.
249
250       -E
251       --export-dynamic
252       --no-export-dynamic
253           When creating a dynamically linked executable, using the -E option
254           or the --export-dynamic option causes the linker to add all symbols
255           to the dynamic symbol table.  The dynamic symbol table is the set
256           of symbols which are visible from dynamic objects at run time.
257
258           If you do not use either of these options (or use the
259           --no-export-dynamic option to restore the default behavior), the
260           dynamic symbol table will normally contain only those symbols which
261           are referenced by some dynamic object mentioned in the link.
262
263           If you use "dlopen" to load a dynamic object which needs to refer
264           back to the symbols defined by the program, rather than some other
265           dynamic object, then you will probably need to use this option when
266           linking the program itself.
267
268           You can also use the dynamic list to control what symbols should be
269           added to the dynamic symbol table if the output format supports it.
270           See the description of --dynamic-list.
271
272           Note that this option is specific to ELF targeted ports.  PE
273           targets support a similar function to export all symbols from a DLL
274           or EXE; see the description of --export-all-symbols below.
275
276       -EB Link big-endian objects.  This affects the default output format.
277
278       -EL Link little-endian objects.  This affects the default output
279           format.
280
281       -f name
282       --auxiliary=name
283           When creating an ELF shared object, set the internal DT_AUXILIARY
284           field to the specified name.  This tells the dynamic linker that
285           the symbol table of the shared object should be used as an
286           auxiliary filter on the symbol table of the shared object name.
287
288           If you later link a program against this filter object, then, when
289           you run the program, the dynamic linker will see the DT_AUXILIARY
290           field.  If the dynamic linker resolves any symbols from the filter
291           object, it will first check whether there is a definition in the
292           shared object name.  If there is one, it will be used instead of
293           the definition in the filter object.  The shared object name need
294           not exist.  Thus the shared object name may be used to provide an
295           alternative implementation of certain functions, perhaps for
296           debugging or for machine specific performance.
297
298           This option may be specified more than once.  The DT_AUXILIARY
299           entries will be created in the order in which they appear on the
300           command line.
301
302       -F name
303       --filter=name
304           When creating an ELF shared object, set the internal DT_FILTER
305           field to the specified name.  This tells the dynamic linker that
306           the symbol table of the shared object which is being created should
307           be used as a filter on the symbol table of the shared object name.
308
309           If you later link a program against this filter object, then, when
310           you run the program, the dynamic linker will see the DT_FILTER
311           field.  The dynamic linker will resolve symbols according to the
312           symbol table of the filter object as usual, but it will actually
313           link to the definitions found in the shared object name.  Thus the
314           filter object can be used to select a subset of the symbols
315           provided by the object name.
316
317           Some older linkers used the -F option throughout a compilation
318           toolchain for specifying object-file format for both input and
319           output object files.  The GNU linker uses other mechanisms for this
320           purpose: the -b, --format, --oformat options, the "TARGET" command
321           in linker scripts, and the "GNUTARGET" environment variable.  The
322           GNU linker will ignore the -F option when not creating an ELF
323           shared object.
324
325       -fini=name
326           When creating an ELF executable or shared object, call NAME when
327           the executable or shared object is unloaded, by setting DT_FINI to
328           the address of the function.  By default, the linker uses "_fini"
329           as the function to call.
330
331       -g  Ignored.  Provided for compatibility with other tools.
332
333       -G value
334       --gpsize=value
335           Set the maximum size of objects to be optimized using the GP
336           register to size.  This is only meaningful for object file formats
337           such as MIPS ELF that support putting large and small objects into
338           different sections.  This is ignored for other object file formats.
339
340       -h name
341       -soname=name
342           When creating an ELF shared object, set the internal DT_SONAME
343           field to the specified name.  When an executable is linked with a
344           shared object which has a DT_SONAME field, then when the executable
345           is run the dynamic linker will attempt to load the shared object
346           specified by the DT_SONAME field rather than the using the file
347           name given to the linker.
348
349       -i  Perform an incremental link (same as option -r).
350
351       -init=name
352           When creating an ELF executable or shared object, call NAME when
353           the executable or shared object is loaded, by setting DT_INIT to
354           the address of the function.  By default, the linker uses "_init"
355           as the function to call.
356
357       -l namespec
358       --library=namespec
359           Add the archive or object file specified by namespec to the list of
360           files to link.  This option may be used any number of times.  If
361           namespec is of the form :filename, ld will search the library path
362           for a file called filename, otherwise it will search the library
363           path for a file called libnamespec.a.
364
365           On systems which support shared libraries, ld may also search for
366           files other than libnamespec.a.  Specifically, on ELF and SunOS
367           systems, ld will search a directory for a library called
368           libnamespec.so before searching for one called libnamespec.a.  (By
369           convention, a ".so" extension indicates a shared library.)  Note
370           that this behavior does not apply to :filename, which always
371           specifies a file called filename.
372
373           The linker will search an archive only once, at the location where
374           it is specified on the command line.  If the archive defines a
375           symbol which was undefined in some object which appeared before the
376           archive on the command line, the linker will include the
377           appropriate file(s) from the archive.  However, an undefined symbol
378           in an object appearing later on the command line will not cause the
379           linker to search the archive again.
380
381           See the -( option for a way to force the linker to search archives
382           multiple times.
383
384           You may list the same archive multiple times on the command line.
385
386           This type of archive searching is standard for Unix linkers.
387           However, if you are using ld on AIX, note that it is different from
388           the behaviour of the AIX linker.
389
390       -L searchdir
391       --library-path=searchdir
392           Add path searchdir to the list of paths that ld will search for
393           archive libraries and ld control scripts.  You may use this option
394           any number of times.  The directories are searched in the order in
395           which they are specified on the command line.  Directories
396           specified on the command line are searched before the default
397           directories.  All -L options apply to all -l options, regardless of
398           the order in which the options appear.  -L options do not affect
399           how ld searches for a linker script unless -T option is specified.
400
401           If searchdir begins with "=", then the "=" will be replaced by the
402           sysroot prefix, controlled by the --sysroot option, or specified
403           when the linker is configured.
404
405           The default set of paths searched (without being specified with -L)
406           depends on which emulation mode ld is using, and in some cases also
407           on how it was configured.
408
409           The paths can also be specified in a link script with the
410           "SEARCH_DIR" command.  Directories specified this way are searched
411           at the point in which the linker script appears in the command
412           line.
413
414       -m emulation
415           Emulate the emulation linker.  You can list the available
416           emulations with the --verbose or -V options.
417
418           If the -m option is not used, the emulation is taken from the
419           "LDEMULATION" environment variable, if that is defined.
420
421           Otherwise, the default emulation depends upon how the linker was
422           configured.
423
424       -M
425       --print-map
426           Print a link map to the standard output.  A link map provides
427           information about the link, including the following:
428
429           ·   Where object files are mapped into memory.
430
431           ·   How common symbols are allocated.
432
433           ·   All archive members included in the link, with a mention of the
434               symbol which caused the archive member to be brought in.
435
436           ·   The values assigned to symbols.
437
438               Note - symbols whose values are computed by an expression which
439               involves a reference to a previous value of the same symbol may
440               not have correct result displayed in the link map.  This is
441               because the linker discards intermediate results and only
442               retains the final value of an expression.  Under such
443               circumstances the linker will display the final value enclosed
444               by square brackets.  Thus for example a linker script
445               containing:
446
447                          foo = 1
448                          foo = foo * 4
449                          foo = foo + 8
450
451               will produce the following output in the link map if the -M
452               option is used:
453
454                          0x00000001                foo = 0x1
455                          [0x0000000c]                foo = (foo * 0x4)
456                          [0x0000000c]                foo = (foo + 0x8)
457
458               See Expressions for more information about expressions in
459               linker scripts.
460
461       -n
462       --nmagic
463           Turn off page alignment of sections, and disable linking against
464           shared libraries.  If the output format supports Unix style magic
465           numbers, mark the output as "NMAGIC".
466
467       -N
468       --omagic
469           Set the text and data sections to be readable and writable.  Also,
470           do not page-align the data segment, and disable linking against
471           shared libraries.  If the output format supports Unix style magic
472           numbers, mark the output as "OMAGIC". Note: Although a writable
473           text section is allowed for PE-COFF targets, it does not conform to
474           the format specification published by Microsoft.
475
476       --no-omagic
477           This option negates most of the effects of the -N option.  It sets
478           the text section to be read-only, and forces the data segment to be
479           page-aligned.  Note - this option does not enable linking against
480           shared libraries.  Use -Bdynamic for this.
481
482       -o output
483       --output=output
484           Use output as the name for the program produced by ld; if this
485           option is not specified, the name a.out is used by default.  The
486           script command "OUTPUT" can also specify the output file name.
487
488       -O level
489           If level is a numeric values greater than zero ld optimizes the
490           output.  This might take significantly longer and therefore
491           probably should only be enabled for the final binary.  At the
492           moment this option only affects ELF shared library generation.
493           Future releases of the linker may make more use of this option.
494           Also currently there is no difference in the linker's behaviour for
495           different non-zero values of this option.  Again this may change
496           with future releases.
497
498       --push-state
499           The --push-state allows to preserve the current state of the flags
500           which govern the input file handling so that they can all be
501           restored with one corresponding --pop-state option.
502
503           The option which are covered are: -Bdynamic, -Bstatic, -dn, -dy,
504           -call_shared, -non_shared, -static, -N, -n, --whole-archive,
505           --no-whole-archive, -r, -Ur, --copy-dt-needed-entries,
506           --no-copy-dt-needed-entries, --as-needed, --no-as-needed, and -a.
507
508           One target for this option are specifications for pkg-config.  When
509           used with the --libs option all possibly needed libraries are
510           listed and then possibly linked with all the time.  It is better to
511           return something as follows:
512
513                   -Wl,--push-state,--as-needed -libone -libtwo -Wl,--pop-state
514
515           Undoes the effect of --push-state, restores the previous values of
516           the flags governing input file handling.
517
518       -q
519       --emit-relocs
520           Leave relocation sections and contents in fully linked executables.
521           Post link analysis and optimization tools may need this information
522           in order to perform correct modifications of executables.  This
523           results in larger executables.
524
525           This option is currently only supported on ELF platforms.
526
527       --force-dynamic
528           Force the output file to have dynamic sections.  This option is
529           specific to VxWorks targets.
530
531       -r
532       --relocatable
533           Generate relocatable output---i.e., generate an output file that
534           can in turn serve as input to ld.  This is often called partial
535           linking.  As a side effect, in environments that support standard
536           Unix magic numbers, this option also sets the output file's magic
537           number to "OMAGIC".  If this option is not specified, an absolute
538           file is produced.  When linking C++ programs, this option will not
539           resolve references to constructors; to do that, use -Ur.
540
541           When an input file does not have the same format as the output
542           file, partial linking is only supported if that input file does not
543           contain any relocations.  Different output formats can have further
544           restrictions; for example some "a.out"-based formats do not support
545           partial linking with input files in other formats at all.
546
547           This option does the same thing as -i.
548
549       -R filename
550       --just-symbols=filename
551           Read symbol names and their addresses from filename, but do not
552           relocate it or include it in the output.  This allows your output
553           file to refer symbolically to absolute locations of memory defined
554           in other programs.  You may use this option more than once.
555
556           For compatibility with other ELF linkers, if the -R option is
557           followed by a directory name, rather than a file name, it is
558           treated as the -rpath option.
559
560       -s
561       --strip-all
562           Omit all symbol information from the output file.
563
564       -S
565       --strip-debug
566           Omit debugger symbol information (but not all symbols) from the
567           output file.
568
569       -t
570       --trace
571           Print the names of the input files as ld processes them.
572
573       -T scriptfile
574       --script=scriptfile
575           Use scriptfile as the linker script.  This script replaces ld's
576           default linker script (rather than adding to it), so commandfile
577           must specify everything necessary to describe the output file.
578           If scriptfile does not exist in the current directory, "ld" looks
579           for it in the directories specified by any preceding -L options.
580           Multiple -T options accumulate.
581
582       -dT scriptfile
583       --default-script=scriptfile
584           Use scriptfile as the default linker script.
585
586           This option is similar to the --script option except that
587           processing of the script is delayed until after the rest of the
588           command line has been processed.  This allows options placed after
589           the --default-script option on the command line to affect the
590           behaviour of the linker script, which can be important when the
591           linker command line cannot be directly controlled by the user.  (eg
592           because the command line is being constructed by another tool, such
593           as gcc).
594
595       -u symbol
596       --undefined=symbol
597           Force symbol to be entered in the output file as an undefined
598           symbol.  Doing this may, for example, trigger linking of additional
599           modules from standard libraries.  -u may be repeated with different
600           option arguments to enter additional undefined symbols.  This
601           option is equivalent to the "EXTERN" linker script command.
602
603           If this option is being used to force additional modules to be
604           pulled into the link, and if it is an error for the symbol to
605           remain undefined, then the option --require-defined should be used
606           instead.
607
608       --require-defined=symbol
609           Require that symbol is defined in the output file.  This option is
610           the same as option --undefined except that if symbol is not defined
611           in the output file then the linker will issue an error and exit.
612           The same effect can be achieved in a linker script by using
613           "EXTERN", "ASSERT" and "DEFINED" together.  This option can be used
614           multiple times to require additional symbols.
615
616       -Ur For anything other than C++ programs, this option is equivalent to
617           -r: it generates relocatable output---i.e., an output file that can
618           in turn serve as input to ld.  When linking C++ programs, -Ur does
619           resolve references to constructors, unlike -r.  It does not work to
620           use -Ur on files that were themselves linked with -Ur; once the
621           constructor table has been built, it cannot be added to.  Use -Ur
622           only for the last partial link, and -r for the others.
623
624       --orphan-handling=MODE
625           Control how orphan sections are handled.  An orphan section is one
626           not specifically mentioned in a linker script.
627
628           MODE can have any of the following values:
629
630           "place"
631               Orphan sections are placed into a suitable output section
632               following the strategy described in Orphan Sections.  The
633               option --unique also effects how sections are placed.
634
635           "discard"
636               All orphan sections are discarded, by placing them in the
637               /DISCARD/ section.
638
639           "warn"
640               The linker will place the orphan section as for "place" and
641               also issue a warning.
642
643           "error"
644               The linker will exit with an error if any orphan section is
645               found.
646
647           The default if --orphan-handling is not given is "place".
648
649       --unique[=SECTION]
650           Creates a separate output section for every input section matching
651           SECTION, or if the optional wildcard SECTION argument is missing,
652           for every orphan input section.  An orphan section is one not
653           specifically mentioned in a linker script.  You may use this option
654           multiple times on the command line;  It prevents the normal merging
655           of input sections with the same name, overriding output section
656           assignments in a linker script.
657
658       -v
659       --version
660       -V  Display the version number for ld.  The -V option also lists the
661           supported emulations.
662
663       -x
664       --discard-all
665           Delete all local symbols.
666
667       -X
668       --discard-locals
669           Delete all temporary local symbols.  (These symbols start with
670           system-specific local label prefixes, typically .L for ELF systems
671           or L for traditional a.out systems.)
672
673       -y symbol
674       --trace-symbol=symbol
675           Print the name of each linked file in which symbol appears.  This
676           option may be given any number of times.  On many systems it is
677           necessary to prepend an underscore.
678
679           This option is useful when you have an undefined symbol in your
680           link but don't know where the reference is coming from.
681
682       -Y path
683           Add path to the default library search path.  This option exists
684           for Solaris compatibility.
685
686       -z keyword
687           The recognized keywords are:
688
689           combreloc
690               Combines multiple reloc sections and sorts them to make dynamic
691               symbol lookup caching possible.
692
693           defs
694               Disallows undefined symbols in object files.  Undefined symbols
695               in shared libraries are still allowed.
696
697           execstack
698               Marks the object as requiring executable stack.
699
700           global
701               This option is only meaningful when building a shared object.
702               It makes the symbols defined by this shared object available
703               for symbol resolution of subsequently loaded libraries.
704
705           initfirst
706               This option is only meaningful when building a shared object.
707               It marks the object so that its runtime initialization will
708               occur before the runtime initialization of any other objects
709               brought into the process at the same time.  Similarly the
710               runtime finalization of the object will occur after the runtime
711               finalization of any other objects.
712
713           interpose
714               Marks the object that its symbol table interposes before all
715               symbols but the primary executable.
716
717           lazy
718               When generating an executable or shared library, mark it to
719               tell the dynamic linker to defer function call resolution to
720               the point when the function is called (lazy binding), rather
721               than at load time.  Lazy binding is the default.
722
723           loadfltr
724               Marks  the object that its filters be processed immediately at
725               runtime.
726
727           muldefs
728               Allows multiple definitions.
729
730           nocombreloc
731               Disables multiple reloc sections combining.
732
733           nocopyreloc
734               Disable linker generated .dynbss variables used in place of
735               variables defined in shared libraries.  May result in dynamic
736               text relocations.
737
738           nodefaultlib
739               Marks the object that the search for dependencies of this
740               object will ignore any default library search paths.
741
742           nodelete
743               Marks the object shouldn't be unloaded at runtime.
744
745           nodlopen
746               Marks the object not available to "dlopen".
747
748           nodump
749               Marks the object can not be dumped by "dldump".
750
751           noexecstack
752               Marks the object as not requiring executable stack.
753
754           text
755               Treat DT_TEXTREL in shared object as error.
756
757           notext
758               Don't treat DT_TEXTREL in shared object as error.
759
760           textoff
761               Don't treat DT_TEXTREL in shared object as error.
762
763           norelro
764               Don't create an ELF "PT_GNU_RELRO" segment header in the
765               object.
766
767           now When generating an executable or shared library, mark it to
768               tell the dynamic linker to resolve all symbols when the program
769               is started, or when the shared library is linked to using
770               dlopen, instead of deferring function call resolution to the
771               point when the function is first called.
772
773           origin
774               Marks the object may contain $ORIGIN.
775
776           relro
777               Create an ELF "PT_GNU_RELRO" segment header in the object.
778
779           max-page-size=value
780               Set the emulation maximum page size to value.
781
782           common-page-size=value
783               Set the emulation common page size to value.
784
785           stack-size=value
786               Specify a stack size for in an ELF "PT_GNU_STACK" segment.
787               Specifying zero will override any default non-zero sized
788               "PT_GNU_STACK" segment creation.
789
790           bndplt
791               Always generate BND prefix in PLT entries. Supported for
792               Linux/x86_64.
793
794           noextern-protected-data
795               Don't treat protected data symbol as external when building
796               shared library.  This option overrides linker backend default.
797               It can be used to workaround incorrect relocations against
798               protected data symbols generated by compiler.  Updates on
799               protected data symbols by another module aren't visible to the
800               resulting shared library.  Supported for i386 and x86-64.
801
802           call-nop=prefix-addr
803           call-nop=prefix-nop
804           call-nop=suffix-nop
805           call-nop=prefix-byte
806           call-nop=suffix-byte
807               Specify the 1-byte "NOP" padding when transforming indirect
808               call to a locally defined function, foo, via its GOT slot.
809               call-nop=prefix-addr generates "0x67 call foo".
810               call-nop=prefix-nop generates "0x90 call foo".
811               call-nop=suffix-nop generates "call foo 0x90".
812               call-nop=prefix-byte generates "byte call foo".
813               call-nop=suffix-byte generates "call foo byte".  Supported for
814               i386 and x86_64.
815
816           Other keywords are ignored for Solaris compatibility.
817
818       -( archives -)
819       --start-group archives --end-group
820           The archives should be a list of archive files.  They may be either
821           explicit file names, or -l options.
822
823           The specified archives are searched repeatedly until no new
824           undefined references are created.  Normally, an archive is searched
825           only once in the order that it is specified on the command line.
826           If a symbol in that archive is needed to resolve an undefined
827           symbol referred to by an object in an archive that appears later on
828           the command line, the linker would not be able to resolve that
829           reference.  By grouping the archives, they all be searched
830           repeatedly until all possible references are resolved.
831
832           Using this option has a significant performance cost.  It is best
833           to use it only when there are unavoidable circular references
834           between two or more archives.
835
836       --accept-unknown-input-arch
837       --no-accept-unknown-input-arch
838           Tells the linker to accept input files whose architecture cannot be
839           recognised.  The assumption is that the user knows what they are
840           doing and deliberately wants to link in these unknown input files.
841           This was the default behaviour of the linker, before release 2.14.
842           The default behaviour from release 2.14 onwards is to reject such
843           input files, and so the --accept-unknown-input-arch option has been
844           added to restore the old behaviour.
845
846       --as-needed
847       --no-as-needed
848           This option affects ELF DT_NEEDED tags for dynamic libraries
849           mentioned on the command line after the --as-needed option.
850           Normally the linker will add a DT_NEEDED tag for each dynamic
851           library mentioned on the command line, regardless of whether the
852           library is actually needed or not.  --as-needed causes a DT_NEEDED
853           tag to only be emitted for a library that at that point in the link
854           satisfies a non-weak undefined symbol reference from a regular
855           object file or, if the library is not found in the DT_NEEDED lists
856           of other needed libraries, a non-weak undefined symbol reference
857           from another needed dynamic library.  Object files or libraries
858           appearing on the command line after the library in question do not
859           affect whether the library is seen as needed.  This is similar to
860           the rules for extraction of object files from archives.
861           --no-as-needed restores the default behaviour.
862
863       --add-needed
864       --no-add-needed
865           These two options have been deprecated because of the similarity of
866           their names to the --as-needed and --no-as-needed options.  They
867           have been replaced by --copy-dt-needed-entries and
868           --no-copy-dt-needed-entries.
869
870       -assert keyword
871           This option is ignored for SunOS compatibility.
872
873       -Bdynamic
874       -dy
875       -call_shared
876           Link against dynamic libraries.  This is only meaningful on
877           platforms for which shared libraries are supported.  This option is
878           normally the default on such platforms.  The different variants of
879           this option are for compatibility with various systems.  You may
880           use this option multiple times on the command line: it affects
881           library searching for -l options which follow it.
882
883       -Bgroup
884           Set the "DF_1_GROUP" flag in the "DT_FLAGS_1" entry in the dynamic
885           section.  This causes the runtime linker to handle lookups in this
886           object and its dependencies to be performed only inside the group.
887           --unresolved-symbols=report-all is implied.  This option is only
888           meaningful on ELF platforms which support shared libraries.
889
890       -Bstatic
891       -dn
892       -non_shared
893       -static
894           Do not link against shared libraries.  This is only meaningful on
895           platforms for which shared libraries are supported.  The different
896           variants of this option are for compatibility with various systems.
897           You may use this option multiple times on the command line: it
898           affects library searching for -l options which follow it.  This
899           option also implies --unresolved-symbols=report-all.  This option
900           can be used with -shared.  Doing so means that a shared library is
901           being created but that all of the library's external references
902           must be resolved by pulling in entries from static libraries.
903
904       -Bsymbolic
905           When creating a shared library, bind references to global symbols
906           to the definition within the shared library, if any.  Normally, it
907           is possible for a program linked against a shared library to
908           override the definition within the shared library.  This option is
909           only meaningful on ELF platforms which support shared libraries.
910
911       -Bsymbolic-functions
912           When creating a shared library, bind references to global function
913           symbols to the definition within the shared library, if any.  This
914           option is only meaningful on ELF platforms which support shared
915           libraries.
916
917       --dynamic-list=dynamic-list-file
918           Specify the name of a dynamic list file to the linker.  This is
919           typically used when creating shared libraries to specify a list of
920           global symbols whose references shouldn't be bound to the
921           definition within the shared library, or creating dynamically
922           linked executables to specify a list of symbols which should be
923           added to the symbol table in the executable.  This option is only
924           meaningful on ELF platforms which support shared libraries.
925
926           The format of the dynamic list is the same as the version node
927           without scope and node name.  See VERSION for more information.
928
929       --dynamic-list-data
930           Include all global data symbols to the dynamic list.
931
932       --dynamic-list-cpp-new
933           Provide the builtin dynamic list for C++ operator new and delete.
934           It is mainly useful for building shared libstdc++.
935
936       --dynamic-list-cpp-typeinfo
937           Provide the builtin dynamic list for C++ runtime type
938           identification.
939
940       --check-sections
941       --no-check-sections
942           Asks the linker not to check section addresses after they have been
943           assigned to see if there are any overlaps.  Normally the linker
944           will perform this check, and if it finds any overlaps it will
945           produce suitable error messages.  The linker does know about, and
946           does make allowances for sections in overlays.  The default
947           behaviour can be restored by using the command line switch
948           --check-sections.  Section overlap is not usually checked for
949           relocatable links.  You can force checking in that case by using
950           the --check-sections option.
951
952       --copy-dt-needed-entries
953       --no-copy-dt-needed-entries
954           This option affects the treatment of dynamic libraries referred to
955           by DT_NEEDED tags inside ELF dynamic libraries mentioned on the
956           command line.  Normally the linker won't add a DT_NEEDED tag to the
957           output binary for each library mentioned in a DT_NEEDED tag in an
958           input dynamic library.  With --copy-dt-needed-entries specified on
959           the command line however any dynamic libraries that follow it will
960           have their DT_NEEDED entries added.  The default behaviour can be
961           restored with --no-copy-dt-needed-entries.
962
963           This option also has an effect on the resolution of symbols in
964           dynamic libraries.  With --copy-dt-needed-entries dynamic libraries
965           mentioned on the command line will be recursively searched,
966           following their DT_NEEDED tags to other libraries, in order to
967           resolve symbols required by the output binary.  With the default
968           setting however the searching of dynamic libraries that follow it
969           will stop with the dynamic library itself.  No DT_NEEDED links will
970           be traversed to resolve symbols.
971
972       --cref
973           Output a cross reference table.  If a linker map file is being
974           generated, the cross reference table is printed to the map file.
975           Otherwise, it is printed on the standard output.
976
977           The format of the table is intentionally simple, so that it may be
978           easily processed by a script if necessary.  The symbols are printed
979           out, sorted by name.  For each symbol, a list of file names is
980           given.  If the symbol is defined, the first file listed is the
981           location of the definition.  If the symbol is defined as a common
982           value then any files where this happens appear next.  Finally any
983           files that reference the symbol are listed.
984
985       --no-define-common
986           This option inhibits the assignment of addresses to common symbols.
987           The script command "INHIBIT_COMMON_ALLOCATION" has the same effect.
988
989           The --no-define-common option allows decoupling the decision to
990           assign addresses to Common symbols from the choice of the output
991           file type; otherwise a non-Relocatable output type forces assigning
992           addresses to Common symbols.  Using --no-define-common allows
993           Common symbols that are referenced from a shared library to be
994           assigned addresses only in the main program.  This eliminates the
995           unused duplicate space in the shared library, and also prevents any
996           possible confusion over resolving to the wrong duplicate when there
997           are many dynamic modules with specialized search paths for runtime
998           symbol resolution.
999
1000       --defsym=symbol=expression
1001           Create a global symbol in the output file, containing the absolute
1002           address given by expression.  You may use this option as many times
1003           as necessary to define multiple symbols in the command line.  A
1004           limited form of arithmetic is supported for the expression in this
1005           context: you may give a hexadecimal constant or the name of an
1006           existing symbol, or use "+" and "-" to add or subtract hexadecimal
1007           constants or symbols.  If you need more elaborate expressions,
1008           consider using the linker command language from a script.  Note:
1009           there should be no white space between symbol, the equals sign
1010           ("="), and expression.
1011
1012       --demangle[=style]
1013       --no-demangle
1014           These options control whether to demangle symbol names in error
1015           messages and other output.  When the linker is told to demangle, it
1016           tries to present symbol names in a readable fashion: it strips
1017           leading underscores if they are used by the object file format, and
1018           converts C++ mangled symbol names into user readable names.
1019           Different compilers have different mangling styles.  The optional
1020           demangling style argument can be used to choose an appropriate
1021           demangling style for your compiler.  The linker will demangle by
1022           default unless the environment variable COLLECT_NO_DEMANGLE is set.
1023           These options may be used to override the default.
1024
1025       -Ifile
1026       --dynamic-linker=file
1027           Set the name of the dynamic linker.  This is only meaningful when
1028           generating dynamically linked ELF executables.  The default dynamic
1029           linker is normally correct; don't use this unless you know what you
1030           are doing.
1031
1032       --no-dynamic-linker
1033           When producing an executable file, omit the request for a dynamic
1034           linker to be used at load-time.  This is only meaningful for ELF
1035           executables that contain dynamic relocations, and usually requires
1036           entry point code that is capable of processing these relocations.
1037
1038       --fatal-warnings
1039       --no-fatal-warnings
1040           Treat all warnings as errors.  The default behaviour can be
1041           restored with the option --no-fatal-warnings.
1042
1043       --force-exe-suffix
1044           Make sure that an output file has a .exe suffix.
1045
1046           If a successfully built fully linked output file does not have a
1047           ".exe" or ".dll" suffix, this option forces the linker to copy the
1048           output file to one of the same name with a ".exe" suffix. This
1049           option is useful when using unmodified Unix makefiles on a
1050           Microsoft Windows host, since some versions of Windows won't run an
1051           image unless it ends in a ".exe" suffix.
1052
1053       --gc-sections
1054       --no-gc-sections
1055           Enable garbage collection of unused input sections.  It is ignored
1056           on targets that do not support this option.  The default behaviour
1057           (of not performing this garbage collection) can be restored by
1058           specifying --no-gc-sections on the command line.  Note that garbage
1059           collection for COFF and PE format targets is supported, but the
1060           implementation is currently considered to be experimental.
1061
1062           --gc-sections decides which input sections are used by examining
1063           symbols and relocations.  The section containing the entry symbol
1064           and all sections containing symbols undefined on the command-line
1065           will be kept, as will sections containing symbols referenced by
1066           dynamic objects.  Note that when building shared libraries, the
1067           linker must assume that any visible symbol is referenced.  Once
1068           this initial set of sections has been determined, the linker
1069           recursively marks as used any section referenced by their
1070           relocations.  See --entry and --undefined.
1071
1072           This option can be set when doing a partial link (enabled with
1073           option -r).  In this case the root of symbols kept must be
1074           explicitly specified either by an --entry or --undefined option or
1075           by a "ENTRY" command in the linker script.
1076
1077       --print-gc-sections
1078       --no-print-gc-sections
1079           List all sections removed by garbage collection.  The listing is
1080           printed on stderr.  This option is only effective if garbage
1081           collection has been enabled via the --gc-sections) option.  The
1082           default behaviour (of not listing the sections that are removed)
1083           can be restored by specifying --no-print-gc-sections on the command
1084           line.
1085
1086       --print-output-format
1087           Print the name of the default output format (perhaps influenced by
1088           other command-line options).  This is the string that would appear
1089           in an "OUTPUT_FORMAT" linker script command.
1090
1091       --print-memory-usage
1092           Print used size, total size and used size of memory regions created
1093           with the MEMORY command.  This is useful on embedded targets to
1094           have a quick view of amount of free memory.  The format of the
1095           output has one headline and one line per region.  It is both human
1096           readable and easily parsable by tools.  Here is an example of an
1097           output:
1098
1099                   Memory region         Used Size  Region Size  %age Used
1100                                ROM:        256 KB         1 MB     25.00%
1101                                RAM:          32 B         2 GB      0.00%
1102
1103       --help
1104           Print a summary of the command-line options on the standard output
1105           and exit.
1106
1107       --target-help
1108           Print a summary of all target specific options on the standard
1109           output and exit.
1110
1111       -Map=mapfile
1112           Print a link map to the file mapfile.  See the description of the
1113           -M option, above.
1114
1115       --no-keep-memory
1116           ld normally optimizes for speed over memory usage by caching the
1117           symbol tables of input files in memory.  This option tells ld to
1118           instead optimize for memory usage, by rereading the symbol tables
1119           as necessary.  This may be required if ld runs out of memory space
1120           while linking a large executable.
1121
1122       --no-undefined
1123       -z defs
1124           Report unresolved symbol references from regular object files.
1125           This is done even if the linker is creating a non-symbolic shared
1126           library.  The switch --[no-]allow-shlib-undefined controls the
1127           behaviour for reporting unresolved references found in shared
1128           libraries being linked in.
1129
1130       --allow-multiple-definition
1131       -z muldefs
1132           Normally when a symbol is defined multiple times, the linker will
1133           report a fatal error. These options allow multiple definitions and
1134           the first definition will be used.
1135
1136       --allow-shlib-undefined
1137       --no-allow-shlib-undefined
1138           Allows or disallows undefined symbols in shared libraries.  This
1139           switch is similar to --no-undefined except that it determines the
1140           behaviour when the undefined symbols are in a shared library rather
1141           than a regular object file.  It does not affect how undefined
1142           symbols in regular object files are handled.
1143
1144           The default behaviour is to report errors for any undefined symbols
1145           referenced in shared libraries if the linker is being used to
1146           create an executable, but to allow them if the linker is being used
1147           to create a shared library.
1148
1149           The reasons for allowing undefined symbol references in shared
1150           libraries specified at link time are that:
1151
1152           ·   A shared library specified at link time may not be the same as
1153               the one that is available at load time, so the symbol might
1154               actually be resolvable at load time.
1155
1156           ·   There are some operating systems, eg BeOS and HPPA, where
1157               undefined symbols in shared libraries are normal.
1158
1159               The BeOS kernel for example patches shared libraries at load
1160               time to select whichever function is most appropriate for the
1161               current architecture.  This is used, for example, to
1162               dynamically select an appropriate memset function.
1163
1164       --no-undefined-version
1165           Normally when a symbol has an undefined version, the linker will
1166           ignore it. This option disallows symbols with undefined version and
1167           a fatal error will be issued instead.
1168
1169       --default-symver
1170           Create and use a default symbol version (the soname) for
1171           unversioned exported symbols.
1172
1173       --default-imported-symver
1174           Create and use a default symbol version (the soname) for
1175           unversioned imported symbols.
1176
1177       --no-warn-mismatch
1178           Normally ld will give an error if you try to link together input
1179           files that are mismatched for some reason, perhaps because they
1180           have been compiled for different processors or for different
1181           endiannesses.  This option tells ld that it should silently permit
1182           such possible errors.  This option should only be used with care,
1183           in cases when you have taken some special action that ensures that
1184           the linker errors are inappropriate.
1185
1186       --no-warn-search-mismatch
1187           Normally ld will give a warning if it finds an incompatible library
1188           during a library search.  This option silences the warning.
1189
1190       --no-whole-archive
1191           Turn off the effect of the --whole-archive option for subsequent
1192           archive files.
1193
1194       --noinhibit-exec
1195           Retain the executable output file whenever it is still usable.
1196           Normally, the linker will not produce an output file if it
1197           encounters errors during the link process; it exits without writing
1198           an output file when it issues any error whatsoever.
1199
1200       -nostdlib
1201           Only search library directories explicitly specified on the command
1202           line.  Library directories specified in linker scripts (including
1203           linker scripts specified on the command line) are ignored.
1204
1205       --oformat=output-format
1206           ld may be configured to support more than one kind of object file.
1207           If your ld is configured this way, you can use the --oformat option
1208           to specify the binary format for the output object file.  Even when
1209           ld is configured to support alternative object formats, you don't
1210           usually need to specify this, as ld should be configured to produce
1211           as a default output format the most usual format on each machine.
1212           output-format is a text string, the name of a particular format
1213           supported by the BFD libraries.  (You can list the available binary
1214           formats with objdump -i.)  The script command "OUTPUT_FORMAT" can
1215           also specify the output format, but this option overrides it.
1216
1217       -pie
1218       --pic-executable
1219           Create a position independent executable.  This is currently only
1220           supported on ELF platforms.  Position independent executables are
1221           similar to shared libraries in that they are relocated by the
1222           dynamic linker to the virtual address the OS chooses for them
1223           (which can vary between invocations).  Like normal dynamically
1224           linked executables they can be executed and symbols defined in the
1225           executable cannot be overridden by shared libraries.
1226
1227       -qmagic
1228           This option is ignored for Linux compatibility.
1229
1230       -Qy This option is ignored for SVR4 compatibility.
1231
1232       --relax
1233       --no-relax
1234           An option with machine dependent effects.  This option is only
1235           supported on a few targets.
1236
1237           On some platforms the --relax option performs target specific,
1238           global optimizations that become possible when the linker resolves
1239           addressing in the program, such as relaxing address modes,
1240           synthesizing new instructions, selecting shorter version of current
1241           instructions, and combining constant values.
1242
1243           On some platforms these link time global optimizations may make
1244           symbolic debugging of the resulting executable impossible.  This is
1245           known to be the case for the Matsushita MN10200 and MN10300 family
1246           of processors.
1247
1248           On platforms where this is not supported, --relax is accepted, but
1249           ignored.
1250
1251           On platforms where --relax is accepted the option --no-relax can be
1252           used to disable the feature.
1253
1254       --retain-symbols-file=filename
1255           Retain only the symbols listed in the file filename, discarding all
1256           others.  filename is simply a flat file, with one symbol name per
1257           line.  This option is especially useful in environments (such as
1258           VxWorks) where a large global symbol table is accumulated
1259           gradually, to conserve run-time memory.
1260
1261           --retain-symbols-file does not discard undefined symbols, or
1262           symbols needed for relocations.
1263
1264           You may only specify --retain-symbols-file once in the command
1265           line.  It overrides -s and -S.
1266
1267       -rpath=dir
1268           Add a directory to the runtime library search path.  This is used
1269           when linking an ELF executable with shared objects.  All -rpath
1270           arguments are concatenated and passed to the runtime linker, which
1271           uses them to locate shared objects at runtime.  The -rpath option
1272           is also used when locating shared objects which are needed by
1273           shared objects explicitly included in the link; see the description
1274           of the -rpath-link option.  If -rpath is not used when linking an
1275           ELF executable, the contents of the environment variable
1276           "LD_RUN_PATH" will be used if it is defined.
1277
1278           The -rpath option may also be used on SunOS.  By default, on SunOS,
1279           the linker will form a runtime search path out of all the -L
1280           options it is given.  If a -rpath option is used, the runtime
1281           search path will be formed exclusively using the -rpath options,
1282           ignoring the -L options.  This can be useful when using gcc, which
1283           adds many -L options which may be on NFS mounted file systems.
1284
1285           For compatibility with other ELF linkers, if the -R option is
1286           followed by a directory name, rather than a file name, it is
1287           treated as the -rpath option.
1288
1289       -rpath-link=dir
1290           When using ELF or SunOS, one shared library may require another.
1291           This happens when an "ld -shared" link includes a shared library as
1292           one of the input files.
1293
1294           When the linker encounters such a dependency when doing a non-
1295           shared, non-relocatable link, it will automatically try to locate
1296           the required shared library and include it in the link, if it is
1297           not included explicitly.  In such a case, the -rpath-link option
1298           specifies the first set of directories to search.  The -rpath-link
1299           option may specify a sequence of directory names either by
1300           specifying a list of names separated by colons, or by appearing
1301           multiple times.
1302
1303           This option should be used with caution as it overrides the search
1304           path that may have been hard compiled into a shared library. In
1305           such a case it is possible to use unintentionally a different
1306           search path than the runtime linker would do.
1307
1308           The linker uses the following search paths to locate required
1309           shared libraries:
1310
1311           1.  Any directories specified by -rpath-link options.
1312
1313           2.  Any directories specified by -rpath options.  The difference
1314               between -rpath and -rpath-link is that directories specified by
1315               -rpath options are included in the executable and used at
1316               runtime, whereas the -rpath-link option is only effective at
1317               link time. Searching -rpath in this way is only supported by
1318               native linkers and cross linkers which have been configured
1319               with the --with-sysroot option.
1320
1321           3.  On an ELF system, for native linkers, if the -rpath and
1322               -rpath-link options were not used, search the contents of the
1323               environment variable "LD_RUN_PATH".
1324
1325           4.  On SunOS, if the -rpath option was not used, search any
1326               directories specified using -L options.
1327
1328           5.  For a native linker, search the contents of the environment
1329               variable "LD_LIBRARY_PATH".
1330
1331           6.  For a native ELF linker, the directories in "DT_RUNPATH" or
1332               "DT_RPATH" of a shared library are searched for shared
1333               libraries needed by it. The "DT_RPATH" entries are ignored if
1334               "DT_RUNPATH" entries exist.
1335
1336           7.  The default directories, normally /lib and /usr/lib.
1337
1338           8.  For a native linker on an ELF system, if the file
1339               /etc/ld.so.conf exists, the list of directories found in that
1340               file.
1341
1342           If the required shared library is not found, the linker will issue
1343           a warning and continue with the link.
1344
1345       -shared
1346       -Bshareable
1347           Create a shared library.  This is currently only supported on ELF,
1348           XCOFF and SunOS platforms.  On SunOS, the linker will automatically
1349           create a shared library if the -e option is not used and there are
1350           undefined symbols in the link.
1351
1352       --sort-common
1353       --sort-common=ascending
1354       --sort-common=descending
1355           This option tells ld to sort the common symbols by alignment in
1356           ascending or descending order when it places them in the
1357           appropriate output sections.  The symbol alignments considered are
1358           sixteen-byte or larger, eight-byte, four-byte, two-byte, and one-
1359           byte. This is to prevent gaps between symbols due to alignment
1360           constraints.  If no sorting order is specified, then descending
1361           order is assumed.
1362
1363       --sort-section=name
1364           This option will apply "SORT_BY_NAME" to all wildcard section
1365           patterns in the linker script.
1366
1367       --sort-section=alignment
1368           This option will apply "SORT_BY_ALIGNMENT" to all wildcard section
1369           patterns in the linker script.
1370
1371       --split-by-file[=size]
1372           Similar to --split-by-reloc but creates a new output section for
1373           each input file when size is reached.  size defaults to a size of 1
1374           if not given.
1375
1376       --split-by-reloc[=count]
1377           Tries to creates extra sections in the output file so that no
1378           single output section in the file contains more than count
1379           relocations.  This is useful when generating huge relocatable files
1380           for downloading into certain real time kernels with the COFF object
1381           file format; since COFF cannot represent more than 65535
1382           relocations in a single section.  Note that this will fail to work
1383           with object file formats which do not support arbitrary sections.
1384           The linker will not split up individual input sections for
1385           redistribution, so if a single input section contains more than
1386           count relocations one output section will contain that many
1387           relocations.  count defaults to a value of 32768.
1388
1389       --stats
1390           Compute and display statistics about the operation of the linker,
1391           such as execution time and memory usage.
1392
1393       --sysroot=directory
1394           Use directory as the location of the sysroot, overriding the
1395           configure-time default.  This option is only supported by linkers
1396           that were configured using --with-sysroot.
1397
1398       --traditional-format
1399           For some targets, the output of ld is different in some ways from
1400           the output of some existing linker.  This switch requests ld to use
1401           the traditional format instead.
1402
1403           For example, on SunOS, ld combines duplicate entries in the symbol
1404           string table.  This can reduce the size of an output file with full
1405           debugging information by over 30 percent.  Unfortunately, the SunOS
1406           "dbx" program can not read the resulting program ("gdb" has no
1407           trouble).  The --traditional-format switch tells ld to not combine
1408           duplicate entries.
1409
1410       --section-start=sectionname=org
1411           Locate a section in the output file at the absolute address given
1412           by org.  You may use this option as many times as necessary to
1413           locate multiple sections in the command line.  org must be a single
1414           hexadecimal integer; for compatibility with other linkers, you may
1415           omit the leading 0x usually associated with hexadecimal values.
1416           Note: there should be no white space between sectionname, the
1417           equals sign ("="), and org.
1418
1419       -Tbss=org
1420       -Tdata=org
1421       -Ttext=org
1422           Same as --section-start, with ".bss", ".data" or ".text" as the
1423           sectionname.
1424
1425       -Ttext-segment=org
1426           When creating an ELF executable, it will set the address of the
1427           first byte of the text segment.
1428
1429       -Trodata-segment=org
1430           When creating an ELF executable or shared object for a target where
1431           the read-only data is in its own segment separate from the
1432           executable text, it will set the address of the first byte of the
1433           read-only data segment.
1434
1435       -Tldata-segment=org
1436           When creating an ELF executable or shared object for x86-64 medium
1437           memory model, it will set the address of the first byte of the
1438           ldata segment.
1439
1440       --unresolved-symbols=method
1441           Determine how to handle unresolved symbols.  There are four
1442           possible values for method:
1443
1444           ignore-all
1445               Do not report any unresolved symbols.
1446
1447           report-all
1448               Report all unresolved symbols.  This is the default.
1449
1450           ignore-in-object-files
1451               Report unresolved symbols that are contained in shared
1452               libraries, but ignore them if they come from regular object
1453               files.
1454
1455           ignore-in-shared-libs
1456               Report unresolved symbols that come from regular object files,
1457               but ignore them if they come from shared libraries.  This can
1458               be useful when creating a dynamic binary and it is known that
1459               all the shared libraries that it should be referencing are
1460               included on the linker's command line.
1461
1462           The behaviour for shared libraries on their own can also be
1463           controlled by the --[no-]allow-shlib-undefined option.
1464
1465           Normally the linker will generate an error message for each
1466           reported unresolved symbol but the option --warn-unresolved-symbols
1467           can change this to a warning.
1468
1469       --dll-verbose
1470       --verbose[=NUMBER]
1471           Display the version number for ld and list the linker emulations
1472           supported.  Display which input files can and cannot be opened.
1473           Display the linker script being used by the linker. If the optional
1474           NUMBER argument > 1, plugin symbol status will also be displayed.
1475
1476       --version-script=version-scriptfile
1477           Specify the name of a version script to the linker.  This is
1478           typically used when creating shared libraries to specify additional
1479           information about the version hierarchy for the library being
1480           created.  This option is only fully supported on ELF platforms
1481           which support shared libraries; see VERSION.  It is partially
1482           supported on PE platforms, which can use version scripts to filter
1483           symbol visibility in auto-export mode: any symbols marked local in
1484           the version script will not be exported.
1485
1486       --warn-common
1487           Warn when a common symbol is combined with another common symbol or
1488           with a symbol definition.  Unix linkers allow this somewhat sloppy
1489           practice, but linkers on some other operating systems do not.  This
1490           option allows you to find potential problems from combining global
1491           symbols.  Unfortunately, some C libraries use this practice, so you
1492           may get some warnings about symbols in the libraries as well as in
1493           your programs.
1494
1495           There are three kinds of global symbols, illustrated here by C
1496           examples:
1497
1498           int i = 1;
1499               A definition, which goes in the initialized data section of the
1500               output file.
1501
1502           extern int i;
1503               An undefined reference, which does not allocate space.  There
1504               must be either a definition or a common symbol for the variable
1505               somewhere.
1506
1507           int i;
1508               A common symbol.  If there are only (one or more) common
1509               symbols for a variable, it goes in the uninitialized data area
1510               of the output file.  The linker merges multiple common symbols
1511               for the same variable into a single symbol.  If they are of
1512               different sizes, it picks the largest size.  The linker turns a
1513               common symbol into a declaration, if there is a definition of
1514               the same variable.
1515
1516           The --warn-common option can produce five kinds of warnings.  Each
1517           warning consists of a pair of lines: the first describes the symbol
1518           just encountered, and the second describes the previous symbol
1519           encountered with the same name.  One or both of the two symbols
1520           will be a common symbol.
1521
1522           1.  Turning a common symbol into a reference, because there is
1523               already a definition for the symbol.
1524
1525                       <file>(<section>): warning: common of `<symbol>'
1526                          overridden by definition
1527                       <file>(<section>): warning: defined here
1528
1529           2.  Turning a common symbol into a reference, because a later
1530               definition for the symbol is encountered.  This is the same as
1531               the previous case, except that the symbols are encountered in a
1532               different order.
1533
1534                       <file>(<section>): warning: definition of `<symbol>'
1535                          overriding common
1536                       <file>(<section>): warning: common is here
1537
1538           3.  Merging a common symbol with a previous same-sized common
1539               symbol.
1540
1541                       <file>(<section>): warning: multiple common
1542                          of `<symbol>'
1543                       <file>(<section>): warning: previous common is here
1544
1545           4.  Merging a common symbol with a previous larger common symbol.
1546
1547                       <file>(<section>): warning: common of `<symbol>'
1548                          overridden by larger common
1549                       <file>(<section>): warning: larger common is here
1550
1551           5.  Merging a common symbol with a previous smaller common symbol.
1552               This is the same as the previous case, except that the symbols
1553               are encountered in a different order.
1554
1555                       <file>(<section>): warning: common of `<symbol>'
1556                          overriding smaller common
1557                       <file>(<section>): warning: smaller common is here
1558
1559       --warn-constructors
1560           Warn if any global constructors are used.  This is only useful for
1561           a few object file formats.  For formats like COFF or ELF, the
1562           linker can not detect the use of global constructors.
1563
1564       --warn-multiple-gp
1565           Warn if multiple global pointer values are required in the output
1566           file.  This is only meaningful for certain processors, such as the
1567           Alpha.  Specifically, some processors put large-valued constants in
1568           a special section.  A special register (the global pointer) points
1569           into the middle of this section, so that constants can be loaded
1570           efficiently via a base-register relative addressing mode.  Since
1571           the offset in base-register relative mode is fixed and relatively
1572           small (e.g., 16 bits), this limits the maximum size of the constant
1573           pool.  Thus, in large programs, it is often necessary to use
1574           multiple global pointer values in order to be able to address all
1575           possible constants.  This option causes a warning to be issued
1576           whenever this case occurs.
1577
1578       --warn-once
1579           Only warn once for each undefined symbol, rather than once per
1580           module which refers to it.
1581
1582       --warn-section-align
1583           Warn if the address of an output section is changed because of
1584           alignment.  Typically, the alignment will be set by an input
1585           section.  The address will only be changed if it not explicitly
1586           specified; that is, if the "SECTIONS" command does not specify a
1587           start address for the section.
1588
1589       --warn-shared-textrel
1590           Warn if the linker adds a DT_TEXTREL to a shared object.
1591
1592       --warn-alternate-em
1593           Warn if an object has alternate ELF machine code.
1594
1595       --warn-unresolved-symbols
1596           If the linker is going to report an unresolved symbol (see the
1597           option --unresolved-symbols) it will normally generate an error.
1598           This option makes it generate a warning instead.
1599
1600       --error-unresolved-symbols
1601           This restores the linker's default behaviour of generating errors
1602           when it is reporting unresolved symbols.
1603
1604       --whole-archive
1605           For each archive mentioned on the command line after the
1606           --whole-archive option, include every object file in the archive in
1607           the link, rather than searching the archive for the required object
1608           files.  This is normally used to turn an archive file into a shared
1609           library, forcing every object to be included in the resulting
1610           shared library.  This option may be used more than once.
1611
1612           Two notes when using this option from gcc: First, gcc doesn't know
1613           about this option, so you have to use -Wl,-whole-archive.  Second,
1614           don't forget to use -Wl,-no-whole-archive after your list of
1615           archives, because gcc will add its own list of archives to your
1616           link and you may not want this flag to affect those as well.
1617
1618       --wrap=symbol
1619           Use a wrapper function for symbol.  Any undefined reference to
1620           symbol will be resolved to "__wrap_symbol".  Any undefined
1621           reference to "__real_symbol" will be resolved to symbol.
1622
1623           This can be used to provide a wrapper for a system function.  The
1624           wrapper function should be called "__wrap_symbol".  If it wishes to
1625           call the system function, it should call "__real_symbol".
1626
1627           Here is a trivial example:
1628
1629                   void *
1630                   __wrap_malloc (size_t c)
1631                   {
1632                     printf ("malloc called with %zu\n", c);
1633                     return __real_malloc (c);
1634                   }
1635
1636           If you link other code with this file using --wrap malloc, then all
1637           calls to "malloc" will call the function "__wrap_malloc" instead.
1638           The call to "__real_malloc" in "__wrap_malloc" will call the real
1639           "malloc" function.
1640
1641           You may wish to provide a "__real_malloc" function as well, so that
1642           links without the --wrap option will succeed.  If you do this, you
1643           should not put the definition of "__real_malloc" in the same file
1644           as "__wrap_malloc"; if you do, the assembler may resolve the call
1645           before the linker has a chance to wrap it to "malloc".
1646
1647       --eh-frame-hdr
1648           Request creation of ".eh_frame_hdr" section and ELF
1649           "PT_GNU_EH_FRAME" segment header.
1650
1651       --no-ld-generated-unwind-info
1652           Request creation of ".eh_frame" unwind info for linker generated
1653           code sections like PLT.  This option is on by default if linker
1654           generated unwind info is supported.
1655
1656       --enable-new-dtags
1657       --disable-new-dtags
1658           This linker can create the new dynamic tags in ELF. But the older
1659           ELF systems may not understand them. If you specify
1660           --enable-new-dtags, the new dynamic tags will be created as needed
1661           and older dynamic tags will be omitted.  If you specify
1662           --disable-new-dtags, no new dynamic tags will be created. By
1663           default, the new dynamic tags are not created. Note that those
1664           options are only available for ELF systems.
1665
1666       --hash-size=number
1667           Set the default size of the linker's hash tables to a prime number
1668           close to number.  Increasing this value can reduce the length of
1669           time it takes the linker to perform its tasks, at the expense of
1670           increasing the linker's memory requirements.  Similarly reducing
1671           this value can reduce the memory requirements at the expense of
1672           speed.
1673
1674       --hash-style=style
1675           Set the type of linker's hash table(s).  style can be either "sysv"
1676           for classic ELF ".hash" section, "gnu" for new style GNU
1677           ".gnu.hash" section or "both" for both the classic ELF ".hash" and
1678           new style GNU ".gnu.hash" hash tables.  The default is "sysv".
1679
1680       --compress-debug-sections=none
1681       --compress-debug-sections=zlib
1682       --compress-debug-sections=zlib-gnu
1683       --compress-debug-sections=zlib-gabi
1684           On ELF platforms , these options control how DWARF debug sections
1685           are compressed using zlib.  --compress-debug-sections=none doesn't
1686           compress DWARF debug sections.  --compress-debug-sections=zlib-gnu
1687           compresses DWARF debug sections and rename debug section names to
1688           begin with .zdebug instead of .debug.
1689           --compress-debug-sections=zlib and
1690           --compress-debug-sections=zlib-gabi compress DWARF debug sections
1691           with SHF_COMPRESSED from the ELF ABI.  The default behaviour varies
1692           depending upon the target involved and the configure options used
1693           to build the toolchain.  The default can be determined by examing
1694           the output from the linker's --help option.
1695
1696       --reduce-memory-overheads
1697           This option reduces memory requirements at ld runtime, at the
1698           expense of linking speed.  This was introduced to select the old
1699           O(n^2) algorithm for link map file generation, rather than the new
1700           O(n) algorithm which uses about 40% more memory for symbol storage.
1701
1702           Another effect of the switch is to set the default hash table size
1703           to 1021, which again saves memory at the cost of lengthening the
1704           linker's run time.  This is not done however if the --hash-size
1705           switch has been used.
1706
1707           The --reduce-memory-overheads switch may be also be used to enable
1708           other tradeoffs in future versions of the linker.
1709
1710       --build-id
1711       --build-id=style
1712           Request the creation of a ".note.gnu.build-id" ELF note section or
1713           a ".buildid" COFF section.  The contents of the note are unique
1714           bits identifying this linked file.  style can be "uuid" to use 128
1715           random bits, "sha1" to use a 160-bit SHA1 hash on the normative
1716           parts of the output contents, "md5" to use a 128-bit MD5 hash on
1717           the normative parts of the output contents, or "0xhexstring" to use
1718           a chosen bit string specified as an even number of hexadecimal
1719           digits ("-" and ":" characters between digit pairs are ignored).
1720           If style is omitted, "sha1" is used.
1721
1722           The "md5" and "sha1" styles produces an identifier that is always
1723           the same in an identical output file, but will be unique among all
1724           nonidentical output files.  It is not intended to be compared as a
1725           checksum for the file's contents.  A linked file may be changed
1726           later by other tools, but the build ID bit string identifying the
1727           original linked file does not change.
1728
1729           Passing "none" for style disables the setting from any "--build-id"
1730           options earlier on the command line.
1731
1732       The i386 PE linker supports the -shared option, which causes the output
1733       to be a dynamically linked library (DLL) instead of a normal
1734       executable.  You should name the output "*.dll" when you use this
1735       option.  In addition, the linker fully supports the standard "*.def"
1736       files, which may be specified on the linker command line like an object
1737       file (in fact, it should precede archives it exports symbols from, to
1738       ensure that they get linked in, just like a normal object file).
1739
1740       In addition to the options common to all targets, the i386 PE linker
1741       support additional command line options that are specific to the i386
1742       PE target.  Options that take values may be separated from their values
1743       by either a space or an equals sign.
1744
1745       --add-stdcall-alias
1746           If given, symbols with a stdcall suffix (@nn) will be exported as-
1747           is and also with the suffix stripped.  [This option is specific to
1748           the i386 PE targeted port of the linker]
1749
1750       --base-file file
1751           Use file as the name of a file in which to save the base addresses
1752           of all the relocations needed for generating DLLs with dlltool.
1753           [This is an i386 PE specific option]
1754
1755       --dll
1756           Create a DLL instead of a regular executable.  You may also use
1757           -shared or specify a "LIBRARY" in a given ".def" file.  [This
1758           option is specific to the i386 PE targeted port of the linker]
1759
1760       --enable-long-section-names
1761       --disable-long-section-names
1762           The PE variants of the COFF object format add an extension that
1763           permits the use of section names longer than eight characters, the
1764           normal limit for COFF.  By default, these names are only allowed in
1765           object files, as fully-linked executable images do not carry the
1766           COFF string table required to support the longer names.  As a GNU
1767           extension, it is possible to allow their use in executable images
1768           as well, or to (probably pointlessly!)  disallow it in object
1769           files, by using these two options.  Executable images generated
1770           with these long section names are slightly non-standard, carrying
1771           as they do a string table, and may generate confusing output when
1772           examined with non-GNU PE-aware tools, such as file viewers and
1773           dumpers.  However, GDB relies on the use of PE long section names
1774           to find Dwarf-2 debug information sections in an executable image
1775           at runtime, and so if neither option is specified on the command-
1776           line, ld will enable long section names, overriding the default and
1777           technically correct behaviour, when it finds the presence of debug
1778           information while linking an executable image and not stripping
1779           symbols.  [This option is valid for all PE targeted ports of the
1780           linker]
1781
1782       --enable-stdcall-fixup
1783       --disable-stdcall-fixup
1784           If the link finds a symbol that it cannot resolve, it will attempt
1785           to do "fuzzy linking" by looking for another defined symbol that
1786           differs only in the format of the symbol name (cdecl vs stdcall)
1787           and will resolve that symbol by linking to the match.  For example,
1788           the undefined symbol "_foo" might be linked to the function
1789           "_foo@12", or the undefined symbol "_bar@16" might be linked to the
1790           function "_bar".  When the linker does this, it prints a warning,
1791           since it normally should have failed to link, but sometimes import
1792           libraries generated from third-party dlls may need this feature to
1793           be usable.  If you specify --enable-stdcall-fixup, this feature is
1794           fully enabled and warnings are not printed.  If you specify
1795           --disable-stdcall-fixup, this feature is disabled and such
1796           mismatches are considered to be errors.  [This option is specific
1797           to the i386 PE targeted port of the linker]
1798
1799       --leading-underscore
1800       --no-leading-underscore
1801           For most targets default symbol-prefix is an underscore and is
1802           defined in target's description. By this option it is possible to
1803           disable/enable the default underscore symbol-prefix.
1804
1805       --export-all-symbols
1806           If given, all global symbols in the objects used to build a DLL
1807           will be exported by the DLL.  Note that this is the default if
1808           there otherwise wouldn't be any exported symbols.  When symbols are
1809           explicitly exported via DEF files or implicitly exported via
1810           function attributes, the default is to not export anything else
1811           unless this option is given.  Note that the symbols "DllMain@12",
1812           "DllEntryPoint@0", "DllMainCRTStartup@12", and "impure_ptr" will
1813           not be automatically exported.  Also, symbols imported from other
1814           DLLs will not be re-exported, nor will symbols specifying the DLL's
1815           internal layout such as those beginning with "_head_" or ending
1816           with "_iname".  In addition, no symbols from "libgcc", "libstd++",
1817           "libmingw32", or "crtX.o" will be exported.  Symbols whose names
1818           begin with "__rtti_" or "__builtin_" will not be exported, to help
1819           with C++ DLLs.  Finally, there is an extensive list of cygwin-
1820           private symbols that are not exported (obviously, this applies on
1821           when building DLLs for cygwin targets).  These cygwin-excludes are:
1822           "_cygwin_dll_entry@12", "_cygwin_crt0_common@8",
1823           "_cygwin_noncygwin_dll_entry@12", "_fmode", "_impure_ptr",
1824           "cygwin_attach_dll", "cygwin_premain0", "cygwin_premain1",
1825           "cygwin_premain2", "cygwin_premain3", and "environ".  [This option
1826           is specific to the i386 PE targeted port of the linker]
1827
1828       --exclude-symbols symbol,symbol,...
1829           Specifies a list of symbols which should not be automatically
1830           exported.  The symbol names may be delimited by commas or colons.
1831           [This option is specific to the i386 PE targeted port of the
1832           linker]
1833
1834       --exclude-all-symbols
1835           Specifies no symbols should be automatically exported.  [This
1836           option is specific to the i386 PE targeted port of the linker]
1837
1838       --file-alignment
1839           Specify the file alignment.  Sections in the file will always begin
1840           at file offsets which are multiples of this number.  This defaults
1841           to 512.  [This option is specific to the i386 PE targeted port of
1842           the linker]
1843
1844       --heap reserve
1845       --heap reserve,commit
1846           Specify the number of bytes of memory to reserve (and optionally
1847           commit) to be used as heap for this program.  The default is 1MB
1848           reserved, 4K committed.  [This option is specific to the i386 PE
1849           targeted port of the linker]
1850
1851       --image-base value
1852           Use value as the base address of your program or dll.  This is the
1853           lowest memory location that will be used when your program or dll
1854           is loaded.  To reduce the need to relocate and improve performance
1855           of your dlls, each should have a unique base address and not
1856           overlap any other dlls.  The default is 0x400000 for executables,
1857           and 0x10000000 for dlls.  [This option is specific to the i386 PE
1858           targeted port of the linker]
1859
1860       --kill-at
1861           If given, the stdcall suffixes (@nn) will be stripped from symbols
1862           before they are exported.  [This option is specific to the i386 PE
1863           targeted port of the linker]
1864
1865       --large-address-aware
1866           If given, the appropriate bit in the "Characteristics" field of the
1867           COFF header is set to indicate that this executable supports
1868           virtual addresses greater than 2 gigabytes.  This should be used in
1869           conjunction with the /3GB or /USERVA=value megabytes switch in the
1870           "[operating systems]" section of the BOOT.INI.  Otherwise, this bit
1871           has no effect.  [This option is specific to PE targeted ports of
1872           the linker]
1873
1874       --disable-large-address-aware
1875           Reverts the effect of a previous --large-address-aware option.
1876           This is useful if --large-address-aware is always set by the
1877           compiler driver (e.g. Cygwin gcc) and the executable does not
1878           support virtual addresses greater than 2 gigabytes.  [This option
1879           is specific to PE targeted ports of the linker]
1880
1881       --major-image-version value
1882           Sets the major number of the "image version".  Defaults to 1.
1883           [This option is specific to the i386 PE targeted port of the
1884           linker]
1885
1886       --major-os-version value
1887           Sets the major number of the "os version".  Defaults to 4.  [This
1888           option is specific to the i386 PE targeted port of the linker]
1889
1890       --major-subsystem-version value
1891           Sets the major number of the "subsystem version".  Defaults to 4.
1892           [This option is specific to the i386 PE targeted port of the
1893           linker]
1894
1895       --minor-image-version value
1896           Sets the minor number of the "image version".  Defaults to 0.
1897           [This option is specific to the i386 PE targeted port of the
1898           linker]
1899
1900       --minor-os-version value
1901           Sets the minor number of the "os version".  Defaults to 0.  [This
1902           option is specific to the i386 PE targeted port of the linker]
1903
1904       --minor-subsystem-version value
1905           Sets the minor number of the "subsystem version".  Defaults to 0.
1906           [This option is specific to the i386 PE targeted port of the
1907           linker]
1908
1909       --output-def file
1910           The linker will create the file file which will contain a DEF file
1911           corresponding to the DLL the linker is generating.  This DEF file
1912           (which should be called "*.def") may be used to create an import
1913           library with "dlltool" or may be used as a reference to
1914           automatically or implicitly exported symbols.  [This option is
1915           specific to the i386 PE targeted port of the linker]
1916
1917       --out-implib file
1918           The linker will create the file file which will contain an import
1919           lib corresponding to the DLL the linker is generating. This import
1920           lib (which should be called "*.dll.a" or "*.a" may be used to link
1921           clients against the generated DLL; this behaviour makes it possible
1922           to skip a separate "dlltool" import library creation step.  [This
1923           option is specific to the i386 PE targeted port of the linker]
1924
1925       --enable-auto-image-base
1926       --enable-auto-image-base=value
1927           Automatically choose the image base for DLLs, optionally starting
1928           with base value, unless one is specified using the "--image-base"
1929           argument.  By using a hash generated from the dllname to create
1930           unique image bases for each DLL, in-memory collisions and
1931           relocations which can delay program execution are avoided.  [This
1932           option is specific to the i386 PE targeted port of the linker]
1933
1934       --disable-auto-image-base
1935           Do not automatically generate a unique image base.  If there is no
1936           user-specified image base ("--image-base") then use the platform
1937           default.  [This option is specific to the i386 PE targeted port of
1938           the linker]
1939
1940       --dll-search-prefix string
1941           When linking dynamically to a dll without an import library, search
1942           for "<string><basename>.dll" in preference to "lib<basename>.dll".
1943           This behaviour allows easy distinction between DLLs built for the
1944           various "subplatforms": native, cygwin, uwin, pw, etc.  For
1945           instance, cygwin DLLs typically use "--dll-search-prefix=cyg".
1946           [This option is specific to the i386 PE targeted port of the
1947           linker]
1948
1949       --enable-auto-import
1950           Do sophisticated linking of "_symbol" to "__imp__symbol" for DATA
1951           imports from DLLs, and create the necessary thunking symbols when
1952           building the import libraries with those DATA exports. Note: Use of
1953           the 'auto-import' extension will cause the text section of the
1954           image file to be made writable. This does not conform to the PE-
1955           COFF format specification published by Microsoft.
1956
1957           Note - use of the 'auto-import' extension will also cause read only
1958           data which would normally be placed into the .rdata section to be
1959           placed into the .data section instead.  This is in order to work
1960           around a problem with consts that is described here:
1961           http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
1962
1963           Using 'auto-import' generally will 'just work' -- but sometimes you
1964           may see this message:
1965
1966           "variable '<var>' can't be auto-imported. Please read the
1967           documentation for ld's "--enable-auto-import" for details."
1968
1969           This message occurs when some (sub)expression accesses an address
1970           ultimately given by the sum of two constants (Win32 import tables
1971           only allow one).  Instances where this may occur include accesses
1972           to member fields of struct variables imported from a DLL, as well
1973           as using a constant index into an array variable imported from a
1974           DLL.  Any multiword variable (arrays, structs, long long, etc) may
1975           trigger this error condition.  However, regardless of the exact
1976           data type of the offending exported variable, ld will always detect
1977           it, issue the warning, and exit.
1978
1979           There are several ways to address this difficulty, regardless of
1980           the data type of the exported variable:
1981
1982           One way is to use --enable-runtime-pseudo-reloc switch. This leaves
1983           the task of adjusting references in your client code for runtime
1984           environment, so this method works only when runtime environment
1985           supports this feature.
1986
1987           A second solution is to force one of the 'constants' to be a
1988           variable -- that is, unknown and un-optimizable at compile time.
1989           For arrays, there are two possibilities: a) make the indexee (the
1990           array's address) a variable, or b) make the 'constant' index a
1991           variable.  Thus:
1992
1993                   extern type extern_array[];
1994                   extern_array[1] -->
1995                      { volatile type *t=extern_array; t[1] }
1996
1997           or
1998
1999                   extern type extern_array[];
2000                   extern_array[1] -->
2001                      { volatile int t=1; extern_array[t] }
2002
2003           For structs (and most other multiword data types) the only option
2004           is to make the struct itself (or the long long, or the ...)
2005           variable:
2006
2007                   extern struct s extern_struct;
2008                   extern_struct.field -->
2009                      { volatile struct s *t=&extern_struct; t->field }
2010
2011           or
2012
2013                   extern long long extern_ll;
2014                   extern_ll -->
2015                     { volatile long long * local_ll=&extern_ll; *local_ll }
2016
2017           A third method of dealing with this difficulty is to abandon
2018           'auto-import' for the offending symbol and mark it with
2019           "__declspec(dllimport)".  However, in practice that requires using
2020           compile-time #defines to indicate whether you are building a DLL,
2021           building client code that will link to the DLL, or merely
2022           building/linking to a static library.   In making the choice
2023           between the various methods of resolving the 'direct address with
2024           constant offset' problem, you should consider typical real-world
2025           usage:
2026
2027           Original:
2028
2029                   --foo.h
2030                   extern int arr[];
2031                   --foo.c
2032                   #include "foo.h"
2033                   void main(int argc, char **argv){
2034                     printf("%d\n",arr[1]);
2035                   }
2036
2037           Solution 1:
2038
2039                   --foo.h
2040                   extern int arr[];
2041                   --foo.c
2042                   #include "foo.h"
2043                   void main(int argc, char **argv){
2044                     /* This workaround is for win32 and cygwin; do not "optimize" */
2045                     volatile int *parr = arr;
2046                     printf("%d\n",parr[1]);
2047                   }
2048
2049           Solution 2:
2050
2051                   --foo.h
2052                   /* Note: auto-export is assumed (no __declspec(dllexport)) */
2053                   #if (defined(_WIN32) || defined(__CYGWIN__)) && \
2054                     !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
2055                   #define FOO_IMPORT __declspec(dllimport)
2056                   #else
2057                   #define FOO_IMPORT
2058                   #endif
2059                   extern FOO_IMPORT int arr[];
2060                   --foo.c
2061                   #include "foo.h"
2062                   void main(int argc, char **argv){
2063                     printf("%d\n",arr[1]);
2064                   }
2065
2066           A fourth way to avoid this problem is to re-code your library to
2067           use a functional interface rather than a data interface for the
2068           offending variables (e.g. set_foo() and get_foo() accessor
2069           functions).  [This option is specific to the i386 PE targeted port
2070           of the linker]
2071
2072       --disable-auto-import
2073           Do not attempt to do sophisticated linking of "_symbol" to
2074           "__imp__symbol" for DATA imports from DLLs.  [This option is
2075           specific to the i386 PE targeted port of the linker]
2076
2077       --enable-runtime-pseudo-reloc
2078           If your code contains expressions described in --enable-auto-import
2079           section, that is, DATA imports from DLL with non-zero offset, this
2080           switch will create a vector of 'runtime pseudo relocations' which
2081           can be used by runtime environment to adjust references to such
2082           data in your client code.  [This option is specific to the i386 PE
2083           targeted port of the linker]
2084
2085       --disable-runtime-pseudo-reloc
2086           Do not create pseudo relocations for non-zero offset DATA imports
2087           from DLLs.  [This option is specific to the i386 PE targeted port
2088           of the linker]
2089
2090       --enable-extra-pe-debug
2091           Show additional debug info related to auto-import symbol thunking.
2092           [This option is specific to the i386 PE targeted port of the
2093           linker]
2094
2095       --section-alignment
2096           Sets the section alignment.  Sections in memory will always begin
2097           at addresses which are a multiple of this number.  Defaults to
2098           0x1000.  [This option is specific to the i386 PE targeted port of
2099           the linker]
2100
2101       --stack reserve
2102       --stack reserve,commit
2103           Specify the number of bytes of memory to reserve (and optionally
2104           commit) to be used as stack for this program.  The default is 2MB
2105           reserved, 4K committed.  [This option is specific to the i386 PE
2106           targeted port of the linker]
2107
2108       --subsystem which
2109       --subsystem which:major
2110       --subsystem which:major.minor
2111           Specifies the subsystem under which your program will execute.  The
2112           legal values for which are "native", "windows", "console", "posix",
2113           and "xbox".  You may optionally set the subsystem version also.
2114           Numeric values are also accepted for which.  [This option is
2115           specific to the i386 PE targeted port of the linker]
2116
2117           The following options set flags in the "DllCharacteristics" field
2118           of the PE file header: [These options are specific to PE targeted
2119           ports of the linker]
2120
2121       --high-entropy-va
2122           Image is compatible with 64-bit address space layout randomization
2123           (ASLR).
2124
2125       --dynamicbase
2126           The image base address may be relocated using address space layout
2127           randomization (ASLR).  This feature was introduced with MS Windows
2128           Vista for i386 PE targets.
2129
2130       --forceinteg
2131           Code integrity checks are enforced.
2132
2133       --nxcompat
2134           The image is compatible with the Data Execution Prevention.  This
2135           feature was introduced with MS Windows XP SP2 for i386 PE targets.
2136
2137       --no-isolation
2138           Although the image understands isolation, do not isolate the image.
2139
2140       --no-seh
2141           The image does not use SEH. No SE handler may be called from this
2142           image.
2143
2144       --no-bind
2145           Do not bind this image.
2146
2147       --wdmdriver
2148           The driver uses the MS Windows Driver Model.
2149
2150       --tsaware
2151           The image is Terminal Server aware.
2152
2153       --insert-timestamp
2154       --no-insert-timestamp
2155           Insert a real timestamp into the image.  This is the default
2156           behaviour as it matches legacy code and it means that the image
2157           will work with other, proprietary tools.  The problem with this
2158           default is that it will result in slightly different images being
2159           produced each time the same sources are linked.  The option
2160           --no-insert-timestamp can be used to insert a zero value for the
2161           timestamp, this ensuring that binaries produced from identical
2162           sources will compare identically.
2163
2164       The C6X uClinux target uses a binary format called DSBT to support
2165       shared libraries.  Each shared library in the system needs to have a
2166       unique index; all executables use an index of 0.
2167
2168       --dsbt-size size
2169           This option sets the number of entries in the DSBT of the current
2170           executable or shared library to size.  The default is to create a
2171           table with 64 entries.
2172
2173       --dsbt-index index
2174           This option sets the DSBT index of the current executable or shared
2175           library to index.  The default is 0, which is appropriate for
2176           generating executables.  If a shared library is generated with a
2177           DSBT index of 0, the "R_C6000_DSBT_INDEX" relocs are copied into
2178           the output file.
2179
2180           The --no-merge-exidx-entries switch disables the merging of
2181           adjacent exidx entries in frame unwind info.
2182
2183       The 68HC11 and 68HC12 linkers support specific options to control the
2184       memory bank switching mapping and trampoline code generation.
2185
2186       --no-trampoline
2187           This option disables the generation of trampoline. By default a
2188           trampoline is generated for each far function which is called using
2189           a "jsr" instruction (this happens when a pointer to a far function
2190           is taken).
2191
2192       --bank-window name
2193           This option indicates to the linker the name of the memory region
2194           in the MEMORY specification that describes the memory bank window.
2195           The definition of such region is then used by the linker to compute
2196           paging and addresses within the memory window.
2197
2198       The following options are supported to control handling of GOT
2199       generation when linking for 68K targets.
2200
2201       --got=type
2202           This option tells the linker which GOT generation scheme to use.
2203           type should be one of single, negative, multigot or target.  For
2204           more information refer to the Info entry for ld.
2205
2206       The following options are supported to control microMIPS instruction
2207       generation when linking for MIPS targets.
2208
2209       --insn32
2210       --no-insn32
2211           These options control the choice of microMIPS instructions used in
2212           code generated by the linker, such as that in the PLT or lazy
2213           binding stubs, or in relaxation.  If --insn32 is used, then the
2214           linker only uses 32-bit instruction encodings.  By default or if
2215           --no-insn32 is used, all instruction encodings are used, including
2216           16-bit ones where possible.
2217

ENVIRONMENT

2219       You can change the behaviour of ld with the environment variables
2220       "GNUTARGET", "LDEMULATION" and "COLLECT_NO_DEMANGLE".
2221
2222       "GNUTARGET" determines the input-file object format if you don't use -b
2223       (or its synonym --format).  Its value should be one of the BFD names
2224       for an input format.  If there is no "GNUTARGET" in the environment, ld
2225       uses the natural format of the target. If "GNUTARGET" is set to
2226       "default" then BFD attempts to discover the input format by examining
2227       binary input files; this method often succeeds, but there are potential
2228       ambiguities, since there is no method of ensuring that the magic number
2229       used to specify object-file formats is unique.  However, the
2230       configuration procedure for BFD on each system places the conventional
2231       format for that system first in the search-list, so ambiguities are
2232       resolved in favor of convention.
2233
2234       "LDEMULATION" determines the default emulation if you don't use the -m
2235       option.  The emulation can affect various aspects of linker behaviour,
2236       particularly the default linker script.  You can list the available
2237       emulations with the --verbose or -V options.  If the -m option is not
2238       used, and the "LDEMULATION" environment variable is not defined, the
2239       default emulation depends upon how the linker was configured.
2240
2241       Normally, the linker will default to demangling symbols.  However, if
2242       "COLLECT_NO_DEMANGLE" is set in the environment, then it will default
2243       to not demangling symbols.  This environment variable is used in a
2244       similar fashion by the "gcc" linker wrapper program.  The default may
2245       be overridden by the --demangle and --no-demangle options.
2246

SEE ALSO

2248       ar(1), nm(1), objcopy(1), objdump(1), readelf(1) and the Info entries
2249       for binutils and ld.
2250
2252       Copyright (c) 1991-2015 Free Software Foundation, Inc.
2253
2254       Permission is granted to copy, distribute and/or modify this document
2255       under the terms of the GNU Free Documentation License, Version 1.3 or
2256       any later version published by the Free Software Foundation; with no
2257       Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
2258       Texts.  A copy of the license is included in the section entitled "GNU
2259       Free Documentation License".
2260
2261
2262
2263binutils-2.26                     2019-02-02                             LD(1)
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