1 .\" Copyright (c) 1991, 92, 93, 94, 1995 Free Software Foundation
2 .\" See section COPYING for conditions for redistribution
3 .TH ld 1 "17 August 1992" "cygnus support" "GNU Development Tools"
30 .RB "[\|" \-Bstatic "\|]"
31 .RB "[\|" \-Bdynamic "\|]"
32 .RB "[\|" \-Bsymbolic "\|]"
36 .RB "[\|" \-d | \-dc | \-dp\c
39 .RB "[\|" "\-defsym\ "\c
47 .RB "[\|" \-embedded\-relocs "\|]"
52 .RB "[\|" "\-format\ "\c
59 .RB "[\|" \-\-help "\|]"
74 .RB "[\|" \-n | \-N "\|]"
75 .RB "[\|" \-noinhibit-exec "\|]"
76 .RB "[\|" \-no\-keep\-memory "\|]"
77 .RB "[\|" "\-oformat\ "\c
83 .RB "[\|" \-relax "\|]"
84 .RB "[\|" \-r | \-Ur "\|]"
87 .RB "[\|" \-shared "\|]"
88 .RB "[\|" \-sort\-common "\|]"
89 .RB "[\|" \-split\-by\-reloc\ "\c
92 .RB "[\|" \-split\-by\-file "\|]"
96 .RB "[\|" "\-Ttext\ "\c
99 .RB "[\|" "\-Tdata\ "\c
102 .RB "[\|" "\-Tbss\ "\c
111 .RB "[\|" \-\-verbose "\|]"
112 .RB "[\|" \-\-version "\|]"
113 .RB "[\|" \-warn\-common "\|]"
114 .RB "[\|" \-warn\-constructors "\|]"
115 .RB "[\|" \-warn\-once "\|]"
116 .RB "[\|" \-\-whole\-archive "\|]"
124 \& combines a number of object and archive files, relocates
125 their data and ties up symbol references. Often the last step in
126 building a new compiled program to run is a call to \c
132 \& accepts Linker Command Language files
133 to provide explicit and total control over the linking process.
134 This man page does not describe the command language; see the `\|\c
141 \&, for full details on the command language and on other aspects of
146 \& uses the general purpose BFD libraries
147 to operate on object files. This allows \c
149 \& to read, combine, and
150 write object files in many different formats\(em\&for example, COFF or
153 \&. Different formats may be linked together to produce any
154 available kind of object file. You can use `\|\c
156 \|' to get a list of formats supported on various architectures; see
159 Aside from its flexibility, the GNU linker is more helpful than other
160 linkers in providing diagnostic information. Many linkers abandon
161 execution immediately upon encountering an error; whenever possible,
164 \& continues executing, allowing you to identify other errors
165 (or, in some cases, to get an output file in spite of the error).
169 \& is meant to cover a broad range of situations,
170 and to be as compatible as possible with other linkers. As a result,
171 you have many choices to control its behavior through the command line,
172 and through environment variables.
175 The plethora of command-line options may seem intimidating, but in
176 actual practice few of them are used in any particular context.
177 For instance, a frequent use of \c
179 \& is to link standard Unix
180 object files on a standard, supported Unix system. On such a system, to
186 $\ ld\ \-o\ output\ /lib/crt0.o\ hello.o\ \-lc
191 \& to produce a file called \c
194 result of linking the file \c
201 \& which will come from the standard search
204 The command-line options to \c
206 \& may be specified in any order, and
207 may be repeated at will. For the most part, repeating an option with a
208 different argument will either have no further effect, or override prior
209 occurrences (those further to the left on the command line) of an
212 The exceptions\(em\&which may meaningfully be used more than once\(em\&are
217 \& (or its synonym \c
232 The list of object files to be linked together, shown as \c
235 may follow, precede, or be mixed in with command-line options; save that
238 \& argument may not be placed between an option flag and
241 Usually the linker is invoked with at least one object file, but other
242 forms of binary input files can also be specified with \c
247 \&, and the script command language. If \c
250 files at all are specified, the linker does not produce any output, and
251 issues the message `\|\c
255 Option arguments must either follow the option letter without intervening
256 whitespace, or be given as separate arguments immediately following the
257 option that requires them.
260 .BI "-A" "architecture"\c
262 In the current release of \c
264 \&, this option is useful only for the
265 Intel 960 family of architectures. In that \c
267 \& configuration, the
270 \& argument is one of the two-letter names identifying
271 members of the 960 family; the option specifies the desired output
272 target, and warns of any incompatible instructions in the input files.
273 It also modifies the linker's search strategy for archive libraries, to
274 support the use of libraries specific to each particular
275 architecture, by including in the search loop names suffixed with the
276 string identifying the architecture.
278 For example, if your \c
280 \& command line included `\|\c
285 \|', the linker would look (in its built-in search
286 paths, and in any paths you specify with \c
288 \&) for a library with
302 The first two possibilities would be considered in any event; the last
303 two are due to the use of `\|\c
307 Future releases of \c
309 \& may support similar functionality for
310 other architecture families.
312 You can meaningfully use \c
314 \& more than once on a command line, if
315 an architecture family allows combination of target architectures; each
316 use will add another pair of name variants to search for when \c
322 .BI "\-b " "input-format"\c
324 Specify the binary format for input object files that follow this option
325 on the command line. You don't usually need to specify this, as
328 \& is configured to expect as a default input format the most
329 usual format on each machine. \c
331 \& is a text string, the
332 name of a particular format supported by the BFD libraries.
337 \& has the same effect, as does the script command
340 You may want to use this option if you are linking files with an unusual
341 binary format. You can also use \c
343 \& to switch formats explicitly (when
344 linking object files of different formats), by including
349 \& before each group of object files in a
352 The default format is taken from the environment variable
354 \&. You can also define the input
355 format from a script, using the command \c
361 Do not link against shared libraries. This is only meaningful on
362 platforms for which shared libraries are supported.
366 Link against dynamic libraries. This is only meaningful on platforms
367 for which shared libraries are supported. This option is normally the
368 default on such platforms.
372 When creating a shared library, bind references to global symbols to
373 the definition within the shared library, if any. Normally, it is
374 possible for a program linked against a shared library to override the
375 definition within the shared library. This option is only meaningful
376 on ELF platforms which support shared libraries.
379 .BI "\-c " "commandfile"\c
383 \& to read link commands from the file
386 \&. These commands will completely override \c
389 default link format (rather than adding to it); \c
392 specify everything necessary to describe the target format.
395 You may also include a script of link commands directly in the command
396 line by bracketing it between `\|\c
408 These three options are equivalent; multiple forms are supported for
409 compatibility with other linkers. Use any of them to make \c
412 assign space to common symbols even if a relocatable output file is
415 \&). The script command
417 .B FORCE_COMMON_ALLOCATION\c
418 \& has the same effect.
421 .BI "-defsym " "symbol"\c
425 Create a global symbol in the output file, containing the absolute
428 \&. You may use this option as many
429 times as necessary to define multiple symbols in the command line. A
430 limited form of arithmetic is supported for the \c
433 context: you may give a hexadecimal constant or the name of an existing
438 \& to add or subtract hexadecimal
439 constants or symbols. If you need more elaborate expressions, consider
440 using the linker command language from a script.
447 \& as the explicit symbol for beginning execution of your
448 program, rather than the default entry point. for a
449 discussion of defaults and other ways of specifying the
453 .B \-embedded\-relocs
454 This option is only meaningful when linking MIPS embedded PIC code,
457 option to the GNU compiler and assembler. It causes the linker to
458 create a table which may be used at runtime to relocate any data which
459 was statically initialized to pointer values. See the code in
460 testsuite/ld-empic for details.
467 Some older linkers used this option throughout a compilation toolchain
468 for specifying object-file format for both input and output object
471 \&'s mechanisms (the \c
476 for input files, the \c
478 \& command in linker scripts for output
481 \& environment variable) are more flexible, but
482 but it accepts (and ignores) the \c
484 \& option flag for compatibility
485 with scripts written to call the old linker.
488 .BI "\-format " "input\-format"\c
498 Accepted, but ignored; provided for compatibility with other tools.
502 Set the maximum size of objects to be optimized using the GP register
505 under MIPS ECOFF. Ignored for other object file formats.
509 Print a summary of the command-line options on the standard output and exit.
512 begin with two dashes instead of one
513 for compatibility with other GNU programs. The other options start with
514 only one dash for compatibility with other linkers.
518 Perform an incremental link (same as option \c
525 Add an archive file \c
527 \& to the list of files to link. This
528 option may be used any number of times. \c
531 path-list for occurrences of \c
541 .BI "\-L" "searchdir"\c
543 This command adds path \c
545 \& to the list of paths that
548 \& will search for archive libraries. You may use this option
551 The default set of paths searched (without being specified with
554 \&) depends on what emulation mode \c
557 some cases also on how it was configured. The
558 paths can also be specified in a link script with the \c
565 Print (to the standard output file) a link map\(em\&diagnostic information
566 about where symbols are mapped by \c
568 \&, and information on global
569 common storage allocation.
572 .BI "\-Map " "mapfile"\c
575 a link map\(em\&diagnostic information
576 about where symbols are mapped by \c
578 \&, and information on global
579 common storage allocation.
582 .BI "\-m " "emulation"\c
585 linker. You can list the available emulations with the
589 options. This option overrides the compiled-in default, which is the
590 system for which you configured
595 specifies readable and writable \c
600 the output format supports Unix style magic numbers, the output is
605 When you use the `\|\c
607 \&\|' option, the linker does not page-align the
612 sets the text segment to be read only, and \c
619 Normally, the linker will not produce an output file if it encounters
620 errors during the link process. With this flag, you can specify that
621 you wish the output file retained even after non-fatal errors.
624 .B \-no\-keep\-memory
625 The linker normally optimizes for speed over memory usage by caching
626 the symbol tables of input files in memory. This option tells the
627 linker to instead optimize for memory usage, by rereading the symbol
628 tables as necessary. This may be required if the linker runs out of
629 memory space while linking a large executable.
632 .BI "\-o " "output"\c
638 \& is a name for the program produced by \c
641 option is not specified, the name `\|\c
643 \|' is used by default. The
646 \& can also specify the output file name.
649 .BI "\-oformat " "output\-format"\c
651 Specify the binary format for the output object file.
652 You don't usually need to specify this, as
655 \& is configured to produce as a default output format the most
656 usual format on each machine. \c
658 \& is a text string, the
659 name of a particular format supported by the BFD libraries.
662 can also specify the output format, but this option overrides it.
665 .BI "\-R " "filename"\c
669 Read symbol names and their addresses from \c
672 relocate it or include it in the output. This allows your output file
673 to refer symbolically to absolute locations of memory defined in other
678 An option with machine dependent effects. Currently this option is only
679 supported on the H8/300.
681 On some platforms, use this option to perform global optimizations that
682 become possible when the linker resolves addressing in your program, such
683 as relaxing address modes and synthesizing new instructions in the
686 On platforms where this is not supported, `\|\c
688 \&\|' is accepted, but has no effect.
692 Generates relocatable output\(em\&i.e., generate an output file that can in
693 turn serve as input to \c
695 \&. This is often called \c
698 \&. As a side effect, in environments that support standard Unix
699 magic numbers, this option also sets the output file's magic number to
703 If this option is not specified, an absolute file is produced. When
704 linking C++ programs, this option \c
706 \& resolve references to
709 \& is an alternative.
711 This option does the same as \c
717 Omits debugger symbol information (but not all symbols) from the output file.
721 Omits all symbol information from the output file.
725 Create a shared library. This is currently only supported on ELF
732 places the global common symbols in the appropriate output sections,
733 it sorts them by size. First come all the one byte symbols, then all
734 the two bytes, then all the four bytes, and then everything else.
735 This is to prevent gaps between symbols due to
736 alignment constraints. This option disables that sorting.
739 .B \-split\-by\-reloc\ \fIcount
740 Trys to creates extra sections in the output file so that no single
741 output section in the file contains more than
744 This is useful when generating huge relocatable for downloading into
745 certain real time kernels with the COFF object file format; since COFF
746 cannot represent more than 65535 relocations in a single section.
747 Note that this will fail to work with object file formats which do not
748 support arbitrary sections. The linker will not split up individual
749 input sections for redistribution, so if a single input section
752 relocations one output section will contain that many relocations.
757 .B \-split\-by\-reloc
758 but creates a new output section for each input file.
761 .BI "\-Tbss " "org"\c
763 .BI "\-Tdata " "org"\c
765 .BI "\-Ttext " "org"\c
768 \& as the starting address for\(em\&respectively\(em\&the
775 \& segment of the output file.
778 \& must be a hexadecimal integer.
781 .BI "\-T " "commandfile"\c
784 .BI "\-T" "commandfile"\c
789 \&; supported for compatibility with
794 Prints names of input files as \c
802 \& to be entered in the output file as an undefined symbol.
803 This may, for example, trigger linking of additional modules from
804 standard libraries. \c
806 \& may be repeated with different option
807 arguments to enter additional undefined symbols.
811 For anything other than C++ programs, this option is equivalent to
814 \&: it generates relocatable output\(em\&i.e., an output file that can in
815 turn serve as input to \c
817 \&. When linking C++ programs, \c
822 \& resolve references to constructors, unlike \c
828 Display the version number for \c
830 and list the supported emulations.
831 Display which input files can and can not be opened.
835 Display the version number for \c
840 option also lists the supported emulations.
844 Display the version number for \c
850 Warn when a common symbol is combined with another common symbol or with
851 a symbol definition. Unix linkers allow this somewhat sloppy practice,
852 but linkers on some other operating systems do not. This option allows
853 you to find potential problems from combining global symbols.
856 .B \-warn\-constructors
857 Warn if any global constructors are used. This is only useful for a
858 few object file formats. For formats like COFF or ELF, the linker can
859 not detect the use of global constructors.
863 Only warn once for each undefined symbol, rather than once per module
867 .B \-\-whole\-archive
868 For each archive mentioned on the command line, include every object
869 file in the archive in the link, rather than searching the archive for
870 the required object files. This is normally used to turn an archive
871 file into a shared library, forcing every object to be included in the
872 resulting shared library.
876 Delete all temporary local symbols. For most targets, this is all local
877 symbols whose names begin with `\|\c
883 Delete all local symbols.
889 You can change the behavior of
891 \& with the environment variable \c
897 \& determines the input-file object format if you don't
900 \& (or its synonym \c
902 \&). Its value should be one
903 of the BFD names for an input format. If there is no
906 \& in the environment, \c
908 \& uses the natural format
913 \& then BFD attempts to discover the
914 input format by examining binary input files; this method often
915 succeeds, but there are potential ambiguities, since there is no method
916 of ensuring that the magic number used to flag object-file formats is
917 unique. However, the configuration procedure for BFD on each system
918 places the conventional format for that system first in the search-list,
919 so ambiguities are resolved in favor of convention.
928 .RB "`\|" ld "\|' and `\|" binutils "\|'"
934 , Steve Chamberlain and Roland Pesch;
936 The GNU Binary Utilities\c
940 Copyright (c) 1991, 1992 Free Software Foundation, Inc.
942 Permission is granted to make and distribute verbatim copies of
943 this manual provided the copyright notice and this permission notice
944 are preserved on all copies.
946 Permission is granted to copy and distribute modified versions of this
947 manual under the conditions for verbatim copying, provided that the
948 entire resulting derived work is distributed under the terms of a
949 permission notice identical to this one.
951 Permission is granted to copy and distribute translations of this
952 manual into another language, under the above conditions for modified
953 versions, except that this permission notice may be included in
954 translations approved by the Free Software Foundation instead of in
955 the original English.