ld/ld.1

   1 .\" Copyright (c) 1991, 1992 Free Software Foundation
   2 .\" See section COPYING for conditions for redistribution
   3 .TH ld 1 "17 August 1992" "cygnus support" "GNU Development Tools"
   4 .de BP
   5 .sp
   6 .ti \-.2i
   7 \(**
   8 ..
   9
  10 .SH NAME
  11 ld \- the GNU linker
  12
  13 .SH SYNOPSIS
  14 .hy 0
  15 .na
  16 .TP
  17 .B ld
  18 .RB "[\|" \-o "
  19 .I output\c
  20 \&\|] \c
  21 .I objfile\c
  22 \&.\|.\|.
  23 .br
  24 .RB "[\|" \-A\c
  25 .I architecture\c
  26 \&\|]
  27 .RB "[\|" "\-b\ "\c
  28 .I input-format\c
  29 \&\|]
  30 .RB "[\|" \-Bstatic "\|]"
  31 .RB "[\|" "\-c\ "\c
  32 .I commandfile\c
  33 \&\|]
  34 .RB "[\|" \-d | \-dc | \-dp\c
  35 \|]
  36 .br
  37 .RB "[\|" "\-defsym\ "\c
  38 .I symbol\c
  39 \& = \c
  40 .I expression\c
  41 \&\|]
  42 .RB "[\|" "\-e\ "\c
  43 .I entry\c
  44 \&\|]
  45 .RB "[\|" \-embedded\-relocs "\|]"
  46 .RB "[\|" \-F "\|]"
  47 .RB "[\|" "\-F\ "\c
  48 .I format\c
  49 \&\|]
  50 .RB "[\|" "\-format\ "\c
  51 .I input-format\c
  52 \&\|]
  53 .RB "[\|" \-g "\|]"
  54 .RB "[\|" \-G\c
  55 .I size\c
  56 \&\|]
  57 .RB "[\|" \-\-help "\|]"
  58 .RB "[\|" \-i "\|]"
  59 .RB "[\|" \-l\c
  60 .I ar\c
  61 \&\|]
  62 .RB "[\|" \-L\c
  63 .I searchdir\c
  64 \&\|]
  65 .RB "[\|" \-M "\|]"
  66 .RB "[\|" \-Map\c
  67 .I mapfile\c
  68 \&\|]
  69 .RB "[\|" \-m\c
  70 .I emulation\c
  71 \&\|]
  72 .RB "[\|" \-n | \-N "\|]"
  73 .RB "[\|" \-noinhibit-exec "\|]"
  74 .RB "[\|" "\-oformat\ "\c
  75 .I output-format\c
  76 \&\|]
  77 .RB "[\|" "\-R\ "\c
  78 .I filename\c
  79 \&\|]
  80 .RB "[\|" \-relax "\|]"
  81 .RB "[\|" \-r | \-Ur "\|]"
  82 .RB "[\|" \-S "\|]"
  83 .RB "[\|" \-s "\|]"
  84 .RB "[\|" \-sort\-common "\|]"
  85 .RB "[\|" "\-T\ "\c
  86 .I commandfile\c
  87 \&\|]
  88 .RB "[\|" "\-Ttext\ "\c
  89 .I textorg\c
  90 \&\|]
  91 .RB "[\|" "\-Tdata\ "\c
  92 .I dataorg\c
  93 \&\|]
  94 .RB "[\|" "\-Tbss\ "\c
  95 .I bssorg\c
  96 \&\|]
  97 .RB "[\|" \-t "\|]"
  98 .RB "[\|" "\-u\ "\c
  99 .I sym\c
 100 \&]
 101 .RB "[\|" \-V "\|]"
 102 .RB "[\|" \-v "\|]"
 103 .RB "[\|" \-\-verbose "\|]"
 104 .RB "[\|" \-\-version "\|]"
 105 .RB "[\|" \-warn\-common "\|]"
 106 .RB "[\|" \-warn\-once "\|]"
 107 .RB "[\|" \-X "\|]"
 108 .RB "[\|" \-x "\|]"
 109 .ad b
 110 .hy 1
 111 .SH DESCRIPTION
 112 \c
 113 .B ld\c
 114 \& combines a number of object and archive files, relocates
 115 their data and ties up symbol references. Often the last step in
 116 building a new compiled program to run is a call to \c
 117 .B ld\c
 118 \&.
 119
 120 \c
 121 .B ld\c
 122 \& accepts Linker Command Language files
 123 to provide explicit and total control over the linking process.
 124 This man page does not describe the command language; see the `\|\c
 125 .B ld\c
 126 \|' entry in `\|\c
 127 .B info\c
 128 \|', or the manual
 129 .I
 130 ld: the GNU linker
 131 \&, for full details on the command language and on other aspects of
 132 the GNU linker.
 133
 134 This version of \c
 135 .B ld\c
 136 \& uses the general purpose BFD libraries
 137 to operate on object files. This allows \c
 138 .B ld\c
 139 \& to read, combine, and
 140 write object files in many different formats\(em\&for example, COFF or
 141 \c
 142 .B a.out\c
 143 \&.  Different formats may be linked together to produce any
 144 available kind of object file.  You can use `\|\c
 145 .B objdump \-i\c
 146 \|' to get a list of formats supported on various architectures; see
 147 .BR objdump ( 1 ).
 148
 149 Aside from its flexibility, the GNU linker is more helpful than other
 150 linkers in providing diagnostic information.  Many linkers abandon
 151 execution immediately upon encountering an error; whenever possible,
 152 \c
 153 .B ld\c
 154 \& continues executing, allowing you to identify other errors
 155 (or, in some cases, to get an output file in spite of the error).
 156
 157 The GNU linker \c
 158 .B ld\c
 159 \& is meant to cover a broad range of situations,
 160 and to be as compatible as possible with other linkers.  As a result,
 161 you have many choices to control its behavior through the command line,
 162 and through environment variables.
 163
 164 .SH OPTIONS
 165 The plethora of command-line options may seem intimidating, but in
 166 actual practice few of them are used in any particular context.
 167 For instance, a frequent use of \c
 168 .B ld\c
 169 \& is to link standard Unix
 170 object files on a standard, supported Unix system.  On such a system, to
 171 link a file \c
 172 .B hello.o\c
 173 \&:
 174 .sp
 175 .br
 176 $\ ld\ \-o\ output\ /lib/crt0.o\ hello.o\ \-lc
 177 .br
 178 .sp
 179 This tells \c
 180 .B ld\c
 181 \& to produce a file called \c
 182 .B output\c
 183 \& as the
 184 result of linking the file \c
 185 .B /lib/crt0.o\c
 186 \& with \c
 187 .B hello.o\c
 188 \& and
 189 the library \c
 190 .B libc.a\c
 191 \& which will come from the standard search
 192 directories.
 193
 194 The command-line options to \c
 195 .B ld\c
 196 \& may be specified in any order, and
 197 may be repeated at will.  For the most part, repeating an option with a
 198 different argument will either have no further effect, or override prior
 199 occurrences (those further to the left on the command line) of an
 200 option.
 201
 202 The exceptions\(em\&which may meaningfully be used more than once\(em\&are
 203 \c
 204 .B \-A\c
 205 \&, \c
 206 .B \-b\c
 207 \& (or its synonym \c
 208 .B \-format\c
 209 \&), \c
 210 .B \-defsym\c
 211 \&,
 212 \c
 213 .B \-L\c
 214 \&, \c
 215 .B \-l\c
 216 \&, \c
 217 .B \-R\c
 218 \&, and \c
 219 .B \-u\c
 220 \&.
 221
 222 The list of object files to be linked together, shown as \c
 223 .I objfile\c
 224 \&,
 225 may follow, precede, or be mixed in with command-line options; save that
 226 an \c
 227 .I objfile\c
 228 \& argument may not be placed between an option flag and
 229 its argument.
 230
 231 Usually the linker is invoked with at least one object file, but other
 232 forms of binary input files can also be specified with \c
 233 .B \-l\c
 234 \&,
 235 \c
 236 .B \-R\c
 237 \&, and the script command language.  If \c
 238 .I no\c
 239 \& binary input
 240 files at all are specified, the linker does not produce any output, and
 241 issues the message `\|\c
 242 .B No input files\c
 243 \|'.
 244
 245 Option arguments must either follow the option letter without intervening
 246 whitespace, or be given as separate arguments immediately following the
 247 option that requires them.
 248
 249 .TP
 250 .BI "-A" "architecture"\c
 251 \&
 252 In the current release of \c
 253 .B ld\c
 254 \&, this option is useful only for the
 255 Intel 960 family of architectures.  In that \c
 256 .B ld\c
 257 \& configuration, the
 258 \c
 259 .I architecture\c
 260 \& argument is one of the two-letter names identifying
 261 members of the 960 family; the option specifies the desired output
 262 target, and warns of any incompatible instructions in the input files.
 263 It also modifies the linker's search strategy for archive libraries, to
 264 support the use of libraries specific to each particular
 265 architecture, by including in the search loop names suffixed with the
 266 string identifying the architecture.
 267
 268 For example, if your \c
 269 .B ld\c
 270 \& command line included `\|\c
 271 .B \-ACA\c
 272 \|' as
 273 well as `\|\c
 274 .B \-ltry\c
 275 \|', the linker would look (in its built-in search
 276 paths, and in any paths you specify with \c
 277 .B \-L\c
 278 \&) for a library with
 279 the names
 280 .sp
 281 .br
 282 try
 283 .br
 284 libtry.a
 285 .br
 286 tryca
 287 .br
 288 libtryca.a
 289 .br
 290 .sp
 291
 292 The first two possibilities would be considered in any event; the last
 293 two are due to the use of `\|\c
 294 .B \-ACA\c
 295 \|'.
 296
 297 Future releases of \c
 298 .B ld\c
 299 \& may support similar functionality for
 300 other architecture families.
 301
 302 You can meaningfully use \c
 303 .B \-A\c
 304 \& more than once on a command line, if
 305 an architecture family allows combination of target architectures; each
 306 use will add another pair of name variants to search for when \c
 307 .B \-l\c
 308 \&
 309 specifies a library.
 310
 311 .TP
 312 .BI "\-b " "input-format"\c
 313 \&
 314 Specify the binary format for input object files that follow this option
 315 on the command line.  You don't usually need to specify this, as
 316 \c
 317 .B ld\c
 318 \& is configured to expect as a default input format the most
 319 usual format on each machine.  \c
 320 .I input-format\c
 321 \& is a text string, the
 322 name of a particular format supported by the BFD libraries.
 323 \c
 324 .B \-format \c
 325 .I input-format\c
 326 \&\c
 327 \& has the same effect, as does the script command
 328 .BR TARGET .
 329
 330 You may want to use this option if you are linking files with an unusual
 331 binary format.  You can also use \c
 332 .B \-b\c
 333 \& to switch formats explicitly (when
 334 linking object files of different formats), by including
 335 \c
 336 .B \-b \c
 337 .I input-format\c
 338 \&\c
 339 \& before each group of object files in a
 340 particular format.
 341
 342 The default format is taken from the environment variable
 343 .B GNUTARGET\c
 344 \&.  You can also define the input
 345 format from a script, using the command \c
 346 .B TARGET\c
 347 \&.
 348
 349 .TP
 350 .B \-Bstatic
 351 This flag is accepted for command-line compatibility with the SunOS linker,
 352 but has no effect on \c
 353 .B ld\c
 354 \&.
 355
 356 .TP
 357 .BI "\-c " "commandfile"\c
 358 \&
 359 Directs \c
 360 .B ld\c
 361 \& to read link commands from the file
 362 \c
 363 .I commandfile\c
 364 \&.  These commands will completely override \c
 365 .B ld\c
 366 \&'s
 367 default link format (rather than adding to it); \c
 368 .I commandfile\c
 369 \& must
 370 specify everything necessary to describe the target format.
 371
 372
 373 You may also include a script of link commands directly in the command
 374 line by bracketing it between `\|\c
 375 .B {\c
 376 \|' and `\|\c
 377 .B }\c
 378 \|' characters.
 379
 380 .TP
 381 .B \-d
 382 .TP
 383 .B \-dc
 384 .TP
 385 .B \-dp
 386 These three options are equivalent; multiple forms are supported for
 387 compatibility with other linkers.  Use any of them to make \c
 388 .B ld\c
 389 \&
 390 assign space to common symbols even if a relocatable output file is
 391 specified (\c
 392 .B \-r\c
 393 \&).  The script command
 394 \c
 395 .B FORCE_COMMON_ALLOCATION\c
 396 \& has the same effect.
 397
 398 .TP
 399 .BI "-defsym " "symbol"\c
 400 \& = \c
 401 .I expression\c
 402 \&
 403 Create a global symbol in the output file, containing the absolute
 404 address given by \c
 405 .I expression\c
 406 \&.  You may use this option as many
 407 times as necessary to define multiple symbols in the command line.  A
 408 limited form of arithmetic is supported for the \c
 409 .I expression\c
 410 \& in this
 411 context: you may give a hexadecimal constant or the name of an existing
 412 symbol, or use \c
 413 .B +\c
 414 \& and \c
 415 .B \-\c
 416 \& to add or subtract hexadecimal
 417 constants or symbols.  If you need more elaborate expressions, consider
 418 using the linker command language from a script.
 419
 420 .TP
 421 .BI "-e " "entry"\c
 422 \&
 423 Use \c
 424 .I entry\c
 425 \& as the explicit symbol for beginning execution of your
 426 program, rather than the default entry point.  for a
 427 discussion of defaults and other ways of specifying the
 428 entry point.
 429
 430 .TP
 431 .B \-embedded\-relocs
 432 This option is only meaningful when linking MIPS embedded PIC code,
 433 generated by the
 434 .B \-membedded\-pic
 435 option to the GNU compiler and assembler.  It causes the linker to
 436 create a table which may be used at runtime to relocate any data which
 437 was statically initialized to pointer values.  See the code in
 438 testsuite/ld-empic for details.
 439
 440 .TP
 441 .B \-F
 442 .TP
 443 .BI "-F" "format"\c
 444 \&
 445 Some older linkers used this option throughout a compilation toolchain
 446 for specifying object-file format for both input and output object
 447 files.  \c
 448 .B ld\c
 449 \&'s mechanisms (the \c
 450 .B \-b\c
 451 \& or \c
 452 .B \-format\c
 453 \& options
 454 for input files, the \c
 455 .B TARGET\c
 456 \& command in linker scripts for output
 457 files, the \c
 458 .B GNUTARGET\c
 459 \& environment variable) are more flexible, but
 460 but it accepts (and ignores) the \c
 461 .B \-F\c
 462 \& option flag for compatibility
 463 with scripts written to call the old linker.
 464
 465 .TP
 466 .BI "\-format " "input\-format"\c
 467 \&
 468 Synonym for \c
 469 .B \-b\c
 470 \& \c
 471 .I input\-format\c
 472 \&.
 473
 474 .TP
 475 .B \-g
 476 Accepted, but ignored; provided for compatibility with other tools.
 477
 478 .TP
 479 .BI "\-G " "size"\c
 480 Set the maximum size of objects to be optimized using the GP register
 481 to
 482 .I size
 483 under MIPS ECOFF.  Ignored for other object file formats.
 484
 485 .TP
 486 .B \-\-help
 487 Print a summary of the command-line options on the standard output and exit.
 488 This option and
 489 .B \-\-version
 490 begin with two dashes instead of one
 491 for compatibility with other GNU programs.  The other options start with
 492 only one dash for compatibility with other linkers.
 493
 494 .TP
 495 .B \-i
 496 Perform an incremental link (same as option \c
 497 .B \-r\c
 498 \&).
 499
 500 .TP
 501 .BI "\-l" "ar"\c
 502 \&
 503 Add an archive file \c
 504 .I ar\c
 505 \& to the list of files to link.  This
 506 option may be used any number of times.  \c
 507 .B ld\c
 508 \& will search its
 509 path-list for occurrences of \c
 510 .B lib\c
 511 .I ar\c
 512 \&.a\c
 513 \& for every \c
 514 .I ar\c
 515 \&
 516 specified.
 517
 518 .TP
 519 .BI "\-L" "searchdir"\c
 520 \&
 521 This command adds path \c
 522 .I searchdir\c
 523 \& to the list of paths that
 524 \c
 525 .B ld\c
 526 \& will search for archive libraries.  You may use this option
 527 any number of times.
 528
 529 The default set of paths searched (without being specified with
 530 \c
 531 .B \-L\c
 532 \&) depends on what emulation mode \c
 533 .B ld\c
 534 \& is using, and in
 535 some cases also on how it was configured.    The
 536 paths can also be specified in a link script with the \c
 537 .B SEARCH_DIR\c
 538 \&
 539 command.
 540
 541 .TP
 542 .B \-M
 543 Print (to the standard output file) a link map\(em\&diagnostic information
 544 about where symbols are mapped by \c
 545 .B ld\c
 546 \&, and information on global
 547 common storage allocation.
 548
 549 .TP
 550 .BI "\-Map " "mapfile"\c
 551 Print to the file
 552 .I mapfile
 553 a link map\(em\&diagnostic information
 554 about where symbols are mapped by \c
 555 .B ld\c
 556 \&, and information on global
 557 common storage allocation.
 558
 559 .TP
 560 .BI "\-m " "emulation"\c
 561 Emulate the
 562 .I emulation
 563 linker.  You can list the available emulations with the
 564 .I \-\-verbose
 565 or
 566 .I \-V
 567 options.  This option overrides the compiled-in default, which is the
 568 system for which you configured
 569 .BR ld .
 570
 571 .TP
 572 .B \-N
 573 specifies readable and writable \c
 574 .B text\c
 575 \& and \c
 576 .B data\c
 577 \& sections. If
 578 the output format supports Unix style magic numbers, the output is
 579 marked as \c
 580 .B OMAGIC\c
 581 \&.
 582
 583 When you use the `\|\c
 584 .B \-N\c
 585 \&\|' option, the linker does not page-align the
 586 data segment.
 587
 588 .TP
 589 .B \-n
 590 sets the text segment to be read only, and \c
 591 .B NMAGIC\c
 592 \& is written
 593 if possible.
 594
 595 .TP
 596 .B \-noinhibit\-exec
 597 Normally, the linker will not produce an output file if it encounters
 598 errors during the link process.  With this flag, you can specify that
 599 you wish the output file retained even after non-fatal errors.
 600
 601 .TP
 602 .BI "\-o " "output"\c
 603 \&
 604 .I output\c
 605 \&
 606 \c
 607 .I output\c
 608 \& is a name for the program produced by \c
 609 .B ld\c
 610 \&; if this
 611 option is not specified, the name `\|\c
 612 .B a.out\c
 613 \|' is used by default.  The
 614 script command \c
 615 .B OUTPUT\c
 616 \& can also specify the output file name.
 617
 618 .TP
 619 .BI "\-oformat " "output\-format"\c
 620 \&
 621 Specify the binary format for the output object file.
 622 You don't usually need to specify this, as
 623 \c
 624 .B ld\c
 625 \& is configured to produce as a default output format the most
 626 usual format on each machine.  \c
 627 .I output-format\c
 628 \& is a text string, the
 629 name of a particular format supported by the BFD libraries.
 630 The script command
 631 .B OUTPUT_FORMAT
 632 can also specify the output format, but this option overrides it.
 633
 634 .TP
 635 .BI "\-R " "filename"\c
 636 \&
 637 .I file\c
 638 \&
 639 Read symbol names and their addresses from \c
 640 .I filename\c
 641 \&, but do not
 642 relocate it or include it in the output.  This allows your output file
 643 to refer symbolically to absolute locations of memory defined in other
 644 programs.
 645
 646 .TP
 647 .B \-relax
 648 An option with machine dependent effects.  Currently this option is only
 649 supported on the H8/300.
 650
 651 On some platforms, use this option to perform global optimizations that
 652 become possible when the linker resolves addressing in your program, such
 653 as relaxing address modes and synthesizing new instructions in the
 654 output object file.
 655
 656 On platforms where this is not supported, `\|\c
 657 .B \-relax\c
 658 \&\|' is accepted, but has no effect.
 659
 660 .TP
 661 .B \-r
 662 Generates relocatable output\(em\&i.e., generate an output file that can in
 663 turn serve as input to \c
 664 .B ld\c
 665 \&.  This is often called \c
 666 .I partial
 667 linking\c
 668 \&.  As a side effect, in environments that support standard Unix
 669 magic numbers, this option also sets the output file's magic number to
 670 \c
 671 .B OMAGIC\c
 672 \&.
 673 If this option is not specified, an absolute file is produced.  When
 674 linking C++ programs, this option \c
 675 .I will not\c
 676 \& resolve references to
 677 constructors; \c
 678 .B \-Ur\c
 679 \& is an alternative.
 680
 681 This option does the same as \c
 682 .B \-i\c
 683 \&.
 684
 685 .TP
 686 .B \-S
 687 Omits debugger symbol information (but not all symbols) from the output file.
 688
 689 .TP
 690 .B \-s
 691 Omits all symbol information from the output file.
 692
 693 .TP
 694 .B \-sort\-common
 695 Normally, when
 696 .B ld
 697 places the global common symbols in the appropriate output sections,
 698 it sorts them by size.  First come all the one byte symbols, then all
 699 the two bytes, then all the four bytes, and then everything else.
 700 This is to prevent gaps between symbols due to
 701 alignment constraints.  This option disables that sorting.
 702
 703 .TP
 704 .BI "\-Tbss " "org"\c
 705 .TP
 706 .BI "\-Tdata " "org"\c
 707 .TP
 708 .BI "\-Ttext " "org"\c
 709 Use \c
 710 .I org\c
 711 \& as the starting address for\(em\&respectively\(em\&the
 712 \c
 713 .B bss\c
 714 \&, \c
 715 .B data\c
 716 \&, or the \c
 717 .B text\c
 718 \& segment of the output file.
 719 \c
 720 .I textorg\c
 721 \& must be a hexadecimal integer.
 722
 723 .TP
 724 .BI "\-T " "commandfile"\c
 725 \&
 726 .TP
 727 .BI "\-T" "commandfile"\c
 728 Equivalent to \c
 729 .B \-c \c
 730 .I commandfile\c
 731 \&\c
 732 \&; supported for compatibility with
 733 other tools.
 734
 735 .TP
 736 .B \-t
 737 Prints names of input files as \c
 738 .B ld\c
 739 \& processes them.
 740
 741 .TP
 742 .BI "\-u " "sym"
 743 Forces \c
 744 .I sym\c
 745 \& to be entered in the output file as an undefined symbol.
 746 This may, for example, trigger linking of additional modules from
 747 standard libraries.  \c
 748 .B \-u\c
 749 \& may be repeated with different option
 750 arguments to enter additional undefined symbols.
 751
 752 .TP
 753 .B \-Ur
 754 For anything other than C++ programs, this option is equivalent to
 755 \c
 756 .B \-r\c
 757 \&: it generates relocatable output\(em\&i.e., an output file that can in
 758 turn serve as input to \c
 759 .B ld\c
 760 \&.  When linking C++ programs, \c
 761 .B \-Ur\c
 762 \&
 763 \c
 764 .I will\c
 765 \& resolve references to constructors, unlike \c
 766 .B \-r\c
 767 \&.
 768
 769 .TP
 770 .B \-\-verbose
 771 Display the version number for \c
 772 .B ld
 773 and list the supported emulations.
 774 Display which input files can and can not be opened.
 775
 776 .TP
 777 .B \-v, \-V
 778 Display the version number for \c
 779 .B ld\c
 780 \&.
 781 The
 782 .B \-V
 783 option also lists the supported emulations.
 784
 785 .TP
 786 .B \-\-version
 787 Display the version number for \c
 788 .B ld
 789 and exit.
 790
 791 .TP
 792 .B \-warn\-common
 793 Warn when a common symbol is combined with another common symbol or with
 794 a symbol definition.  Unix linkers allow this somewhat sloppy practice,
 795 but linkers on some other operating systems do not.  This option allows
 796 you to find potential problems from combining global symbols.
 797
 798 .TP
 799 .B \-warn\-once
 800 Only warn once for each undefined symbol, rather than once per module
 801 which refers to it.
 802
 803 .TP
 804 .B \-X
 805 If \c
 806 .B \-s\c
 807 \& or \c
 808 .B \-S\c
 809 \& is also specified, delete only local symbols
 810 beginning with `\|\c
 811 .B L\c
 812 \|'.
 813
 814 .TP
 815 .B \-x
 816 If \c
 817 .B \-s\c
 818 \& or \c
 819 .B \-S\c
 820 \& is also specified, delete all local symbols,
 821 not just those beginning with `\|\c
 822 .B L\c
 823 \|'.
 824
 825 .PP
 826
 827 .SH ENVIRONMENT
 828 \c
 829 You can change the behavior of
 830 .B ld\c
 831 \& with the environment variable \c
 832 .B GNUTARGET\c
 833 \&.
 834
 835 \c
 836 .B GNUTARGET\c
 837 \& determines the input-file object format if you don't
 838 use \c
 839 .B \-b\c
 840 \& (or its synonym \c
 841 .B \-format\c
 842 \&).  Its value should be one
 843 of the BFD names for an input format.  If there is no
 844 \c
 845 .B GNUTARGET\c
 846 \& in the environment, \c
 847 .B ld\c
 848 \& uses the natural format
 849 of the host. If \c
 850 .B GNUTARGET\c
 851 \& is set to \c
 852 .B default\c
 853 \& then BFD attempts to discover the
 854 input format by examining binary input files; this method often
 855 succeeds, but there are potential ambiguities, since there is no method
 856 of ensuring that the magic number used to flag object-file formats is
 857 unique.  However, the configuration procedure for BFD on each system
 858 places the conventional format for that system first in the search-list,
 859 so ambiguities are resolved in favor of convention.
 860
 861 .PP
 862
 863 .SH "SEE ALSO"
 864
 865 .BR objdump ( 1 )
 866 .br
 867 .br
 868 .RB "`\|" ld "\|' and `\|" binutils "\|'"
 869 entries in
 870 .B info\c
 871 .br
 872 .I
 873 ld: the GNU linker\c
 874 , Steve Chamberlain and Roland Pesch;
 875 .I
 876 The GNU Binary Utilities\c
 877 , Roland H. Pesch.
 878
 879 .SH COPYING
 880 Copyright (c) 1991, 1992 Free Software Foundation, Inc.
 881 .PP
 882 Permission is granted to make and distribute verbatim copies of
 883 this manual provided the copyright notice and this permission notice
 884 are preserved on all copies.
 885 .PP
 886 Permission is granted to copy and distribute modified versions of this
 887 manual under the conditions for verbatim copying, provided that the
 888 entire resulting derived work is distributed under the terms of a
 889 permission notice identical to this one.
 890 .PP
 891 Permission is granted to copy and distribute translations of this
 892 manual into another language, under the above conditions for modified
 893 versions, except that this permission notice may be included in
 894 translations approved by the Free Software Foundation instead of in
 895 the original English.