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 "[\|" \-split\-by\-reloc\ "\c
  86 .I count\c
  87 \&\|]
  88 .RB "[\|" \-split\-by\-file "\|]"
  89 .RB "[\|" "\-T\ "\c
  90 .I commandfile\c
  91 \&\|]
  92 .RB "[\|" "\-Ttext\ "\c
  93 .I textorg\c
  94 \&\|]
  95 .RB "[\|" "\-Tdata\ "\c
  96 .I dataorg\c
  97 \&\|]
  98 .RB "[\|" "\-Tbss\ "\c
  99 .I bssorg\c
 100 \&\|]
 101 .RB "[\|" \-t "\|]"
 102 .RB "[\|" "\-u\ "\c
 103 .I sym\c
 104 \&]
 105 .RB "[\|" \-V "\|]"
 106 .RB "[\|" \-v "\|]"
 107 .RB "[\|" \-\-verbose "\|]"
 108 .RB "[\|" \-\-version "\|]"
 109 .RB "[\|" \-warn\-common "\|]"
 110 .RB "[\|" \-warn\-once "\|]"
 111 .RB "[\|" \-X "\|]"
 112 .RB "[\|" \-x "\|]"
 113 .ad b
 114 .hy 1
 115 .SH DESCRIPTION
 116 \c
 117 .B ld\c
 118 \& combines a number of object and archive files, relocates
 119 their data and ties up symbol references. Often the last step in
 120 building a new compiled program to run is a call to \c
 121 .B ld\c
 122 \&.
 123
 124 \c
 125 .B ld\c
 126 \& accepts Linker Command Language files
 127 to provide explicit and total control over the linking process.
 128 This man page does not describe the command language; see the `\|\c
 129 .B ld\c
 130 \|' entry in `\|\c
 131 .B info\c
 132 \|', or the manual
 133 .I
 134 ld: the GNU linker
 135 \&, for full details on the command language and on other aspects of
 136 the GNU linker.
 137
 138 This version of \c
 139 .B ld\c
 140 \& uses the general purpose BFD libraries
 141 to operate on object files. This allows \c
 142 .B ld\c
 143 \& to read, combine, and
 144 write object files in many different formats\(em\&for example, COFF or
 145 \c
 146 .B a.out\c
 147 \&.  Different formats may be linked together to produce any
 148 available kind of object file.  You can use `\|\c
 149 .B objdump \-i\c
 150 \|' to get a list of formats supported on various architectures; see
 151 .BR objdump ( 1 ).
 152
 153 Aside from its flexibility, the GNU linker is more helpful than other
 154 linkers in providing diagnostic information.  Many linkers abandon
 155 execution immediately upon encountering an error; whenever possible,
 156 \c
 157 .B ld\c
 158 \& continues executing, allowing you to identify other errors
 159 (or, in some cases, to get an output file in spite of the error).
 160
 161 The GNU linker \c
 162 .B ld\c
 163 \& is meant to cover a broad range of situations,
 164 and to be as compatible as possible with other linkers.  As a result,
 165 you have many choices to control its behavior through the command line,
 166 and through environment variables.
 167
 168 .SH OPTIONS
 169 The plethora of command-line options may seem intimidating, but in
 170 actual practice few of them are used in any particular context.
 171 For instance, a frequent use of \c
 172 .B ld\c
 173 \& is to link standard Unix
 174 object files on a standard, supported Unix system.  On such a system, to
 175 link a file \c
 176 .B hello.o\c
 177 \&:
 178 .sp
 179 .br
 180 $\ ld\ \-o\ output\ /lib/crt0.o\ hello.o\ \-lc
 181 .br
 182 .sp
 183 This tells \c
 184 .B ld\c
 185 \& to produce a file called \c
 186 .B output\c
 187 \& as the
 188 result of linking the file \c
 189 .B /lib/crt0.o\c
 190 \& with \c
 191 .B hello.o\c
 192 \& and
 193 the library \c
 194 .B libc.a\c
 195 \& which will come from the standard search
 196 directories.
 197
 198 The command-line options to \c
 199 .B ld\c
 200 \& may be specified in any order, and
 201 may be repeated at will.  For the most part, repeating an option with a
 202 different argument will either have no further effect, or override prior
 203 occurrences (those further to the left on the command line) of an
 204 option.
 205
 206 The exceptions\(em\&which may meaningfully be used more than once\(em\&are
 207 \c
 208 .B \-A\c
 209 \&, \c
 210 .B \-b\c
 211 \& (or its synonym \c
 212 .B \-format\c
 213 \&), \c
 214 .B \-defsym\c
 215 \&,
 216 \c
 217 .B \-L\c
 218 \&, \c
 219 .B \-l\c
 220 \&, \c
 221 .B \-R\c
 222 \&, and \c
 223 .B \-u\c
 224 \&.
 225
 226 The list of object files to be linked together, shown as \c
 227 .I objfile\c
 228 \&,
 229 may follow, precede, or be mixed in with command-line options; save that
 230 an \c
 231 .I objfile\c
 232 \& argument may not be placed between an option flag and
 233 its argument.
 234
 235 Usually the linker is invoked with at least one object file, but other
 236 forms of binary input files can also be specified with \c
 237 .B \-l\c
 238 \&,
 239 \c
 240 .B \-R\c
 241 \&, and the script command language.  If \c
 242 .I no\c
 243 \& binary input
 244 files at all are specified, the linker does not produce any output, and
 245 issues the message `\|\c
 246 .B No input files\c
 247 \|'.
 248
 249 Option arguments must either follow the option letter without intervening
 250 whitespace, or be given as separate arguments immediately following the
 251 option that requires them.
 252
 253 .TP
 254 .BI "-A" "architecture"\c
 255 \&
 256 In the current release of \c
 257 .B ld\c
 258 \&, this option is useful only for the
 259 Intel 960 family of architectures.  In that \c
 260 .B ld\c
 261 \& configuration, the
 262 \c
 263 .I architecture\c
 264 \& argument is one of the two-letter names identifying
 265 members of the 960 family; the option specifies the desired output
 266 target, and warns of any incompatible instructions in the input files.
 267 It also modifies the linker's search strategy for archive libraries, to
 268 support the use of libraries specific to each particular
 269 architecture, by including in the search loop names suffixed with the
 270 string identifying the architecture.
 271
 272 For example, if your \c
 273 .B ld\c
 274 \& command line included `\|\c
 275 .B \-ACA\c
 276 \|' as
 277 well as `\|\c
 278 .B \-ltry\c
 279 \|', the linker would look (in its built-in search
 280 paths, and in any paths you specify with \c
 281 .B \-L\c
 282 \&) for a library with
 283 the names
 284 .sp
 285 .br
 286 try
 287 .br
 288 libtry.a
 289 .br
 290 tryca
 291 .br
 292 libtryca.a
 293 .br
 294 .sp
 295
 296 The first two possibilities would be considered in any event; the last
 297 two are due to the use of `\|\c
 298 .B \-ACA\c
 299 \|'.
 300
 301 Future releases of \c
 302 .B ld\c
 303 \& may support similar functionality for
 304 other architecture families.
 305
 306 You can meaningfully use \c
 307 .B \-A\c
 308 \& more than once on a command line, if
 309 an architecture family allows combination of target architectures; each
 310 use will add another pair of name variants to search for when \c
 311 .B \-l\c
 312 \&
 313 specifies a library.
 314
 315 .TP
 316 .BI "\-b " "input-format"\c
 317 \&
 318 Specify the binary format for input object files that follow this option
 319 on the command line.  You don't usually need to specify this, as
 320 \c
 321 .B ld\c
 322 \& is configured to expect as a default input format the most
 323 usual format on each machine.  \c
 324 .I input-format\c
 325 \& is a text string, the
 326 name of a particular format supported by the BFD libraries.
 327 \c
 328 .B \-format \c
 329 .I input-format\c
 330 \&\c
 331 \& has the same effect, as does the script command
 332 .BR TARGET .
 333
 334 You may want to use this option if you are linking files with an unusual
 335 binary format.  You can also use \c
 336 .B \-b\c
 337 \& to switch formats explicitly (when
 338 linking object files of different formats), by including
 339 \c
 340 .B \-b \c
 341 .I input-format\c
 342 \&\c
 343 \& before each group of object files in a
 344 particular format.
 345
 346 The default format is taken from the environment variable
 347 .B GNUTARGET\c
 348 \&.  You can also define the input
 349 format from a script, using the command \c
 350 .B TARGET\c
 351 \&.
 352
 353 .TP
 354 .B \-Bstatic
 355 This flag is accepted for command-line compatibility with the SunOS linker,
 356 but has no effect on \c
 357 .B ld\c
 358 \&.
 359
 360 .TP
 361 .BI "\-c " "commandfile"\c
 362 \&
 363 Directs \c
 364 .B ld\c
 365 \& to read link commands from the file
 366 \c
 367 .I commandfile\c
 368 \&.  These commands will completely override \c
 369 .B ld\c
 370 \&'s
 371 default link format (rather than adding to it); \c
 372 .I commandfile\c
 373 \& must
 374 specify everything necessary to describe the target format.
 375
 376
 377 You may also include a script of link commands directly in the command
 378 line by bracketing it between `\|\c
 379 .B {\c
 380 \|' and `\|\c
 381 .B }\c
 382 \|' characters.
 383
 384 .TP
 385 .B \-d
 386 .TP
 387 .B \-dc
 388 .TP
 389 .B \-dp
 390 These three options are equivalent; multiple forms are supported for
 391 compatibility with other linkers.  Use any of them to make \c
 392 .B ld\c
 393 \&
 394 assign space to common symbols even if a relocatable output file is
 395 specified (\c
 396 .B \-r\c
 397 \&).  The script command
 398 \c
 399 .B FORCE_COMMON_ALLOCATION\c
 400 \& has the same effect.
 401
 402 .TP
 403 .BI "-defsym " "symbol"\c
 404 \& = \c
 405 .I expression\c
 406 \&
 407 Create a global symbol in the output file, containing the absolute
 408 address given by \c
 409 .I expression\c
 410 \&.  You may use this option as many
 411 times as necessary to define multiple symbols in the command line.  A
 412 limited form of arithmetic is supported for the \c
 413 .I expression\c
 414 \& in this
 415 context: you may give a hexadecimal constant or the name of an existing
 416 symbol, or use \c
 417 .B +\c
 418 \& and \c
 419 .B \-\c
 420 \& to add or subtract hexadecimal
 421 constants or symbols.  If you need more elaborate expressions, consider
 422 using the linker command language from a script.
 423
 424 .TP
 425 .BI "-e " "entry"\c
 426 \&
 427 Use \c
 428 .I entry\c
 429 \& as the explicit symbol for beginning execution of your
 430 program, rather than the default entry point.  for a
 431 discussion of defaults and other ways of specifying the
 432 entry point.
 433
 434 .TP
 435 .B \-embedded\-relocs
 436 This option is only meaningful when linking MIPS embedded PIC code,
 437 generated by the
 438 .B \-membedded\-pic
 439 option to the GNU compiler and assembler.  It causes the linker to
 440 create a table which may be used at runtime to relocate any data which
 441 was statically initialized to pointer values.  See the code in
 442 testsuite/ld-empic for details.
 443
 444 .TP
 445 .B \-F
 446 .TP
 447 .BI "-F" "format"\c
 448 \&
 449 Some older linkers used this option throughout a compilation toolchain
 450 for specifying object-file format for both input and output object
 451 files.  \c
 452 .B ld\c
 453 \&'s mechanisms (the \c
 454 .B \-b\c
 455 \& or \c
 456 .B \-format\c
 457 \& options
 458 for input files, the \c
 459 .B TARGET\c
 460 \& command in linker scripts for output
 461 files, the \c
 462 .B GNUTARGET\c
 463 \& environment variable) are more flexible, but
 464 but it accepts (and ignores) the \c
 465 .B \-F\c
 466 \& option flag for compatibility
 467 with scripts written to call the old linker.
 468
 469 .TP
 470 .BI "\-format " "input\-format"\c
 471 \&
 472 Synonym for \c
 473 .B \-b\c
 474 \& \c
 475 .I input\-format\c
 476 \&.
 477
 478 .TP
 479 .B \-g
 480 Accepted, but ignored; provided for compatibility with other tools.
 481
 482 .TP
 483 .BI "\-G " "size"\c
 484 Set the maximum size of objects to be optimized using the GP register
 485 to
 486 .I size
 487 under MIPS ECOFF.  Ignored for other object file formats.
 488
 489 .TP
 490 .B \-\-help
 491 Print a summary of the command-line options on the standard output and exit.
 492 This option and
 493 .B \-\-version
 494 begin with two dashes instead of one
 495 for compatibility with other GNU programs.  The other options start with
 496 only one dash for compatibility with other linkers.
 497
 498 .TP
 499 .B \-i
 500 Perform an incremental link (same as option \c
 501 .B \-r\c
 502 \&).
 503
 504 .TP
 505 .BI "\-l" "ar"\c
 506 \&
 507 Add an archive file \c
 508 .I ar\c
 509 \& to the list of files to link.  This
 510 option may be used any number of times.  \c
 511 .B ld\c
 512 \& will search its
 513 path-list for occurrences of \c
 514 .B lib\c
 515 .I ar\c
 516 \&.a\c
 517 \& for every \c
 518 .I ar\c
 519 \&
 520 specified.
 521
 522 .TP
 523 .BI "\-L" "searchdir"\c
 524 \&
 525 This command adds path \c
 526 .I searchdir\c
 527 \& to the list of paths that
 528 \c
 529 .B ld\c
 530 \& will search for archive libraries.  You may use this option
 531 any number of times.
 532
 533 The default set of paths searched (without being specified with
 534 \c
 535 .B \-L\c
 536 \&) depends on what emulation mode \c
 537 .B ld\c
 538 \& is using, and in
 539 some cases also on how it was configured.    The
 540 paths can also be specified in a link script with the \c
 541 .B SEARCH_DIR\c
 542 \&
 543 command.
 544
 545 .TP
 546 .B \-M
 547 Print (to the standard output file) a link map\(em\&diagnostic information
 548 about where symbols are mapped by \c
 549 .B ld\c
 550 \&, and information on global
 551 common storage allocation.
 552
 553 .TP
 554 .BI "\-Map " "mapfile"\c
 555 Print to the file
 556 .I mapfile
 557 a link map\(em\&diagnostic information
 558 about where symbols are mapped by \c
 559 .B ld\c
 560 \&, and information on global
 561 common storage allocation.
 562
 563 .TP
 564 .BI "\-m " "emulation"\c
 565 Emulate the
 566 .I emulation
 567 linker.  You can list the available emulations with the
 568 .I \-\-verbose
 569 or
 570 .I \-V
 571 options.  This option overrides the compiled-in default, which is the
 572 system for which you configured
 573 .BR ld .
 574
 575 .TP
 576 .B \-N
 577 specifies readable and writable \c
 578 .B text\c
 579 \& and \c
 580 .B data\c
 581 \& sections. If
 582 the output format supports Unix style magic numbers, the output is
 583 marked as \c
 584 .B OMAGIC\c
 585 \&.
 586
 587 When you use the `\|\c
 588 .B \-N\c
 589 \&\|' option, the linker does not page-align the
 590 data segment.
 591
 592 .TP
 593 .B \-n
 594 sets the text segment to be read only, and \c
 595 .B NMAGIC\c
 596 \& is written
 597 if possible.
 598
 599 .TP
 600 .B \-noinhibit\-exec
 601 Normally, the linker will not produce an output file if it encounters
 602 errors during the link process.  With this flag, you can specify that
 603 you wish the output file retained even after non-fatal errors.
 604
 605 .TP
 606 .BI "\-o " "output"\c
 607 \&
 608 .I output\c
 609 \&
 610 \c
 611 .I output\c
 612 \& is a name for the program produced by \c
 613 .B ld\c
 614 \&; if this
 615 option is not specified, the name `\|\c
 616 .B a.out\c
 617 \|' is used by default.  The
 618 script command \c
 619 .B OUTPUT\c
 620 \& can also specify the output file name.
 621
 622 .TP
 623 .BI "\-oformat " "output\-format"\c
 624 \&
 625 Specify the binary format for the output object file.
 626 You don't usually need to specify this, as
 627 \c
 628 .B ld\c
 629 \& is configured to produce as a default output format the most
 630 usual format on each machine.  \c
 631 .I output-format\c
 632 \& is a text string, the
 633 name of a particular format supported by the BFD libraries.
 634 The script command
 635 .B OUTPUT_FORMAT
 636 can also specify the output format, but this option overrides it.
 637
 638 .TP
 639 .BI "\-R " "filename"\c
 640 \&
 641 .I file\c
 642 \&
 643 Read symbol names and their addresses from \c
 644 .I filename\c
 645 \&, but do not
 646 relocate it or include it in the output.  This allows your output file
 647 to refer symbolically to absolute locations of memory defined in other
 648 programs.
 649
 650 .TP
 651 .B \-relax
 652 An option with machine dependent effects.  Currently this option is only
 653 supported on the H8/300.
 654
 655 On some platforms, use this option to perform global optimizations that
 656 become possible when the linker resolves addressing in your program, such
 657 as relaxing address modes and synthesizing new instructions in the
 658 output object file.
 659
 660 On platforms where this is not supported, `\|\c
 661 .B \-relax\c
 662 \&\|' is accepted, but has no effect.
 663
 664 .TP
 665 .B \-r
 666 Generates relocatable output\(em\&i.e., generate an output file that can in
 667 turn serve as input to \c
 668 .B ld\c
 669 \&.  This is often called \c
 670 .I partial
 671 linking\c
 672 \&.  As a side effect, in environments that support standard Unix
 673 magic numbers, this option also sets the output file's magic number to
 674 \c
 675 .B OMAGIC\c
 676 \&.
 677 If this option is not specified, an absolute file is produced.  When
 678 linking C++ programs, this option \c
 679 .I will not\c
 680 \& resolve references to
 681 constructors; \c
 682 .B \-Ur\c
 683 \& is an alternative.
 684
 685 This option does the same as \c
 686 .B \-i\c
 687 \&.
 688
 689 .TP
 690 .B \-S
 691 Omits debugger symbol information (but not all symbols) from the output file.
 692
 693 .TP
 694 .B \-s
 695 Omits all symbol information from the output file.
 696
 697 .TP
 698 .B \-sort\-common
 699 Normally, when
 700 .B ld
 701 places the global common symbols in the appropriate output sections,
 702 it sorts them by size.  First come all the one byte symbols, then all
 703 the two bytes, then all the four bytes, and then everything else.
 704 This is to prevent gaps between symbols due to
 705 alignment constraints.  This option disables that sorting.
 706
 707 .TP
 708 .B \-split\-by\-reloc\ \fIcount
 709 Trys to creates extra sections in the output file so that no single
 710 output section in the file contains more than
 711 .I count
 712 relocations.
 713 This is useful when generating huge relocatable for downloading into
 714 certain real time kernels with the COFF object file format; since COFF
 715 cannot represent more than 65535 relocations in a single section.
 716 Note that this will fail to work with object file formats which do not
 717 support arbitrary sections.  The linker will not split up individual
 718 input sections for redistribution, so if a single input section
 719 contains more than
 720 .I count
 721 relocations one output section will contain that many relocations.
 722
 723 .TP
 724 .B \-split\-by\-file
 725 Similar to
 726 .B \-split\-by\-reloc
 727 but creates a new output section for each input file.
 728
 729 .TP
 730 .BI "\-Tbss " "org"\c
 731 .TP
 732 .BI "\-Tdata " "org"\c
 733 .TP
 734 .BI "\-Ttext " "org"\c
 735 Use \c
 736 .I org\c
 737 \& as the starting address for\(em\&respectively\(em\&the
 738 \c
 739 .B bss\c
 740 \&, \c
 741 .B data\c
 742 \&, or the \c
 743 .B text\c
 744 \& segment of the output file.
 745 \c
 746 .I textorg\c
 747 \& must be a hexadecimal integer.
 748
 749 .TP
 750 .BI "\-T " "commandfile"\c
 751 \&
 752 .TP
 753 .BI "\-T" "commandfile"\c
 754 Equivalent to \c
 755 .B \-c \c
 756 .I commandfile\c
 757 \&\c
 758 \&; supported for compatibility with
 759 other tools.
 760
 761 .TP
 762 .B \-t
 763 Prints names of input files as \c
 764 .B ld\c
 765 \& processes them.
 766
 767 .TP
 768 .BI "\-u " "sym"
 769 Forces \c
 770 .I sym\c
 771 \& to be entered in the output file as an undefined symbol.
 772 This may, for example, trigger linking of additional modules from
 773 standard libraries.  \c
 774 .B \-u\c
 775 \& may be repeated with different option
 776 arguments to enter additional undefined symbols.
 777
 778 .TP
 779 .B \-Ur
 780 For anything other than C++ programs, this option is equivalent to
 781 \c
 782 .B \-r\c
 783 \&: it generates relocatable output\(em\&i.e., an output file that can in
 784 turn serve as input to \c
 785 .B ld\c
 786 \&.  When linking C++ programs, \c
 787 .B \-Ur\c
 788 \&
 789 \c
 790 .I will\c
 791 \& resolve references to constructors, unlike \c
 792 .B \-r\c
 793 \&.
 794
 795 .TP
 796 .B \-\-verbose
 797 Display the version number for \c
 798 .B ld
 799 and list the supported emulations.
 800 Display which input files can and can not be opened.
 801
 802 .TP
 803 .B \-v, \-V
 804 Display the version number for \c
 805 .B ld\c
 806 \&.
 807 The
 808 .B \-V
 809 option also lists the supported emulations.
 810
 811 .TP
 812 .B \-\-version
 813 Display the version number for \c
 814 .B ld
 815 and exit.
 816
 817 .TP
 818 .B \-warn\-common
 819 Warn when a common symbol is combined with another common symbol or with
 820 a symbol definition.  Unix linkers allow this somewhat sloppy practice,
 821 but linkers on some other operating systems do not.  This option allows
 822 you to find potential problems from combining global symbols.
 823
 824 .TP
 825 .B \-warn\-once
 826 Only warn once for each undefined symbol, rather than once per module
 827 which refers to it.
 828
 829 .TP
 830 .B \-X
 831 Delete all temporary local symbols.  For most targets, this is all local
 832 symbols whose names begin with `\|\c
 833 .B L\c
 834 \|'.
 835
 836 .TP
 837 .B \-x
 838 Delete all local symbols.
 839
 840 .PP
 841
 842 .SH ENVIRONMENT
 843 \c
 844 You can change the behavior of
 845 .B ld\c
 846 \& with the environment variable \c
 847 .B GNUTARGET\c
 848 \&.
 849
 850 \c
 851 .B GNUTARGET\c
 852 \& determines the input-file object format if you don't
 853 use \c
 854 .B \-b\c
 855 \& (or its synonym \c
 856 .B \-format\c
 857 \&).  Its value should be one
 858 of the BFD names for an input format.  If there is no
 859 \c
 860 .B GNUTARGET\c
 861 \& in the environment, \c
 862 .B ld\c
 863 \& uses the natural format
 864 of the host. If \c
 865 .B GNUTARGET\c
 866 \& is set to \c
 867 .B default\c
 868 \& then BFD attempts to discover the
 869 input format by examining binary input files; this method often
 870 succeeds, but there are potential ambiguities, since there is no method
 871 of ensuring that the magic number used to flag object-file formats is
 872 unique.  However, the configuration procedure for BFD on each system
 873 places the conventional format for that system first in the search-list,
 874 so ambiguities are resolved in favor of convention.
 875
 876 .PP
 877
 878 .SH "SEE ALSO"
 879
 880 .BR objdump ( 1 )
 881 .br
 882 .br
 883 .RB "`\|" ld "\|' and `\|" binutils "\|'"
 884 entries in
 885 .B info\c
 886 .br
 887 .I
 888 ld: the GNU linker\c
 889 , Steve Chamberlain and Roland Pesch;
 890 .I
 891 The GNU Binary Utilities\c
 892 , Roland H. Pesch.
 893
 894 .SH COPYING
 895 Copyright (c) 1991, 1992 Free Software Foundation, Inc.
 896 .PP
 897 Permission is granted to make and distribute verbatim copies of
 898 this manual provided the copyright notice and this permission notice
 899 are preserved on all copies.
 900 .PP
 901 Permission is granted to copy and distribute modified versions of this
 902 manual under the conditions for verbatim copying, provided that the
 903 entire resulting derived work is distributed under the terms of a
 904 permission notice identical to this one.
 905 .PP
 906 Permission is granted to copy and distribute translations of this
 907 manual into another language, under the above conditions for modified
 908 versions, except that this permission notice may be included in
 909 translations approved by the Free Software Foundation instead of in
 910 the original English.