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Code review comments from jeffpc
7029 want per-process exploit mitigation features (secflags)
7030 want basic address space layout randomization (aslr)
7031 noexec_user_stack should be a secflag
7032 want a means to forbid mappings around NULL.
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--- old/usr/src/man/man1/ld.1.man.txt
+++ new/usr/src/man/man1/ld.1.man.txt
1 1 LD(1) User Commands LD(1)
2 2
3 3
4 4
5 5 NAME
6 6 ld - link-editor for object files
7 7
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8 8 SYNOPSIS
9 9 ld [-32 | -64] [-a | -r] [-b] [-Bdirect | nodirect]
10 10 [-B dynamic | static] [-B eliminate] [-B group] [-B local]
11 11 [-B reduce] [-B symbolic] [-c name] [-C] [-d y | n]
12 12 [-D token,...] [-e epsym] [-f name | -F name] [-G] [-h name]
13 13 [-i] [-I name] [-l x] [-L path] [-m] [-M mapfile]
14 14 [-N string] [-o outfile] [-p auditlib] [-P auditlib]
15 15 [-Q y | n] [-R path] [-s] [-S supportlib] [-t]
16 16 [-u symname] [-V] [-Y P,dirlist] [-z absexec]
17 17 [-z allextract | defaultextract | weakextract ] [-z altexec64]
18 - [-z assert-deflib ] [ -z assert-deflib=libname ]
18 + [-z aslr[=state]] [-z assert-deflib] [ -z assert-deflib=libname]
19 19 [-z combreloc | nocombreloc ] [-z defs | nodefs]
20 20 [-z direct | nodirect] [-z endfiltee]
21 21 [-z fatal-warnings | nofatal-warnings ] [-z finiarray=function]
22 22 [-z globalaudit] [-z groupperm | nogroupperm]
23 23 [-z guidance[=id1,id2...] [-z help ]
24 24 [-z ignore | record] [-z initarray=function] [-z initfirst]
25 25 [-z interpose] [-z lazyload | nolazyload]
26 26 [-z ld32=arg1,arg2,...] [-z ld64=arg1,arg2,...]
27 27 [-z loadfltr] [-z muldefs] [-z nocompstrtab] [-z nodefaultlib]
28 28 [-z nodelete] [-z nodlopen] [-z nodump] [-z noldynsym]
29 29 [-z nopartial] [-z noversion] [-z now] [-z origin]
30 30 [-z preinitarray=function] [-z redlocsym] [-z relaxreloc]
31 31 [-z rescan-now] [-z recan] [-z rescan-start ... -z rescan-end]]
32 32 [-z target=sparc|x86] [-z text | textwarn | textoff]
33 33 [-z verbose] [-z wrap=symbol] filename...
34 34
35 35
36 36 DESCRIPTION
37 37 The link-editor, ld, combines relocatable object files by resolving
38 38 symbol references to symbol definitions, together with performing
39 39 relocations. ld operates in two modes, static or dynamic, as governed
40 40 by the -d option. In all cases, the output of ld is left in the file
41 41 a.out by default. See NOTES.
42 42
43 43
44 44 In dynamic mode, -dy, the default, relocatable object files that are
45 45 provided as arguments are combined to produce an executable object
46 46 file. This file is linked at execution with any shared object files
47 47 that are provided as arguments. If the -G option is specified,
48 48 relocatable object files are combined to produce a shared object.
49 49 Without the -G option, a dynamic executable is created.
50 50
51 51
52 52 In static mode, -dn, relocatable object files that are provided as
53 53 arguments are combined to produce a static executable file. If the -r
54 54 option is specified, relocatable object files are combined to produce
55 55 one relocatable object file. See Static Executables.
56 56
57 57
58 58 Dynamic linking is the most common model for combining relocatable
59 59 objects, and the eventual creation of processes within Solaris. This
60 60 environment tightly couples the work of the link-editor and the runtime
61 61 linker, ld.so.1(1). Both of these utilities, together with their
62 62 related technologies and utilities, are extensively documented in the
63 63 Linker and Libraries Guide.
64 64
65 65
66 66 If any argument is a library, ld by default searches the library
67 67 exactly once at the point the library is encountered on the argument
68 68 list. The library can be either a shared object or relocatable archive.
69 69 See ar.h(3HEAD)).
70 70
71 71
72 72 A shared object consists of an indivisible, whole unit that has been
73 73 generated by a previous link-edit of one or more input files. When the
74 74 link-editor processes a shared object, the entire contents of the
75 75 shared object become a logical part of the resulting output file image.
76 76 The shared object is not physically copied during the link-edit as its
77 77 actual inclusion is deferred until process execution. This logical
78 78 inclusion means that all symbol entries defined in the shared object
79 79 are made available to the link-editing process. See Chapter 4, Shared
80 80 Objects, in Linker and Libraries Guide
81 81
82 82
83 83 For an archive library, ld loads only those routines that define an
84 84 unresolved external reference. ld searches the symbol table of the
85 85 archive library sequentially to resolve external references that can be
86 86 satisfied by library members. This search is repeated until no external
87 87 references can be resolved by the archive. Thus, the order of members
88 88 in the library is functionally unimportant, unless multiple library
89 89 members exist that define the same external symbol. Archive libraries
90 90 that have interdependencies can require multiple command line
91 91 definitions, or the use of one of the -z rescan options. See Archive
92 92 Processing in Linker and Libraries Guide.
93 93
94 94
95 95 ld is a cross link-editor, able to link 32-bit objects or 64-bit
96 96 objects, for Sparc or x86 targets. ld uses the ELF class and machine
97 97 type of the first relocatable object on the command line to govern the
98 98 mode in which to operate. The mixing of 32-bit objects and 64-bit
99 99 objects is not permitted. Similarly, only objects of a single machine
100 100 type are allowed. See the -32, -64 and -z target options, and the
101 101 LD_NOEXEC_64 environment variable.
102 102
103 103 Static Executables
104 104 The creation of static executables has been discouraged for many
105 105 releases. In fact, 64-bit system archive libraries have never been
106 106 provided. Because a static executable is built against system archive
107 107 libraries, the executable contains system implementation details. This
108 108 self-containment has a number of drawbacks.
109 109
110 110 o The executable is immune to the benefits of system patches
111 111 delivered as shared objects. The executable therefore, must
112 112 be rebuilt to take advantage of many system improvements.
113 113
114 114 o The ability of the executable to run on future releases can
115 115 be compromised.
116 116
117 117 o The duplication of system implementation details negatively
118 118 affects system performance.
119 119
120 120
121 121 With Solaris 10, 32-bit system archive libraries are no longer
122 122 provided. Without these libraries, specifically libc.a, the creation
123 123 of static executables is no longer achievable without specialized
124 124 system knowledge. However, the capability of ld to process static
125 125 linking options, and the processing of archive libraries, remains
126 126 unchanged.
127 127
128 128 OPTIONS
129 129 The following options are supported.
130 130
131 131 -32 | -64
132 132
133 133 Creates a 32-bit, or 64-bit object.
134 134
135 135 By default, the class of the object being generated is determined
136 136 from the first ELF object processed from the command line. If no
137 137 objects are specified, the class is determined by the first object
138 138 encountered within the first archive processed from the command
139 139 line. If there are no objects or archives, the link-editor creates
140 140 a 32-bit object.
141 141
142 142 The -64 option is required to create a 64-bit object solely from a
143 143 mapfile.
144 144
145 145 This -32 or -64 options can also be used in the rare case of
146 146 linking entirely from an archive that contains a mixture of 32 and
147 147 64-bit objects. If the first object in the archive is not the class
148 148 of the object that is required to be created, then the -32 or -64
149 149 option can be used to direct the link-editor. See The 32-bit link-
150 150 editor and 64-bit link-editor in Linker and Libraries Guide.
151 151
152 152
153 153 -a
154 154
155 155 In static mode only, produces an executable object file. Undefined
156 156 references are not permitted. This option is the default behavior
157 157 for static mode. The -a option can not be used with the -r option.
158 158 See Static Executables under DESCRIPTION.
159 159
160 160
161 161 -b
162 162
163 163 In dynamic mode only, provides no special processing for dynamic
164 164 executable relocations that reference symbols in shared objects.
165 165 Without the -b option, the link-editor applies techniques within a
166 166 dynamic executable so that the text segment can remain read-only.
167 167 One technique is the creation of special position-independent
168 168 relocations for references to functions that are defined in shared
169 169 objects. Another technique arranges for data objects that are
170 170 defined in shared objects to be copied into the memory image of an
171 171 executable at runtime.
172 172
173 173 The -b option is intended for specialized dynamic objects and is
174 174 not recommended for general use. Its use suppresses all specialized
175 175 processing required to ensure an object's shareability, and can
176 176 even prevent the relocation of 64-bit executables.
177 177
178 178
179 179 -B direct | nodirect
180 180
181 181 These options govern direct binding. -B direct establishes direct
182 182 binding information by recording the relationship between each
183 183 symbol reference together with the dependency that provides the
184 184 definition. In addition, direct binding information is established
185 185 between each symbol reference and an associated definition within
186 186 the object being created. The runtime linker uses this information
187 187 to search directly for a symbol in the associated object rather
188 188 than to carry out a default symbol search.
189 189
190 190 Direct binding information can only be established to dependencies
191 191 specified with the link-edit. Thus, you should use the -z defs
192 192 option. Objects that wish to interpose on symbols in a direct
193 193 binding environment should identify themselves as interposers with
194 194 the -z interpose option. The use of -B direct enables -z lazyload
195 195 for all dependencies.
196 196
197 197 The -B nodirect option prevents any direct binding to the
198 198 interfaces offered by the object being created. The object being
199 199 created can continue to directly bind to external interfaces by
200 200 specifying the -z direct option. See Appendix D, Direct Bindings,
201 201 in Linker and Libraries Guide.
202 202
203 203
204 204 -B dynamic | static
205 205
206 206 Options governing library inclusion. -B dynamic is valid in dynamic
207 207 mode only. These options can be specified any number of times on
208 208 the command line as toggles: if the -B static option is given, no
209 209 shared objects are accepted until -B dynamic is seen. See the -l
210 210 option.
211 211
212 212
213 213 -B eliminate
214 214
215 215 Causes any global symbols, not assigned to a version definition, to
216 216 be eliminated from the symbol table. Version definitions can be
217 217 supplied by means of a mapfile to indicate the global symbols that
218 218 should remain visible in the generated object. This option achieves
219 219 the same symbol elimination as the auto-elimination directive that
220 220 is available as part of a mapfile version definition. This option
221 221 can be useful when combining versioned and non-versioned
222 222 relocatable objects. See also the -B local option and the -B reduce
223 223 option. See Defining Additional Symbols with a mapfile in Linker
224 224 and Libraries Guide.
225 225
226 226
227 227 -B group
228 228
229 229 Establishes a shared object and its dependencies as a group.
230 230 Objects within the group are bound to other members of the group at
231 231 runtime. This mode is similar to adding the object to the process
232 232 by using dlopen(3C) with the RTLD_GROUP mode. An object that has an
233 233 explicit dependency on a object identified as a group, becomes a
234 234 member of the group.
235 235
236 236 As the group must be self contained, use of the -B group option
237 237 also asserts the -z defs option.
238 238
239 239
240 240 -B local
241 241
242 242 Causes any global symbols, not assigned to a version definition, to
243 243 be reduced to local. Version definitions can be supplied by means
244 244 of a mapfile to indicate the global symbols that should remain
245 245 visible in the generated object. This option achieves the same
246 246 symbol reduction as the auto-reduction directive that is available
247 247 as part of a mapfile version definition. This option can be useful
248 248 when combining versioned and non-versioned relocatable objects. See
249 249 also the -B eliminate option and the -B reduce option. See Defining
250 250 Additional Symbols with a mapfile in Linker and Libraries Guide.
251 251
252 252
253 253 -B reduce
254 254
255 255 When generating a relocatable object, causes the reduction of
256 256 symbolic information defined by any version definitions. Version
257 257 definitions can be supplied by means of a mapfile to indicate the
258 258 global symbols that should remain visible in the generated object.
259 259 By default, when a relocatable object is generated, version
260 260 definitions are only recorded in the output image. The actual
261 261 reduction of symbolic information is carried out when the object is
262 262 used in the construction of a dynamic executable or shared object.
263 263 The -B reduce option is applied automatically when a dynamic
264 264 executable or shared object is created.
265 265
266 266
267 267 -B symbolic
268 268
269 269 In dynamic mode only. When building a shared object, binds
270 270 references to global symbols to their definitions, if available,
271 271 within the object. Normally, references to global symbols within
272 272 shared objects are not bound until runtime, even if definitions are
273 273 available. This model allows definitions of the same symbol in an
274 274 executable or other shared object to override the object's own
275 275 definition. ld issues warnings for undefined symbols unless -z defs
276 276 overrides.
277 277
278 278 The -B symbolic option is intended for specialized dynamic objects
279 279 and is not recommended for general use. To reduce the runtime
280 280 relocation processing that is required an object, the creation of a
281 281 version definition is recommended.
282 282
283 283
284 284 -c name
285 285
286 286 Records the configuration file name for use at runtime.
287 287 Configuration files can be employed to alter default search paths,
288 288 provide a directory cache, together with providing alternative
289 289 object dependencies. See crle(1).
290 290
291 291
292 292 -C
293 293
294 294 Demangles C++ symbol names displayed in diagnostic messages.
295 295
296 296
297 297 -d y | n
298 298
299 299 When -d y, the default, is specified, ld uses dynamic linking. When
300 300 -d n is specified, ld uses static linking. See Static Executables
301 301 under DESCRIPTION, and -B dynamic|static.
302 302
303 303
304 304 -D token,...
305 305
306 306 Prints debugging information as specified by each token, to the
307 307 standard error. The special token help indicates the full list of
308 308 tokens available. See Debugging Aids in Linker and Libraries Guide.
309 309
310 310
311 311 -e epsym
312 312 --entry epsym
313 313
314 314 Sets the entry point address for the output file to be the symbol
315 315 epsym.
316 316
317 317
318 318 -f name
319 319 --auxiliary name
320 320
321 321 Useful only when building a shared object. Specifies that the
322 322 symbol table of the shared object is used as an auxiliary filter on
323 323 the symbol table of the shared object specified by name. Multiple
324 324 instances of this option are allowed. This option can not be
325 325 combined with the -F option. See Generating Auxiliary Filters in
326 326 Linker and Libraries Guide.
327 327
328 328
329 329 -F name
330 330 --filter name
331 331
332 332 Useful only when building a shared object. Specifies that the
333 333 symbol table of the shared object is used as a filter on the symbol
334 334 table of the shared object specified by name. Multiple instances of
335 335 this option are allowed. This option can not be combined with the
336 336 -f option. See Generating Standard Filters in Linker and Libraries
337 337 Guide.
338 338
339 339
340 340 -G
341 341 -shared
342 342
343 343 In dynamic mode only, produces a shared object. Undefined symbols
344 344 are allowed. See Chapter 4, Shared Objects, in Linker and
345 345 Libraries Guide.
346 346
347 347
348 348 -h name
349 349 --soname name
350 350
351 351 In dynamic mode only, when building a shared object, records name
352 352 in the object's dynamic section. name is recorded in any dynamic
353 353 objects that are linked with this object rather than the object's
354 354 file system name. Accordingly, name is used by the runtime linker
355 355 as the name of the shared object to search for at runtime. See
356 356 Recording a Shared Object Name in Linker and Libraries Guide.
357 357
358 358
359 359 -i
360 360
361 361 Ignores LD_LIBRARY_PATH. This option is useful when an
362 362 LD_LIBRARY_PATH setting is in effect to influence the runtime
363 363 library search, which would interfere with the link-editing being
364 364 performed.
365 365
366 366
367 367 -I name
368 368 --dynamic-linker name
369 369
370 370 When building an executable, uses name as the path name of the
371 371 interpreter to be written into the program header. The default in
372 372 static mode is no interpreter. In dynamic mode, the default is the
373 373 name of the runtime linker, ld.so.1(1). Either case can be
374 374 overridden by -I name. exec(2) loads this interpreter when the
375 375 a.out is loaded, and passes control to the interpreter rather than
376 376 to the a.out directly.
377 377
378 378
379 379 -l x
380 380 --library x
381 381
382 382 Searches a library libx.so or libx.a, the conventional names for
383 383 shared object and archive libraries, respectively. In dynamic
384 384 mode, unless the -B static option is in effect, ld searches each
385 385 directory specified in the library search path for a libx.so or
386 386 libx.a file. The directory search stops at the first directory
387 387 containing either. ld chooses the file ending in .so if -lx expands
388 388 to two files with names of the form libx.so and libx.a. If no
389 389 libx.so is found, then ld accepts libx.a. In static mode, or when
390 390 the -B static option is in effect, ld selects only the file ending
391 391 in .a. ld searches a library when the library is encountered, so
392 392 the placement of -l is significant. See Linking With Additional
393 393 Libraries in Linker and Libraries Guide.
394 394
395 395
396 396 -L path
397 397 --library-path path
398 398
399 399 Adds path to the library search directories. ld searches for
400 400 libraries first in any directories specified by the -L options and
401 401 then in the standard directories. This option is useful only if the
402 402 option precedes the -l options to which the -L option applies. See
403 403 Directories Searched by the Link-Editor in Linker and Libraries
404 404 Guide.
405 405
406 406 The environment variable LD_LIBRARY_PATH can be used to supplement
407 407 the library search path, however the -L option is recommended, as
408 408 the environment variable is also interpreted by the runtime
409 409 environment. See LD_LIBRARY_PATH under ENVIRONMENT VARIABLES.
410 410
411 411
412 412 -m
413 413
414 414 Produces a memory map or listing of the input/output sections,
415 415 together with any non-fatal multiply-defined symbols, on the
416 416 standard output.
417 417
418 418
419 419 -M mapfile
420 420
421 421 Reads mapfile as a text file of directives to ld. This option can
422 422 be specified multiple times. If mapfile is a directory, then all
423 423 regular files, as defined by stat(2), within the directory are
424 424 processed. See Chapter 9, Mapfile Option, in Linker and Libraries
425 425 Guide. Example mapfiles are provided in /usr/lib/ld. See FILES.
426 426
427 427
428 428 -N string
429 429
430 430 This option causes a DT_NEEDED entry to be added to the .dynamic
431 431 section of the object being built. The value of the DT_NEEDED
432 432 string is the string that is specified on the command line. This
433 433 option is position dependent, and the DT_NEEDED .dynamic entry is
434 434 relative to the other dynamic dependencies discovered on the link-
435 435 edit line. This option is useful for specifying dependencies within
436 436 device driver relocatable objects when combined with the -dy and -r
437 437 options.
438 438
439 439
440 440 -o outfile
441 441 --output outfile
442 442
443 443 Produces an output object file that is named outfile. The name of
444 444 the default object file is a.out.
445 445
446 446
447 447 -p auditlib
448 448
449 449 Identifies an audit library, auditlib. This audit library is used
450 450 to audit the object being created at runtime. A shared object
451 451 identified as requiring auditing with the -p option, has this
452 452 requirement inherited by any object that specifies the shared
453 453 object as a dependency. See the -P option. See Runtime Linker
454 454 Auditing Interface in Linker and Libraries Guide.
455 455
456 456
457 457 -P auditlib
458 458
459 459 Identifies an audit library, auditlib. This audit library is used
460 460 to audit the dependencies of the object being created at runtime.
461 461 Dependency auditing can also be inherited from dependencies that
462 462 are identified as requiring auditing. See the -p option, and the -z
463 463 globalaudit option. See Runtime Linker Auditing Interface in Linker
464 464 and Libraries Guide.
465 465
466 466
467 467 -Q y | n
468 468
469 469 Under -Q y, an ident string is added to the .comment section of the
470 470 output file. This string identifies the version of the ld used to
471 471 create the file. This results in multiple ld idents when there have
472 472 been multiple linking steps, such as when using ld -r. This
473 473 identification is identical with the default action of the cc
474 474 command. -Q n suppresses version identification. .comment sections
475 475 can be manipulated by the mcs(1) utility.
476 476
477 477
478 478 -r
479 479 --relocatable
480 480
481 481 Combines relocatable object files to produce one relocatable object
482 482 file. ld does not complain about unresolved references. This
483 483 option cannot be used with the -a option.
484 484
485 485
486 486 -R path
487 487 -rpath path
488 488
489 489 A colon-separated list of directories used to specify library
490 490 search directories to the runtime linker. If present and not NULL,
491 491 the path is recorded in the output object file and passed to the
492 492 runtime linker. Multiple instances of this option are concatenated
493 493 together with each path separated by a colon. See Directories
494 494 Searched by the Runtime Linker in Linker and Libraries Guide.
495 495
496 496 The use of a runpath within an associated object is preferable to
497 497 setting global search paths such as through the LD_LIBRARY_PATH
498 498 environment variable. Only the runpaths that are necessary to find
499 499 the objects dependencies should be recorded. ldd(1) can also be
500 500 used to discover unused runpaths in dynamic objects, when used with
501 501 the -U option.
502 502
503 503 Various tokens can also be supplied with a runpath that provide a
504 504 flexible means of identifying system capabilities or an objects
505 505 location. See Appendix C, Establishing Dependencies with Dynamic
506 506 String Tokens, in Linker and Libraries Guide. The $ORIGIN token is
507 507 especially useful in allowing dynamic objects to be relocated to
508 508 different locations in the file system.
509 509
510 510
511 511 -s
512 512 --strip-all
513 513
514 514 Strips symbolic information from the output file. Any debugging
515 515 information, that is, .line, .debug*, and .stab* sections, and
516 516 their associated relocation entries are removed. Except for
517 517 relocatable files, a symbol table SHT_SYMTAB and its associated
518 518 string table section are not created in the output object file. The
519 519 elimination of a SHT_SYMTAB symbol table can reduce the .stab*
520 520 debugging information that is generated using the compiler drivers
521 521 -g option. See the -z redlocsym and -z noldynsym options.
522 522
523 523
524 524 -S supportlib
525 525
526 526 The shared object supportlib is loaded with ld and given
527 527 information regarding the linking process. Shared objects that are
528 528 defined by using the -S option can also be supplied using the
529 529 SGS_SUPPORT environment variable. See Link-Editor Support Interface
530 530 in Linker and Libraries Guide.
531 531
532 532
533 533 -t
534 534
535 535 Turns off the warning for multiply-defined symbols that have
536 536 different sizes or different alignments.
537 537
538 538
539 539 -u symname
540 540 --undefined symname
541 541
542 542 Enters symname as an undefined symbol in the symbol table. This
543 543 option is useful for loading entirely from an archive library. In
544 544 this instance, an unresolved reference is needed to force the
545 545 loading of the first routine. The placement of this option on the
546 546 command line is significant. This option must be placed before the
547 547 library that defines the symbol. See Defining Additional Symbols
548 548 with the u option in Linker and Libraries Guide.
549 549
550 550
551 551 -V
552 552 --version
553 553
554 554 Outputs a message giving information about the version of ld being
555 555 used.
556 556
557 557
558 558 -Y P,dirlist
559 559
560 560 Changes the default directories used for finding libraries. dirlist
561 561 is a colon-separated path list.
562 562
563 563
564 564 -z absexec
565 565
566 566 Useful only when building a dynamic executable. Specifies that
567 567 references to external absolute symbols should be resolved
568 568 immediately instead of being left for resolution at runtime. In
569 569 very specialized circumstances, this option removes text
570 570 relocations that can result in excessive swap space demands by an
571 571 executable.
572 572
573 573
574 574 -z allextract | defaultextract | weakextract
575 575 --whole-archive | --no-whole-archive
576 576
577 577 Alters the extraction criteria of objects from any archives that
578 578 follow. By default, archive members are extracted to satisfy
579 579 undefined references and to promote tentative definitions with data
580 580 definitions. Weak symbol references do not trigger extraction.
581 581 Under the -z allextract or --whole-archive options, all archive
582 582 members are extracted from the archive. Under -z weakextract, weak
583 583 references trigger archive extraction. The -z defaultextract or
584 584 --no-whole-archive options provide a means of returning to the
585 585 default following use of the former extract options. See Archive
586 586 Processing in Linker and Libraries Guide.
587 587
588 588
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589 589 -z altexec64
590 590
591 591 Execute the 64-bit ld. The creation of very large 32-bit objects
592 592 can exhaust the virtual memory that is available to the 32-bit ld.
593 593 The -z altexec64 option can be used to force the use of the
594 594 associated 64-bit ld. The 64-bit ld provides a larger virtual
595 595 address space for building 32-bit objects. See The 32-bit link-
596 596 editor and 64-bit link-editor in Linker and Libraries Guide.
597 597
598 598
599 + -z aslr[=state]
600 +
601 + Specify whether the executable's address space should be randomized
602 + on execution. If state is "enabled" randomization will always
603 + occur when this executable is run (regardless of inherited
604 + settings). If state is "disabled" randomization will never occur
605 + when this executable is run. If state is omitted, ASLR is enabled.
606 +
607 + An executable that should simply use the settings inherited from
608 + its environment should not use this flag at all.
609 +
610 +
599 611 -z combreloc | nocombreloc
600 612
601 613 By default, ld combines multiple relocation sections when building
602 614 executables or shared objects. This section combination differs
603 615 from relocatable objects, in which relocation sections are
604 616 maintained in a one-to-one relationship with the sections to which
605 617 the relocations must be applied. The -z nocombreloc option disables
606 618 this merging of relocation sections, and preserves the one-to-one
607 619 relationship found in the original relocatable objects.
608 620
609 621 ld sorts the entries of data relocation sections by their symbol
610 622 reference. This sorting reduces runtime symbol lookup. When
611 623 multiple relocation sections are combined, this sorting produces
612 624 the least possible relocation overhead when objects are loaded into
613 625 memory, and speeds the runtime loading of dynamic objects.
614 626
615 627 Historically, the individual relocation sections were carried over
616 628 to any executable or shared object, and the -z combreloc option was
617 629 required to enable the relocation section merging previously
618 630 described. Relocation section merging is now the default. The -z
619 631 combreloc option is still accepted for the benefit of old build
620 632 environments, but the option is unnecessary, and has no effect.
621 633
622 634
623 635 -z assert-deflib
624 636 -z assert-deflib=libname
625 637
626 638 Enables warnings that check the location of where libraries passed
627 639 in with -l are found. If the link-editor finds a library on its
628 640 default search path it will emit a warning. This warning can be
629 641 made fatal in conjunction with the option -z fatal-warnings.
630 642 Passing libname white lists a library from this check. The library
631 643 must be the full name of the library, e.g. libc.so. To white list
632 644 multiple libraries, the -z assert-deflib=libname option can be
633 645 repeated multiple times. This option is useful when trying to build
634 646 self-contained objects where a referenced library might exist in
635 647 the default system library path and in alternate paths specified by
636 648 -L, but you only want the alternate paths to be used.
637 649
638 650
639 651 -z defs | nodefs
640 652 --no-undefined
641 653
642 654 The -z defs option and the --no-undefined option force a fatal
643 655 error if any undefined symbols remain at the end of the link. This
644 656 mode is the default when an executable is built. For historic
645 657 reasons, this mode is not the default when building a shared
646 658 object. Use of the -z defs option is recommended, as this mode
647 659 assures the object being built is self-contained. A self-contained
648 660 object has all symbolic references resolved internally, or to the
649 661 object's immediate dependencies.
650 662
651 663 The -z nodefs option allows undefined symbols. For historic
652 664 reasons, this mode is the default when a shared object is built.
653 665 When used with executables, the behavior of references to such
654 666 undefined symbols is unspecified. Use of the -z nodefs option is
655 667 not recommended.
656 668
657 669
658 670 -z direct | nodirect
659 671
660 672 Enables or disables direct binding to any dependencies that follow
661 673 on the command line. These options allow finer control over direct
662 674 binding than the global counterpart -B direct. The -z direct option
663 675 also differs from the -B direct option in the following areas.
664 676 Direct binding information is not established between a symbol
665 677 reference and an associated definition within the object being
666 678 created. Lazy loading is not enabled.
667 679
668 680
669 681 -z endfiltee
670 682
671 683 Marks a filtee so that when processed by a filter, the filtee
672 684 terminates any further filtee searches by the filter. See Reducing
673 685 Filtee Searches in Linker and Libraries Guide.
674 686
675 687
676 688 -z fatal-warnings | nofatal-warnings
677 689 --fatal-warnings | --no-fatal-warnings
678 690
679 691 Controls the behavior of warnings emitted from the link-editor.
680 692 Setting -z fatal-warnings promotes warnings emitted by the link-
681 693 editor to fatal errors that will cause the link-editor to fail
682 694 before linking. -z nofatal-warnings instead demotes these warnings
683 695 such that they will not cause the link-editor to exit prematurely.
684 696
685 697
686 698
687 699 -z finiarray=function
688 700
689 701 Appends an entry to the .fini_array section of the object being
690 702 built. If no .fini_array section is present, a section is created.
691 703 The new entry is initialized to point to function. See
692 704 Initialization and Termination Sections in Linker and Libraries
693 705 Guide.
694 706
695 707
696 708 -z globalaudit
697 709
698 710 This option supplements an audit library definition that has been
699 711 recorded with the -P option. This option is only meaningful when
700 712 building a dynamic executable. Audit libraries that are defined
701 713 within an object with the -P option typically allow for the
702 714 auditing of the immediate dependencies of the object. The -z
703 715 globalaudit promotes the auditor to a global auditor, thus allowing
704 716 the auditing of all dependencies. See Invoking the Auditing
705 717 Interface in Linker and Libraries Guide.
706 718
707 719 An auditor established with the -P option and the -z globalaudit
708 720 option, is equivalent to the auditor being established with the
709 721 LD_AUDIT environment variable. See ld.so.1(1).
710 722
711 723
712 724 -z groupperm | nogroupperm
713 725
714 726 Assigns, or deassigns each dependency that follows to a unique
715 727 group. The assignment of a dependency to a group has the same
716 728 effect as if the dependency had been built using the -B group
717 729 option.
718 730
719 731
720 732 -z guidance[=id1,id2...]
721 733
722 734 Give messages suggesting link-editor features that could improve
723 735 the resulting dynamic object.
724 736
725 737 Specific classes of suggestion can be silenced by specifying an
726 738 optional comma separated list of guidance identifiers.
727 739
728 740 The current classes of suggestion provided are:
729 741
730 742
731 743 Enable use of direct binding
732 744
733 745 Suggests that -z direct or -B direct be present prior to any
734 746 specified dependency. This allows predictable symbol binding
735 747 at runtime.
736 748
737 749 Can be disabled with -z guidance=nodirect
738 750
739 751
740 752 Enable lazy dependency loading
741 753
742 754 Suggests that -z lazyload be present prior to any specified
743 755 dependency. This allows the dynamic object to be loaded more
744 756 quickly.
745 757
746 758 Can be disabled with -z guidance=nolazyload.
747 759
748 760
749 761 Shared objects should define all their dependencies.
750 762
751 763 Suggests that -z defs be specified on the link-editor command
752 764 line. Shared objects that explicitly state all their
753 765 dependencies behave more predictably when used.
754 766
755 767 Can be be disabled with -z guidance=nodefs
756 768
757 769
758 770 Version 2 mapfile syntax
759 771
760 772 Suggests that any specified mapfiles use the more readable
761 773 version 2 syntax.
762 774
763 775 Can be disabled with -z guidance=nomapfile.
764 776
765 777
766 778 Read-only text segment
767 779
768 780 Should any runtime relocations within the text segment exist,
769 781 suggests that the object be compiled with position independent
770 782 code (PIC). Keeping large allocatable sections read-only
771 783 allows them to be shared between processes using a given shared
772 784 object.
773 785
774 786 Can be disabled with -z guidance=notext
775 787
776 788
777 789 No unused dependencies
778 790
779 791 Suggests that any dependency not referenced by the resulting
780 792 dynamic object be removed from the link-editor command line.
781 793
782 794 Can be disabled with -z guidance=nounused.
783 795
784 796
785 797 -z help
786 798 --help
787 799
788 800 Print a summary of the command line options on the standard output
789 801 and exit.
790 802
791 803
792 804 -z ignore | record
793 805
794 806 Ignores, or records, dynamic dependencies that are not referenced
795 807 as part of the link-edit. Ignores, or records, unreferenced ELF
796 808 sections from the relocatable objects that are read as part of the
797 809 link-edit. By default, -z record is in effect.
798 810
799 811 If an ELF section is ignored, the section is eliminated from the
800 812 output file being generated. A section is ignored when three
801 813 conditions are true. The eliminated section must contribute to an
802 814 allocatable segment. The eliminated section must provide no global
803 815 symbols. No other section from any object that contributes to the
804 816 link-edit, must reference an eliminated section.
805 817
806 818
807 819 -z initarray=function
808 820
809 821 Appends an entry to the .init_array section of the object being
810 822 built. If no .init_array section is present, a section is created.
811 823 The new entry is initialized to point to function. See
812 824 Initialization and Termination Sections in Linker and Libraries
813 825 Guide.
814 826
815 827
816 828 -z initfirst
817 829
818 830 Marks the object so that its runtime initialization occurs before
819 831 the runtime initialization of any other objects brought into the
820 832 process at the same time. In addition, the object runtime
821 833 finalization occurs after the runtime finalization of any other
822 834 objects removed from the process at the same time. This option is
823 835 only meaningful when building a shared object.
824 836
825 837
826 838 -z interpose
827 839
828 840 Marks the object as an interposer. At runtime, an object is
829 841 identified as an explicit interposer if the object has been tagged
830 842 using the -z interpose option. An explicit interposer is also
831 843 established when an object is loaded using the LD_PRELOAD
832 844 environment variable. Implicit interposition can occur because of
833 845 the load order of objects, however, this implicit interposition is
834 846 unknown to the runtime linker. Explicit interposition can ensure
835 847 that interposition takes place regardless of the order in which
836 848 objects are loaded. Explicit interposition also ensures that the
837 849 runtime linker searches for symbols in any explicit interposers
838 850 when direct bindings are in effect.
839 851
840 852
841 853 -z lazyload | nolazyload
842 854
843 855 Enables or disables the marking of dynamic dependencies to be
844 856 lazily loaded. Dynamic dependencies which are marked lazyload are
845 857 not loaded at initial process start-up. These dependencies are
846 858 delayed until the first binding to the object is made. Note: Lazy
847 859 loading requires the correct declaration of dependencies, together
848 860 with associated runpaths for each dynamic object used within a
849 861 process. See Lazy Loading of Dynamic Dependencies in Linker and
850 862 Libraries Guide.
851 863
852 864
853 865 -z ld32=arg1,arg2,...
854 866 -z ld64=arg1,arg2,...
855 867
856 868 The class of the link-editor is affected by the class of the output
857 869 file being created and by the capabilities of the underlying
858 870 operating system. The -z ld[32|64] options provide a means of
859 871 defining any link-editor argument. The defined argument is only
860 872 interpreted, respectively, by the 32-bit class or 64-bit class of
861 873 the link-editor.
862 874
863 875 For example, support libraries are class specific, so the correct
864 876 class of support library can be ensured using:
865 877
866 878 ld ... -z ld32=-Saudit32.so.1 -z ld64=-Saudit64.so.1 ...
867 879
868 880
869 881 The class of link-editor that is invoked is determined from the ELF
870 882 class of the first relocatable file that is seen on the command
871 883 line. This determination is carried out prior to any -z ld[32|64]
872 884 processing.
873 885
874 886
875 887 -z loadfltr
876 888
877 889 Marks a filter to indicate that filtees must be processed
878 890 immediately at runtime. Normally, filter processing is delayed
879 891 until a symbol reference is bound to the filter. The runtime
880 892 processing of an object that contains this flag mimics that which
881 893 occurs if the LD_LOADFLTR environment variable is in effect. See
882 894 the ld.so.1(1).
883 895
884 896
885 897 -z muldefs
886 898 --allow-multiple-definition
887 899
888 900 Allows multiple symbol definitions. By default, multiple symbol
889 901 definitions that occur between relocatable objects result in a
890 902 fatal error condition. This option, suppresses the error condition,
891 903 allowing the first symbol definition to be taken.
892 904
893 905
894 906 -z nocompstrtab
895 907
896 908 Disables the compression of ELF string tables. By default, string
897 909 compression is applied to SHT_STRTAB sections, and to SHT_PROGBITS
898 910 sections that have their SHF_MERGE and SHF_STRINGS section flags
899 911 set.
900 912
901 913
902 914 -z nodefaultlib
903 915
904 916 Marks the object so that the runtime default library search path,
905 917 used after any LD_LIBRARY_PATH or runpaths, is ignored. This option
906 918 implies that all dependencies of the object can be satisfied from
907 919 its runpath.
908 920
909 921
910 922 -z nodelete
911 923
912 924 Marks the object as non-deletable at runtime. This mode is similar
913 925 to adding the object to the process by using dlopen(3C) with the
914 926 RTLD_NODELETE mode.
915 927
916 928
917 929 -z nodlopen
918 930
919 931 Marks the object as not available to dlopen(3C), either as the
920 932 object specified by the dlopen(), or as any form of dependency
921 933 required by the object specified by the dlopen(). This option is
922 934 only meaningful when building a shared object.
923 935
924 936
925 937 -z nodump
926 938
927 939 Marks the object as not available to dldump(3C).
928 940
929 941
930 942 -z noldynsym
931 943
932 944 Prevents the inclusion of a .SUNW_ldynsym section in dynamic
933 945 executables or sharable libraries. The .SUNW_ldynsym section
934 946 augments the .dynsym section by providing symbols for local
935 947 functions. Local function symbols allow debuggers to display local
936 948 function names in stack traces from stripped programs. Similarly,
937 949 dladdr(3C) is able to supply more accurate results.
938 950
939 951 The -z noldynsym option also prevents the inclusion of the two
940 952 symbol sort sections that are related to the .SUNW_ldynsym section.
941 953 The .SUNW_dynsymsort section provides sorted access to regular
942 954 function and variable symbols. The .SUNW_dyntlssort section
943 955 provides sorted access to thread local storage (TLS) variable
944 956 symbols.
945 957
946 958 The .SUNW_ldynsym, .SUNW_dynsymsort, and .SUNW_dyntlssort sections,
947 959 which becomes part of the allocable text segment of the resulting
948 960 file, cannot be removed by strip(1). Therefore, the -z noldynsym
949 961 option is the only way to prevent their inclusion. See the -s and
950 962 -z redlocsym options.
951 963
952 964
953 965 -z nopartial
954 966
955 967 Partially initialized symbols, that are defined within relocatable
956 968 object files, are expanded in the output file being generated.
957 969
958 970
959 971 -z noversion
960 972
961 973 Does not record any versioning sections. Any version sections or
962 974 associated .dynamic section entries are not generated in the output
963 975 image.
964 976
965 977
966 978 -z now
967 979
968 980 Marks the object as requiring non-lazy runtime binding. This mode
969 981 is similar to adding the object to the process by using dlopen(3C)
970 982 with the RTLD_NOW mode. This mode is also similar to having the
971 983 LD_BIND_NOW environment variable in effect. See ld.so.1(1).
972 984
973 985
974 986 -z origin
975 987
976 988 Marks the object as requiring immediate $ORIGIN processing at
977 989 runtime. This option is only maintained for historic
978 990 compatibility, as the runtime analysis of objects to provide for
979 991 $ORIGIN processing is now default.
980 992
981 993
982 994 -z preinitarray=function
983 995
984 996 Appends an entry to the .preinitarray section of the object being
985 997 built. If no .preinitarray section is present, a section is
986 998 created. The new entry is initialized to point to function. See
987 999 Initialization and Termination Sections in Linker and Libraries
988 1000 Guide.
989 1001
990 1002
991 1003 -z redlocsym
992 1004
993 1005 Eliminates all local symbols except for the SECT symbols from the
994 1006 symbol table SHT_SYMTAB. All relocations that refer to local
995 1007 symbols are updated to refer to the corresponding SECT symbol. This
996 1008 option allows specialized objects to greatly reduce their symbol
997 1009 table sizes. Eliminated local symbols can reduce the .stab*
998 1010 debugging information that is generated using the compiler drivers
999 1011 -g option. See the -s and -z noldynsym options.
1000 1012
1001 1013
1002 1014 -z relaxreloc
1003 1015
1004 1016 ld normally issues a fatal error upon encountering a relocation
1005 1017 using a symbol that references an eliminated COMDAT section. If -z
1006 1018 relaxreloc is enabled, ld instead redirects such relocations to the
1007 1019 equivalent symbol in the COMDAT section that was kept. -z
1008 1020 relaxreloc is a specialized option, mainly of interest to compiler
1009 1021 authors, and is not intended for general use.
1010 1022
1011 1023
1012 1024 -z rescan-now
1013 1025 -z rescan
1014 1026
1015 1027 These options rescan the archive files that are provided to the
1016 1028 link-edit. By default, archives are processed once as the archives
1017 1029 appear on the command line. Archives are traditionally specified at
1018 1030 the end of the command line so that their symbol definitions
1019 1031 resolve any preceding references. However, specifying archives
1020 1032 multiple times to satisfy their own interdependencies can be
1021 1033 necessary.
1022 1034
1023 1035 -z rescan-now is a positional option, and is processed by the link-
1024 1036 editor immediately when encountered on the command line. All
1025 1037 archives seen on the command line up to that point are immediately
1026 1038 reprocessed in an attempt to locate additional archive members that
1027 1039 resolve symbol references. This archive rescanning is repeated
1028 1040 until a pass over the archives occurs in which no new members are
1029 1041 extracted.
1030 1042
1031 1043 -z rescan is a position independent option. The link-editor defers
1032 1044 the rescan operation until after it has processed the entire
1033 1045 command line, and then initiates a final rescan operation over all
1034 1046 archives seen on the command line. The -z rescan operation can
1035 1047 interact incorrectly with objects that contain
1036 1048 initialization (.init) or finalization (.fini) sections, preventing
1037 1049 the code in those sections from running. For this reason, -z rescan
1038 1050 is deprecated, and use of -z rescan-now is advised.
1039 1051
1040 1052
1041 1053 -z rescan-start ... -z rescan-end
1042 1054 --start-group ... --end-group
1043 1055 -( ... -)
1044 1056
1045 1057 Defines an archive rescan group. This is a positional construct,
1046 1058 and is processed by the link-editor immediately upon encountering
1047 1059 the closing delimiter option. Archives found within the group
1048 1060 delimiter options are reprocessed as a group in an attempt to
1049 1061 locate additional archive members that resolve symbol references.
1050 1062 This archive rescanning is repeated until a pass over the
1051 1063 archives On the occurs in which no new members are extracted.
1052 1064 Archive rescan groups cannot be nested.
1053 1065
1054 1066
1055 1067 -z target=sparc|x86
1056 1068
1057 1069 Specifies the machine type for the output object. Supported targets
1058 1070 are Sparc and x86. The 32-bit machine type for the specified target
1059 1071 is used unless the -64 option is also present, in which case the
1060 1072 corresponding 64-bit machine type is used. By default, the machine
1061 1073 type of the object being generated is determined from the first ELF
1062 1074 object processed from the command line. If no objects are
1063 1075 specified, the machine type is determined by the first object
1064 1076 encountered within the first archive processed from the command
1065 1077 line. If there are no objects or archives, the link-editor assumes
1066 1078 the native machine. This option is useful when creating an object
1067 1079 directly with ld whose input is solely from a mapfile. See the -M
1068 1080 option. It can also be useful in the rare case of linking entirely
1069 1081 from an archive that contains objects of different machine types
1070 1082 for which the first object is not of the desired machine type. See
1071 1083 The 32-bit link-editor and 64-bit link-editor in Linker and
1072 1084 Libraries Guide.
1073 1085
1074 1086
1075 1087 -z text
1076 1088
1077 1089 In dynamic mode only, forces a fatal error if any relocations
1078 1090 against non-writable, allocatable sections remain. For historic
1079 1091 reasons, this mode is not the default when building an executable
1080 1092 or shared object. However, its use is recommended to ensure that
1081 1093 the text segment of the dynamic object being built is shareable
1082 1094 between multiple running processes. A shared text segment incurs
1083 1095 the least relocation overhead when loaded into memory. See
1084 1096 Position-Independent Code in Linker and Libraries Guide.
1085 1097
1086 1098
1087 1099 -z textoff
1088 1100
1089 1101 In dynamic mode only, allows relocations against all allocatable
1090 1102 sections, including non-writable ones. This mode is the default
1091 1103 when building a shared object.
1092 1104
1093 1105
1094 1106 -z textwarn
1095 1107
1096 1108 In dynamic mode only, lists a warning if any relocations against
1097 1109 non-writable, allocatable sections remain. This mode is the default
1098 1110 when building an executable.
1099 1111
1100 1112
1101 1113 -z verbose
1102 1114
1103 1115 This option provides additional warning diagnostics during a link-
1104 1116 edit. Presently, this option conveys suspicious use of
1105 1117 displacement relocations. This option also conveys the restricted
1106 1118 use of static TLS relocations when building shared objects. In
1107 1119 future, this option might be enhanced to provide additional
1108 1120 diagnostics that are deemed too noisy to be generated by default.
1109 1121
1110 1122
1111 1123 -zwrap=symbol
1112 1124 -wrap= symbol
1113 1125 --wrap= symbol
1114 1126
1115 1127 Rename undefined references to symbol in order to allow wrapper
1116 1128 code to be linked into the output object without having to modify
1117 1129 source code. When -z wrap is specified, all undefined references to
1118 1130 symbol are modified to reference __wrap_symbol, and all references
1119 1131 to __real_symbol are modified to reference symbol. The user is
1120 1132 expected to provide an object containing the __wrap_symbol
1121 1133 function. This wrapper function can call __real_symbol in order to
1122 1134 reference the actual function being wrapped.
1123 1135
1124 1136 The following is an example of a wrapper for the malloc(3C)
1125 1137 function:
1126 1138
1127 1139 void *
1128 1140 __wrap_malloc(size_t c)
1129 1141 {
1130 1142 (void) printf("malloc called with %zu\n", c);
1131 1143 return (__real_malloc(c));
1132 1144 }
1133 1145
1134 1146 If you link other code with this file using -z wrap=malloc to
1135 1147 compile all the objects, then all calls to malloc will call the
1136 1148 function __wrap_malloc instead. The call to __real_malloc will call
1137 1149 the real malloc function.
1138 1150
1139 1151 The real and wrapped functions should be maintained in separate
1140 1152 source files. Otherwise, the compiler or assembler may resolve the
1141 1153 call instead of leaving that operation for the link-editor to carry
1142 1154 out, and prevent the wrap from occurring.
1143 1155
1144 1156
1145 1157 ENVIRONMENT VARIABLES
1146 1158 LD_ALTEXEC
1147 1159
1148 1160 An alternative link-editor path name. ld executes, and passes
1149 1161 control to this alternative link-editor. This environment variable
1150 1162 provides a generic means of overriding the default link-editor that
1151 1163 is called from the various compiler drivers. See the -z altexec64
1152 1164 option.
1153 1165
1154 1166
1155 1167 LD_LIBRARY_PATH
1156 1168
1157 1169 A list of directories in which to search for the libraries
1158 1170 specified using the -l option. Multiple directories are separated
1159 1171 by a colon. In the most general case, this environment variable
1160 1172 contains two directory lists separated by a semicolon:
1161 1173
1162 1174 dirlist1;dirlist2
1163 1175
1164 1176
1165 1177 If ld is called with any number of occurrences of -L, as in:
1166 1178
1167 1179 ld ... -Lpath1 ... -Lpathn ...
1168 1180
1169 1181
1170 1182 then the search path ordering is:
1171 1183
1172 1184 dirlist1 path1 ... pathn dirlist2 LIBPATH
1173 1185
1174 1186
1175 1187 When the list of directories does not contain a semicolon, the list
1176 1188 is interpreted as dirlist2.
1177 1189
1178 1190 The LD_LIBRARY_PATH environment variable also affects the runtime
1179 1191 linkers search for dynamic dependencies.
1180 1192
1181 1193 This environment variable can be specified with a _32 or _64
1182 1194 suffix. This makes the environment variable specific, respectively,
1183 1195 to 32-bit or 64-bit processes and overrides any non-suffixed
1184 1196 version of the environment variable that is in effect.
1185 1197
1186 1198
1187 1199 LD_NOEXEC_64
1188 1200
1189 1201 Suppresses the automatic execution of the 64-bit link-editor. By
1190 1202 default, the link-editor executes the 64-bit version when the ELF
1191 1203 class of the first relocatable file identifies a 64-bit object. The
1192 1204 64-bit image that a 32-bit link-editor can create, has some
1193 1205 limitations. However, some link-edits might find the use of the
1194 1206 32-bit link-editor faster.
1195 1207
1196 1208
1197 1209 LD_OPTIONS
1198 1210
1199 1211 A default set of options to ld. LD_OPTIONS is interpreted by ld
1200 1212 just as though its value had been placed on the command line,
1201 1213 immediately following the name used to invoke ld, as in:
1202 1214
1203 1215 ld $LD_OPTIONS ... other-arguments ...
1204 1216
1205 1217
1206 1218
1207 1219
1208 1220 LD_RUN_PATH
1209 1221
1210 1222 An alternative mechanism for specifying a runpath to the link-
1211 1223 editor. See the -R option. If both LD_RUN_PATH and the -R option
1212 1224 are specified, -R supersedes.
1213 1225
1214 1226
1215 1227 SGS_SUPPORT
1216 1228
1217 1229 Provides a colon-separated list of shared objects that are loaded
1218 1230 with the link-editor and given information regarding the linking
1219 1231 process. This environment variable can be specified with a _32 or
1220 1232 _64 suffix. This makes the environment variable specific,
1221 1233 respectively, to the 32-bit or 64-bit class of ld and overrides any
1222 1234 non-suffixed version of the environment variable that is in effect.
1223 1235 See the -S option.
1224 1236
1225 1237
1226 1238
1227 1239 Notice that environment variable-names that begin with the characters
1228 1240 'LD_' are reserved for possible future enhancements to ld and
1229 1241 ld.so.1(1).
1230 1242
1231 1243 FILES
1232 1244 libx.so
1233 1245 shared object libraries.
1234 1246
1235 1247
1236 1248 libx.a
1237 1249 archive libraries.
1238 1250
1239 1251
1240 1252 a.out
1241 1253 default output file.
1242 1254
1243 1255
1244 1256 LIBPATH
1245 1257 For 32-bit libraries, the default search path is
1246 1258 /usr/ccs/lib, followed by /lib, and finally /usr/lib.
1247 1259 For 64-bit libraries, the default search path is
1248 1260 /lib/64, followed by /usr/lib/64.
1249 1261
1250 1262
1251 1263 /usr/lib/ld
1252 1264 A directory containing several mapfiles that can be used
1253 1265 during link-editing. These mapfiles provide various
1254 1266 capabilities, such as defining memory layouts, aligning
1255 1267 bss, and defining non-executable stacks.
1256 1268
1257 1269
1258 1270 ATTRIBUTES
1259 1271 See attributes(5) for descriptions of the following attributes:
1260 1272
1261 1273
1262 1274
1263 1275
1264 1276 +--------------------+-----------------+
1265 1277 | ATTRIBUTE TYPE | ATTRIBUTE VALUE |
1266 1278 +--------------------+-----------------+
1267 1279 |Interface Stability | Committed |
1268 1280 +--------------------+-----------------+
1269 1281
1270 1282 SEE ALSO
1271 1283 as(1), crle(1), gprof(1), ld.so.1(1), ldd(1), mcs(1), pvs(1), exec(2),
1272 1284 stat(2), dlopen(3C), dldump(3C), elf(3ELF), ar.h(3HEAD), a.out(4),
1273 1285 attributes(5)
1274 1286
1275 1287
1276 1288 Linker and Libraries Guide
1277 1289
1278 1290 NOTES
1279 1291 Default options applied by ld are maintained for historic reasons. In
1280 1292 today's programming environment, where dynamic objects dominate,
1281 1293 alternative defaults would often make more sense. However, historic
1282 1294 defaults must be maintained to ensure compatibility with existing
1283 1295 program development environments. Historic defaults are called out
1284 1296 wherever possible in this manual. For a description of the current
1285 1297 recommended options, see Appendix A, Link-Editor Quick Reference, in
1286 1298 Linker and Libraries Guide.
1287 1299
1288 1300
1289 1301 If the file being created by ld already exists, the file is unlinked
1290 1302 after all input files have been processed. A new file with the
1291 1303 specified name is then created. This allows ld to create a new version
1292 1304 of the file, while simultaneously allowing existing processes that are
1293 1305 accessing the old file contents to continue running. If the old file
1294 1306 has no other links, the disk space of the removed file is freed when
1295 1307 the last process referencing the file terminates.
1296 1308
1297 1309
1298 1310 The behavior of ld when the file being created already exists was
1299 1311 changed with SXCE build 43. In older versions, the existing file was
1300 1312 rewritten in place, an approach with the potential to corrupt any
1301 1313 running processes that is using the file. This change has an
1302 1314 implication for output files that have multiple hard links in the file
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1303 1315 system. Previously, all links would remain intact, with all links
1304 1316 accessing the new file contents. The new ld behavior breaks such links,
1305 1317 with the result that only the specified output file name references the
1306 1318 new file. All the other links continue to reference the old file. To
1307 1319 ensure consistent behavior, applications that rely on multiple hard
1308 1320 links to linker output files should explicitly remove and relink the
1309 1321 other file names.
1310 1322
1311 1323
1312 1324
1313 - September 10, 2013 LD(1)
1325 + June 6, 2016 LD(1)
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