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1 .\" Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
2 .\" See https://llvm.org/LICENSE.txt for license information.
3 .\" SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
4 .\"
5 .\" This man page documents only lld's ELF linking support, obtained originally
6 .\" from FreeBSD.
7 .Dd Jul 25, 2023
8 .Dt LD.LLD 1
9 .Os
10 .Sh NAME
11 .Nm ld.lld
12 .Nd ELF linker from the LLVM project
13 .Sh SYNOPSIS
14 .Nm ld.lld
15 .Op Ar options
16 .Ar objfile ...
17 .Sh DESCRIPTION
18 A linker takes one or more object, archive, and library files, and combines
19 them into an output file (an executable, a shared library, or another object
20 file).
21 It relocates code and data from the input files and resolves symbol
22 references between them.
23 .Pp
24 .Nm
25 is a drop-in replacement for the GNU BFD and gold linkers.
26 It accepts most of the same command line arguments and linker scripts
27 as GNU linkers.
28 .Pp
29 .Nm
30 currently supports i386, x86-64, ARM, AArch64, LoongArch, PowerPC32,
31 PowerPC64, MIPS32, MIPS64, RISC-V, AMDGPU, Hexagon and SPARC V9 targets.
32 .Nm
33 acts as a Microsoft link.exe-compatible linker if invoked as
34 .Nm lld-link
35 and as macOS's ld if invoked as
36 .Nm ld.ld64.
37 All these targets are always supported however
38 .Nm
39 was built, so you can always use
40 .Nm
41 as a native linker as well as a cross linker.
42 .Sh OPTIONS
43 Many options have both a single-letter and long form.
44 When using the long form options other than those beginning with the
45 letter
46 .Cm o
47 may be specified using either one or two dashes preceding the option name.
48 Long options beginning with
49 .Cm o
50 require two dashes to avoid confusion with the
51 .Fl o Ar path
52 option.
53 .Pp
54 .Bl -tag -width indent
55 .It Fl -allow-multiple-definition
56 Do not error if a symbol is defined multiple times.
57 The first definition will be used.
58 .It Fl -allow-shlib-undefined
59 Allow unresolved references in shared libraries.
60 This option is enabled by default when linking a shared library.
61 .It Fl -apply-dynamic-relocs
62 Apply link-time values for dynamic relocations.
63 .It Fl -as-needed
64 Only set
65 .Dv DT_NEEDED
66 for shared libraries if used.
67 .It Fl -auxiliary Ns = Ns Ar value
68 Set the
69 .Dv DT_AUXILIARY
70 field to the specified name.
71 .It Fl -Bdynamic , Fl -dy
72 Link against shared libraries.
73 .It Fl -Bstatic , Fl -static , Fl -dn
74 Do not link against shared libraries.
75 .It Fl Bno-symbolic
76 Don't bind default visibility defined symbols locally for
77 .Fl shared
78 (default).
79 .It Fl Bsymbolic
80 Bind default visibility defined symbols locally for
81 .Fl shared.
82 Also set the
83 .Dv DF_SYMBOLIC
84 flag.
85 .It Fl Bsymbolic-non-weak
86 Bind default visibility defined STB_GLOBAL symbols locally for
87 .Fl shared.
88 .It Fl Bsymbolic-functions
89 Bind default visibility defined function symbols locally for
90 .Fl shared.
91 .It Fl Bsymbolic-non-weak-functions
92 Bind default visibility defined STB_GLOBAL function symbols locally for
93 .Fl shared.
94 .It Fl --be8
95 Write a Big Endian ELF File using BE8 format(AArch32 only)
96 .It Fl -build-id Ns = Ns Ar value
97 Generate a build ID note.
98 .Ar value
99 may be one of
100 .Cm fast ,
101 .Cm md5 ,
102 .Cm sha1 ,
103 .Cm tree ,
104 .Cm uuid ,
105 .Cm 0x Ns Ar hex-string ,
106 and
107 .Cm none .
108 .Cm tree
109 is an alias for
110 .Cm sha1 .
111 Build-IDs of type
112 .Cm fast ,
113 .Cm md5 ,
114 .Cm sha1 ,
115 and
116 .Cm tree
117 are calculated from the object contents.
118 .Cm fast
119 is not intended to be cryptographically secure.
120 .It Fl -build-id
121 Synonym for
122 .Fl -build-id Ns = Ns Cm sha1 .
123 .It Fl -call-graph-profile-sort Ns = Ns Ar algorithm
124 .Ar algorithm
125 may be:
126 .Pp
127 .Bl -tag -width 2n -compact
128 .It Cm none
129 Ignore call graph profile.
130 .It Cm hfsort
131 Use hfsort.
132 .It Cm cdsort
133 Use cdsort (default).
134 .El
135 .Pp
136 .It Fl -color-diagnostics Ns = Ns Ar value
137 Use colors in diagnostics.
138 .Ar value
139 may be one of
140 .Cm always ,
141 .Cm auto ,
142 and
143 .Cm never .
144 .Cm auto
145 enables color if and only if output is to a terminal.
146 .It Fl -color-diagnostics
147 Alias for
148 .Fl -color-diagnostics Ns = Ns Cm auto .
149 .It Fl -compress-debug-sections Ns = Ns Ar value
150 Compress DWARF debug sections.
151 The sections remain uncompressed if compressed content would be larger.
152 .Cm value
153 may be
154 .Pp
155 .Bl -tag -width 2n -compact
156 .It Cm none
157 No compression.
158 .It Cm zlib
159 The default compression level is 1 (fastest) as the debug info usually
160 compresses well at that level.
161 .It Cm zstd
162 Use the default compression level in zstd.
163 .El
164 .Pp
165 .It Fl -compress-sections Ns = Ns Ar section-glob={none,zlib,zstd}[:level]
166 Compress output sections that match the glob and do not have the SHF_ALLOC flag.
167 The matched sections remain uncompressed if compressed content would be larger.
168 The compression level is
169 .Cm level
170 (if specified) or a default speed-focused level.
171 This is like a generalized
172 .Cm --compress-debug-sections.
173 .It Fl -cref
174 Output cross reference table. If
175 .Fl Map
176 is specified, print to the map file.
177 .It Fl -debug-names
178 Generate a merged
179 .Li .debug_names
180 section.
181 .It Fl -default-script Ns = Ns Ar file , Fl dT Ar file
182 In the absence of
183 .Fl -script ,
184 read this default linker script.
185 .It Fl -defsym Ns = Ns Ar symbol Ns = Ns Ar expression
186 Define a symbol alias.
187 .Ar expression
188 may be another symbol or a linker script expression.
189 For example,
190 .Ql --defsym=foo=bar
191 or
192 .Ql --defsym=foo=bar+0x100 .
193 .It Fl -demangle
194 Demangle symbol names.
195 .It Fl -disable-new-dtags
196 Disable new dynamic tags.
197 .It Fl -discard-all , Fl x
198 Delete all local symbols.
199 .It Fl -discard-locals , Fl X
200 Delete temporary local symbols.
201 .It Fl -discard-none
202 Keep all symbols in the symbol table.
203 .It Fl -dynamic-linker Ns = Ns Ar value
204 Specify the dynamic linker to be used for a dynamically linked executable.
205 This is recorded in an ELF segment of type
206 .Dv PT_INTERP .
207 .It Fl -dynamic-list Ns = Ns Ar file
208 Similar to
209 .Cm --export-dynamic-symbol-list .
210 When creating a shared object, implies
211 .Cm -Bsymbolic
212 but does not set DF_SYMBOLIC
213 .It Fl -EB
214 Select the big-endian format in the OUTPUT_FORMAT command.
215 .It Fl -EL
216 Select the little-endian format in the OUTPUT_FORMAT command.
217 .It Fl -eh-frame-hdr
218 Request creation of
219 .Li .eh_frame_hdr
220 section and
221 .Dv PT_GNU_EH_FRAME
222 segment header.
223 .It Fl -emit-relocs , Fl q
224 Generate relocations in the output.
225 .It Fl -enable-new-dtags
226 Enable new dynamic tags.
227 .It Fl -enable-non-contiguous-regions
228 Spill input sections to later matching output sections to avoid memory region overflow.
229 .It Fl -end-lib
230 End a grouping of objects that should be treated as if they were together
231 in an archive.
232 .It Fl -entry Ns = Ns Ar entry
233 Name of entry point symbol.
234 .It Fl -error-limit Ns = Ns Ar value
235 Maximum number of errors to emit before stopping.
236 A value of zero indicates that there is no limit.
237 .It Fl -error-unresolved-symbols
238 Report unresolved symbols as errors.
239 .It Fl -error-handing-script Ns = Ns Ar script_path
240 Call script
241 .Ar script_path
242 upon some error, with
243 .Ar tag
244 as first argument, and an extra parameter as second argument. The script is
245 expected to return 0 on success. Any other value is considered a generic error.
246 .Ar tag
247 may be
248 .Cm missing-lib
249 followed by the name of the missing library.
250 .Cm undefined-symbol
251 followed by the name of the undefined symbol.
252 .It Fl -execute-only
253 Mark executable sections unreadable.
254 This option is currently only supported on AArch64.
255 .It Fl -exclude-libs Ns = Ns Ar value
256 Exclude static libraries from automatic export.
257 .It Fl -export-dynamic , Fl E
258 Put symbols in the dynamic symbol table.
259 .It Fl -export-dynamic-symbol Ns = Ns Ar glob
260 (executable) Put matched non-local defined symbols to the dynamic symbol table.
261 (shared object) References to matched non-local STV_DEFAULT symbols shouldn't be bound to definitions within the shared object even if they would otherwise be due to
262 .Cm -Bsymbolic
263 ,
264 .Cm -Bsymbolic-functions
265 or
266 .Cm --dynamic-list
267 .It Fl -export-dynamic-symbol-list Ns = Ns Ar file
268 Read a list of dynamic symbol patterns from
269 .Ar file .
270 Apply
271 .Cm --export-dynamic-symbol
272 on each pattern.
273 .It Fl -fatal-warnings
274 Treat warnings as errors.
275 .It Fl -filter Ns = Ns Ar value , Fl F Ar value
276 Set the
277 .Dv DT_FILTER
278 field to the specified value.
279 .It Fl -fini Ns = Ns Ar symbol
280 Specify a finalizer function.
281 .It Fl -force-group-allocation
282 Only meaningful for -r. Section groups are discarded. If two section group members are placed to the same output section, combine their relocations as well.
283 .It Fl -format Ns = Ns Ar input-format , Fl b Ar input-format
284 Specify the format of the inputs following this option.
285 .Ar input-format
286 may be one of
287 .Cm binary ,
288 .Cm elf ,
289 and
290 .Cm default .
291 .Cm default
292 is a synonym for
293 .Cm elf .
294 .It Fl -gc-sections
295 Enable garbage collection of unused sections.
296 .It Fl -gdb-index
297 Generate
298 .Li .gdb_index
299 section.
300 .It Fl -hash-style Ns = Ns Ar value
301 Specify hash style.
302 .Ar value
303 may be
304 .Cm sysv ,
305 .Cm gnu ,
306 or
307 .Cm both .
308 .Cm both
309 is the default.
310 .It Fl -help
311 Print a help message.
312 .It Fl -icf Ns = Ns Cm all
313 Enable identical code folding.
314 .It Fl -icf Ns = Ns Cm safe
315 Enable safe identical code folding.
316 .It Fl -icf Ns = Ns Cm none
317 Disable identical code folding.
318 .It Fl -ignore-data-address-equality
319 Ignore address equality of data. C/C++ requires each data to have a unique
320 address.
321 This option allows lld to do unsafe optimization that breaks the
322 requirement: create copies of read-only data or merge two or more read-only data
323 that happen to have the same value.
324 .It Fl -ignore-function-address-equality
325 Ignore address equality of functions.
326 This option allows non-PIC calls to a function with non-default visibility in
327 a shared object.
328 The function may have different addresses within the executable and within the
329 shared object.
330 .It Fl -image-base Ns = Ns Ar value
331 Set the base address to
332 .Ar value .
333 .It Fl -init Ns = Ns Ar symbol
334 Specify an initializer function.
335 .It Fl -keep-unique Ns = Ns Ar symbol
336 Do not fold
337 .Ar symbol
338 during ICF.
339 .It Fl l Ar libName, Fl -library Ns = Ns Ar libName
340 Root name of library to use.
341 .It Fl L Ar dir , Fl -library-path Ns = Ns Ar dir
342 Add a directory to the library search path.
343 .It Fl -lto-aa-pipeline Ns = Ns Ar value
344 AA pipeline to run during LTO.
345 Used in conjunction with
346 .Fl -lto-newpm-passes .
347 .It Fl -lto-newpm-passes Ns = Ns Ar value
348 Passes to run during LTO.
349 .It Fl -lto-O Ns Ar opt-level
350 Optimization level for LTO.
351 .It Fl -lto-partitions Ns = Ns Ar value
352 Number of LTO codegen partitions.
353 .It Fl m Ar value
354 Set target emulation.
355 .It Fl -Map Ns = Ns Ar file , Fl M Ar file
356 Print a link map to
357 .Ar file .
358 .It Fl -nmagic , Fl n
359 Do not page align sections, link against static libraries.
360 .It Fl -no-allow-shlib-undefined
361 Do not allow unresolved references in shared libraries.
362 This option is enabled by default when linking an executable.
363 .It Fl -no-as-needed
364 Always set
365 .Dv DT_NEEDED
366 for shared libraries.
367 .It Fl -no-color-diagnostics
368 Do not use colors in diagnostics.
369 .It Fl -no-demangle
370 Do not demangle symbol names.
371 .It Fl -no-dynamic-linker
372 Inhibit output of an
373 .Li .interp
374 section.
375 .It Fl -no-fortran-common
376 Do not search archive members for definitions to override COMMON symbols.
377 .It Fl -no-gc-sections
378 Disable garbage collection of unused sections.
379 .It Fl -no-gnu-unique
380 Disable STB_GNU_UNIQUE symbol binding.
381 .It Fl -no-merge-exidx-entries
382 Disable merging .ARM.exidx entries.
383 .It Fl -no-nmagic
384 Page align sections.
385 .It Fl -no-omagic
386 Do not set the text data sections to be writable, page align sections.
387 .It Fl -no-relax
388 Disable target-specific relaxations. For x86-64 this disables R_X86_64_GOTPCRELX and R_X86_64_REX_GOTPCRELX GOT optimization.
389 .It Fl -no-rosegment
390 Do not put read-only non-executable sections in their own segment.
391 .It Fl -undefined-version
392 Do not report version scripts that refer to undefined symbols.
393 .It Fl -no-undefined
394 Report unresolved symbols even if the linker is creating a shared library.
395 .It Fl -no-warn-mismatch
396 Do not reject unknown section types.
397 .It Fl -no-warn-symbol-ordering
398 Do not warn about problems with the symbol ordering file or call graph profile.
399 .It Fl -no-warnings , Fl w
400 Suppress warnings and cancel
401 .Cm --fatal-warnings.
402 .It Fl -no-whole-archive
403 Restores the default behavior of loading archive members.
404 .It Fl -no-pie , Fl -no-pic-executable
405 Do not create a position independent executable.
406 .It Fl -noinhibit-exec
407 Retain the executable output file whenever it is still usable.
408 .It Fl -nostdlib
409 Only search directories specified on the command line.
410 .It Fl o Ar path
411 Write the output executable, library, or object to
412 .Ar path .
413 If not specified,
414 .Dv a.out
415 is used as a default.
416 .It Fl O Ns Ar value
417 Optimize output file size.
418 .Ar value
419 may be:
420 .Pp
421 .Bl -tag -width 2n -compact
422 .It Cm 0
423 Disable string merging.
424 .It Cm 1
425 Enable string merging.
426 .It Cm 2
427 Enable string tail merging.
428 .El
429 .Pp
430 .Fl O Ns Cm 1
431 is the default.
432 .It Fl -oformat Ns = Ns Ar format
433 Specify the format for the output object file.
434 The only supported
435 .Ar format
436 is
437 .Cm binary ,
438 which produces output with no ELF header.
439 .It Fl -omagic , Fl N
440 Set the text and data sections to be readable and writable, do not page align
441 sections, link against static libraries.
442 .It Fl -opt-remarks-filename Ar file
443 Write optimization remarks in YAML format to
444 .Ar file .
445 .It Fl -opt-remarks-passes Ar pass-regex
446 Filter optimization remarks by only allowing the passes matching
447 .Ar pass-regex .
448 .It Fl -opt-remarks-with-hotness
449 Include hotness information in the optimization remarks file.
450 .It Fl -orphan-handling Ns = Ns Ar mode
451 Control how orphan sections are handled.
452 An orphan section is one not specifically mentioned in a linker script.
453 .Ar mode
454 may be:
455 .Pp
456 .Bl -tag -width 2n -compact
457 .It Cm place
458 Place orphan sections in suitable output sections.
459 .It Cm warn
460 Place orphan sections as for
461 .Cm place
462 and also report a warning.
463 .It Cm error
464 Place orphan sections as for
465 .Cm place
466 and also report an error.
467 .El
468 .Pp
469 .Cm place
470 is the default.
471 .It Fl -pack-dyn-relocs Ns = Ns Ar format
472 Pack dynamic relocations in the given format.
473 .Ar format
474 may be:
475 .Pp
476 .Bl -tag -width 2n -compact
477 .It Cm none
478 Do not pack.
479 Dynamic relocations are encoded in SHT_REL(A).
480 .It Cm android
481 Pack dynamic relocations in SHT_ANDROID_REL(A).
482 .It Cm relr
483 Pack relative relocations in SHT_RELR, and the rest of dynamic relocations in
484 SHT_REL(A).
485 .It Cm android+relr
486 Pack relative relocations in SHT_RELR, and the rest of dynamic relocations in
487 SHT_ANDROID_REL(A).
488 .El
489 .Pp
490 .Cm none
491 is the default.
492 If
493 .Fl -use-android-relr-tags
494 is specified, use SHT_ANDROID_RELR instead of SHT_RELR.
495 .Pp
496 .It Fl -pic-veneer
497 Always generate position independent thunks.
498 .It Fl -pie , Fl -pic-executable
499 Create a position independent executable.
500 .It Fl -power10-stubs Ns = Ns Cm mode
501 Whether to use Power10 instructions in call stubs for R_PPC64_REL24_NOTOC and TOC/NOTOC interworking.
502 .Ar mode
503 may be:
504 .Pp
505 .Bl -tag -width 2n -compact
506 .It Cm yes
507 (default) Use.
508 .It Cm auto
509 Currently the same as yes.
510 .It Cm no
511 Don't use.
512 .El
514 .It Fl -print-gc-sections
515 List removed unused sections.
516 .It Fl -print-icf-sections
517 List identical folded sections.
518 .It Fl -print-map
519 Print a link map to the standard output.
520 .It Fl -print-archive-stats Ns = Ns Ar file
521 Write archive usage statistics to the specified file.
522 Print the numbers of members and fetched members for each archive.
523 .It Fl -push-state
524 Save the current state of
525 .Fl -as-needed ,
526 .Fl -static ,
527 and
528 .Fl -whole-archive.
529 .It Fl -pop-state
530 Restore the states saved by
531 .Fl -push-state.
532 .It Fl -randomize-section-padding Ns = Ns Ar seed
533 Randomly insert padding between input sections and at the start of each segment using the given seed.
534 Padding is inserted into output sections with names matching the following patterns:
535 .Cm .bss ,
536 .Cm .data ,
537 .Cm .data.rel.ro ,
538 .Cm .lbss ,
539 .Cm .ldata ,
540 .Cm .lrodata ,
541 .Cm .ltext ,
542 .Cm .rodata
543 and
544 .Cm .text* .
545 .It Fl --relax-gp
546 Enable global pointer relaxation for RISC-V.
547 .It Fl -relocatable , Fl r
548 Create relocatable object file.
549 .It Fl -remap-inputs Ns = Ns Ar from-glob=to-file
550 Input files matching
551 .Cm from-glob
552 are mapped to
553 .Cm to-file.
554 Use
555 .Cm /dev/null
556 to ignore an input file.
557 .It Fl -remap-inputs-file Ns = Ns Ar file
558 Remap input files based on patterns in
559 .Ar file .
560 Each line in the remap file is of the format
561 .Cm from-glob=to-file
562 or a comment starting with
563 .Cm # .
564 .It Fl -reproduce Ns = Ns Ar path
565 Write a tar file to
566 .Ar path,
567 containing all the input files needed to reproduce the link, a text file called
568 response.txt containing the command line options and a text file called
569 version.txt containing the output of ld.lld --version.
570 The archive when
571 unpacked can be used to re-run the linker with the same options and input files.
572 .It Fl -retain-symbols-file Ns = Ns Ar file
573 Retain only the symbols listed in the file.
574 .It Fl -rpath Ns = Ns Ar value , Fl R Ar value
575 Add a
576 .Dv DT_RUNPATH
577 to the output.
578 .It Fl -rsp-quoting Ns = Ns Ar value
579 Quoting style for response files.
580 The supported values are
581 .Cm windows
582 and
583 .Cm posix .
584 .It Fl -script Ns = Ns Ar file , Fl T Ar file
585 Read linker script from
586 .Ar file .
587 If multiple linker scripts are given, they are processed as if they
588 were concatenated in the order they appeared on the command line.
589 .It Fl -section-start Ns = Ns Ar section Ns = Ns Ar address
590 Set address of section.
591 .It Fl -shared , Fl -Bsharable
592 Build a shared object.
593 .It Fl -shuffle-sections Ns = Ns Ar seed
594 Shuffle matched sections using the given seed before mapping them to the output sections.
595 If -1, reverse the section order. If 0, use a random seed.
596 .It Fl -soname Ns = Ns Ar value , Fl h Ar value
597 Set
598 .Dv DT_SONAME
599 to
600 .Ar value .
601 .It Fl -sort-common
602 This option is ignored for GNU compatibility.
603 .It Fl -sort-section Ns = Ns Ar value
604 Specifies sections sorting rule when linkerscript is used.
605 .It Fl -start-lib
606 Start a grouping of objects that should be treated as if they were together
607 in an archive.
608 .It Fl -strip-all , Fl s
609 Strip all symbols.
610 Implies
611 .Fl -strip-debug .
612 .It Fl -strip-debug , Fl S
613 Strip debugging information.
614 .It Fl -symbol-ordering-file Ns = Ns Ar file
615 Lay out sections in the order specified by
616 .Ar file .
617 .It Fl -sysroot Ns = Ns Ar value
618 Set the system root.
619 .It Fl -target1-abs
620 Interpret
621 .Dv R_ARM_TARGET1
622 as
623 .Dv R_ARM_ABS32 .
624 .It Fl -target1-rel
625 Interpret
626 .Dv R_ARM_TARGET1
627 as
628 .Dv R_ARM_REL32 .
629 .It Fl -target2 Ns = Ns Ar type
630 Interpret
631 .Dv R_ARM_TARGET2
632 as
633 .Ar type ,
634 where
635 .Ar type
636 is one of
637 .Cm rel ,
638 .Cm abs ,
639 or
640 .Cm got-rel .
641 .It Fl -Tbss Ns = Ns Ar value
642 Same as
643 .Fl -section-start
644 with
645 .Li .bss
646 as the sectionname.
647 .It Fl -Tdata Ns = Ns Ar value
648 Same as
649 .Fl -section-start
650 with
651 .Li .data
652 as the sectionname.
653 .It Fl -Ttext Ns = Ns Ar value
654 Same as
655 .Fl -section-start
656 with
657 .Li .text
658 as the sectionname.
659 .It Fl -thinlto-cache-dir Ns = Ns Ar value
660 Path to ThinLTO cached object file directory.
661 .It Fl -thinlto-cache-policy Ns = Ns Ar value
662 Pruning policy for the ThinLTO cache.
663 .It Fl -thinlto-jobs Ns = Ns Ar value
664 Number of ThinLTO jobs.
665 .It Fl -threads Ns = Ns Ar N
666 Number of threads.
667 .Cm all
668 (default) means all of concurrent threads supported.
669 .Cm 1
670 disables multi-threading.
671 .It Fl -fat-lto-objects
672 Use the .llvm.lto section, which contains LLVM bitcode, in fat LTO object files to perform LTO.
673 .It Fl -no-fat-lto-objects
674 Ignore the .llvm.lto section in relocatable object files (default).
675 .It Fl -time-trace
676 Record time trace.
677 .It Fl -time-trace-file Ns = Ns Ar file
678 Write time trace output to
679 .Ar file .
680 .It Fl -time-trace-granularity Ns = Ns Ar value
681 Minimum time granularity (in microseconds) traced by time profiler.
682 .It Fl -trace
683 Print the names of the input files.
684 .It Fl -trace-symbol Ns = Ns Ar symbol , Fl y Ar symbol
685 Trace references to
686 .Ar symbol .
687 .It Fl -undefined Ns = Ns Ar symbol , Fl u Ar symbol
688 If
689 .Ar symbol
690 is not defined after symbol resolution, and there's a static library
691 that contains an object file defining the symbol, load the member
692 to include the object file in the output file.
693 .It Fl -undefined-glob Ns = Ns Ar pattern
694 Synonym for
695 .Fl -undefined ,
696 except that it takes a glob pattern.
697 In a glob pattern,
698 .Cm *
699 matches zero or more characters,
700 .Cm ?
701 matches any single character, and
702 .Cm [...]
703 matches the characters within brackets.
704 All symbols that match
705 a given pattern are handled as if they were given as arguments of
706 .Fl -undefined .
707 .It Fl -unique
708 Creates a separate output section for every orphan input section.
709 .It Fl -unresolved-symbols Ns = Ns Ar value
710 Determine how to handle unresolved symbols.
711 .It Fl -use-android-relr-tags
712 Use SHT_ANDROID_RELR / DT_ANDROID_RELR* tags instead of SHT_RELR / DT_RELR*.
713 .It Fl v , Fl V
714 Display the version number and proceed with linking if object files are
715 specified.
716 .It Fl -version
717 Display the version number and exit.
718 .It Fl -verbose
719 Verbose mode.
720 .It Fl -version-script Ns = Ns Ar file
721 Read version script from
722 .Ar file .
723 .It Fl -warn-backrefs
724 Warn about reverse or cyclic dependencies to or between static archives.
725 This can be used to ensure linker invocation remains compatible with
726 traditional Unix-like linkers.
727 .It Fl -warn-backrefs-exclude Ns = Ns Ar glob
728 Glob describing an archive (or an object file within --start-lib)
729 which should be ignored for
730 .Fl -warn-backrefs
731 .It Fl -warn-common
732 Warn about duplicate common symbols.
733 .It Fl -warn-ifunc-textrel
734 Warn about using ifunc symbols in conjunction with text relocations.
735 Older versions of glibc library (2.28 and earlier) has a bug that causes
736 the segment that includes ifunc symbols to be marked as not executable when
737 they are relocated.
738 As a result, although the program compiles and links
739 successfully, it gives segmentation fault when the instruction pointer reaches
740 an ifunc symbol.
741 Use -warn-ifunc-textrel to let lld give a warning, if the
742 code may include ifunc symbols, may do text relocations and be linked with
743 an older glibc version.
744 Otherwise, there is no need to use it, as the default value does not give a
745 warning.
746 This flag has been introduced in late 2018, has no counter part in ld and gold
747 linkers, and may be removed in the future.
748 .It Fl -warn-unresolved-symbols
749 Report unresolved symbols as warnings.
750 .It Fl -whole-archive
751 Force load of all members in a static library.
752 .It Fl -why-extract Ns = Ns Ar file
753 Print to a file about why archive members are extracted.
754 .It Fl -wrap Ns = Ns Ar symbol
755 Redirect
756 .Ar symbol
757 references to
758 .Ar __wrap_symbol
759 and
760 .Ar __real_symbol
761 references to
762 .Ar symbol.
763 .It Fl z Ar option
764 Linker option extensions.
765 .Bl -tag -width indent -compact
766 .Pp
767 .It Cm dead-reloc-in-nonalloc Ns = Ns Ar section_glob=value
768 Resolve a relocation in a matched non-SHF_ALLOC section referencing a discarded symbol to
769 .Ar value
770 Accepts globs, in the event of a section matching more than one option, the last
771 option takes precedence. An order of least specific to most specific match is
772 recommended.
773 .Pp
774 .It Cm execstack
775 Make the main stack executable.
776 Stack permissions are recorded in the
777 .Dv PT_GNU_STACK
778 segment.
779 .Pp
780 .It Cm bti-report Ns = Ns Ar [none|warning|error]
781 Specify how to report the missing GNU_PROPERTY_AARCH64_FEATURE_1_BTI property.
782 .Cm none
783 is the default, linker will not report the missing property otherwise will be reported as a warning or an error.
784 .Pp
785 .It Cm cet-report Ns = Ns Ar [none|warning|error]
786 Specify how to report the missing GNU_PROPERTY_X86_FEATURE_1_IBT or GNU_PROPERTY_X86_FEATURE_1_SHSTK properties.
787 .Cm none
788 is the default, linker will not report the missing property otherwise will be reported as a warning or an error.
789 .Pp
790 .It Cm pauth-report Ns = Ns Ar [none|warning|error]
791 Specify how to report the missing GNU_PROPERTY_AARCH64_FEATURE_PAUTH property.
792 .Cm none
793 is the default, linker will not report the missing property otherwise will be reported as a warning or an error.
794 .Pp
795 .It Cm force-bti
796 Force enable AArch64 BTI instruction in PLT, warn if Input ELF file does not have GNU_PROPERTY_AARCH64_FEATURE_1_BTI property.
797 .Pp
798 .It Cm force-ibt
799 Force enable Intel Indirect Branch Tracking in PLT, warn if an input ELF file
800 does not have GNU_PROPERTY_X86_FEATURE_1_IBT property.
801 .Pp
802 .It Cm global
803 Sets the
804 .Dv DF_1_GLOBAL flag in the
805 .Dv DYNAMIC
806 section.
807 Different loaders can decide how to handle this flag on their own.
808 .Pp
809 .It Cm ifunc-noplt
810 Do not emit PLT entries for ifunc symbols.
811 Instead, emit text relocations referencing the resolver.
812 This is an experimental optimization and only suitable for standalone
813 environments where text relocations do not have the usual drawbacks.
814 This option must be combined with the
815 .Fl z Li notext
816 option.
817 .Pp
818 .It Cm initfirst
819 Sets the
820 .Dv DF_1_INITFIRST
821 flag to indicate the module should be initialized first.
822 .Pp
823 .It Cm interpose
824 Set the
825 .Dv DF_1_INTERPOSE
826 flag to indicate to the runtime linker that the object is an interposer.
827 During symbol resolution interposers are searched after the application
828 but before other dependencies.
829 .Pp
830 .It Cm lrodata-after-bss
831 Place .lrodata after .bss.
832 .Pp
833 .It Cm muldefs
834 Do not error if a symbol is defined multiple times.
835 The first definition will be used.
836 This is a synonym for
837 .Fl -allow-multiple-definition.
838 .Pp
839 .It Cm nocombreloc
840 Disable combining and sorting multiple relocation sections.
841 .Pp
842 .It Cm nocopyreloc
843 Disable the creation of copy relocations.
844 .Pp
845 .It Cm nodefaultlib
846 Set the
847 .Dv DF_1_NODEFLIB
848 flag to indicate that default library search paths should be ignored.
849 .Pp
850 .It Cm nodelete
851 Set the
852 .Dv DF_1_NODELETE
853 flag to indicate that the object cannot be unloaded from a process.
854 .Pp
855 .It Cm nodlopen
856 Set the
857 .Dv DF_1_NOOPEN
858 flag to indicate that the object may not be opened by
859 .Xr dlopen 3 .
860 .Pp
861 .It Cm nognustack
862 Do not emit the
863 .Dv PT_GNU_STACK
864 segment.
865 .Pp
866 .It Cm norelro
867 Do not indicate that portions of the object should be mapped read-only
868 after initial relocation processing.
869 The object will omit the
870 .Dv PT_GNU_RELRO
871 segment.
872 .Pp
873 .It Cm nosectionheader
874 Don't generate the section header table.
875 .Pp
876 .It Cm notext
877 Allow relocations against read-only segments.
878 Sets the
879 .Dv DT_TEXTREL flag in the
880 .Dv DYNAMIC
881 section.
882 .Pp
883 .It Cm now
884 Set the
885 .Dv DF_BIND_NOW
886 flag to indicate that the run-time loader should perform all relocation
887 processing as part of object initialization.
888 By default relocations may be performed on demand.
889 .Pp
890 .It Cm origin
891 Set the
892 .Dv DF_ORIGIN
893 flag to indicate that the object requires
894 $ORIGIN
895 processing.
896 .Pp
897 .It Cm pac-plt
898 AArch64 only, use pointer authentication in PLT.
899 .Pp
900 .It Cm pack-relative-relocs
901 Similar to
902 .Cm -pack-dyn-relocs=relr
903 , but synthesizes the GLIBC_ABI_DT_RELR version dependency if there is a GLIBC_2.* version dependency.
904 glibc ld.so rejects loading a dynamically linked object without the GLIBC_ABI_DT_RELR version dependency.
905 .Pp
906 .It Cm rel
907 Use REL format for dynamic relocations.
908 .Pp
909 .It Cm rela
910 Use RELA format for dynamic relocations.
911 .Pp
912 .It Cm retpolineplt
913 Emit retpoline format PLT entries as a mitigation for CVE-2017-5715.
914 .Pp
915 .It Cm rodynamic
916 Make the
917 .Li .dynamic
918 section read-only.
919 The
920 .Dv DT_DEBUG
921 tag will not be emitted.
922 .Pp
923 .It Cm separate-loadable-segments
924 .It Cm separate-code
925 .It Cm noseparate-code
926 Specify whether two adjacent PT_LOAD segments are allowed to overlap in pages.
927 .Cm noseparate-code
928 (default) allows overlap.
929 .Cm separate-code
930 allows overlap between two executable segments, or two non-executable segments.
931 .Cm separate-loadable-segments
932 disallows overlap.
933 .Pp
934 .It Cm shstk
935 x86 only, use shadow stack.
936 .Pp
937 .It Cm stack-size Ns = Ns Ar size
938 Set the main thread's stack size to
939 .Ar size .
940 The stack size is recorded as the size of the
941 .Ar size .
942 .Dv PT_GNU_STACK
943 program segment.
944 .Pp
945 .It Cm start-stop-gc
946 Don't let __start_/__stop_ references retain the associated C identifier name sections (default).
947 .Pp
948 .It Cm nostart-stop-gc
949 Let __start_/__stop_ references retain the associated C identifier name sections.
950 .Pp
951 .It Cm text
952 Do not allow relocations against read-only segments.
953 This is the default.
954 .Pp
955 .It Cm nobtcfi
956 Create a
957 .Dv PT_OPENBSD_NOBTCFI
958 segment.
959 .Pp
960 .It Cm wxneeded
961 Create a
962 .Dv PT_OPENBSD_WXNEEDED
963 segment.
964 .El
965 .El
967 .Sh ENVIRONMENT VARIABLES
968 .Bl -tag -width LC_CTYPE
969 .It Ev LLD_REPRODUCE
970 Create a reproduce tarball with the specified filename. If
971 .Fl -reproduce
972 is specified,
973 .Fl -reproduce
974 takes precedence.
975 .It Ev LLD_VERSION
976 ld.lld creates a section named
977 .Cm .comment
978 containing the LLD version string. The version string can be overridden by this environment variable,
979 which is useful to eliminate differences in the binary caused by LLD version number differences.
980 .El
982 .Sh IMPLEMENTATION NOTES
983 .Nm Ap s
984 handing of archive files (those with a
985 .Pa .a
986 file extension) is different from traditional linkers used on Unix-like
987 systems.
988 .Pp
989 Traditional linkers maintain a set of undefined symbols during linking.
990 The linker processes each file in the order in which it appears on the
991 command line, until the set of undefined symbols becomes empty.
992 An object file is linked into the output object when it is encountered,
993 with its undefined symbols added to the set.
994 Upon encountering an archive file a traditional linker searches the objects
995 contained therein, and processes those that satisfy symbols in the unresolved
996 set.
997 .Pp
998 Handling mutually dependent archives may be awkward when using a traditional
999 linker.
1000 Archive files may have to be specified multiple times, or the special command
1001 line options
1002 .Fl -start-group
1003 and
1004 .Fl -end-group
1005 may be used to have the linker loop over the files in the group until no new
1006 symbols are added to the set.
1007 .Pp
1008 .Nm
1009 records all symbols found in objects and archives as it iterates over
1010 command line arguments.
1011 When
1012 .Nm
1013 encounters an undefined symbol that can be resolved by an object file
1014 contained in a previously processed archive file, it immediately extracts
1015 and links it into the output object.
1016 .Pp
1017 With certain archive inputs
1018 .Nm
1019 may produce different results compared to traditional linkers.
1020 In practice, large bodies of third party software have been linked with
1021 .Nm
1022 without material issues.
1023 .Pp
1024 The
1025 .Fl -warn-backrefs
1026 option may be used to identify a linker invocation that may be incompatible
1027 with traditional Unix-like linker behavior.