1//===- Symbols.cpp --------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "Symbols.h"
10#include "Driver.h"
11#include "InputFiles.h"
12#include "InputSection.h"
13#include "OutputSections.h"
14#include "SymbolTable.h"
15#include "SyntheticSections.h"
16#include "Target.h"
17#include "Writer.h"
18#include "llvm/Demangle/Demangle.h"
19#include "llvm/Support/Compiler.h"
20#include <cstring>
21
22using namespace llvm;
23using namespace llvm::object;
24using namespace llvm::ELF;
25using namespace lld;
26using namespace lld::elf;
27
28static_assert(sizeof(SymbolUnion) <= 64, "SymbolUnion too large");
29
30template <typename T> struct AssertSymbol {
31 static_assert(std::is_trivially_destructible<T>(),
32 "Symbol types must be trivially destructible");
33 static_assert(sizeof(T) <= sizeof(SymbolUnion), "SymbolUnion too small");
34 static_assert(alignof(T) <= alignof(SymbolUnion),
35 "SymbolUnion not aligned enough");
36};
37
38LLVM_ATTRIBUTE_UNUSED static inline void assertSymbols() {
39 AssertSymbol<Defined>();
40 AssertSymbol<CommonSymbol>();
41 AssertSymbol<Undefined>();
42 AssertSymbol<SharedSymbol>();
43 AssertSymbol<LazySymbol>();
44}
45
46// Returns a symbol for an error message.
47static std::string maybeDemangleSymbol(Ctx &ctx, StringRef symName) {
48 return ctx.arg.demangle ? demangle(MangledName: symName.str()) : symName.str();
49}
50
51std::string elf::toStr(Ctx &ctx, const elf::Symbol &sym) {
52 StringRef name = sym.getName();
53 std::string ret = maybeDemangleSymbol(ctx, symName: name);
54
55 const char *suffix = sym.getVersionSuffix();
56 if (*suffix == '@')
57 ret += suffix;
58 return ret;
59}
60
61const ELFSyncStream &elf::operator<<(const ELFSyncStream &s,
62 const Symbol *sym) {
63 return s << toStr(ctx&: s.ctx, sym: *sym);
64}
65
66static uint64_t getSymVA(Ctx &ctx, const Symbol &sym, int64_t addend) {
67 switch (sym.kind()) {
68 case Symbol::DefinedKind: {
69 auto &d = cast<Defined>(Val: sym);
70 SectionBase *isec = d.section;
71
72 // This is an absolute symbol.
73 if (!isec)
74 return d.value;
75
76 assert(isec != &InputSection::discarded);
77
78 uint64_t offset = d.value;
79
80 // An object in an SHF_MERGE section might be referenced via a
81 // section symbol (as a hack for reducing the number of local
82 // symbols).
83 // Depending on the addend, the reference via a section symbol
84 // refers to a different object in the merge section.
85 // Since the objects in the merge section are not necessarily
86 // contiguous in the output, the addend can thus affect the final
87 // VA in a non-linear way.
88 // To make this work, we incorporate the addend into the section
89 // offset (and zero out the addend for later processing) so that
90 // we find the right object in the section.
91 if (d.isSection())
92 offset += addend;
93
94 // In the typical case, this is actually very simple and boils
95 // down to adding together 3 numbers:
96 // 1. The address of the output section.
97 // 2. The offset of the input section within the output section.
98 // 3. The offset within the input section (this addition happens
99 // inside InputSection::getOffset).
100 //
101 // If you understand the data structures involved with this next
102 // line (and how they get built), then you have a pretty good
103 // understanding of the linker.
104 uint64_t va = isec->getVA(offset);
105 if (d.isSection())
106 va -= addend;
107
108 // MIPS relocatable files can mix regular and microMIPS code.
109 // Linker needs to distinguish such code. To do so microMIPS
110 // symbols has the `STO_MIPS_MICROMIPS` flag in the `st_other`
111 // field. Unfortunately, the `MIPS::relocate()` method has
112 // a symbol value only. To pass type of the symbol (regular/microMIPS)
113 // to that routine as well as other places where we write
114 // a symbol value as-is (.dynamic section, `Elf_Ehdr::e_entry`
115 // field etc) do the same trick as compiler uses to mark microMIPS
116 // for CPU - set the less-significant bit.
117 if (ctx.arg.emachine == EM_MIPS && isMicroMips(ctx) &&
118 ((sym.stOther & STO_MIPS_MICROMIPS) || sym.hasFlag(bit: NEEDS_COPY)))
119 va |= 1;
120
121 if (d.isTls() && !ctx.arg.relocatable) {
122 // Use the address of the TLS segment's first section rather than the
123 // segment's address, because segment addresses aren't initialized until
124 // after sections are finalized. (e.g. Measuring the size of .rela.dyn
125 // for Android relocation packing requires knowing TLS symbol addresses
126 // during section finalization.)
127 if (!ctx.tlsPhdr || !ctx.tlsPhdr->firstSec) {
128 Err(ctx) << d.file
129 << " has an STT_TLS symbol but doesn't have a PT_TLS segment";
130 return 0;
131 }
132 return va - ctx.tlsPhdr->firstSec->addr;
133 }
134 return va;
135 }
136 case Symbol::SharedKind:
137 case Symbol::UndefinedKind:
138 return 0;
139 case Symbol::LazyKind:
140 llvm_unreachable("lazy symbol reached writer");
141 case Symbol::CommonKind:
142 llvm_unreachable("common symbol reached writer");
143 case Symbol::PlaceholderKind:
144 llvm_unreachable("placeholder symbol reached writer");
145 }
146 llvm_unreachable("invalid symbol kind");
147}
148
149uint64_t Symbol::getVA(Ctx &ctx, int64_t addend) const {
150 return getSymVA(ctx, sym: *this, addend) + addend;
151}
152
153uint64_t Symbol::getGotVA(Ctx &ctx) const {
154 if (gotInIgot)
155 return ctx.in.igotPlt->getVA() + getGotPltOffset(ctx);
156 return ctx.in.got->getVA() + getGotOffset(ctx);
157}
158
159uint64_t Symbol::getGotOffset(Ctx &ctx) const {
160 return getGotIdx(ctx) * ctx.target->gotEntrySize;
161}
162
163uint64_t Symbol::getGotPltVA(Ctx &ctx) const {
164 if (isInIplt)
165 return ctx.in.igotPlt->getVA() + getGotPltOffset(ctx);
166 return ctx.in.gotPlt->getVA() + getGotPltOffset(ctx);
167}
168
169uint64_t Symbol::getGotPltOffset(Ctx &ctx) const {
170 if (isInIplt)
171 return getPltIdx(ctx) * ctx.target->gotEntrySize;
172 return (getPltIdx(ctx) + ctx.target->gotPltHeaderEntriesNum) *
173 ctx.target->gotEntrySize;
174}
175
176uint64_t Symbol::getPltVA(Ctx &ctx) const {
177 uint64_t outVA = isInIplt ? ctx.in.iplt->getVA() +
178 getPltIdx(ctx) * ctx.target->ipltEntrySize
179 : ctx.in.plt->getVA() + ctx.in.plt->headerSize +
180 getPltIdx(ctx) * ctx.target->pltEntrySize;
181
182 // While linking microMIPS code PLT code are always microMIPS
183 // code. Set the less-significant bit to track that fact.
184 // See detailed comment in the `getSymVA` function.
185 if (ctx.arg.emachine == EM_MIPS && isMicroMips(ctx))
186 outVA |= 1;
187 return outVA;
188}
189
190uint64_t Symbol::getSize() const {
191 if (const auto *dr = dyn_cast<Defined>(Val: this))
192 return dr->size;
193 return cast<SharedSymbol>(Val: this)->size;
194}
195
196OutputSection *Symbol::getOutputSection() const {
197 if (auto *s = dyn_cast<Defined>(Val: this)) {
198 if (auto *sec = s->section)
199 return sec->getOutputSection();
200 return nullptr;
201 }
202 return nullptr;
203}
204
205// If a symbol name contains '@', the characters after that is
206// a symbol version name. This function parses that.
207void Symbol::parseSymbolVersion(Ctx &ctx) {
208 // Return if localized by a local: pattern in a version script.
209 if (versionId == VER_NDX_LOCAL)
210 return;
211 StringRef s = getName();
212 size_t pos = s.find(C: '@');
213 if (pos == StringRef::npos)
214 return;
215 StringRef verstr = s.substr(Start: pos + 1);
216
217 // Truncate the symbol name so that it doesn't include the version string.
218 nameSize = pos;
219
220 if (verstr.empty())
221 return;
222
223 // If this is not in this DSO, it is not a definition.
224 if (!isDefined())
225 return;
226
227 // '@@' in a symbol name means the default version.
228 // It is usually the most recent one.
229 bool isDefault = (verstr[0] == '@');
230 if (isDefault)
231 verstr = verstr.substr(Start: 1);
232
233 for (const VersionDefinition &ver : namedVersionDefs(ctx)) {
234 if (ver.name != verstr)
235 continue;
236
237 if (isDefault)
238 versionId = ver.id;
239 else
240 versionId = ver.id | VERSYM_HIDDEN;
241 return;
242 }
243
244 // It is an error if the specified version is not defined.
245 // Usually version script is not provided when linking executable,
246 // but we may still want to override a versioned symbol from DSO,
247 // so we do not report error in this case. We also do not error
248 // if the symbol has a local version as it won't be in the dynamic
249 // symbol table.
250 if (ctx.arg.shared && versionId != VER_NDX_LOCAL)
251 ErrAlways(ctx) << file << ": symbol " << s << " has undefined version "
252 << verstr;
253}
254
255void Symbol::extract(Ctx &ctx) const {
256 assert(file->lazy);
257 file->lazy = false;
258 parseFile(ctx, file);
259}
260
261uint8_t Symbol::computeBinding(Ctx &ctx) const {
262 auto v = visibility();
263 if ((v != STV_DEFAULT && v != STV_PROTECTED) || versionId == VER_NDX_LOCAL)
264 return STB_LOCAL;
265 if (binding == STB_GNU_UNIQUE && !ctx.arg.gnuUnique)
266 return STB_GLOBAL;
267 return binding;
268}
269
270// Print out a log message for --trace-symbol.
271void elf::printTraceSymbol(const Symbol &sym, StringRef name) {
272 std::string s;
273 if (sym.isUndefined())
274 s = ": reference to ";
275 else if (sym.isLazy())
276 s = ": lazy definition of ";
277 else if (sym.isShared())
278 s = ": shared definition of ";
279 else if (sym.isCommon())
280 s = ": common definition of ";
281 else
282 s = ": definition of ";
283
284 Msg(ctx&: sym.file->ctx) << sym.file << s << name;
285}
286
287static void recordWhyExtract(Ctx &ctx, const InputFile *reference,
288 const InputFile &extracted, const Symbol &sym) {
289 ctx.whyExtractRecords.emplace_back(Args: toStr(ctx, f: reference), Args: &extracted, Args: sym);
290}
291
292void elf::maybeWarnUnorderableSymbol(Ctx &ctx, const Symbol *sym) {
293 if (!ctx.arg.warnSymbolOrdering)
294 return;
295
296 // If UnresolvedPolicy::Ignore is used, no "undefined symbol" error/warning is
297 // emitted. It makes sense to not warn on undefined symbols (excluding those
298 // demoted by demoteSymbols).
299 //
300 // Note, ld.bfd --symbol-ordering-file= does not warn on undefined symbols,
301 // but we don't have to be compatible here.
302 if (sym->isUndefined() && !cast<Undefined>(Val: sym)->discardedSecIdx &&
303 ctx.arg.unresolvedSymbols == UnresolvedPolicy::Ignore)
304 return;
305
306 const InputFile *file = sym->file;
307 auto *d = dyn_cast<Defined>(Val: sym);
308
309 auto report = [&](StringRef s) { Warn(ctx) << file << s << sym->getName(); };
310
311 if (sym->isUndefined()) {
312 if (cast<Undefined>(Val: sym)->discardedSecIdx)
313 report(": unable to order discarded symbol: ");
314 else
315 report(": unable to order undefined symbol: ");
316 } else if (sym->isShared())
317 report(": unable to order shared symbol: ");
318 else if (d && !d->section)
319 report(": unable to order absolute symbol: ");
320 else if (d && isa<OutputSection>(Val: d->section))
321 report(": unable to order synthetic symbol: ");
322 else if (d && !d->section->isLive())
323 report(": unable to order discarded symbol: ");
324}
325
326// Returns true if a symbol can be replaced at load-time by a symbol
327// with the same name defined in other ELF executable or DSO.
328bool elf::computeIsPreemptible(Ctx &ctx, const Symbol &sym) {
329 assert(!sym.isLocal() || sym.isPlaceholder());
330
331 // Only symbols with default visibility that appear in dynsym can be
332 // preempted. Symbols with protected visibility cannot be preempted.
333 if (sym.visibility() != STV_DEFAULT)
334 return false;
335
336 // At this point copy relocations have not been created yet.
337 // Shared symbols are preemptible. Undefined symbols are preemptible
338 // when zDynamicUndefined (default in dynamic linking). Weakness is not
339 // checked, though undefined non-weak would typically trigger relocation
340 // errors unless options like -z undefs are used.
341 if (!sym.isDefined())
342 return !sym.isUndefined() || ctx.arg.zDynamicUndefined;
343
344 if (!ctx.arg.shared)
345 return false;
346
347 // If -Bsymbolic or --dynamic-list is specified, or -Bsymbolic-functions is
348 // specified and the symbol is STT_FUNC, the symbol is preemptible iff it is
349 // in the dynamic list. -Bsymbolic-non-weak-functions is a non-weak subset of
350 // -Bsymbolic-functions.
351 if (ctx.arg.symbolic ||
352 (ctx.arg.bsymbolic == BsymbolicKind::NonWeak &&
353 sym.binding != STB_WEAK) ||
354 (ctx.arg.bsymbolic == BsymbolicKind::Functions && sym.isFunc()) ||
355 (ctx.arg.bsymbolic == BsymbolicKind::NonWeakFunctions && sym.isFunc() &&
356 sym.binding != STB_WEAK))
357 return sym.inDynamicList;
358 return true;
359}
360
361void elf::parseVersionAndComputeIsPreemptible(Ctx &ctx) {
362 // Symbol themselves might know their versions because symbols
363 // can contain versions in the form of <name>@<version>.
364 // Let them parse and update their names to exclude version suffix.
365 // In addition, compute isExported and isPreemptible.
366 for (Symbol *sym : ctx.symtab->getSymbols()) {
367 if (sym->hasVersionSuffix)
368 sym->parseSymbolVersion(ctx);
369 if (sym->computeBinding(ctx) == STB_LOCAL) {
370 sym->isExported = false;
371 continue;
372 }
373 if (!sym->isDefined() && !sym->isCommon()) {
374 sym->isPreemptible = computeIsPreemptible(ctx, sym: *sym);
375 } else if (ctx.arg.exportDynamic &&
376 (sym->isUsedInRegularObj || !sym->ltoCanOmit)) {
377 sym->isExported = true;
378 sym->isPreemptible = computeIsPreemptible(ctx, sym: *sym);
379 }
380 }
381}
382
383// Merge symbol properties.
384//
385// When we have many symbols of the same name, we choose one of them,
386// and that's the result of symbol resolution. However, symbols that
387// were not chosen still affect some symbol properties.
388void Symbol::mergeProperties(const Symbol &other) {
389 // DSO symbols do not affect visibility in the output.
390 if (!other.isShared() && other.visibility() != STV_DEFAULT) {
391 uint8_t v = visibility(), ov = other.visibility();
392 setVisibility(v == STV_DEFAULT ? ov : std::min(a: v, b: ov));
393 }
394}
395
396void Symbol::resolve(Ctx &ctx, const Undefined &other) {
397 if (other.visibility() != STV_DEFAULT) {
398 uint8_t v = visibility(), ov = other.visibility();
399 setVisibility(v == STV_DEFAULT ? ov : std::min(a: v, b: ov));
400 }
401 // An undefined symbol with non default visibility must be satisfied
402 // in the same DSO.
403 //
404 // If this is a non-weak defined symbol in a discarded section, override the
405 // existing undefined symbol for better error message later.
406 if (isPlaceholder() || (isShared() && other.visibility() != STV_DEFAULT) ||
407 (isUndefined() && other.binding != STB_WEAK && other.discardedSecIdx)) {
408 other.overwrite(sym&: *this);
409 return;
410 }
411
412 if (traced)
413 printTraceSymbol(sym: other, name: getName());
414
415 if (isLazy()) {
416 // An undefined weak will not extract archive members. See comment on Lazy
417 // in Symbols.h for the details.
418 if (other.binding == STB_WEAK) {
419 binding = STB_WEAK;
420 type = other.type;
421 return;
422 }
423
424 // Do extra check for --warn-backrefs.
425 //
426 // --warn-backrefs is an option to prevent an undefined reference from
427 // extracting an archive member written earlier in the command line. It can
428 // be used to keep compatibility with GNU linkers to some degree. I'll
429 // explain the feature and why you may find it useful in this comment.
430 //
431 // lld's symbol resolution semantics is more relaxed than traditional Unix
432 // linkers. For example,
433 //
434 // ld.lld foo.a bar.o
435 //
436 // succeeds even if bar.o contains an undefined symbol that has to be
437 // resolved by some object file in foo.a. Traditional Unix linkers don't
438 // allow this kind of backward reference, as they visit each file only once
439 // from left to right in the command line while resolving all undefined
440 // symbols at the moment of visiting.
441 //
442 // In the above case, since there's no undefined symbol when a linker visits
443 // foo.a, no files are pulled out from foo.a, and because the linker forgets
444 // about foo.a after visiting, it can't resolve undefined symbols in bar.o
445 // that could have been resolved otherwise.
446 //
447 // That lld accepts more relaxed form means that (besides it'd make more
448 // sense) you can accidentally write a command line or a build file that
449 // works only with lld, even if you have a plan to distribute it to wider
450 // users who may be using GNU linkers. With --warn-backrefs, you can detect
451 // a library order that doesn't work with other Unix linkers.
452 //
453 // The option is also useful to detect cyclic dependencies between static
454 // archives. Again, lld accepts
455 //
456 // ld.lld foo.a bar.a
457 //
458 // even if foo.a and bar.a depend on each other. With --warn-backrefs, it is
459 // handled as an error.
460 //
461 // Here is how the option works. We assign a group ID to each file. A file
462 // with a smaller group ID can pull out object files from an archive file
463 // with an equal or greater group ID. Otherwise, it is a reverse dependency
464 // and an error.
465 //
466 // A file outside --{start,end}-group gets a fresh ID when instantiated. All
467 // files within the same --{start,end}-group get the same group ID. E.g.
468 //
469 // ld.lld A B --start-group C D --end-group E
470 //
471 // A forms group 0. B form group 1. C and D (including their member object
472 // files) form group 2. E forms group 3. I think that you can see how this
473 // group assignment rule simulates the traditional linker's semantics.
474 bool backref = ctx.arg.warnBackrefs && file->groupId < other.file->groupId;
475 extract(ctx);
476
477 if (!ctx.arg.whyExtract.empty())
478 recordWhyExtract(ctx, reference: other.file, extracted: *file, sym: *this);
479
480 // We don't report backward references to weak symbols as they can be
481 // overridden later.
482 //
483 // A traditional linker does not error for -ldef1 -lref -ldef2 (linking
484 // sandwich), where def2 may or may not be the same as def1. We don't want
485 // to warn for this case, so dismiss the warning if we see a subsequent lazy
486 // definition. this->file needs to be saved because in the case of LTO it
487 // may be reset to internalFile or be replaced with a file named lto.tmp.
488 if (backref && !isWeak())
489 ctx.backwardReferences.try_emplace(Key: this,
490 Args: std::make_pair(x: other.file, y&: file));
491 return;
492 }
493
494 // Undefined symbols in a SharedFile do not change the binding.
495 if (isa<SharedFile>(Val: other.file))
496 return;
497
498 if (isUndefined() || isShared()) {
499 // The binding will be weak if there is at least one reference and all are
500 // weak. The binding has one opportunity to change to weak: if the first
501 // reference is weak.
502 if (other.binding != STB_WEAK || !referenced)
503 binding = other.binding;
504 }
505}
506
507// Compare two symbols. Return true if the new symbol should win.
508bool Symbol::shouldReplace(Ctx &ctx, const Defined &other) const {
509 if (LLVM_UNLIKELY(isCommon())) {
510 if (ctx.arg.warnCommon)
511 Warn(ctx) << "common " << getName() << " is overridden";
512 return !other.isWeak();
513 }
514 if (!isDefined())
515 return true;
516
517 // Incoming STB_GLOBAL overrides STB_WEAK/STB_GNU_UNIQUE. -fgnu-unique changes
518 // some vague linkage data in COMDAT from STB_WEAK to STB_GNU_UNIQUE. Treat
519 // STB_GNU_UNIQUE like STB_WEAK so that we prefer the first among all
520 // STB_WEAK/STB_GNU_UNIQUE copies. If we prefer an incoming STB_GNU_UNIQUE to
521 // an existing STB_WEAK, there may be discarded section errors because the
522 // selected copy may be in a non-prevailing COMDAT.
523 return !isGlobal() && other.isGlobal();
524}
525
526void elf::reportDuplicate(Ctx &ctx, const Symbol &sym, const InputFile *newFile,
527 InputSectionBase *errSec, uint64_t errOffset) {
528 if (ctx.arg.allowMultipleDefinition)
529 return;
530 // In glibc<2.32, crti.o has .gnu.linkonce.t.__x86.get_pc_thunk.bx, which
531 // is sort of proto-comdat. There is actually no duplicate if we have
532 // full support for .gnu.linkonce.
533 const Defined *d = dyn_cast<Defined>(Val: &sym);
534 if (!d || d->getName() == "__x86.get_pc_thunk.bx")
535 return;
536 // Allow absolute symbols with the same value for GNU ld compatibility.
537 if (!d->section && !errSec && errOffset && d->value == errOffset)
538 return;
539 if (!d->section || !errSec) {
540 Err(ctx) << "duplicate symbol: " << &sym << "\n>>> defined in " << sym.file
541 << "\n>>> defined in " << newFile;
542 return;
543 }
544
545 // Construct and print an error message in the form of:
546 //
547 // ld.lld: error: duplicate symbol: foo
548 // >>> defined at bar.c:30
549 // >>> bar.o (/home/alice/src/bar.o)
550 // >>> defined at baz.c:563
551 // >>> baz.o in archive libbaz.a
552 auto *sec1 = cast<InputSectionBase>(Val: d->section);
553 auto diag = Err(ctx);
554 diag << "duplicate symbol: " << &sym << "\n>>> defined at ";
555 auto tell = diag.tell();
556 diag << sec1->getSrcMsg(sym, offset: d->value);
557 if (tell != diag.tell())
558 diag << "\n>>> ";
559 diag << sec1->getObjMsg(offset: d->value) << "\n>>> defined at ";
560 tell = diag.tell();
561 diag << errSec->getSrcMsg(sym, offset: errOffset);
562 if (tell != diag.tell())
563 diag << "\n>>> ";
564 diag << errSec->getObjMsg(offset: errOffset);
565}
566
567void Symbol::checkDuplicate(Ctx &ctx, const Defined &other) const {
568 if (isDefined() && !isWeak() && !other.isWeak())
569 reportDuplicate(ctx, sym: *this, newFile: other.file,
570 errSec: dyn_cast_or_null<InputSectionBase>(Val: other.section),
571 errOffset: other.value);
572}
573
574void Symbol::resolve(Ctx &ctx, const CommonSymbol &other) {
575 if (other.visibility() != STV_DEFAULT) {
576 uint8_t v = visibility(), ov = other.visibility();
577 setVisibility(v == STV_DEFAULT ? ov : std::min(a: v, b: ov));
578 }
579 if (isDefined() && !isWeak()) {
580 if (ctx.arg.warnCommon)
581 Warn(ctx) << "common " << getName() << " is overridden";
582 return;
583 }
584
585 if (CommonSymbol *oldSym = dyn_cast<CommonSymbol>(Val: this)) {
586 if (ctx.arg.warnCommon)
587 Warn(ctx) << "multiple common of " << getName();
588 oldSym->alignment = std::max(a: oldSym->alignment, b: other.alignment);
589 if (oldSym->size < other.size) {
590 oldSym->file = other.file;
591 oldSym->size = other.size;
592 }
593 return;
594 }
595
596 if (auto *s = dyn_cast<SharedSymbol>(Val: this)) {
597 // Increase st_size if the shared symbol has a larger st_size. The shared
598 // symbol may be created from common symbols. The fact that some object
599 // files were linked into a shared object first should not change the
600 // regular rule that picks the largest st_size.
601 uint64_t size = s->size;
602 other.overwrite(sym&: *this);
603 if (size > cast<CommonSymbol>(Val: this)->size)
604 cast<CommonSymbol>(Val: this)->size = size;
605 } else {
606 other.overwrite(sym&: *this);
607 }
608}
609
610void Symbol::resolve(Ctx &ctx, const Defined &other) {
611 if (other.visibility() != STV_DEFAULT) {
612 uint8_t v = visibility(), ov = other.visibility();
613 setVisibility(v == STV_DEFAULT ? ov : std::min(a: v, b: ov));
614 }
615 if (shouldReplace(ctx, other))
616 other.overwrite(sym&: *this);
617}
618
619void Symbol::resolve(Ctx &ctx, const LazySymbol &other) {
620 if (isPlaceholder()) {
621 other.overwrite(sym&: *this);
622 return;
623 }
624
625 if (LLVM_UNLIKELY(!isUndefined())) {
626 // See the comment in resolve(Ctx &, const Undefined &).
627 if (isDefined()) {
628 ctx.backwardReferences.erase(Val: this);
629 } else if (isCommon() && ctx.arg.fortranCommon &&
630 other.file->shouldExtractForCommon(name: getName())) {
631 // For common objects, we want to look for global or weak definitions that
632 // should be extracted as the canonical definition instead.
633 ctx.backwardReferences.erase(Val: this);
634 other.overwrite(sym&: *this);
635 other.extract(ctx);
636 }
637 return;
638 }
639
640 // An undefined weak will not extract archive members. See comment on Lazy in
641 // Symbols.h for the details.
642 if (isWeak()) {
643 uint8_t ty = type;
644 other.overwrite(sym&: *this);
645 type = ty;
646 binding = STB_WEAK;
647 return;
648 }
649
650 const InputFile *oldFile = file;
651 other.extract(ctx);
652 if (!ctx.arg.whyExtract.empty())
653 recordWhyExtract(ctx, reference: oldFile, extracted: *file, sym: *this);
654}
655
656void Symbol::resolve(Ctx &ctx, const SharedSymbol &other) {
657 isExported = true;
658 if (isPlaceholder()) {
659 other.overwrite(sym&: *this);
660 return;
661 }
662 if (isCommon()) {
663 // See the comment in resolveCommon() above.
664 if (other.size > cast<CommonSymbol>(Val: this)->size)
665 cast<CommonSymbol>(Val: this)->size = other.size;
666 return;
667 }
668 if (visibility() == STV_DEFAULT && (isUndefined() || isLazy())) {
669 // An undefined symbol with non default visibility must be satisfied
670 // in the same DSO.
671 uint8_t bind = binding;
672 other.overwrite(sym&: *this);
673 binding = bind;
674 } else if (traced)
675 printTraceSymbol(sym: other, name: getName());
676}
677
678void Defined::overwrite(Symbol &sym) const {
679 if (isa_and_nonnull<SharedFile>(Val: sym.file))
680 sym.versionId = VER_NDX_GLOBAL;
681 Symbol::overwrite(sym, k: DefinedKind);
682 auto &s = static_cast<Defined &>(sym);
683 s.value = value;
684 s.size = size;
685 s.section = section;
686}
687