forked from OSchip/llvm-project
449 lines
15 KiB
C++
449 lines
15 KiB
C++
//===- SymbolTable.cpp ----------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "SymbolTable.h"
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#include "ConcatOutputSection.h"
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#include "Config.h"
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#include "InputFiles.h"
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#include "InputSection.h"
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#include "Symbols.h"
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#include "SyntheticSections.h"
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#include "lld/Common/ErrorHandler.h"
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#include "lld/Common/Memory.h"
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using namespace llvm;
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using namespace lld;
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using namespace lld::macho;
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Symbol *SymbolTable::find(CachedHashStringRef cachedName) {
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auto it = symMap.find(cachedName);
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if (it == symMap.end())
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return nullptr;
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return symVector[it->second];
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}
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std::pair<Symbol *, bool> SymbolTable::insert(StringRef name,
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const InputFile *file) {
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auto p = symMap.insert({CachedHashStringRef(name), (int)symVector.size()});
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Symbol *sym;
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if (!p.second) {
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// Name already present in the symbol table.
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sym = symVector[p.first->second];
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} else {
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// Name is a new symbol.
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sym = reinterpret_cast<Symbol *>(make<SymbolUnion>());
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symVector.push_back(sym);
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}
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sym->isUsedInRegularObj |= !file || isa<ObjFile>(file);
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return {sym, p.second};
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}
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Defined *SymbolTable::addDefined(StringRef name, InputFile *file,
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InputSection *isec, uint64_t value,
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uint64_t size, bool isWeakDef,
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bool isPrivateExtern, bool isThumb,
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bool isReferencedDynamically, bool noDeadStrip,
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bool isWeakDefCanBeHidden) {
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Symbol *s;
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bool wasInserted;
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bool overridesWeakDef = false;
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std::tie(s, wasInserted) = insert(name, file);
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assert(!isWeakDef || (isa<BitcodeFile>(file) && !isec) ||
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(isa<ObjFile>(file) && file == isec->getFile()));
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if (!wasInserted) {
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if (auto *defined = dyn_cast<Defined>(s)) {
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if (isWeakDef) {
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// See further comment in createDefined() in InputFiles.cpp
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if (defined->isWeakDef()) {
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defined->privateExtern &= isPrivateExtern;
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defined->weakDefCanBeHidden &= isWeakDefCanBeHidden;
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defined->referencedDynamically |= isReferencedDynamically;
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defined->noDeadStrip |= noDeadStrip;
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}
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// FIXME: Handle this for bitcode files.
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if (auto concatIsec = dyn_cast_or_null<ConcatInputSection>(isec))
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concatIsec->wasCoalesced = true;
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return defined;
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}
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if (defined->isWeakDef()) {
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// FIXME: Handle this for bitcode files.
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if (auto concatIsec =
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dyn_cast_or_null<ConcatInputSection>(defined->isec)) {
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concatIsec->wasCoalesced = true;
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concatIsec->symbols.erase(llvm::find(concatIsec->symbols, defined));
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}
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} else {
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std::string src1 = defined->getSourceLocation();
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std::string src2 = isec ? isec->getSourceLocation(value) : "";
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std::string message =
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"duplicate symbol: " + toString(*defined) + "\n>>> defined in ";
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if (!src1.empty())
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message += src1 + "\n>>> ";
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message += toString(defined->getFile()) + "\n>>> defined in ";
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if (!src2.empty())
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message += src2 + "\n>>> ";
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error(message + toString(file));
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}
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} else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
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overridesWeakDef = !isWeakDef && dysym->isWeakDef();
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dysym->unreference();
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}
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// Defined symbols take priority over other types of symbols, so in case
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// of a name conflict, we fall through to the replaceSymbol() call below.
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}
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// With -flat_namespace, all extern symbols in dylibs are interposable.
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// FIXME: Add support for `-interposable` (PR53680).
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bool interposable = config->namespaceKind == NamespaceKind::flat &&
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config->outputType != MachO::MH_EXECUTE &&
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!isPrivateExtern;
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Defined *defined = replaceSymbol<Defined>(
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s, name, file, isec, value, size, isWeakDef, /*isExternal=*/true,
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isPrivateExtern, /*includeInSymtab=*/true, isThumb,
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isReferencedDynamically, noDeadStrip, overridesWeakDef,
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isWeakDefCanBeHidden, interposable);
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return defined;
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}
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Defined *SymbolTable::aliasDefined(Defined *src, StringRef target) {
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return addDefined(target, src->getFile(), src->isec, src->value, src->size,
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src->isWeakDef(), src->privateExtern, src->thumb,
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src->referencedDynamically, src->noDeadStrip,
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src->weakDefCanBeHidden);
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}
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Symbol *SymbolTable::addUndefined(StringRef name, InputFile *file,
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bool isWeakRef) {
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Symbol *s;
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bool wasInserted;
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std::tie(s, wasInserted) = insert(name, file);
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RefState refState = isWeakRef ? RefState::Weak : RefState::Strong;
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if (wasInserted)
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replaceSymbol<Undefined>(s, name, file, refState);
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else if (auto *lazy = dyn_cast<LazyArchive>(s))
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lazy->fetchArchiveMember();
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else if (isa<LazyObject>(s))
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extract(*s->getFile(), s->getName());
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else if (auto *dynsym = dyn_cast<DylibSymbol>(s))
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dynsym->reference(refState);
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else if (auto *undefined = dyn_cast<Undefined>(s))
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undefined->refState = std::max(undefined->refState, refState);
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return s;
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}
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Symbol *SymbolTable::addCommon(StringRef name, InputFile *file, uint64_t size,
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uint32_t align, bool isPrivateExtern) {
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Symbol *s;
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bool wasInserted;
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std::tie(s, wasInserted) = insert(name, file);
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if (!wasInserted) {
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if (auto *common = dyn_cast<CommonSymbol>(s)) {
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if (size < common->size)
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return s;
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} else if (isa<Defined>(s)) {
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return s;
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}
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// Common symbols take priority over all non-Defined symbols, so in case of
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// a name conflict, we fall through to the replaceSymbol() call below.
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}
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replaceSymbol<CommonSymbol>(s, name, file, size, align, isPrivateExtern);
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return s;
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}
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Symbol *SymbolTable::addDylib(StringRef name, DylibFile *file, bool isWeakDef,
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bool isTlv) {
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Symbol *s;
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bool wasInserted;
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std::tie(s, wasInserted) = insert(name, file);
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RefState refState = RefState::Unreferenced;
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if (!wasInserted) {
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if (auto *defined = dyn_cast<Defined>(s)) {
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if (isWeakDef && !defined->isWeakDef())
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defined->overridesWeakDef = true;
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} else if (auto *undefined = dyn_cast<Undefined>(s)) {
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refState = undefined->refState;
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} else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
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refState = dysym->getRefState();
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}
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}
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bool isDynamicLookup = file == nullptr;
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if (wasInserted || isa<Undefined>(s) ||
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(isa<DylibSymbol>(s) &&
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((!isWeakDef && s->isWeakDef()) ||
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(!isDynamicLookup && cast<DylibSymbol>(s)->isDynamicLookup())))) {
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if (auto *dynsym = dyn_cast<DylibSymbol>(s))
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dynsym->unreference();
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replaceSymbol<DylibSymbol>(s, file, name, isWeakDef, refState, isTlv);
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}
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return s;
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}
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Symbol *SymbolTable::addDynamicLookup(StringRef name) {
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return addDylib(name, /*file=*/nullptr, /*isWeakDef=*/false, /*isTlv=*/false);
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}
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Symbol *SymbolTable::addLazyArchive(StringRef name, ArchiveFile *file,
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const object::Archive::Symbol &sym) {
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Symbol *s;
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bool wasInserted;
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std::tie(s, wasInserted) = insert(name, file);
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if (wasInserted) {
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replaceSymbol<LazyArchive>(s, file, sym);
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} else if (isa<Undefined>(s)) {
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file->fetch(sym);
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} else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
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if (dysym->isWeakDef()) {
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if (dysym->getRefState() != RefState::Unreferenced)
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file->fetch(sym);
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else
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replaceSymbol<LazyArchive>(s, file, sym);
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}
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}
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return s;
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}
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Symbol *SymbolTable::addLazyObject(StringRef name, InputFile &file) {
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Symbol *s;
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bool wasInserted;
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std::tie(s, wasInserted) = insert(name, &file);
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if (wasInserted) {
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replaceSymbol<LazyObject>(s, file, name);
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} else if (isa<Undefined>(s)) {
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extract(file, name);
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} else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
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if (dysym->isWeakDef()) {
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if (dysym->getRefState() != RefState::Unreferenced)
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extract(file, name);
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else
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replaceSymbol<LazyObject>(s, file, name);
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}
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}
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return s;
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}
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Defined *SymbolTable::addSynthetic(StringRef name, InputSection *isec,
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uint64_t value, bool isPrivateExtern,
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bool includeInSymtab,
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bool referencedDynamically) {
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assert(!isec || !isec->getFile()); // See makeSyntheticInputSection().
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Defined *s =
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addDefined(name, /*file=*/nullptr, isec, value, /*size=*/0,
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/*isWeakDef=*/false, isPrivateExtern, /*isThumb=*/false,
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referencedDynamically, /*noDeadStrip=*/false,
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/*isWeakDefCanBeHidden=*/false);
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s->includeInSymtab = includeInSymtab;
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return s;
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}
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enum class Boundary {
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Start,
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End,
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};
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static Defined *createBoundarySymbol(const Undefined &sym) {
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return symtab->addSynthetic(
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sym.getName(), /*isec=*/nullptr, /*value=*/-1, /*isPrivateExtern=*/true,
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/*includeInSymtab=*/false, /*referencedDynamically=*/false);
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}
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static void handleSectionBoundarySymbol(const Undefined &sym, StringRef segSect,
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Boundary which) {
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StringRef segName, sectName;
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std::tie(segName, sectName) = segSect.split('$');
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// Attach the symbol to any InputSection that will end up in the right
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// OutputSection -- it doesn't matter which one we pick.
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// Don't bother looking through inputSections for a matching
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// ConcatInputSection -- we need to create ConcatInputSection for
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// non-existing sections anyways, and that codepath works even if we should
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// already have a ConcatInputSection with the right name.
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OutputSection *osec = nullptr;
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// This looks for __TEXT,__cstring etc.
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for (SyntheticSection *ssec : syntheticSections)
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if (ssec->segname == segName && ssec->name == sectName) {
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osec = ssec->isec->parent;
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break;
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}
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if (!osec) {
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ConcatInputSection *isec = makeSyntheticInputSection(segName, sectName);
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// This runs after markLive() and is only called for Undefineds that are
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// live. Marking the isec live ensures an OutputSection is created that the
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// start/end symbol can refer to.
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assert(sym.isLive());
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isec->live = true;
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// This runs after gatherInputSections(), so need to explicitly set parent
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// and add to inputSections.
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osec = isec->parent = ConcatOutputSection::getOrCreateForInput(isec);
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inputSections.push_back(isec);
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}
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if (which == Boundary::Start)
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osec->sectionStartSymbols.push_back(createBoundarySymbol(sym));
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else
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osec->sectionEndSymbols.push_back(createBoundarySymbol(sym));
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}
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static void handleSegmentBoundarySymbol(const Undefined &sym, StringRef segName,
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Boundary which) {
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OutputSegment *seg = getOrCreateOutputSegment(segName);
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if (which == Boundary::Start)
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seg->segmentStartSymbols.push_back(createBoundarySymbol(sym));
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else
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seg->segmentEndSymbols.push_back(createBoundarySymbol(sym));
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}
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// Try to find a definition for an undefined symbol.
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// Returns true if a definition was found and no diagnostics are needed.
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static bool recoverFromUndefinedSymbol(const Undefined &sym) {
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// Handle start/end symbols.
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StringRef name = sym.getName();
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if (name.consume_front("section$start$")) {
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handleSectionBoundarySymbol(sym, name, Boundary::Start);
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return true;
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}
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if (name.consume_front("section$end$")) {
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handleSectionBoundarySymbol(sym, name, Boundary::End);
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return true;
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}
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if (name.consume_front("segment$start$")) {
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handleSegmentBoundarySymbol(sym, name, Boundary::Start);
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return true;
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}
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if (name.consume_front("segment$end$")) {
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handleSegmentBoundarySymbol(sym, name, Boundary::End);
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return true;
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}
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// Leave dtrace symbols, since we will handle them when we do the relocation
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if (name.startswith("___dtrace_"))
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return true;
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// Handle -U.
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if (config->explicitDynamicLookups.count(sym.getName())) {
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symtab->addDynamicLookup(sym.getName());
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return true;
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}
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// Handle -undefined.
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if (config->undefinedSymbolTreatment ==
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UndefinedSymbolTreatment::dynamic_lookup ||
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config->undefinedSymbolTreatment == UndefinedSymbolTreatment::suppress) {
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symtab->addDynamicLookup(sym.getName());
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return true;
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}
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// We do not return true here, as we still need to print diagnostics.
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if (config->undefinedSymbolTreatment == UndefinedSymbolTreatment::warning)
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symtab->addDynamicLookup(sym.getName());
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return false;
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}
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namespace {
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struct UndefinedDiag {
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struct SectionAndOffset {
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const InputSection *isec;
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uint64_t offset;
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};
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std::vector<SectionAndOffset> codeReferences;
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std::vector<std::string> otherReferences;
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};
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MapVector<const Undefined *, UndefinedDiag> undefs;
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}
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void macho::reportPendingUndefinedSymbols() {
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for (const auto &undef : undefs) {
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const UndefinedDiag &locations = undef.second;
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std::string message = "undefined symbol";
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if (config->archMultiple)
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message += (" for arch " + getArchitectureName(config->arch())).str();
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message += ": " + toString(*undef.first);
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const size_t maxUndefinedReferences = 3;
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size_t i = 0;
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for (const std::string &loc : locations.otherReferences) {
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if (i >= maxUndefinedReferences)
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break;
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message += "\n>>> referenced by " + loc;
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++i;
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}
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for (const UndefinedDiag::SectionAndOffset &loc :
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locations.codeReferences) {
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if (i >= maxUndefinedReferences)
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break;
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message += "\n>>> referenced by ";
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std::string src = loc.isec->getSourceLocation(loc.offset);
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if (!src.empty())
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message += src + "\n>>> ";
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message += loc.isec->getLocation(loc.offset);
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++i;
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}
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size_t totalReferences =
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locations.otherReferences.size() + locations.codeReferences.size();
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if (totalReferences > i)
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message +=
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("\n>>> referenced " + Twine(totalReferences - i) + " more times")
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.str();
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if (config->undefinedSymbolTreatment == UndefinedSymbolTreatment::error)
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error(message);
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else if (config->undefinedSymbolTreatment ==
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UndefinedSymbolTreatment::warning)
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warn(message);
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else
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assert(false &&
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"diagnostics make sense for -undefined error|warning only");
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}
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// This function is called multiple times during execution. Clear the printed
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// diagnostics to avoid printing the same things again the next time.
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undefs.clear();
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}
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void macho::treatUndefinedSymbol(const Undefined &sym, StringRef source) {
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if (recoverFromUndefinedSymbol(sym))
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return;
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undefs[&sym].otherReferences.push_back(source.str());
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}
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void macho::treatUndefinedSymbol(const Undefined &sym, const InputSection *isec,
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uint64_t offset) {
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if (recoverFromUndefinedSymbol(sym))
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return;
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undefs[&sym].codeReferences.push_back({isec, offset});
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}
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std::unique_ptr<SymbolTable> macho::symtab;
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