[lld/mac] Use C++17 structured bindings

[thakis]

Summary

No behavior change.

[int3]

Sweet, didn't know about this feature

lld/MachO/MapFile.cpp

for (OutputSection *osec : seg->getSections()) {
       if (osec->isHidden())
         continue;
 
       os << format("0x%08llX\t0x%08llX\t%s\t%s\n", osec->addr, osec->getSize(),
                    seg->name.str().c_str(), osec->name.str().c_str());
     }
 
   // Dump table of symbols
-  Symbols liveSymbols, deadSymbols;
-  std::tie(liveSymbols, deadSymbols) = getSymbols();
+  auto [liveSymbols, deadSymbols] = getSymbols();
 
   DenseMap<Symbol *, std::string> liveSymbolStrings =
       getSymbolStrings(liveSymbols);
   os << "# Symbols:\n";
   os << "# Address\t    File  Name\n";
   for (Symbol *sym : liveSymbols) {
     assert(sym->isLive());
     os << format("0x%08llX\t[%3u] %s\n", sym->getVA(),

lld/MachO/SymbolTable.cpp

 }
 
 Defined *SymbolTable::addDefined(StringRef name, InputFile *file,
                                  InputSection *isec, uint64_t value,
                                  uint64_t size, bool isWeakDef,
                                  bool isPrivateExtern, bool isThumb,
                                  bool isReferencedDynamically, bool noDeadStrip,
                                  bool isWeakDefCanBeHidden) {
-  Symbol *s;
-  bool wasInserted;
   bool overridesWeakDef = false;
-  std::tie(s, wasInserted) = insert(name, file);
+  auto [s, wasInserted] = insert(name, file);
 
   assert(!isWeakDef || (isa<BitcodeFile>(file) && !isec) ||
          (isa<ObjFile>(file) && file == isec->getFile()));
 
   if (!wasInserted) {
     if (auto *defined = dyn_cast<Defined>(s)) {
       if (isWeakDef) {
         // See further comment in createDefined() in InputFiles.cpp
Defined *SymbolTable::aliasDefined(Defined *src, StringRef target) {
   return addDefined(target, src->getFile(), src->isec, src->value, src->size,
                     src->isWeakDef(), src->privateExtern, src->thumb,
                     src->referencedDynamically, src->noDeadStrip,
                     src->weakDefCanBeHidden);
 }
 
 Symbol *SymbolTable::addUndefined(StringRef name, InputFile *file,
                                   bool isWeakRef) {
-  Symbol *s;
-  bool wasInserted;
-  std::tie(s, wasInserted) = insert(name, file);
+  auto [s, wasInserted] = insert(name, file);
 
   RefState refState = isWeakRef ? RefState::Weak : RefState::Strong;
 
   if (wasInserted)
     replaceSymbol<Undefined>(s, name, file, refState);
   else if (auto *lazy = dyn_cast<LazyArchive>(s))
     lazy->fetchArchiveMember();
   else if (isa<LazyObject>(s))
     extract(*s->getFile(), s->getName());
   else if (auto *dynsym = dyn_cast<DylibSymbol>(s))
     dynsym->reference(refState);
   else if (auto *undefined = dyn_cast<Undefined>(s))
     undefined->refState = std::max(undefined->refState, refState);
   return s;
 }
 
 Symbol *SymbolTable::addCommon(StringRef name, InputFile *file, uint64_t size,
                                uint32_t align, bool isPrivateExtern) {
-  Symbol *s;
-  bool wasInserted;
-  std::tie(s, wasInserted) = insert(name, file);
+  auto [s, wasInserted] = insert(name, file);
 
   if (!wasInserted) {
     if (auto *common = dyn_cast<CommonSymbol>(s)) {
       if (size < common->size)
         return s;
     } else if (isa<Defined>(s)) {
       return s;
     }
     // Common symbols take priority over all non-Defined symbols, so in case of
     // a name conflict, we fall through to the replaceSymbol() call below.
   }
 
   replaceSymbol<CommonSymbol>(s, name, file, size, align, isPrivateExtern);
   return s;
 }
 
 Symbol *SymbolTable::addDylib(StringRef name, DylibFile *file, bool isWeakDef,
                               bool isTlv) {
-  Symbol *s;
-  bool wasInserted;
-  std::tie(s, wasInserted) = insert(name, file);
+  auto [s, wasInserted] = insert(name, file);
 
   RefState refState = RefState::Unreferenced;
   if (!wasInserted) {
     if (auto *defined = dyn_cast<Defined>(s)) {
       if (isWeakDef && !defined->isWeakDef())
         defined->overridesWeakDef = true;
     } else if (auto *undefined = dyn_cast<Undefined>(s)) {
       refState = undefined->refState;

 }
 
 Symbol *SymbolTable::addDynamicLookup(StringRef name) {
   return addDylib(name, /*file=*/nullptr, /*isWeakDef=*/false, /*isTlv=*/false);
 }
 
 Symbol *SymbolTable::addLazyArchive(StringRef name, ArchiveFile *file,
                                     const object::Archive::Symbol &sym) {
-  Symbol *s;
-  bool wasInserted;
-  std::tie(s, wasInserted) = insert(name, file);
+  auto [s, wasInserted] = insert(name, file);
 
   if (wasInserted) {
     replaceSymbol<LazyArchive>(s, file, sym);
   } else if (isa<Undefined>(s)) {
     file->fetch(sym);
   } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
     if (dysym->isWeakDef()) {
       if (dysym->getRefState() != RefState::Unreferenced)
         file->fetch(sym);
       else
         replaceSymbol<LazyArchive>(s, file, sym);
     }
   }
   return s;
 }
 
 Symbol *SymbolTable::addLazyObject(StringRef name, InputFile &file) {
-  Symbol *s;
-  bool wasInserted;
-  std::tie(s, wasInserted) = insert(name, &file);
+  auto [s, wasInserted] = insert(name, &file);
 
   if (wasInserted) {
     replaceSymbol<LazyObject>(s, file, name);
   } else if (isa<Undefined>(s)) {
     extract(file, name);
   } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
     if (dysym->isWeakDef()) {
       if (dysym->getRefState() != RefState::Unreferenced)