[ELF] - Fixed integral constant overflow warning under MSVS 2015.

[grimar]

Summary

Under MSVS 2015 I observed integral constant overflow warning when aggregate initialization was used
to init the bit field. Patch fixes that.

SymbolTable.cpp(177): warning C4307: '-': integral constant overflow
SymbolTable.cpp(176): note: while compiling class template member function 'std::pair<lld::elf::Symbol *,bool> lld::elf::SymbolTable<llvm::object::ELF32LE>::insert(llvm::StringRef)'
SymbolTable.cpp(468): note: see reference to function template instantiation 'std::pair<lld::elf::Symbol *,bool> lld::elf::SymbolTable<llvm::object::ELF32LE>::insert(llvm::StringRef)' being compiled
SymbolTable.cpp(710): note: see reference to class template instantiation 'lld::elf::SymbolTable<llvm::object::ELF32LE>' being compiled
SymbolTable.cpp(183): warning C4307: '-': integral constant overflow

[grimar]

Revision: 276118

ELF/SymbolTable.h

std::pair<Symbol *, bool> insert(StringRef Name, uint8_t Type,
                                    bool IsUsedInRegularObj, InputFile *File);
 
   std::string conflictMsg(SymbolBody *Existing, InputFile *NewFile);
   void reportDuplicate(SymbolBody *Existing, InputFile *NewFile);
 
   std::map<std::string, SymbolBody *> getDemangledSyms();
 
   struct SymIndex {
+    SymIndex(int Idx, unsigned Traced) : Idx(Idx), Traced(Traced) {}
     int Idx : 31;
     unsigned Traced : 1;
   };
 
   // The order the global symbols are in is not defined. We can use an arbitrary
   // order, but it has to be reproducible. That is true even when cross linking.
   // The default hashing of StringRef produces different results on 32 and 64
   // bit systems so we use a map to a vector. That is arbitrary, deterministic

ELF/SymbolTable.cpp

static uint8_t getMinVisibility(uint8_t VA, uint8_t VB) {
   if (VB == STV_DEFAULT)
     return VA;
   return std::min(VA, VB);
 }
 
 // Find an existing symbol or create and insert a new one.
 template <class ELFT>
 std::pair<Symbol *, bool> SymbolTable<ELFT>::insert(StringRef Name) {
-  auto P = Symtab.insert({Name, {(int)SymVector.size(), false}});
+  auto P = Symtab.insert({Name, SymIndex((int)SymVector.size(), false)});
   SymIndex &V = P.first->second;
   bool IsNew = P.second;
 
   if (V.Idx == -1) {
     IsNew = true;
-    V = {(int)SymVector.size(), true};
+    V = SymIndex((int)SymVector.size(), true);
   }
 
   Symbol *Sym;
   if (IsNew) {
     Sym = new (Alloc) Symbol;
     Sym->Binding = STB_WEAK;
     Sym->Visibility = STV_DEFAULT;
     Sym->IsUsedInRegularObj = false;