[Object/ELF] - Check index argument in getSymbol().
Without this check LLD crashes when SHT_GROUP section has invalid symbol index
because of next code:
template <class ELFT>
StringRef elf::ObjectFile<ELFT>::getShtGroupSignature(const Elf_Shdr &Sec) {
..
const Elf_Sym *Sym = Obj.getSymbol(Symtab, Sec.sh_info);
..
}
If sh_info is too large, &Symbols[Index] just asserts.
No testcases provided because llvm-objdump/llvm-readelf does
not use getSymbol() function.
I`ll commit testcase for LLD separatelly.
Differential revision: https://reviews.llvm.org/D25516
llvm-svn: 284702