Return ErrorOr from SymbolRef::getName.

This function can really fail since the string table offset can be out of
bounds.

Using ErrorOr makes sure the error is checked.

Hopefully a lot of the boilerplate code in tools/* can go away once we have
a diagnostic manager in Object.

llvm-svn: 241297
diff --git a/llvm/lib/Object/MachOObjectFile.cpp b/llvm/lib/Object/MachOObjectFile.cpp
index 51d9677..4255ed7 100644
--- a/llvm/lib/Object/MachOObjectFile.cpp
+++ b/llvm/lib/Object/MachOObjectFile.cpp
@@ -327,16 +327,14 @@
   Symb.p += SymbolTableEntrySize;
 }
 
-std::error_code MachOObjectFile::getSymbolName(DataRefImpl Symb,
-                                               StringRef &Res) const {
+ErrorOr<StringRef> MachOObjectFile::getSymbolName(DataRefImpl Symb) const {
   StringRef StringTable = getStringTableData();
   MachO::nlist_base Entry = getSymbolTableEntryBase(this, Symb);
   const char *Start = &StringTable.data()[Entry.n_strx];
   if (Start < getData().begin() || Start >= getData().end())
     report_fatal_error(
         "Symbol name entry points before beginning or past end of file.");
-  Res = StringRef(Start);
-  return std::error_code();
+  return StringRef(Start);
 }
 
 unsigned MachOObjectFile::getSectionType(SectionRef Sec) const {