[Object] Change getSectionName() to use Expected<StringRef>

[MaskRay]

Summary

It currently receives an output parameter and returns
std::error_code. Expected<StringRef> fits for this purpose perfectly.

[jhenderson]

Looks good, apart from one comment.

llvm/tools/llvm-readobj/COFFDumper.cpp

1545 ↗

(On Diff #197709)

I'm not sure this is the right way to throw away an Error. Assuming for a moment that we don't want to report this error here (I'm guessing we probably should at some point), you should use something like consumeError.

[MaskRay]

Use consumeError

[MaskRay]

llvm/tools/llvm-readobj/COFFDumper.cpp

1545 ↗

(On Diff #197709)

Thanks! I forgot consumeError.

[jhenderson]

LGTM. It might be worth a TODO/FIXME next to that consumeError saying we should propagate it (assuming that we should).

[MaskRay]

Add a TODO

COFF/Chunks.cpp

 
 namespace lld {
 namespace coff {
 
 SectionChunk::SectionChunk(ObjFile *F, const coff_section *H)
     : Chunk(SectionKind), File(F), Header(H),
       Relocs(File->getCOFFObj()->getRelocations(Header)), Repl(this) {
   // Initialize SectionName.
-  File->getCOFFObj()->getSectionName(Header, SectionName);
+  if (Expected<StringRef> E = File->getCOFFObj()->getSectionName(Header))
+    SectionName = *E;
 
   Alignment = Header->getAlignment();
 
   // If linker GC is disabled, every chunk starts out alive.  If linker GC is
   // enabled, treat non-comdat sections as roots. Generally optimized object
   // files will be built with -ffunction-sections or /Gy, so most things worth
   // stripping will be in a comdat.
   Live = !Config->DoGC || !isCOMDAT();

COFF/InputFiles.cpp

 }
 
 SectionChunk *ObjFile::readSection(uint32_t SectionNumber,
                                    const coff_aux_section_definition *Def,
                                    StringRef LeaderName) {
   const coff_section *Sec = getSection(SectionNumber);
 
   StringRef Name;
-  if (auto EC = COFFObj->getSectionName(Sec, Name))
+  if (Expected<StringRef> E = COFFObj->getSectionName(Sec))
+    Name = *E;
+  else
     fatal("getSectionName failed: #" + Twine(SectionNumber) + ": " +
-          EC.message());
+          toString(E.takeError()));
 
   if (Name == ".drectve") {
     ArrayRef<uint8_t> Data;
     COFFObj->getSectionContents(Sec, Data);
     Directives = StringRef((const char *)Data.data(), Data.size());
     return nullptr;
   }
 
void ObjFile::readAssociativeDefinition(COFFSymbolRef Sym,
   SectionChunk *Parent = SparseChunks[ParentIndex];
   int32_t SectionNumber = Sym.getSectionNumber();
 
   auto Diag = [&]() {
     StringRef Name, ParentName;
     COFFObj->getSymbolName(Sym, Name);
 
     const coff_section *ParentSec = getSection(ParentIndex);
-    COFFObj->getSectionName(ParentSec, ParentName);
+    if (Expected<StringRef> E = COFFObj->getSectionName(ParentSec))
+      ParentName = *E;
     error(toString(this) + ": associative comdat " + Name + " (sec " +
           Twine(SectionNumber) + ") has invalid reference to section " +
           ParentName + " (sec " + Twine(ParentIndex) + ")");
   };
 
   if (Parent == PendingComdat) {
     // This can happen if an associative comdat refers to another associative
     // comdat that appears after it (invalid per COFF spec) or to a section