Track undefined sym in the symtab. Remove hack for missing relocs against undef.

src/IceELFObjectWriter.cpp

Index: src/IceELFObjectWriter.cpp
diff --git a/src/IceELFObjectWriter.cpp b/src/IceELFObjectWriter.cpp
index d15c735edf96c83028bb06c04f0f50c56cdb1cd8..980030be10f0ba859e1223a4f7696101b85e13de 100644
--- a/src/IceELFObjectWriter.cpp
+++ b/src/IceELFObjectWriter.cpp
@@ -533,12 +533,22 @@ void ELFObjectWriter::writeAllRelocationSections(bool IsELF64) {
   writeRelocationSections(IsELF64, RelRODataSections);
 }
 
+void ELFObjectWriter::setUndefinedSyms(const ConstantList &UndefSyms) {
+  for (const Constant *S : UndefSyms) {
+    const auto Sym = llvm::cast<ConstantRelocatable>(S);
+    IceString Name = Sym->getName();

[Jim Stichnoth, 2015/02/01 03:23:55]

The fact that this is IceString instead of IceString& makes me think it's too
bad all the getName() methods don't return references.  Most of the getName()
calls are only used for dumping or textual emission, but this use is probably
unavoidable.

Nothing to do about it yet, I guess.

[jvoung (off chromium), 2015/02/01 17:07:56]

Hmm I can check if they can be converted to return IceString& in a separate CL.

+    assert(Sym->getOffset() == 0 && Sym->getSuppressMangling());

[Jim Stichnoth, 2015/02/01 03:23:55]

I realize there are "violations" elsewhere, but I think it's better to use two
asserts here since you get more precise information on a failure.

[jvoung (off chromium), 2015/02/01 17:07:56]

Oops done.

+    SymTab->noteUndefinedSym(Name, NullSection);
+    StrTab->add(Name);
+  }
+}
+
 void ELFObjectWriter::writeRelocationSections(bool IsELF64,
                                               RelSectionList &RelSections) {
   for (ELFRelocationSection *RelSec : RelSections) {
     Elf64_Off Offset = alignFileOffset(RelSec->getSectionAlign());
     RelSec->setFileOffset(Offset);
-    RelSec->setSize(RelSec->getSectionDataSize(Ctx, SymTab));
+    RelSec->setSize(RelSec->getSectionDataSize());
     if (IsELF64) {
       RelSec->writeData<true>(Ctx, Str, SymTab);
     } else {