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

src/IceELFSection.h

 //===- subzero/src/IceELFSection.h - Model of ELF sections ------*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // Representation of ELF sections.
@@ skipping 199 matching lines @@
     RelatedSection = Section;
   }
 
   // Track additional relocations which start out relative to offset 0,
   // but should be adjusted to be relative to BaseOff.
   void addRelocations(RelocOffsetT BaseOff, const FixupRefList &FixupRefs);
 
   // Track a single additional relocation.
   void addRelocation(const AssemblerFixup &Fixup) { Fixups.push_back(Fixup); }
 
-  size_t getSectionDataSize(const GlobalContext &Ctx,
-                            const ELFSymbolTableSection *SymTab) const;
+  size_t getSectionDataSize() const;
 
   template <bool IsELF64>
   void writeData(const GlobalContext &Ctx, ELFStreamer &Str,
                  const ELFSymbolTableSection *SymTab);
 
   bool isRela() const { return Header.sh_type == SHT_RELA; }
 
 private:
   const ELFSection *RelatedSection;
   FixupList Fixups;
@@ skipping 94 matching lines @@
       Str.writeLE16(SymInfo.st_shndx);
     }
   }
 }
 
 template <bool IsELF64>
 void ELFRelocationSection::writeData(const GlobalContext &Ctx, ELFStreamer &Str,
                                      const ELFSymbolTableSection *SymTab) {
   for (const AssemblerFixup &Fixup : Fixups) {
     const ELFSym *Symbol = SymTab->findSymbol(Fixup.symbol(&Ctx));
-    // TODO(jvoung): Make sure this always succeeds.
-    // We currently don't track data symbols, so they aren't even marked
-    // as undefined symbols.
-    if (Symbol) {
-      if (IsELF64) {
-        Elf64_Rela Rela;
-        Rela.r_offset = Fixup.position();
-        Rela.setSymbolAndType(Symbol->getNumber(), Fixup.kind());
-        Rela.r_addend = Fixup.offset();
-        Str.writeAddrOrOffset<IsELF64>(Rela.r_offset);
-        Str.writeELFXword<IsELF64>(Rela.r_info);
-        Str.writeELFXword<IsELF64>(Rela.r_addend);
-      } else {
-        Elf32_Rel Rel;
-        Rel.r_offset = Fixup.position();
-        Rel.setSymbolAndType(Symbol->getNumber(), Fixup.kind());
-        Str.writeAddrOrOffset<IsELF64>(Rel.r_offset);
-        Str.writeELFWord<IsELF64>(Rel.r_info);
-      }
+    if (!Symbol)
+      llvm::report_fatal_error("Missing symbol mentioned in reloc");
+
+    if (IsELF64) {
+      Elf64_Rela Rela;
+      Rela.r_offset = Fixup.position();
+      Rela.setSymbolAndType(Symbol->getNumber(), Fixup.kind());
+      Rela.r_addend = Fixup.offset();
+      Str.writeAddrOrOffset<IsELF64>(Rela.r_offset);
+      Str.writeELFXword<IsELF64>(Rela.r_info);
+      Str.writeELFXword<IsELF64>(Rela.r_addend);
+    } else {
+      Elf32_Rel Rel;
+      Rel.r_offset = Fixup.position();
+      Rel.setSymbolAndType(Symbol->getNumber(), Fixup.kind());
+      Str.writeAddrOrOffset<IsELF64>(Rel.r_offset);
+      Str.writeELFWord<IsELF64>(Rel.r_info);
     }
   }
 }
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEELFSECTION_H