ELFWriter.cpp

    // Record the symbol table index for each symbol
    if (Sym.isGlobalValue())
      GblSymLookup[Sym.getGlobalValue()] = i;
    else if (Sym.isExternalSym())
      ExtSymLookup[Sym.getExternalSymbol()] = i;

    // Keep track on the symbol index into the symbol table
    Sym.SymTabIdx = i;
  }

  // One greater than the symbol table index of the last local symbol
  SymTab.Info = FirstNonLocalSymbol;
  SymTab.Size = SymTab.size();
}

/// EmitSectionTableStringTable - This method adds and emits a section for the
/// ELF Section Table string table: the string table that holds all of the
/// section names.
void ELFWriter::EmitSectionTableStringTable() {
  // First step: add the section for the string table to the list of sections:
  ELFSection &SHStrTab = getSectionHeaderStringTableSection();

  // Now that we know which section number is the .shstrtab section, update the
  // e_shstrndx entry in the ELF header.
  ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);

  // Set the NameIdx of each section in the string table and emit the bytes for
  // the string table.
  unsigned Index = 0;

  for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
    ELFSection &S = *(*I);
    // Set the index into the table.  Note if we have lots of entries with
    // common suffixes, we could memoize them here if we cared.
    S.NameIdx = Index;
    SHStrTab.emitString(S.getName());

    // Keep track of the number of bytes emitted to this section.
    Index += S.getName().size()+1;
  }

  // Set the size of .shstrtab now that we know what it is.
  assert(Index == SHStrTab.size());
  SHStrTab.Size = Index;
}

/// OutputSectionsAndSectionTable - Now that we have constructed the file header
/// and all of the sections, emit these to the ostream destination and emit the
/// SectionTable.
void ELFWriter::OutputSectionsAndSectionTable() {
  // Pass #1: Compute the file offset for each section.
  size_t FileOff = ElfHdr.size();   // File header first.

  // Adjust alignment of all section if needed, skip the null section.
  for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
    ELFSection &ES = *SectionList[i];
    if (!ES.size()) {
      ES.Offset = FileOff;
      continue;
    }

    // Update Section size
    if (!ES.Size)
      ES.Size = ES.size();

    // Align FileOff to whatever the alignment restrictions of the section are.
    if (ES.Align)
      FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);

    ES.Offset = FileOff;
    FileOff += ES.Size;
  }

  // Align Section Header.
  unsigned TableAlign = TEW->getPrefELFAlignment();
  FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);

  // Now that we know where all of the sections will be emitted, set the e_shnum
  // entry in the ELF header.
  ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);

  // Now that we know the offset in the file of the section table, update the
  // e_shoff address in the ELF header.
  ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);

  // Now that we know all of the data in the file header, emit it and all of the
  // sections!
  O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
  FileOff = ElfHdr.size();

  // Section Header Table blob
  BinaryObject SHdrTable(isLittleEndian, is64Bit);

  // Emit all of sections to the file and build the section header table.
  for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
    ELFSection &S = *(*I);
    DOUT << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
         << ", Size: " << S.Size << ", Offset: " << S.Offset
         << ", SectionData Size: " << S.size() << "\n";

    // Align FileOff to whatever the alignment restrictions of the section are.
    if (S.size()) {
      if (S.Align)  {
        for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
             FileOff != NewFileOff; ++FileOff)
          O << (char)0xAB;
      }
      O.write((char *)&S.getData()[0], S.Size);
      FileOff += S.Size;
    }

    EmitSectionHeader(SHdrTable, S);
  }

  // Align output for the section table.
  for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
       FileOff != NewFileOff; ++FileOff)
    O << (char)0xAB;

  // Emit the section table itself.
  O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());
}