lib/CodeGen/ELFWriter.cpp - platform/external/llvm - Gitiles

 //===-- ELFWriter.cpp - Target-independent ELF Writer code ----------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file was developed by the LLVM research group and is distributed under
 // the University of Illinois Open Source License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the target-independent ELF writer.  This file writes out
 // the ELF file in the following order:
 //
 //  #1. ELF Header
 //  #2. '.text' section
 //  #3. '.data' section
 //  #4. '.bss' section  (conceptual position in file)
 //  ...
 //  #X. '.shstrtab' section
 //  #Y. Section Table
 //
 // The entries in the section table are laid out as:
 //  #0. Null entry [required]
 //  #1. ".text" entry - the program code
 //  #2. ".data" entry - global variables with initializers.     [ if needed ]
 //  #3. ".bss" entry  - global variables without initializers.  [ if needed ]
 //  ...
 //  #N. ".shstrtab" entry - String table for the section names.

 //
 // NOTE: This code should eventually be extended to support 64-bit ELF (this
 // won't be hard), but we haven't done so yet!
 //
 //===----------------------------------------------------------------------===//

 #include "llvm/CodeGen/ELFWriter.h"
 #include "llvm/Module.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Support/Mangler.h"
 using namespace llvm;

 ELFWriter::ELFWriter(std::ostream &o, TargetMachine &tm) : O(o), TM(tm) {
   e_machine = 0;  // e_machine defaults to 'No Machine'
   e_flags = 0;    // e_flags defaults to 0, no flags.

   is64Bit = TM.getTargetData().getPointerSizeInBits() == 64;
   isLittleEndian = TM.getTargetData().isLittleEndian();
 }

 // doInitialization - Emit the file header and all of the global variables for
 // the module to the ELF file.
 bool ELFWriter::doInitialization(Module &M) {
   Mang = new Mangler(M);

   outbyte(0x7F);                     // EI_MAG0
   outbyte('E');                      // EI_MAG1
   outbyte('L');                      // EI_MAG2
   outbyte('F');                      // EI_MAG3
   outbyte(is64Bit ? 2 : 1);          // EI_CLASS
   outbyte(isLittleEndian ? 1 : 2);   // EI_DATA
   outbyte(1);                        // EI_VERSION
   for (unsigned i = OutputBuffer.size(); i != 16; ++i)
     outbyte(0);                      // EI_PAD up to 16 bytes.

   // This should change for shared objects.
   outhalf(1);                        // e_type = ET_REL
   outhalf(e_machine);                // e_machine = whatever the target wants
   outword(1);                        // e_version = 1
   outaddr(0);                        // e_entry = 0 -> no entry point in .o file
   outaddr(0);                        // e_phoff = 0 -> no program header for .o

   ELFHeader_e_shoff_Offset = OutputBuffer.size();
   outaddr(0);                        // e_shoff
   outword(e_flags);                  // e_flags = whatever the target wants

   assert(!is64Bit && "These sizes need to be adjusted for 64-bit!");
   outhalf(52);                       // e_ehsize = ELF header size
   outhalf(0);                        // e_phentsize = prog header entry size
   outhalf(0);                        // e_phnum     = # prog header entries = 0
   outhalf(40);                       // e_shentsize = sect header entry size


   ELFHeader_e_shnum_Offset = OutputBuffer.size();
   outhalf(0);                        // e_shnum     = # of section header ents
   ELFHeader_e_shstrndx_Offset = OutputBuffer.size();
   outhalf(0);                        // e_shstrndx  = Section # of '.shstrtab'

   // Add the null section.
   SectionList.push_back(ELFSection());

   // Start up the symbol table.  The first entry in the symtab is the null
   // entry.
   SymbolTable.push_back(ELFSym(0));


   // FIXME: Should start the .text section.
   return false;
 }

 void ELFWriter::EmitGlobal(GlobalVariable *GV, ELFSection &DataSection,
                            ELFSection &BSSSection) {
   // If this is an external global, emit it now.  TODO: Note that it would be
   // better to ignore the symbol here and only add it to the symbol table if
   // referenced.
   if (!GV->hasInitializer()) {
     ELFSym ExternalSym(GV);
     ExternalSym.SetBind(ELFSym::STB_GLOBAL);
     ExternalSym.SetType(ELFSym::STT_NOTYPE);
     ExternalSym.SectionIdx = ELFSection::SHN_UNDEF;
     SymbolTable.push_back(ExternalSym);
     return;
   }

   const Type *GVType = (const Type*)GV->getType();
   unsigned Align = TM.getTargetData().getTypeAlignment(GVType);
   unsigned Size  = TM.getTargetData().getTypeSize(GVType);

   // If this global has a zero initializer, it is part of the .bss or common
   // section.
   if (GV->getInitializer()->isNullValue()) {
     // If this global is part of the common block, add it now.  Variables are
     // part of the common block if they are zero initialized and allowed to be
     // merged with other symbols.
     if (GV->hasLinkOnceLinkage() || GV->hasWeakLinkage()) {
       ELFSym CommonSym(GV);
       // Value for common symbols is the alignment required.
       CommonSym.Value = Align;
       CommonSym.Size  = Size;
       CommonSym.SetBind(ELFSym::STB_GLOBAL);
       CommonSym.SetType(ELFSym::STT_OBJECT);
       // TODO SOMEDAY: add ELF visibility.
       CommonSym.SectionIdx = ELFSection::SHN_COMMON;
       SymbolTable.push_back(CommonSym);
       return;
     }

     // Otherwise, this symbol is part of the .bss section.  Emit it now.

     // Handle alignment.  Ensure section is aligned at least as much as required
     // by this symbol.
     BSSSection.Align = std::max(BSSSection.Align, Align);

     // Within the section, emit enough virtual padding to get us to an alignment
     // boundary.
     if (Align)
       BSSSection.Size = (BSSSection.Size + Align - 1) & ~(Align-1);

     ELFSym BSSSym(GV);
     BSSSym.Value = BSSSection.Size;
     BSSSym.Size = Size;
     BSSSym.SetType(ELFSym::STT_OBJECT);

     switch (GV->getLinkage()) {
     default:  // weak/linkonce handled above
       assert(0 && "Unexpected linkage type!");
     case GlobalValue::AppendingLinkage:  // FIXME: This should be improved!
     case GlobalValue::ExternalLinkage:
       BSSSym.SetBind(ELFSym::STB_GLOBAL);
       break;
     case GlobalValue::InternalLinkage:
       BSSSym.SetBind(ELFSym::STB_LOCAL);
       break;
     }

     // Set the idx of the .bss section
     BSSSym.SectionIdx = &BSSSection-&SectionList[0];
     SymbolTable.push_back(BSSSym);

     // Reserve space in the .bss section for this symbol.
     BSSSection.Size += Size;
     return;
   }

   // FIXME: handle .rodata
   //assert(!GV->isConstant() && "unimp");

   // FIXME: handle .data
   //assert(0 && "unimp");
 }


 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
   return false;
 }

 /// doFinalization - Now that the module has been completely processed, emit
 /// the ELF file to 'O'.
 bool ELFWriter::doFinalization(Module &M) {
   // Okay, the .text section has now been finalized.
   // FIXME: finalize the .text section.

   // Okay, the ELF header and .text sections have been completed, build the
   // .data, .bss, and "common" sections next.
   SectionList.push_back(ELFSection(".data", OutputBuffer.size()));
   SectionList.push_back(ELFSection(".bss"));
   ELFSection &DataSection = *(SectionList.end()-2);
   ELFSection &BSSSection = SectionList.back();
   for (Module::global_iterator I = M.global_begin(), E = M.global_end();
        I != E; ++I)
     EmitGlobal(I, DataSection, BSSSection);

   // Finish up the data section.
   DataSection.Type  = ELFSection::SHT_PROGBITS;
   DataSection.Flags = ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC;

   // The BSS Section logically starts at the end of the Data Section (adjusted
   // to the required alignment of the BSSSection).
   BSSSection.Offset = DataSection.Offset+DataSection.Size;
   BSSSection.Type   = ELFSection::SHT_NOBITS;
   BSSSection.Flags  = ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC;
   if (BSSSection.Align)
     BSSSection.Offset = (BSSSection.Offset+BSSSection.Align-1) &
                         ~(BSSSection.Align-1);

   // Emit the symbol table now, if non-empty.
   EmitSymbolTable();

   // FIXME: Emit the relocations now.

   // Emit the string table for the sections in the ELF file we have.
   EmitSectionTableStringTable();

   // Emit the .o file section table.
   EmitSectionTable();

   // Emit the .o file to the specified stream.
   O.write((char*)&OutputBuffer[0], OutputBuffer.size());

   // Free the output buffer.
   std::vector<unsigned char>().swap(OutputBuffer);

   // Release the name mangler object.
   delete Mang; Mang = 0;
   return false;
 }

 /// EmitSymbolTable - If the current symbol table is non-empty, emit the string
 /// table for it and then the symbol table itself.
 void ELFWriter::EmitSymbolTable() {
   if (SymbolTable.size() == 1) return;  // Only the null entry.

   // FIXME: compact all local symbols to the start of the symtab.
   unsigned FirstNonLocalSymbol = 1;

   SectionList.push_back(ELFSection(".strtab", OutputBuffer.size()));
   ELFSection &StrTab = SectionList.back();
   StrTab.Type = ELFSection::SHT_STRTAB;
   StrTab.Align = 1;

   // Set the zero'th symbol to a null byte, as required.
   outbyte(0);
   SymbolTable[0].NameIdx = 0;
   unsigned Index = 1;
   for (unsigned i = 1, e = SymbolTable.size(); i != e; ++i) {
     // Use the name mangler to uniquify the LLVM symbol.
     std::string Name = Mang->getValueName(SymbolTable[i].GV);

     if (Name.empty()) {
       SymbolTable[i].NameIdx = 0;
     } else {
       SymbolTable[i].NameIdx = Index;

       // Add the name to the output buffer, including the null terminator.
       OutputBuffer.insert(OutputBuffer.end(), Name.begin(), Name.end());

       // Add a null terminator.
       OutputBuffer.push_back(0);

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

   StrTab.Size = OutputBuffer.size()-StrTab.Offset;

   // Now that we have emitted the string table and know the offset into the
   // string table of each symbol, emit the symbol table itself.
   assert(!is64Bit && "Should this be 8 byte aligned for 64-bit?"
          " (check .Align below also)");
   align(4);

   SectionList.push_back(ELFSection(".symtab", OutputBuffer.size()));
   ELFSection &SymTab = SectionList.back();
   SymTab.Type = ELFSection::SHT_SYMTAB;
   SymTab.Align = 4;   // FIXME: check for ELF64
   SymTab.Link = SectionList.size()-2;  // Section Index of .strtab.
   SymTab.Info = FirstNonLocalSymbol;   // First non-STB_LOCAL symbol.
   SymTab.EntSize = 16; // Size of each symtab entry. FIXME: wrong for ELF64

   assert(!is64Bit && "check this!");
   for (unsigned i = 0, e = SymbolTable.size(); i != e; ++i) {
     ELFSym &Sym = SymbolTable[i];
     outword(Sym.NameIdx);
     outaddr(Sym.Value);
     outword(Sym.Size);
     outbyte(Sym.Info);
     outbyte(Sym.Other);
     outhalf(Sym.SectionIdx);
   }

   SymTab.Size = OutputBuffer.size()-SymTab.Offset;
 }

 /// 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:
   SectionList.push_back(ELFSection(".shstrtab", OutputBuffer.size()));
   SectionList.back().Type = ELFSection::SHT_STRTAB;

   // Now that we know which section number is the .shstrtab section, update the
   // e_shstrndx entry in the ELF header.
   fixhalf(SectionList.size()-1, ELFHeader_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 (unsigned i = 0, e = SectionList.size(); i != e; ++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.
     SectionList[i].NameIdx = Index;

     // Add the name to the output buffer, including the null terminator.
     OutputBuffer.insert(OutputBuffer.end(), SectionList[i].Name.begin(),
                         SectionList[i].Name.end());
     // Add a null terminator.
     OutputBuffer.push_back(0);

     // Keep track of the number of bytes emitted to this section.
     Index += SectionList[i].Name.size()+1;
   }

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

 /// EmitSectionTable - Now that we have emitted the entire contents of the file
 /// (all of the sections), emit the section table which informs the reader where
 /// the boundaries are.
 void ELFWriter::EmitSectionTable() {
   // Now that all of the sections have been emitted, set the e_shnum entry in
   // the ELF header.
   fixhalf(SectionList.size(), ELFHeader_e_shnum_Offset);

   // Now that we know the offset in the file of the section table (which we emit
   // next), update the e_shoff address in the ELF header.
   fixaddr(OutputBuffer.size(), ELFHeader_e_shoff_Offset);

   // Emit all of the section table entries.
   for (unsigned i = 0, e = SectionList.size(); i != e; ++i) {
     const ELFSection &S = SectionList[i];
     outword(S.NameIdx);  // sh_name - Symbol table name idx
     outword(S.Type);     // sh_type - Section contents & semantics
     outword(S.Flags);    // sh_flags - Section flags.
     outaddr(S.Addr);     // sh_addr - The mem address this section appears in.
     outaddr(S.Offset);   // sh_offset - The offset from the start of the file.
     outword(S.Size);     // sh_size - The section size.
     outword(S.Link);     // sh_link - Section header table index link.
     outword(S.Info);     // sh_info - Auxillary information.
     outword(S.Align);    // sh_addralign - Alignment of section.
     outword(S.EntSize);  // sh_entsize - Size of each entry in the section.
   }

   // Release the memory allocated for the section list.
   std::vector<ELFSection>().swap(SectionList);
 }
	//===-- ELFWriter.cpp - Target-independent ELF Writer code ----------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file was developed by the LLVM research group and is distributed under
	// the University of Illinois Open Source License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// This file implements the target-independent ELF writer. This file writes out
	// the ELF file in the following order:
	//
	// #1. ELF Header
	// #2. '.text' section
	// #3. '.data' section
	// #4. '.bss' section (conceptual position in file)
	// ...
	// #X. '.shstrtab' section
	// #Y. Section Table
	//
	// The entries in the section table are laid out as:
	// #0. Null entry [required]
	// #1. ".text" entry - the program code
	// #2. ".data" entry - global variables with initializers. [ if needed ]
	// #3. ".bss" entry - global variables without initializers. [ if needed ]
	// ...
	// #N. ".shstrtab" entry - String table for the section names.

	//
	// NOTE: This code should eventually be extended to support 64-bit ELF (this
	// won't be hard), but we haven't done so yet!
	//
	//===----------------------------------------------------------------------===//

	#include "llvm/CodeGen/ELFWriter.h"
	#include "llvm/Module.h"
	#include "llvm/Target/TargetMachine.h"
	#include "llvm/Support/Mangler.h"
	using namespace llvm;

	ELFWriter::ELFWriter(std::ostream &o, TargetMachine &tm) : O(o), TM(tm) {
	e_machine = 0; // e_machine defaults to 'No Machine'
	e_flags = 0; // e_flags defaults to 0, no flags.

	is64Bit = TM.getTargetData().getPointerSizeInBits() == 64;
	isLittleEndian = TM.getTargetData().isLittleEndian();
	}

	// doInitialization - Emit the file header and all of the global variables for
	// the module to the ELF file.
	bool ELFWriter::doInitialization(Module &M) {
	Mang = new Mangler(M);

	outbyte(0x7F); // EI_MAG0
	outbyte('E'); // EI_MAG1
	outbyte('L'); // EI_MAG2
	outbyte('F'); // EI_MAG3
	outbyte(is64Bit ? 2 : 1); // EI_CLASS
	outbyte(isLittleEndian ? 1 : 2); // EI_DATA
	outbyte(1); // EI_VERSION
	for (unsigned i = OutputBuffer.size(); i != 16; ++i)
	outbyte(0); // EI_PAD up to 16 bytes.

	// This should change for shared objects.
	outhalf(1); // e_type = ET_REL
	outhalf(e_machine); // e_machine = whatever the target wants
	outword(1); // e_version = 1
	outaddr(0); // e_entry = 0 -> no entry point in .o file
	outaddr(0); // e_phoff = 0 -> no program header for .o

	ELFHeader_e_shoff_Offset = OutputBuffer.size();
	outaddr(0); // e_shoff
	outword(e_flags); // e_flags = whatever the target wants

	assert(!is64Bit && "These sizes need to be adjusted for 64-bit!");
	outhalf(52); // e_ehsize = ELF header size
	outhalf(0); // e_phentsize = prog header entry size
	outhalf(0); // e_phnum = # prog header entries = 0
	outhalf(40); // e_shentsize = sect header entry size


	ELFHeader_e_shnum_Offset = OutputBuffer.size();
	outhalf(0); // e_shnum = # of section header ents
	ELFHeader_e_shstrndx_Offset = OutputBuffer.size();
	outhalf(0); // e_shstrndx = Section # of '.shstrtab'

	// Add the null section.
	SectionList.push_back(ELFSection());

	// Start up the symbol table. The first entry in the symtab is the null
	// entry.
	SymbolTable.push_back(ELFSym(0));



	// FIXME: Should start the .text section.
	return false;
	}

	void ELFWriter::EmitGlobal(GlobalVariable *GV, ELFSection &DataSection,
	ELFSection &BSSSection) {
	// If this is an external global, emit it now. TODO: Note that it would be
	// better to ignore the symbol here and only add it to the symbol table if
	// referenced.
	if (!GV->hasInitializer()) {
	ELFSym ExternalSym(GV);
	ExternalSym.SetBind(ELFSym::STB_GLOBAL);
	ExternalSym.SetType(ELFSym::STT_NOTYPE);
	ExternalSym.SectionIdx = ELFSection::SHN_UNDEF;
	SymbolTable.push_back(ExternalSym);
	return;
	}

	const Type GVType = (const Type)GV->getType();
	unsigned Align = TM.getTargetData().getTypeAlignment(GVType);
	unsigned Size = TM.getTargetData().getTypeSize(GVType);

	// If this global has a zero initializer, it is part of the .bss or common
	// section.
	if (GV->getInitializer()->isNullValue()) {
	// If this global is part of the common block, add it now. Variables are
	// part of the common block if they are zero initialized and allowed to be
	// merged with other symbols.
	if (GV->hasLinkOnceLinkage() \|\| GV->hasWeakLinkage()) {
	ELFSym CommonSym(GV);
	// Value for common symbols is the alignment required.
	CommonSym.Value = Align;
	CommonSym.Size = Size;
	CommonSym.SetBind(ELFSym::STB_GLOBAL);
	CommonSym.SetType(ELFSym::STT_OBJECT);
	// TODO SOMEDAY: add ELF visibility.
	CommonSym.SectionIdx = ELFSection::SHN_COMMON;
	SymbolTable.push_back(CommonSym);
	return;
	}

	// Otherwise, this symbol is part of the .bss section. Emit it now.

	// Handle alignment. Ensure section is aligned at least as much as required
	// by this symbol.
	BSSSection.Align = std::max(BSSSection.Align, Align);

	// Within the section, emit enough virtual padding to get us to an alignment
	// boundary.
	if (Align)
	BSSSection.Size = (BSSSection.Size + Align - 1) & ~(Align-1);

	ELFSym BSSSym(GV);
	BSSSym.Value = BSSSection.Size;
	BSSSym.Size = Size;
	BSSSym.SetType(ELFSym::STT_OBJECT);

	switch (GV->getLinkage()) {
	default: // weak/linkonce handled above
	assert(0 && "Unexpected linkage type!");
	case GlobalValue::AppendingLinkage: // FIXME: This should be improved!
	case GlobalValue::ExternalLinkage:
	BSSSym.SetBind(ELFSym::STB_GLOBAL);
	break;
	case GlobalValue::InternalLinkage:
	BSSSym.SetBind(ELFSym::STB_LOCAL);
	break;
	}

	// Set the idx of the .bss section
	BSSSym.SectionIdx = &BSSSection-&SectionList[0];
	SymbolTable.push_back(BSSSym);

	// Reserve space in the .bss section for this symbol.
	BSSSection.Size += Size;
	return;
	}

	// FIXME: handle .rodata
	//assert(!GV->isConstant() && "unimp");

	// FIXME: handle .data
	//assert(0 && "unimp");
	}


	bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
	return false;
	}

	/// doFinalization - Now that the module has been completely processed, emit
	/// the ELF file to 'O'.
	bool ELFWriter::doFinalization(Module &M) {
	// Okay, the .text section has now been finalized.
	// FIXME: finalize the .text section.

	// Okay, the ELF header and .text sections have been completed, build the
	// .data, .bss, and "common" sections next.
	SectionList.push_back(ELFSection(".data", OutputBuffer.size()));
	SectionList.push_back(ELFSection(".bss"));
	ELFSection &DataSection = *(SectionList.end()-2);
	ELFSection &BSSSection = SectionList.back();
	for (Module::global_iterator I = M.global_begin(), E = M.global_end();
	I != E; ++I)
	EmitGlobal(I, DataSection, BSSSection);

	// Finish up the data section.
	DataSection.Type = ELFSection::SHT_PROGBITS;
	DataSection.Flags = ELFSection::SHF_WRITE \| ELFSection::SHF_ALLOC;

	// The BSS Section logically starts at the end of the Data Section (adjusted
	// to the required alignment of the BSSSection).
	BSSSection.Offset = DataSection.Offset+DataSection.Size;
	BSSSection.Type = ELFSection::SHT_NOBITS;
	BSSSection.Flags = ELFSection::SHF_WRITE \| ELFSection::SHF_ALLOC;
	if (BSSSection.Align)
	BSSSection.Offset = (BSSSection.Offset+BSSSection.Align-1) &
	~(BSSSection.Align-1);

	// Emit the symbol table now, if non-empty.
	EmitSymbolTable();

	// FIXME: Emit the relocations now.

	// Emit the string table for the sections in the ELF file we have.
	EmitSectionTableStringTable();

	// Emit the .o file section table.
	EmitSectionTable();

	// Emit the .o file to the specified stream.
	O.write((char*)&OutputBuffer[0], OutputBuffer.size());

	// Free the output buffer.
	std::vector<unsigned char>().swap(OutputBuffer);

	// Release the name mangler object.
	delete Mang; Mang = 0;
	return false;
	}

	/// EmitSymbolTable - If the current symbol table is non-empty, emit the string
	/// table for it and then the symbol table itself.
	void ELFWriter::EmitSymbolTable() {
	if (SymbolTable.size() == 1) return; // Only the null entry.

	// FIXME: compact all local symbols to the start of the symtab.
	unsigned FirstNonLocalSymbol = 1;

	SectionList.push_back(ELFSection(".strtab", OutputBuffer.size()));
	ELFSection &StrTab = SectionList.back();
	StrTab.Type = ELFSection::SHT_STRTAB;
	StrTab.Align = 1;

	// Set the zero'th symbol to a null byte, as required.
	outbyte(0);
	SymbolTable[0].NameIdx = 0;
	unsigned Index = 1;
	for (unsigned i = 1, e = SymbolTable.size(); i != e; ++i) {
	// Use the name mangler to uniquify the LLVM symbol.
	std::string Name = Mang->getValueName(SymbolTable[i].GV);

	if (Name.empty()) {
	SymbolTable[i].NameIdx = 0;
	} else {
	SymbolTable[i].NameIdx = Index;

	// Add the name to the output buffer, including the null terminator.
	OutputBuffer.insert(OutputBuffer.end(), Name.begin(), Name.end());

	// Add a null terminator.
	OutputBuffer.push_back(0);

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

	StrTab.Size = OutputBuffer.size()-StrTab.Offset;

	// Now that we have emitted the string table and know the offset into the
	// string table of each symbol, emit the symbol table itself.
	assert(!is64Bit && "Should this be 8 byte aligned for 64-bit?"
	" (check .Align below also)");
	align(4);

	SectionList.push_back(ELFSection(".symtab", OutputBuffer.size()));
	ELFSection &SymTab = SectionList.back();
	SymTab.Type = ELFSection::SHT_SYMTAB;
	SymTab.Align = 4; // FIXME: check for ELF64
	SymTab.Link = SectionList.size()-2; // Section Index of .strtab.
	SymTab.Info = FirstNonLocalSymbol; // First non-STB_LOCAL symbol.
	SymTab.EntSize = 16; // Size of each symtab entry. FIXME: wrong for ELF64

	assert(!is64Bit && "check this!");
	for (unsigned i = 0, e = SymbolTable.size(); i != e; ++i) {
	ELFSym &Sym = SymbolTable[i];
	outword(Sym.NameIdx);
	outaddr(Sym.Value);
	outword(Sym.Size);
	outbyte(Sym.Info);
	outbyte(Sym.Other);
	outhalf(Sym.SectionIdx);
	}

	SymTab.Size = OutputBuffer.size()-SymTab.Offset;
	}

	/// 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:
	SectionList.push_back(ELFSection(".shstrtab", OutputBuffer.size()));
	SectionList.back().Type = ELFSection::SHT_STRTAB;

	// Now that we know which section number is the .shstrtab section, update the
	// e_shstrndx entry in the ELF header.
	fixhalf(SectionList.size()-1, ELFHeader_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 (unsigned i = 0, e = SectionList.size(); i != e; ++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.
	SectionList[i].NameIdx = Index;

	// Add the name to the output buffer, including the null terminator.
	OutputBuffer.insert(OutputBuffer.end(), SectionList[i].Name.begin(),
	SectionList[i].Name.end());
	// Add a null terminator.
	OutputBuffer.push_back(0);

	// Keep track of the number of bytes emitted to this section.
	Index += SectionList[i].Name.size()+1;
	}

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

	/// EmitSectionTable - Now that we have emitted the entire contents of the file
	/// (all of the sections), emit the section table which informs the reader where
	/// the boundaries are.
	void ELFWriter::EmitSectionTable() {
	// Now that all of the sections have been emitted, set the e_shnum entry in
	// the ELF header.
	fixhalf(SectionList.size(), ELFHeader_e_shnum_Offset);

	// Now that we know the offset in the file of the section table (which we emit
	// next), update the e_shoff address in the ELF header.
	fixaddr(OutputBuffer.size(), ELFHeader_e_shoff_Offset);

	// Emit all of the section table entries.
	for (unsigned i = 0, e = SectionList.size(); i != e; ++i) {
	const ELFSection &S = SectionList[i];
	outword(S.NameIdx); // sh_name - Symbol table name idx
	outword(S.Type); // sh_type - Section contents & semantics
	outword(S.Flags); // sh_flags - Section flags.
	outaddr(S.Addr); // sh_addr - The mem address this section appears in.
	outaddr(S.Offset); // sh_offset - The offset from the start of the file.
	outword(S.Size); // sh_size - The section size.
	outword(S.Link); // sh_link - Section header table index link.
	outword(S.Info); // sh_info - Auxillary information.
	outword(S.Align); // sh_addralign - Alignment of section.
	outword(S.EntSize); // sh_entsize - Size of each entry in the section.
	}

	// Release the memory allocated for the section list.
	std::vector<ELFSection>().swap(SectionList);
	}