[llvm-commits] CVS: llvm/include/llvm/CodeGen/MachOWriter.h

Nate Begeman natebegeman at mac.com
Wed Aug 23 14:09:13 PDT 2006



Changes in directory llvm/include/llvm/CodeGen:

MachOWriter.h added (r1.1)
---
Log message:

Initial checkin of the Mach-O emitter.  There's plenty of fixmes, but it
does emit linkable .o files in very simple cases.


---
Diffs of the changes:  (+600 -0)

 MachOWriter.h |  600 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 600 insertions(+)


Index: llvm/include/llvm/CodeGen/MachOWriter.h
diff -c /dev/null llvm/include/llvm/CodeGen/MachOWriter.h:1.1
*** /dev/null	Wed Aug 23 16:09:02 2006
--- llvm/include/llvm/CodeGen/MachOWriter.h	Wed Aug 23 16:08:52 2006
***************
*** 0 ****
--- 1,600 ----
+ //=== MachOWriter.h - Target-independent Mach-O writer support --*- C++ -*-===//
+ //
+ //                     The LLVM Compiler Infrastructure
+ //
+ // This file was developed by Chris Lattner and is distributed under the
+ // University of Illinois Open Source License. See LICENSE.TXT for details.
+ //
+ //===----------------------------------------------------------------------===//
+ //
+ // This file defines the MachOWriter class.
+ //
+ //===----------------------------------------------------------------------===//
+ 
+ #ifndef LLVM_CODEGEN_MACHOWRITER_H
+ #define LLVM_CODEGEN_MACHOWRITER_H
+ 
+ #include "llvm/CodeGen/MachineRelocation.h"
+ #include "llvm/CodeGen/MachineFunctionPass.h"
+ #include <list>
+ 
+ namespace llvm {
+   class GlobalVariable;
+   class Mangler;
+   class MachineCodeEmitter;
+   class MachOCodeEmitter;
+ 
+   /// MachOWriter - This class implements the common target-independent code for
+   /// writing Mach-O files.  Targets should derive a class from this to
+   /// parameterize the output format.
+   ///
+   class MachOWriter : public MachineFunctionPass {
+     friend class MachOCodeEmitter;
+   public:
+     MachineCodeEmitter &getMachineCodeEmitter() const {
+       return *(MachineCodeEmitter*)MCE;
+     }
+ 
+     ~MachOWriter();
+ 
+     typedef std::vector<unsigned char> DataBuffer;
+ 
+   protected:
+     MachOWriter(std::ostream &O, TargetMachine &TM);
+ 
+     /// Output stream to send the resultant object file to.
+     ///
+     std::ostream &O;
+ 
+     /// Target machine description.
+     ///
+     TargetMachine &TM;
+ 
+     /// Mang - The object used to perform name mangling for this module.
+     ///
+     Mangler *Mang;
+ 
+     /// MCE - The MachineCodeEmitter object that we are exposing to emit machine
+     /// code for functions to the .o file.
+     MachOCodeEmitter *MCE;
+ 
+     /// is64Bit/isLittleEndian - This information is inferred from the target
+     /// machine directly, indicating what header values and flags to set.
+     bool is64Bit, isLittleEndian;
+ 
+     /// doInitialization - Emit the file header and all of the global variables
+     /// for the module to the Mach-O file.
+     bool doInitialization(Module &M);
+ 
+     bool runOnMachineFunction(MachineFunction &MF);
+ 
+     /// doFinalization - Now that the module has been completely processed, emit
+     /// the Mach-O file to 'O'.
+     bool doFinalization(Module &M);
+ 
+     /// MachOHeader - This struct contains the header information about a
+     /// specific architecture type/subtype pair that is emitted to the file.
+     struct MachOHeader {
+       uint32_t	magic;      // mach magic number identifier
+       uint32_t	cputype;    // cpu specifier
+       uint32_t	cpusubtype; // machine specifier
+       uint32_t	filetype;   // type of file
+       uint32_t	ncmds;      // number of load commands
+       uint32_t	sizeofcmds; // the size of all the load commands
+       uint32_t	flags;      // flags
+       uint32_t  reserved;   // 64-bit only
+       
+       /// HeaderData - The actual data for the header which we are building
+       /// up for emission to the file.
+       DataBuffer HeaderData;
+ 
+       // Constants for the cputype field
+       // see <mach/machine.h>
+       enum { CPU_TYPE_I386      = 7,
+              CPU_TYPE_X86_64    = 7 | 0x1000000,
+              CPU_TYPE_ARM       = 12,
+              CPU_TYPE_SPARC     = 14,
+              CPU_TYPE_POWERPC   = 18,
+              CPU_TYPE_POWERPC64 = 18 | 0x1000000
+       };
+       
+       // Constants for the cpusubtype field
+       // see <mach/machine.h>
+       enum { CPU_SUBTYPE_I386_ALL    = 3,
+              CPU_SUBTYPE_X86_64_ALL  = 3,
+              CPU_SUBTYPE_ARM_ALL     = 0,
+              CPU_SUBTYPE_SPARC_ALL   = 0,
+              CPU_SUBTYPE_POWERPC_ALL = 0
+       };
+              
+       // Constants for the filetype field
+       // see <mach-o/loader.h> for additional info on the various types
+       enum { MH_OBJECT     = 1, // relocatable object file
+              MH_EXECUTE    = 2, // demand paged executable file
+              MH_FVMLIB     = 3, // fixed VM shared library file
+              MH_CORE       = 4, // core file
+              MH_PRELOAD    = 5, // preloaded executable file
+              MH_DYLIB      = 6, // dynamically bound shared library
+              MH_DYLINKER   = 7, // dynamic link editor
+              MH_BUNDLE     = 8, // dynamically bound bundle file
+              MH_DYLIB_STUB = 9, // shared library stub for static linking only
+              MH_DSYM       = 10 // companion file wiht only debug sections
+       };
+       
+       // Constants for the flags field
+       enum { MH_NOUNDEFS                = 1 << 0,
+                 // the object file has no undefined references
+              MH_INCRLINK                = 1 << 1,
+                 // the object file is the output of an incremental link against
+                 // a base file and cannot be link edited again
+              MH_DYLDLINK                = 1 << 2,
+                 // the object file is input for the dynamic linker and cannot be
+                 // statically link edited again.
+              MH_BINDATLOAD              = 1 << 3,
+                 // the object file's undefined references are bound by the
+                 // dynamic linker when loaded.
+              MH_PREBOUND                = 1 << 4,
+                 // the file has its dynamic undefined references prebound
+              MH_SPLIT_SEGS              = 1 << 5,
+                 // the file has its read-only and read-write segments split
+                 // see <mach/shared_memory_server.h>
+              MH_LAZY_INIT               = 1 << 6,
+                 // the shared library init routine is to be run lazily via
+                 // catching memory faults to its writable segments (obsolete)
+              MH_TWOLEVEL                = 1 << 7,
+                 // the image is using two-level namespace bindings
+              MH_FORCE_FLAT              = 1 << 8,
+                 // the executable is forcing all images to use flat namespace
+                 // bindings.
+              MH_NOMULTIDEFS             = 1 << 8,
+                 // this umbrella guarantees no multiple definitions of symbols
+                 // in its sub-images so the two-level namespace hints can
+                 // always be used.
+              MH_NOFIXPREBINDING         = 1 << 10,
+                 // do not have dyld notify the prebidning agent about this
+                 // executable.
+              MH_PREBINDABLE             = 1 << 11,
+                 // the binary is not prebound but can have its prebinding
+                 // redone.  only used when MH_PREBOUND is not set.
+              MH_ALLMODSBOUND            = 1 << 12,
+                 // indicates that this binary binds to all two-level namespace
+                 // modules of its dependent libraries.  Only used when
+                 // MH_PREBINDABLE and MH_TWOLEVEL are both set.
+              MH_SUBSECTIONS_VIA_SYMBOLS = 1 << 13,
+                 // safe to divide up the sections into sub-sections via symbols
+                 // for dead code stripping.
+              MH_CANONICAL               = 1 << 14,
+                 // the binary has been canonicalized via the unprebind operation
+              MH_WEAK_DEFINES            = 1 << 15,
+                 // the final linked image contains external weak symbols
+              MH_BINDS_TO_WEAK           = 1 << 16,
+                 // the final linked image uses weak symbols
+              MH_ALLOW_STACK_EXECUTION   = 1 << 17
+                 // When this bit is set, all stacks in the task will be given
+                 // stack execution privilege.  Only used in MH_EXECUTE filetype
+       };
+ 
+       MachOHeader() : magic(0), cputype(0), cpusubtype(0), filetype(0),
+                       ncmds(0), sizeofcmds(0), flags(0), reserved(0) { }
+       
+       /// cmdSize - This routine returns the size of the MachOSection as written
+       /// to disk, depending on whether the destination is a 64 bit Mach-O file.
+       unsigned cmdSize(bool is64Bit) const {
+         if (is64Bit)
+           return 8 * sizeof(uint32_t);
+         else
+           return 7 * sizeof(uint32_t);
+       }
+ 
+       /// setMagic - This routine sets the appropriate value for the 'magic'
+       /// field based on pointer size and endianness.
+       void setMagic(bool isLittleEndian, bool is64Bit) {
+         if (isLittleEndian)
+           if (is64Bit) magic = 0xcffaedfe;
+           else         magic = 0xcefaedfe;
+         else
+           if (is64Bit) magic = 0xfeedfacf;
+           else         magic = 0xfeedface;
+       }
+     };
+     
+     /// Header - An instance of MachOHeader that we will update while we build
+     /// the file, and then emit during finalization.
+     MachOHeader Header;
+     
+   private:
+ 
+     /// MachOSegment - This struct contains the necessary information to
+     /// emit the load commands for each section in the file.
+     struct MachOSegment {
+       uint32_t    cmd;      // LC_SEGMENT or LC_SEGMENT_64
+       uint32_t    cmdsize;  // Total size of this struct and section commands
+       std::string segname;  // segment name
+       uint64_t    vmaddr;   // address of this segment
+       uint64_t    vmsize;   // size of this segment, may be larger than filesize
+       uint64_t    fileoff;  // offset in file
+       uint64_t    filesize; // amount to read from file
+       uint32_t    maxprot;  // maximum VM protection
+       uint32_t    initprot; // initial VM protection
+       uint32_t    nsects;   // number of sections in this segment
+       uint32_t    flags;    // flags
+       
+       // Constants for the vm protection fields
+       // see <mach-o/vm_prot.h>
+       enum { VM_PROT_NONE    = 0x00, 
+              VM_PROT_READ    = 0x01, // read permission
+              VM_PROT_WRITE   = 0x02, // write permission
+              VM_PROT_EXECUTE = 0x04, // execute permission,
+              VM_PROT_ALL     = 0x07
+       };
+       
+       // Constants for the cmd field
+       // see <mach-o/loader.h>
+       enum { LC_SEGMENT    = 0x01,  // segment of this file to be mapped
+              LC_SEGMENT_64 = 0x19   // 64-bit segment of this file to be mapped
+       };
+       
+       /// cmdSize - This routine returns the size of the MachOSection as written
+       /// to disk, depending on whether the destination is a 64 bit Mach-O file.
+       unsigned cmdSize(bool is64Bit) const {
+         if (is64Bit)
+           return 6 * sizeof(uint32_t) + 4 * sizeof(uint64_t) + 16;
+         else
+           return 10 * sizeof(uint32_t) + 16;  // addresses only 32 bits
+       }
+ 
+       MachOSegment(const std::string &seg, bool is64Bit)
+         : cmd(is64Bit ? LC_SEGMENT_64 : LC_SEGMENT), cmdsize(0), segname(seg),
+           vmaddr(0), vmsize(0), fileoff(0), filesize(0), maxprot(VM_PROT_ALL),
+           initprot(VM_PROT_ALL), nsects(0), flags(0) { }
+     };
+ 
+     /// MachOSection - This struct contains information about each section in a 
+     /// particular segment that is emitted to the file.  This is eventually
+     /// turned into the SectionCommand in the load command for a particlar
+     /// segment.
+     struct MachOSection { 
+       std::string sectname; // name of this section, 
+       std::string	segname;  // segment this section goes in
+       uint64_t	addr;       // memory address of this section
+       uint64_t	size;       // size in bytes of this section
+       uint32_t	offset;     // file offset of this section
+       uint32_t	align;      // section alignment (power of 2)
+       uint32_t	reloff;     // file offset of relocation entries
+       uint32_t	nreloc;     // number of relocation entries
+       uint32_t	flags;      // flags (section type and attributes)
+       uint32_t	reserved1;  // reserved (for offset or index)
+       uint32_t	reserved2;  // reserved (for count or sizeof)
+       uint32_t	reserved3;  // reserved (64 bit only)
+       
+       /// A unique number for this section, which will be used to match symbols
+       /// to the correct section.
+       uint32_t Index;
+       
+       /// SectionData - The actual data for this section which we are building
+       /// up for emission to the file.
+       DataBuffer SectionData;
+       
+       // Constants for the section types (low 8 bits of flags field)
+       // see <mach-o/loader.h>
+       enum { S_REGULAR = 0,
+                 // regular section
+              S_ZEROFILL = 1,
+                 // zero fill on demand section
+              S_CSTRING_LITERALS = 2,
+                 // section with only literal C strings
+              S_4BYTE_LITERALS = 3,
+                 // section with only 4 byte literals
+              S_8BYTE_LITERALS = 4,
+                 // section with only 8 byte literals
+              S_LITERAL_POINTERS = 5, 
+                 // section with only pointers to literals
+              S_NON_LAZY_SYMBOL_POINTERS = 6,
+                 // section with only non-lazy symbol pointers
+              S_LAZY_SYMBOL_POINTERS = 7,
+                 // section with only lazy symbol pointers
+              S_SYMBOL_STUBS = 8,
+                 // section with only symbol stubs
+                 // byte size of stub in the reserved2 field
+              S_MOD_INIT_FUNC_POINTERS = 9,
+                 // section with only function pointers for initialization
+              S_MOD_TERM_FUNC_POINTERS = 10,
+                 // section with only function pointers for termination
+              S_COALESCED = 11,
+                 // section contains symbols that are coalesced
+              S_GB_ZEROFILL = 12,
+                 // zero fill on demand section (that can be larger than 4GB)
+              S_INTERPOSING = 13,
+                 // section with only pairs of function pointers for interposing
+              S_16BYTE_LITERALS = 14
+                 // section with only 16 byte literals
+       };
+       
+       // Constants for the section flags (high 24 bits of flags field)
+       // see <mach-o/loader.h>
+       enum { S_ATTR_PURE_INSTRUCTIONS   = 1 << 31,
+                 // section contains only true machine instructions
+              S_ATTR_NO_TOC              = 1 << 30,
+                 // section contains coalesced symbols that are not to be in a 
+                 // ranlib table of contents
+              S_ATTR_STRIP_STATIC_SYMS   = 1 << 29,
+                 // ok to strip static symbols in this section in files with the
+                 // MY_DYLDLINK flag
+              S_ATTR_NO_DEAD_STRIP       = 1 << 28,
+                 // no dead stripping
+              S_ATTR_LIVE_SUPPORT        = 1 << 27,
+                 // blocks are live if they reference live blocks
+              S_ATTR_SELF_MODIFYING_CODE = 1 << 26,
+                 // used with i386 code stubs written on by dyld
+              S_ATTR_DEBUG               = 1 << 25,
+                 // a debug section
+              S_ATTR_SOME_INSTRUCTIONS   = 1 << 10,
+                 // section contains some machine instructions
+              S_ATTR_EXT_RELOC           = 1 << 9,
+                 // section has external relocation entries
+              S_ATTR_LOC_RELOC           = 1 << 8
+                 // section has local relocation entries
+       };
+ 
+       /// cmdSize - This routine returns the size of the MachOSection as written
+       /// to disk, depending on whether the destination is a 64 bit Mach-O file.
+       unsigned cmdSize(bool is64Bit) const {
+         if (is64Bit)
+           return 7 * sizeof(uint32_t) + 2 * sizeof(uint64_t) + 32;
+         else
+           return 9 * sizeof(uint32_t) + 32;  // addresses only 32 bits
+       }
+ 
+       MachOSection(const std::string &seg, const std::string &sect)
+         : sectname(sect), segname(seg), addr(0), size(0), offset(0), align(0),
+           reloff(0), nreloc(0), flags(0), reserved1(0), reserved2(0),
+           reserved3(0) { }
+     };
+ 
+     /// SectionList - This is the list of sections that we have emitted to the
+     /// file.  Once the file has been completely built, the segment load command
+     /// SectionCommands are constructed from this info.
+     std::list<MachOSection> SectionList;
+ 
+     /// SectionLookup - This is a mapping from section name to SectionList entry
+     std::map<std::string, MachOSection*> SectionLookup;
+ 
+     /// getSection - Return the section with the specified name, creating a new
+     /// section if one does not already exist.
+     MachOSection &getSection(const std::string &seg, const std::string &sect,
+                              unsigned Flags = 0) {
+       MachOSection *&SN = SectionLookup[seg+sect];
+       if (SN) return *SN;
+ 
+       SectionList.push_back(MachOSection(seg, sect));
+       SN = &SectionList.back();
+       SN->Index = SectionList.size();
+       SN->flags = MachOSection::S_REGULAR | Flags;
+       return *SN;
+     }
+     MachOSection &getTextSection() {
+       return getSection("__TEXT", "__text", 
+                         MachOSection::S_ATTR_PURE_INSTRUCTIONS |
+                         MachOSection::S_ATTR_SOME_INSTRUCTIONS);
+     }
+     
+     /// MachOSymTab - This struct contains information about the offsets and 
+     /// size of symbol table information.
+     /// segment.
+     struct MachOSymTab {
+       uint32_t cmd;     // LC_SYMTAB
+       uint32_t cmdsize; // sizeof( MachOSymTab )
+       uint32_t symoff;  // symbol table offset
+       uint32_t nsyms;   // number of symbol table entries
+       uint32_t stroff;  // string table offset
+       uint32_t strsize; // string table size in bytes
+ 
+       // Constants for the cmd field
+       // see <mach-o/loader.h>
+       enum { LC_SYMTAB = 0x02  // link-edit stab symbol table info
+       };
+       
+       MachOSymTab() : cmd(LC_SYMTAB), cmdsize(6 * sizeof(uint32_t)), symoff(0),
+         nsyms(0), stroff(0), strsize(0) { }
+     };
+     
+     /// MachOSymTab - This struct contains information about the offsets and 
+     /// size of symbol table information.
+     /// segment.
+     struct MachODySymTab {
+       uint32_t cmd;             // LC_DYSYMTAB
+       uint32_t cmdsize;         // sizeof( MachODySymTab )
+       uint32_t ilocalsym;       // index to local symbols
+       uint32_t nlocalsym;       // number of local symbols
+       uint32_t iextdefsym;      // index to externally defined symbols
+       uint32_t nextdefsym;      // number of externally defined symbols
+       uint32_t iundefsym;       // index to undefined symbols
+       uint32_t nundefsym;       // number of undefined symbols
+       uint32_t tocoff;          // file offset to table of contents
+       uint32_t ntoc;            // number of entries in table of contents
+       uint32_t modtaboff;       // file offset to module table
+       uint32_t nmodtab;         // number of module table entries
+       uint32_t extrefsymoff;    // offset to referenced symbol table
+       uint32_t nextrefsyms;     // number of referenced symbol table entries
+       uint32_t indirectsymoff;  // file offset to the indirect symbol table
+       uint32_t nindirectsyms;   // number of indirect symbol table entries
+       uint32_t extreloff;       // offset to external relocation entries
+       uint32_t nextrel;         // number of external relocation entries
+       uint32_t locreloff;       // offset to local relocation entries
+       uint32_t nlocrel;         // number of local relocation entries
+ 
+       // Constants for the cmd field
+       // see <mach-o/loader.h>
+       enum { LC_DYSYMTAB = 0x0B  // dynamic link-edit symbol table info
+       };
+       
+       MachODySymTab() : cmd(LC_DYSYMTAB), cmdsize(20 * sizeof(uint32_t)),
+         ilocalsym(0), nlocalsym(0), iextdefsym(0), nextdefsym(0),
+         iundefsym(0), nundefsym(0), tocoff(0), ntoc(0), modtaboff(0),
+         nmodtab(0), extrefsymoff(0), nextrefsyms(0), indirectsymoff(0),
+         nindirectsyms(0), extreloff(0), nextrel(0), locreloff(0), nlocrel(0) { }
+     };
+     
+     /// SymTab - The "stab" style symbol table information
+     MachOSymTab   SymTab;     
+     /// DySymTab - symbol table info for the dynamic link editor
+     MachODySymTab DySymTab;
+ 
+     /// MachOSym - This struct contains information about each symbol that is
+     /// added to logical symbol table for the module.  This is eventually
+     /// turned into a real symbol table in the file.
+     struct MachOSym {
+       const GlobalValue *GV;    // The global value this corresponds to.
+       uint32_t  n_strx;         // index into the string table
+       uint8_t   n_type;         // type flag
+       uint8_t   n_sect;         // section number or NO_SECT
+       int16_t   n_desc;         // see <mach-o/stab.h>
+       uint64_t  n_value;        // value for this symbol (or stab offset)
+       
+       // Constants for the n_sect field
+       // see <mach-o/nlist.h>
+       enum { NO_SECT = 0 };   // symbol is not in any section
+ 
+       // Constants for the n_type field
+       // see <mach-o/nlist.h>
+       enum { N_UNDF  = 0x0,  // undefined, n_sect == NO_SECT
+              N_ABS   = 0x2,  // absolute, n_sect == NO_SECT
+              N_SECT  = 0xe,  // defined in section number n_sect
+              N_PBUD  = 0xc,  // prebound undefined (defined in a dylib)
+              N_INDR  = 0xa   // indirect
+       };
+       // The following bits are OR'd into the types above. For example, a type
+       // of 0x0f would be an external N_SECT symbol (0x0e | 0x01).
+       enum { N_EXT  = 0x01,   // external symbol bit
+              N_PEXT = 0x10    // private external symbol bit
+       };
+       
+       // Constants for the n_desc field
+       // see <mach-o/loader.h>
+       enum { REFERENCE_FLAG_UNDEFINED_NON_LAZY          = 0,
+              REFERENCE_FLAG_UNDEFINED_LAZY              = 1,
+              REFERENCE_FLAG_DEFINED                     = 2,
+              REFERENCE_FLAG_PRIVATE_DEFINED             = 3,
+              REFERENCE_FLAG_PRIVATE_UNDEFINED_NON_LAZY  = 4,
+              REFERENCE_FLAG_PRIVATE_UNDEFINED_LAZY      = 5
+       };
+       enum { N_NO_DEAD_STRIP = 0x0020, // symbol is not to be dead stripped
+              N_WEAK_REF      = 0x0040, // symbol is weak referenced
+              N_WEAK_DEF      = 0x0080  // coalesced symbol is a weak definition
+       };
+       
+       /// entrySize - This routine returns the size of a symbol table entry as
+       /// written to disk.
+       static unsigned entrySize() { return 12; }
+ 
+       MachOSym(const GlobalValue *gv, uint8_t sect) : GV(gv), n_strx(0), 
+         n_type(N_UNDF), n_sect(sect), n_desc(0), n_value(0) {}
+     };
+ 
+     /// SymbolTable - This is the list of symbols we have emitted to the file.
+     /// This actually gets rearranged before emission to the file (to put the
+     /// local symbols first in the list).
+     std::vector<MachOSym> SymbolTable;
+     
+     /// DynamicSymbolTable - This is just a vector of indices into
+     /// SymbolTable to aid in emitting the DYSYMTAB load command.
+     std::vector<unsigned> DynamicSymbolTable;
+     
+     /// StringTable - The table of strings referenced by SymbolTable entries
+     std::vector<std::string> StringTable;
+ 
+     // align - Emit padding into the file until the current output position is
+     // aligned to the specified power of two boundary.
+     static void align(DataBuffer &Output, unsigned Boundary) {
+       assert(Boundary && (Boundary & (Boundary-1)) == 0 &&
+              "Must align to 2^k boundary");
+       size_t Size = Output.size();
+       if (Size & (Boundary-1)) {
+         // Add padding to get alignment to the correct place.
+         size_t Pad = Boundary-(Size & (Boundary-1));
+         Output.resize(Size+Pad);
+       }
+     }
+ 
+     void outbyte(DataBuffer &Output, unsigned char X) {
+       Output.push_back(X);
+     }
+     void outhalf(DataBuffer &Output, unsigned short X) {
+       if (isLittleEndian) {
+         Output.push_back(X&255);
+         Output.push_back(X >> 8);
+       } else {
+         Output.push_back(X >> 8);
+         Output.push_back(X&255);
+       }
+     }
+     void outword(DataBuffer &Output, unsigned X) {
+       if (isLittleEndian) {
+         Output.push_back((X >>  0) & 255);
+         Output.push_back((X >>  8) & 255);
+         Output.push_back((X >> 16) & 255);
+         Output.push_back((X >> 24) & 255);
+       } else {
+         Output.push_back((X >> 24) & 255);
+         Output.push_back((X >> 16) & 255);
+         Output.push_back((X >>  8) & 255);
+         Output.push_back((X >>  0) & 255);
+       }
+     }
+     void outxword(DataBuffer &Output, uint64_t X) {
+       if (isLittleEndian) {
+         Output.push_back(unsigned(X >>  0) & 255);
+         Output.push_back(unsigned(X >>  8) & 255);
+         Output.push_back(unsigned(X >> 16) & 255);
+         Output.push_back(unsigned(X >> 24) & 255);
+         Output.push_back(unsigned(X >> 32) & 255);
+         Output.push_back(unsigned(X >> 40) & 255);
+         Output.push_back(unsigned(X >> 48) & 255);
+         Output.push_back(unsigned(X >> 56) & 255);
+       } else {
+         Output.push_back(unsigned(X >> 56) & 255);
+         Output.push_back(unsigned(X >> 48) & 255);
+         Output.push_back(unsigned(X >> 40) & 255);
+         Output.push_back(unsigned(X >> 32) & 255);
+         Output.push_back(unsigned(X >> 24) & 255);
+         Output.push_back(unsigned(X >> 16) & 255);
+         Output.push_back(unsigned(X >>  8) & 255);
+         Output.push_back(unsigned(X >>  0) & 255);
+       }
+     }
+     void outaddr32(DataBuffer &Output, unsigned X) {
+       outword(Output, X);
+     }
+     void outaddr64(DataBuffer &Output, uint64_t X) {
+       outxword(Output, X);
+     }
+     void outaddr(DataBuffer &Output, uint64_t X) {
+       if (!is64Bit)
+         outword(Output, (unsigned)X);
+       else
+         outxword(Output, X);
+     }
+     void outstring(DataBuffer &Output, std::string &S, unsigned Length) {
+       char *buffer = (char *)calloc(1, Length);
+       unsigned i;
+       // FIXME: it is unclear if mach-o requires null terminated strings, or
+       //        if a string of 16 bytes with no null terminator is ok.  If so,
+       //        we should switch to strncpy.
+       strlcpy(buffer, S.c_str(), Length);
+       
+       for (i = 0; i < Length; ++i)
+         outbyte(Output, buffer[i]);
+       
+       free(buffer);
+     }
+   private:
+     void EmitGlobal(GlobalVariable *GV);
+     void EmitHeaderAndLoadCommands();
+     void EmitSections();
+     void EmitRelocations();
+     void EmitSymbolTable();
+     void EmitStringTable();
+   };
+ }
+ 
+ #endif






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