Fix Mac Breakpad host tools to build in Linux cross-compile

We're working on building our Firefox Mac builds as a Linux cross-compile
(https://bugzilla.mozilla.org/show_bug.cgi?id=921040) and we need symbol
dumping to work. This change ports the Mac dump_syms tool to build and work
on Linux. I've tested it and it produces identical output to running the
tool on Mac.

The bulk of the work here was converting src/common/mac/dump_syms.mm and
src/tools/mac/dump_syms/dump_syms_tool.mm from ObjC++ to C++ and removing
their use of Foundation classes in favor of standard C/C++.

This won't compile out-of-the-box on Linux, it requires some Mac system
headers that are not included in this patch. I have those tentatively in
a separate patch to land in Gecko
(http://hg.mozilla.org/users/tmielczarek_mozilla.com/mc/rev/5fb8da23c83c),
but I wasn't sure if you'd be interested in having them in the Breakpad tree.
We could almost certainly pare down the set of headers included there, I
didn't spend too much time trying to minimize them (we primarily just need
the Mach-O structs and a few associated bits).

I just realized that this patch is missing updating the XCode project files
(ugh). I'll fix that up in a bit.

R=mark@chromium.org
BUG=https://bugzilla.mozilla.org/show_bug.cgi?id=543111

Review URL: https://codereview.chromium.org/1340543002 .

1 files changed, 1402 insertions, 0 deletions

diff --git a/src/third_party/mac_headers/mach-o/loader.h b/src/third_party/mac_headers/mach-o/loader.h
new file mode 100644
index 00000000..ff18e29c
--- /dev/null
+++ b/src/third_party/mac_headers/mach-o/loader.h
@@ -0,0 +1,1402 @@
+/*
+ * Copyright (c) 1999-2010 Apple Inc.  All Rights Reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ * 
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ * 
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ * 
+ * @APPLE_LICENSE_HEADER_END@
+ */
+#ifndef _MACHO_LOADER_H_
+#define _MACHO_LOADER_H_
+
+/*
+ * This file describes the format of mach object files.
+ */
+#include <stdint.h>
+
+/*
+ * <mach/machine.h> is needed here for the cpu_type_t and cpu_subtype_t types
+ * and contains the constants for the possible values of these types.
+ */
+#include <mach/machine.h>
+
+/*
+ * <mach/vm_prot.h> is needed here for the vm_prot_t type and contains the 
+ * constants that are or'ed together for the possible values of this type.
+ */
+#include <mach/vm_prot.h>
+
+/*
+ * <machine/thread_status.h> is expected to define the flavors of the thread
+ * states and the structures of those flavors for each machine.
+ */
+#include <mach/machine/thread_status.h>
+#include <architecture/byte_order.h>
+
+/*
+ * The 32-bit mach header appears at the very beginning of the object file for
+ * 32-bit architectures.
+ */
+struct mach_header {
+	uint32_t	magic;		/* mach magic number identifier */
+	cpu_type_t	cputype;	/* cpu specifier */
+	cpu_subtype_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 */
+};
+
+/* Constant for the magic field of the mach_header (32-bit architectures) */
+#define	MH_MAGIC	0xfeedface	/* the mach magic number */
+#define MH_CIGAM	0xcefaedfe	/* NXSwapInt(MH_MAGIC) */
+
+/*
+ * The 64-bit mach header appears at the very beginning of object files for
+ * 64-bit architectures.
+ */
+struct mach_header_64 {
+	uint32_t	magic;		/* mach magic number identifier */
+	cpu_type_t	cputype;	/* cpu specifier */
+	cpu_subtype_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;	/* reserved */
+};
+
+/* Constant for the magic field of the mach_header_64 (64-bit architectures) */
+#define MH_MAGIC_64 0xfeedfacf /* the 64-bit mach magic number */
+#define MH_CIGAM_64 0xcffaedfe /* NXSwapInt(MH_MAGIC_64) */
+
+/*
+ * The layout of the file depends on the filetype.  For all but the MH_OBJECT
+ * file type the segments are padded out and aligned on a segment alignment
+ * boundary for efficient demand pageing.  The MH_EXECUTE, MH_FVMLIB, MH_DYLIB,
+ * MH_DYLINKER and MH_BUNDLE file types also have the headers included as part
+ * of their first segment.
+ * 
+ * The file type MH_OBJECT is a compact format intended as output of the
+ * assembler and input (and possibly output) of the link editor (the .o
+ * format).  All sections are in one unnamed segment with no segment padding. 
+ * This format is used as an executable format when the file is so small the
+ * segment padding greatly increases its size.
+ *
+ * The file type MH_PRELOAD is an executable format intended for things that
+ * are not executed under the kernel (proms, stand alones, kernels, etc).  The
+ * format can be executed under the kernel but may demand paged it and not
+ * preload it before execution.
+ *
+ * A core file is in MH_CORE format and can be any in an arbritray legal
+ * Mach-O file.
+ *
+ * Constants for the filetype field of the mach_header
+ */
+#define	MH_OBJECT	0x1		/* relocatable object file */
+#define	MH_EXECUTE	0x2		/* demand paged executable file */
+#define	MH_FVMLIB	0x3		/* fixed VM shared library file */
+#define	MH_CORE		0x4		/* core file */
+#define	MH_PRELOAD	0x5		/* preloaded executable file */
+#define	MH_DYLIB	0x6		/* dynamically bound shared library */
+#define	MH_DYLINKER	0x7		/* dynamic link editor */
+#define	MH_BUNDLE	0x8		/* dynamically bound bundle file */
+#define	MH_DYLIB_STUB	0x9		/* shared library stub for static */
+					/*  linking only, no section contents */
+#define	MH_DSYM		0xa		/* companion file with only debug */
+					/*  sections */
+#define	MH_KEXT_BUNDLE	0xb		/* x86_64 kexts */
+
+/* Constants for the flags field of the mach_header */
+#define	MH_NOUNDEFS	0x1		/* the object file has no undefined
+					   references */
+#define	MH_INCRLINK	0x2		/* the object file is the output of an
+					   incremental link against a base file
+					   and can't be link edited again */
+#define MH_DYLDLINK	0x4		/* the object file is input for the
+					   dynamic linker and can't be staticly
+					   link edited again */
+#define MH_BINDATLOAD	0x8		/* the object file's undefined
+					   references are bound by the dynamic
+					   linker when loaded. */
+#define MH_PREBOUND	0x10		/* the file has its dynamic undefined
+					   references prebound. */
+#define MH_SPLIT_SEGS	0x20		/* the file has its read-only and
+					   read-write segments split */
+#define MH_LAZY_INIT	0x40		/* the shared library init routine is
+					   to be run lazily via catching memory
+					   faults to its writeable segments
+					   (obsolete) */
+#define MH_TWOLEVEL	0x80		/* the image is using two-level name
+					   space bindings */
+#define MH_FORCE_FLAT	0x100		/* the executable is forcing all images
+					   to use flat name space bindings */
+#define MH_NOMULTIDEFS	0x200		/* this umbrella guarantees no multiple
+					   defintions of symbols in its
+					   sub-images so the two-level namespace
+					   hints can always be used. */
+#define MH_NOFIXPREBINDING 0x400	/* do not have dyld notify the
+					   prebinding agent about this
+					   executable */
+#define MH_PREBINDABLE  0x800           /* the binary is not prebound but can
+					   have its prebinding redone. only used
+                                           when MH_PREBOUND is not set. */
+#define MH_ALLMODSBOUND 0x1000		/* 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. */ 
+#define MH_SUBSECTIONS_VIA_SYMBOLS 0x2000/* safe to divide up the sections into
+					    sub-sections via symbols for dead
+					    code stripping */
+#define MH_CANONICAL    0x4000		/* the binary has been canonicalized
+					   via the unprebind operation */
+#define MH_WEAK_DEFINES	0x8000		/* the final linked image contains
+					   external weak symbols */
+#define MH_BINDS_TO_WEAK 0x10000	/* the final linked image uses
+					   weak symbols */
+
+#define MH_ALLOW_STACK_EXECUTION 0x20000/* When this bit is set, all stacks 
+					   in the task will be given stack
+					   execution privilege.  Only used in
+					   MH_EXECUTE filetypes. */
+#define MH_ROOT_SAFE 0x40000           /* When this bit is set, the binary 
+					  declares it is safe for use in
+					  processes with uid zero */
+                                         
+#define MH_SETUID_SAFE 0x80000         /* When this bit is set, the binary 
+					  declares it is safe for use in
+					  processes when issetugid() is true */
+
+#define MH_NO_REEXPORTED_DYLIBS 0x100000 /* When this bit is set on a dylib, 
+					  the static linker does not need to
+					  examine dependent dylibs to see
+					  if any are re-exported */
+#define	MH_PIE 0x200000			/* When this bit is set, the OS will
+					   load the main executable at a
+					   random address.  Only used in
+					   MH_EXECUTE filetypes. */
+#define	MH_DEAD_STRIPPABLE_DYLIB 0x400000 /* Only for use on dylibs.  When
+					     linking against a dylib that
+					     has this bit set, the static linker
+					     will automatically not create a
+					     LC_LOAD_DYLIB load command to the
+					     dylib if no symbols are being
+					     referenced from the dylib. */
+#define MH_HAS_TLV_DESCRIPTORS 0x800000 /* Contains a section of type 
+					    S_THREAD_LOCAL_VARIABLES */
+
+#define MH_NO_HEAP_EXECUTION 0x1000000	/* When this bit is set, the OS will
+					   run the main executable with
+					   a non-executable heap even on
+					   platforms (e.g. i386) that don't
+					   require it. Only used in MH_EXECUTE
+					   filetypes. */
+
+/*
+ * The load commands directly follow the mach_header.  The total size of all
+ * of the commands is given by the sizeofcmds field in the mach_header.  All
+ * load commands must have as their first two fields cmd and cmdsize.  The cmd
+ * field is filled in with a constant for that command type.  Each command type
+ * has a structure specifically for it.  The cmdsize field is the size in bytes
+ * of the particular load command structure plus anything that follows it that
+ * is a part of the load command (i.e. section structures, strings, etc.).  To
+ * advance to the next load command the cmdsize can be added to the offset or
+ * pointer of the current load command.  The cmdsize for 32-bit architectures
+ * MUST be a multiple of 4 bytes and for 64-bit architectures MUST be a multiple
+ * of 8 bytes (these are forever the maximum alignment of any load commands).
+ * The padded bytes must be zero.  All tables in the object file must also
+ * follow these rules so the file can be memory mapped.  Otherwise the pointers
+ * to these tables will not work well or at all on some machines.  With all
+ * padding zeroed like objects will compare byte for byte.
+ */
+struct load_command {
+	uint32_t cmd;		/* type of load command */
+	uint32_t cmdsize;	/* total size of command in bytes */
+};
+
+/*
+ * After MacOS X 10.1 when a new load command is added that is required to be
+ * understood by the dynamic linker for the image to execute properly the
+ * LC_REQ_DYLD bit will be or'ed into the load command constant.  If the dynamic
+ * linker sees such a load command it it does not understand will issue a
+ * "unknown load command required for execution" error and refuse to use the
+ * image.  Other load commands without this bit that are not understood will
+ * simply be ignored.
+ */
+#define LC_REQ_DYLD 0x80000000
+
+/* Constants for the cmd field of all load commands, the type */
+#define	LC_SEGMENT	0x1	/* segment of this file to be mapped */
+#define	LC_SYMTAB	0x2	/* link-edit stab symbol table info */
+#define	LC_SYMSEG	0x3	/* link-edit gdb symbol table info (obsolete) */
+#define	LC_THREAD	0x4	/* thread */
+#define	LC_UNIXTHREAD	0x5	/* unix thread (includes a stack) */
+#define	LC_LOADFVMLIB	0x6	/* load a specified fixed VM shared library */
+#define	LC_IDFVMLIB	0x7	/* fixed VM shared library identification */
+#define	LC_IDENT	0x8	/* object identification info (obsolete) */
+#define LC_FVMFILE	0x9	/* fixed VM file inclusion (internal use) */
+#define LC_PREPAGE      0xa     /* prepage command (internal use) */
+#define	LC_DYSYMTAB	0xb	/* dynamic link-edit symbol table info */
+#define	LC_LOAD_DYLIB	0xc	/* load a dynamically linked shared library */
+#define	LC_ID_DYLIB	0xd	/* dynamically linked shared lib ident */
+#define LC_LOAD_DYLINKER 0xe	/* load a dynamic linker */
+#define LC_ID_DYLINKER	0xf	/* dynamic linker identification */
+#define	LC_PREBOUND_DYLIB 0x10	/* modules prebound for a dynamically */
+				/*  linked shared library */
+#define	LC_ROUTINES	0x11	/* image routines */
+#define	LC_SUB_FRAMEWORK 0x12	/* sub framework */
+#define	LC_SUB_UMBRELLA 0x13	/* sub umbrella */
+#define	LC_SUB_CLIENT	0x14	/* sub client */
+#define	LC_SUB_LIBRARY  0x15	/* sub library */
+#define	LC_TWOLEVEL_HINTS 0x16	/* two-level namespace lookup hints */
+#define	LC_PREBIND_CKSUM  0x17	/* prebind checksum */
+
+/*
+ * load a dynamically linked shared library that is allowed to be missing
+ * (all symbols are weak imported).
+ */
+#define	LC_LOAD_WEAK_DYLIB (0x18 | LC_REQ_DYLD)
+
+#define	LC_SEGMENT_64	0x19	/* 64-bit segment of this file to be
+				   mapped */
+#define	LC_ROUTINES_64	0x1a	/* 64-bit image routines */
+#define LC_UUID		0x1b	/* the uuid */
+#define LC_RPATH       (0x1c | LC_REQ_DYLD)    /* runpath additions */
+#define LC_CODE_SIGNATURE 0x1d	/* local of code signature */
+#define LC_SEGMENT_SPLIT_INFO 0x1e /* local of info to split segments */
+#define LC_REEXPORT_DYLIB (0x1f | LC_REQ_DYLD) /* load and re-export dylib */
+#define	LC_LAZY_LOAD_DYLIB 0x20	/* delay load of dylib until first use */
+#define	LC_ENCRYPTION_INFO 0x21	/* encrypted segment information */
+#define	LC_DYLD_INFO 	0x22	/* compressed dyld information */
+#define	LC_DYLD_INFO_ONLY (0x22|LC_REQ_DYLD)	/* compressed dyld information only */
+#define	LC_LOAD_UPWARD_DYLIB (0x23 | LC_REQ_DYLD) /* load upward dylib */
+#define LC_VERSION_MIN_MACOSX 0x24   /* build for MacOSX min OS version */
+#define LC_VERSION_MIN_IPHONEOS 0x25 /* build for iPhoneOS min OS version */
+#define LC_FUNCTION_STARTS 0x26 /* compressed table of function start addresses */
+#define LC_DYLD_ENVIRONMENT 0x27 /* string for dyld to treat
+				    like environment variable */
+
+/*
+ * A variable length string in a load command is represented by an lc_str
+ * union.  The strings are stored just after the load command structure and
+ * the offset is from the start of the load command structure.  The size
+ * of the string is reflected in the cmdsize field of the load command.
+ * Once again any padded bytes to bring the cmdsize field to a multiple
+ * of 4 bytes must be zero.
+ */
+union lc_str {
+	uint32_t	offset;	/* offset to the string */
+#ifndef __LP64__
+	char		*ptr;	/* pointer to the string */
+#endif 
+};
+
+/*
+ * The segment load command indicates that a part of this file is to be
+ * mapped into the task's address space.  The size of this segment in memory,
+ * vmsize, maybe equal to or larger than the amount to map from this file,
+ * filesize.  The file is mapped starting at fileoff to the beginning of
+ * the segment in memory, vmaddr.  The rest of the memory of the segment,
+ * if any, is allocated zero fill on demand.  The segment's maximum virtual
+ * memory protection and initial virtual memory protection are specified
+ * by the maxprot and initprot fields.  If the segment has sections then the
+ * section structures directly follow the segment command and their size is
+ * reflected in cmdsize.
+ */
+struct segment_command { /* for 32-bit architectures */
+	uint32_t	cmd;		/* LC_SEGMENT */
+	uint32_t	cmdsize;	/* includes sizeof section structs */
+	char		segname[16];	/* segment name */
+	uint32_t	vmaddr;		/* memory address of this segment */
+	uint32_t	vmsize;		/* memory size of this segment */
+	uint32_t	fileoff;	/* file offset of this segment */
+	uint32_t	filesize;	/* amount to map from the file */
+	vm_prot_t	maxprot;	/* maximum VM protection */
+	vm_prot_t	initprot;	/* initial VM protection */
+	uint32_t	nsects;		/* number of sections in segment */
+	uint32_t	flags;		/* flags */
+};
+
+/*
+ * The 64-bit segment load command indicates that a part of this file is to be
+ * mapped into a 64-bit task's address space.  If the 64-bit segment has
+ * sections then section_64 structures directly follow the 64-bit segment
+ * command and their size is reflected in cmdsize.
+ */
+struct segment_command_64 { /* for 64-bit architectures */
+	uint32_t	cmd;		/* LC_SEGMENT_64 */
+	uint32_t	cmdsize;	/* includes sizeof section_64 structs */
+	char		segname[16];	/* segment name */
+	uint64_t	vmaddr;		/* memory address of this segment */
+	uint64_t	vmsize;		/* memory size of this segment */
+	uint64_t	fileoff;	/* file offset of this segment */
+	uint64_t	filesize;	/* amount to map from the file */
+	vm_prot_t	maxprot;	/* maximum VM protection */
+	vm_prot_t	initprot;	/* initial VM protection */
+	uint32_t	nsects;		/* number of sections in segment */
+	uint32_t	flags;		/* flags */
+};
+
+/* Constants for the flags field of the segment_command */
+#define	SG_HIGHVM	0x1	/* the file contents for this segment is for
+				   the high part of the VM space, the low part
+				   is zero filled (for stacks in core files) */
+#define	SG_FVMLIB	0x2	/* this segment is the VM that is allocated by
+				   a fixed VM library, for overlap checking in
+				   the link editor */
+#define	SG_NORELOC	0x4	/* this segment has nothing that was relocated
+				   in it and nothing relocated to it, that is
+				   it maybe safely replaced without relocation*/
+#define SG_PROTECTED_VERSION_1	0x8 /* This segment is protected.  If the
+				       segment starts at file offset 0, the
+				       first page of the segment is not
+				       protected.  All other pages of the
+				       segment are protected. */
+
+/*
+ * A segment is made up of zero or more sections.  Non-MH_OBJECT files have
+ * all of their segments with the proper sections in each, and padded to the
+ * specified segment alignment when produced by the link editor.  The first
+ * segment of a MH_EXECUTE and MH_FVMLIB format file contains the mach_header
+ * and load commands of the object file before its first section.  The zero
+ * fill sections are always last in their segment (in all formats).  This
+ * allows the zeroed segment padding to be mapped into memory where zero fill
+ * sections might be. The gigabyte zero fill sections, those with the section
+ * type S_GB_ZEROFILL, can only be in a segment with sections of this type.
+ * These segments are then placed after all other segments.
+ *
+ * The MH_OBJECT format has all of its sections in one segment for
+ * compactness.  There is no padding to a specified segment boundary and the
+ * mach_header and load commands are not part of the segment.
+ *
+ * Sections with the same section name, sectname, going into the same segment,
+ * segname, are combined by the link editor.  The resulting section is aligned
+ * to the maximum alignment of the combined sections and is the new section's
+ * alignment.  The combined sections are aligned to their original alignment in
+ * the combined section.  Any padded bytes to get the specified alignment are
+ * zeroed.
+ *
+ * The format of the relocation entries referenced by the reloff and nreloc
+ * fields of the section structure for mach object files is described in the
+ * header file <reloc.h>.
+ */
+struct section { /* for 32-bit architectures */
+	char		sectname[16];	/* name of this section */
+	char		segname[16];	/* segment this section goes in */
+	uint32_t	addr;		/* memory address of this section */
+	uint32_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) */
+};
+
+struct section_64 { /* for 64-bit architectures */
+	char		sectname[16];	/* name of this section */
+	char		segname[16];	/* 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 */
+};
+
+/*
+ * The flags field of a section structure is separated into two parts a section
+ * type and section attributes.  The section types are mutually exclusive (it
+ * can only have one type) but the section attributes are not (it may have more
+ * than one attribute).
+ */
+#define SECTION_TYPE		 0x000000ff	/* 256 section types */
+#define SECTION_ATTRIBUTES	 0xffffff00	/*  24 section attributes */
+
+/* Constants for the type of a section */
+#define	S_REGULAR		0x0	/* regular section */
+#define	S_ZEROFILL		0x1	/* zero fill on demand section */
+#define	S_CSTRING_LITERALS	0x2	/* section with only literal C strings*/
+#define	S_4BYTE_LITERALS	0x3	/* section with only 4 byte literals */
+#define	S_8BYTE_LITERALS	0x4	/* section with only 8 byte literals */
+#define	S_LITERAL_POINTERS	0x5	/* section with only pointers to */
+					/*  literals */
+/*
+ * For the two types of symbol pointers sections and the symbol stubs section
+ * they have indirect symbol table entries.  For each of the entries in the
+ * section the indirect symbol table entries, in corresponding order in the
+ * indirect symbol table, start at the index stored in the reserved1 field
+ * of the section structure.  Since the indirect symbol table entries
+ * correspond to the entries in the section the number of indirect symbol table
+ * entries is inferred from the size of the section divided by the size of the
+ * entries in the section.  For symbol pointers sections the size of the entries
+ * in the section is 4 bytes and for symbol stubs sections the byte size of the
+ * stubs is stored in the reserved2 field of the section structure.
+ */
+#define	S_NON_LAZY_SYMBOL_POINTERS	0x6	/* section with only non-lazy
+						   symbol pointers */
+#define	S_LAZY_SYMBOL_POINTERS		0x7	/* section with only lazy symbol
+						   pointers */
+#define	S_SYMBOL_STUBS			0x8	/* section with only symbol
+						   stubs, byte size of stub in
+						   the reserved2 field */
+#define	S_MOD_INIT_FUNC_POINTERS	0x9	/* section with only function
+						   pointers for initialization*/
+#define	S_MOD_TERM_FUNC_POINTERS	0xa	/* section with only function
+						   pointers for termination */
+#define	S_COALESCED			0xb	/* section contains symbols that
+						   are to be coalesced */
+#define	S_GB_ZEROFILL			0xc	/* zero fill on demand section
+						   (that can be larger than 4
+						   gigabytes) */
+#define	S_INTERPOSING			0xd	/* section with only pairs of
+						   function pointers for
+						   interposing */
+#define	S_16BYTE_LITERALS		0xe	/* section with only 16 byte
+						   literals */
+#define	S_DTRACE_DOF			0xf	/* section contains 
+						   DTrace Object Format */
+#define	S_LAZY_DYLIB_SYMBOL_POINTERS	0x10	/* section with only lazy
+						   symbol pointers to lazy
+						   loaded dylibs */
+/*
+ * Section types to support thread local variables
+ */
+#define S_THREAD_LOCAL_REGULAR                   0x11  /* template of initial 
+							  values for TLVs */
+#define S_THREAD_LOCAL_ZEROFILL                  0x12  /* template of initial 
+							  values for TLVs */
+#define S_THREAD_LOCAL_VARIABLES                 0x13  /* TLV descriptors */
+#define S_THREAD_LOCAL_VARIABLE_POINTERS         0x14  /* pointers to TLV 
+                                                          descriptors */
+#define S_THREAD_LOCAL_INIT_FUNCTION_POINTERS    0x15  /* functions to call
+							  to initialize TLV
+							  values */
+
+/*
+ * Constants for the section attributes part of the flags field of a section
+ * structure.
+ */
+#define SECTION_ATTRIBUTES_USR	 0xff000000	/* User setable attributes */
+#define S_ATTR_PURE_INSTRUCTIONS 0x80000000	/* section contains only true
+						   machine instructions */
+#define S_ATTR_NO_TOC 		 0x40000000	/* section contains coalesced
+						   symbols that are not to be
+						   in a ranlib table of
+						   contents */
+#define S_ATTR_STRIP_STATIC_SYMS 0x20000000	/* ok to strip static symbols
+						   in this section in files
+						   with the MH_DYLDLINK flag */
+#define S_ATTR_NO_DEAD_STRIP	 0x10000000	/* no dead stripping */
+#define S_ATTR_LIVE_SUPPORT	 0x08000000	/* blocks are live if they
+						   reference live blocks */
+#define S_ATTR_SELF_MODIFYING_CODE 0x04000000	/* Used with i386 code stubs
+						   written on by dyld */
+/*
+ * If a segment contains any sections marked with S_ATTR_DEBUG then all
+ * sections in that segment must have this attribute.  No section other than
+ * a section marked with this attribute may reference the contents of this
+ * section.  A section with this attribute may contain no symbols and must have
+ * a section type S_REGULAR.  The static linker will not copy section contents
+ * from sections with this attribute into its output file.  These sections
+ * generally contain DWARF debugging info.
+ */ 
+#define	S_ATTR_DEBUG		 0x02000000	/* a debug section */
+#define SECTION_ATTRIBUTES_SYS	 0x00ffff00	/* system setable attributes */
+#define S_ATTR_SOME_INSTRUCTIONS 0x00000400	/* section contains some
+						   machine instructions */
+#define S_ATTR_EXT_RELOC	 0x00000200	/* section has external
+						   relocation entries */
+#define S_ATTR_LOC_RELOC	 0x00000100	/* section has local
+						   relocation entries */
+
+
+/*
+ * The names of segments and sections in them are mostly meaningless to the
+ * link-editor.  But there are few things to support traditional UNIX
+ * executables that require the link-editor and assembler to use some names
+ * agreed upon by convention.
+ *
+ * The initial protection of the "__TEXT" segment has write protection turned
+ * off (not writeable).
+ *
+ * The link-editor will allocate common symbols at the end of the "__common"
+ * section in the "__DATA" segment.  It will create the section and segment
+ * if needed.
+ */
+
+/* The currently known segment names and the section names in those segments */
+
+#define	SEG_PAGEZERO	"__PAGEZERO"	/* the pagezero segment which has no */
+					/* protections and catches NULL */
+					/* references for MH_EXECUTE files */
+
+
+#define	SEG_TEXT	"__TEXT"	/* the tradition UNIX text segment */
+#define	SECT_TEXT	"__text"	/* the real text part of the text */
+					/* section no headers, and no padding */
+#define SECT_FVMLIB_INIT0 "__fvmlib_init0"	/* the fvmlib initialization */
+						/*  section */
+#define SECT_FVMLIB_INIT1 "__fvmlib_init1"	/* the section following the */
+					        /*  fvmlib initialization */
+						/*  section */
+
+#define	SEG_DATA	"__DATA"	/* the tradition UNIX data segment */
+#define	SECT_DATA	"__data"	/* the real initialized data section */
+					/* no padding, no bss overlap */
+#define	SECT_BSS	"__bss"		/* the real uninitialized data section*/
+					/* no padding */
+#define SECT_COMMON	"__common"	/* the section common symbols are */
+					/* allocated in by the link editor */
+
+#define	SEG_OBJC	"__OBJC"	/* objective-C runtime segment */
+#define SECT_OBJC_SYMBOLS "__symbol_table"	/* symbol table */
+#define SECT_OBJC_MODULES "__module_info"	/* module information */
+#define SECT_OBJC_STRINGS "__selector_strs"	/* string table */
+#define SECT_OBJC_REFS "__selector_refs"	/* string table */
+
+#define	SEG_ICON	 "__ICON"	/* the icon segment */
+#define	SECT_ICON_HEADER "__header"	/* the icon headers */
+#define	SECT_ICON_TIFF   "__tiff"	/* the icons in tiff format */
+
+#define	SEG_LINKEDIT	"__LINKEDIT"	/* the segment containing all structs */
+					/* created and maintained by the link */
+					/* editor.  Created with -seglinkedit */
+					/* option to ld(1) for MH_EXECUTE and */
+					/* FVMLIB file types only */
+
+#define SEG_UNIXSTACK	"__UNIXSTACK"	/* the unix stack segment */
+
+#define SEG_IMPORT	"__IMPORT"	/* the segment for the self (dyld) */
+					/* modifing code stubs that has read, */
+					/* write and execute permissions */
+
+/*
+ * Fixed virtual memory shared libraries are identified by two things.  The
+ * target pathname (the name of the library as found for execution), and the
+ * minor version number.  The address of where the headers are loaded is in
+ * header_addr. (THIS IS OBSOLETE and no longer supported).
+ */
+struct fvmlib {
+	union lc_str	name;		/* library's target pathname */
+	uint32_t	minor_version;	/* library's minor version number */
+	uint32_t	header_addr;	/* library's header address */
+};
+
+/*
+ * A fixed virtual shared library (filetype == MH_FVMLIB in the mach header)
+ * contains a fvmlib_command (cmd == LC_IDFVMLIB) to identify the library.
+ * An object that uses a fixed virtual shared library also contains a
+ * fvmlib_command (cmd == LC_LOADFVMLIB) for each library it uses.
+ * (THIS IS OBSOLETE and no longer supported).
+ */
+struct fvmlib_command {
+	uint32_t	cmd;		/* LC_IDFVMLIB or LC_LOADFVMLIB */
+	uint32_t	cmdsize;	/* includes pathname string */
+	struct fvmlib	fvmlib;		/* the library identification */
+};
+
+/*
+ * Dynamicly linked shared libraries are identified by two things.  The
+ * pathname (the name of the library as found for execution), and the
+ * compatibility version number.  The pathname must match and the compatibility
+ * number in the user of the library must be greater than or equal to the
+ * library being used.  The time stamp is used to record the time a library was
+ * built and copied into user so it can be use to determined if the library used
+ * at runtime is exactly the same as used to built the program.
+ */
+struct dylib {
+    union lc_str  name;			/* library's path name */
+    uint32_t timestamp;			/* library's build time stamp */
+    uint32_t current_version;		/* library's current version number */
+    uint32_t compatibility_version;	/* library's compatibility vers number*/
+};
+
+/*
+ * A dynamically linked shared library (filetype == MH_DYLIB in the mach header)
+ * contains a dylib_command (cmd == LC_ID_DYLIB) to identify the library.
+ * An object that uses a dynamically linked shared library also contains a
+ * dylib_command (cmd == LC_LOAD_DYLIB, LC_LOAD_WEAK_DYLIB, or
+ * LC_REEXPORT_DYLIB) for each library it uses.
+ */
+struct dylib_command {
+	uint32_t	cmd;		/* LC_ID_DYLIB, LC_LOAD_{,WEAK_}DYLIB,
+					   LC_REEXPORT_DYLIB */
+	uint32_t	cmdsize;	/* includes pathname string */
+	struct dylib	dylib;		/* the library identification */
+};
+
+/*
+ * A dynamically linked shared library may be a subframework of an umbrella
+ * framework.  If so it will be linked with "-umbrella umbrella_name" where
+ * Where "umbrella_name" is the name of the umbrella framework. A subframework
+ * can only be linked against by its umbrella framework or other subframeworks
+ * that are part of the same umbrella framework.  Otherwise the static link
+ * editor produces an error and states to link against the umbrella framework.
+ * The name of the umbrella framework for subframeworks is recorded in the
+ * following structure.
+ */
+struct sub_framework_command {
+	uint32_t	cmd;		/* LC_SUB_FRAMEWORK */
+	uint32_t	cmdsize;	/* includes umbrella string */
+	union lc_str 	umbrella;	/* the umbrella framework name */
+};
+
+/*
+ * For dynamically linked shared libraries that are subframework of an umbrella
+ * framework they can allow clients other than the umbrella framework or other
+ * subframeworks in the same umbrella framework.  To do this the subframework
+ * is built with "-allowable_client client_name" and an LC_SUB_CLIENT load
+ * command is created for each -allowable_client flag.  The client_name is
+ * usually a framework name.  It can also be a name used for bundles clients
+ * where the bundle is built with "-client_name client_name".
+ */
+struct sub_client_command {
+	uint32_t	cmd;		/* LC_SUB_CLIENT */
+	uint32_t	cmdsize;	/* includes client string */
+	union lc_str 	client;		/* the client name */
+};
+
+/*
+ * A dynamically linked shared library may be a sub_umbrella of an umbrella
+ * framework.  If so it will be linked with "-sub_umbrella umbrella_name" where
+ * Where "umbrella_name" is the name of the sub_umbrella framework.  When
+ * staticly linking when -twolevel_namespace is in effect a twolevel namespace 
+ * umbrella framework will only cause its subframeworks and those frameworks
+ * listed as sub_umbrella frameworks to be implicited linked in.  Any other
+ * dependent dynamic libraries will not be linked it when -twolevel_namespace
+ * is in effect.  The primary library recorded by the static linker when
+ * resolving a symbol in these libraries will be the umbrella framework.
+ * Zero or more sub_umbrella frameworks may be use by an umbrella framework.
+ * The name of a sub_umbrella framework is recorded in the following structure.
+ */
+struct sub_umbrella_command {
+	uint32_t	cmd;		/* LC_SUB_UMBRELLA */
+	uint32_t	cmdsize;	/* includes sub_umbrella string */
+	union lc_str 	sub_umbrella;	/* the sub_umbrella framework name */
+};
+
+/*
+ * A dynamically linked shared library may be a sub_library of another shared
+ * library.  If so it will be linked with "-sub_library library_name" where
+ * Where "library_name" is the name of the sub_library shared library.  When
+ * staticly linking when -twolevel_namespace is in effect a twolevel namespace 
+ * shared library will only cause its subframeworks and those frameworks
+ * listed as sub_umbrella frameworks and libraries listed as sub_libraries to
+ * be implicited linked in.  Any other dependent dynamic libraries will not be
+ * linked it when -twolevel_namespace is in effect.  The primary library
+ * recorded by the static linker when resolving a symbol in these libraries
+ * will be the umbrella framework (or dynamic library). Zero or more sub_library
+ * shared libraries may be use by an umbrella framework or (or dynamic library).
+ * The name of a sub_library framework is recorded in the following structure.
+ * For example /usr/lib/libobjc_profile.A.dylib would be recorded as "libobjc".
+ */
+struct sub_library_command {
+	uint32_t	cmd;		/* LC_SUB_LIBRARY */
+	uint32_t	cmdsize;	/* includes sub_library string */
+	union lc_str 	sub_library;	/* the sub_library name */
+};
+
+/*
+ * A program (filetype == MH_EXECUTE) that is
+ * prebound to its dynamic libraries has one of these for each library that
+ * the static linker used in prebinding.  It contains a bit vector for the
+ * modules in the library.  The bits indicate which modules are bound (1) and
+ * which are not (0) from the library.  The bit for module 0 is the low bit
+ * of the first byte.  So the bit for the Nth module is:
+ * (linked_modules[N/8] >> N%8) & 1
+ */
+struct prebound_dylib_command {
+	uint32_t	cmd;		/* LC_PREBOUND_DYLIB */
+	uint32_t	cmdsize;	/* includes strings */
+	union lc_str	name;		/* library's path name */
+	uint32_t	nmodules;	/* number of modules in library */
+	union lc_str	linked_modules;	/* bit vector of linked modules */
+};
+
+/*
+ * A program that uses a dynamic linker contains a dylinker_command to identify
+ * the name of the dynamic linker (LC_LOAD_DYLINKER).  And a dynamic linker
+ * contains a dylinker_command to identify the dynamic linker (LC_ID_DYLINKER).
+ * A file can have at most one of these.
+ * This struct is also used for the LC_DYLD_ENVIRONMENT load command and
+ * contains string for dyld to treat like environment variable.
+ */
+struct dylinker_command {
+	uint32_t	cmd;		/* LC_ID_DYLINKER, LC_LOAD_DYLINKER or
+					   LC_DYLD_ENVIRONMENT */
+	uint32_t	cmdsize;	/* includes pathname string */
+	union lc_str    name;		/* dynamic linker's path name */
+};
+
+/*
+ * Thread commands contain machine-specific data structures suitable for
+ * use in the thread state primitives.  The machine specific data structures
+ * follow the struct thread_command as follows.
+ * Each flavor of machine specific data structure is preceded by an unsigned
+ * long constant for the flavor of that data structure, an uint32_t
+ * that is the count of longs of the size of the state data structure and then
+ * the state data structure follows.  This triple may be repeated for many
+ * flavors.  The constants for the flavors, counts and state data structure
+ * definitions are expected to be in the header file <machine/thread_status.h>.
+ * These machine specific data structures sizes must be multiples of
+ * 4 bytes  The cmdsize reflects the total size of the thread_command
+ * and all of the sizes of the constants for the flavors, counts and state
+ * data structures.
+ *
+ * For executable objects that are unix processes there will be one
+ * thread_command (cmd == LC_UNIXTHREAD) created for it by the link-editor.
+ * This is the same as a LC_THREAD, except that a stack is automatically
+ * created (based on the shell's limit for the stack size).  Command arguments
+ * and environment variables are copied onto that stack.
+ */
+struct thread_command {
+	uint32_t	cmd;		/* LC_THREAD or  LC_UNIXTHREAD */
+	uint32_t	cmdsize;	/* total size of this command */
+	/* uint32_t flavor		   flavor of thread state */
+	/* uint32_t count		   count of longs in thread state */
+	/* struct XXX_thread_state state   thread state for this flavor */
+	/* ... */
+};
+
+/*
+ * The routines command contains the address of the dynamic shared library 
+ * initialization routine and an index into the module table for the module
+ * that defines the routine.  Before any modules are used from the library the
+ * dynamic linker fully binds the module that defines the initialization routine
+ * and then calls it.  This gets called before any module initialization
+ * routines (used for C++ static constructors) in the library.
+ */
+struct routines_command { /* for 32-bit architectures */
+	uint32_t	cmd;		/* LC_ROUTINES */
+	uint32_t	cmdsize;	/* total size of this command */
+	uint32_t	init_address;	/* address of initialization routine */
+	uint32_t	init_module;	/* index into the module table that */
+				        /*  the init routine is defined in */
+	uint32_t	reserved1;
+	uint32_t	reserved2;
+	uint32_t	reserved3;
+	uint32_t	reserved4;
+	uint32_t	reserved5;
+	uint32_t	reserved6;
+};
+
+/*
+ * The 64-bit routines command.  Same use as above.
+ */
+struct routines_command_64 { /* for 64-bit architectures */
+	uint32_t	cmd;		/* LC_ROUTINES_64 */
+	uint32_t	cmdsize;	/* total size of this command */
+	uint64_t	init_address;	/* address of initialization routine */
+	uint64_t	init_module;	/* index into the module table that */
+					/*  the init routine is defined in */
+	uint64_t	reserved1;
+	uint64_t	reserved2;
+	uint64_t	reserved3;
+	uint64_t	reserved4;
+	uint64_t	reserved5;
+	uint64_t	reserved6;
+};
+
+/*
+ * The symtab_command contains the offsets and sizes of the link-edit 4.3BSD
+ * "stab" style symbol table information as described in the header files
+ * <nlist.h> and <stab.h>.
+ */
+struct symtab_command {
+	uint32_t	cmd;		/* LC_SYMTAB */
+	uint32_t	cmdsize;	/* sizeof(struct symtab_command) */
+	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 */
+};
+
+/*
+ * This is the second set of the symbolic information which is used to support
+ * the data structures for the dynamically link editor.
+ *
+ * The original set of symbolic information in the symtab_command which contains
+ * the symbol and string tables must also be present when this load command is
+ * present.  When this load command is present the symbol table is organized
+ * into three groups of symbols:
+ *	local symbols (static and debugging symbols) - grouped by module
+ *	defined external symbols - grouped by module (sorted by name if not lib)
+ *	undefined external symbols (sorted by name if MH_BINDATLOAD is not set,
+ *	     			    and in order the were seen by the static
+ *				    linker if MH_BINDATLOAD is set)
+ * In this load command there are offsets and counts to each of the three groups
+ * of symbols.
+ *
+ * This load command contains a the offsets and sizes of the following new
+ * symbolic information tables:
+ *	table of contents
+ *	module table
+ *	reference symbol table
+ *	indirect symbol table
+ * The first three tables above (the table of contents, module table and
+ * reference symbol table) are only present if the file is a dynamically linked
+ * shared library.  For executable and object modules, which are files
+ * containing only one module, the information that would be in these three
+ * tables is determined as follows:
+ * 	table of contents - the defined external symbols are sorted by name
+ *	module table - the file contains only one module so everything in the
+ *		       file is part of the module.
+ *	reference symbol table - is the defined and undefined external symbols
+ *
+ * For dynamically linked shared library files this load command also contains
+ * offsets and sizes to the pool of relocation entries for all sections
+ * separated into two groups:
+ *	external relocation entries
+ *	local relocation entries
+ * For executable and object modules the relocation entries continue to hang
+ * off the section structures.
+ */
+struct dysymtab_command {
+    uint32_t cmd;	/* LC_DYSYMTAB */
+    uint32_t cmdsize;	/* sizeof(struct dysymtab_command) */
+
+    /*
+     * The symbols indicated by symoff and nsyms of the LC_SYMTAB load command
+     * are grouped into the following three groups:
+     *    local symbols (further grouped by the module they are from)
+     *    defined external symbols (further grouped by the module they are from)
+     *    undefined symbols
+     *
+     * The local symbols are used only for debugging.  The dynamic binding
+     * process may have to use them to indicate to the debugger the local
+     * symbols for a module that is being bound.
+     *
+     * The last two groups are used by the dynamic binding process to do the
+     * binding (indirectly through the module table and the reference symbol
+     * table when this is a dynamically linked shared library file).
+     */
+    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 */
+
+    /*
+     * For the for the dynamic binding process to find which module a symbol
+     * is defined in the table of contents is used (analogous to the ranlib
+     * structure in an archive) which maps defined external symbols to modules
+     * they are defined in.  This exists only in a dynamically linked shared
+     * library file.  For executable and object modules the defined external
+     * symbols are sorted by name and is use as the table of contents.
+     */
+    uint32_t tocoff;	/* file offset to table of contents */
+    uint32_t ntoc;	/* number of entries in table of contents */
+
+    /*
+     * To support dynamic binding of "modules" (whole object files) the symbol
+     * table must reflect the modules that the file was created from.  This is
+     * done by having a module table that has indexes and counts into the merged
+     * tables for each module.  The module structure that these two entries
+     * refer to is described below.  This exists only in a dynamically linked
+     * shared library file.  For executable and object modules the file only
+     * contains one module so everything in the file belongs to the module.
+     */
+    uint32_t modtaboff;	/* file offset to module table */
+    uint32_t nmodtab;	/* number of module table entries */
+
+    /*
+     * To support dynamic module binding the module structure for each module
+     * indicates the external references (defined and undefined) each module
+     * makes.  For each module there is an offset and a count into the
+     * reference symbol table for the symbols that the module references.
+     * This exists only in a dynamically linked shared library file.  For
+     * executable and object modules the defined external symbols and the
+     * undefined external symbols indicates the external references.
+     */
+    uint32_t extrefsymoff;	/* offset to referenced symbol table */
+    uint32_t nextrefsyms;	/* number of referenced symbol table entries */
+
+    /*
+     * The sections that contain "symbol pointers" and "routine stubs" have
+     * indexes and (implied counts based on the size of the section and fixed
+     * size of the entry) into the "indirect symbol" table for each pointer
+     * and stub.  For every section of these two types the index into the
+     * indirect symbol table is stored in the section header in the field
+     * reserved1.  An indirect symbol table entry is simply a 32bit index into
+     * the symbol table to the symbol that the pointer or stub is referring to.
+     * The indirect symbol table is ordered to match the entries in the section.
+     */
+    uint32_t indirectsymoff; /* file offset to the indirect symbol table */
+    uint32_t nindirectsyms;  /* number of indirect symbol table entries */
+
+    /*
+     * To support relocating an individual module in a library file quickly the
+     * external relocation entries for each module in the library need to be
+     * accessed efficiently.  Since the relocation entries can't be accessed
+     * through the section headers for a library file they are separated into
+     * groups of local and external entries further grouped by module.  In this
+     * case the presents of this load command who's extreloff, nextrel,
+     * locreloff and nlocrel fields are non-zero indicates that the relocation
+     * entries of non-merged sections are not referenced through the section
+     * structures (and the reloff and nreloc fields in the section headers are
+     * set to zero).
+     *
+     * Since the relocation entries are not accessed through the section headers
+     * this requires the r_address field to be something other than a section
+     * offset to identify the item to be relocated.  In this case r_address is
+     * set to the offset from the vmaddr of the first LC_SEGMENT command.
+     * For MH_SPLIT_SEGS images r_address is set to the the offset from the
+     * vmaddr of the first read-write LC_SEGMENT command.
+     *
+     * The relocation entries are grouped by module and the module table
+     * entries have indexes and counts into them for the group of external
+     * relocation entries for that the module.
+     *
+     * For sections that are merged across modules there must not be any
+     * remaining external relocation entries for them (for merged sections
+     * remaining relocation entries must be local).
+     */
+    uint32_t extreloff;	/* offset to external relocation entries */
+    uint32_t nextrel;	/* number of external relocation entries */
+
+    /*
+     * All the local relocation entries are grouped together (they are not
+     * grouped by their module since they are only used if the object is moved
+     * from it staticly link edited address).
+     */
+    uint32_t locreloff;	/* offset to local relocation entries */
+    uint32_t nlocrel;	/* number of local relocation entries */
+
+};	
+
+/*
+ * An indirect symbol table entry is simply a 32bit index into the symbol table 
+ * to the symbol that the pointer or stub is refering to.  Unless it is for a
+ * non-lazy symbol pointer section for a defined symbol which strip(1) as 
+ * removed.  In which case it has the value INDIRECT_SYMBOL_LOCAL.  If the
+ * symbol was also absolute INDIRECT_SYMBOL_ABS is or'ed with that.
+ */
+#define INDIRECT_SYMBOL_LOCAL	0x80000000
+#define INDIRECT_SYMBOL_ABS	0x40000000
+
+
+/* a table of contents entry */
+struct dylib_table_of_contents {
+    uint32_t symbol_index;	/* the defined external symbol
+				   (index into the symbol table) */
+    uint32_t module_index;	/* index into the module table this symbol
+				   is defined in */
+};	
+
+/* a module table entry */
+struct dylib_module {
+    uint32_t module_name;	/* the module name (index into string table) */
+
+    uint32_t iextdefsym;	/* index into externally defined symbols */
+    uint32_t nextdefsym;	/* number of externally defined symbols */
+    uint32_t irefsym;		/* index into reference symbol table */
+    uint32_t nrefsym;		/* number of reference symbol table entries */
+    uint32_t ilocalsym;		/* index into symbols for local symbols */
+    uint32_t nlocalsym;		/* number of local symbols */
+
+    uint32_t iextrel;		/* index into external relocation entries */
+    uint32_t nextrel;		/* number of external relocation entries */
+
+    uint32_t iinit_iterm;	/* low 16 bits are the index into the init
+				   section, high 16 bits are the index into
+			           the term section */
+    uint32_t ninit_nterm;	/* low 16 bits are the number of init section
+				   entries, high 16 bits are the number of
+				   term section entries */
+
+    uint32_t			/* for this module address of the start of */
+	objc_module_info_addr;  /*  the (__OBJC,__module_info) section */
+    uint32_t			/* for this module size of */
+	objc_module_info_size;	/*  the (__OBJC,__module_info) section */
+};	
+
+/* a 64-bit module table entry */
+struct dylib_module_64 {
+    uint32_t module_name;	/* the module name (index into string table) */
+
+    uint32_t iextdefsym;	/* index into externally defined symbols */
+    uint32_t nextdefsym;	/* number of externally defined symbols */
+    uint32_t irefsym;		/* index into reference symbol table */
+    uint32_t nrefsym;		/* number of reference symbol table entries */
+    uint32_t ilocalsym;		/* index into symbols for local symbols */
+    uint32_t nlocalsym;		/* number of local symbols */
+
+    uint32_t iextrel;		/* index into external relocation entries */
+    uint32_t nextrel;		/* number of external relocation entries */
+
+    uint32_t iinit_iterm;	/* low 16 bits are the index into the init
+				   section, high 16 bits are the index into
+				   the term section */
+    uint32_t ninit_nterm;      /* low 16 bits are the number of init section
+				  entries, high 16 bits are the number of
+				  term section entries */
+
+    uint32_t			/* for this module size of */
+        objc_module_info_size;	/*  the (__OBJC,__module_info) section */
+    uint64_t			/* for this module address of the start of */
+        objc_module_info_addr;	/*  the (__OBJC,__module_info) section */
+};
+
+/* 
+ * The entries in the reference symbol table are used when loading the module
+ * (both by the static and dynamic link editors) and if the module is unloaded
+ * or replaced.  Therefore all external symbols (defined and undefined) are
+ * listed in the module's reference table.  The flags describe the type of
+ * reference that is being made.  The constants for the flags are defined in
+ * <mach-o/nlist.h> as they are also used for symbol table entries.
+ */
+struct dylib_reference {
+    uint32_t isym:24,		/* index into the symbol table */
+    		  flags:8;	/* flags to indicate the type of reference */
+};
+
+/*
+ * The twolevel_hints_command contains the offset and number of hints in the
+ * two-level namespace lookup hints table.
+ */
+struct twolevel_hints_command {
+    uint32_t cmd;	/* LC_TWOLEVEL_HINTS */
+    uint32_t cmdsize;	/* sizeof(struct twolevel_hints_command) */
+    uint32_t offset;	/* offset to the hint table */
+    uint32_t nhints;	/* number of hints in the hint table */
+};
+
+/*
+ * The entries in the two-level namespace lookup hints table are twolevel_hint
+ * structs.  These provide hints to the dynamic link editor where to start
+ * looking for an undefined symbol in a two-level namespace image.  The
+ * isub_image field is an index into the sub-images (sub-frameworks and
+ * sub-umbrellas list) that made up the two-level image that the undefined
+ * symbol was found in when it was built by the static link editor.  If
+ * isub-image is 0 the the symbol is expected to be defined in library and not
+ * in the sub-images.  If isub-image is non-zero it is an index into the array
+ * of sub-images for the umbrella with the first index in the sub-images being
+ * 1. The array of sub-images is the ordered list of sub-images of the umbrella
+ * that would be searched for a symbol that has the umbrella recorded as its
+ * primary library.  The table of contents index is an index into the
+ * library's table of contents.  This is used as the starting point of the
+ * binary search or a directed linear search.
+ */
+struct twolevel_hint {
+    uint32_t 
+	isub_image:8,	/* index into the sub images */
+	itoc:24;	/* index into the table of contents */
+};
+
+/*
+ * The prebind_cksum_command contains the value of the original check sum for
+ * prebound files or zero.  When a prebound file is first created or modified
+ * for other than updating its prebinding information the value of the check sum
+ * is set to zero.  When the file has it prebinding re-done and if the value of
+ * the check sum is zero the original check sum is calculated and stored in
+ * cksum field of this load command in the output file.  If when the prebinding
+ * is re-done and the cksum field is non-zero it is left unchanged from the
+ * input file.
+ */
+struct prebind_cksum_command {
+    uint32_t cmd;	/* LC_PREBIND_CKSUM */
+    uint32_t cmdsize;	/* sizeof(struct prebind_cksum_command) */
+    uint32_t cksum;	/* the check sum or zero */
+};
+
+/*
+ * The uuid load command contains a single 128-bit unique random number that
+ * identifies an object produced by the static link editor.
+ */
+struct uuid_command {
+    uint32_t	cmd;		/* LC_UUID */
+    uint32_t	cmdsize;	/* sizeof(struct uuid_command) */
+    uint8_t	uuid[16];	/* the 128-bit uuid */
+};
+
+/*
+ * The rpath_command contains a path which at runtime should be added to
+ * the current run path used to find @rpath prefixed dylibs.
+ */
+struct rpath_command {
+    uint32_t	 cmd;		/* LC_RPATH */
+    uint32_t	 cmdsize;	/* includes string */
+    union lc_str path;		/* path to add to run path */
+};
+
+/*
+ * The linkedit_data_command contains the offsets and sizes of a blob
+ * of data in the __LINKEDIT segment.  
+ */
+struct linkedit_data_command {
+    uint32_t	cmd;		/* LC_CODE_SIGNATURE, LC_SEGMENT_SPLIT_INFO,
+                                   or LC_FUNCTION_STARTS */
+    uint32_t	cmdsize;	/* sizeof(struct linkedit_data_command) */
+    uint32_t	dataoff;	/* file offset of data in __LINKEDIT segment */
+    uint32_t	datasize;	/* file size of data in __LINKEDIT segment  */
+};
+
+/*
+ * The encryption_info_command contains the file offset and size of an
+ * of an encrypted segment.
+ */
+struct encryption_info_command {
+   uint32_t	cmd;		/* LC_ENCRYPTION_INFO */
+   uint32_t	cmdsize;	/* sizeof(struct encryption_info_command) */
+   uint32_t	cryptoff;	/* file offset of encrypted range */
+   uint32_t	cryptsize;	/* file size of encrypted range */
+   uint32_t	cryptid;	/* which enryption system,
+				   0 means not-encrypted yet */
+};
+
+/*
+ * The version_min_command contains the min OS version on which this 
+ * binary was built to run.
+ */
+struct version_min_command {
+    uint32_t	cmd;		/* LC_VERSION_MIN_MACOSX or
+				   LC_VERSION_MIN_IPHONEOS  */
+    uint32_t	cmdsize;	/* sizeof(struct min_version_command) */
+    uint32_t	version;	/* X.Y.Z is encoded in nibbles xxxx.yy.zz */
+    uint32_t	reserved;	/* zero */
+};
+
+/*
+ * The dyld_info_command contains the file offsets and sizes of 
+ * the new compressed form of the information dyld needs to 
+ * load the image.  This information is used by dyld on Mac OS X
+ * 10.6 and later.  All information pointed to by this command
+ * is encoded using byte streams, so no endian swapping is needed
+ * to interpret it. 
+ */
+struct dyld_info_command {
+   uint32_t   cmd;		/* LC_DYLD_INFO or LC_DYLD_INFO_ONLY */
+   uint32_t   cmdsize;		/* sizeof(struct dyld_info_command) */
+
+    /*
+     * Dyld rebases an image whenever dyld loads it at an address different
+     * from its preferred address.  The rebase information is a stream
+     * of byte sized opcodes whose symbolic names start with REBASE_OPCODE_.
+     * Conceptually the rebase information is a table of tuples:
+     *    <seg-index, seg-offset, type>
+     * The opcodes are a compressed way to encode the table by only
+     * encoding when a column changes.  In addition simple patterns
+     * like "every n'th offset for m times" can be encoded in a few
+     * bytes.
+     */
+    uint32_t   rebase_off;	/* file offset to rebase info  */
+    uint32_t   rebase_size;	/* size of rebase info   */
+    
+    /*
+     * Dyld binds an image during the loading process, if the image
+     * requires any pointers to be initialized to symbols in other images.  
+     * The bind information is a stream of byte sized 
+     * opcodes whose symbolic names start with BIND_OPCODE_.
+     * Conceptually the bind information is a table of tuples:
+     *    <seg-index, seg-offset, type, symbol-library-ordinal, symbol-name, addend>
+     * The opcodes are a compressed way to encode the table by only
+     * encoding when a column changes.  In addition simple patterns
+     * like for runs of pointers initialzed to the same value can be 
+     * encoded in a few bytes.
+     */
+    uint32_t   bind_off;	/* file offset to binding info   */
+    uint32_t   bind_size;	/* size of binding info  */
+        
+    /*
+     * Some C++ programs require dyld to unique symbols so that all
+     * images in the process use the same copy of some code/data.
+     * This step is done after binding. The content of the weak_bind
+     * info is an opcode stream like the bind_info.  But it is sorted
+     * alphabetically by symbol name.  This enable dyld to walk 
+     * all images with weak binding information in order and look
+     * for collisions.  If there are no collisions, dyld does
+     * no updating.  That means that some fixups are also encoded
+     * in the bind_info.  For instance, all calls to "operator new"
+     * are first bound to libstdc++.dylib using the information
+     * in bind_info.  Then if some image overrides operator new
+     * that is detected when the weak_bind information is processed
+     * and the call to operator new is then rebound.
+     */
+    uint32_t   weak_bind_off;	/* file offset to weak binding info   */
+    uint32_t   weak_bind_size;  /* size of weak binding info  */
+    
+    /*
+     * Some uses of external symbols do not need to be bound immediately.
+     * Instead they can be lazily bound on first use.  The lazy_bind
+     * are contains a stream of BIND opcodes to bind all lazy symbols.
+     * Normal use is that dyld ignores the lazy_bind section when
+     * loading an image.  Instead the static linker arranged for the
+     * lazy pointer to initially point to a helper function which 
+     * pushes the offset into the lazy_bind area for the symbol
+     * needing to be bound, then jumps to dyld which simply adds
+     * the offset to lazy_bind_off to get the information on what 
+     * to bind.  
+     */
+    uint32_t   lazy_bind_off;	/* file offset to lazy binding info */
+    uint32_t   lazy_bind_size;  /* size of lazy binding infs */
+    
+    /*
+     * The symbols exported by a dylib are encoded in a trie.  This
+     * is a compact representation that factors out common prefixes.
+     * It also reduces LINKEDIT pages in RAM because it encodes all  
+     * information (name, address, flags) in one small, contiguous range.
+     * The export area is a stream of nodes.  The first node sequentially
+     * is the start node for the trie.  
+     *
+     * Nodes for a symbol start with a uleb128 that is the length of
+     * the exported symbol information for the string so far.
+     * If there is no exported symbol, the node starts with a zero byte. 
+     * If there is exported info, it follows the length.  First is
+     * a uleb128 containing flags.  Normally, it is followed by a
+     * uleb128 encoded offset which is location of the content named
+     * by the symbol from the mach_header for the image.  If the flags
+     * is EXPORT_SYMBOL_FLAGS_REEXPORT, then following the flags is
+     * a uleb128 encoded library ordinal, then a zero terminated
+     * UTF8 string.  If the string is zero length, then the symbol
+     * is re-export from the specified dylib with the same name.
+     *
+     * After the optional exported symbol information is a byte of
+     * how many edges (0-255) that this node has leaving it, 
+     * followed by each edge.
+     * Each edge is a zero terminated UTF8 of the addition chars
+     * in the symbol, followed by a uleb128 offset for the node that
+     * edge points to.
+     *  
+     */
+    uint32_t   export_off;	/* file offset to lazy binding info */
+    uint32_t   export_size;	/* size of lazy binding infs */
+};
+
+/*
+ * The following are used to encode rebasing information
+ */
+#define REBASE_TYPE_POINTER					1
+#define REBASE_TYPE_TEXT_ABSOLUTE32				2
+#define REBASE_TYPE_TEXT_PCREL32				3
+
+#define REBASE_OPCODE_MASK					0xF0
+#define REBASE_IMMEDIATE_MASK					0x0F
+#define REBASE_OPCODE_DONE					0x00
+#define REBASE_OPCODE_SET_TYPE_IMM				0x10
+#define REBASE_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB		0x20
+#define REBASE_OPCODE_ADD_ADDR_ULEB				0x30
+#define REBASE_OPCODE_ADD_ADDR_IMM_SCALED			0x40
+#define REBASE_OPCODE_DO_REBASE_IMM_TIMES			0x50
+#define REBASE_OPCODE_DO_REBASE_ULEB_TIMES			0x60
+#define REBASE_OPCODE_DO_REBASE_ADD_ADDR_ULEB			0x70
+#define REBASE_OPCODE_DO_REBASE_ULEB_TIMES_SKIPPING_ULEB	0x80
+
+
+/*
+ * The following are used to encode binding information
+ */
+#define BIND_TYPE_POINTER					1
+#define BIND_TYPE_TEXT_ABSOLUTE32				2
+#define BIND_TYPE_TEXT_PCREL32					3
+
+#define BIND_SPECIAL_DYLIB_SELF					 0
+#define BIND_SPECIAL_DYLIB_MAIN_EXECUTABLE			-1
+#define BIND_SPECIAL_DYLIB_FLAT_LOOKUP				-2
+
+#define BIND_SYMBOL_FLAGS_WEAK_IMPORT				0x1
+#define BIND_SYMBOL_FLAGS_NON_WEAK_DEFINITION			0x8
+
+#define BIND_OPCODE_MASK					0xF0
+#define BIND_IMMEDIATE_MASK					0x0F
+#define BIND_OPCODE_DONE					0x00
+#define BIND_OPCODE_SET_DYLIB_ORDINAL_IMM			0x10
+#define BIND_OPCODE_SET_DYLIB_ORDINAL_ULEB			0x20
+#define BIND_OPCODE_SET_DYLIB_SPECIAL_IMM			0x30
+#define BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM		0x40
+#define BIND_OPCODE_SET_TYPE_IMM				0x50
+#define BIND_OPCODE_SET_ADDEND_SLEB				0x60
+#define BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB			0x70
+#define BIND_OPCODE_ADD_ADDR_ULEB				0x80
+#define BIND_OPCODE_DO_BIND					0x90
+#define BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB			0xA0
+#define BIND_OPCODE_DO_BIND_ADD_ADDR_IMM_SCALED			0xB0
+#define BIND_OPCODE_DO_BIND_ULEB_TIMES_SKIPPING_ULEB		0xC0
+
+
+/*
+ * The following are used on the flags byte of a terminal node
+ * in the export information.
+ */
+#define EXPORT_SYMBOL_FLAGS_KIND_MASK				0x03
+#define EXPORT_SYMBOL_FLAGS_KIND_REGULAR			0x00
+#define EXPORT_SYMBOL_FLAGS_KIND_THREAD_LOCAL			0x01
+#define EXPORT_SYMBOL_FLAGS_WEAK_DEFINITION			0x04
+#define EXPORT_SYMBOL_FLAGS_REEXPORT				0x08
+#define EXPORT_SYMBOL_FLAGS_STUB_AND_RESOLVER			0x10
+
+/*
+ * The symseg_command contains the offset and size of the GNU style
+ * symbol table information as described in the header file <symseg.h>.
+ * The symbol roots of the symbol segments must also be aligned properly
+ * in the file.  So the requirement of keeping the offsets aligned to a
+ * multiple of a 4 bytes translates to the length field of the symbol
+ * roots also being a multiple of a long.  Also the padding must again be
+ * zeroed. (THIS IS OBSOLETE and no longer supported).
+ */
+struct symseg_command {
+	uint32_t	cmd;		/* LC_SYMSEG */
+	uint32_t	cmdsize;	/* sizeof(struct symseg_command) */
+	uint32_t	offset;		/* symbol segment offset */
+	uint32_t	size;		/* symbol segment size in bytes */
+};
+
+/*
+ * The ident_command contains a free format string table following the
+ * ident_command structure.  The strings are null terminated and the size of
+ * the command is padded out with zero bytes to a multiple of 4 bytes/
+ * (THIS IS OBSOLETE and no longer supported).
+ */
+struct ident_command {
+	uint32_t cmd;		/* LC_IDENT */
+	uint32_t cmdsize;	/* strings that follow this command */
+};
+
+/*
+ * The fvmfile_command contains a reference to a file to be loaded at the
+ * specified virtual address.  (Presently, this command is reserved for
+ * internal use.  The kernel ignores this command when loading a program into
+ * memory).
+ */
+struct fvmfile_command {
+	uint32_t cmd;			/* LC_FVMFILE */
+	uint32_t cmdsize;		/* includes pathname string */
+	union lc_str	name;		/* files pathname */
+	uint32_t	header_addr;	/* files virtual address */
+};
+
+/*
+ * Sections of type S_THREAD_LOCAL_VARIABLES contain an array 
+ * of tlv_descriptor structures.
+ */
+struct tlv_descriptor
+{
+	void*		(*thunk)(struct tlv_descriptor*);
+	unsigned long	key;
+	unsigned long	offset;
+};
+
+#endif /* _MACHO_LOADER_H_ */