Expand description
A header contains minimal architecture information, the binary kind, the number of load commands, as well as an endianness hint
Structs
- Generic sized header
 - A 32-bit Mach-o header
 - A 64-bit Mach-o header
 
Constants
- 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.
 - When this bit is set, all stacks in the task will be given stack execution privilege. Only used in MH_EXECUTE filetypes.
 - The code was linked for use in an application extension.
 - the object file’s undefined references are bound by the dynamic linker when loaded.
 - the final linked image uses weak symbols
 - dynamically bound bundle file
 - the binary has been canonicalized via the unprebind operation
 - core file
 - 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.
 - companion file with only debug sections
 - the object file is input for the dynamic linker and can’t be staticly link edited again
 - dynamically bound shared library
 - shared library stub for static linking only, no section contents
 - dynamic link editor
 - demand paged executable file
 - the executable is forcing all images to use flat name space bindings
 - fixed VM shared library file
 - Contains a section of type S_THREAD_LOCAL_VARIABLES
 - the object file is the output of an incremental link against a base file and can’t be link edited again
 - x86_64 kexts
 - the shared library init routine is to be run lazily via catching memory faults to its writeable segments (obsolete)
 - Mach Header magic constant
 - Mach Header magic constant for 64-bit
 - do not have dyld notify the prebinding agent about this executable
 - this umbrella guarantees no multiple defintions of symbols in its sub-images so the two-level namespace hints can always be used.
 - the object file has no undefined references
 - 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.
 - 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
 - relocatable object file
 - When this bit is set, the OS will load the main executable at a random address. Only used in MH_EXECUTE filetypes.
 - the binary is not prebound but can have its prebinding redone. only used when MH_PREBOUND is not set.
 - the file has its dynamic undefined references prebound.
 - preloaded executable file
 - When this bit is set, the binary declares it is safe for use in processes with uid zero
 - When this bit is set, the binary declares it is safe for use in processes when issetugid() is true
 - the file has its read-only and read-write segments split
 - safe to divide up the sections into sub-sections via symbols for dead code stripping
 - the image is using two-level name space bindings
 - the final linked image contains external weak symbols