Mach-O的Header的flags
flags含义解释
MH_NOUNDEFS- The object file contained no undefined references when it was built.
MH_INCRLINK- The object file is the output of an incremental link against a base file and cannot be linked again.
MH_DYLDLINK- The file is input for the dynamic linker and cannot be statically linked again.
MH_TWOLEVEL- The image is using two-level namespace bindings.
MH_BINDATLOAD- The dynamic linker should bind the undefined references when the file is loaded.
MH_PREBOUND- The file’s undefined references are prebound.
MH_PREBINDABLE- This file is not prebound but can have its prebinding redone. Used only when MH_PREBEOUND is not set.
MH_NOFIXPREBINDING- The dynamic linker doesn’t notify the prebinding agent about this executable.
MH_ALLMODSBOUND- Indicates that this binary binds to all two-level namespace modules of its dependent libraries. Used only when MH_PREBINDABLE and MH_TWOLEVEL are set.
MH_CANONICAL- This file has been canonicalized by unprebinding—clearing prebinding information from the file. See the redo_prebinding man page for details.
MH_SPLIT_SEGS- The file has its read-only and read-write segments split.
MH_FORCE_FLAT- The executable is forcing all images to use flat namespace bindings.
MH_SUBSECTIONS_VIA_SYMBOLS- The sections of the object file can be divided into individual blocks. These blocks are dead-stripped if they are not used by other code. See Linking for details.
MH_NOMULTIDEFS- This umbrella guarantees there are no multiple definitions of symbols in its subimages. As a result, the two-level namespace hints can always be used.
flags定义
源码定义：
/* 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. */