compat(5) BSD File Formats Manual compat(5)
NAME
compat -- manipulate compatibility settings
SYNOPSIS
COMMAND_MODE=legacy|unix2003
#define _POSIX_C_SOURCE
#define _DARWIN_C_SOURCE
#define _NONSTD_SOURCE
defined(__LP64__)
#include <sys/cdefs.h>
defined(_DARWIN_FEATURE_UNIX_CONFORMANCE)
DESCRIPTION
Setting the environment variable COMMAND_MODE to the value legacy causes
utility programs to behave as closely to Mac OS X 10.3's utility programs
as possible. When in this mode all of 10.3's flags are accepted, and in
some cases extra flags are accepted, but no flags that were used in 10.3
will have been removed or changed in meaning. Any behavioral changes in
this mode are documented in the LEGACY sections of the individual utili-
ties.
Setting the environment variable COMMAND_MODE to the value unix03 causes
utility programs to obey the Version 3 of the Single UNIX Specification
(``SUSv3'') standards even if doing so would alter the behavior of flags
used in 10.3.
The value of COMMAND_MODE is case insensitive and if it is unset or set
to something other than legacy or unix03 it behaves as if it were set to
unix03.
32-BIT COMPILATION
Defining _NONSTD_SOURCE causes library and kernel calls to behave as
closely to Mac OS X 10.3's library and kernel calls as possible. Any
behavioral changes in this mode are documented in the LEGACY sections of
the individual function calls.
Defining _POSIX_C_SOURCE or _DARWIN_C_SOURCE causes library and kernel
calls to conform to the SUSv3 standards even if doing so would alter the
behavior of functions used in 10.3. Defining _POSIX_C_SOURCE also
removes functions, types, and other interfaces that are not part of SUSv3
from the normal C namespace, unless _DARWIN_C_SOURCE is also defined
(i.e., _DARWIN_C_SOURCE is _POSIX_C_SOURCE with non-POSIX extensions).
In any of these cases, the _DARWIN_FEATURE_UNIX_CONFORMANCE feature macro
will be defined to the SUS conformance level (it is undefined otherwise).
Starting in Mac OS X 10.5, if none of the macros _NONSTD_SOURCE,
_POSIX_C_SOURCE or _DARWIN_C_SOURCE are defined, and the environment
variable MACOSX_DEPLOYMENT_TARGET is either undefined or set to 10.5 or
greater (or equivalently, the gcc(1) option -mmacosx-version-min is
either not specified or set to 10.5 or greater), then UNIX conformance
will be on by default, and non-POSIX extensions will also be available
(this is the equivalent of defining _DARWIN_C_SOURCE). For version val-
ues less that 10.5, UNIX conformance will be off (the equivalent of
defining _NONSTD_SOURCE).
64-BIT COMPILATION
When compiling for 64-bit architectures, the __LP64__ macro will be
defined to 1, and UNIX conformance is always on (the
_DARWIN_FEATURE_UNIX_CONFORMANCE macro will also be defined to the SUS
conformance level). Defining _NONSTD_SOURCE will cause a compilation
error.
STANDARDS
With COMMAND_MODE set to unix2003 utility functions conform to Version 3
of the Single UNIX Specification (``SUSv3'').
With _POSIX_C_SOURCE, _DARWIN_C_SOURCE, or __LP64__, system and library
calls conform to Version 3 of the Single UNIX Specification (``SUSv3'').
BUGS
Different parts of a program can be compiled with different compatibility
settings. The resultant program will normally work as expected, for
example a regex created by the SUSv3 regcomp(3) can be passed to the
legacy regfree(3) with no unexpected results. Some cases are less clear
cut, for example what does the programmer intend when they use the SUSv3
regcomp(3) to compile a regex, but the legacy regexec(3) to execute it?
Any interpretation will surprise someone.
Darwin October 23, 2005 Darwin
Mac OS X 10.5 - Generated Sun Oct 28 21:43:47 EDT 2007