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 unix2003
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 unix2003 it behaves as if it were set
to unix2003.
COMPILATION
Defining _NONSTD_SOURCE for i386 causes library and kernel calls to
behave as closely to Mac OS X 10.3's library and kernel calls as possi-
ble. Any behavioral changes are documented in the LEGACY sections of the
man pages for the individual function calls. Defining this macro when
compiling for any other architecture will result in a compilation error.
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 when targeting i386 (the
equivalent of defining _NONSTD_SOURCE).
In order to provide both legacy and conformance versions of functions,
two versions of affected functions are provided. Legacy variants have
symbol names with no suffix in order to maintain ABI compatibility. Con-
formance versions have a $UNIX2003 suffix appended to their symbol name.
These $UNIX2003 suffixes are automatically appended by the compiler tool-
chain and should not be used directly.
Platforms that were released after these updates only have conformance
variants available and do not have a $UNIX2003 suffix.
i386
------------------------------+--------------------------------------------
user defines deployment | namespace conformance suffix
target |
------------------------------+--------------------------------------------
(none) < 10.5 | full 10.3 compatibility (none)
(none) >= 10.5 | full SUSv3 conformance $UNIX2003
_NONSTD_SOURCE (any) | full 10.3 compatibility (none)
_DARWIN_C_SOURCE < 10.4 | full 10.3 compatibility (none)
_DARWIN_C_SOURCE >= 10.4 | full SUSv3 conformance $UNIX2003
_POSIX_C_SOURCE < 10.4 | strict 10.3 compatibility (none)
_POSIX_C_SOURCE >= 10.4 | strict SUSv3 conformance $UNIX2003
------------------------------+--------------------------------------------
Newer Architectures
------------------------------+--------------------------------------------
user defines deployment | namespace conformance suffix
target |
------------------------------+--------------------------------------------
(none) (any) | full SUSv3 conformance (none)
_NONSTD_SOURCE (any) | (error)
_DARWIN_C_SOURCE (any) | full SUSv3 conformance (none)
_POSIX_C_SOURCE (any) | strict SUSv3 conformance (none)
------------------------------+--------------------------------------------
STANDARDS
With COMMAND_MODE set to anything other than legacy, utility functions
conform to Version 3 of the Single UNIX Specification (``SUSv3'').
With _POSIX_C_SOURCE or _DARWIN_C_SOURCE for i386, or when building for
any other architecture, 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 June 30, 2010 Darwin
Mac OS X 10.9 - Generated Wed Oct 16 18:19:27 CDT 2013