The following macros check for certain operating systems that need special treatment for some programs, due to exceptional oddities in their header files or libraries. These macros are warts; they will be replaced by a more systematic approach, based on the functions they make available or the environments they provide.
function>AC_AIX/function> If on AIX, define _ALL_SOURCE. Allows the use of some bsd functions. Should be called before any macros that run the C compiler.
function>AC_ISC_POSIX/function> For interactive unix (isc), add -lcposix to output variable LIBS if necessary for posix facilities. Call this after AC_PROG_CC and before any other macros that use posix interfaces. interactive unix is no longer sold, and Sun says that they will drop support for it on 2006-07-23, so this macro is becoming obsolescent.
function>AC_MINIX/function> If on Minix, define _MINIX and _POSIX_SOURCE and define _POSIX_1_SOURCE to be 2. This allows the use of posix facilities. Should be called before any macros that run the C compiler.