ax_have_select

This macro determines whether the system supports the select I/O event interface. A neat usage example would be:

  AX_HAVE_SELECT(
    [AX_CONFIG_FEATURE_ENABLE(select)],
    [AX_CONFIG_FEATURE_DISABLE(select)])
  AX_CONFIG_FEATURE(
    [select], [This platform supports select(7)],
    [HAVE_SELECT], [This platform supports select(7).])

Some systems also have the variant pselect(). The availability of that function can be tested with the second macro. Generally speaking, it is safe to assume that AX_HAVE_SELECT would succeed if AX_HAVE_SELECT_PWAIT has, but not the other way round.

AC_DEFUN([AX_HAVE_SELECT], [dnl
  AC_MSG_CHECKING([for select(2)])
  AC_CACHE_VAL([ax_cv_have_select], [dnl
    AC_LINK_IFELSE([dnl
      AC_LANG_PROGRAM(
        [#include <sys/select.h>],
        [int rc; rc = select(0, (fd_set *)(0), (fd_set *)(0), (fd_set *)(0), (struct timeval *)(0));])],
      [ax_cv_have_select=yes],
      [ax_cv_have_select=no])])
  AS_IF([test "${ax_cv_have_select}" = "yes"],
    [AC_MSG_RESULT([yes])
$1],[AC_MSG_RESULT([no])
$2])
])dnl

AC_DEFUN([AX_HAVE_PSELECT], [dnl
  AC_MSG_CHECKING([for pselect(2)])
  AC_CACHE_VAL([ax_cv_have_pselect], [dnl
    AC_LINK_IFELSE([dnl
      AC_LANG_PROGRAM(
        [dnl
#include <sys/select.h>
#include <signal.h>],
        [dnl
int rc;
rc = select(0, (fd_set *)(0), (fd_set *)(0), (fd_set *)(0), (struct timeval *)(0));
rc = pselect(0, (fd_set *)(0), (fd_set *)(0), (fd_set *)(0), (struct timespec const *)(0), (sigset_t const *)(0));])],
      [ax_cv_have_pselect=yes],
      [ax_cv_have_pselect=no])])
  AS_IF([test "${ax_cv_have_pselect}" = "yes"],
    [AC_MSG_RESULT([yes])
$1],[AC_MSG_RESULT([no])
$2])
])dnl

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