gettimeofday.m4

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#serial 2

dnl From Jim Meyering.
dnl
dnl See if gettimeofday clobbers the static buffer that localtime uses
dnl for it's return value.  The gettimeofday function from Mac OS X 10.0.4,
dnl i.e. Darwin 1.3.7 has this problem.
dnl
dnl If it does, then arrange to use gettimeofday and localtime only via
dnl the wrapper functions that work around the problem.

AC_DEFUN([AC_FUNC_GETTIMEOFDAY_CLOBBER],
[
 AC_REQUIRE([AC_HEADER_TIME])
 AC_CHECK_HEADERS(string.h stdlib.h)
 AC_CACHE_CHECK([whether gettimeofday clobbers localtime buffer],
  jm_cv_func_gettimeofday_clobber,
  [AC_TRY_RUN([
#include <stdio.h>
#if HAVE_STRING_H
# include <string.h>
#endif

#if TIME_WITH_SYS_TIME
# include <sys/time.h>
# include <time.h>
#else
# if HAVE_SYS_TIME_H
#  include <sys/time.h>
# else
#  include <time.h>
# endif
#endif

#if HAVE_STDLIB_H
# include <stdlib.h>
#endif

int
main ()
{
  time_t t = 0;
  struct tm *lt;
  struct tm saved_lt;
  struct timeval tv;
  lt = localtime (&t);
  saved_lt = *lt;
  gettimeofday (&tv, NULL);
  if (memcmp (lt, &saved_lt, sizeof (struct tm)) != 0)
    exit (1);

  exit (0);
}
	  ],
	 jm_cv_func_gettimeofday_clobber=no,
	 jm_cv_func_gettimeofday_clobber=yes,
	 dnl When crosscompiling, assume it is broken.
	 jm_cv_func_gettimeofday_clobber=yes)
  ])
  if test $jm_cv_func_gettimeofday_clobber = yes; then
    AC_LIBOBJ(gettimeofday)
    AC_DEFINE(localtime, rpl_localtime,
      [Define to rpl_localtime if the replacement function should be used.])
    AC_DEFINE(gettimeofday, rpl_gettimeofday,
      [Define to rpl_gettimeofday if the replacement function should be used.])
    AC_DEFINE(GETTIMEOFDAY_CLOBBERS_LOCALTIME_BUFFER, 1,
      [Define if gettimeofday clobbers localtime's static buffer.])
  fi
])