emacs/m4/gettimeofday.m4

# serial 27

# Copyright (C) 2001-2003, 2005, 2007, 2009-2020 Free Software Foundation, Inc.
# This file is free software; the Free Software Foundation
# gives unlimited permission to copy and/or distribute it,
# with or without modifications, as long as this notice is preserved.

dnl From Jim Meyering.

AC_DEFUN([gl_FUNC_GETTIMEOFDAY],
[
  AC_REQUIRE([gl_HEADER_SYS_TIME_H_DEFAULTS])
  AC_REQUIRE([AC_C_RESTRICT])
  AC_REQUIRE([AC_CANONICAL_HOST])
  AC_REQUIRE([gl_HEADER_SYS_TIME_H])
  AC_CHECK_FUNCS_ONCE([gettimeofday])

  gl_gettimeofday_timezone=void
  if test $ac_cv_func_gettimeofday != yes; then
    HAVE_GETTIMEOFDAY=0
  else
    gl_FUNC_GETTIMEOFDAY_CLOBBER
    AC_CACHE_CHECK([for gettimeofday with POSIX signature],
      [gl_cv_func_gettimeofday_posix_signature],
      [AC_COMPILE_IFELSE(
         [AC_LANG_PROGRAM(
            [[#include <sys/time.h>
              struct timeval c;
              int gettimeofday (struct timeval *restrict, void *restrict);
            ]],
            [[/* glibc uses struct timezone * rather than the POSIX void *
                 if _GNU_SOURCE is defined.  However, since the only portable
                 use of gettimeofday uses NULL as the second parameter, and
                 since the glibc definition is actually more typesafe, it is
                 not worth wrapping this to get a compliant signature.  */
              int (*f) (struct timeval *restrict, void *restrict)
                = gettimeofday;
              int x = f (&c, 0);
              return !(x | c.tv_sec | c.tv_usec);
            ]])],
          [gl_cv_func_gettimeofday_posix_signature=yes],
          [AC_COMPILE_IFELSE(
            [AC_LANG_PROGRAM(
              [[#include <sys/time.h>
int gettimeofday (struct timeval *restrict, struct timezone *restrict);
              ]])],
            [gl_cv_func_gettimeofday_posix_signature=almost],
            [gl_cv_func_gettimeofday_posix_signature=no])])])
    if test $gl_cv_func_gettimeofday_posix_signature = almost; then
      gl_gettimeofday_timezone='struct timezone'
    elif test $gl_cv_func_gettimeofday_posix_signature != yes; then
      REPLACE_GETTIMEOFDAY=1
    fi
    dnl If we override 'struct timeval', we also have to override gettimeofday.
    if test $REPLACE_STRUCT_TIMEVAL = 1; then
      REPLACE_GETTIMEOFDAY=1
    fi
    dnl On mingw, the original gettimeofday has only a precision of 15.6
    dnl milliseconds. So override it.
    case "$host_os" in
      mingw*) REPLACE_GETTIMEOFDAY=1 ;;
    esac
  fi
  AC_DEFINE_UNQUOTED([GETTIMEOFDAY_TIMEZONE], [$gl_gettimeofday_timezone],
    [Define this to 'void' or 'struct timezone' to match the system's
     declaration of the second argument to gettimeofday.])
])


dnl See if gettimeofday clobbers the static buffer that localtime uses
dnl for its 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([gl_FUNC_GETTIMEOFDAY_CLOBBER],
[
 AC_REQUIRE([gl_HEADER_SYS_TIME_H])
 AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
 AC_REQUIRE([gl_LOCALTIME_BUFFER_DEFAULTS])

 AC_CACHE_CHECK([whether gettimeofday clobbers localtime buffer],
  [gl_cv_func_gettimeofday_clobber],
  [AC_RUN_IFELSE(
     [AC_LANG_PROGRAM(
        [[#include <string.h>
          #include <sys/time.h>
          #include <time.h>
          #include <stdlib.h>
        ]],
        [[
          time_t t = 0;
          struct tm *lt;
          struct tm saved_lt;
          struct timeval tv;
          lt = localtime (&t);
          saved_lt = *lt;
          gettimeofday (&tv, NULL);
          return memcmp (lt, &saved_lt, sizeof (struct tm)) != 0;
        ]])],
     [gl_cv_func_gettimeofday_clobber=no],
     [gl_cv_func_gettimeofday_clobber=yes],
     [# When cross-compiling:
      case "$host_os" in
                       # Guess all is fine on glibc systems.
        *-gnu* | gnu*) gl_cv_func_gettimeofday_clobber="guessing no" ;;
                       # Guess all is fine on musl systems.
        *-musl*)       gl_cv_func_gettimeofday_clobber="guessing no" ;;
                       # Guess no on native Windows.
        mingw*)        gl_cv_func_gettimeofday_clobber="guessing no" ;;
                       # If we don't know, obey --enable-cross-guesses.
        *)             gl_cv_func_gettimeofday_clobber="$gl_cross_guess_inverted" ;;
      esac
     ])])

 case "$gl_cv_func_gettimeofday_clobber" in
   *yes)
     REPLACE_GETTIMEOFDAY=1
     AC_DEFINE([GETTIMEOFDAY_CLOBBERS_LOCALTIME], [1],
       [Define if gettimeofday clobbers the localtime buffer.])
     gl_LOCALTIME_BUFFER_NEEDED
     ;;
 esac
])

# Prerequisites of lib/gettimeofday.c.
AC_DEFUN([gl_PREREQ_GETTIMEOFDAY], [:])