# usleep.m4 serial 8
dnl Copyright (C) 2009-2023 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.

dnl This macro intentionally does not check for select or nanosleep;
dnl both of those modules can require external libraries.
AC_DEFUN([gl_FUNC_USLEEP],
[
  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
  dnl usleep was required in POSIX 2001, but dropped as obsolete in
  dnl POSIX 2008; therefore, it is not always exposed in headers.
  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
  AC_CHECK_FUNCS_ONCE([usleep])
  AC_CHECK_TYPE([useconds_t], [],
    [AC_DEFINE([useconds_t], [unsigned int], [Define to an unsigned 32-bit
      type if <sys/types.h> lacks this type.])])
  if test $ac_cv_func_usleep = no; then
    HAVE_USLEEP=0
  else
    dnl POSIX allows implementations to reject arguments larger than
    dnl 999999, but GNU guarantees it will work.
    AC_CACHE_CHECK([whether usleep allows large arguments],
      [gl_cv_func_usleep_works],
      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
#include <unistd.h>
]], [[return !!usleep (1000000);]])],
        [gl_cv_func_usleep_works=yes], [gl_cv_func_usleep_works=no],
        [case "$host_os" in
                          # Guess yes on glibc systems.
           *-gnu* | gnu*) gl_cv_func_usleep_works="guessing yes" ;;
                          # Guess yes on musl systems.
           *-musl*)       gl_cv_func_usleep_works="guessing yes" ;;
                          # Guess yes on systems that emulate the Linux system calls.
           midipix*)      gl_cv_func_usleep_works="guessing yes" ;;
                          # Guess no on native Windows.
           mingw*)        gl_cv_func_usleep_works="guessing no" ;;
                          # If we don't know, obey --enable-cross-guesses.
           *)             gl_cv_func_usleep_works="$gl_cross_guess_normal" ;;
         esac
        ])])
    case "$gl_cv_func_usleep_works" in
      *yes) ;;
      *)
        REPLACE_USLEEP=1
        ;;
    esac
  fi
])