emacs/m4/timer_time.m4

# timer_time.m4 serial 4
dnl Copyright (C) 2011-2021 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.

# Check for timer_settime, and set LIB_TIMER_TIME.

AC_DEFUN([gl_TIMER_TIME],
[
  dnl Based on clock_time.m4. See details there.

  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])

  dnl Test whether the gnulib module 'threadlib' is in use.
  dnl Some packages like Emacs use --avoid=threadlib.
  dnl Write the symbol in such a way that it does not cause 'aclocal' to pick
  dnl the threadlib.m4 file that is installed in $PREFIX/share/aclocal/.
  m4_ifdef([gl_][PTHREADLIB], [AC_REQUIRE([gl_][PTHREADLIB])])

  LIB_TIMER_TIME=
  AC_SUBST([LIB_TIMER_TIME])
  gl_saved_libs=$LIBS
    AC_SEARCH_LIBS([timer_settime], [rt posix4],
                   [test "$ac_cv_search_timer_settime" = "none required" ||
                    LIB_TIMER_TIME=$ac_cv_search_timer_settime])
    m4_ifdef([gl_][PTHREADLIB],
      [dnl GLIBC uses threads to emulate posix timers when kernel support
       dnl is not available (like Linux < 2.6 or when used with kFreeBSD)
       dnl Now the pthread lib is linked automatically in the normal case,
       dnl but when linking statically, it needs to be explicitly specified.
       AC_EGREP_CPP([Thread],
         [#include <features.h>
          #ifdef __GNU_LIBRARY__
           #if ((__GLIBC__ == 2 && __GLIBC_MINOR__ >= 2) || (__GLIBC__ > 2)) \
               && !(__UCLIBC__ && __HAS_NO_THREADS__)
            Thread emulation available
           #endif
          #endif
         ],
         [LIB_TIMER_TIME="$LIB_TIMER_TIME $LIBPMULTITHREAD"])])
    AC_CHECK_FUNCS([timer_settime])
  LIBS=$gl_saved_libs
])