view m4/ceilf.m4 @ 16869:38e6d30d7e4d

poll/select: prevent busy-waiting 2012-05-21 Paolo Bonzini <bonzini@gnu.org> poll/select: prevent busy-waiting. SwitchToThread() only gives away the rest of the current time slice to another thread in the current process. So if the thread that feeds the file decscriptor we're polling is not in the current process, we get busy-waiting. * lib/poll.c: Use SleepEx(1, TRUE) instead of SwitchToThread(). Patch from Theodore Leblond. * lib/select.c: Split polling out of the loop that sets the output fd_sets. Check for zero result and loop if the wait timeout is infinite.
author Paolo Bonzini <bonzini@gnu.org>
date Mon, 21 May 2012 09:52:42 +0200
parents b187fc49964b
children e542fd46ad6f
line wrap: on
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# ceilf.m4 serial 14
dnl Copyright (C) 2007, 2009-2012 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.

AC_DEFUN([gl_FUNC_CEILF],
[
  m4_divert_text([DEFAULTS], [gl_ceilf_required=plain])
  AC_REQUIRE([gl_MATH_H_DEFAULTS])
  dnl Persuade glibc <math.h> to declare ceilf().
  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
  dnl Test whether ceilf() is declared.
  AC_CHECK_DECLS([ceilf], , , [[#include <math.h>]])
  if test "$ac_cv_have_decl_ceilf" = yes; then
    dnl Test whether ceilf() can be used without libm.
    gl_FUNC_CEILF_LIBS
    if test "$CEILF_LIBM" = "?"; then
      dnl Sun C 5.0 on Solaris declares ceilf() and has it in the system-wide
      dnl libm.so, but not in the libm.so that the compiler uses.
      REPLACE_CEILF=1
    fi
    m4_ifdef([gl_FUNC_CEILF_IEEE], [
      if test $gl_ceilf_required = ieee && test $REPLACE_CEILF = 0; then
        AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
        AC_CACHE_CHECK([whether ceilf works according to ISO C 99 with IEC 60559],
          [gl_cv_func_ceilf_ieee],
          [
            save_LIBS="$LIBS"
            LIBS="$LIBS $CEILF_LIBM"
            AC_RUN_IFELSE(
              [AC_LANG_SOURCE([[
#ifndef __NO_MATH_INLINES
# define __NO_MATH_INLINES 1 /* for glibc */
#endif
#include <math.h>
]gl_FLOAT_MINUS_ZERO_CODE[
]gl_FLOAT_SIGNBIT_CODE[
static float dummy (float f) { return 0; }
int main (int argc, char *argv[])
{
  float (*my_ceilf) (float) = argc ? ceilf : dummy;
  int result = 0;
  /* Test whether ceilf (-0.0f) is -0.0f.  */
  if (signbitf (minus_zerof) && !signbitf (my_ceilf (minus_zerof)))
    result |= 1;
  /* Test whether ceilf (-0.3f) is -0.0f.  */
  if (signbitf (-0.3f) && !signbitf (my_ceilf (-0.3f)))
    result |= 2;
  return result;
}
              ]])],
              [gl_cv_func_ceilf_ieee=yes],
              [gl_cv_func_ceilf_ieee=no],
              [case "$host_os" in
                         # Guess yes on glibc systems.
                 *-gnu*) gl_cv_func_ceilf_ieee="guessing yes" ;;
                         # If we don't know, assume the worst.
                 *)      gl_cv_func_ceilf_ieee="guessing no" ;;
               esac
              ])
            LIBS="$save_LIBS"
          ])
        case "$gl_cv_func_ceilf_ieee" in
          *yes) ;;
          *) REPLACE_CEILF=1 ;;
        esac
      fi
    ])
  else
    HAVE_DECL_CEILF=0
  fi
  if test $HAVE_DECL_CEILF = 0 || test $REPLACE_CEILF = 1; then
    dnl No libraries are needed to link lib/ceilf.c.
    CEILF_LIBM=
  fi
  AC_SUBST([CEILF_LIBM])
])

# Determines the libraries needed to get the ceilf() function.
# Sets CEILF_LIBM.
AC_DEFUN([gl_FUNC_CEILF_LIBS],
[
  gl_CACHE_VAL_SILENT([gl_cv_func_ceilf_libm], [
    gl_cv_func_ceilf_libm=?
    AC_LINK_IFELSE(
      [AC_LANG_PROGRAM(
         [[#ifndef __NO_MATH_INLINES
           # define __NO_MATH_INLINES 1 /* for glibc */
           #endif
           #include <math.h>
           float (*funcptr) (float) = ceilf;
           float x;]],
         [[x = funcptr(x) + ceilf(x);]])],
      [gl_cv_func_ceilf_libm=])
    if test "$gl_cv_func_ceilf_libm" = "?"; then
      save_LIBS="$LIBS"
      LIBS="$LIBS -lm"
      AC_LINK_IFELSE(
        [AC_LANG_PROGRAM(
           [[#ifndef __NO_MATH_INLINES
             # define __NO_MATH_INLINES 1 /* for glibc */
             #endif
             #include <math.h>
             float (*funcptr) (float) = ceilf;
             float x;]],
           [[x = funcptr(x) + ceilf(x);]])],
        [gl_cv_func_ceilf_libm="-lm"])
      LIBS="$save_LIBS"
    fi
  ])
  CEILF_LIBM="$gl_cv_func_ceilf_libm"
])