2 dnl Copyright (C) 2007, 2009 Free Software Foundation, Inc.
3 dnl This file is free software; the Free Software Foundation
4 dnl gives unlimited permission to copy and/or distribute it,
5 dnl with or without modifications, as long as this notice is preserved.
7 AC_DEFUN([gl_FUNC_ROUND],
9 AC_REQUIRE([gl_MATH_H_DEFAULTS])
10 dnl Persuade glibc <math.h> to declare round().
11 AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
12 AC_CHECK_DECLS([round], , , [#include <math.h>])
13 if test "$ac_cv_have_decl_round" = yes; then
14 gl_CHECK_MATH_LIB([ROUND_LIBM], [x = round (x);])
16 if test "$ac_cv_have_decl_round" = yes && test "$ROUND_LIBM" != missing; then
17 dnl Test whether round() produces correct results. On NetBSD 3.0, for
18 dnl x = 1/2 - 2^-54, the system's round() returns a wrong result.
19 AC_REQUIRE([AC_PROG_CC])
20 AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
21 AC_CACHE_CHECK([whether round works], [gl_cv_func_round_works],
24 LIBS="$LIBS $ROUND_LIBM"
25 AC_RUN_IFELSE([AC_LANG_SOURCE([[
31 static const double TWO_MANT_DIG =
32 /* Assume DBL_MANT_DIG <= 5 * 31.
34 n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5). */
35 (double) (1U << (DBL_MANT_DIG / 5))
36 * (double) (1U << ((DBL_MANT_DIG + 1) / 5))
37 * (double) (1U << ((DBL_MANT_DIG + 2) / 5))
38 * (double) (1U << ((DBL_MANT_DIG + 3) / 5))
39 * (double) (1U << ((DBL_MANT_DIG + 4) / 5));
40 volatile double x = 0.5 - 0.5 / TWO_MANT_DIG;
41 exit (x < 0.5 && round (x) != 0.0);
42 }]])], [gl_cv_func_round_works=yes], [gl_cv_func_round_works=no],
44 netbsd*) gl_cv_func_round_works="guessing no";;
45 *) gl_cv_func_round_works="guessing yes";;
50 case "$gl_cv_func_round_works" in
51 *no) ROUND_LIBM=missing ;;
54 if test "$ac_cv_have_decl_round" != yes || test "$ROUND_LIBM" = missing; then
59 ROUND_LIBM="$FLOOR_LIBM $CEIL_LIBM"
61 AC_SUBST([ROUND_LIBM])