2 dnl Copyright (C) 2007, 2009-2010 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 "$ac_cv_have_decl_round" = yes; then
14 gl_CHECK_MATH_LIB([ROUND_LIBM], [x = round (x);])
15 if test "$ROUND_LIBM" != missing; then
16 dnl Test whether round() produces correct results. On NetBSD 3.0, for
17 dnl x = 1/2 - 2^-54, the system's round() returns a wrong result.
18 AC_REQUIRE([AC_PROG_CC])
19 AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
20 AC_CACHE_CHECK([whether round works], [gl_cv_func_round_works],
23 LIBS="$LIBS $ROUND_LIBM"
24 AC_RUN_IFELSE([AC_LANG_SOURCE([[
30 static const double TWO_MANT_DIG =
31 /* Assume DBL_MANT_DIG <= 5 * 31.
33 n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5). */
34 (double) (1U << (DBL_MANT_DIG / 5))
35 * (double) (1U << ((DBL_MANT_DIG + 1) / 5))
36 * (double) (1U << ((DBL_MANT_DIG + 2) / 5))
37 * (double) (1U << ((DBL_MANT_DIG + 3) / 5))
38 * (double) (1U << ((DBL_MANT_DIG + 4) / 5));
39 volatile double x = 0.5 - 0.5 / TWO_MANT_DIG;
40 exit (x < 0.5 && round (x) != 0.0);
41 }]])], [gl_cv_func_round_works=yes], [gl_cv_func_round_works=no],
43 netbsd* | aix*) gl_cv_func_round_works="guessing no";;
44 *) gl_cv_func_round_works="guessing yes";;
49 case "$gl_cv_func_round_works" in
50 *no) ROUND_LIBM=missing ;;
53 if test "$ROUND_LIBM" = missing; then
59 if test $HAVE_DECL_ROUND = 0 || test $REPLACE_ROUND = 1; then
64 dnl Append $FLOOR_LIBM to ROUND_LIBM, avoiding gratuitous duplicates.
65 case " $ROUND_LIBM " in
67 *) ROUND_LIBM="$ROUND_LIBM $FLOOR_LIBM" ;;
69 dnl Append $CEIL_LIBM to ROUND_LIBM, avoiding gratuitous duplicates.
70 case " $ROUND_LIBM " in
72 *) ROUND_LIBM="$ROUND_LIBM $CEIL_LIBM" ;;
75 AC_SUBST([ROUND_LIBM])