2 dnl Copyright (C) 2007, 2009-2012 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 m4_divert_text([DEFAULTS], [gl_round_required=plain])
10 AC_REQUIRE([gl_MATH_H_DEFAULTS])
11 dnl Persuade glibc <math.h> to declare round().
12 AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
13 AC_CHECK_DECLS([round], , , [[#include <math.h>]])
14 if test "$ac_cv_have_decl_round" = yes; then
15 gl_CHECK_MATH_LIB([ROUND_LIBM], [x = round (x);])
16 if test "$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 $ROUND_LIBM"
25 AC_RUN_IFELSE([AC_LANG_SOURCE([[
29 # pragma fenv_access (off)
34 static const double TWO_MANT_DIG =
35 /* Assume DBL_MANT_DIG <= 5 * 31.
37 n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5). */
38 (double) (1U << (DBL_MANT_DIG / 5))
39 * (double) (1U << ((DBL_MANT_DIG + 1) / 5))
40 * (double) (1U << ((DBL_MANT_DIG + 2) / 5))
41 * (double) (1U << ((DBL_MANT_DIG + 3) / 5))
42 * (double) (1U << ((DBL_MANT_DIG + 4) / 5));
43 volatile double x = 0.5 - 0.5 / TWO_MANT_DIG;
44 exit (x < 0.5 && round (x) != 0.0);
45 }]])], [gl_cv_func_round_works=yes], [gl_cv_func_round_works=no],
47 netbsd* | aix*) gl_cv_func_round_works="guessing no";;
48 *) gl_cv_func_round_works="guessing yes";;
53 case "$gl_cv_func_round_works" in
54 *no) ROUND_LIBM=missing ;;
57 if test "$ROUND_LIBM" = missing; then
60 m4_ifdef([gl_FUNC_ROUND_IEEE], [
61 if test $gl_round_required = ieee && test $REPLACE_ROUND = 0; then
62 AC_CACHE_CHECK([whether round works according to ISO C 99 with IEC 60559],
63 [gl_cv_func_round_ieee],
66 LIBS="$LIBS $ROUND_LIBM"
69 #ifndef __NO_MATH_INLINES
70 # define __NO_MATH_INLINES 1 /* for glibc */
73 ]gl_DOUBLE_MINUS_ZERO_CODE[
74 ]gl_DOUBLE_SIGNBIT_CODE[
75 static double dummy (double f) { return 0; }
76 int main (int argc, char *argv[])
78 double (*my_round) (double) = argc ? round : dummy;
79 /* Test whether round (-0.0) is -0.0. */
80 if (signbitd (minus_zerod) && !signbitd (my_round (minus_zerod)))
85 [gl_cv_func_round_ieee=yes],
86 [gl_cv_func_round_ieee=no],
87 [gl_cv_func_round_ieee="guessing no"])
90 case "$gl_cv_func_round_ieee" in
99 if test $HAVE_DECL_ROUND = 0 || test $REPLACE_ROUND = 1; then
100 dnl Find libraries needed to link lib/round.c.
104 dnl Append $FLOOR_LIBM to ROUND_LIBM, avoiding gratuitous duplicates.
105 case " $ROUND_LIBM " in
106 *" $FLOOR_LIBM "*) ;;
107 *) ROUND_LIBM="$ROUND_LIBM $FLOOR_LIBM" ;;
109 dnl Append $CEIL_LIBM to ROUND_LIBM, avoiding gratuitous duplicates.
110 case " $ROUND_LIBM " in
112 *) ROUND_LIBM="$ROUND_LIBM $CEIL_LIBM" ;;
115 AC_SUBST([ROUND_LIBM])