-# round.m4 serial 1
+# round.m4 serial 5
dnl Copyright (C) 2007 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
AC_REQUIRE([gl_MATH_H_DEFAULTS])
dnl Persuade glibc <math.h> to declare round().
AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
- gl_CHECK_LIBM_FUNC([round], [x = round(x);], [], [
- AC_REQUIRE([gl_FUNC_FLOOR])
- ROUND_LIBM=$FLOOR_LIBM
- AC_LIBOBJ([round])])])
+ AC_CHECK_DECLS([round], , , [#include <math.h>])
+ if test "$ac_cv_have_decl_round" = yes; then
+ gl_CHECK_MATH_LIB([ROUND_LIBM], [x = round (x);])
+ fi
+ if test "$ac_cv_have_decl_round" = yes && test "$ROUND_LIBM" != missing; then
+ dnl Test whether round() produces correct results. On NetBSD 3.0, for
+ dnl x = 1/2 - 2^-54, the system's round() returns a wrong result.
+ AC_REQUIRE([AC_PROG_CC])
+ AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+ AC_CACHE_CHECK([whether round works], [gl_cv_func_round_works],
+ [
+ save_LIBS="$LIBS"
+ LIBS="$LIBS $ROUND_LIBM"
+ AC_TRY_RUN([
+#include <float.h>
+#include <math.h>
+int main()
+{
+ /* 2^DBL_MANT_DIG. */
+ static const double TWO_MANT_DIG =
+ /* Assume DBL_MANT_DIG <= 5 * 31.
+ Use the identity
+ n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5). */
+ (double) (1U << (DBL_MANT_DIG / 5))
+ * (double) (1U << ((DBL_MANT_DIG + 1) / 5))
+ * (double) (1U << ((DBL_MANT_DIG + 2) / 5))
+ * (double) (1U << ((DBL_MANT_DIG + 3) / 5))
+ * (double) (1U << ((DBL_MANT_DIG + 4) / 5));
+ volatile double x = 0.5 - 0.5 / TWO_MANT_DIG;
+ exit (x < 0.5 && round (x) != 0.0);
+}], [gl_cv_func_round_works=yes], [gl_cv_func_round_works=no],
+ [case "$host_os" in
+ netbsd*) gl_cv_func_round_works="guessing no";;
+ *) gl_cv_func_round_works="guessing yes";;
+ esac
+ ])
+ LIBS="$save_LIBS"
+ ])
+ case "$gl_cv_func_round_works" in
+ *no) ROUND_LIBM=missing ;;
+ esac
+ fi
+ if test "$ac_cv_have_decl_round" != yes || test "$ROUND_LIBM" = missing; then
+ REPLACE_ROUND=1
+ AC_LIBOBJ([round])
+ gl_FUNC_FLOOR_LIBS
+ gl_FUNC_CEIL_LIBS
+ ROUND_LIBM="$FLOOR_LIBM $CEIL_LIBM"
+ fi
+ AC_SUBST([ROUND_LIBM])
+])