+ if 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 $ROUND_LIBM"
+ AC_RUN_IFELSE([AC_LANG_SOURCE([[
+#include <float.h>
+#include <math.h>
+int main()
+{
+ /* 2^DBL_MANT_DIG. */
+ static const double TWO_MANT_DIG =
+ /* Assume DBL_MANT_DIG <= 5 * 31.
+ Use the identity
+ n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5). */
+ (double) (1U << (DBL_MANT_DIG / 5))
+ * (double) (1U << ((DBL_MANT_DIG + 1) / 5))
+ * (double) (1U << ((DBL_MANT_DIG + 2) / 5))
+ * (double) (1U << ((DBL_MANT_DIG + 3) / 5))
+ * (double) (1U << ((DBL_MANT_DIG + 4) / 5));
+ volatile double x = 0.5 - 0.5 / TWO_MANT_DIG;
+ exit (x < 0.5 && round (x) != 0.0);
+}]])], [gl_cv_func_round_works=yes], [gl_cv_func_round_works=no],
+ [case "$host_os" in
+ netbsd* | aix*) 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 "$ROUND_LIBM" = missing; then
+ REPLACE_ROUND=1
+ fi
+ m4_ifdef([gl_FUNC_ROUND_IEEE], [
+ if test $gl_round_required = ieee && test $REPLACE_ROUND = 0; then
+ AC_CACHE_CHECK([whether round works according to ISO C 99 with IEC 60559],
+ [gl_cv_func_round_ieee],
+ [
+ save_LIBS="$LIBS"
+ LIBS="$LIBS $ROUND_LIBM"
+ AC_RUN_IFELSE(
+ [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+]gl_DOUBLE_MINUS_ZERO_CODE[
+]gl_DOUBLE_SIGNBIT_CODE[
+int main()
+{
+ /* Test whether round (-0.0) is -0.0. */
+ if (signbitd (minus_zerod) && !signbitd (round (minus_zerod)))
+ return 1;
+ return 0;
+}
+ ]])],
+ [gl_cv_func_round_ieee=yes],
+ [gl_cv_func_round_ieee=no],
+ [gl_cv_func_round_ieee="guessing no"])
+ LIBS="$save_LIBS"
+ ])
+ case "$gl_cv_func_round_ieee" in
+ *yes) ;;
+ *) REPLACE_ROUND=1 ;;
+ esac
+ fi
+ ])
+ else
+ HAVE_DECL_ROUND=0