+ m4_ifdef([gl_FUNC_TRUNC_IEEE], [
+ if test $gl_trunc_required = ieee && test $REPLACE_TRUNC = 0; then
+ AC_CACHE_CHECK([whether trunc works according to ISO C 99 with IEC 60559],
+ [gl_cv_func_trunc_ieee],
+ [
+ save_LIBS="$LIBS"
+ LIBS="$LIBS $TRUNC_LIBM"
+ AC_RUN_IFELSE(
+ [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+]gl_DOUBLE_MINUS_ZERO_CODE[
+]gl_DOUBLE_SIGNBIT_CODE[
+int main()
+{
+ /* Test whether trunc (-0.0) is -0.0. */
+ if (signbitd (minus_zerod) && !signbitd (trunc (minus_zerod)))
+ return 1;
+ return 0;
+}
+ ]])],
+ [gl_cv_func_trunc_ieee=yes],
+ [gl_cv_func_trunc_ieee=no],
+ [gl_cv_func_trunc_ieee="guessing no"])
+ LIBS="$save_LIBS"
+ ])
+ case "$gl_cv_func_trunc_ieee" in
+ *yes) ;;
+ *) REPLACE_TRUNC=1 ;;
+ esac
+ fi
+ ])