+ m4_ifdef([gl_FUNC_TRUNCL_IEEE], [
+ if test $gl_truncl_required = ieee && test $REPLACE_TRUNCL = 0; then
+ AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+ AC_CACHE_CHECK([whether truncl works according to ISO C 99 with IEC 60559],
+ [gl_cv_func_truncl_ieee],
+ [
+ save_LIBS="$LIBS"
+ LIBS="$LIBS $TRUNCL_LIBM"
+ AC_RUN_IFELSE(
+ [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+]gl_LONG_DOUBLE_MINUS_ZERO_CODE[
+]gl_LONG_DOUBLE_SIGNBIT_CODE[
+static long double dummy (long double f) { return 0; }
+int main (int argc, char *argv[])
+{
+ long double (*my_truncl) (long double) = argc ? truncl : dummy;
+ /* Test whether truncl (-0.3L) is -0.0L. */
+ if (signbitl (minus_zerol) && !signbitl (my_truncl (-0.3L)))
+ return 1;
+ return 0;
+}
+ ]])],
+ [gl_cv_func_truncl_ieee=yes],
+ [gl_cv_func_truncl_ieee=no],
+ [case "$host_os" in
+ # Guess yes on glibc systems.
+ *-gnu*) gl_cv_func_truncl_ieee="guessing yes" ;;
+ # If we don't know, assume the worst.
+ *) gl_cv_func_truncl_ieee="guessing no" ;;
+ esac
+ ])
+ LIBS="$save_LIBS"
+ ])
+ case "$gl_cv_func_truncl_ieee" in
+ *yes) ;;
+ *) REPLACE_TRUNCL=1 ;;
+ esac
+ fi
+ ])