modfl-ieee: Work around test failures on IRIX, OSF/1, mingw.

[gnulib.git] / m4 / modfl.m4

diff --git a/m4/modfl.m4 b/m4/modfl.m4
index 98aa363..7764eb2 100644 (file)
--- a/m4/modfl.m4
+++ b/m4/modfl.m4
@@ -6,6 +6,7 @@ dnl with or without modifications, as long as this notice is preserved.
 
 AC_DEFUN([gl_FUNC_MODFL],
 [
+  m4_divert_text([DEFAULTS], [gl_modfl_required=plain])
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
   AC_REQUIRE([gl_LONG_DOUBLE_VS_DOUBLE])
 
@@ -13,9 +14,63 @@ AC_DEFUN([gl_FUNC_MODFL],
   dnl exists, is defined in the same library as modf(). This is not the case
   dnl on FreeBSD, Solaris.
   gl_MATHFUNC([modfl], [long double], [(long double, long double *)])
-  if test $gl_cv_func_modfl_no_libm = no \
-     && test $gl_cv_func_modfl_in_libm = no; then
+  if test $gl_cv_func_modfl_no_libm = yes \
+     || test $gl_cv_func_modfl_in_libm = yes; then
+    m4_ifdef([gl_FUNC_MODFL_IEEE], [
+      if test $gl_modfl_required = ieee && test $REPLACE_MODFL = 0; then
+        AC_CACHE_CHECK([whether modfl works according to ISO C 99 with IEC 60559],
+          [gl_cv_func_modfl_ieee],
+          [
+            save_LIBS="$LIBS"
+            LIBS="$LIBS $MODFL_LIBM"
+            AC_RUN_IFELSE(
+              [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+]gl_LONG_DOUBLE_MINUS_ZERO_CODE[
+]gl_LONG_DOUBLE_SIGNBIT_CODE[
+/* Compare two numbers with ==.
+   This is a separate function because IRIX 6.5 "cc -O" miscompiles an
+   'x == x' test.  */
+static int
+numeric_equal (long double x, long double y)
+{
+  return x == y;
+}
+static long double dummy (long double x, long double *iptr) { return 0; }
+long double zero;
+long double minus_one = - 1.0L;
+int main (int argc, char *argv[])
+{
+  long double (*my_modfl) (long double, long double *) = argc ? modfl : dummy;
+  long double i;
+  long double f;
+  /* Test modfl(-Inf,...).
+     This test fails on IRIX 6.5, OSF/1 5.1, mingw.  */
+  f = my_modfl (minus_one / zero, &i);
+  if (!(f == 0.0L) || (signbitl (minus_zerol) && !signbitl (f)))
+    return 1;
+  return 0;
+}
+              ]])],
+              [gl_cv_func_modfl_ieee=yes],
+              [gl_cv_func_modfl_ieee=no],
+              [gl_cv_func_modfl_ieee="guessing no"])
+            LIBS="$save_LIBS"
+          ])
+        case "$gl_cv_func_modfl_ieee" in
+          *yes) ;;
+          *) REPLACE_MODFL=1 ;;
+        esac
+      fi
+    ])
+  else
     HAVE_MODFL=0
+  fi
+  if test $HAVE_MODFL = 0 || test $REPLACE_MODFL = 1; then
+    dnl Find libraries needed to link lib/modfl.c.
     if test $HAVE_SAME_LONG_DOUBLE_AS_DOUBLE = 1; then
       AC_REQUIRE([gl_FUNC_MODF])
       MODFL_LIBM="$MODF_LIBM"