X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=m4%2Fhypotl.m4;h=ce92bece5e89a0c89be6dc7a093ced8595ecbcd3;hb=23eecb48e39afd0d267d64d40ba6bf97aa865e13;hp=e7b0eb242fa064176f456d8eb548bf49aabac6c1;hpb=bf6909e5ca400414ed0730b7f64e48d04993936e;p=gnulib.git

diff --git a/m4/hypotl.m4 b/m4/hypotl.m4
index e7b0eb242..ce92bece5 100644
--- a/m4/hypotl.m4
+++ b/m4/hypotl.m4
@@ -1,5 +1,5 @@
-# hypotl.m4 serial 3
-dnl Copyright (C) 2012 Free Software Foundation, Inc.
+# hypotl.m4 serial 5
+dnl Copyright (C) 2012-2013 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -21,8 +21,19 @@ AC_DEFUN([gl_FUNC_HYPOTL],
   LIBS="$save_LIBS"
   if test $ac_cv_func_hypotl = yes; then
     HYPOTL_LIBM="$HYPOT_LIBM"
+
+    save_LIBS="$LIBS"
+    LIBS="$LIBS $HYPOTL_LIBM"
+    gl_FUNC_HYPOTL_WORKS
+    LIBS="$save_LIBS"
+    case "$gl_cv_func_hypotl_works" in
+      *yes) ;;
+      *) REPLACE_HYPOTL=1 ;;
+    esac
+
     m4_ifdef([gl_FUNC_HYPOTL_IEEE], [
       if test $gl_hypotl_required = ieee && test $REPLACE_HYPOTL = 0; then
+        AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
         AC_CACHE_CHECK([whether hypotl works according to ISO C 99 with IEC 60559],
           [gl_cv_func_hypotl_ieee],
           [
@@ -59,7 +70,13 @@ int main (int argc, char *argv[])
               ]])],
               [gl_cv_func_hypotl_ieee=yes],
               [gl_cv_func_hypotl_ieee=no],
-              [gl_cv_func_hypotl_ieee="guessing no"])
+              [case "$host_os" in
+                         # Guess yes on glibc systems.
+                 *-gnu*) gl_cv_func_hypotl_ieee="guessing yes" ;;
+                         # If we don't know, assume the worst.
+                 *)      gl_cv_func_hypotl_ieee="guessing no" ;;
+               esac
+              ])
             LIBS="$save_LIBS"
           ])
         case "$gl_cv_func_hypotl_ieee" in
@@ -105,3 +122,55 @@ int main (int argc, char *argv[])
   fi
   AC_SUBST([HYPOTL_LIBM])
 ])
+
+dnl Test whether hypotl() works.
+dnl On OpenBSD 5.1/SPARC,
+dnl hypotl (2.5541394760659556563446062497337725156L, 7.7893454113437840832487794525518765265L)
+dnl has rounding errors that eat up the last 8 to 9 decimal digits.
+AC_DEFUN([gl_FUNC_HYPOTL_WORKS],
+[
+  AC_REQUIRE([AC_PROG_CC])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  AC_CACHE_CHECK([whether hypotl works], [gl_cv_func_hypotl_works],
+    [
+      AC_RUN_IFELSE(
+        [AC_LANG_SOURCE([[
+#include <float.h>
+#include <math.h>
+static long double
+my_ldexpl (long double x, int d)
+{
+  for (; d > 0; d--)
+    x *= 2.0L;
+  for (; d < 0; d++)
+    x *= 0.5L;
+  return x;
+}
+volatile long double x;
+volatile long double y;
+volatile long double z;
+int main ()
+{
+  long double err;
+
+  x = 2.5541394760659556563446062497337725156L;
+  y = 7.7893454113437840832487794525518765265L;
+  z = hypotl (x, y);
+  err = z * z - (x * x + y * y);
+  err = my_ldexpl (err, LDBL_MANT_DIG);
+  if (err < 0)
+    err = - err;
+  if (err > 1000.0L)
+    return 1;
+  return 0;
+}
+]])],
+        [gl_cv_func_hypotl_works=yes],
+        [gl_cv_func_hypotl_works=no],
+        [case "$host_os" in
+           openbsd*) gl_cv_func_hypotl_works="guessing no";;
+           *)        gl_cv_func_hypotl_works="guessing yes";;
+         esac
+        ])
+    ])
+])