Make x86_64 fegetenv preserve exception mask (bug 16198).

Bug 16198 is x86_64 fegetenv wrongly masking exceptions for which
traps are enabled, because that's a side-effect of the fnstenv
instruction.  This patch fixes it to use fldenv immediately after
fnstenv, like the i386 version.  Tested x86_64 and x86.

	[BZ #16198]
	* sysdeps/x86_64/fpu/fegetenv.c (fegetenv): Use fldenv after
	fnstenv.
	* math/test-fenv-preserve.c: New file.
	* math/Makefile (tests): Add test-fenv-preserve.

1 files changed, 53 insertions, 0 deletions

diff --git a/math/test-fenv-preserve.c b/math/test-fenv-preserve.c
new file mode 100644
index 0000000000..8288b2c971
--- /dev/null
+++ b/math/test-fenv-preserve.c
@@ -0,0 +1,53 @@
+/* Test fegetenv preserves exception mask (bug 16198).
+   Copyright (C) 2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <fenv.h>
+#include <stdio.h>
+
+static int
+do_test (void)
+{
+  fenv_t env;
+
+  if (feenableexcept (FE_INVALID) != 0)
+    {
+      puts ("feenableexcept (FE_INVALID) failed, cannot test");
+      return 0;
+    }
+
+  if (fegetenv (&env) != 0)
+    {
+      puts ("fegetenv failed, cannot test");
+      return 0;
+    }
+
+  int ret = fegetexcept ();
+  if (ret == FE_INVALID)
+    {
+      puts ("fegetenv preserved exception mask, OK");
+      return 0;
+    }
+  else
+    {
+      printf ("fegetexcept returned %d, expected %d\n", ret, FE_INVALID);
+      return 1;
+    }
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"