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Make x86_64 fegetenv preserve exception mask (bug 16198)
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: <libc-alpha at sourceware dot org>
- Date: Wed, 26 Mar 2014 17:37:15 +0000
- Subject: Make x86_64 fegetenv preserve exception mask (bug 16198)
- Authentication-results: sourceware.org; auth=none
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.
2014-03-26 Joseph Myers <joseph@codesourcery.com>
[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.
diff --git a/math/Makefile b/math/Makefile
index 09d14a0..c13ca80 100644
--- a/math/Makefile
+++ b/math/Makefile
@@ -90,7 +90,7 @@ tests = test-matherr test-fenv atest-exp atest-sincos atest-exp2 basic-test \
test-misc test-fpucw test-fpucw-ieee tst-definitions test-tgmath \
test-tgmath-ret bug-nextafter bug-nexttoward bug-tgmath1 \
test-tgmath-int test-tgmath2 test-powl tst-CMPLX tst-CMPLX2 test-snan \
- test-fenv-tls $(tests-static)
+ test-fenv-tls test-fenv-preserve $(tests-static)
tests-static = test-fpucw-static test-fpucw-ieee-static
# We do the `long double' tests only if this data type is available and
# distinct from `double'.
diff --git a/math/test-fenv-preserve.c b/math/test-fenv-preserve.c
new file mode 100644
index 0000000..8288b2c
--- /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"
diff --git a/sysdeps/x86_64/fpu/fegetenv.c b/sysdeps/x86_64/fpu/fegetenv.c
index 364f917..0e0c269 100644
--- a/sysdeps/x86_64/fpu/fegetenv.c
+++ b/sysdeps/x86_64/fpu/fegetenv.c
@@ -22,6 +22,9 @@ int
fegetenv (fenv_t *envp)
{
__asm__ ("fnstenv %0\n"
+ /* fnstenv changes the exception mask, so load back the
+ stored environment. */
+ "fldenv %0\n"
"stmxcsr %1" : "=m" (*envp), "=m" (envp->__mxcsr));
/* Success. */
--
Joseph S. Myers
joseph@codesourcery.com