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Do not use const attribute for nan functions (bug 23277).

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As in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86113 for
__builtin_nan, bits/mathcalls.h wrongly declares the nan function with
the __const__ attribute.  Because the function reads memory pointed to
by an argument, it's only pure, not const.  This patch removes the
incorrect attribute and adds a testcase for the bug.  No __pure__
attribute is added to replace the incorrect __const__ one, since that
would introduce problems when using GCC versions that have the
incorrect built-in __const__ attribute and warn for the combination of
those two attributes.

Tested for x86_64.

	[BZ #23277]
	* math/bits/mathcalls.h [__USE_ISOC99] (nan): Do not use __const__
	attribute.
	* math/test-nan-const.c: New file.
	* math/Makefile (tests): Add test-nan-const.
	(CFLAGS-test-nan-const.c): New variable.
This commit is contained in:
Joseph Myers 2018-06-12 16:57:26 +00:00
parent cb8f6affed
commit 48b12ed54c
4 changed files with 45 additions and 2 deletions
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9
ChangeLog
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@ -1,3 +1,12 @@
2018-06-12 Joseph Myers <joseph@codesourcery.com>
[BZ #23277]
* math/bits/mathcalls.h [__USE_ISOC99] (nan): Do not use __const__
attribute.
* math/test-nan-const.c: New file.
* math/Makefile (tests): Add test-nan-const.
(CFLAGS-test-nan-const.c): New variable.
2018-06-12 H.J. Lu <hongjiu.lu@intel.com>
* benchtests/scripts/compare_strings.py (process_results): Add

4
math/Makefile
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@ -235,7 +235,7 @@ tests = test-matherr-3 test-fenv basic-test \
test-iseqsig-excess-precision test-flt-eval-method \
test-fp-ilogb-constants test-fp-llogb-constants \
test-fe-snans-always-signal test-finite-macros test-narrow-macros \
$(tests-static)
test-nan-const $(tests-static)
tests-static = test-fpucw-static test-fpucw-ieee-static \
test-signgam-uchar-static test-signgam-uchar-init-static \
test-signgam-uint-static test-signgam-uint-init-static \
@ -442,6 +442,8 @@ CFLAGS-test-fe-snans-always-signal.c += -fsignaling-nans
CFLAGS-test-finite-macros.c += -ffinite-math-only
CFLAGS-test-nan-const.c += -fno-builtin
include ../Rules
gen-all-calls = $(gen-libm-calls) $(gen-calls)

2
math/bits/mathcalls.h
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@ -198,7 +198,7 @@ __MATHCALLX (copysign,, (_Mdouble_ __x, _Mdouble_ __y), (__const__));
#ifdef __USE_ISOC99
/* Return representation of qNaN for double type. */
__MATHCALLX (nan,, (const char *__tagb), (__const__));
__MATHCALL (nan,, (const char *__tagb));
#endif

32
math/test-nan-const.c Normal file
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@ -0,0 +1,32 @@
/* Test nan functions do not have const attribute. Bug 23277.
Copyright (C) 2018 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 <math.h>
#include <string.h>
static int
do_test (void)
{
char buf[2] = { '2', 0 };
float a = nanf (buf);
buf[0] = '3';
float b = nanf (buf);
return memcmp (&a, &b, sizeof (float)) == 0;
}
#include <support/test-driver.c>