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authorJoseph Myers <joseph@codesourcery.com>2016-09-28 21:11:58 +0000
committerJoseph Myers <joseph@codesourcery.com>2016-09-28 21:11:58 +0000
commitb59ad2db99df74326ae28926299469eecce6f468 (patch)
treec18cd839284e4ce4ca1b9edc06a4f61032c077f4 /math
parente83be730910c341f2f02ccc207b0586bb04fc21a (diff)
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Fix iszero for excess precision.
Floating-point classification macros are supposed to remove any excess range or precision from their arguments. This patch fixes the non-sNaN version of iszero to do so, by casting the argument to its own type. (This will of course work only for standard-conforming excess precision, not for what GCC does on 32-bit x86 by default where the back end hides excess precision from the front end; the same applies to most of the classification macros in that case, as showed up when we made them use GCC built-in functions.) (iseqsig will have the reverse issue, needing to ensure that when an underlying function is used it's for a type wide enough not to remove any excess precision, since comparison macros must not remove excess precision.) Tested for x86_64 and x86. * math/math.h [__GLIBC_USE (IEC_60559_BFP_EXT) && !__SUPPORT_SNAN__] (iszero): Cast argument to its own type. * math/test-iszero-excess-precision.c: New file. * math/Makefile (tests): Add test-iszero-excess-precision. (CFLAGS-test-iszero-excess-precision.c): New variable.
Diffstat (limited to 'math')
-rw-r--r--math/Makefile4
-rw-r--r--math/math.h2
-rw-r--r--math/test-iszero-excess-precision.c49
3 files changed, 53 insertions, 2 deletions
diff --git a/math/Makefile b/math/Makefile
index 6c58b97..7ccd59a 100644
--- a/math/Makefile
+++ b/math/Makefile
@@ -156,7 +156,7 @@ tests = test-matherr test-fenv atest-exp atest-sincos atest-exp2 basic-test \
test-signgam-ullong-init test-nan-overflow test-nan-payload \
test-fexcept test-fexcept-traps test-fesetexcept \
test-fesetexcept-traps test-fetestexceptflag test-femode \
- test-femode-traps $(tests-static)
+ test-femode-traps test-iszero-excess-precision $(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 \
@@ -266,6 +266,8 @@ CFLAGS-test-signgam-ullong-init-static.c = -std=c99
CFLAGS-test-math-isinff.cc = -std=gnu++11
+CFLAGS-test-iszero-excess-precision.c = -fexcess-precision=standard
+
# The -lieee module sets the _LIB_VERSION_ switch to IEEE mode
# for error handling in the -lm functions.
install-lib += libieee.a
diff --git a/math/math.h b/math/math.h
index 0a09959..1382baa 100644
--- a/math/math.h
+++ b/math/math.h
@@ -336,7 +336,7 @@ enum
# ifdef __SUPPORT_SNAN__
# define iszero(x) (fpclassify (x) == FP_ZERO)
# else
-# define iszero(x) ((x) == 0)
+# define iszero(x) (((__typeof (x)) (x)) == 0)
# endif
#endif /* Use IEC_60559_BFP_EXT. */
diff --git a/math/test-iszero-excess-precision.c b/math/test-iszero-excess-precision.c
new file mode 100644
index 0000000..52abc5a
--- /dev/null
+++ b/math/test-iszero-excess-precision.c
@@ -0,0 +1,49 @@
+/* Test iszero with excess precision.
+ Copyright (C) 2016 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 <float.h>
+#include <math.h>
+#include <stdio.h>
+
+#define TEST(TYPE, TRUE_MIN) \
+ do \
+ { \
+ if (iszero (TRUE_MIN / 2)) \
+ puts ("iszero removes excess precision for " #TYPE); \
+ else \
+ { \
+ puts ("iszero fails to remove excess precision for " #TYPE); \
+ result = 1; \
+ } \
+ } \
+ while (0)
+
+static int
+do_test (void)
+{
+ int result = 0;
+
+ TEST (float, FLT_TRUE_MIN);
+ TEST (double, DBL_TRUE_MIN);
+ TEST (long double, LDBL_TRUE_MIN);
+
+ return result;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"