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authorJoseph Myers <joseph@codesourcery.com>2015-08-20 17:28:09 +0000
committerJoseph Myers <joseph@codesourcery.com>2015-08-20 17:28:09 +0000
commit9173e3c0b4455a9cc675318554591247543fb640 (patch)
treea0ca9351f3bb4a01c95e8379494e5bd779e29282 /ChangeLog
parent1ae6c72dc10806d416a611ea8cc15640f972ffa7 (diff)
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Fix uninitialized variable use in ldbl-128ibm nearbyintl.
Removing the use of -Wno-uninitialized for math/ shows errors for
ldbl-128ibm:

../sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c: In function '__nearbyintl':
../sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c:119:34: error: 'low' may be used uninitialized in this function [-Werror=maybe-uninitialized]
       u.d[1].d = high - u.d[0].d + low;
                                  ^
../sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c:119:23: error: 'high' may be used uninitialized in this function [-Werror=maybe-uninitialized]
       u.d[1].d = high - u.d[0].d + low;
                       ^

These errors are correct: if the high part of the argument is a NaN,
and the low part is nonzero but has absolute value less than 2^52,
those variables can be used uninitialized.  This patch rearranges the
code so that the variables are always initialized with the natural
values, and then possibly modified later, to avoid this uninitialized
use.  (Note that there are still other issues with this code and NaNs
that are not fixed by this patch.)  No bug filed in Bugzilla or
testcase added for the uninitialized use since it wasn't user-visible
with the compiler I tried (that is, I still got a NaN result).

Tested for powerpc.

	* sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c: Always initialize
	variables for high and low parts before possibly modifying them.
Diffstat (limited to 'ChangeLog')
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diff --git a/ChangeLog b/ChangeLog
index 1de3a2379e..93d556311e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2015-08-20  Joseph Myers  <joseph@codesourcery.com>
+
+	* sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c: Always initialize
+	variables for high and low parts before possibly modifying them.
+
 2015-08-20  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* sysdeps/i386/i686/multiarch/init-arch.h: Removed.