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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
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.
-rw-r--r--ChangeLog5
-rw-r--r--sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c14
2 files changed, 10 insertions, 9 deletions
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.
diff --git a/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c b/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c
index ef1b3dca1e..5f92a5fee8 100644
--- a/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c
@@ -65,7 +65,7 @@ __nearbyintl (long double x)
}
else if (fabs (u.d[1].d) < TWO52 && u.d[1].d != 0.0)
{
- double high, low, tau;
+ double high = u.d[0].d, low = u.d[1].d, tau;
/* In this case we have to round the low double and handle any
adjustment to the high double that may be caused by rounding
(up). This is complicated by the fact that the high double
@@ -78,8 +78,6 @@ __nearbyintl (long double x)
{
/* If the high/low doubles are the same sign then simply
round the low double. */
- high = u.d[0].d;
- low = u.d[1].d;
}
else if (u.d[1].d < 0.0)
{
@@ -88,8 +86,8 @@ __nearbyintl (long double x)
tau = __nextafter (u.d[0].d, 0.0);
tau = (u.d[0].d - tau) * 2.0;
- high = u.d[0].d - tau;
- low = u.d[1].d + tau;
+ high -= tau;
+ low += tau;
}
low += TWO52;
low -= TWO52;
@@ -100,8 +98,6 @@ __nearbyintl (long double x)
{
/* If the high/low doubles are the same sign then simply
round the low double. */
- high = u.d[0].d;
- low = u.d[1].d;
}
else if (u.d[1].d > 0.0)
{
@@ -109,8 +105,8 @@ __nearbyintl (long double x)
adjust for that. */
tau = __nextafter (u.d[0].d, 0.0);
tau = (u.d[0].d - tau) * 2.0;
- high = u.d[0].d - tau;
- low = u.d[1].d + tau;
+ high -= tau;
+ low += tau;
}
low = TWO52 - low;
low = -(low - TWO52);