From 9173e3c0b4455a9cc675318554591247543fb640 Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Thu, 20 Aug 2015 17:28:09 +0000 Subject: 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. --- sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) (limited to 'sysdeps') diff --git a/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c b/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c index ef1b3dc..5f92a5f 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); -- cgit v1.1