Author: eadler
Date: Wed Feb 14 07:59:30 2018
New Revision: 329259
URL: https://svnweb.freebsd.org/changeset/base/329259
Log:
msun: signed overflow in atan2
As a component of atan2(y, x), the case of x == 1.0 is farmed out to
atan(y). The current implementation of this comparison is vulnerable
to signed integer underflow (that is, undefined behavior), and it's
performed in a somewhat more complicated way than it need be. Change
it to not be quite so cute, rather directly comparing the high/low
bits of x to the specific IEEE-754 bit pattern that encodes 1.0.
Note that while there are three different e_atan* files in the
relevant directory, only this one needs fixing. e_atan2f.c already
compares against the full bit pattern encoding 1.0f, while
e_atan2l.cuses bitwise-ands/ors/nots and so doesn't require a change.
Closes #130
Submitted by: Jeff Walden (@jswalden github PR #130)
Reviewed by: bde
MFC After: 1 month
Modified:
head/lib/msun/src/e_atan2.c
Modified: head/lib/msun/src/e_atan2.c
==============================================================================
--- head/lib/msun/src/e_atan2.c Wed Feb 14 02:51:28 2018 (r329258)
+++ head/lib/msun/src/e_atan2.c Wed Feb 14 07:59:30 2018 (r329259)
@@ -71,7 +71,7 @@ __ieee754_atan2(double y, double x)
if(((ix|((lx|-lx)>>31))>0x7ff00000)||
((iy|((ly|-ly)>>31))>0x7ff00000)) /* x or y is NaN */
return x+y;
- if((hx-0x3ff00000|lx)==0) return atan(y); /* x=1.0 */
+ if(hx==0x3ff00000&&lx==0) return atan(y); /* x=1.0 */
m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */
/* when y = 0 */
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