Author: pfg
Date: Mon Jan 7 17:35:09 2019
New Revision: 342851
URL: https://svnweb.freebsd.org/changeset/base/342851
Log:
pow(3): Workaround possible signed shift Undefined Behavior.
j is int32_t and thus j<<31 is undefined if j==1.
Hinted by: muusl-lib (git 688d3da0f1730daddbc954bbc2d27cc96ceee04c)
Discussed with: freebsd-numerics (kargl)
Modified:
head/lib/msun/src/e_pow.c
Modified: head/lib/msun/src/e_pow.c
==============================================================================
--- head/lib/msun/src/e_pow.c Mon Jan 7 16:36:45 2019 (r342850)
+++ head/lib/msun/src/e_pow.c Mon Jan 7 17:35:09 2019 (r342851)
@@ -133,7 +133,7 @@ __ieee754_pow(double x, double y)
k = (iy>>20)-0x3ff; /* exponent */
if(k>20) {
j = ly>>(52-k);
- if((j<<(52-k))==ly) yisint = 2-(j&1);
+ if(((u_int32_t)j<<(52-k))==ly) yisint = 2-(j&1);
} else if(ly==0) {
j = iy>>(20-k);
if((j<<(20-k))==iy) yisint = 2-(j&1);
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