svn commit: r342851 - head/lib/msun/src

[Pedro F. Giffuni]

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);