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 */
_______________________________________________
svn-src-all@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/svn-src-all
To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"

Reply via email to