Date: Wed, 14 Feb 2018 07:59:30 +0000 (UTC) From: Eitan Adler <eadler@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r329259 - head/lib/msun/src Message-ID: <201802140759.w1E7xUCH027314@repo.freebsd.org>
next in thread | raw e-mail | index | archive | help
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 */
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201802140759.w1E7xUCH027314>