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Message-ID: <20161004015856.GL1280@port70.net>
Date: Tue, 4 Oct 2016 03:58:56 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: [PATCH] math: fix pow signed shift ub
j is int32_t and thus j<<31 is undefined if j==1, so j is changed to
uint32_t locally as a quick fix, the generated code is not affected.
(this is a strict conformance fix, future c standard may allow 1<<31,
see DR 463. the bug was inherited from freebsd fdlibm, the proper fix
is to use uint32_t for all bit hacks, but that requires more intrusive
changes.)
reported by Daniel Sabogal
---
src/math/pow.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/math/pow.c b/src/math/pow.c
index b66f632..3ddc1b6 100644
--- a/src/math/pow.c
+++ b/src/math/pow.c
@@ -125,11 +125,11 @@ double pow(double x, double y)
else if (iy >= 0x3ff00000) {
k = (iy>>20) - 0x3ff; /* exponent */
if (k > 20) {
- j = ly>>(52-k);
+ uint32_t j = ly>>(52-k);
if ((j<<(52-k)) == ly)
yisint = 2 - (j&1);
} else if (ly == 0) {
- j = iy>>(20-k);
+ uint32_t j = iy>>(20-k);
if ((j<<(20-k)) == iy)
yisint = 2 - (j&1);
}
--
2.10.0
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