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math: fix pow signed shift ub

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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
This commit is contained in:
Szabolcs Nagy 2016-10-04 03:58:56 +02:00 committed by Rich Felker
parent 87643335ac
commit 688d3da0f1
1 changed files with 2 additions and 2 deletions
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4
src/math/pow.c
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@ -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);
}