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

diff --git a/src/math/pow.c b/src/math/pow.c
index b66f632..3ddc1b6 100644 (file)
--- 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);
                        }