parsers: avoid signed integer overflow in calculation of leaf-node index
If v = -INT_MAX - 1, -v would exceed INT_MAX. I don't think this would cause
problems such as issue4627, but we can't blame it as a compiler bug because
signed integer overflow is undefined in C.
--- a/mercurial/parsers.c Tue Apr 28 17:38:02 2015 -0700
+++ b/mercurial/parsers.c Wed Apr 29 23:07:34 2015 +0900
@@ -1312,7 +1312,7 @@
const char *n;
Py_ssize_t i;
- v = -v - 1;
+ v = -(v + 1);
n = index_node(self, v);
if (n == NULL)
return -2;
@@ -1368,7 +1368,7 @@
return 0;
}
if (v < 0) {
- const char *oldnode = index_node(self, -v - 1);
+ const char *oldnode = index_node(self, -(v + 1));
int noff;
if (!oldnode || !memcmp(oldnode, node, 20)) {