wildmatch: avoid undefined behavior
The code changed in this commit is designed to check if the pattern
starts with "**/" or contains "/**/" (see 3a078dec33 (wildmatch: fix
"**" special case, 2013-01-01)). Unfortunately when the pattern begins
with "**/" `prev_p = p - 2` is evaluated when `p` points to the second
"*" and so the subtraction is undefined according to section 6.5.6 of
the C standard because the result does not point within the same object
as `p`. Fix this by avoiding the subtraction unless it is well defined.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/wildmatch.c b/wildmatch.c
index 06861bd..694d2f8 100644
--- a/wildmatch.c
+++ b/wildmatch.c
@@ -83,12 +83,12 @@ static int dowild(const uchar *p, const uchar *text, unsigned int flags)
continue;
case '*':
if (*++p == '*') {
- const uchar *prev_p = p - 2;
+ const uchar *prev_p = p;
while (*++p == '*') {}
if (!(flags & WM_PATHNAME))
/* without WM_PATHNAME, '*' == '**' */
match_slash = 1;
- else if ((prev_p < pattern || *prev_p == '/') &&
+ else if ((prev_p - pattern < 2 || *(prev_p - 2) == '/') &&
(*p == '\0' || *p == '/' ||
(p[0] == '\\' && p[1] == '/'))) {
/*
