expand_user_path: do not look at NULL path

We explicitly check for and handle the case that the
incoming "path" variable is NULL, but before doing so we
call strchrnul on it, leading to a potential segfault.

We can fix this simply by moving the strchrnul call down; as
a bonus, we can tighten the scope on the associated
variable.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/path.c b/path.c
index 6f2aa699ad63c2f7c65632761efbaebb7f461868..3a5796156bd3d59fbf7627ca4292f60bd5d79b01 100644 (file)
--- a/path.c
+++ b/path.c
@@ -231,12 +231,12 @@ static struct passwd *getpw_str(const char *username, size_t len)
 char *expand_user_path(const char *path)
 {
        struct strbuf user_path = STRBUF_INIT;
-       const char *first_slash = strchrnul(path, '/');
        const char *to_copy = path;
 
        if (path == NULL)
                goto return_null;
        if (path[0] == '~') {
+               const char *first_slash = strchrnul(path, '/');
                const char *username = path + 1;
                size_t username_len = first_slash - username;
                if (username_len == 0) {