Re: [PATCH] Off-by-one error in get_path_prefix(), found by Valgrind
On Wed, Jun 07, 2006 at 01:01:40PM -0400, Pavel Roskin wrote:
Show 23 quoted lines
> From: Pavel Roskin <proski@gnu.org>
>
> Signed-off-by: Pavel Roskin <proski@gnu.org>
> ---
>
> builtin-tar-tree.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/builtin-tar-tree.c b/builtin-tar-tree.c
> index 5f740cf..05da1f2 100644
> --- a/builtin-tar-tree.c
> +++ b/builtin-tar-tree.c
> @@ -166,8 +166,8 @@ static unsigned int ustar_header_chksum(
> static int get_path_prefix(const struct strbuf *path, int maxlen)
> {
> int i = path->len;
> - if (i > maxlen)
> - i = maxlen;
> + if (i >= maxlen)
> + i = maxlen - 1;
> while (i > 0 && path->buf[i] != '/')
> i--;
> return i;Argh, yes. Thanks, Pavel! However, the other branch is incorrect, too: accessing path->buf[path->len] is wrong, even if it's within the buffer. In order to use a length variable to point to the end of some string we need to subtract 1. *sigh* So, how about this one instead?
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Show changes to builtin-tar-tree.c +2 −1
diff --git a/builtin-tar-tree.c b/builtin-tar-tree.c
index 5f740cf..7663b9b 100644
--- a/builtin-tar-tree.c
+++ b/builtin-tar-tree.c
@@ -168,8 +168,9 @@ static int get_path_prefix(const struct
int i = path->len;
if (i > maxlen)
i = maxlen;
- while (i > 0 && path->buf[i] != '/')
+ do {
i--;
+ } while (i > 0 && path->buf[i] != '/');
return i;
}
