Re: [PATCH] fsck.c:fsck_commit() use starts_with() and skip_prefix()

From: Eric Sunshine <sunshine@sunshineco.com>
Date: Mar 18, 2014, 23:09 UTC
Message-ID: <CAPig+cRoRzZKjW3cY86iQxz9iZ_TKT-yyu=6Va5aV_DsCAQquA@mail.gmail.com>
In-Reply-To: <1395182512-17179-1-git-send-email-darrazo16@gmail.com>

Thanks for the submission. Comments below to give you a taste of the Git review process...

On Tue, Mar 18, 2014 at 6:41 PM, Othman Darraz <darrazo16@gmail.com> wrote:

> use of starts_with() instead of memcmp()
>
> use of skip_prefix instead of memcmp() and strlen()

Write proper sentences to explain and justify the change; not sentence fragments.

> Signed-off-by: Othman Darraz <darrazo16@gmail.com>
> ---
>
> I am planning to apply to GSOC 214

Your logic in these changes is rather severely flawed. Running the test suite (t1450, in particular), as the GSoC microproject page suggests, would have clued you in that something was amiss.

Show 15 quoted lines

>  fsck.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fsck.c b/fsck.c
> index 64bf279..5eae856 100644
> --- a/fsck.c
> +++ b/fsck.c
> @@ -290,7 +290,7 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
>         int parents = 0;
>         int err;
>
> -       if (memcmp(buffer, "tree ", 5))
> +       if (starts_with(buffer, "tree "))
>                 return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'tree' line");
>         if (get_sha1_hex(buffer+5, tree_sha1) || buffer[45] != '\n')

One of the reasons for using starts_with() rather than memcmp() is that it allows you to eliminate magic numbers, such as 5. However, if you look closely at this code fragment, you will see that the magic number is still present in the expression 'buffer+5'. starts_with(), might be a better fit.

Show 9 quoted lines

>                 return error_func(&commit->object, FSCK_ERROR, "invalid 'tree' line format - bad sha1");
> @@ -322,15 +322,15 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
>                 if (p || parents)
>                         return error_func(&commit->object, FSCK_ERROR, "parent objects missing");
>         }
> -       if (memcmp(buffer, "author ", 7))
> +       if (starts_with(buffer, "author "))
>                 return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'author' line");
>         buffer += 7;

Same problem here with magic number 7.

Show 5 quoted lines

>         err = fsck_ident(&buffer, &commit->object, error_func);
>         if (err)
>                 return err;
> -       if (memcmp(buffer, "committer ", strlen("committer ")))
> +       buffer = (char* )skip_prefix(buffer,"committer ");

Style: (char *)
Style: whitespace: skip_prefix(foo, "bar")

Regarding the (char *) cast: Is 'buffer' ever modified in this function? If not, would it make sense to make it 'const' (and fix any other small fallout from that change)?

Show 8 quoted lines

> +       if (!buffer)
>                 return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'committer' line");
> -       buffer += strlen("committer ");
>         err = fsck_ident(&buffer, &commit->object, error_func);
>         if (err)
>                 return err;
> --
> 1.9.0.258.g00eda23.dirty