Re: [PATCH] diff --no-index: reset temporary buffer lengths on directory iteration

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On Wed, May 16, 2012 at 2:33 AM, René Scharfe
<rene.scharfe@xxxxxxxxxxxxxx> wrote:
> Am 16.05.2012 06:14, schrieb Bobby Powers:
>
>> Commit 875b91b3 introduced a regression when using diff --no-index
>> with directories.  When iterating through a directory, the switch to
>> strbuf from heap-allocated char arrays caused paths to form like
>> 'dir/file1', 'dir/file1file2', rather than 'dir/file1', 'dir/file2' as
>> expected.  By resetting the length on each iteration (but not
>> buf.alloc), we avoid this.
>>
>> Signed-off-by: Bobby Powers <bobbypowers@xxxxxxxxx>
>> ---
>>  diff-no-index.c |    7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>
>
> Nice catch!  Could you please also add a test case so that we can be sure a
> similar bug is not reintroduced later?

Yup, will do.

>
>
>> diff --git a/diff-no-index.c b/diff-no-index.c
>> index b44473e..bec3ea4 100644
>> --- a/diff-no-index.c
>> +++ b/diff-no-index.c
>> @@ -67,7 +67,7 @@ static int queue_diff(struct diff_options *o,
>>                struct strbuf buffer2 = STRBUF_INIT;
>>                struct string_list p1 = STRING_LIST_INIT_DUP;
>>                struct string_list p2 = STRING_LIST_INIT_DUP;
>> -               int i1, i2, ret = 0;
>> +               int len1 = 0, len2 = 0, i1, i2, ret = 0;
>>
>>                if (name1 && read_directory(name1, &p1))
>>                        return -1;
>> @@ -80,18 +80,23 @@ static int queue_diff(struct diff_options *o,
>>                        strbuf_addstr(&buffer1, name1);
>>                        if (buffer1.len && buffer1.buf[buffer1.len - 1] !=
>> '/')
>>                                strbuf_addch(&buffer1, '/');
>> +                       len1 = buffer1.len;
>>                }
>>
>>                if (name2) {
>>                        strbuf_addstr(&buffer2, name2);
>>                        if (buffer2.len && buffer2.buf[buffer2.len - 1] !=
>> '/')
>>                                strbuf_addch(&buffer2, '/');
>> +                       len2 = buffer2.len;
>>                }
>>
>>                for (i1 = i2 = 0; !ret && (i1 < p1.nr || i2 < p2.nr); ) {
>>                        const char *n1, *n2;
>>                        int comp;
>
>
> If you declare len1 and len2 right here at the start of the loop and reset
> the strbufs at its end, you wouldn't have to initialize them to zero and
> they'd have the right scope for their task.

Nope, thats not what we want actually.  At the start of the first
iteration, the buffers have directory names in them, like 'dir_1/' and
'dir_2/'.  The loop appends the directory contents to the directory
path, upon each iteration we only want to clear the last filename from
the buffer, not the entire buffer.

>
> Using type size_t, the type used in struct strbuf, is more correct.

Done.

>
>
>>
>> +                       buffer1.len = len1;
>> +                       buffer2.len = len2;
>
>
> It's cleaner to use strbuf_setlen() instead of setting the len member
> directly.

Done.

>
> Looking at the code, I think the strbufs are never freed and the
> strbuf_reset() calls after the loop should be replaced by ones to
> strbuf_release() in order to avoid leaking.  This is a different issue, but
> would be nice to squash as well.

Yup, I noticed that as well.  I'll send a separate patch out for it.

Thanks for the review!  I'll send a revised patch out momentarily.

yours,
Bobby

>
>
>> +
>>                        if (i1 == p1.nr)
>>                                comp = 1;
>>                        else if (i2 == p2.nr)
>> -- 1.7.10.2
>>
>
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