Re: [PATCH Outreachy] mru: use double-linked list from list.h

From: Christian Couder <christian.couder@gmail.com>
Date: Sep 29, 2017, 07:18 UTC
Message-ID: <CAP8UFD13obkLWyuCGUpFxryr8DWfQ8W4JNn04ajO50PvF0SnXQ@mail.gmail.com>
In-Reply-To: <20170928224244.pi34zwifnornssqk@sigill.intra.peff.net>

On Fri, Sep 29, 2017 at 12:42 AM, Jeff King <peff@peff.net> wrote:

Show 22 quoted lines

> On Thu, Sep 28, 2017 at 08:38:39AM +0000, Olga Telezhnaya wrote:
>
>> diff --git a/packfile.c b/packfile.c
>> index f69a5c8d607af..ae3b0b2e9c09a 100644
>> --- a/packfile.c
>> +++ b/packfile.c
>> @@ -876,6 +876,7 @@ void prepare_packed_git(void)
>>       for (alt = alt_odb_list; alt; alt = alt->next)
>>               prepare_packed_git_one(alt->path, 0);
>>       rearrange_packed_git();
>> +     INIT_LIST_HEAD(&packed_git_mru.list);
>>       prepare_packed_git_mru();
>>       prepare_packed_git_run_once = 1;
>>  }
>
> I was thinking on this hunk a bit more, and I think it's not quite
> right.
>
> The prepare_packed_git_mru() function will clear the mru list and then
> re-add each item from the packed_git list. But by calling
> INIT_LIST_HEAD() here, we're effectively clearing the packed_git_mru
> list, and we end up leaking whatever was on the list before.

The current code is:

static int prepare_packed_git_run_once = 0;
void prepare_packed_git(void)
{
    struct alternate_object_database *alt;

    if (prepare_packed_git_run_once)
        return;
    prepare_packed_git_one(get_object_directory(), 1);
    prepare_alt_odb();
    for (alt = alt_odb_list; alt; alt = alt->next)
        prepare_packed_git_one(alt->path, 0);
    rearrange_packed_git();
    prepare_packed_git_mru();
    prepare_packed_git_run_once = 1;
}

As we use the "prepare_packed_git_run_once" static, this function will only be called only once when packed_git_mru has not yet been initialized, so there will be no leak.