Re: [PATCH] repository: fix free problem with repo_clear(the_repository)

[Stefan Beller <sbeller@google.com>]

On Wed, May 9, 2018 at 10:04 AM, Nguyễn Thái Ngọc Duy <pclouds@gmail.com> wrote:
> the_repository is special. One of the special things about it is that
> it does not allocate a new index_state object like submodules but
> points to the global the_index variable instead. As a global variable,
> the_index cannot be free()'d.

ok. That is the situation we're in.

>
> Add an exception for this in repo_clear(). In the future perhaps we
> would be able to allocate the_repository's index on heap too. Then we
> can remove revert this.
>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>  I was trying to test the new parsed_object_pool_clear() and found this.

So this would go with the latest sb/object-store-alloc ?

My impression was that we never call repo_clear() on
the_repository, which would allow us to special case
the_repository further just as I did in v2 of that series[1] by
having static allocations for certain objects in case of \
the_repository.

[1] https://public-inbox.org/git/20180501213403.14643-14-sbeller@google.com/

We could just deal with all the exceptions, but that makes repo_clear
ugly IMHO.

I would rather special case the_repository even more instead
of having it allocate all its things on the heap. (However we rather
want to profile it and argue with data....)

>  repository.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/repository.c b/repository.c
> index a4848c1bd0..f44733524a 100644
> --- a/repository.c
> +++ b/repository.c
> @@ -238,7 +238,9 @@ void repo_clear(struct repository *repo)
>
>         if (repo->index) {
>                 discard_index(repo->index);
> -               FREE_AND_NULL(repo->index);
> +               if (repo->index != &the_index)
> +                       free(repo->index);
> +               repo->index = NULL;

So after this we have a "dangling" the_index.
It is not really dangling, but it is not part of the_repository any more
and many places still use the_index, it might make up for interesting
bugs?

What is your use case of repo_clear(the_repository)?

Thanks,
Stefan