Re: [PATCH] progress: don't dereference before checking for NULL

> In `stop_progress()`, we're careful to check that `p_progress` is
> non-NULL before we dereference it, but by then we have already
> dereferenced it when calling `finish_if_sparse(*p_progress)`. And, for
> what it's worth, we'll go on to blindly dereference it again inside
> `stop_progress_msg()`.
>
> We could return early if we get a NULL-pointer, but let's go one step
> further and BUG instead. The progress API handles NULL just fine, but
> that's the NULL-ness of `*p_progress`, e.g., when running with
> `--no-progress`. If `p_progress` is NULL, chances are that's a mistake.
> For symmetry, let's do the same check in `stop_progress_msg()`, too.
>
> Signed-off-by: Martin Ågren <martin.agren@gmail.com>
> ---
> diff --git a/progress.c b/progress.c
> @@ -319,9 +319,12 @@ static void finish_if_sparse(struct progress *progress)
>  void stop_progress(struct progress **p_progress)
>  {
> +       if (!p_progress)
> +               BUG("don't provide NULL to stop_progress");
> +
>         finish_if_sparse(*p_progress);