Subject: Re: [PATCH 01/15] read-cache: fix memleak

From: Junio C Hamano <[email-masked]>
Date: Fri, 20 Mar 2015 20:26:14 -0700

Stefan Beller <[email-masked]> writes:

> `ce` is allocated in make_cache_entry and should be freed if it is not
> used any more. refresh_cache_entry as a wrapper around refresh_cache_ent
> will either return `ce` or a new updated cache entry which is allocated
> to new memory. In that case we need to free `ce` ourselfs.
>
> Signed-off-by: Stefan Beller <[email-masked]>
> ---
>  read-cache.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/read-cache.c b/read-cache.c
> index 8d71860..f72ea9f 100644
> --- a/read-cache.c
> +++ b/read-cache.c
> @@ -747,6 +747,8 @@ struct cache_entry *make_cache_entry(unsigned int mode,
>  		free(ce);
>  		return NULL;
>  	} else {
> +		if (ret != ce)
> +			free(ce);
>  		return ret;
>  	}
>  }

Good, I vaguely recall that we did something similar in another
codepath that forgot the fact that refresh_cache_entry() may make
the incoming ce unnecessary.

As the rule is "if ret is different from ce, then ce must be freed"
in this codepath, I wonder if this is easier to read:

	ret = refresh_cache_entry(ce, ...);
        if (ret != ce)
        	free(ce);
	return ret;