Re: [PATCH 05/11] submodule-config: avoid memory leak

From: Junio C Hamano <gitster@pobox.com>
To: "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, Johannes Schindelin <johannes.schindelin@gmx.de>
Subject: Re: [PATCH 05/11] submodule-config: avoid memory leak
Date: Wed, 15 Jun 2022 21:36:45 -0700	[thread overview]
Message-ID: <xmqqmtedw7fm.fsf@gitster.g> (raw)
In-Reply-To: <591166e07d87fdb5efc2769d3e2963e3f0412720.1655336146.git.gitgitgadget@gmail.com> (Johannes Schindelin via GitGitGadget's message of "Wed, 15 Jun 2022 23:35:39 +0000")

"Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
writes:

> From: Johannes Schindelin <johannes.schindelin@gmx.de>
>
> In 961b130d20c9 (branch: add --recurse-submodules option for branch
> creation, 2022-01-28), a funny pattern was introduced where first some
> struct is `xmalloc()`ed, then we resize an array whose element type is
> the same struct, and then the first struct's contents are copied into
> the last element of that array.

Sigh.  The original is butt ugly, with this strange pattern and
structure assignments etc.  I wonder how something like this slipped
through our reviews.

I wonder if it would help for me to stop trusting reviews by less
experienced reviewers too much, and instead give sanity checks to
more patches myself from now on, but I certainly cannot afford the
time and my mental health to do so for all the patches X-<.

Will queue.

>  		if (S_ISGITLINK(name_entry->mode) &&
>  		    is_tree_submodule_active(r, root_tree, tree_path)) {
> -			st_entry = xmalloc(sizeof(*st_entry));
> +			ALLOC_GROW(out->entries, out->entry_nr + 1,
> +				   out->entry_alloc);
> +			st_entry = &out->entries[out->entry_nr++];
> +
>  			st_entry->name_entry = xmalloc(sizeof(*st_entry->name_entry));
>  			*st_entry->name_entry = *name_entry;
>  			st_entry->submodule =
> @@ -766,9 +769,6 @@ static void traverse_tree_submodules(struct repository *r,
>  						root_tree))
>  				FREE_AND_NULL(st_entry->repo);
>  
> -			ALLOC_GROW(out->entries, out->entry_nr + 1,
> -				   out->entry_alloc);
> -			out->entries[out->entry_nr++] = *st_entry;
>  		} else if (S_ISDIR(name_entry->mode))
>  			traverse_tree_submodules(r, root_tree, tree_path,
>  						 &name_entry->oid, out);