From: Jonathan Tan <jonathantanmy@google.com>
Date: Fri, 24 Feb 2023 23:22:56 GMT
Subject: Re: [PATCH 06/11] sparse-checkout: avoid using internal API of unpack-trees, take 2
Message-ID: <20230224232256.2038749-1-jonathantanmy@google.com>
In-Reply-To: <8955b45e35474e5feb826101423470d0b51e5470.1677143700.git.gitgitgadget@gmail.com>

"Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com> writes:
> From: Elijah Newren <newren@gmail.com>
> 
> Commit 2f6b1eb794 ("cache API: add a "INDEX_STATE_INIT" macro/function,
> add release_index()", 2023-01-12) mistakenly added some initialization
> of a member of unpack_trees_options that was intended to be
> internal-only.  Further, it served no purpose as it simply duplicated
> the initialization that unpack-trees.c code was already doing.
> 
> Signed-off-by: Elijah Newren <newren@gmail.com>
> ---
>  builtin/sparse-checkout.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
> index 4b7390ce367..8d5ae6f2a60 100644
> --- a/builtin/sparse-checkout.c
> +++ b/builtin/sparse-checkout.c
> @@ -217,7 +217,6 @@ static int update_working_directory(struct pattern_list *pl)
>  	o.head_idx = -1;
>  	o.src_index = r->index;
>  	o.dst_index = r->index;
> -	index_state_init(&o.result, r);
>  	o.skip_sparse_checkout = 0;
>  
>  	setup_work_tree();

The commit message seems to imply that in this code path, there is some
code in unpack-trees.c that runs index_state_init(), but that doesn't
seem to be the case. memset-ting the result field with a junk value
causes valgrind to fail with the following trace:

  ==2035705== Invalid read of size 8
  ==2035705==    at 0x30D982: lazy_init_name_hash (name-hash.c:602)
  ==2035705==    by 0x30DDDA: index_file_exists (name-hash.c:721)
  ==2035705==    by 0x3F71A8: check_ok_to_remove (unpack-trees.c:2430)
  ==2035705==    by 0x3F74EE: verify_absent_1 (unpack-trees.c:2495)
  ==2035705==    by 0x3F75C6: verify_absent_sparse (unpack-trees.c:2523)
  ==2035705==    by 0x3F2A15: apply_sparse_checkout (unpack-trees.c:566)
  ==2035705==    by 0x3F6849: update_sparsity (unpack-trees.c:2147)
  ==2035705==    by 0x1FC105: update_working_directory (sparse-checkout.c:228)

so it might be better to move the init invocation to update_sparsity()
instead of only removing it.