Re: [PATCH 6/9] commit-graph: use fanout value for graph size

[Taylor Blau <me@ttaylorr.com>]

On Thu, Nov 09, 2023 at 02:24:35AM -0500, Jeff King wrote:
> @@ -323,7 +320,8 @@ static int graph_read_oid_lookup(const unsigned char *chunk_start,
>  {
>  	struct commit_graph *g = data;
>  	g->chunk_oid_lookup = chunk_start;
> -	g->num_commits = chunk_size / g->hash_len;
> +	if (chunk_size / g->hash_len != g->num_commits)
> +		return error(_("commit-graph OID lookup chunk is the wrong size"));
>  	return 0;
>  }

My understanding is that you need this error message to come from
graph_read_oid_lookup() in order to pass the "detect incorrect fanout
final value" test, but I wish that we didn't have to, since having the
more-or-less duplicate error messages in the latter "reader notices
fanout/lookup table mismatch" is somewhat unfortunate.

> diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
> index affb959d64..8bd7fcefb5 100755
> --- a/t/t5318-commit-graph.sh
> +++ b/t/t5318-commit-graph.sh
> @@ -560,7 +560,7 @@ test_expect_success 'detect incorrect fanout' '
>
>  test_expect_success 'detect incorrect fanout final value' '
>  	corrupt_graph_and_verify $GRAPH_BYTE_FANOUT2 "\01" \
> -		"oid table and fanout disagree on size"
> +		"OID lookup chunk is the wrong size"
>  '
>
>  test_expect_success 'detect incorrect OID order' '
> @@ -850,7 +850,8 @@ test_expect_success 'reader notices too-small oid fanout chunk' '
>  test_expect_success 'reader notices fanout/lookup table mismatch' '
>  	check_corrupt_chunk OIDF 1020 "FFFFFFFF" &&
>  	cat >expect.err <<-\EOF &&
> -	error: commit-graph oid table and fanout disagree on size
> +	error: commit-graph OID lookup chunk is the wrong size
> +	error: commit-graph required OID lookup chunk missing or corrupted
>  	EOF
>  	test_cmp expect.err err
>  '
> --
> 2.43.0.rc1.572.g273fc7bed6
>
Thanks,
Taylor