Re: [PATCH] Don't dereference NULL upon lookup_tree failure.

[Junio C Hamano <gitster@pobox.com>]

Jim Meyering <jim@meyering.net> writes:

> When running on an x86_64 system (either debian unstable or rawhide)
> I see only this:
>
>   0 blocks
>   error: Object 0d57588da39d10795486bd5451bc2660832228e6 is a commit, not a tree
>   fatal: The remote end hung up unexpectedly
>...
> diff --git a/object.c b/object.c
> index 16793d9..eb59550 100644
> --- a/object.c
> +++ b/object.c
> @@ -142,10 +142,14 @@ struct object *parse_object_buffer(const unsigned char *sha1, enum object_type t
>  		obj = &blob->object;
>  	} else if (type == OBJ_TREE) {
>  		struct tree *tree = lookup_tree(sha1);
> -		obj = &tree->object;
> -		if (!tree->object.parsed) {
> -			parse_tree_buffer(tree, buffer, size);
> -			eaten = 1;
> +		if (!tree)
> +		    obj = NULL;
> +		else {
> +		    obj = &tree->object;
> +		    if (!tree->object.parsed) {
> +			    parse_tree_buffer(tree, buffer, size);
> +			    eaten = 1;
> +		    }
>  		}
>  	} else if (type == OBJ_COMMIT) {
>  		struct commit *commit = lookup_commit(sha1);

While this change may be a prudent safeguard, there is something
else going on.  Can you provide the callchain that led to the
parse_object_buffer() that gave SHA1 of a commit object with
type set to OBJ_TREE?  Which caller does that bogus combination?