Subject: Re: [PATCH 8/9] cache-tree: convert struct cache_tree to use object_id

From: Michael Haggerty <[email-masked]>
Date: Tue, 06 May 2014 16:53:47 +0200

On 05/03/2014 10:12 PM, brian m. carlson wrote:
> Signed-off-by: brian m. carlson <[email-masked]>
> ---
>  builtin/commit.c       |  2 +-
>  builtin/fsck.c         |  4 ++--
>  cache-tree.c           | 30 +++++++++++++++---------------
>  cache-tree.h           |  3 ++-
>  merge-recursive.c      |  2 +-
>  reachable.c            |  2 +-
>  sequencer.c            |  2 +-
>  test-dump-cache-tree.c |  4 ++--
>  8 files changed, 25 insertions(+), 24 deletions(-)
> 
> diff --git a/builtin/commit.c b/builtin/commit.c
> index 9cfef6c..639f843 100644
> --- a/builtin/commit.c
> +++ b/builtin/commit.c
> @@ -1659,7 +1659,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
>  		append_merge_tag_headers(parents, &tail);
>  	}
>  
> -	if (commit_tree_extended(&sb, active_cache_tree->sha1, parents, sha1,
> +	if (commit_tree_extended(&sb, active_cache_tree->sha1.oid, parents, sha1,
>  				 author_ident.buf, sign_commit, extra)) {
>  		rollback_index_files();
>  		die(_("failed to write commit object"));
> diff --git a/builtin/fsck.c b/builtin/fsck.c
> index fc150c8..6854c81 100644
> --- a/builtin/fsck.c
> +++ b/builtin/fsck.c
> @@ -587,10 +587,10 @@ static int fsck_cache_tree(struct cache_tree *it)
>  		fprintf(stderr, "Checking cache tree\n");
>  
>  	if (0 <= it->entry_count) {
> -		struct object *obj = parse_object(it->sha1);
> +		struct object *obj = parse_object(it->sha1.oid);
>  		if (!obj) {
>  			error("%s: invalid sha1 pointer in cache-tree",
> -			      sha1_to_hex(it->sha1));
> +			      sha1_to_hex(it->sha1.oid));
>  			return 1;
>  		}
>  		obj->used = 1;
> diff --git a/cache-tree.c b/cache-tree.c
> index 7fa524a..b7b2d06 100644
> --- a/cache-tree.c
> +++ b/cache-tree.c
> @@ -219,7 +219,7 @@ int cache_tree_fully_valid(struct cache_tree *it)
>  	int i;
>  	if (!it)
>  		return 0;
> -	if (it->entry_count < 0 || !has_sha1_file(it->sha1))
> +	if (it->entry_count < 0 || !has_sha1_file(it->sha1.oid))
>  		return 0;
>  	for (i = 0; i < it->subtree_nr; i++) {
>  		if (!cache_tree_fully_valid(it->down[i]->cache_tree))
> @@ -244,7 +244,7 @@ static int update_one(struct cache_tree *it,
>  
>  	*skip_count = 0;
>  
> -	if (0 <= it->entry_count && has_sha1_file(it->sha1))
> +	if (0 <= it->entry_count && has_sha1_file(it->sha1.oid))
>  		return it->entry_count;
>  
>  	/*
> @@ -311,7 +311,7 @@ static int update_one(struct cache_tree *it,
>  		struct cache_tree_sub *sub;
>  		const char *path, *slash;
>  		int pathlen, entlen;
> -		const unsigned char *sha1;
> +		const struct object_id *sha1;
>  		unsigned mode;
>  
>  		path = ce->name;
> @@ -327,21 +327,21 @@ static int update_one(struct cache_tree *it,
>  				die("cache-tree.c: '%.*s' in '%s' not found",
>  				    entlen, path + baselen, path);
>  			i += sub->count;
> -			sha1 = sub->cache_tree->sha1;
> +			sha1 = &sub->cache_tree->sha1;
>  			mode = S_IFDIR;
>  			if (sub->cache_tree->entry_count < 0)
>  				to_invalidate = 1;
>  		}
>  		else {
> -			sha1 = ce->sha1;
> +			sha1 = (struct object_id *)ce->sha1;

This topic was discussed on the mailing list in the abstract.  Here is a
concrete example.

This cast is undefined, because you can't make the assumption that
cache_entry::sha1 has the same alignment and padding as (struct object_id).

I think the transition will be more tractable if you rewrite the data
structures *first*; in this case changing cache_entry::sha1 to be
(struct object_id) *before* rewriting code that works with it.

> [...]

Michael

-- 
Michael Haggerty
[email-masked]
http://softwareswirl.blogspot.com/