Re: [PATCH 8/4] match-trees: drop "x = x" initializations

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

Jeff King <peff@peff.net> writes:

> Of the 8 patches, this is the one I find the least satisfying, if only
> because I do not think gcc's failure is because of complicated control
> flow, and rearranging the code would only hurt readability. And I'm
> quite curious why it complains about "mode", but not about the other
> variables, which are set in the exact same place (and why it would not
> be able to handle such a simple control flow at all).
>
> It makes me wonder if I am missing something, or there is some subtle
> bug. But I can't see it. Other eyes appreciated.

I obviously am not qualified as "other eyes" to catch bugs in this
code as this is entirely mine, but I do not see any obvious reason
that would make the compiler to think mode[12] less initialized than
elem[12] or path[12] either.

These three are all updated by the same tree_entry_extract() call,
and whenever we use mode[12] we use path[12], so if it decides path1
is used or assigned, it should be able to tell mode1 is, too.

Unsatisfactory, it surely is...

>  match-trees.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/match-trees.c b/match-trees.c
> index 26f7ed1..4360f10 100644
> --- a/match-trees.c
> +++ b/match-trees.c
> @@ -71,13 +71,13 @@ static int score_trees(const unsigned char *hash1, const unsigned char *hash2)
>  	if (type != OBJ_TREE)
>  		die("%s is not a tree", sha1_to_hex(hash2));
>  	init_tree_desc(&two, two_buf, size);
> -	while (one.size | two.size) {
> -		const unsigned char *elem1 = elem1;
> -		const unsigned char *elem2 = elem2;
> -		const char *path1 = path1;
> -		const char *path2 = path2;
> -		unsigned mode1 = mode1;
> -		unsigned mode2 = mode2;
> +	while (one.size || two.size) {
> +		const unsigned char *elem1;
> +		const unsigned char *elem2;
> +		const char *path1;
> +		const char *path2;
> +		unsigned mode1 = 0; /* make gcc happy */
> +		unsigned mode2 = 0; /* make gcc happy */
>  		int cmp;
>  
>  		if (one.size)