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

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

René Scharfe <rene.scharfe@lsrfire.ath.cx> writes:

> Hmm, let's see if we can help the compiler follow the code without
> making it harder for people to understand.  The patch looks a bit
> jumbled, but the resulting code is OK in my biased opinion.

I actually think the result is much better than a mere "OK"; the
duplicated "at this point we know path1 (or path2) is missing from
the other side" has been bothering me and I was about to suggest a
similar rewrite before I read your message ;-)

However, the same compiler still thinks {elem,path,mode}1 can be
used uninitialized (but not {elem,path,mode}2).  The craziness I
reported in the previous message is also the same.  With this patch
on top to swap the side we inspect first, the compiler thinks
{elem,path,mode}2 can be used uninitialized but not the other three
variables X-<.

So I like your change for readability, but for GCC 4.4.5 we still
need the unnecessary initialization.

 match-trees.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/match-trees.c b/match-trees.c
index c0c66bb..9ea2c80 100644
--- a/match-trees.c
+++ b/match-trees.c
@@ -77,16 +77,16 @@ static int score_trees(const unsigned char *hash1, const unsigned char *hash2)
 		unsigned mode1, mode2;
 		int cmp = 0;
 
-		if (one.size)
-			elem1 = tree_entry_extract(&one, &path1, &mode1);
-		else
-			/* two has more entries */
-			cmp = 1;
 		if (two.size)
 			elem2 = tree_entry_extract(&two, &path2, &mode2);
 		else
 			/* two lacks this entry */
 			cmp = -1;
+		if (one.size)
+			elem1 = tree_entry_extract(&one, &path1, &mode1);
+		else
+			/* two has more entries */
+			cmp = 1;
 
 		if (!cmp)
 			cmp = base_name_compare(path1, strlen(path1), mode1,