[PATCH] correct type of EMPTY_TREE_SHA1_BIN

[Jonathan Nieder <jrnieder@gmail.com>]

Junio C Hamano wrote:

>> --- a/cache-tree.c
>> +++ b/cache-tree.c
>> @@ -621,9 +621,18 @@ static void prime_cache_tree_rec(struct cache_tree *it, struct tree *tree)
>>  			struct tree *subtree = lookup_tree(entry.sha1);
>>  			if (!subtree->object.parsed)
>>  				parse_tree(subtree);
>> +			if (!hashcmp(entry.sha1, (unsigned char *)EMPTY_TREE_SHA1_BIN)) {
>> +				warning("empty tree detected! Will be removed in new commits");
>> +				cnt = -1;
>> +				break;
>> +			}
>
> You shouldn't need the cast (if you did, then hashcmp() macro should be
> fixed so that you don't need to).

Isn't this a bug in the definition of EMPTY_TREE_SHA1_BIN rather than
the signature of hashcmp?

-- 8< --
Subject: correct type of EMPTY_TREE_SHA1_BIN

Functions such as hashcmp that expect a binary SHA-1 value take
parameters of type "unsigned char *" to avoid accepting a textual
SHA-1 passed by mistake.  Unfortunately, this means passing the string
literal EMPTY_TREE_SHA1_BIN requires an ugly cast.  Tweak the
definition of EMPTY_TREE_SHA1_BIN to produce a value of more
convenient type.

In the future the definition might change to

	extern const unsigned char empty_tree_sha1_bin[20];
	#define EMPTY_TREE_SHA1_BIN empty_tree_sha1_bin

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
 builtin/checkout.c |    2 +-
 cache.h            |    4 +++-
 notes-merge.c      |    2 +-
 sha1_file.c        |    2 +-
 4 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 757f9a0..cd7f56e 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -404,7 +404,7 @@ static int merge_working_tree(struct checkout_opts *opts,
 		topts.dir->exclude_per_dir = ".gitignore";
 		tree = parse_tree_indirect(old->commit ?
 					   old->commit->object.sha1 :
-					   (unsigned char *)EMPTY_TREE_SHA1_BIN);
+					   EMPTY_TREE_SHA1_BIN);
 		init_tree_desc(&trees[0], tree->buffer, tree->size);
 		tree = parse_tree_indirect(new->commit->object.sha1);
 		init_tree_desc(&trees[1], tree->buffer, tree->size);
diff --git a/cache.h b/cache.h
index d83d68c..3abf895 100644
--- a/cache.h
+++ b/cache.h
@@ -676,9 +676,11 @@ static inline void hashclr(unsigned char *hash)
 
 #define EMPTY_TREE_SHA1_HEX \
 	"4b825dc642cb6eb9a060e54bf8d69288fbee4904"
-#define EMPTY_TREE_SHA1_BIN \
+#define EMPTY_TREE_SHA1_BIN_LITERAL \
 	 "\x4b\x82\x5d\xc6\x42\xcb\x6e\xb9\xa0\x60" \
 	 "\xe5\x4b\xf8\xd6\x92\x88\xfb\xee\x49\x04"
+#define EMPTY_TREE_SHA1_BIN \
+	 ((const unsigned char *) EMPTY_TREE_SHA1_BIN_LITERAL)
 
 int git_mkstemp(char *path, size_t n, const char *template);
 
diff --git a/notes-merge.c b/notes-merge.c
index 71c4d45..1467ad3 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -615,7 +615,7 @@ int notes_merge(struct notes_merge_options *o,
 	bases = get_merge_bases(local, remote, 1);
 	if (!bases) {
 		base_sha1 = null_sha1;
-		base_tree_sha1 = (unsigned char *)EMPTY_TREE_SHA1_BIN;
+		base_tree_sha1 = EMPTY_TREE_SHA1_BIN;
 		OUTPUT(o, 4, "No merge base found; doing history-less merge");
 	} else if (!bases->next) {
 		base_sha1 = bases->item->object.sha1;
diff --git a/sha1_file.c b/sha1_file.c
index d86a8db..b44fc95 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -2048,7 +2048,7 @@ static struct cached_object {
 static int cached_object_nr, cached_object_alloc;
 
 static struct cached_object empty_tree = {
-	EMPTY_TREE_SHA1_BIN,
+	EMPTY_TREE_SHA1_BIN_LITERAL,
 	OBJ_TREE,
 	"",
 	0
-- 
1.7.4