[PATCH] diff-delta.c: make FLEX_ARRAY=1 work.

I remarked previously that diff-delta.c does not work with FLEX_ARRAY=1.
Here is one attempt to change this.  It conceivably still suffers from
potential misalignment problems (which would likely need some union type
magic to avoid 100%), but at least the index calculation should not go
as horribly wrong as previously.

---
Junio C Hamano [off-list ref] writes:

"Shawn O. Pearce" [off-list ref] writes:

quoted

I'll try to track it down tomorrow.  But the immediate workaround was
to just add '-DFLEX_ARRAY=/* empty */' to my CFLAGS and recompile
the world.  This compiler accepts the empty FLEX_ARRAY macro but
I'm not sure what feature test(s) would be necessary to make Git
able to automatically set that, seeing as how the tests defined in
8e97 are perfectly reasonable and didn't pass.
..., but will try to come up with a reasonable
detection patch....

Actually I would be more worried about the breakage in FLEX_ARRAY=1 case
than misdetection.  Even if your compiler supports the flexible array
members, the fallback to FLEX_ARRAY=1 ought to work and you are seeing a
case where it doesn't.

 diff-delta.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/diff-delta.c b/diff-delta.c
index 9e440a9..099235c 100644
--- a/diff-delta.c
+++ b/diff-delta.c

@@ -247,7 +247,7 @@ struct delta_index * create_delta_index(const void *buf, unsigned long bufsize)
 	/* Now create the packed index in array form rather than
 	 * linked lists */
 
-	memsize = sizeof(*index)
+	memsize = (char *)&index->hash - (char *)index
 		+ sizeof(*packed_hash) * (hsize+1)
 		+ sizeof(*packed_entry) * entries;
 

@@ -264,7 +264,7 @@ struct delta_index * create_delta_index(const void *buf, unsigned long bufsize)
 	index->src_size = bufsize;
 	index->hash_mask = hmask;
 
-	mem = index + 1;
+	mem = &index->hash;
 	packed_hash = mem;
 	mem = packed_hash + (hsize+1);
 	packed_entry = mem;

-- 
1.5.3.6.995.ge8abd