hashmap.h: make sure map entries are tightly packedkb/fast-hashmap-pack-struct

Extending 'struct hashmap_entry' with an int-sized member shouldn't waste
memory on 64-bit systems. This is already documented in api-hashmap.txt,
but needs '__attribute__((__packed__))' to work.

Reduces e.g.

 struct name_entry {
     struct hashmap_entry ent;
     int namelen;
     char *name;
 };

from 32 to 24 bytes.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/hashmap.h b/hashmap.h
index a816ad47b1..b64567bc17 100644
--- a/hashmap.h
+++ b/hashmap.h
@@ -15,7 +15,7 @@ extern unsigned int memihash(const void *buf, size_t len);
 
 /* data structures */
 
-struct hashmap_entry {
+struct __attribute__((__packed__)) hashmap_entry {
 	struct hashmap_entry *next;
 	unsigned int hash;
 };