OFFSETOF_VAR macro to simplify hashmap iterators

While we cannot rely on a `__typeof__' operator being portable
to use with `offsetof'; we can calculate the pointer offset
using an existing pointer and the address of a member using
pointer arithmetic for compilers without `__typeof__'.

This allows us to simplify usage of hashmap iterator macros
by not having to specify a type when a pointer of that type
is already given.

In the future, list iterator macros (e.g. list_for_each_entry)
may also be implemented using OFFSETOF_VAR to save hackers the
trouble of using container_of/list_entry macros and without
relying on non-portable `__typeof__'.

v3: use `__typeof__' to avoid clang warnings

Signed-off-by: Eric Wong <e@80x24.org>
Reviewed-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 0 insertions, 1 deletions

diff --git a/attr.c b/attr.c
index ca8be46e8e..9849106627 100644
--- a/attr.c
+++ b/attr.c
@@ -168,7 +168,6 @@ static void all_attrs_init(struct attr_hashmap *map, struct attr_check *check)
 		check->all_attrs_nr = size;
 
 		hashmap_for_each_entry(&map->map, &iter, e,
-					struct attr_hash_entry,
 					ent /* member name */) {
 			const struct git_attr *a = e->value;
 			check->all_attrs[a->attr_nr].attr = a;