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, 1 insertions, 1 deletions

diff --git a/submodule-config.c b/submodule-config.c
index 5462acc8ec..c22855cd38 100644
--- a/submodule-config.c
+++ b/submodule-config.c
@@ -100,7 +100,7 @@ static void submodule_cache_clear(struct submodule_cache *cache)
 	 * their .gitmodules blob sha1 and submodule name.
 	 */
 	hashmap_for_each_entry(&cache->for_name, &iter, entry,
-				struct submodule_entry, ent /* member name */)
+				ent /* member name */)
 		free_one_config(entry);
 
 	hashmap_free_entries(&cache->for_path, struct submodule_entry, ent);