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/config.c b/config.c
index 4d05dbc..77ed00b 100644
--- a/config.c
+++ b/config.c
@@ -1943,7 +1943,6 @@ void git_configset_clear(struct config_set *cs)
 		return;
 
 	hashmap_for_each_entry(&cs->config_hash, &iter, entry,
-				struct config_set_element,
 				ent /* member name */) {
 		free(entry->key);
 		string_list_clear(&entry->value_list, 1);