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OFFSETOF_VAR macro to simplify hashmap iterators

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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>
This commit is contained in:
Eric Wong
2019-10-06 23:30:41 +00:00
committed by Junio C Hamano
parent c8e424c9c9
commit 23dee69f53
15 changed files with 56 additions and 45 deletions
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5
diff.c
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@ -1038,7 +1038,7 @@ static void pmb_advance_or_null_multi_match(struct diff_options *o,
int i;
char *got_match = xcalloc(1, pmb_nr);
hashmap_for_each_entry_from(hm, match, struct moved_entry, ent) {
hashmap_for_each_entry_from(hm, match, ent) {
for (i = 0; i < pmb_nr; i++) {
struct moved_entry *prev = pmb[i].match;
struct moved_entry *cur = (prev && prev->next_line) ?
@ -1193,8 +1193,7 @@ static void mark_color_as_moved(struct diff_options *o,
* The current line is the start of a new block.
* Setup the set of potential blocks.
*/
hashmap_for_each_entry_from(hm, match,
struct moved_entry, ent) {
hashmap_for_each_entry_from(hm, match, ent) {
ALLOC_GROW(pmb, pmb_nr + 1, pmb_alloc);
if (o->color_moved_ws_handling &
COLOR_MOVED_WS_ALLOW_INDENTATION_CHANGE) {