diff options
| author | Tian Yuchen <cat@malon.dev> | 2026-03-09 14:51:40 +0800 |
|---|---|---|
| committer | Junio C Hamano <gitster@pobox.com> | 2026-03-09 12:45:19 -0700 |
| commit | 4c223571bef1c008c11ad5028072af862d3e7fe3 (patch) | |
| tree | c02ecea7100fc75a95847a400038d56fc0621c0f | |
| parent | 9a2fb147f2c61d0cab52c883e7e26f5b7948e3ed (diff) | |
| download | git-4c223571bef1c008c11ad5028072af862d3e7fe3.tar.xz | |
patch-ids: document intentional const-casting in patch_id_neq()
The hashmap API requires the comparison function to take const pointers.
However, patch_id_neq() uses lazy evaluation to compute patch IDs on
demand. As established in b3dfeebb (rebase: avoid computing unnecessary
patch IDs, 2016-07-29), this avoids unnecessary work since not all
objects in the hashmap will eventually be compared.
Remove the ten-year-old "NEEDSWORK" comment and formally document
this intentional design trade-off.
Signed-off-by: Tian Yuchen <cat@malon.dev>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
| -rw-r--r-- | patch-ids.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/patch-ids.c b/patch-ids.c index a5683b462c..1fbc88cbec 100644 --- a/patch-ids.c +++ b/patch-ids.c @@ -41,7 +41,14 @@ static int patch_id_neq(const void *cmpfn_data, const struct hashmap_entry *entry_or_key, const void *keydata UNUSED) { - /* NEEDSWORK: const correctness? */ + /* + * We drop the 'const' modifier here intentionally. + * + * Even though eptr and entry_or_key are const, we want to + * lazily compute their .patch_id members; see b3dfeebb (rebase: + * avoid computing unnecessary patch IDs, 2016-07-29). So we cast + * the constness away with container_of(). + */ struct diff_options *opt = (void *)cmpfn_data; struct patch_id *a, *b; |