[PATCH v3] patch-ids: document intentional const-casting in patch_id_neq()
- From
Tian Yuchen <cat@malon.dev>
- Date
- Mar 9, 2026, 06:51 UTC
- Message-ID
- <20260309065140.108644-1-cat@malon.dev>
- In-Reply-To
- <20260308150203.86299-1-cat@malon.dev>
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> --- patch-ids.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
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;
-- 2.43.0