From: Vladimír Čunát <vladimir.cunat@nic.cz>
Date: Thu, 25 Sep 2025 10:25:10 +0000 (+0200)
Subject: contrib/mempattern: silence UBSAN on newer clang
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=refs%2Fmerge-requests%2F1743%2Fhead;p=thirdparty%2Fknot-resolver.git

contrib/mempattern: silence UBSAN on newer clang

Equivalent to
https://gitlab.nic.cz/knot/knot-dns/-/commit/27825e4c595d952

The problem happens now with clang 20.
I don't think I've seen it happen with GCC 15
or with some earlier clang versions.
---

diff --git a/contrib/mempattern.c b/contrib/mempattern.c
index e0c784de1..ea17eb866 100644
--- a/contrib/mempattern.c
+++ b/contrib/mempattern.c
@@ -113,10 +113,16 @@ void mm_ctx_init(knot_mm_t *mm)
 	mm->free = free;
 }
 
+// UBSAN type punning workaround
+static void *mp_alloc_wrap(void *ctx, size_t size)
+{
+	return mp_alloc(ctx, size);
+}
+
 void mm_ctx_mempool(knot_mm_t *mm, size_t chunk_size)
 {
 	mm->ctx = mp_new(chunk_size);
-	mm->alloc = (knot_mm_alloc_t)mp_alloc;
+	mm->alloc = mp_alloc_wrap;
 	mm->free = mm_nofree;
 }