From 3d1b8e7298957711998bfb2e8cce09bcc17e4d46 Mon Sep 17 00:00:00 2001
From: Jean Boussier <jean.boussier@gmail.com>
Date: Thu, 15 May 2025 12:29:54 +0200
Subject: [PATCH] newobj_fill: don't assume RBasic size

The previous implementation assumed `RBasic` size is `2 * sizeof(VALUE)`,
might as well not make assumption and use a proper `sizeof`.

Co-Authored-By: John Hawthorn <john@hawthorn.email>
---
 gc/default/default.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/gc/default/default.c b/gc/default/default.c
index 5bbdc1e026..da1438c2fe 100644
--- a/gc/default/default.c
+++ b/gc/default/default.c
@@ -2073,10 +2073,10 @@ heap_prepare(rb_objspace_t *objspace, rb_heap_t *heap)
 static inline VALUE
 newobj_fill(VALUE obj, VALUE v1, VALUE v2, VALUE v3)
 {
-    VALUE *p = (VALUE *)obj;
-    p[2] = v1;
-    p[3] = v2;
-    p[4] = v3;
+    VALUE *p = (VALUE *)(obj + sizeof(struct RBasic));
+    p[0] = v1;
+    p[1] = v2;
+    p[2] = v3;
     return obj;
 }