From b043abc048e74d5f3fdca37395457e6f24abbe55 Mon Sep 17 00:00:00 2001
From: Peter Zhu <peter@peterzhu.ca>
Date: Tue, 20 May 2025 09:56:42 -0400
Subject: [PATCH] Only define RVALUE_OVERHEAD if undefined

This allows RVALUE_OVERHEAD to be defined elsewhere.
---
 gc/default/default.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/gc/default/default.c b/gc/default/default.c
index 7a488562a7..db8ee7834f 100644
--- a/gc/default/default.c
+++ b/gc/default/default.c
@@ -644,7 +644,9 @@ struct rvalue_overhead {
 size_t rb_gc_impl_obj_slot_size(VALUE obj);
 # define GET_RVALUE_OVERHEAD(obj) ((struct rvalue_overhead *)((uintptr_t)obj + rb_gc_impl_obj_slot_size(obj)))
 #else
-# define RVALUE_OVERHEAD 0
+# ifndef RVALUE_OVERHEAD
+#  define RVALUE_OVERHEAD 0
+# endif
 #endif
 
 #define BASE_SLOT_SIZE (sizeof(struct RBasic) + sizeof(VALUE[RBIMPL_RVALUE_EMBED_LEN_MAX]) + RVALUE_OVERHEAD)