Add RVALUE_OVERHEAD and move ractor_belonging_id

This commit adds RVALUE_OVERHEAD for storing metadata at the end of the
slot. This commit moves the ractor_belonging_id in debug builds from the
flags to RVALUE_OVERHEAD which frees the 16 bits in the headers for
object shapes.

1 files changed, 4 insertions, 3 deletions

diff --git a/ractor_core.h b/ractor_core.h
index 294708fcb8..d6b4a21e8d 100644
--- a/ractor_core.h
+++ b/ractor_core.h
@@ -288,6 +288,8 @@ rb_ractor_id(const rb_ractor_t *r)
 }
 
 #if RACTOR_CHECK_MODE > 0
+# define RACTOR_BELONGING_ID(obj) (*(uint32_t *)(((uintptr_t)(obj)) + rb_gc_obj_slot_size(obj)))
+
 uint32_t rb_ractor_current_id(void);
 // If ractor check mode is enabled, shape bits needs to be smaller
 STATIC_ASSERT(shape_bits, SHAPE_ID_NUM_BITS == 16);
@@ -295,8 +297,7 @@ STATIC_ASSERT(shape_bits, SHAPE_ID_NUM_BITS == 16);
 static inline void
 rb_ractor_setup_belonging_to(VALUE obj, uint32_t rid)
 {
-    VALUE flags = RBASIC(obj)->flags & 0xffff0000ffffffff; // 4B
-    RBASIC(obj)->flags = flags | ((VALUE)rid << 32);
+    RACTOR_BELONGING_ID(obj) = rid;
 }
 
 static inline void
@@ -312,7 +313,7 @@ rb_ractor_belonging(VALUE obj)
         return 0;
     }
     else {
-        return RBASIC(obj)->flags >> 32 & 0xFFFF;
+        return RACTOR_BELONGING_ID(obj);
     }
 }