per-method serial number

Methods and their definitions can be allocated/deallocated on-the-fly.
One pathological situation is when a method is deallocated then another
one is allocated immediately after that.  Address of those old/new method
entries/definitions can be the same then, depending on underlying
malloc/free implementation.

So pointer comparison is insufficient.  We have to check the contents.
To do so we introduce def->method_serial, which is an integer unique to
that specific method definition.

PS: Note that method_serial being uintptr_t rather than rb_serial_t is
intentional.  This is because rb_serial_t can be bigger than a pointer
on a 32bit system (rb_serial_t is at least 64bit).  In order to preserve
old packing of struct rb_call_cache, rb_serial_t is inappropriate.

1 files changed, 2 insertions, 2 deletions

diff --git a/internal.h b/internal.h
index fe2b028f47..c35e3bdb6f 100644
--- a/internal.h
+++ b/internal.h
@@ -2350,7 +2350,7 @@ struct rb_call_cache {
         (CACHELINE
          - sizeof(rb_serial_t)                                   /* method_state */
          - sizeof(struct rb_callable_method_entry_struct *)      /* me */
-         - sizeof(struct rb_callable_method_definition_struct *) /* def */
+         - sizeof(uintptr_t)                                     /* method_serial */
          - sizeof(enum method_missing_reason)                    /* aux */
          - sizeof(VALUE (*)(                                     /* call */
                struct rb_execution_context_struct *e,
@@ -2362,7 +2362,7 @@ struct rb_call_cache {
 
     /* inline cache: values */
     const struct rb_callable_method_entry_struct *me;
-    const struct rb_method_definition_struct *def;
+    uintptr_t method_serial; /* me->def->method_serial */
 
     VALUE (*call)(struct rb_execution_context_struct *ec,
                   struct rb_control_frame_struct *cfp,