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, 0 deletions

diff --git a/vm_method.c b/vm_method.c
index d2bd677e6a..4504468789 100644
--- a/vm_method.c
+++ b/vm_method.c
@@ -351,6 +351,8 @@ rb_method_definition_create(rb_method_type_t type, ID mid)
     def = ZALLOC(rb_method_definition_t);
     def->type = type;
     def->original_id = mid;
+    static uintptr_t method_serial = 1;
+    def->method_serial = method_serial++;
     return def;
 }