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.
Added by shyouhei (Shyouhei Urabe) almost 6 years ago
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.