Change bmethod defined_ractor to use id instead

When defining a bmethod, we recorded the current Ractor's object in the
method. However that was never marked and so could be GC'd and reused by
a future Ractor. Instead we can use the Ractor's id, which we expect to
be unique forever.

Co-authored-by: Luke Gruber <luke.gru@gmail.com>

Author: jhawthorn

bootstraptest/test_ractor.rb

@@ -2413,3 +2413,28 @@ def call_test(obj)
     :ok
   end
 RUBY
+
+# When creating bmethods in Ractors, they should only be usable from their
+# defining ractor, even if it is GC'd
+assert_equal 'ok', <<~'RUBY'
+CLASSES = 1000.times.map do
+  Ractor.new do
+    Class.new do
+      define_method(:foo) {}
+    end
+  end
+end.map(&:value).freeze
+
+any = 1000.times.map do
+  Ractor.new do
+    CLASSES.any? do |klass|
+      begin
+        klass.new.foo
+        true
+      rescue RuntimeError
+        false
+      end
+    end
+  end
+end.map(&:value).none? && :ok
+RUBY

method.h

@@ -167,7 +167,7 @@ typedef struct rb_method_refined_struct {
 typedef struct rb_method_bmethod_struct {
     VALUE proc; /* should be marked */
     struct rb_hook_list_struct *hooks;
-    VALUE defined_ractor;
+    rb_serial_t defined_ractor_id;
 } rb_method_bmethod_t;
 
 enum method_optimized_type {

vm_insnhelper.c

@@ -4121,7 +4121,7 @@ vm_call_bmethod_body(rb_execution_context_t *ec, struct rb_calling_info *calling
     VALUE procv = cme->def->body.bmethod.proc;
 
     if (!RB_OBJ_SHAREABLE_P(procv) &&
-        cme->def->body.bmethod.defined_ractor != rb_ractor_self(rb_ec_ractor_ptr(ec))) {
+        cme->def->body.bmethod.defined_ractor_id != rb_ractor_id(rb_ec_ractor_ptr(ec))) {
         rb_raise(rb_eRuntimeError, "defined with an un-shareable Proc in a different Ractor");
     }
 
@@ -4144,7 +4144,7 @@ vm_call_iseq_bmethod(rb_execution_context_t *ec, rb_control_frame_t *cfp, struct
     VALUE procv = cme->def->body.bmethod.proc;
 
     if (!RB_OBJ_SHAREABLE_P(procv) &&
-        cme->def->body.bmethod.defined_ractor != rb_ractor_self(rb_ec_ractor_ptr(ec))) {
+        cme->def->body.bmethod.defined_ractor_id != rb_ractor_id(rb_ec_ractor_ptr(ec))) {
         rb_raise(rb_eRuntimeError, "defined with an un-shareable Proc in a different Ractor");
     }
 

vm_method.c

@@ -1020,7 +1020,7 @@ rb_method_definition_set(const rb_method_entry_t *me, rb_method_definition_t *de
             }
           case VM_METHOD_TYPE_BMETHOD:
             RB_OBJ_WRITE(me, &def->body.bmethod.proc, (VALUE)opts);
-            RB_OBJ_WRITE(me, &def->body.bmethod.defined_ractor, rb_ractor_self(GET_RACTOR()));
+            def->body.bmethod.defined_ractor_id = rb_ractor_id(rb_ec_ractor_ptr(GET_EC()));
             return;
           case VM_METHOD_TYPE_NOTIMPLEMENTED:
             setup_method_cfunc_struct(UNALIGNED_MEMBER_PTR(def, body.cfunc), (VALUE(*)(ANYARGS))rb_f_notimplement_internal, -1);
@@ -1060,7 +1060,6 @@ method_definition_reset(const rb_method_entry_t *me)
         break;
       case VM_METHOD_TYPE_BMETHOD:
         RB_OBJ_WRITTEN(me, Qundef, def->body.bmethod.proc);
-        RB_OBJ_WRITTEN(me, Qundef, def->body.bmethod.defined_ractor);
         /* give up to check all in a list */
         if (def->body.bmethod.hooks) rb_gc_writebarrier_remember((VALUE)me);
         break;