`mandatory_only_cme` should not be in `def`

`def` (`rb_method_definition_t`) is shared by multiple callable
method entries (cme, `rb_callable_method_entry_t`).

There are two issues:

* old -> young reference: `cme1->def->mandatory_only_cme = monly_cme`
  if `cme1` is young and `monly_cme` is young, there is no problem.
  Howevr, another old `cme2` can refer `def`, in this case, old `cme2`
  points young `monly_cme` and it violates gengc assumption.
* cme can have different `defined_class` but `monly_cme` only has
  one `defined_class`. It does not make sense and `monly_cme`
  should be created for a cme (not `def`).

To solve these issues, this patch allocates `monly_cme` per `cme`.
`cme` does not have another room to store a pointer to the `monly_cme`,
so this patch introduces `overloaded_cme_table`, which is weak key map
`[cme] -> [monly_cme]`.

`def::body::iseqptr::monly_cme` is deleted.

The first issue is reported by Alan Wu.

1 files changed, 13 insertions, 4 deletions

diff --git a/gc.c b/gc.c
index 5a723762ad..5fd46defb4 100644
--- a/gc.c
+++ b/gc.c
@@ -6363,6 +6363,8 @@ rb_mark_hash(st_table *tbl)
     mark_st(&rb_objspace, tbl);
 }
 
+const rb_callable_method_entry_t *rb_vm_lookup_overloaded_cme(const rb_callable_method_entry_t *cme);
+
 static void
 mark_method_entry(rb_objspace_t *objspace, const rb_method_entry_t *me)
 {
@@ -6376,7 +6378,13 @@ mark_method_entry(rb_objspace_t *objspace, const rb_method_entry_t *me)
           case VM_METHOD_TYPE_ISEQ:
             if (def->body.iseq.iseqptr) gc_mark(objspace, (VALUE)def->body.iseq.iseqptr);
             gc_mark(objspace, (VALUE)def->body.iseq.cref);
-            if (def->body.iseq.mandatory_only_cme) gc_mark(objspace, (VALUE)def->body.iseq.mandatory_only_cme);
+            if (def->iseq_overload && me->defined_class) { // cme
+                const rb_callable_method_entry_t *monly_cme = rb_vm_lookup_overloaded_cme((const rb_callable_method_entry_t *)me);
+                if (monly_cme) {
+                    gc_mark(objspace, (VALUE)monly_cme);
+                    gc_mark_and_pin(objspace, (VALUE)me);
+                }
+            }
             break;
 	  case VM_METHOD_TYPE_ATTRSET:
 	  case VM_METHOD_TYPE_IVAR:
@@ -9599,9 +9607,6 @@ gc_ref_update_method_entry(rb_objspace_t *objspace, rb_method_entry_t *me)
                 TYPED_UPDATE_IF_MOVED(objspace, rb_iseq_t *, def->body.iseq.iseqptr);
             }
             TYPED_UPDATE_IF_MOVED(objspace, rb_cref_t *, def->body.iseq.cref);
-            if (def->body.iseq.mandatory_only_cme) {
-                TYPED_UPDATE_IF_MOVED(objspace, rb_callable_method_entry_t *, def->body.iseq.mandatory_only_cme);
-            }
             break;
           case VM_METHOD_TYPE_ATTRSET:
           case VM_METHOD_TYPE_IVAR:
@@ -10108,6 +10113,9 @@ gc_ref_update(void *vstart, void *vend, size_t stride, rb_objspace_t * objspace,
 extern rb_symbols_t ruby_global_symbols;
 #define global_symbols ruby_global_symbols
 
+
+st_table *rb_vm_overloaded_cme_table(void);
+
 static void
 gc_update_references(rb_objspace_t *objspace)
 {
@@ -10143,6 +10151,7 @@ gc_update_references(rb_objspace_t *objspace)
     gc_update_table_refs(objspace, objspace->id_to_obj_tbl);
     gc_update_table_refs(objspace, global_symbols.str_sym);
     gc_update_table_refs(objspace, finalizer_table);
+    gc_update_table_refs(objspace, rb_vm_overloaded_cme_table());
 }
 
 static VALUE