rb_vm_mark       1946 gc.c           void rb_vm_mark(void *ptr);
rb_vm_mark       2022 gc.c               th->vm->self ? rb_gc_mark(th->vm->self) : rb_vm_mark(th->vm);
rb_vm_mark       1916 vm.c           	vm->self = Data_Wrap_Struct(rb_cRubyVM, rb_vm_mark, vm_free, vm);