Ractor: Fix moving embedded objects

[Bug #20271]
[Bug #20267]
[Bug #20255]

`rb_obj_alloc(RBASIC_CLASS(obj))` will always allocate from the basic
40B pool, so if `obj` is larger than `40B`, we'll create a corrupted
object when we later copy the shape_id.

Instead we can use the same logic than ractor copy, which is
to use `rb_obj_clone`, and later ask the GC to free the original
object.

We then must turn it into a `T_OBJECT`, because otherwise
just changing its class to `RactorMoved` leaves a lot of
ways to keep using the object, e.g.:

```
a = [1, 2, 3]
Ractor.new{}.send(a, move: true)
[].concat(a) # Should raise, but wasn't.
```

If it turns out that `rb_obj_clone` isn't performant enough
for some uses, we can always have carefully crafted specialized
paths for the types that would benefit from it.

1 files changed, 1 insertions, 0 deletions

diff --git a/internal/gc.h b/internal/gc.h
index 4e9b4554e8..454f8ec685 100644
--- a/internal/gc.h
+++ b/internal/gc.h
@@ -183,6 +183,7 @@ struct rb_gc_object_metadata_entry {
 /* gc.c */
 RUBY_ATTR_MALLOC void *ruby_mimmalloc(size_t size);
 RUBY_ATTR_MALLOC void *ruby_mimcalloc(size_t num, size_t size);
+void rb_gc_ractor_moved(VALUE dest, VALUE src);
 void ruby_mimfree(void *ptr);
 void rb_gc_prepare_heap(void);
 void rb_objspace_set_event_hook(const rb_event_flag_t event);