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Handle GC triggering while building the initial id_to_obj_tbl

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GC can trigger while we build the table, and if it sweeps an object
with an ID, it may not find it in the `id_to_obj` table.
This commit is contained in:
Jean Boussier 2025-05-11 20:30:42 +02:00
parent 2fe8b9cd3d
commit 8b7a4d167a
Notes: git 2025-05-11 20:05:18 +00:00 
Merged: https://github.com/ruby/ruby/pull/13303
1 changed files with 9 additions and 1 deletions
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10
gc.c
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@ -1777,6 +1777,7 @@ rb_gc_pointer_to_heap_p(VALUE obj)
static unsigned long long next_object_id = OBJ_ID_INITIAL;
static VALUE id_to_obj_value = 0;
static st_table *id_to_obj_tbl = NULL;
static bool id_to_obj_tbl_built = false;
void
rb_gc_obj_id_moved(VALUE obj)
@ -1910,9 +1911,13 @@ object_id_to_ref(void *objspace_ptr, VALUE object_id)
if (!id_to_obj_tbl) {
rb_gc_vm_barrier(); // stop other ractors
// GC Must not trigger while we build the table, otherwise if we end
// up freeing an object that had an ID, we might try to delete it from
// the table even though it wasn't inserted yet.
id_to_obj_tbl = st_init_table(&object_id_hash_type);
id_to_obj_value = TypedData_Wrap_Struct(0, &id_to_obj_tbl_type, id_to_obj_tbl);
rb_gc_impl_each_object(objspace, build_id_to_obj_i, (void *)id_to_obj_tbl);
id_to_obj_tbl_built = true;
}
VALUE obj;
@ -1941,7 +1946,10 @@ obj_free_object_id(VALUE obj)
RUBY_ASSERT(FIXNUM_P(obj_id) || RB_TYPE_P(obj, T_BIGNUM));
if (!st_delete(id_to_obj_tbl, (st_data_t *)&obj_id, NULL)) {
rb_bug("Object ID seen, but not in id_to_obj table: object_id=%llu object=%s", NUM2ULL(obj_id), rb_obj_info(obj));
// If we're currently building the table then it's not a bug
if (id_to_obj_tbl_built) {
rb_bug("Object ID seen, but not in id_to_obj table: object_id=%llu object=%s", NUM2ULL(obj_id), rb_obj_info(obj));
}
}
}
}