Examples of errors detected by the V1036 diagnostic

V1036. Potentially unsafe double-checked locking.

Blender

V1036 Potentially unsafe double-checked locking. node_ui_storage.cc 46

typedef struct bNodeTree {
  ....
  struct NodeTreeUIStorage *ui_storage;
} bNodeTree;

static void ui_storage_ensure(bNodeTree &ntree)
{
  /* As an optimization, only acquire a lock if the UI storage doesn't exist,
   * because it only needs to be allocated once for every node tree. */
  if (ntree.ui_storage == nullptr) {
    std::lock_guard<std::mutex> lock(global_ui_storage_mutex);
    /* Check again-- another thread may have allocated the
       storage while this one waited. */
    if (ntree.ui_storage == nullptr) {
      ntree.ui_storage = new NodeTreeUIStorage();
    }
  }
}