# Extra Clang Tools 4 documentation

## clang-tidy - misc-unused-raii

# misc-unused-raii

Finds temporaries that look like RAII objects.

The canonical example for this is a scoped lock.

    {
      scoped_lock(&global_mutex);
      critical_section();
    }

The destructor of the scoped_lock is called before the `critical_section` is entered, leaving it unprotected.

We apply a number of heuristics to reduce the false positive count of this check:

- Ignore code expanded from macros. Testing frameworks make heavy use of this.
- Ignore types with trivial destructors. They are very unlikely to be RAII objects and there’s no difference when they are deleted.
- Ignore objects at the end of a compound statement (doesn’t change behavior).
- Ignore objects returned from a call.