Warning C28302

For C++ reference-parameter 'parameter_name', an extra _Deref_ operator was found on 'annotation'.

This warning is reported when an extra level of _Deref_ is used on a parameter of a reference type such as T &a. A common mistake when using SAL1 annotations is to use __deref on a reference type. Reference types are understood by SAL, so all annotations are already applied to the underlying type. It's typically not an issue in SAL2 because the free-floating __deref annotation was removed. If you intend to apply an annotation to a subtype, then you should instead use the SAL2 _AT_ or _Outref_ annotations.

Example

// Oops, trying to apply __elem_writableTo to the pointer being referenced
void f( __deref __elem_writableTo(size) int *& buffer, int size);

void func()
{
  int buffer[100] = {};
  int *pbuffer = buffer;
  f(pbuffer, 100);
}

To address the issue, update to SAL2 annotations:

// Fix warning by switching to SAL2 syntax which has annotations that better describe what the function does.
void f( _Outref_result_buffer_(size) int *& buffer);

See also

Understanding SAL