DPL: Constructors and operator= for DPC++ execution policies are not explicitly specified

[andreyfe1]

The following are not explicitly specified for DPC++ execution policies:

• copy constructor
• move constructor
• copy assignment
• move assignment

Is their behavior considered to be default?
For example. What if an implementation decide to mark operator= as deleted, will it be considered as a deviation from the Spec?

[rarutyun]

From my perspective if we don't explicitly list the default members the behavior is as they are there with = default marker. The argument for that is the destructor. I believe that we didn't specify the destructor almost anywhere. But it's valid operation since we can create the objects on the stack (e.g. device_policy) and this is the desired scenario.

Even if we don't specify the layout explicitly I think we should consider prohibiting those default members as the breaking change. Consider one more example: Imagine that the class has all default members specified as = default without specifying the layout. I think user would assume that they can be called. Then, on the next version of the product the implementation has been changed and contains the reference in the layout which breaks the ability to call copy-assignment. To me it also looks like breaking change.