When is deleting a template instantiation preferable to deleting a non-template overload?

Question

Suppose I have a template that works with raw pointers:

template
void processPointer(T* ptr);

I don\'t want this to be called

Answer 1

Suppose you want to pass the argument pointer of type void* (or simply nullptr) to your processPointer function and you also want to call its specialization for type Type. Then you should write

processPointer(static_cast(pointer));

for

void processPointer(void*) = delete;

But for

template<>
void processPointer(void*) = delete;

you could write the code which is much shorter:

processPointer(pointer);

So both variants can be used in the different cases.

However the analogue of the variant with non-template overload can be the only way in some cases. Suppose there is a function template with two parameters:

template
void processPointer(T* ptr1, U* ptr2);

You don't want it to be called with void* pointers as the first argument. The partial specialization of function templates is not allowed in C++ so this code is incorrect:

template
void processPointer(void*, U*) = delete;

And you must use another one:

template
void processPointer(void*, U*) = delete;