c++ - What's the point of const void?

Question

Apparently, it is possible to declare a function returning const void:

const void foo()
{
}

g++ seems to consider the const important, because the following code does not compile:

#include <type_traits>

static_assert(std::is_same<void(), const void()>::value, "const matters");

So does const void have any practical significance?

Answer 1

Not really. But to ignore cv-qualifications on void or to make them errors could create unnecessary complexity in terms of both compiler implementation and end-user code. Consider templates like

  template<typename T>
  const T ...

There's no reason to make using void in that scenario a special case (more than it already is), it would just create headaches.

Also, while const void isn't helpful, const void* has its uses.