[boost] a question about scoped_ptr and checked_delete

From: Bronek Kozicki (brok_at_[hidden])
Date: 2005-10-11 11:49:23

As I understand, checked_delete is being used by scoped_ptr to prevent 
deletion of incomplete type. However, this very simple program is 
accepted by MSVC6, MSVC71 and MinGW (GCC) 3.4.4, even though implicit 
destructor of A is deleting incomplete class A::impl . Only one compiler 
of these that I could test (Comeau 4.3.3) throws compilation error. 
Could we do better?

I know, there are simple workaround - declare destructor in class A or 
use shared_ptr . But as we know, workarounds in user code to generate 
compilation error (not suppress them) are rare thing.

B.

#include <boost/scoped_ptr.hpp>

struct A
{
  struct impl;
  boost::scoped_ptr<impl> impl_;

  A();
};

int main()
{
  A a;
}

struct A::impl
{};

A::A() : impl_(new impl()) {}