Is std::unique_ptr required to know the full definition of T?

by

I have some code in a header that looks like this:

#include <memory>

class Thing;

class MyClass
{
    std::unique_ptr< Thing > my_thing;
};

If I include this header in a cpp that does not include the Thing type definition, then this does not compile under VS2010-SP1:

1>C:\Program Files (x86)\Microsoft
Visual Studio
10.0\VC\include\memory(2067): error C2027: use of undefined type ‘Thing’

Replace std::unique_ptr by std::shared_ptr and it compiles.

So, I’m guessing that it’s the current VS2010 std::unique_ptr‘s implementation that requires the full definition and it’s totally implementation-dependant.

Or is it? Is there something in it’s standard requirements that makes impossible for std::unique_ptr‘s implementation to work with a forward declaration only? It feels strange as it should only hold a pointer to Thing, shouldn’t it?

9 Answers
9

Leave a Comment