restricting c++ template usage to POD types

Question

I have a c++ template class, which only operates correctly if the templatized type is plain old data. Anything with a constructor that does anything will not work correctly.

I'd like to somehow get a compiletime or runtime warning when someone tries to do so anyway.

//this should generate error
myclass<std::string> a;

//this should be fine
myclass<int> b;

is there a trick to do this?

Answer 1

#include <type_traits>

template<typename T>
class myclass
{
    static_assert(std::is_pod<T>::value, "T must be POD");

    // stuff here...
};

The above will cause a compilation error if you pass a non-POD type as the template parameter. This solution requires C++11 for the <type_traits> header and static_assert keyword.

EDIT: You can also implement this in C++03 if your compiler supports TR1 (most do):

#include <tr1/type_traits>

template<typename T>
class myclass
{
    static char T_must_be_pod[std::tr1::is_pod<T>::value ? 1 : -1];

    // stuff here...
};