Question

The following case compiles fine in MS Visual Studio, but not in g++ 4.6.

Compiling:

    template <typename T>
    struct get_type
    { typedef void type_;};

template <>
    struct get_type<float>
    { typedef float type_; };

template <>
    struct get_type<int>
    { typedef int type_; };

template <typename T, typename P=get_type<T>::type_> // <--- line 16
    struct get_destroy_type
    { static inline void exec(P a) {} };

Results in:

../testlibrary/testlibrary.h:16:34: error: expected type-specifier
../testlibrary/testlibrary.h:16:34: error: expected ‘>’

Doesn’t seem to like it when I use

get_type<T>::type_

as the template argument default. MS Visual Studio (Express 10) compiles this fine. What changes can I make to get g++ to compile this?

Answer 1

Use typename to disambiguate:

template <typename T, typename P = typename get_type<T>::type_>
                                   |______|