Why Does C Throw an 'Explicit Specialization in Non-Namespace Scope' Error?

C Explicit Specialization Error in Non-Namespace Scope

A C compilation error may arise when attempting explicit specialization of a member function template outside of the namespace scope, resulting in the message "Explicit specialization in non-namespace scope." This issue pertains to the violation of the C standard that mandates explicit specializations to be declared within the namespace of the template or its enclosing class.

To resolve this issue, consider the following options:

• Use the Correct Scope:
  Explicit specializations must be declared in the namespace of the template they belong to.
• Forward to a Non-Member Function:
  Create a free function for specialization and have the member function forward to it, as in the following example:

namespace detail {
    template <typename TL> void Verify(int, int[]) {}
    template <>            void Verify<int>(int, int[]) {}
}

template<typename T> class CConstraint {
    // ...
    template <typename TL> void Verify(int position, int constraints[]) {
        detail::Verify<TL>(position, constraints);
    }
};

By placing the specialization in the correct scope or forwarding to a non-member function, the compilation error should be resolved.

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