Cannot Pass Variable Args to Nested Variadic Template Call

Question

Compiler: TDM-GCC 5.1.0 (SJLJ Unwinding)

I'm having an issue passing variable number of type arguments to a static variadic template method call inside of a template function. I've tried every syntax variation, but it won't compile, so I can only assume I'm doing this wrong.

Here's the setup:

#include <iostream>

template <class T>
struct Foo
{
    template <class...>
    static void test()
    {
        std::cout << "Foo<T>::test<...>() called.";
    }
};


template <class T, class... Args>
void bar()
{
    Foo<T>::test<Args...>();  //error happens here
}

int main()
{
    bar<int, int>();
}

This gives the compiler error: expected primary-expression before '...' token.

I thought pack expansions looked like Args..., but that doesn't seems to work here.

Any help is appreciated.

You'll probably find this question informative: ["Where and why do I have to put the `template` and `typename` keywords?"](https://stackoverflow.com/questions/610245/where-and-why-do-i-have-to-put-the-template-and-typename-keywords) — WhozCraig, Nov 04 '16 at 16:56

score 1 · Answer 1 · answered Nov 04 '16 at 16:54

1

You need to tell the parser that dependant test is a template:

template <class T, class... Args>
void bar()
{
    Foo<T>::template test<Args...>();  //error happens here
            ^^^^^^^^^
}

demo

answered Nov 04 '16 at 16:54

krzaq

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Cannot Pass Variable Args to Nested Variadic Template Call

1 Answers1