Compilation Error on Recursive Variadic Template Function

Question

I\'ve prepared a simple variadic template test in Code::Blocks, but I\'m getting an error:

No matching function for call to \'OutputSizes()\'

Answer 1

It's because you didn't provide a base case. You extracted the last data type of the variadic template parameter- then you tried to match an empty variadic parameter to a function taking a type and a variadic parameter. You need to provide a "base case" for when the variadic parameter is empty.

using namespace std;

template 
void OutputSizes()
{
    std::cout << typeid(FirstDatatype).name() << ": " << sizeof(FirstDatatype) << std::endl;
    OutputSizes();
}

template
void OutputSizes() // We're called when there's no template arguments
                   // left in the pack
{
}

int main()
{
    OutputSizes();
    return 0;
}

Edit: The many-zero overloads I have shown here actually only work when you take actual run-time arguments too based on the template types. If you only take template parameters directly, you have use two-one recursion like shown in Howard Hinnant's answer.