Puzzle #8 (based on C++17)
#include <stdio.h>

template <typename Foo, typename ...Bars>
constexpr auto baz(Foo(*)(Bars......))
{
    return sizeof...(Bars);
}

int main()
{
    return baz(::printf);
}
With given code, pick one answer:
Guaranteed to return 0 from main
Guaranteed to return 1 from main
Guaranteed to return 2 from main
Guaranteed to return 3 from main
Guaranteed to return 4 from main
Guaranteed to return something other from main
Undefined bahaviour
Implementation defined
Will not compile