Captureless lambda cannot be converted to function pointer when stored in std::function

Question

Usually, a C++ lambda without a capture should be convertable to a c-style function pointer. Somehow, converting it using std::function::target does not work (i

Answer 1

In your first call, std::function does not bother with decaying the lambda into a pointer, it just stores it, with its actual type (which is indeed not void()).

You can force the lambda to decay into a pointer before constructing the std::function with the latter by simply using a unary +:

callMe(+[](){});
//     ^