Is possible, in C , to overload the ""_something operator for function identifiers or callables in order to make it have custom behaviour?

I recently saw something similar in this cppcon video, where the presenter is exposing how to build a unit test framework using modules, zero macros... but I am not understanding well how the ""_test is possible, or how C understands that for that callable should perform such an action defined in the body of the operator overloading implementation.

template <typename T>
auto "some_name"_test(T a, T b);

Can someone explain the details behind this?

CodePudding user response：

The UDL operator "" is just a function call. Functions can return anything. They can, for example, return an object type which has an overloaded operator(), and is therefore callable. They can return an object type with an overloaded operator=, and is therefore assignable. Etc.

It's not about how you overload the UDL operator; it's about what your overload returns.