Question

I am reviewing some C code, but having a hard time understanding what Callback is exactly. Does anyone know what this means? I’m guessing that it is defining “Callback and x to be both a void *?

typedef void (*Callback)(bool x);

Answer 1

It makes a new type name Callback. Every Callback will be a pointer to a function taking a bool and returning void. In effect Callback will be an alias for that real type. So when you say:

Callback ptr = some_fun;

You’re making a function pointer that points at some_fun. Function pointers are typically passed to other functions as arguments.