I'm not sure how exactly to read this:
void (*signal(int sig, void (*func)(int))) (int);
I know that void (*func)(int) is a pointer to a function accepting int and returning void.
My best guess is: signal is a function accepting int, and void (*func)(int), which returns a pointer to a function accepting int and returning void (so another void (*func)(int)). I am just a bit confused by this usage, and also the fact that this website is not able to translate it properly.
Your reading is correct.
The signal function takes two arguments, an int and a void (*)(int) (i.e. a pointer to a function that takes an int and returns void), and returns a void (*)(int).
As for cdecl, you need to remove the parameter names so it recognizes it as a declaration. So if you pass it this:
void (*signal(int, void (*)(int))) (int);
It returns this:
declare signal as function (int, pointer to function (int) returning void) returning pointer to function (int) returning void
When dealing with function pointers, it makes code more readable to use a typedef for them. In fact, the Linux man page for signal defines it as follows:
typedef void (*sighandler_t)(int);
sighandler_t signal(int signum, sighandler_t handler);
Which is much clearer than the explicit version.
