为什么可以将 void(*)(int x, int y) 传递给期望 void(*)() 的 attachInterrupt？

Question

I've been inattentive and for some reason created a function that takes two arguments, and I passed it to attachInterrupt like so:

int state = 42;
void simplified_state_handler(){
    state++;
}

void interrupt_func(int x, int y) {
    simplified_state_handler();
}

attachInterrupt(digitalPinToInterrupt(10), interrupt_func, CHANGE);

The code got compiled with no complaints at all, and it even works. Now, a bit later, I really can't understand why. Reading and digging the attachInterrupt code didn't help. Please explain why can I pass such a function at all. I'm keeping the (now) useless simplified_state_handler in the example, maybe it is important.

Answer 1

The compiler settings of the AVR boards allow it.

It is only a warning: invalid conversion from 'void (*)(int, int)' to 'void (*)()' [-fpermissive] .

On other Arduino platforms (SAMD, STM32, esp8266) it is an error.

The compiler settings in AVR platform were benevolent from the start and they can't change them suddenly. Many existing codes would not compile then.