This program demonstrate that 'exit' used as keyword compiles properly, but has no effect.

nop-exit.cpp

/*

http://www.cplusplus.com/reference/cstdlib/exit/

https://github.com/sui77/rc-switch/pull/35/files/361888c4aef6f4c977108539ab858dd910532a41

	for(unsigned int i = 1; i < numProto; i++ ) {
		if (receiveProtocol(i, changeCount))
			exit;
	}


The "exit" line in the above code has no effect.
It is an expression of type pointer-to function ( void(*)(int) ).

*/


// included by default in Arduino
#include <cstdlib>
#include <cassert>
#include <iostream>

using namespace std;

bool flag=0;

void f() {

    // nop - this is an expression of type pointer-to-function 
    exit;

    flag=1;
}


int main() {

    f();

    assert(flag==1);

    cout << ("PASS") << endl;
    return 0;
}