Continuation Semantics

Continuation semantics are the traditional way to deal with signals. The idea is that when a signal handler returns, control resumes where it was at the time of the interruption. This is well suited for asynchronous signals in single-threaded processes, as shown in Example 5-1.

This is also used as the exception-handling mechanism in some programming languages, such as PL/1.

Example 5-1 Continuation Semantics

unsigned int nestcount;

unsigned int A(int i, int j) {
    nestcount++;

    if (i==0)
        return(j+1)
    else if (j==0)
        return(A(i-1, 1));
    else
        return(A(i-1, A(i, j-1)));
}

void sig(int i) {
    printf("nestcount = %d\n", nestcount);
}

main() {
    sigset(SIGINT, sig);
    A(4,4);
}