encountered “cleanup:” in a Foundation code sample in Xcode. What is this?

Question

so in some sample code from this upcoming Core Audio Book i\'ve encountered an unfamiliar symbol

cleanup:

which is used before some dispose(myS

Answer 1

That's a label, to be used in a goto statement.

Answer 2

It's not a comment. It's a label specifying a location for goto.

E.g.

int main (int argc, const char * argv[])
{
    while (1) {
        printf("Is this an infinite loop?\n");
        goto endLabel;
    }

    endLabel:    

    printf("No.");

    return 0;
}

Output:

Is this an infinite loop?
No.