Question

I have this function

TOKENP scan_line() {
    TOKENP cur, last = 0;

    while(cur = scan_opd())
        last = cur;

    if (cur = scan_comm())
    #if ENABLE_COMMENT_AS_TOKEN
        add_token(cur);
    #endif
    return last;
}

If the #if directive is false, will it be compiled as

if (cur = scan_comm())
    return last;

or

if (cur = scan_comm());
return last;

?

Answer 1

It will be compiled just as if the disabled line didn’t exist, so:

if (cur = scan_comm())
    return last;

You should use braces to make it clear what you mean.

if (cur = scan_comm())
{
    #if ENABLE_COMMENT_AS_TOKEN
    add_token(cur);
    #endif
}    
return last;