Need help understanding this for loop code in C

Question

Consider the following code in C:

void main()
{
    int a=0;

    for(printf(\"\\nA\"); a; printf(\"\\nB\"));

    printf(\"\\nC\");
    printf(\"\\nD\");            


        

Answer 1

What is the full "for" loop syntax in C (and others in case they are compatible)?

This question quotes the applicable part of the standard. The 3rd expression shouldn't be evaluated unless the loop executes at least once. So, I'd say that in the 2nd case the old compiler is wrong to print 'B'.