Avoid duplicating code

Question

let's say I have:

  switch( choice ) {
  case A:   
     stmt;
     do_stmt_related2A;
  break;

  case B:
     stmt;
     do_stmt_related2B;
  break;

  case C: something_different();
   ...
  }

How could I avoid duplicating stmt code?

But is there any workaround? gcc extension label as value looks quite good for such situation.

   switch( choice ) {
     do {
     case A:  ptr = &&A_label;
     break;
     case B:  ptr = &&B_label;
     } while(0);
              stmt;
              goto *ptr;
     case C: ...

Is there any trick that can do the same in ANSI-C? Edit: Of course I have thought of function/macro/inline. But anything else? It's not about performance either. Just for educational purpose. ;)

Answer 1

Why don't you just refactor stmt (I'm assuming this is a big chunk of instructions rather than a single line) into its own function do_stmt() and call it? Something like:

switch( choice ) {
    case A:
        do_stmt();
        do_stmt_related2A;
        break;
    case B:
        do_stmt();
        do_stmt_related2B;
        break;
    case C: something_different();
        ...
}

That gcc trick is truly hideous. I would rather have readable code over such monstrosities any day.

You should always assume that the programmer that inherits your code is a homicidal maniac who knows where you live :-)

Answer 2

How could I avoid duplicating stmt code?

By putting it into a function and call that.

And, no, you do not know whether this will slow down your application until you profiled it and found it to be the bottleneck. (And in case it really is, use a macro or, if that's C99, make the function inline.)