gistfile1.txt

#define NEXT goto *opcodes[program[pc++]]

int interpret(char *stack, int sp, char *program) {
  int pc = 0;
  static const void *opcodes[] = {&&push, &&pop, &&add, &&sub, &&ret};
  NEXT;
  
push:
  stack[sp++] = program[pc++];
  NEXT;
  
pop:
  sp--;
  NEXT;
  
add:
  sp--;
  stack[sp - 1] = stack[sp - 1] + stack[sp];
  NEXT;
  
sub:
  sp--;
  stack[sp - 1] = stack[sp - 1] - stack[sp];
  NEXT;

ret:
  return stack[sp - 1];
}