preprocessor_transform.c

/**
 * The following preprocessor form allows one to wrap C functions
 */

#define-func-decorator <any> critical_region(args, func)
{
  bool enable_interrupts = false;
  if (are_interrupts_enabled()) {
    DISABLE_INTERRUPTS();
    enable_interrupts = true;
  }
  
  <any> ret = func(args);
  
  if (enable_interrupts) {
    ENABLE_INTERRUPTS();
  }
  
  return ret;
}


#decorate[critical_region]
int something_important(int j) {
  int i = 0;
  if (i == j) {
    return 9;
  }
  
  return i + 8;
}

/**
 * The above code should reduce to something equivalent to the following:
 */
int something_important(int j) {
  bool enable_interrupts = false;
  if (are_interrupts_enabled()) {
    DISABLE_INTERRUPTS();
    enable_interrupts = true;
  }
  
  int ret;
  int i = 0;
  if (i == j) {
    ret = 9;
  }
  
  ret = i + 8;
  
  if (enable_interrupts) {
    ENABLE_INTERRUPTS();
  }
  
  return ret;
}

/**
 * For ease of implementation it might actually reduce to the following
 * which should be equivalent for all intents and purposes
 */

int MANGLED_something_important(int j) {
  int i = 0;
  if (i == j) {
    return 9;
  }
  
  return i + 8;
}

int something_important(int j) {
  bool enable_interrupts = false;
  if (are_interrupts_enabled()) {
    DISABLE_INTERRUPTS();
    enable_interrupts = true;
  }
  
  int ret = MANGLED_something_important(j);
  
  if (enable_interrupts) {
    ENABLE_INTERRUPTS();
  }
  
  return ret;
}