Example error handling in c.

example.c

/**
 * error type
 */
typedef int state_t;

/**
 * error states
 */
#define STATE_SUCCESS (0)
#define STATE_NULL_PTR (1)

/**
 * macros for error handling
 */
#define ERRSR(state) if( (s=state) ) { return s; }
#define ERRSPR( PTR, STATECODE )                            \
    ERRSR( ( NULL == (PTR) ? STATECODE : STATE_SUCCESS) )   \
#define ERRSB(state) if( (s=state) ) { break; }
#define ERRSPB( PTR, STATECODE )                            \
    ERRSB( ( NULL == (PTR) ? STATECODE : STATE_SUCCESS) )   \

state_t methodA()
{
  state_t s = STATE_SUCCESS;
  char *str = NULL;  

  do
  {
    str = (char*) malloc(...);
    ERRSPB(str, STATE_NULL_PTR);
    
    //do something

    ERRSPB(...);
  }
  while(0);

  //cleanup
  if ( NULL != str )
  {
    free(str);
  }

  return s;
}

state_t methodB()
{
  state_t s = STATE_SUCCESS;
  char *str = NULL;   

  str = (char*) malloc(...);
  ERRSPR(str, STATE_NULL_PTR);

  //do something

  ERRSPR(...);

  return s;

}