Justification

If you ignore an error code and an error occurs, it will be very hard to find the root cause.

Example 1

static int ccbb_example(void)
{
   /* log error code */
   return e;
}

void CCBB_X(void)
{
   ccbb_example(); /* WRONG: return value is ignored */
}

Example 2

static int ccbb_example(void)
{
   return (e);
}

void CCBB_X(void)
{
   if (ccbb_example() == OK) /* RIGHT */
   {
      ...
   }
}