MISRA.SWITCH.NODEFAULT

No default clause at the end of a switch statement.

MISRA-C Rule 15.3 (required): The final clause of a switch statement shall be the default clause.

The requirement for a final default clause is defensive programming. This clause shall either take appropriate action or contain a suitable comment as to why no action is taken.

MISRA-C++ Rule 6-4-6 (required): The final clause of a switch statement shall be the default-clause.

Rationale

The requirement for a final default-clause is defensive programming. This clause shall either take appropriate action, or else contain a suitable comment as to why no action is taken.

Exception

If the condition of a switch statement is of type enum, and all the enumerators are listed in case labels, then the default-clause is not required as the rules associated with enums are intended to ensure that the enum cannot be assigned values outside of its set of enumerators. Note that it may still be appropriate to include a default-clause for the purpose of defensive programming.

Example

switch ( int16 )
{
case 0:
   break;
case 1:
case 2:
   break;
                 // Non-compliant — default clause is required.
}
enum Colours { RED, BLUE, GREEN } colour;

switch ( colour )
{
   case RED:
      break;
   case GREEN:
      break;
                 // Non-compliant — default clause is required.
}
switch ( colour )
{
   case RED:
      break;
   case BLUE:
      break;
   case GREEN:
      break;
                 // Compliant — exception allows no default in this case
}