MISRA.FUNC.UNUSEDPAR.UNNAMED

Unnamed formal parameter of a non-virtual function is not used.

MISRA-C++ Rule 0-1-11 (required): There shall be no unused parameters (named or unnamed) in non-virtual functions.

This rule is also covered by MISRA.FUNC.UNUSEDPAR.

Rationale

Unused function parameters are often due to design changes and can lead to mismatched parameter lists.

Exception

An unnamed parameter in the definition of a function that is used as a callback does not violate this rule.

Example

typedef int16_t ( * CallbackFn )( int16_t a, int16_t b );

int16_t Callback_1 ( int16_t a, int16_t b ) // Compliant
{
   return a + b;
}
int16_t Callback_2 ( int16_t a, int16_t b ) // Non-compliant
{
   return a;
}
int16_t Callback_3 ( int16_t, int16_t b ) // Compliant by exception
{
   return b;
}

void Dispatch ( int16_t n,
                int16_t a,
                int16_t b,
                int16_t c,   // Non-compliant
                int16_t )    // Non-compliant if Dispatch not a callback.
{
   CallbackFn pFn;

   switch ( n )
   {
      case 0: pFn = &Callback_1; break;
      case 1: pFn = &Callback_2; break;
      default: pFn = &Callback_3; break;
   }
   ( *pFn )( a, b );
}