Using default in a switch statement when switching over an enum

Question

What is your procedure when switching over an enum where every enumeration is covered by a case? Ideally you\'d like the code to be future proof, how do you do that?

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Answer 1

Apart from exceptions which would be the preferred solution at runtime (and will handle crazy casting), I tend to use static compile time assertions as well.

You can do the following:

//this fails at compile time when the parameter to the template is false at compile time, Boost should provide a similar facility
template  struct STATIC_ASSERTION_FAILURE;
template <> struct STATIC_ASSERTION_FAILURE{};
#define STATIC_ASSERT( CONDITION_ ) sizeof( STATIC_ASSERTION_FAILURE< (COLboolean)(CONDITION_) > );

//
// this define will break at compile time at locations where a switch is being
// made for the enum. This helps when adding enums
//
// the max number here should be updated when a new enum is added.
//
// When a new enum is added, at the point of the switch (where this
// define is being used), update the switch statement, then update
// the value being passed into the define.
//
#define ENUM_SWITCH_ASSERT( _MAX_VALUE )\
   STATIC_ASSERT( _MAX_VALUE  ==  Enum_Two)

enum Enum
{
    Enum_One = 0,
    Enum_Two = 1
};

Then in your code, whenever you use the enum set:

ENUM_SWITCH_ASSERT( Enum_Two )
switch( e )
{
    case Enum_One:
        do_one();
        break;
    case Enum_Two:
        do_two();
        break;
}

Now whenever you change the macro ENUM_SWITCH_ASSERT to handle a new enum value, it will break at compile time near locations that use the enum set. Helps lots when adding new cases.