Question

How can I rewrite this code in such a way that user is always shown the correct state(CA,AL etc.) string whenever he passes a valid direction.

i.e How do I make sure there is a valid case statement for each of those enum_types in the directions enum during compile time than in runtime?

For. Eg. I have intentionally commented out the case statement for east. Is there a way to catch this at compile time.

My gut feel is (NO) that this is why the language provides a default case and hence this may not be possible. But I’ll leave this to the experts.

#include <iostream>
#include <string>

using namespace::std;

typedef enum 
{
    min_dir = -1,
    north,
    south,
    east,
    west,
}directions;

directions get_direction( string user_choice)
{
    if(user_choice == "north")
    {
        return north;
    }
    else if (user_choice == "south")
    {
        return south;   
    }
    else if (user_choice == "east")
    {
        return east;    
    }
    else if (user_choice == "west")
    {
        return west;    
    }
    else 
    {
        return min_dir;
    }
}

int main()
{
    string user_direction;
    cout << "Enter direction\n";
    cin >> user_direction;

    directions my_dir = get_direction(user_direction);
    cout << " Print direction's description\n";

    if( my_dir == min_dir)
    {
        // User passed junk
        return -1;
    }

    switch(my_dir)
    {
    case north:
        cout << "North - New york\n";break;
    case south:
        cout << "South - Alabama\n";break;
//  case east:
//      cout << "East - North Carolina\n";break;
    case west:
        cout << "West - California\n";break;
    default:
        cout << "Should Ideally never get here\n";break;
    }
    system("pause");
    return 0;
}

Edit:
This is just an example to illustrate the point. This for code at work. They have compile this both in Windows(MSVC) and linux (gcc). Would this only be a warning? I’ll need a stricter enforcement.

Can I write some code that will error out during a make process if an enum doesn’t have a case statement?

Answer 1

In GCC (g++) and Clang, there is -Wswitch-enum, which will warn you if you do not have a case for a possible value for the enum type you’re switching over (even if you have a default case).

In MSVC, there is the comparable C4062 which comes from warning level 3, but it will not warn you if you have a default statement. If you want warnings in that case, you need to enable the level 4 warning C4061, which produces a warning when an enumerated value is missing, even if a default case is provided.

As far as making it an error goes: all compilers have a “treat warnings as errors” option. In GCC and Clang, it’s -Werror; in MSVC, it’s /WX.