CODEWITHSUNDEEP
c++unit-testingenumsreinterpret-cast
Martin G
Martin G

Reputation: 18129

Is it possible to pass a non-enum value as an enum function parameter?

I have a function that looks like this:

std::string SomeClass::convertStateToString(StateE state) const
{
  std::string stateAsString;
  switch (state)
  {
    case UNKNOWN:
      stateAsString = "UNKNOWN";
      break;
    case OFFLINE:
      stateAsString = "OFFLINE";
      break;
    case ENABLED:
      stateAsString = "ENABLED";
      break;
    case DISABLED:
      stateAsString = "DISABLED";
      break;
    default:
      stateAsString = "ABNORMAL";
      break;
  }
  return stateAsString;
}

Where StateE is defined as:

typedef enum
{
  UNKNOWN      = 0,
  OFFLINE      = 1,
  ENABLED      = 2,
  DISABLED     = 3
} StateE;

For unit testing purposes i want to feed some bad data to convertStateToString and verify that i get "ABNORMAL" back. Is this possible?

In other words, is it possible to pass a value outside the range of an enum as an in-parameter to a function where the signature of the function says the parameter is of the enum type?

After having experimented with pointers and reinterpret_cast, i'm almost ready to claim that the function convertStateToString can not under any circumstances return "ABNORMAL".

No method is too hackish!

Upvotes: 0

Views: 573

Answers (3)

Bill Lynch
Bill Lynch

Reputation: 82026

I don't see the problem:

std::string convertStateToString(StateE state);

int main() {
    std::cout << convertStateToString(StateE(30)) << "\n";
}

Outputs:

ABNORMAL

Upvotes: 1

Adrien BARRAL
Adrien BARRAL

Reputation: 3604

You can write this in your unit test : 

convertStateToString(static_cast<StateE>(10));

This will force your code to pass in the "default" of your switch/case.

Upvotes: 2

Igor Stoppa
Igor Stoppa

Reputation: 333

No matter in how many ways C++ tries to enforce proper type checking, it should still be possible to just take the address of a memory location and change its content. Ex: declare a variable of type StateE, get its address, write in it a value that is out of range, then pass it to the function. Probably the variable should be volatile.

Upvotes: 1

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