Translate error codes to string to display

Question

Is there a common way in C++ to translate an error code to a string to display it?

I saw somewhere a err2msg function, with a big switch, but is that re

Answer 1

As far as I am concerned, error codes are just a subset of enums. Since we are not blessed in C++ with pretty enums (which makes logs somehow quite hard to parse), error codes are no more easier.

The solution is pretty simple for error codes though:

class ErrorCode
{
public:
  ErrorCode(): message(0) {}
  explicit ErrorCode(char const* m): message(m) {}

  char const* c_str() const { return message; }
  std::string toString() const
  {
    return message ? std::string(message) : std::string();
  }

private:
  char const* message;
};

std::ostream& operator<<(std::ostream& out, ErrorCode const& ec)
{
  return out << ec.c_str();
}

Of course you can supply the traditional ==, !=, <, etc...

• It's simple!
• It's fast (the code IS the string, no look-up involved)
• It's type safe (you cannot accidentally mix it up with another type)

The idea is to return pointers to the text instead of error codes (though wrapped in a class for type safety).

Usage:

// someErrors.h
extern ErrorCode const ErrorOutOfMemory;

// someErrors.cpp
ErrorCode const ErrorOutOfMemory = ErrorCode("OUT OF MEMORY");