How to deal with noexcept in Visual Studio

Question

I'm trying to create a custom exception that derives from std::exception and overrides what(). At first, I wrote it like this:

class UserException : public std::exception
{
private:
    const std::string message;
public:
    UserException(const std::string &message)
        : message(message)
    {}

    virtual const char* what() const override
    {
        return message.c_str();
    }
};

This works fine in VS2012, but it doesn't compile in GCC 4.8 with -std=c++11:

error: looser throw specifier for ‘virtual const char* UserException::what() const’

So I add noexcept:

virtual const char* what() const noexcept override

This works fine in GCC, but it doesn't compile in Visual Studio (because VS 2012 doesn't support noexcept):

error C3646: 'noexcept' : unknown override specifier

What is the recommended way to deal with this? I want the same code to compile with both compilers and I'm using C++11 features, so I can't compile with different -std.

Answer 1

Use a macro

#ifndef _MSC_VER
#define NOEXCEPT noexcept
#else
#define NOEXCEPT
#endif

And then define the function as

virtual const char* what() const NOEXCEPT override

You could also modify that to allow noexcept on later versions of VS by checking the value of _MSC_VER; for VS2012 the value is 1600.