Q: C++ namespace as a macro value I have simple delegate functions in my C++ test code. Since I cannot include the original implementation .cpp files(embedded ones), I use delegate .cpp file in the tests that are running on PC. My idea is to simply use the same macro as a body for the implementation, except the parentheses () and arguments which will supplied according to the signature. 
I tried something like:
void Flash::init()
{
   DELEGATE_DESTINATION();
}

bool Flash::write(args)
{
   DELEGATE_DESTINATION(args);
}

bool Flash::read(args)
{
   DELEGATE_DESTINATION(args);
}

Where
void Flash::init()
bool Flash::write(args)
bool Flash::read(args)

Are identical to the ones in the embedded project implementation ones. In the test files I simply relay the call to the fake implementations. One possible solution would be to already include the signature and implementation in the fake classes not using relaying, I know.
I am having hard time figuring out the macro. I tried something like:
#define FAKE_PREFIX             fakes::device::Flash::
#define DELEGATE_DESTINATION    FAKE_PREFIX##__FUNCTION__

Which expands to FAKE_PREFIX__FUNCTION__
Well then after going through C Preprocessor, Stringify the result of a macro
I can get only fakes expanding in place.
My goal would be to have a result like
fakes::device::Flash::init

and so on for read and write.

A: What you want to do can be done far simpler. You don't need the full power of the pre-processor:


*

*You don't concatenate tokens (:: is not part of a valid token). You just need to print one macro next to another.

*_FUNCTION_ isn't a pre-processor macro, it's a string literal (in gcc and other compilers).
So to do what you want, you need to pass the function name into your macro:
#define FAKE_PREFIX fakes::device::Flash::
#define DELEGATE_DESTINATION(func)  FAKE_PREFIX func

Then you define your functions, like this:
bool Flash::write(args)
{
  DELEGATE_DESTINATION(write)(args);
}

It's all live here.
