带验证的 C++ 编译时类名字符串

Question

I would like a way to get a string from a class at compile time, but would also want an error if that class doesn't exist in the scope, so this is not enough:

#define CLASS_STR(c) # c

I guess I could write a post build script as a static analyzer of some sort.

An example would be keypath checking in libextobjc http://devetc.org/code/2014/05/17/safe-and-sane-key-paths.html

It should be simple to grasp, really. Instead of writing "MyClass", one should utilize a macro that can return the class name in a string, while also making sure that class is visible in the scope.

Answer 1

Here is one way to do it:

#include <iostream>
#include <MyLib/MyClass.h>

#define CLASS_STR(__class__) \
({              \
    __class__ *x;\
    #__class__ ;\
})

int main(int argc, char* argv[]) {

    auto className = CLASS_STR(MyClass);

    std::cout << className << std::endl;

    return 0;
}

Notice if I passed in MyKlass to the macro, it will fail to initialize the pointer, so now I have a compile time check that the class is available. After the check, I get a string, which is guaranteed to represent that class.

Of course, one can easily redefine the macro for release builds to just perform the stringification.