Why would you use 'extern "C++"'?

Question

In this article the keyword extern can be followed by "C" or "C++". Why would you use 'extern "C++"'? Is it practical?

Answer 1

The language permits:

extern "C" {   #include "foo.h" } 

What if foo.h contains something which requires C++ linkage?

    void f_plain(const char *);     extern "C++" void f_fancy(const std::string &); 

That's how you keep the linker happy.

Answer 2

There is no real reason to use extern "C++". It merely make explicit the linkage that is the implicit default. If you have a class where some members have extern "C" linkage, you may wish the explicit state that the others are extern "C++".

Note that the C++ Standard defines syntactically extern "anystring". It only give formal meanings to extern "C" and extern "C++". A compiler vendor is free to define extern "Pascal" or even extern "COM+" if they like.