具有内部链接的命名命名空间

Question

[@PasserBy has found that my question is a duplicate. The question can be closed, thanks.]

How can I get a named namespace with internal linkage? That is, how can I get a named namespace invisible to external source files? I want this:

static namespace N {
    int foo() {return 10;}
    int bar() {return 20;}
}

However, unfortunately, C++ does not recognize static namespace .

Answer 1

Enclose the named namespace within an unnamed namespace:

namespace {
    namespace N {
        int foo() {return 10;}
        int bar() {return 20;}
    }
}

int sum()
{
    return N::foo() + N::bar();
}

This works because an unnamed namespace automatically exports its members (the sole member in this case being the namespace N ) to the surrounding scope—without exposing the members to other source files.