C++: what is the proper way of declaring function prototype in anonymous namespace?

Question

If I declare it in .h in obvious way:

namespace <named_namespace> {
    namespace {
        …
        <type> <function>(<parameters>);
        …
    }
}

and put its implementation in .cpp, a compilation error will occur:

'<type> <named_namespace>::{anonymous}::<function>(<parameters>)' should have been declared inside <named_namespace>

Is it possible to avoid this error without putting the function's implementation in the single file? Currently I use keyword static instead, but it produces multiply annoying warnings:

'<type> <named_namespace>::<function>(<parameters>)' declared 'static' but never defined

which, as I've understood, can be disabled only by keeping function in a single file (header or source).

Cross-compiler solution is welcome (if any).

Or maybe splitting the header file into 'public' and 'private' parts is more efficient?

Answer 1

You cannot have anonymous namespace that works across translation units therefore putting anonymous namespace in .h won't work as you expect. In each translation unit (.cpp), that namespace is assigned a different, unique name.

Separated declaration and definition is possible but only inside that namespace:

namespace {
    void func();
}

…

namespace {
    void func()
    {
        …
    }
}