Cancelling _declspec(dllexport)

Just for simplification...

Code:

---

class _declspec(dllexport) Whatever
{
public:
    int some_func1 ();
    int some_func2 ();
    int some_func3 ();

    [...]

    int some_func20 ();

private:
    int some_var;
};

---

Using _declspec(dllexport) in the above way provides a convenient way to export all the functions in a class without needing to export them all individually but IIUC it exports everything - even some_var

Is there some convenient way to export a class's functions but to exclude its member variables?

From https://docs.microsoft.com/en-us/cpp...?view=msvc-160

it says that "all its member functions and static data members are exported". So from this I'd take it that non-static member variables wouldn't be exported ???

Ah, that might explain it.... In the actual code, the variable gets declared like this:-

Code:

---

static thread_local SharedPtr _tempo_map_p;

---

but apparently, a variable declared with thread_local isn't also allowed to have DLL linkage. I'll need to ask the original author if there's some reason why it needed to be static.

An interesting problem... apparently anything using thread_local can be declared as either static or extern - but if it's a class member, it's only allowed to be static - and if the class itself is _declspec(dllexport) this results in it getting exported. But the catch 22 is that anything declared as thread_local in a DLL, isn't allowed to be exported!!!

So AFAICT the only option is to declare all the class members individually using _declspec(dllexport) but exclude this one :cry:

Presumably... declaring the whole class as _declspec(dllexport) exports everything (even private members?) It'd be nice if there's some way to exclude specific members (e.g. the private ones).

Another idea... does VC++ support anonymous classes or structs (I've a feeling some compilers do). I'm just wondering if something like this could work...

Code:

---

class Whatever
{
protected:

    // These two wouldn't get exported
    static int some_var;
    int some_func1 ();

    class _declspec(dllexport) {
        public:

        // But these would get exported as members of class Whatever
        int some_func2 ();
        int some_func3 ();
    }
};

---

Have you tried it? I haven't done it this way before - but I gave up with .dlls some years ago!

PS. This compiles but with a warning re non-standard extension re nameless struct/union

Code:

---

class Whatever
{
public:

        // These two wouldn't get exported
        static int some_var;
        int some_func1() { return 1; }

        class _declspec(dllexport) {
        public:

                // But these would get exported as members of  class Whatever
                int some_func2() { return 2; }
                int some_func3() { return 3; }
        };
};

int main()
{
        Whatever w;

        w.some_func1();
        //w.some_func2(); // Error - Not a member
}

---

This compiles OK:

Code:

---

class Whatever
{
public:

        // These two wouldn't get exported
        static int some_var;
        int some_func1() { return 1; }

        class _declspec(dllexport) {
        public:

                // But these would get exported as members of  class Whatever
                int some_func2() { return 2; }
                int some_func3() { return 3; }
        }exp;
};

int main()
{
        Whatever w;

        w.some_func1();
        w.exp.some_func2();
}

---

Many thanks 2kaud - I'm just shutting down for the night but I'll give that a try tomorrow!

Yes you're right - the anonymous class needs to be instantiated, rather than just declared... how annoying!!

I don't know if their posts are public or private but I've flagged this up on the Microsoft Developer forum to see if they've got any ideas.

BTW - in a situation like this...

Code:

---

class Whatever
{
public:
        __declspec(dllexport) Whatever();
        __declspec(dllexport) ~Whatever();

        __declspec(dllexport) int some_func1();
};

---

Is it strictly necessary to export the destructor (given that the user's code can't call it) ?