On Wed, Apr 8, 2009 at 11:28 PM, Brent Arias wrote:

I've defined a class to use within shared memory, and I've decorated it with a Windows _declspec(export) to expose it from a DLL.  When I compiled with VC 2008, I got this warning:

Warning C4251: class 'boost::interprocess::vector' needs to have dll-interface to be used by clients of 'MyClass'

I searched boost user archives for any discussion of this, and in the context of boost.signals I've seen someone comment to simply disable the warning with:

#pragma warning (disable: 4251) Std::list talkers; #pragma warning (default: 4151)

Does this also apply to boost.interprocess?  Is it really safe to ignore this warning and continue to use the interprocess code from within a DLL?

Brent Arias

Brent - this warning applies because you've decorated the whole class with _declspec(dllexport). If you only decorate the public (and protected, I guess, taking inheritance into account) methods and data with _declspec(dllexport), those warnings will go away (unless they were originally being reported for public or protected data, of course). As an example: class A { public: _declspec(dllexport) A(); _declspec(dllexport) ~A(); _declspec(dllexport) A(const A&); _declspec(dllexport) A& operator=(const A&); _declspec(dllexport) size_t Count(std::list<int> const); private: std::list<int> l; }; Visual C++ is happy with that, but if I move the declspec onto the class, Visual C++ complains about the data member. Stuart Dootson