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Getting rid of dllimport warning messages for template classes

Posted on 2004-08-20
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Last Modified: 2010-04-01
Hi,

I'm tired of stuff like this:

// File: foo.h

class __declspec(dllimport) foo
{
  int x;
  vector<int> xs;
};

When including foo.h you will get a bunch of warnings about vector<> (or it's allocator) not being dllexported:

c:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\vector(35) : warning C4251: 'std::_Vector_val<_Ty,_Alloc>::_Alval' : class 'std::allocator<_Ty>' needs to have dll-interface to be used by clients of class 'std::_Vector_val<_Ty,_Alloc>'

Of course, vector isn't dllexported because it is a template class, and its implementation is entirely contained within the relevant header files.  Is there some way to avoid these warning?

Unacceptable solutions are:

(1) using #pragma warning(disable: xxxx) or similar to simply surpress the errors
(2) changing any of the standard header files
(3) Changing the dllexport nature of the client class (foo), for example by only exporting specific functions



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Question by:travd
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jkr earned 250 total points
ID: 11857349
As I just posted the same in another Q: Check out http://support.microsoft.com/default.aspx?scid=kb;en-us;168958 ("How To Exporting STL Components Inside & Outside of a Class") and http://support.microsoft.com/default.aspx?scid=kb;en-us;172396 ("PRB: Access Violation When Accessing STL Object in DLL")

Templates and DLLs can cause problems if you do not offer proper access (via e.g interfaces) to these objects, which better only "live" inside the modukes they're created in.
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