How to get rid of warning LNK4006 when not using templates?

Question

I know the question is not very descriptive but I couldn't phrase it better.

I'm trying to compile a static linked library that has several objects, all the objects contain the following:

#include foo.h

foo.h is something along these lines:

#pragma once
template<class T>
class DataT{
    private:
        T m_v;
    public:
        DataT(T v) : m_v(v){}
};

typedef DataT<double> Data;

Now, everything works fine, but if I change DataT to be just Data with double instead of T, I will get a LNK4006 warning at linking time for each .obj stating that the .ctor was already defined.

Edit 1:

#pragma once

class Data{
    private:
        double m_v;
    public:
        Data(double v) : m_v(v){}
};

Edit 2: I'm using MSVC7. The .ctor is actually included in both cases as in

...
public:
   Data(double v);

#include foo.inl
...
//foo.inl
Data::Data(double v): m_v(v) {}

What I'm trying to accomplish though, is not to have that compiled but as a header the user can use.

Answer 1

If you put the constructor definition in foo.cpp instead of foo.h it will not be compiled separately into every translation unit. At the moment a copy of the constructor is compiled into every object the contains the foo.h include.

The other possible solution would be to the get the compiler to inline the constructor. have you disabled inlining in the compiler settings? The constructor looks easy enough to get automatically inlined.

Answer 2

I'm not sure what you're trying to do in the example for edit #2, but I think it might help if you have the following in foo.inl:

inline
Data::Data(double v): m_v(v) {}

If the contents of foo.inl is also being included in something where the inline keyword won't work or shouldn't be, you can probably use the preprocessor to handle the difference by using a macro that expands to nothing or inline as appropriate.