Question

I am planning to use libraries in my C++ program. Development is happening on Linux but application is designed to compile on both Linux and Windows. I understand direct equivalent for shared libraries(.so) in windows is DLL, right?

In Linux using g++, I can create shared library using -fPIC and -shared flags. AFAIK, there is no other code change required for a shared library. But things are different in a Windows DLL. There I should specify the functions which have to be exported using dllexport, right?

My question is how do I manage this situation? I mean dllexport is invalid in Linux and the compiler will give an error. But it is required in Windows. So how do I write a function which will compile on both platforms without any code change?

Compilers used

• g++ – LINUX
• VC++ – Windows

Any help would be great!

Answer 1

We specify __declspec(dllexport) for class:

#define EXPORT_XX __declspec(dllexport)

class EXPORT_XX A
{
};

You can then check for platform and only define the macro on windows. E.g.:

#ifdef WIN32
#define EXPORT_XX __declspec(dllexport)
#else
#define EXPORT_XX
#endif

We mostly build static libraries so there might be more stuff to do for dynamic libs but the concept is the same – use preprocessor macro to define string that you need to insert into Windows code.