How Do I Properly Define COMPILING_DLL for DLLEXPORT/DLLIMPORT Macros?

Macro for dllexport/dllimport Switch

The provided code snippet defines the macro DLLEXPORT to add the dllexport or dllimport attribute to functions based on the value of the COMPILING_DLL macro. However, the question remains: how and where should COMPILING_DLL be defined?

Defining COMPILING_DLL

One option is to use the default defined macro local to the project. These macros can be found in Properties -> C/C -> Preprocessor -> Preprocessor Definition.

For example, if your project is named MyDLL, the default macro is MYDLL_EXPORTS. You can use this macro as follows:

#ifdef MYDLL_EXPORTS
    #define DLLEXPORT __declspec(dllexport)
#else
    #define DLLEXPORT __declspec(dllimport)
#endif

When compiling the DLL project, MYDLL_EXPORTS will be defined, enabling DLLEXPORT as "export". When using the DLL in client code, MYDLL_EXPORTS will not be defined, enabling DLLEXPORT as "import".

This approach allows you to use the same header for both compiling the DLL and using it in client code.

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