Exporting global const variable from a DLL

Question

The following is a simplified version of the code I am using with the Qt framework:

foo.h:

// Defines DLL import or export as required
#if defined(REGEXUTIL_LIBRARY)
  #define LIBRARY_EXPORT Q_DECL_EXPORT
#else
  #define LIBRARY_EXPORT Q_DECL_IMPORT
#endif

LIBRARY_EXPORT extern const QString testString;

foo.cpp:

#include "foo.h"
LIBRARY_EXPORT const QString testString = "Test string";

test.cpp, in module which imports this DLL:

const QString s = testString;

I know both the DLL and the test compile and link correctly since the above works with a non-const QString. However, when I make the QString const I get an unresolved external symbol error upon compiling the test, which I am assuming is to do with the fact that the const variable is not initialised in the header file. If I do initialise it there, I get errors about the DLL import prefix not being allowed when I attempt to compile the test.

What is the correct way to fix this error? I want to be able to access the const QString variables from modules which import this DLL.

Answer 1

If solution of const string being defined in header is acceptable to you, there is no need to import the symbol at all:

//foo.h
static const QString testString = "Test string";

should be enough - testString can be accessed both in modules importing the dll and inside the dll itself.