How to pass a class by (const) reference to C++

[Tim]

On Wednesday, 15 December 2021 at 15:20:18 UTC, Jan wrote:
> As I was told linking against functions in DLLs works 
> perfectly, because it is identical to static linking. Linking 
> against global/static variables supposedly differs and that's 
> not handled correctly for DLLs. As I said, I talked to someone 
> who worked on fixing lots of those issues a while ago and he 
> immediately knew about this limitation.

I have used global variables from DLLs successfully. DMD now also 
has a test for C++ DLLs: 
https://github.com/dlang/dmd/blob/master/test/dshell/extra-files/dll_cxx/testdll.d

The variable should be declared like this in C++:
__declspec(dllexport) int value;

It can then be accessed from D with this:
extern (C++) export extern __gshared int value;

Do you have a test case for your problem?