[fpc-pascal] How do I pass a call back Class and its method to an external library *.so file writting in C++

[Dennis]

>
>
>     I am expected to create and pass an instance of such class
>     ApiProxyWrapperReply in my calling program
>       via a function
>     void SPAPI_RegisterApiProxyWrapperReply(ApiProxyWrapperReply*
>     apiProxyWrapperReply);
>
>     and the external library will then call the various methods of
>     ApiProxyWrapperReply  as 'call-back' functions when needed.
>
>
> Considering that the class only has abstract virtual methods and the 
> destructor is non-virtual you *might* be able to do this by declaring 
> a raw interface ({$Interfaces Corba}) and declaring all the virtual 
> methods in the same order (very important!) with suitable signatures 
> and calling convention (for i386 you should pick cppdecl otherwise the 
> system default should be alright), implementing that interface in some 
> Object Pascal class and then passing an instance of that interface to 
> the library.
>
> It could still go wrong due to some differences in the ABI, but it 
> might just as well work. 🤷‍♀️
>
In C++, I was expected to pass the class instance to the external 
library. So, In Pascal, do I pass the interface variable to the external 
library?

Thanks a lot.

Dennis Poon
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