C++ objects as parameters for interface methods

Question

For my C++ DLLs, I am using the factory pattern with abstract interfaces.
In the disadvantages section of this article, it says:

An abstract interface method cannot return or accept a regular C++ object as a parameter. It has be either a built-in type (like int, double, char*, etc.) or another abstract interface. It is the same limitation as for COM interfaces.

Could you elaborate what this means? What exactly can I not do and why?
Is there any further reading available on this matter?

Community · Accepted Answer · 2017-05-23 12:06:23Z

1

This statement does not look accurate. Abstract interface method can return or accept C++ class instance (or its pointer) as parameter. There is no COM-like limitation here. It might be unsafe though in case caller/callee are built using different compiler settings, alignments, using different allocators etc. in which case the same C++ class is defined slightly differently and the mismatch might result in unexpected behavior. That is, it is not about "cannot", it is about it might lead to unobvious problems.

A frequent example of the problem in question is passing CString as a parameter:

function in dll doesn't receive CString argument value

edited May 23, 2017 at 12:06

CommunityBot

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answered Apr 23, 2015 at 10:49

Roman Ryltsov

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