Home/ Questions/Q 694579
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-14T02:52:16+00:00

I followed an excellent article by Rudy Velthuis about using C++ classes in DLL’s.

  • 0

I followed an excellent article by Rudy Velthuis about using C++ classes in DLL’s. Everything was golden, except that I need access to some classes that do not have corresponding factories in the C++ DLL. How can I construct an instance of a class in the DLL? The classes in question are defined as 

class __declspec(dllexport) exampleClass
{
public:
  void foo();
};

Now without a factory, I have no clear way of instantiating the class, but I know it can be done, as I have seen SWIG scripts (.i files) that make these classes available to Python. If Python&SWIG can do it, then I presume/hope there is some way to make it happen in Delphi too.

Now I don’t know much about SWIG, but it seems like it generates some sort of map for C++ mangled names? Is that anywhere near right? Looking at the exports from the DLL, I suppose I could access functions & constructor/destructor by index or the mangled name directly, but that would be nasty; and would it even work? Even if I can call the constructor, how can I do the equivalent of “new CClass();” in Delphi?

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    The correct way to do it is to write a wrapper DLL that exposes a factory for the class you need.

    I am not sure hiw SWIG works, but anything that relies on reverse-engineering the name mangling seems a dubious approach.

    Besides a C++ object should be created only in C++ code. You ought to leave the object creation semantics to the C++ runtime.

    There is a reason why COM exists. Precisely to make this cross language object metaphor work neatly.

    I’ve written scores of COM objects that are called from Delphi, python and C#

    • 0