It is unwise to pass objects allocated in one framework over a DLL boundary to a different framework.
In the case of Using C dll in delphi return nothing, someone tries to pass an Interface to some memory in the C side over to Delphi.
Unless that interface is COM based, don’t do that!
In a more general way: don’t pass memory allocated on the DLL side over to the client side, no matter what kind of client you have.
From the DLL, either pass simple types, or fill buffers allocated at the client side.
Edit:
There was a nice Delphi DLL return string from C# … .NET 4.5 Heap Corruption but .NET 4.0 works? Explain please? – Stack Overflow question explaining in detail what to do for strings in a specific case: use the COM heap on the Delphi side using CoTaskMemAlloc (actually it uses the OLE task memory allocator as the Old New Thing explains).
–jeroen
via: Using C dll in delphi return nothing – Stack Overflow.
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