[fpc-pascal] How to call C++ function with Vector

Marco van de Voort marcov at stack.nl
Tue Sep 26 12:49:47 CEST 2017

In our previous episode, Dennis said:
> I have a windows 32-bit dll written in C++ (probably C++ Builder).
> It has 1 function which I need to call:
> int SPAPI_GetProduct(vector<SPApiProduct>& apiProdList)
> I am stuck at the keyword vector.

It is not a keyword it is a generic type. So that is not easy, specially
since C++ and Pascal classes differ.

And even if the call succeeds, getting results from apiprodlist is major
problem number two.

You can try to match the C++ code with carefully crafted pascal code, but
that requires knowledge about implementation details of the C++

I avoided that way (as too complicated and too fragile), but Rudy Velthuis
has an article on it (C++ <-> Delphi)

I myself generally solve this with a wrapper DLL, by crafting a DLL in C++
that exports a C (not C++) interface, and then use that. The same method as
QT is used from Lazarus (via wrapper dll/.so qtpas)

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