Passing non-primitive types fron Rhino C++ plugin to C++ DLL

Rhino Developer
1

Hi,

I’m calling my own C++ DLL from my C++ Rhino plugin. Both are two projects of the same solution. I’m using VS2020 with /std:c++17.

I cannot pass non-primitive types. For example, I can pass a char* correctly but when I try to pass a string I get a NULL string. Analogous for containers and my own classes.

When I call the DLL from a plain C++ test program it works correctly, so I assume it is not a problem of C/C++ linkage.

Is there any limitation or known problem?

Thanks in advance,
Jordi Duran

2

What kind of string and how are you passing it from your plug-in to your DLL?

Sample code can be helpful…

— Dale

3

Hi Dale,

Thanks a lot for your reply. I prepared a very simple test case. I’m taking the example plugin created by the wizard and I’m adding a very simple call to a DLL function:

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The DLL gets the int, float and char* parameteers but does not receive the std::vector and std::string parameters:
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Regards,
Jordi Duran

4

Two things:

Can you share the header of the function you’re calling from the plug-in?
Can you try passing the vector and the string by reference? You’re currently passing by value, and although that should work it is not necessary.

5

Hi @jordi,

You should google “C++ pass std::string to DLL”, as there is a lot written about this.

In the case of a string, I would pass a const char* (or const wchar_t*) and do the conversion to std::string on the other side of the interface, within the DLL.

– Dale

6

Thanks Dale,

I wanted to avoid the conversions but I see the best way is to use primitive types unless you build your program and your DLL at the same time (tightly coupled).

Jordi

7

Hi Menno,

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Passing the vector and the string by reference does not change the behavior. I found a good answer, following Dale’s suggestion, at:

Thanks a lot for your answer,
Jordi Duran