C++ and C# PInvoke Mac

Petras1 · July 9, 2021, 12:19pm

I am trying to run .dylib library of mac in c# of mac.

It is all new for me and I know this website Interop with Native Libraries | Mono
and also mcneel guide.

In windows C++ I always decorate PInvoke methods with

extern "C"{
__declspec(dllexport) void MethodName()
}

Is there any alternative in Mac for __declspec(dllexport) decoration, since this wont build on mac?

nathanletwory · July 9, 2021, 1:40pm

I decorate my function declarations with defines that are controlled by the build system

github.com

mcneel/CCSycles/blob/ccd94af323894db3b265a469042c5c88caf05209/ccycles/ccycles.h#L20

    
      
          Unless required by applicable law or agreed to in writing, software
          distributed under the License is distributed on an "AS IS" BASIS,
          WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
          See the License for the specific language governing permissions and
          limitations under the License.
          **/
          
          
#ifndef __CYCLES__H__
          #define __CYCLES__H__
          
          
#ifdef WIN32
          #ifdef CCL_CAPI_DLL
          #define CCL_CAPI __declspec (dllexport)
          #else
          #define CCL_CAPI __declspec (dllimport)
          #endif
          #else
          #define CCL_CAPI
          #endif
          /*

Then the initialization function looks like this

github.com

mcneel/CCSycles/blob/ccd94af323894db3b265a469042c5c88caf05209/ccycles/ccycles.h#L124

    
      
          * Set update function to CCycles using cycles_session_set_display_update_callback
          * \ingroup ccycles ccycles_session
          */
          typedef void(__cdecl *DISPLAY_UPDATE_CB)(unsigned int session_id, unsigned int sample);
          
          

          
/**
          * Initialise Cycles by querying available devices.
          * \ingroup ccycles
          */
          CCL_CAPI void __cdecl cycles_initialise(unsigned int mask = ccl::DEVICE_MASK_ALL);
          
          
/**
          * Initialise paths for Cycles to look in (pre-compiled kernels, cached kernels, kernel code)
          * \ingroup ccycles
          */
          CCL_CAPI void __cdecl cycles_path_init(const char* path, const char* user_path);
          
          
/**
          * Set an environment variable for Cycles
          * \ingroup ccycles

With implementation

github.com

mcneel/CCSycles/blob/ccd94af323894db3b265a469042c5c88caf05209/ccycles/ccycles.cpp#L64

    
      
          
          
void cycles_putenv(const char* var, const char* val)
          {
          #if defined(_WIN32)
          	_putenv_s(var, val);
          #else
          	setenv(var, val, 1);
          #endif
          }
          
          
void cycles_initialise(unsigned int mask)
          {
          	if (!initialised) {
          		devices.clear();
          		multi_devices.clear();
          		devices = ccl::Device::available_devices(mask);
          		initialised = true;
          	}
          }
          
          
void cycles_debug_set_cpu_kernel(unsigned int state)

Petras1 · July 9, 2021, 4:22pm

Hi,

Thanks for the answer. It seems the answer to my question is true, I can use this PInvoke method.
I managed to compile .dylib on Mac and call in C# ConsoleApp in VisualStudio mac by:

C++ Side:


.hpp:
#define PINVOKE extern "C"
PINVOKE int test (int n);

.cpp:
PINVOKE int test (int n){
return n*n;
}

and C#

[DllImport("libsimpleDYLIB.dylib")]
private static extern int test (int n);

I am super suspicious why it is so simple. I did not even had to change anything in default Mac Visual Studio configuration.

@nathanletwory
Is there also a possibility to compile Grasshopper components in Mac Visual Studio?
Or RhinoCommands ? Since it is not a .NET framework
Are there any samples?

dale · July 9, 2021, 4:26pm

This guide might (also) be worth your time.

– Dale

Petras1 · July 9, 2021, 4:35pm

Thanks @Dale, I think I will use your documentation since I will get more into Mac development.
I see that you made a tutorial for a Command Line, and do you also have for Grasshopper? Or it is not possible due to .NET?

dale · July 9, 2021, 6:41pm

Both RhinoCommon plug-ins and Grasshopper plug-ins are just .NET assemblies. So the guide (above) should work to build Grasshopper components that call into unmanaged libraries.