Undefined symbols when trying to use native C++ .so in Mono Pinvoke

Recently I have been trying to get some Point Cloud Library functionality going in my .NET framework application, and considering that there is no completely functional wrapper for PCL for C#, I made my own for a few functions as a test. Something like this:

[DllImport(DllFilePath, CallingConvention = CallingConvention.Cdecl)]
public extern static IntPtr StatisticalOutlierFilter(IntPtr data, int length, int meanK = 50, float mulThresh = 1.0f);

Which calls a function from a C++ library, such as this:

EXPORT VectorXYZ* StatisticalOutlierFilter(VectorXYZ* data, int length, int meanK, float mulThresh) {

    auto processedCloud = process.StatisticalOutlierFilter(data, length, meanK, mulThresh);
    auto processedVector = convert.ToVectorXYZ(processedCloud);

    return processedVector;
}

Where EXPORT is defined such for gcc:

#define EXPORT extern "C" __attribute__ ((visibility ("default")))

And relevant processing function from PCL is implemented such in a class (note that the returned is a boost shared pointer):

PointCloud<PointXYZ>::Ptr Processors::StatisticalOutlierFilter(VectorXYZ* data, int length, int meanK, float mulThresh) {

    auto cloud = PrepareCloud(data, length);
    PointCloud<PointXYZ>::Ptr cloud_filtered(new PointCloud<PointXYZ>);

    StatisticalOutlierRemoval<PointXYZ> sor;
    sor.setInputCloud(cloud);
    sor.setMeanK(meanK);
    sor.setStddevMulThresh(mulThresh);
    sor.filter(*cloud_filtered);

    return cloud_filtered;
}

This procedure works well with a dll built w/MSVC and running the whole thing on Windows, though the final target is gcc/Linux/Mono, where I get several errors of the following type (this is from mono debug):

'libavpcl_dll.so': '/usr/lib/libavpcl_dll.so: undefined symbol: _ZN3pcl7PCLBaseINS_8PointXYZEE13setInputCloudERKN5boost10shared_ptrIKNS_10PointCloudIS1_EEEE'.

I have investigated quite a bit so far, and have set my CmakeLists.txt to set(CMAKE_CXX_VISIBILITY_PRESET hidden) , therefore, I imagine, only functions I defined as EXPORT should be visible and imported - however, that is not the case, and I get the aforementioned errors. PCL was installed on Windows via vcpkg and on Xubuntu via apt. I am somewhat stumped as to what is the error source, considering the code runs well on windows, and builds without issue on Linux. Thanks.