Support Vector Machine link error

Hi Developers,

I have worked a bit an SVM classifier test with PCL and I have few issues.
The svm_wrapper gives me an error to link dlls in visual studio.
Here link error is reported.

Your Environment

• Operating System and version: Windows 10
• Compiler: Visual Studio 2012
• PCL Version: trunk

Expected Behavior

NO link errors

Current Behavior

there is a link error when I try to build any object from the SMV class in visual studio
in file svm_wrapper.h

No link error anymore

Possible Solution

I don't know if it is correct, but I have solved in my local code using PCL_EXPORTS in the following lines:

- class SVM
+class PCL_EXPORTS SVM

-  class SVMTrain : public SVM
+  class PCL_EXPORTS SVMTrain : public SVM

-  class SVMClassify : public SVM
+  class PCL_EXPORTS SVMClassify : public SVM

the same happen with functions called in svm.h

so here is my code to fix

+#ifdef __cplusplus
+extern "C"
+{
+#if (defined WIN32 || defined _WIN32 || defined WINCE) 
+    #define SVMLIB_EXPORTS __declspec(dllexport)
+#else
+    #define SVMLIB_EXPORTS
+#endif
+
+#endif


+  SVMLIB_EXPORTS int svm_get_nr_class (const struct svm_model *model);
+  SVMLIB_EXPORTS void svm_get_labels (const struct svm_model *model, int *label);

+  SVMLIB_EXPORTS void svm_free_model_content (struct svm_model *model_ptr);
+  SVMLIB_EXPORTS void svm_free_and_destroy_model (struct svm_model **model_ptr_ptr);
+  SVMLIB_EXPORTS void svm_destroy_param (struct svm_parameter *param);

Code to Reproduce

if you want to reproduce my error you can use the following code:
cmakelists.txt

cmake_minimum_required (VERSION 2.8 FATAL_ERROR)

project(pcl_SVM_PCD_test)

find_package (PCL 1.8 REQUIRED)

include_directories (${PCL_INCLUDE_DIRS})
include_directories (${CMAKE_BINARY_DIR})
link_directories    (${PCL_LIBRARY_DIRS})
add_definitions     (${PCL_DEFINITIONS})

add_executable  (pcl_SVM_PCD_test pcl_SVM_PCD_test.cpp)

target_link_libraries (pcl_SVM_PCD_test ${PCL_LIBRARIES} )

pcl_SVM_PCD_test.cpp

#include <pcl/ml/svm_wrapper.h>

int main (int argc, char** argv)
{
  // Only create objects to use the classifier

    pcl::SVMTrain my_svm_trainer; //--> our trainer, to be used for store training data or for a new training procedure
    pcl::SVMClassify my_svm_classifier;  //--> our classifier
    pcl::SVMModel my_svm_model;   //--> classifier model, this is automatically generated after the training or loaded for the classification
    pcl::SVMParam my_svm_parameters; //--> our own configuration parameters


 return (0);
}

COMPILER ANSWER :

1>------ Build started: Project: ZERO_CHECK, Configuration: Release x64 ------
1>  Checking Build System
1>  CMake does not need to re-run because C:/code/prova2/build/CMakeFiles/generate.stamp is up-to-date.
2>------ Build started: Project: pcl_SVM_PCD_test, Configuration: Release x64 ------
2>  Building Custom Rule C:/code/prova2/CMakeLists.txt
2>  CMake does not need to re-run because C:\code\prova2\build\CMakeFiles\generate.stamp is up-to-date.
2>  pcl_SVM_PCD_test.cpp
2>pcl_SVM_PCD_test.obj : error LNK2019: unresolved external symbol svm_free_model_content referenced in function "public: __cdecl pcl::SVMClassify::~SVMClassify(void)" (??1SVMClassify@pcl@@QEAA@XZ)
2>pcl_SVM_PCD_test.obj : error LNK2019: unresolved external symbol svm_destroy_param referenced in function "public: __cdecl pcl::SVM::~SVM(void)" (??1SVM@pcl@@QEAA@XZ)
2>pcl_SVM_PCD_test.obj : error LNK2019: unresolved external symbol svm_set_print_string_function referenced in function "public: __cdecl pcl::SVMTrain::SVMTrain(void)" (??0SVMTrain@pcl@@QEAA@XZ)
2>C:\code\prova2\build\Release\pcl_SVM_PCD_test.exe : fatal error LNK1120: 3 unresolved externals
========== Build: 1 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Context

Build a machine learning algorithm based on the SVM classifier.
On my local code I have made few modifications, I can commit the changes in a branch and then check/pull if you are interested.
I have prepared a tutorial on how to classify point clouds, just in case.

Start by building the supplied CMakeLists.txt and pcl_SVM_PCD_test.cpp reproduction on Windows, then inspect pcl/ml/svm_wrapper.h and the related svm.h declarations. Compare the unresolved symbols with the linked PCL libraries and the reported export changes. Done means the sample links successfully without unresolved SVM symbols.