Add PCL_UNUSED to fix doxygen warnings

[aPonza]

Fixes warning: argument <arg> of command @param is not found in the argument list of <function>

If this seems reasonable I'll follow up with a PR aiming at using this macro instead of all the naked (void) casts.

[kunaltyagi]

If we could make this optional (eg: for OMP thread number), that would be heaven

[SergioRAgostinho]

My eyes are struggling to mentally compile this expression.

[SergioRAgostinho]

By the way this PR introduced warnings in 18.04, g++ 7.5.0

[ 42%] Building CXX object tools/CMakeFiles/pcl_plane_projection.dir/plane_projection.cpp.o                                                         
In file included from /home/sergio/Development/3rdparty/pcl/filters/include/pcl/filters/normal_refinement.h:40:0,          
                 from /home/sergio/Development/3rdparty/pcl/filters/include/pcl/filters/impl/normal_refinement.hpp:44,              
                 from /home/sergio/Development/3rdparty/pcl/filters/src/normal_refinement.cpp:39:                                   
/home/sergio/Development/3rdparty/pcl/filters/include/pcl/filters/normal_refinement.h: In instantiation of ‘std::vector<float> pcl::assignNormalWeights(const pcl::PointCloud<PointT>&, int, const
 std::vector<int>&, const std::vector<float>&) [with NormalT = pcl::Normal]’:                                                                                                                     
/home/sergio/Development/3rdparty/pcl/filters/include/pcl/filters/normal_refinement.h:102:60:   required from ‘bool pcl::refineNormal(const pcl::PointCloud<PointT>&, int, const std::vector<int>&
, const std::vector<float>&, NormalT&) [with NormalT = pcl::Normal]’                                                                                                                              
/home/sergio/Development/3rdparty/pcl/filters/include/pcl/filters/impl/normal_refinement.hpp:94:24:   required from ‘void pcl::NormalRefinement<NormalT>::applyFilter(pcl::NormalRefinement<Normal
T>::PointCloud&) [with NormalT = pcl::Normal; pcl::NormalRefinement<NormalT>::PointCloud = pcl::PointCloud<pcl::Normal>]’                                                                         
/home/sergio/Development/3rdparty/pcl/filters/src/normal_refinement.cpp:45:3:   required from here                                         
/home/sergio/Development/3rdparty/pcl/common/include/pcl/pcl_macros.h:133:46: warning: left operand of comma operator has no effect [-Wunused-value]
 #define PCL_UNUSED(x) ((void)(true ? 0 : ((x), void(), 0)))                                                                                        
                                           ~~~^~~~~~~~                                                   
/home/sergio/Development/3rdparty/pcl/filters/include/pcl/filters/normal_refinement.h:60:5: note: in expansion of macro ‘PCL_UNUSED’
     PCL_UNUSED(cloud);                                                                                                             
     ^                                                                                          
/home/sergio/Development/3rdparty/pcl/common/include/pcl/pcl_macros.h:133:46: warning: left operand of comma operator has no effect [-Wunused-value]
 #define PCL_UNUSED(x) ((void)(true ? 0 : ((x), void(), 0)))
                                           ~~~^~~~~~~~
/home/sergio/Development/3rdparty/pcl/filters/include/pcl/filters/normal_refinement.h:61:5: note: in expansion of macro ‘PCL_UNUSED’
     PCL_UNUSED(index);

[aPonza]

This actually didn't work for:

• GCC (both 5.5.0, and 9.2.1)

In file included from /__w/1/s/filters/include/pcl/filters/normal_refinement.h:40:0,
                 from /__w/1/s/filters/include/pcl/filters/impl/normal_refinement.hpp:44,
                 from /__w/1/s/filters/src/normal_refinement.cpp:39:
/__w/1/s/filters/include/pcl/filters/normal_refinement.h: In instantiation of 'std::vector<float> pcl::assignNormalWeights(const pcl::PointCloud<PointT>&, int, const std::vector<int>&, const std::vector<float>&) [with NormalT = pcl::Normal]':
/__w/1/s/filters/include/pcl/filters/normal_refinement.h:102:60:   required from 'bool pcl::refineNormal(const pcl::PointCloud<PointT>&, int, const std::vector<int>&, const std::vector<float>&, NormalT&) [with NormalT = pcl::Normal]'
/__w/1/s/filters/include/pcl/filters/impl/normal_refinement.hpp:94:24:   required from 'void pcl::NormalRefinement<NormalT>::applyFilter(pcl::NormalRefinement<NormalT>::PointCloud&) [with NormalT = pcl::Normal; pcl::NormalRefinement<NormalT>::PointCloud = pcl::PointCloud<pcl::Normal>]'
/__w/1/s/filters/src/normal_refinement.cpp:45:3:   required from here
/__w/1/s/common/include/pcl/pcl_macros.h:133:46: warning: left operand of comma operator has no effect [-Wunused-value]
 #define PCL_UNUSED(x) ((void)(true ? 0 : ((x), void(), 0)))
                                              ^
/__w/1/s/filters/include/pcl/filters/normal_refinement.h:60:5: note: in expansion of macro 'PCL_UNUSED'
     PCL_UNUSED(cloud);
     ^
/__w/1/s/common/include/pcl/pcl_macros.h:133:23: warning: left operand of comma operator has no effect [-Wunused-value]
 #define PCL_UNUSED(x) ((void)(true ? 0 : ((x), void(), 0)))
                       ^
/__w/1/s/filters/include/pcl/filters/normal_refinement.h:61:5: note: in expansion of macro 'PCL_UNUSED'
     PCL_UNUSED(index);
     ^

(link)

• XCode

In file included from /Users/runner/runners/2.166.2/work/1/s/filters/src/normal_refinement.cpp:39:
In file included from /Users/runner/runners/2.166.2/work/1/s/filters/include/pcl/filters/impl/normal_refinement.hpp:44:
/Users/runner/runners/2.166.2/work/1/s/filters/include/pcl/filters/normal_refinement.h:61:16: warning: expression result unused [-Wunused-value]
    PCL_UNUSED(index);
               ^~~~~
/Users/runner/runners/2.166.2/work/1/s/common/include/pcl/pcl_macros.h:133:44: note: expanded from macro 'PCL_UNUSED'
#define PCL_UNUSED(x) ((void)(true ? 0 : ((x), void(), 0)))
                                           ^

(link)

But it was perfect for Doxygen and MSVC. Maybe for the rest (void)x will do since it's in place everywhere else in the library. This really should've been a draft PR.

[aPonza]

Didn't update the page so I didn't see your message.

Anyways coliru seems ok with clang and gcc, and godbolt likes the MSVC version. I don't have anything online to test XCode, so I'll check that Doxygen doesn't complain and push the fix.