Make OpenMP available in downstream projects (#5744)

* Make OpenMP available in downstream projects
Previously, if a downstream project used PCL_NO_PRECOMPILE or if it used a PCL class which includes OpenMP code, but PCL does not make an instantiation of that class, OpenMP was not available.
In other words, when PCL code using OpenMP was compiled when building PCL, OpenMP was available. However when PCL code using OpenMP was compiled in the downstream/user project (e.g. in the two mentioned cases), OpenMP was not available.
The fix is to search for OpenMP again in PCLConfig.cmake

* OpenMP as dep for more modules

Author: mvieth

PCLConfig.cmake.in

@@ -303,6 +303,11 @@ function(find_external_library _component _lib _is_optional)
     find_package(Pcap)
   elseif("${_lib}" STREQUAL "png")
     find_package(PNG)
+  elseif("${_lib}" STREQUAL "OpenMP")
+    find_package(OpenMP COMPONENTS CXX)
+    # the previous find_package call sets OpenMP_CXX_LIBRARIES, but not OPENMP_LIBRARIES, which is used further down
+    # we can link to the CMake target OpenMP::OpenMP_CXX by setting the following:
+    set(OPENMP_LIBRARIES OpenMP::OpenMP_CXX)
   else()
     message(WARNING "${_lib} is not handled by find_external_library")
   endif()

features/CMakeLists.txt

@@ -4,7 +4,7 @@ set(SUBSYS_DEPS common search kdtree octree filters 2d)
 
 set(build TRUE)
 PCL_SUBSYS_OPTION(build "${SUBSYS_NAME}" "${SUBSYS_DESC}" ON)
-PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS})
+PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS} OPT_DEPS OpenMP)
 
 PCL_ADD_DOC("${SUBSYS_NAME}")
 

filters/CMakeLists.txt

@@ -4,7 +4,7 @@ set(SUBSYS_DEPS common sample_consensus search kdtree octree)
 
 set(build TRUE)
 PCL_SUBSYS_OPTION(build "${SUBSYS_NAME}" "${SUBSYS_DESC}" ON)
-PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS})
+PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS} OPT_DEPS OpenMP)
 
 PCL_ADD_DOC("${SUBSYS_NAME}")
 

io/CMakeLists.txt

@@ -6,9 +6,9 @@ set(SUBSYS_EXT_DEPS boost eigen)
 set(build TRUE)
 PCL_SUBSYS_OPTION(build "${SUBSYS_NAME}" "${SUBSYS_DESC}" ON)
 if(WIN32)
-  PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS} OPT_DEPS openni openni2 ensenso davidSDK dssdk rssdk rssdk2 pcap png vtk EXT_DEPS ${SUBSYS_EXT_DEPS})
+  PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS} OPT_DEPS openni openni2 ensenso davidSDK dssdk rssdk rssdk2 pcap png vtk OpenMP EXT_DEPS ${SUBSYS_EXT_DEPS})
 else()
-  PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS} OPT_DEPS openni openni2 ensenso davidSDK dssdk pcap png vtk libusb EXT_DEPS ${SUBSYS_EXT_DEPS})
+  PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS} OPT_DEPS openni openni2 ensenso davidSDK dssdk pcap png vtk libusb OpenMP EXT_DEPS ${SUBSYS_EXT_DEPS})
 endif()
 
 PCL_ADD_DOC("${SUBSYS_NAME}")

keypoints/CMakeLists.txt

@@ -4,7 +4,7 @@ set(SUBSYS_DEPS common search kdtree octree features filters)
 
 set(build TRUE)
 PCL_SUBSYS_OPTION(build "${SUBSYS_NAME}" "${SUBSYS_DESC}" ON)
-PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS})
+PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS} OPT_DEPS OpenMP)
 
 PCL_ADD_DOC("${SUBSYS_NAME}")
 

registration/CMakeLists.txt

@@ -4,7 +4,7 @@ set(SUBSYS_DEPS common octree kdtree search sample_consensus features filters)
 
 set(build TRUE)
 PCL_SUBSYS_OPTION(build "${SUBSYS_NAME}" "${SUBSYS_DESC}" ON)
-PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS})
+PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS} OPT_DEPS OpenMP)
 
 PCL_ADD_DOC("${SUBSYS_NAME}")
 

segmentation/CMakeLists.txt

@@ -4,7 +4,7 @@ set(SUBSYS_DEPS common geometry search sample_consensus kdtree octree features f
 
 set(build TRUE)
 PCL_SUBSYS_OPTION(build "${SUBSYS_NAME}" "${SUBSYS_DESC}" ON)
-PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS})
+PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS} OPT_DEPS OpenMP)
 
 PCL_ADD_DOC("${SUBSYS_NAME}")
 

surface/CMakeLists.txt

@@ -4,7 +4,7 @@ set(SUBSYS_DEPS common search kdtree octree)
 
 set(build TRUE)
 PCL_SUBSYS_OPTION(build "${SUBSYS_NAME}" "${SUBSYS_DESC}" ON)
-PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS} OPT_DEPS qhull vtk)
+PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS} OPT_DEPS qhull vtk OpenMP)
 
 PCL_ADD_DOC("${SUBSYS_NAME}")
 

tracking/CMakeLists.txt

@@ -4,7 +4,7 @@ set(SUBSYS_DEPS common search kdtree filters octree)
 
 set(build TRUE)
 PCL_SUBSYS_OPTION(build "${SUBSYS_NAME}" "${SUBSYS_DESC}" ON)
-PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS})
+PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS} OPT_DEPS OpenMP)
 
 PCL_ADD_DOC("${SUBSYS_NAME}")