Use imported targets for linking to CUDA

This retains the desirable quality of not including paths to CUDA libraries
from the build system into the config files, and has two major advantages:

* It removes the need to use link_directories, which doesn't guarantee that
  the libraries from the supplied directory will be used (there may be
  libraries with the same names earlier in the search path).

* It removes the need to put -L entries into OPENCV_LINKER_LIBS. This variable
  is used with target_link_libraries, where such entries are treated as linker
  flags, so doing this is unportable. I remove the support for -L entries
  from OpenCVGenPkgconfig.cmake, as well, to discourage adding them in the
  future.

CMakeLists.txt

@@ -540,9 +540,6 @@ if(HAVE_CUDA AND NOT ENABLE_DYNAMIC_CUDA)
   if(HAVE_CUFFT)
     set(OPENCV_LINKER_LIBS ${OPENCV_LINKER_LIBS} ${CUDA_cufft_LIBRARY})
   endif()
-  foreach(p ${CUDA_LIBS_PATH})
-    set(OPENCV_LINKER_LIBS ${OPENCV_LINKER_LIBS} -L${p})
-  endforeach()
 endif()
 
 # ----------------------------------------------------------------------------

cmake/OpenCVDetectCUDA.cmake

@@ -216,40 +216,18 @@ else()
 endif()
 
 if(HAVE_CUDA)
-  set(CUDA_LIBS_PATH "")
-  foreach(p ${CUDA_LIBRARIES} ${CUDA_npp_LIBRARY})
-    get_filename_component(_tmp ${p} PATH)
-    list(APPEND CUDA_LIBS_PATH ${_tmp})
-  endforeach()
-
-  if(HAVE_CUBLAS)
-    foreach(p ${CUDA_cublas_LIBRARY})
-      get_filename_component(_tmp ${p} PATH)
-      list(APPEND CUDA_LIBS_PATH ${_tmp})
-    endforeach()
-  endif()
-
-  if(HAVE_CUFFT)
-    foreach(p ${CUDA_cufft_LIBRARY})
-      get_filename_component(_tmp ${p} PATH)
-      list(APPEND CUDA_LIBS_PATH ${_tmp})
-    endforeach()
-  endif()
-
-  list(REMOVE_DUPLICATES CUDA_LIBS_PATH)
-  link_directories(${CUDA_LIBS_PATH})
-
   set(CUDA_LIBRARIES_ABS ${CUDA_LIBRARIES})
-  ocv_convert_to_lib_name(CUDA_LIBRARIES ${CUDA_LIBRARIES})
+  ocv_create_imported_targets(CUDA_LIBRARIES ${CUDA_LIBRARIES})
   set(CUDA_npp_LIBRARY_ABS ${CUDA_npp_LIBRARY})
-  ocv_convert_to_lib_name(CUDA_npp_LIBRARY ${CUDA_npp_LIBRARY})
+  ocv_create_imported_targets(CUDA_npp_LIBRARY ${CUDA_npp_LIBRARY})
+
   if(HAVE_CUBLAS)
     set(CUDA_cublas_LIBRARY_ABS ${CUDA_cublas_LIBRARY})
-    ocv_convert_to_lib_name(CUDA_cublas_LIBRARY ${CUDA_cublas_LIBRARY})
+    ocv_create_imported_targets(CUDA_cublas_LIBRARY ${CUDA_cublas_LIBRARY})
   endif()
 
   if(HAVE_CUFFT)
     set(CUDA_cufft_LIBRARY_ABS ${CUDA_cufft_LIBRARY})
-    ocv_convert_to_lib_name(CUDA_cufft_LIBRARY ${CUDA_cufft_LIBRARY})
+    ocv_create_imported_targets(CUDA_cufft_LIBRARY ${CUDA_cufft_LIBRARY})
   endif()
 endif()

cmake/OpenCVGenPkgconfig.cmake

@@ -63,22 +63,23 @@ endforeach()
 # add extra dependencies required for OpenCV
 if(OpenCV_EXTRA_COMPONENTS)
   foreach(extra_component ${OpenCV_EXTRA_COMPONENTS})
+    if(TARGET "${extra_component}")
+      get_target_property(extra_component_is_imported "${extra_component}" IMPORTED)
+      if(extra_component_is_imported)
+        get_target_property(extra_component "${extra_component}" LOCATION)
+      endif()
+    endif()
 
-    if(extra_component MATCHES "^-[lL]")
-      set(libprefix "")
-      set(libname "${extra_component}")
+    if(extra_component MATCHES "^-l")
+      list(APPEND OpenCV_LIB_COMPONENTS_ "${extra_component}")
     elseif(extra_component MATCHES "[\\/]")
       get_filename_component(libdir "${extra_component}" PATH)
-      list(APPEND OpenCV_LIB_COMPONENTS_ "-L${libdir}")
       get_filename_component(libname "${extra_component}" NAME_WE)
       string(REGEX REPLACE "^lib" "" libname "${libname}")
-      set(libprefix "-l")
+      list(APPEND OpenCV_LIB_COMPONENTS_ "-L${libdir}" "-l${libname}")
     else()
-      set(libprefix "-l")
-      set(libname "${extra_component}")
+      list(APPEND OpenCV_LIB_COMPONENTS_ "-l${extra_component}")
     endif()
-    list(APPEND OpenCV_LIB_COMPONENTS_ "${libprefix}${libname}")
-
   endforeach()
 endif()
 

cmake/OpenCVModule.cmake

@@ -919,25 +919,28 @@ macro(__ocv_track_module_link_dependencies the_module optkind)
       list(REMOVE_AT __mod_depends 0)
       if(__dep STREQUAL the_module)
         set(__has_cycle TRUE)
-      else()#if("${OPENCV_MODULES_BUILD}" MATCHES "(^|;)${__dep}(;|$)")
+      else()
         ocv_regex_escape(__rdep "${__dep}")
         if(__resolved_deps MATCHES "(^|;)${__rdep}(;|$)")
           #all dependencies of this module are already resolved
           list(APPEND ${the_module}_MODULE_DEPS_${optkind} "${__dep}")
         elseif(TARGET ${__dep})
-          get_target_property(__module_type ${__dep} TYPE)
-          if(__module_type STREQUAL "STATIC_LIBRARY")
-            if(NOT DEFINED ${__dep}_LIB_DEPENDS_${optkind})
-              ocv_split_libs_list(${__dep}_LIB_DEPENDS ${__dep}_LIB_DEPENDS_DBG ${__dep}_LIB_DEPENDS_OPT)
+          get_target_property(__dep_imported ${__dep} IMPORTED)
+          if(__dep_imported)
+            list(APPEND ${the_module}_EXTRA_DEPS_${optkind} "${__dep}")
+          else()
+            get_target_property(__module_type ${__dep} TYPE)
+            if(__module_type STREQUAL "STATIC_LIBRARY")
+              if(NOT DEFINED ${__dep}_LIB_DEPENDS_${optkind})
+                ocv_split_libs_list(${__dep}_LIB_DEPENDS ${__dep}_LIB_DEPENDS_DBG ${__dep}_LIB_DEPENDS_OPT)
+              endif()
+              list(INSERT __mod_depends 0 ${${__dep}_LIB_DEPENDS_${optkind}} ${__dep})
+              list(APPEND __resolved_deps "${__dep}")
             endif()
-            list(INSERT __mod_depends 0 ${${__dep}_LIB_DEPENDS_${optkind}} ${__dep})
-            list(APPEND __resolved_deps "${__dep}")
           endif()
         else()
           list(APPEND  ${the_module}_EXTRA_DEPS_${optkind} "${__dep}")
         endif()
-      #else()
-       # get_target_property(__dep_location "${__dep}" LOCATION)
       endif()
     endwhile()
 
@@ -951,7 +954,7 @@ macro(__ocv_track_module_link_dependencies the_module optkind)
       list(APPEND ${the_module}_MODULE_DEPS_${optkind} "${the_module}")
     endif()
 
-    unset(__dep_location)
+    unset(__dep_imported)
     unset(__mod_depends)
     unset(__resolved_deps)
     unset(__has_cycle)

cmake/OpenCVUtils.cmake

@@ -459,6 +459,19 @@ function(ocv_convert_to_lib_name var)
   set(${var} ${tmp} PARENT_SCOPE)
 endfunction()
 
+# create imported targets for a list of external libraries
+function(ocv_create_imported_targets var)
+  set(target_list "")
+
+  foreach(library ${ARGN})
+    ocv_convert_to_lib_name(libname "${library}")
+    add_library("opencv_dep_${libname}" UNKNOWN IMPORTED)
+    set_target_properties("opencv_dep_${libname}" PROPERTIES IMPORTED_LOCATION "${library}")
+    list(APPEND target_list "opencv_dep_${libname}")
+  endforeach()
+
+  set("${var}" "${target_list}" PARENT_SCOPE)
+endfunction()
 
 # add install command
 function(ocv_install_target)

cmake/templates/OpenCV.mk.in

@@ -104,7 +104,7 @@ endef
 define add_cuda_module
     include $(CLEAR_VARS)
     LOCAL_MODULE:=$1
-    LOCAL_SRC_FILES:=$(CUDA_TOOLKIT_DIR)/targets/armv7-linux-androideabi/lib/lib$1.so
+    LOCAL_SRC_FILES:=$(CUDA_TOOLKIT_DIR)/targets/armv7-linux-androideabi/lib/lib$(1:opencv_dep_%=%).so
     include $(PREBUILT_SHARED_LIBRARY)
 endef
 
@@ -202,7 +202,8 @@ ifeq ($(OPENCV_USE_GPU_MODULE),on)
     ifeq ($(INSTALL_CUDA_LIBRARIES),on)
         LOCAL_SHARED_LIBRARIES += $(foreach mod, $(CUDA_RUNTIME_LIBS), $(mod))
     else
-        LOCAL_LDLIBS += -L$(CUDA_TOOLKIT_DIR)/targets/armv7-linux-androideabi/lib $(foreach lib, $(CUDA_RUNTIME_LIBS), -l$(lib))
+        LOCAL_LDLIBS += -L$(CUDA_TOOLKIT_DIR)/targets/armv7-linux-androideabi/lib \
+            $(foreach lib, $(CUDA_RUNTIME_LIBS), -l$(lib:opencv_dep_%=%))
     endif
     LOCAL_STATIC_LIBRARIES+=libopencv_gpu
 endif

cmake/templates/OpenCVConfig.cmake.in

@@ -236,7 +236,7 @@ foreach(__opttype OPT DBG)
   SET(OpenCV_EXTRA_LIBS_${__opttype} "")
 endforeach()
 
-# CUDA
+# Configure CUDA targets
 if(OpenCV_CUDA_VERSION)
   if(NOT CUDA_FOUND)
     find_host_package(CUDA ${OpenCV_CUDA_VERSION} EXACT REQUIRED)
@@ -273,17 +273,16 @@ if(OpenCV_CUDA_VERSION)
     list(APPEND OpenCV_CUDA_LIBS_ABSPATH ${CUDA_nvcuvenc_LIBRARIES})
   endif()
 
-  set(OpenCV_CUDA_LIBS_RELPATH "")
   foreach(l ${OpenCV_CUDA_LIBS_ABSPATH})
-    get_filename_component(_tmp ${l} PATH)
-    list(APPEND OpenCV_CUDA_LIBS_RELPATH ${_tmp})
+    get_filename_component(_tmp "${l}" NAME_WE)
+    string(REGEX REPLACE "^lib" "" _tmp "${_tmp}")
+    if(NOT TARGET "opencv_dep_${_tmp}") # protect against repeated inclusions
+      add_library("opencv_dep_${_tmp}" UNKNOWN IMPORTED)
+      set_target_properties("opencv_dep_${_tmp}" PROPERTIES IMPORTED_LOCATION "${l}")
+    endif()
   endforeach()
-
-  list(REMOVE_DUPLICATES OpenCV_CUDA_LIBS_RELPATH)
-  link_directories(${OpenCV_CUDA_LIBS_RELPATH})
 endif()
 
-
 # ==============================================================
 #  Android camera helper macro
 # ==============================================================