Merge branch 'fix-vtk-core-test-link-error'

* fix-vtk-core-test-link-error:
  Fix linking of VTKCoreCppTest by adding a check for linker capabilities

CMake/ctkLinkerAsNeededFlagCheck.cmake

@@ -0,0 +1,60 @@
+###########################################################################
+#
+#  Library:   CTK
+#
+#  Copyright (c) Kitware Inc.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0.txt
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+###########################################################################
+
+#
+# Linker --as-needed flag check
+#
+# Check if the linker will resolve symbols of underlinked libraries
+#
+# This script set the variable CTK_LINKER_NO_AS_NEEDED_FLAG_REQUIRED
+# to either TRUE or FALSE.
+#
+
+if(NOT DEFINED CTK_LINKER_NO_AS_NEEDED_FLAG_REQUIRED)
+  message(STATUS "Checking if --no-as-needed linker flag is required")
+  set(LINK_TEST_SOURCE_DIR ${CTK_CMAKE_DIR}/ctkLinkerAsNeededFlagCheck)
+  set(LINK_TEST_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/ctkLinkerAsNeededFlagCheck)
+  execute_process(COMMAND ${CMAKE_COMMAND} -E remove_directory ${LINK_TEST_BINARY_DIR})
+  try_compile(CTK_LINKER_LINKS_UNDERLINKED_LIBS
+    ${LINK_TEST_BINARY_DIR}
+    ${LINK_TEST_SOURCE_DIR}
+    LINK_TEST
+    )
+  if(CTK_LINKER_LINKS_UNDERLINKED_LIBS)
+    set(CTK_LINKER_NO_AS_NEEDED_FLAG_REQUIRED FALSE CACHE INTERNAL "Test CTK_LINKER_NO_AS_NEEDED_FLAG_REQUIRED")
+    message(STATUS "Checking if --no-as-needed linker flag is required - no")
+  else()
+    try_compile(CTK_LINKER_NO_AS_NEEDED_LINKS_UNDERLINKED_LIBS
+      ${LINK_TEST_BINARY_DIR}
+      ${LINK_TEST_SOURCE_DIR}
+      LINK_TEST_FLAGS
+      CMAKE_FLAGS -DCMAKE_EXE_LINKER_FLAGS=-Wl,--no-as-needed
+      )
+    if(CTK_LINKER_NO_AS_NEEDED_LINKS_UNDERLINKED_LIBS)
+      set(CTK_LINKER_NO_AS_NEEDED_FLAG_REQUIRED TRUE CACHE INTERNAL "Test CTK_LINKER_NO_AS_NEEDED_FLAG_REQUIRED")
+      message(STATUS "Checking if --no-as-needed linker flag is required - yes")
+    else()
+      message(STATUS "Checking if --no-as-needed linker flag is required - failed.")
+      message(WARNING "Could not compile test code."
+        "Linker could fail trying to resolve symbols for underlinked libraries."
+        "See issue 2321 (http://na-mic.org/Mantis/view.php?id=2321) for more details.")
+    endif()
+  endif()
+endif()

CMake/ctkLinkerAsNeededFlagCheck/A.cpp

@@ -0,0 +1,5 @@
+int B();
+int A()
+{
+  return B();
+}

CMake/ctkLinkerAsNeededFlagCheck/B.cpp

@@ -0,0 +1,4 @@
+int B()
+{
+  return 10;
+}

CMake/ctkLinkerAsNeededFlagCheck/C.cpp

@@ -0,0 +1,5 @@
+int A();
+int main()
+{
+  return A();
+}

CMake/ctkLinkerAsNeededFlagCheck/CMakeLists.txt

@@ -0,0 +1,4 @@
+add_library(A SHARED A.cpp)
+add_library(B SHARED B.cpp)
+add_executable(C C.cpp)
+target_link_libraries(C B A)

CMakeLists.txt

@@ -199,10 +199,20 @@ endforeach()
 
 foreach(file
   Libs/ctkExport.h.in
+  CMake/ctkLinkerAsNeededFlagCheck.cmake
   )
   install(FILES ${file} DESTINATION ${CTK_INSTALL_CMAKE_DIR} COMPONENT Development)
 endforeach()
 
+install(FILES
+  CMake/ctkLinkerAsNeededFlagCheck/CMakeLists.txt
+  CMake/ctkLinkerAsNeededFlagCheck/A.cpp
+  CMake/ctkLinkerAsNeededFlagCheck/B.cpp
+  CMake/ctkLinkerAsNeededFlagCheck/C.cpp
+  DESTINATION ${CTK_INSTALL_CMAKE_DIR}/ctkLinkerAsNeededFlagCheck
+  COMPONENT Development
+  )
+
 #-----------------------------------------------------------------------------
 # Testing
 #
@@ -329,6 +339,18 @@ if(MSVC)
 endif()
 
 #-----------------------------------------------------------------------------
+# Check if the linker will resolve symbols of underlinked libraries
+#
+if(UNIX AND NOT APPLE)
+  include(ctkLinkerAsNeededFlagCheck)
+  if(CTK_LINKER_NO_AS_NEEDED_FLAG_REQUIRED)
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--no-as-needed"
+      CACHE STRING "Flags used by the linker"
+      FORCE)
+  endif()
+endif()
+
+#-----------------------------------------------------------------------------
 # QT
 #
 ctkMacroSetupQt()