ENH: Add option ENABLED_SHARED to itk_module for shared libraries

Bump required cmake version to 2.8.6 for GenerateExportHeader.

This option enables shared libraries on windows and adds export
specification with gcc shared libraries. This option respects the
CMake variable BUILD_SHARED_LIBS.  Modules without this
specification can still be shared with gcc, but will be static with
msvc.

Change-Id: Ic1552ca64bb7e614e254cefe285802c96359ed3f

CMake/ITKModuleMacros.cmake

@@ -6,6 +6,8 @@ include(${_ITKModuleMacros_DIR}/ITKModuleAPI.cmake)
 include(${_ITKModuleMacros_DIR}/ITKModuleDoxygen.cmake)
 include(${_ITKModuleMacros_DIR}/ITKModuleHeaderTest.cmake)
 
+include(GenerateExportHeader)
+
 if(ITK_CPPCHECK_TEST)
   include(${_ITKModuleMacros_DIR}/ITKModuleCPPCheckTest.cmake)
 endif()
@@ -21,12 +23,16 @@ macro(itk_module _name)
   set(ITK_MODULE_${itk-module-test}_DEPENDS "${itk-module}")
   set(ITK_MODULE_${itk-module}_DESCRIPTION "description")
   set(ITK_MODULE_${itk-module}_EXCLUDE_FROM_ALL 0)
+  set(ITK_MODULE_${itk-module}_ENABLE_SHARED 0)
   foreach(arg ${ARGN})
     if("${arg}" MATCHES "^(DEPENDS|TEST_DEPENDS|DESCRIPTION|DEFAULT)$")
       set(_doing "${arg}")
     elseif("${arg}" MATCHES "^EXCLUDE_FROM_ALL$")
       set(_doing "")
       set(ITK_MODULE_${itk-module}_EXCLUDE_FROM_ALL 1)
+    elseif("${arg}" MATCHES "^ENABLE_SHARED$")
+      set(_doing "")
+      set(ITK_MODULE_${itk-module}_ENABLE_SHARED 1)
     elseif("${arg}" MATCHES "^[A-Z][A-Z][A-Z]$")
       set(_doing "")
       message(AUTHOR_WARNING "Unknown argument [${arg}]")
@@ -128,6 +134,23 @@ macro(itk_module_impl)
     add_subdirectory(src)
   endif()
 
+
+  if( ITK_MODULE_${itk-module}_ENABLE_SHARED )
+    # Generate the export macro header for symbol visibility/Windows DLL declspec
+    generate_export_header(${itk-module}
+      EXPORT_FILE_NAME ${ITKCommon_BINARY_DIR}/${itk-module}Export.h
+      EXPORT_MACRO_NAME ${itk-module}_EXPORT
+      NO_EXPORT_MACRO_NAME ${itk-module}_HIDDEN
+      STATIC_DEFINE ITK_STATIC )
+    if (BUILD_SHARED_LIBS)
+      # export flags are only added when building shared libs, they cause
+      # mismatched visibility warnings when building statically.
+      add_compiler_export_flags(my_abi_flags)
+      set_property(TARGET ${itk-module} APPEND
+        PROPERTY COMPILE_FLAGS "${my_abi_flags}")
+    endif()
+  endif()
+
   set(itk-module-EXPORT_CODE-build "${${itk-module}_EXPORT_CODE_BUILD}")
   set(itk-module-EXPORT_CODE-install "${${itk-module}_EXPORT_CODE_INSTALL}")
 

CMakeLists.txt

@@ -1,13 +1,11 @@
-cmake_minimum_required(VERSION 2.8.4 FATAL_ERROR)
+cmake_minimum_required(VERSION 2.8.6 FATAL_ERROR)
 include(CMakeDependentOption)
 #
 # use ExternalProject
 include(ExternalProject)
 
 if(WIN32)
   cmake_minimum_required(VERSION 2.8.8)
-elseif(NOT EXISTS /dev/urandom)
-  cmake_minimum_required(VERSION 2.8.5)
 endif()
 
 project(ITK)

Modules/Core/Common/include/itkMacro.h

@@ -40,6 +40,7 @@
 
 #include "itkWin32Header.h"
 #include "itkConfigure.h"
+#include "ITKCommonExport.h"
 
 #include <typeinfo>
 
@@ -101,6 +102,7 @@ namespace itk
 #endif
 
 // Setup symbol exports
+// begin legacy
 #if defined( _WIN32 ) || defined ( WIN32 )
   #define ITK_ABI_IMPORT __declspec(dllimport)
   #define ITK_ABI_EXPORT __declspec(dllexport)
@@ -116,27 +118,7 @@ namespace itk
     #define ITK_ABI_HIDDEN
   #endif
 #endif
-
-#define ITKCommon_HIDDEN ITK_ABI_HIDDEN
-
-#if !defined( ITKSTATIC )
-/* CMake adds "MyLibrary_EXPORTS" definition for MSVC platforms
- * when building a DLL */
-  #ifdef ITKCommon_EXPORTS
-    #define ITKCommon_EXPORT ITK_ABI_EXPORT
-  #else
-    #define ITKCommon_EXPORT ITK_ABI_IMPORT
-  #endif  /* ITKCommon_EXPORTS */
-#else
-  /* ITKCommon is build as a static lib */
-  #if __GNUC__ >= 4
-    // Don't hide symbols in the static ITKCommon library in case
-    // -fvisibility=hidden is used
-    #define ITKCommon_EXPORT ITK_ABI_EXPORT
-  #else
-    #define ITKCommon_EXPORT
-  #endif
-#endif
+// end legacy
 
 /** Define two object creation methods.  The first method, New(),
  * creates an object from a class, potentially deferring to a factory.

Modules/Core/Common/itk-module.cmake

@@ -7,6 +7,7 @@ platform specific features. It is anticipated that most other ITK modules will
 depend on this one.")
 
 itk_module(ITKCommon
+  ENABLE_SHARED
   DEPENDS
     ITKVNLInstantiation
     ITKKWSys

Modules/Core/Common/src/CMakeLists.txt

@@ -107,15 +107,6 @@ endif()
 
 ### generating libraries
 add_library( ITKCommon ${ITK_LIBRARY_BUILD_TYPE} ${ITKCommon_SRCS})
-if(NOT WIN32 AND CMAKE_COMPILER_IS_GNUCXX AND BUILD_SHARED_LIBS)
-  set(ITKCommon_CXX_FLAGS "-fvisibility=hidden -fvisibility-inlines-hidden")
-  ITK_CHECK_CXX_COMPILER_FLAG(${ITKCommon_CXX_FLAGS} ITKCommon_HAS_GCC_VISIBILITY_FLAGS)
-  if(ITKCommon_HAS_GCC_VISIBILITY_FLAGS)
-    set_target_properties(ITKCommon PROPERTIES
-      COMPILE_FLAGS "${ITKCommon_CXX_FLAGS}"
-    )
-  endif()
-endif()
 
 target_link_libraries(ITKCommon
   itksys