ENH: Upgrade ITK from C++14 to C++17

Follow-up to pull request #2563
commit daec0fd
"ENH: Upgrade ITK from C++11 to C++14"

CMake/ITKInitializeCXXStandard.cmake

@@ -1,6 +1,6 @@
 ##  Set the default target properties for ITK
 if(NOT CMAKE_CXX_STANDARD)
-  set(CMAKE_CXX_STANDARD 14) # Supported values are 14, 17, 20, and 23.
+  set(CMAKE_CXX_STANDARD 17) # Supported values are 17, 20, and 23.
 endif()
 if(NOT CMAKE_CXX_STANDARD_REQUIRED)
   set(CMAKE_CXX_STANDARD_REQUIRED ON)

CMake/itkCompilerChecks.cmake

@@ -28,13 +28,13 @@ if (CMAKE_CXX_COMPILER_ID STREQUAL "Intel" AND
   message(FATAL_ERROR "Intel C++ (ICC) 17.0 or later is required.")
 endif ()
 
-# Make sure we have C++14 enabled.
-if(NOT ITK_IGNORE_CMAKE_CXX14_CHECKS)
+# Make sure we have C++17 enabled.
+if(NOT ITK_IGNORE_CMAKE_CXX17_CHECKS)
   # Needed to make sure libraries and executables not built by the
-  # itkModuleMacros still have the C++14 compiler flags enabled
+  # itkModuleMacros still have the C++17 compiler flags enabled
   # Wrap this in an escape hatch for unknown compilers
   if(NOT CMAKE_CXX_STANDARD)
-    set(CMAKE_CXX_STANDARD 14) # Supported values are 14, 17, 20, and 23.
+    set(CMAKE_CXX_STANDARD 17) # Supported values are 17, 20, and 23.
   endif()
   if(NOT CMAKE_CXX_STANDARD_REQUIRED)
     set(CMAKE_CXX_STANDARD_REQUIRED ON)

CMakeLists.txt

@@ -33,9 +33,9 @@ endforeach()
 include(${CMAKE_CURRENT_SOURCE_DIR}/CMake/ITKInitializeCXXStandard.cmake)
 include(${CMAKE_CURRENT_SOURCE_DIR}/CMake/ITKInitializeBuildType.cmake)
 
-# ==== Define language standard configurations requiring at least c++14 standard
-if(CMAKE_CXX_STANDARD EQUAL "98" OR CMAKE_CXX_STANDARD LESS "14")
-   message(FATAL_ERROR "C++98 to C++11 are no longer supported in ITK version 5.3 and greater.")
+# ==== Define language standard configurations requiring at least c++17 standard
+if(CMAKE_CXX_STANDARD EQUAL "98" OR CMAKE_CXX_STANDARD LESS "17")
+   message(FATAL_ERROR "C++98 to C++14 are no longer supported in ITK version 5.4 and greater.")
 endif()
 
 set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/CMake ${CMAKE_MODULE_PATH})

Wrapping/macro_files/itk_auto_load_submodules.cmake

@@ -22,9 +22,9 @@ function(generate_castxml_commandline_flags)
     # Avoid missing omp.h include
     set(_castxml_cc_flags ${CMAKE_CXX_FLAGS})
     if(CMAKE_CXX_EXTENSIONS)
-        set(_castxml_cc_flags "${_castxml_cc_flags} ${CMAKE_CXX14_EXTENSION_COMPILE_OPTION}")
+        set(_castxml_cc_flags "${_castxml_cc_flags} ${CMAKE_CXX17_EXTENSION_COMPILE_OPTION}")
     else()
-        set(_castxml_cc_flags "${_castxml_cc_flags} ${CMAKE_CXX14_STANDARD_COMPILE_OPTION}")
+        set(_castxml_cc_flags "${_castxml_cc_flags} ${CMAKE_CXX17_STANDARD_COMPILE_OPTION}")
     endif()
 
     # Aggressive optimization flags cause cast_xml to give invalid error conditions