Require C++17 (#834)

* Bump submodule past nmodl#889.

Author: olupton

CMake/MakefileBuildOptions.cmake

@@ -75,8 +75,7 @@ endforeach()
 # =============================================================================
 # compile flags : common to all backend
 # =============================================================================
-# PGI compiler adds --c++14;-A option for C++14, remove ";"
-string(REPLACE ";" " " CXX14_STD_FLAGS "${CMAKE_CXX14_STANDARD_COMPILE_OPTION}")
+string(JOIN " " CMAKE_CXX17_STANDARD_COMPILE_OPTION_STRING ${CMAKE_CXX17_STANDARD_COMPILE_OPTION})
 string(TOUPPER "${CMAKE_BUILD_TYPE}" _BUILD_TYPE)
 list(TRANSFORM CORENRN_COMPILE_DEFS PREPEND -D OUTPUT_VARIABLE CORENRN_COMPILE_DEF_FLAGS)
 string(
@@ -85,7 +84,7 @@ string(
   CORENRN_CXX_FLAGS
   ${CMAKE_CXX_FLAGS}
   ${CMAKE_CXX_FLAGS_${_BUILD_TYPE}}
-  ${CXX14_STD_FLAGS}
+  ${CMAKE_CXX17_STANDARD_COMPILE_OPTION_STRING}
   ${NVHPC_ACC_COMP_FLAGS}
   ${NVHPC_CXX_INLINE_FLAGS}
   ${CORENRN_COMPILE_DEF_FLAGS}

CMake/OpenAccHelper.cmake

@@ -85,8 +85,6 @@ if(CORENRN_ENABLE_GPU)
   else()
     message(FATAL_ERROR "${CORENRN_ACCELERATOR_OFFLOAD} not supported with NVHPC compilers")
   endif()
-  # avoid PGI adding standard compliant "-A" flags
-  set(CMAKE_CXX14_STANDARD_COMPILE_OPTION --c++14)
   string(APPEND CMAKE_EXE_LINKER_FLAGS " ${NVHPC_ACC_COMP_FLAGS}")
   # Use `-Mautoinline` option to compile .cpp files generated from .mod files only. This is
   # especially needed when we compile with -O0 or -O1 optimisation level where we get link errors.

CMakeLists.txt

@@ -23,18 +23,17 @@ math(EXPR CORENEURON_VERSION_COMBINED
 # =============================================================================
 # CMake common project settings
 # =============================================================================
-set(CMAKE_CXX_STANDARD 14)
+set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 set(CMAKE_BUILD_TYPE
     RelWithDebInfo
     CACHE STRING "Empty or one of Debug, Release, RelWithDebInfo")
 
-if(NOT "cxx_std_14" IN_LIST CMAKE_CXX_COMPILE_FEATURES OR NOT "cxx_digit_separators" IN_LIST
-                                                          CMAKE_CXX_COMPILE_FEATURES)
+if(NOT "cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
   message(
     FATAL_ERROR
-      "This compiler does not fully support C++14, choose an higher version or an other compiler.")
+      "This compiler does not fully support C++17, choose a higher version or another compiler.")
 endif()
 
 # =============================================================================
@@ -297,6 +296,11 @@ if(CORENRN_HAVE_NVHPC_COMPILER)
     # problem. If GPU support is disabled, we define R123_USE_INTRIN_H=0 to avoid the problem.
     list(APPEND CORENRN_COMPILE_DEFS R123_USE_INTRIN_H=0)
   endif()
+  # CMake versions <3.19 used to add -A when using NVHPC/PGI, which makes the compiler excessively
+  # pedantic. See https://gitlab.kitware.com/cmake/cmake/-/issues/20997.
+  if(CMAKE_VERSION VERSION_LESS 3.19)
+    list(REMOVE_ITEM CMAKE_CXX17_STANDARD_COMPILE_OPTION -A)
+  endif()
 endif()
 
 # ~~~