simplify logic, set standard at beginning

use a macro for bob_set_cxx_standard to avoid passing PARENT_SCOPE to set calls

CMakeLists.txt

@@ -13,12 +13,7 @@ include(cmake/xsdk.cmake)
 
 option(USE_XSDK_DEFAULTS "enable the XDSK v0.3.0 default configuration" NO)
 
-#requre c++11 without extensions
-set(CMAKE_CXX_STANDARD_REQUIRED ON)
-set(CMAKE_CXX_EXTENSION OFF)
-if(NOT ENABLE_CGNS)
-  set(CMAKE_CXX_STANDARD 11)
-endif()
+bob_set_cxx_standard(11)
 
 xsdk_begin_package()
 bob_begin_package()
@@ -27,20 +22,22 @@ if(USE_XSDK_DEFAULTS)
   xsdk_compiler_flags()
 endif()
 
-# require c++14
 option(ENABLE_CGNS "Enable the CGNS reader: requires c++14 extensions" OFF)
 message(STATUS "ENABLE_CGNS: ${ENABLE_CGNS}")
+if(ENABLE_CGNS)
+  message(STATUS "enabling cxx14")
+  bob_set_cxx_standard(14)
+endif()
 
 # Set some default compiler flags that should always be used
 if(NOT USE_XSDK_DEFAULTS)
   bob_set_shared_libs()
   bob_begin_cxx_flags()
   bob_end_cxx_flags()
   set(CMAKE_C_FLAGS "${CMAKE_CXX_FLAGS}")
-  if(ENABLE_CGNS) #takes precedence over SCOREC_ENABLE_CXX11
-    message(STATUS "enabling cxx14")
+  if(ENABLE_CGNS)
     bob_cxx14_flags()
-  elseif(SCOREC_ENABLE_CXX11)
+  else()
     bob_cxx11_flags()
   endif()
 endif()
@@ -193,9 +190,6 @@ add_library(core INTERFACE)
 target_link_libraries(core INTERFACE ${SCOREC_EXPORTED_TARGETS})
 if(ENABLE_CGNS)
   target_link_libraries(core INTERFACE ${CMAKE_DL_LIBS}) #HDF5 uses dlopen
-  target_compile_features(core INTERFACE cxx_std_14)
-else()
-  target_compile_features(core INTERFACE cxx_std_11)
 endif()
 scorec_export_library(core)
 

cmake/bob.cmake

@@ -78,7 +78,7 @@ function(bob_begin_cxx_flags)
 endfunction(bob_begin_cxx_flags)
 
 # The following is from the book,"Professional CMake: 19th edition"
-function(bob_setCxxStandard standard)
+macro(bob_set_cxx_standard standard)
   # Require C++<standard>, but let a parent project ask for something higher
   if(DEFINED CMAKE_CXX_STANDARD)
     if(CMAKE_CXX_STANDARD EQUAL 98 OR CMAKE_CXX_STANDARD LESS ${standard})
@@ -87,16 +87,16 @@ function(bob_setCxxStandard standard)
   else()
     set(CMAKE_CXX_STANDARD ${standard})
   endif()
+  message(STATUS "CMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD}")
   # Always enforce the language constraint
   set(CMAKE_CXX_STANDARD_REQUIRED ON)
   # We don't need compiler extensions, but let a parent ask for them
   if(NOT DEFINED CMAKE_CXX_EXTENSIONS)
     set(CMAKE_CXX_EXTENSIONS OFF)
   endif()
-endfunction()
+endmacro()
 
 function(bob_cxx11_flags)
-  bob_setCxxStandard(11)
   set(FLAGS "${CMAKE_CXX_FLAGS}")
   if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     if (${PROJECT_NAME}_CXX_WARNINGS)
@@ -107,7 +107,6 @@ function(bob_cxx11_flags)
 endfunction(bob_cxx11_flags)
 
 function(bob_cxx14_flags)
-  bob_setCxxStandard(14)
   set(FLAGS "${CMAKE_CXX_FLAGS}")
   set(FLAGS "${FLAGS} -Wall -Wextra -Wpedantic -Werror -Wno-extra-semi -Werror=unused-parameter -Wno-error=deprecated-declarations")
   if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")