CMake: Do not unconditionally override settings without good reason

relates FairRootGroup/FairMQ#342

CMakeLists.txt

@@ -53,6 +53,7 @@ add_library(FairLogger
   logger/Logger.cxx
   logger/Logger.h
 )
+target_compile_features(FairLogger PUBLIC cxx_std_11)
 
 if(USE_BOOST_PRETTY_FUNCTION)
   target_link_libraries(FairLogger PUBLIC Boost::boost)
@@ -67,6 +68,7 @@ else()
     $<BUILD_INTERFACE:${CMAKE_SOURCE_DIR}/logger/bundled>
     $<INSTALL_INTERFACE:${PROJECT_INSTALL_BUNDLEDINCDIR}>
   )
+  target_compile_features(fmt PUBLIC cxx_std_11)
   target_compile_definitions(fmt INTERFACE FMT_HEADER_ONLY)
   target_link_libraries(FairLogger PUBLIC fmt)
 endif()

README.md

@@ -234,4 +234,4 @@ Define an option `FAIR_NO_LOG*` to prevent the above unprefixed macros to be def
 
 GNU Lesser General Public Licence (LGPL) version 3, see [LICENSE](LICENSE).
 
-Copyright (C) 2017-2020 GSI Helmholtzzentrum fuer Schwerionenforschung GmbH
+Copyright (C) 2017-2021 GSI Helmholtzzentrum fuer Schwerionenforschung GmbH

cmake/FairLoggerLib.cmake

@@ -95,23 +95,21 @@ macro(set_fairlogger_defaults)
 
   # Handle C++ standard level
   set(PROJECT_MIN_CXX_STANDARD 11)
-  set(CMAKE_CXX_STANDARD_REQUIRED ON)
-  if(NOT CMAKE_CXX_STANDARD)
-    set(CMAKE_CXX_STANDARD ${PROJECT_MIN_CXX_STANDARD})
-  elseif(${CMAKE_CXX_STANDARD} LESS ${PROJECT_MIN_CXX_STANDARD})
+  if(CMAKE_CXX_STANDARD LESS PROJECT_MIN_CXX_STANDARD)
     message(FATAL_ERROR "A minimum CMAKE_CXX_STANDARD of ${PROJECT_MIN_CXX_STANDARD} is required.")
   endif()
-  set(CMAKE_CXX_EXTENSIONS OFF)
 
   # Generate compile_commands.json file (https://clang.llvm.org/docs/JSONCompilationDatabase.html)
+  if(NOT DEFINED CMAKE_EXPORT_COMPILE_COMMANDS)
     set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+  endif()
 
-  if(NOT BUILD_SHARED_LIBS)
+  if(NOT DEFINED BUILD_SHARED_LIBS)
     set(BUILD_SHARED_LIBS ON CACHE BOOL "Whether to build shared libraries or static archives")
   endif()
 
   # Set -fPIC as default for all library types
-  if(NOT CMAKE_POSITION_INDEPENDENT_CODE)
+  if(NOT DEFINED CMAKE_POSITION_INDEPENDENT_CODE)
     set(CMAKE_POSITION_INDEPENDENT_CODE ON)
   endif()
 
@@ -130,13 +128,13 @@ macro(set_fairlogger_defaults)
   list(FIND CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES "${CMAKE_INSTALL_PREFIX}/${PROJECT_INSTALL_LIBDIR}" isSystemDir)
   if("${isSystemDir}" STREQUAL "-1")
     if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
-      set(CMAKE_EXE_LINKER_FLAGS ${CMAKE_EXE_LINKER_FLAGS} "-Wl,--enable-new-dtags")
-      set(CMAKE_SHARED_LINKER_FLAGS ${CMAKE_SHARED_LINKER_FLAGS} "-Wl,--enable-new-dtags")
-      set(CMAKE_INSTALL_RPATH "$ORIGIN/../${PROJECT_INSTALL_LIBDIR}")
+      list(APPEND CMAKE_EXE_LINKER_FLAGS "-Wl,--enable-new-dtags")
+      list(APPEND CMAKE_SHARED_LINKER_FLAGS "-Wl,--enable-new-dtags")
+      list(APPEND CMAKE_INSTALL_RPATH "$ORIGIN/../${PROJECT_INSTALL_LIBDIR}")
     elseif(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
-      set(CMAKE_INSTALL_RPATH "@loader_path/../${PROJECT_INSTALL_LIBDIR}")
+      list(APPEND CMAKE_INSTALL_RPATH "@loader_path/../${PROJECT_INSTALL_LIBDIR}")
     else()
-      set(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/${PROJECT_INSTALL_LIBDIR}")
+      list(APPEND CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/${PROJECT_INSTALL_LIBDIR}")
     endif()
   endif()