Merge pull request Tencent#1124 from DerDakon/CMake-cleanup

CMake cleanups

Author: miloyip

CMakeLists.txt

@@ -31,6 +31,10 @@ option(RAPIDJSON_BUILD_THIRDPARTY_GTEST
     "Use gtest installation in `thirdparty/gtest` by default if available" OFF)
 
 option(RAPIDJSON_BUILD_CXX11 "Build rapidjson with C++11 (gcc/clang)" ON)
+if(RAPIDJSON_BUILD_CXX11)
+    set(CMAKE_CXX_STANDARD 11)
+    set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
+endif()
 
 option(RAPIDJSON_BUILD_ASAN "Build rapidjson with address sanitizer (gcc/clang)" OFF)
 option(RAPIDJSON_BUILD_UBSAN "Build rapidjson with undefined behavior sanitizer (gcc/clang)" OFF)
@@ -51,9 +55,9 @@ if(CCACHE_FOUND)
     endif()
 endif(CCACHE_FOUND)
 
-if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
-    if(${RAPIDJSON_ENABLE_INSTRUMENTATION_OPT})
-        if("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "powerpc" OR "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "ppc64" OR "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "ppc64le")
+if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    if(RAPIDJSON_ENABLE_INSTRUMENTATION_OPT AND NOT CMAKE_CROSSCOMPILING)
+        if(CMAKE_SYSTEM_PROCESSOR STREQUAL "powerpc" OR CMAKE_SYSTEM_PROCESSOR STREQUAL "ppc64" OR CMAKE_SYSTEM_PROCESSOR STREQUAL "ppc64le")
           set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mcpu=native")
         else()
           #FIXME: x86 is -march=native, but doesn't mean every arch is this option. To keep original project's compatibility, I leave this except POWER.
@@ -62,7 +66,7 @@ if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
     endif()
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Werror")
     set(EXTRA_CXX_FLAGS -Weffc++ -Wswitch-default -Wfloat-equal -Wconversion -Wsign-conversion)
-    if (RAPIDJSON_BUILD_CXX11)
+    if (RAPIDJSON_BUILD_CXX11 AND CMAKE_VERSION VERSION_LESS 3.1)
         if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS "4.7.0")
             set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
         else()
@@ -84,15 +88,17 @@ if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
         endif()
     endif()
 elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-    if("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "powerpc" OR "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "ppc64" OR "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "ppc64le")
-      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mcpu=native")
-    else()
-      #FIXME: x86 is -march=native, but doesn't mean every arch is this option. To keep original project's compatibility, I leave this except POWER.
-      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=native")
+    if(NOT CMAKE_CROSSCOMPILING)
+      if(CMAKE_SYSTEM_PROCESSOR STREQUAL "powerpc" OR CMAKE_SYSTEM_PROCESSOR STREQUAL "ppc64" OR CMAKE_SYSTEM_PROCESSOR STREQUAL "ppc64le")
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mcpu=native")
+      else()
+        #FIXME: x86 is -march=native, but doesn't mean every arch is this option. To keep original project's compatibility, I leave this except POWER.
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=native")
+      endif()
     endif()
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Werror -Wno-missing-field-initializers")
     set(EXTRA_CXX_FLAGS -Weffc++ -Wswitch-default -Wfloat-equal -Wconversion -Wimplicit-fallthrough)
-    if (RAPIDJSON_BUILD_CXX11)
+    if (RAPIDJSON_BUILD_CXX11 AND CMAKE_VERSION VERSION_LESS 3.1)
         set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
     endif()
     if (RAPIDJSON_BUILD_ASAN)
@@ -105,7 +111,7 @@ elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
             set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=undefined")
         endif()
     endif()
-elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
+elseif (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
     add_definitions(-D_CRT_SECURE_NO_WARNINGS=1)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /EHsc")
 elseif (CMAKE_CXX_COMPILER_ID MATCHES "XL")