[cmake] Added ability to specify C++ std explicitly in -DCMAKE_CXX_FLAGS cmdline...

diff --git a/CMakeLists.txt b/CMakeLists.txt
index e1f1f47a58ca35fc7608fcbc1af7c2459ee89189..e6bdf69b3032bb0676ceea5ce99b0a9c631f93ec 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -98,7 +98,16 @@ if(NOT CMAKE_BUILD_TYPE)
 endif()
 
 if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall -Wextra -pedantic -fno-strict-aliasing")
+    string(REGEX MATCHALL "-std=[^ ]+" cxx_std_found ${CMAKE_CXX_FLAGS})
+    if(cxx_std_found)
+        message("C++ std: ${cxx_std_found}")
+    else()
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
+        message("C++ std: -std=c++11 (default)")
+    endif()
+
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -pedantic -fno-strict-aliasing")
+
     if(CMAKE_TARGET_ARCHITECTURE STREQUAL "x86_64")
         set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mcx16")
         set(LIB_SUFFIX "64")