Use -stdlib=libc++ only on Darwin systems for clang c++11 support

CMakeLists.txt

@@ -41,6 +41,16 @@ SET(EXT_CPP_PY "${EXT_SRC_CPP}.py")
 SET(THIRD_PARTY_DIR ${CMAKE_SOURCE_DIR}/third_party)
 SET(LIBSHOGUN_SRC_DIR ${CMAKE_SOURCE_DIR}/src/shogun)
 SET(COMMON_MODULAR_SRC_DIR ${CMAKE_SOURCE_DIR}/src/interfaces/modular/)
+
+# Detect OS
+IF(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+	SET(DARWIN 1)
+ELSEIF(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
+	SET(LINUX 1)
+ELSEIF(${CMAKE_SYSTEM_NAME} MATCHES "FreeBSD")
+	SET(FREEBSD 1)
+ENDIF()
+
 ################ COMPILER #######################
 # g++ version needs to be => 4.3
 IF(CMAKE_COMPILER_IS_GNUCXX)
@@ -83,15 +93,6 @@ STRING(REGEX REPLACE "([0-9]*).[0-9]*.[0-9]*" "\\1" SHOGUN_VERSION_MAJOR "${VERS
 STRING(REGEX REPLACE "[0-9]*.([0-9]*).[0-9]*" "\\1" SHOGUN_VERSION_MINOR "${VERSION}")
 STRING(REGEX REPLACE "[0-9]*.[0-9]*.([0-9]*)" "\\1" SHOGUN_VERSION_PATCH "${VERSION}")
 
-# Detect OS
-IF(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
-	SET(DARWIN 1)
-ELSEIF(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
-	SET(LINUX 1)
-ELSEIF(${CMAKE_SYSTEM_NAME} MATCHES "FreeBSD")
-	SET(FREEBSD 1)
-ENDIF()
-
 # Get processor type, sets MACHINE macro
 IF(NOT WIN32)
 	execute_process(COMMAND uname -m

cmake/CheckCXX11Features.cmake

@@ -63,7 +63,13 @@ if (NOT _HAS_CXX11_FLAG)
 endif ()
 
 if (_HAS_CXX11_FLAG)
-    if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
+    # apple's clang requires -stdlib=libc++ otherwise
+    # it won't find <atomic> for example.
+    # but this will break compilation on ubuntu
+    #
+    # TODO: investigate further which system requires -stdlib=libc++
+    # as well.
+    if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" AND DARWIN)
         set(CXX11_COMPILER_FLAGS "-std=c++11 -stdlib=libc++")
     else ()
         set(CXX11_COMPILER_FLAGS "-std=c++11")