How to compile the C++11 code by codeblocks?

I try to study the new style for C++11 about the inline namespace, Build one new project by codeblocks as following: namespace Parent { namespace Child1 { struct child1_data{int a;} ; } namespace Child2 { struct child2_data{int b;} ; } namespace child3 { child1_data data1;
child2_data data2;
} }enter image description here Failed on for the first time by codeblocks, then as the explanation, change the compiler by selected the C++11 ISO language standard, then click the build and run, still report the error message about child1_data and child2_data type. why?enter image description here