foo.cpp: In function 'int main()':
foo.cpp:6:5: warning: 'auto' changes meaning in C++11; please remove it [-Wc++0x-compat]
     auto c = a + b;
     ^
foo.cpp:6:10: error: 'c' does not name a type
     auto c = a + b;
          ^
foo.cpp:7:20: error: 'c' was not declared in this scope
     printf("%d\n", c);
                    ^