/in/foo.cc:1:19: warning: extra tokens at end of #include directive
 #include <cstdio> int main() {int a, b; printf("%d", a + b);}
                   ^~~
/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/Scrt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status