foo.c: In function 'main':
foo.c:22:20: error: 'a' undeclared (first use in this function)
       {scanf("%d",&a[i]); }
                    ^
foo.c:22:20: note: each undeclared identifier is reported only once for each function it appears in
foo.c: In function 'buffer_left_move':
foo.c:15:5: warning: control reaches end of non-void function [-Wreturn-type]
     }
     ^

自豪的采用jd5进行评测(github.com/masnn/jd5)