/in/foo.c: In function 'main':
/in/foo.c:4:13: error: 'n' undeclared (first use in this function)
     int i,a[n];
             ^
/in/foo.c:4:13: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:4:11: warning: unused variable 'a' [-Wunused-variable]
     int i,a[n];
           ^