/in/foo.c: In function 'main':
/in/foo.c:40:5: error: variable-sized object may not be initialized
     int a[len]={0};
     ^~~
/in/foo.c:40:17: warning: excess elements in array initializer
     int a[len]={0};
                 ^
/in/foo.c:40:17: note: (near initialization for 'a')