/in/foo.c: In function 'main':
/in/foo.c:13:5: warning: implicit declaration of function 'fun' [-Wimplicit-function-declaration]
     fun(a,n);
     ^~~
/in/foo.c: At top level:
/in/foo.c:21:6: warning: conflicting types for 'fun'
 void fun(int a[],int n)
      ^~~
/in/foo.c:13:5: note: previous implicit declaration of 'fun' was here
     fun(a,n);
     ^~~