foo.c: In function 'F':
foo.c:56:20: warning: unused variable 'j' [-Wunused-variable]
   56 |             int i, j, index;
      |                    ^
foo.c:65:13: warning: 'index' may be used uninitialized [-Wmaybe-uninitialized]
   65 |             Q(c, index);
      |             ^~~~~~~~~~~
foo.c:56:23: note: 'index' was declared here
   56 |             int i, j, index;
      |                       ^~~~~

[Hydro](https://hydro.ac)提供评测服务