/in/foo.c: In function 'main':
/in/foo.c:9:19: warning: 'a' is used uninitialized in this function [-Wuninitialized]
  for (int i = 0; a[j] != '\n'; i++,j=i-1)
                  ~^~~
/in/foo.c:24:7: note: 'a' was declared here
  char a[10000];
       ^
/in/foo.c:9:19: warning: 'b' may be used uninitialized in this function [-Wmaybe-uninitialized]
  for (int i = 0; a[j] != '\n'; i++,j=i-1)
                  ~^~~
/in/foo.c:25:7: note: 'b' was declared here
  char b[10000];
       ^