foo.cc: In function 'int unique(node*)':
foo.cc:15:13: warning: unused variable 'i' [-Wunused-variable]
   15 |         int i=0;
      |             ^
foo.cc: In function 'int main(int, char**)':
foo.cc:90:15: warning: 'list2' may be used uninitialized [-Wmaybe-uninitialized]
   90 |         output(list2);
      |         ~~~~~~^~~~~~~
foo.cc:56:22: note: 'list2' was declared here
   56 |         struct node *list2;
      |                      ^~~~~
foo.cc:89:15: warning: 'list1' may be used uninitialized [-Wmaybe-uninitialized]
   89 |         output(list1);
      |         ~~~~~~^~~~~~~
foo.cc:55:22: note: 'list1' was declared here
   55 |         struct node *list1;
      |                      ^~~~~

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