In member function 'void SeqList::Append2(int)',
    inlined from 'SeqList::SeqList(int)' at foo.cc:23:11,
    inlined from 'int main()' at foo.cc:85:14:
foo.cc:28:19: warning: 's1.SeqList::n' may be used uninitialized [-Wmaybe-uninitialized]
   28 |                 a[n++]=x;
      |                   ^
foo.cc: In function 'int main()':
foo.cc:85:17: note: 's1' declared here
   85 |         SeqList s1(n);
      |                 ^~