/in/foo.cc: In function 'void dfs1_iterative(int)':
/in/foo.cc:30:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17' [-Wc++17-extensions]
   30 |         auto [u, p, visited] = st.top();
      |              ^
/in/foo.cc: In function 'void dfs2_iterative(int)':
/in/foo.cc:65:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17' [-Wc++17-extensions]
   65 |         auto [u, t] = st.top();
      |              ^