/in/foo.cc: In function 'void dfs1(int)':
/in/foo.cc:17:8: error: 'dfs' was not declared in this scope
   dfs(p);
        ^
/in/foo.cc: In function 'void dfs2(int)':
/in/foo.cc:30:8: error: 'dfs' was not declared in this scope
   dfs(p);
        ^
/in/foo.cc: In function 'void dfs3(int)':
/in/foo.cc:43:9: error: 'dfs' was not declared in this scope
    dfs(p);
         ^