Compilare: user.cpp: In instantiation of ‘t_info list<t_key, t_info>::i_search(t_key) [with t_key = int; t_info = int]’: user.cpp:72:20: required from here user.cpp:180:10: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] return NULL; ^ user.cpp: In instantiation of ‘element<t_key, t_info>* list<t_key, t_info>::search(t_key) [with t_key = int; t_info = int]’: user.cpp:125:14: required from ‘void list<t_key, t_info>::addEl(t_key, t_info) [with t_key = int; t_info = int]’ user.cpp:64:16: required from here user.cpp:114:18: warning: variable ‘prev’ set but not used [-Wunused-but-set-variable] element<types> *prev = head; ^ user.cpp: In member function ‘t_info list<t_key, t_info>::i_search(t_key) [with t_key = int; t_info = int]’: user.cpp:182:1: warning: control reaches end of non-void function [-Wreturn-type] } ^