Compilare: user.cpp: In member function ‘bool list::check_common_element(list*)’: user.cpp:24:5: warning: no return statement in function returning non-void [-Wreturn-type] } ^ user.cpp: In function ‘int main()’: user.cpp:57:39: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 3 has type ‘std::stack<list*>::size_type {aka unsigned int}’ [-Wformat=] fprintf(fout, "%lu ", stack.size()); ^ user.cpp:36:26: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d", &l); ^ user.cpp:40:30: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d", &n); ^ user.cpp:44:34: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d", &x); ^