Compilare: user.cpp: In function ‘int main()’: user.cpp:58:40: 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\n", stack.size()); ^ user.cpp:37:26: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d", &l); ^ user.cpp:41:30: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d", &n); ^ user.cpp:45:34: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d", &x); ^