Compilare: user.cpp: In member function ‘int Coada::pop()’: user.cpp:71:16: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] return NULL; ^ user.cpp: In function ‘int main()’: user.cpp:118:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<strlen(s);i++) ^ user.cpp:114:9: warning: unused variable ‘Optiune’ [-Wunused-variable] int Optiune, n, m; ^