Compilare: user.cpp: In function ‘int main()’: user.cpp:33:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i(0); i < strlen(expr);) { ^ user.cpp:37:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i < strlen(expr) && (expr[i] >= '0' && expr[i] <= '9')) { ^ user.cpp:16:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("evaluare.in", "r", stdin); ^ user.cpp:28:15: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(expr); ^ /tmp/ccVKtpUL.o: In function `main': user.cpp:(.text.startup+0xab): warning: the `gets' function is dangerous and should not be used.