Compilare: main.cpp: In function 'void readc(T&) [with T = int]': main.cpp:9:0: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] template <typename T> void printc(T t); template<> void printc(int v) { printf("%d ", v); } template<> void printc(unsigned int v) { printf("%u ", v); } template<> void printc(char v) { printf("%c ", v); } template<> void printc(long long v) { printf("%lld ", v); } template<> void printc(unsigned long long v) { printf("%llu ", v); } template<> void printc(float v) { printf("%f ", v); } template<> void printc(double v) { printf("%lf ", v); } template<> void printc<char *>(char *str) { printf("%s ", str); } template<> void printc<const char *>(const char *str) { printf("%s ", str); } template<typename E, typename U> void printc(const pair<E, U>& v) { printc(v.first); printc(v.second); } template<typename E> void printc(const vector<E>& v) { for (const E& e : v) printc(e); } template<typename T, typename... TArgs> void printc(const T& t, TArgs&&... args) { printc(t); printc(forward<TArgs>(args)...); } main.cpp: In function 'void readc(T&) [with T = unsigned int]': main.cpp:9:60: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] template <typename T> void printc(T t); template<> void printc(int v) { printf("%d ", v); } template<> void printc(unsigned int v) { printf("%u ", v); } template<> void printc(char v) { printf("%c ", v); } template<> void printc(long long v) { printf("%lld ", v); } template<> void printc(unsigned long long v) { printf("%llu ", v); } template<> void printc(float v) { printf("%f ", v); } template<> void printc(double v) { printf("%lf ", v); } template<> void printc<char *>(char *str) { printf("%s ", str); } template<> void printc<const char *>(const char *str) { printf("%s ", str); } template<typename E, typename U> void printc(const pair<E, U>& v) { printc(v.first); printc(v.second); } template<typename E> void printc(const vector<E>& v) { for (const E& e : v) printc(e); } template<typename T, typename... TArgs> void printc(const T& t, TArgs&&... args) { printc(t); printc(forward<TArgs>(args)...); } ^ main.cpp: In function 'void readc(T&) [with T = char]': main.cpp:9:113: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] template <typename T> void printc(T t); template<> void printc(int v) { printf("%d ", v); } template<> void printc(unsigned int v) { printf("%u ", v); } template<> void printc(char v) { printf("%c ", v); } template<> void printc(long long v) { printf("%lld ", v); } template<> void printc(unsigned long long v) { printf("%llu ", v); } template<> void printc(float v) { printf("%f ", v); } template<> void printc(double v) { printf("%lf ", v); } template<> void printc<char *>(char *str) { printf("%s ", str); } template<> void printc<const char *>(const char *str) { printf("%s ", str); } template<typename E, typename U> void printc(const pair<E, U>& v) { printc(v.first); printc(v.second); } template<typename E> void printc(const vector<E>& v) { for (const E& e : v) printc(e); } template<typename T, typename... TArgs> void printc(const T& t, TArgs&&... args) { printc(t); printc(forward<TArgs>(args)...); } ^ main.cpp: In function 'void readc(T&) [with T = long long int]': main.cpp:10:44: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] ^ main.cpp: In function 'void readc(T&) [with T = long long unsigned int]': main.cpp:10:112: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] ^ main.cpp: In function 'void readc(T&) [with T = float]': main.cpp:11:37: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] template <typename T> void __DEBUG_BASE(const T& t) { cout << t; } template <typename T, typename... TArgs> void __DEBUG_BASE(const T& t, TArgs&&... args) { __DEBUG_BASE(t); cout << ", "; __DEBUG_BASE(forward<TArgs>(args)...); } template <typename... TArgs> void __DEBUG_IMPL(TArgs&&... args) { __DEBUG_BASE(forward<TArgs>(args)...); } ^ main.cpp: In function 'void readc(T&) [with T = double]': main.cpp:11:92: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] template <typename T> void __DEBUG_BASE(const T& t) { cout << t; } template <typename T, typename... TArgs> void __DEBUG_BASE(const T& t, TArgs&&... args) { __DEBUG_BASE(t); cout << ", "; __DEBUG_BASE(forward<TArgs>(args)...); } template <typename... TArgs> void __DEBUG_IMPL(TArgs&&... args) { __DEBUG_BASE(forward<TArgs>(args)...); } ^ main.cpp: In function 'void readc(T&) [with T = char*]': main.cpp:12:90: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] ^ main.cpp: In function 'int main()': main.cpp:18:50: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] #define PB_FILE(nm) freopen(nm ".in", "r", stdin); freopen(nm ".out", "w", stdout) ^ main.cpp:26:5: note: in expansion of macro 'PB_FILE' PB_FILE("royfloyd"); ^~~~~~~ main.cpp:26:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] PB_FILE("royfloyd"); ^