Compilare: main.cpp: In function 'int main()': main.cpp:11:42: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] #define FO(x) {freopen(#x".in","r",stdin);freopen(#x".out","w",stdout);} ^ main.cpp:70:9: note: in expansion of macro 'FO' FO(huffman); ^~ main.cpp:11:71: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] #define FO(x) {freopen(#x".in","r",stdin);freopen(#x".out","w",stdout);} ^ main.cpp:70:9: note: in expansion of macro 'FO' FO(huffman); ^~