Compilare: user.cpp: In member function ‘char Reader::gLetter()’: user.cpp:57:16: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] return NULL; ^ user.cpp: In function ‘int main()’: user.cpp:136:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("vmin.in", "r", stdin); ^ user.cpp:137:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("vmin.out", "w", stdout); ^ user.cpp: In member function ‘char Reader::gChar()’: user.cpp:38:42: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buff, buffer, 1, stdin); ^