Compilare: user.cpp: In member function ‘output_writer& output_writer::operator<<(char*)’: user.cpp:57:32: warning: NULL used in arithmetic [-Wpointer-arith] while( *str_pos != NULL ) { ^ user.cpp: In function ‘int main()’: user.cpp:98:43: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings] output_file << V[P].c2 << "\n"; ^ user.cpp: In constructor ‘input_reader::input_reader(const char*, const char*)’: user.cpp:25:49: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread( buffer, SIZE, 1, input_file ); ^ user.cpp: In member function ‘void input_reader::advance()’: user.cpp:18:53: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread( buffer, SIZE, 1, input_file ); ^