I have looked at a few source files for your current software. I have noticed that some checks for return codes are missing. Would you like to add more error handling for return values from functions like the following? - [fgetpos](http://pubs.opengroup.org/onlinepubs/9699919799/functions/fgetpos.html) ⇒ [copy_hunk](https://github.com/twaugh/patchutils/blob/44a1a327310eb2a222ae190c183fb146ea8beaac/src/rediff.c#L74) - [fputs](http://pubs.opengroup.org/onlinepubs/9699919799/functions/fputs.html) ⇒ [output_header_line](https://github.com/twaugh/patchutils/blob/f39134c7b51bf591ff494496cddf9e5cae38c80a/src/filterdiff.c#L155) - [fwrite](http://pubs.opengroup.org/onlinepubs/9699919799/functions/fprintf.html) ⇒ [xopen_seekable](https://github.com/twaugh/patchutils/blob/92255b5934f0eb2465bd9472e900cd460efdd1d8/src/util.c#L199)