There are several lines in the code which cause GCC to warn the user
about undefined behaviour. Most of these are potential buffer overflow
problems. Which come from either overwriting a buffer which may be too
small for a given input, or writing to, or from, a string not guaranteed
to be null-terminated, such as any of the char[] fields in a utmp
struct. Almost all come from an improper usage of strcmp or strncmp or
similar.
