This is the equivalent patch to xserver commit eaf1f72ed8994b708d94ec2de7b1a99f5c4a39b8:
XkbStringText escapes non-printable characters using octal numbers. Such escape sequence would be at most 5 characters long ("\0123"), so it reserves 5 bytes in the buffer. Due to char->unsigned int conversion, it would print much longer string for negative numbers.
Fixes #8 (closed)