The glob pattern '[[:xdigit::]]*' didn't return the matches expected. It turns out the implementation (from glibc) fails to detect 'xdigit' as a valid character class. Changing the definition of CHAR_CLASS_MAX_LENGTH to 7 fixes the problem. This was never an issue in glibc because it uses a different definition. More modern versions of fnmatch(3) in glibc and gnulib also make CHAR_CLASS_MAX_LENGTH long enough. The code for fnmatch(3) was taken from glibc at commit 7814856974388a856a575fa45f88d502c8a1ab29. This was the last version before the code was rearraged to better support multibyte characters.