The value returned by a64l() may be a pointer to a static buffer, possibly overwritten by later calls.
The behaviour of l64a() is undefined when value is negative. If value is zero, it returns an empty string.
These functions are broken in glibc before 2.2.5 (puts most significant digit first).
XPG 4.2, POSIX 1003.1-2001.
uuencode(1), itoa(3), strtoul(3)