stdio.h hacker in agony

[turner at ucbesvax.UUCP]

4.2BSD <stdio.h> has this gem of a non-comment:
    ...
    #ifdef vax
    char	*sprintf();		/* too painful to do right */
    #endif

I am curious--just what is "doing it right" in this case?
---
Michael Turner (ucbvax!ucbesvax.turner)