setuid (euid) after setuid (uid) on System 5

[Doug Gwyn]

In article <1196 at auspex.UUCP> guy at auspex.UUCP (Guy Harris) writes:
>Both BSD and S5 flavors of "setuid" can be implemented atop "setreuid".

I don't think the "saved set-UID" feature can be emulated using setreuid().
Ron Natalie and I looked into this a few years ago and decided that a
simple semantic extension to setreuid() could be made that would enable
full emulation of saved set-UID, and that our extension would not cause
any new security holes.  However, we never got around to it and I have
since forgotten the details.  Maybe for 4.4BSD?