der Mouse wrote:

> that really safe, is the list order not used by anything?  (Well,
>aside from the primary gid being special, but presumably the primary
>gid would be exempt from the sorting, and possibly the de-duping,
>anyway.)
>
>Access checking doesn't care about order, I think.  But is there, for
>example, code that depends on getgroups() returning a list identical to
>the one passed to setgroups()?
>  
>
If there is such code, I'd say it's poorly written. SUS writes, in the 
RATIONALE section:

"Various implementation variations and administrative sequences cause 
the set of groups appearing in the result of /getgroups/() to vary in 
order and as to whether the effective group ID is included, even when 
the set of groups is the same (in the mathematical sense of "set")."

- Frank