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    SubjectRe: PATCH: report NGROUPS_MAX via a sysctl (read-only)
    Tim Hockin <> wrote:
    > On Thu, Feb 19, 2004 at 09:30:28PM -0800, Andrew Morton wrote:
    > > > Attached is a simple patch to expose NGROUPS_MAX via sysctl.
    > >
    > > Why does userspace actually care? You try to do an oversized setgroups(),
    > > so you get an error?
    > I am systematically tracking down apps that use it. glibc is almost free of
    > it. sysconf() still uses it, but as long as the value compiled into glibc
    > as NGROUPS_MAX is less-than-or-equal-to the current kernel's idea, it meets
    > POSIX, right? If any one goes into their kernel source and lowers
    > NGROUPS_MAX they might break things, but I guess that isn't too big of a
    > worry. Some apps are still assuming that the value they get from sysconf()
    > is the absolute max number of groups. Anyone with libc compiled against an
    > older kernel will see 32, when they could have 64k.

    OK, well certainly fishing the number out of the currently-running kernel
    is the one sure way of getting it right.

    > > And why does NGROUPS_MAX still exist, come to that? AFAICT the only thing
    > Because Linus would not let me set it to INT_MAX. Something about
    > "insanity" ;)

    Is 64k enough?

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