bug#64954: GNU 'uptime' on OpenBSD always prints "0 users"

[Bruno Haible]

Paul Eggert wrote:
> > I'm fine with the change, but we'll also need to adjust
> > the sc_prohibit_always_true_header_tests syntax check in gnulib
> 
> I looked into that but it's such a hassle that I came up with the 
> attached simpler patch to Coreutils. How about installing it instead?

Yes, that's better than what I proposed, on two accounts:
  - Gnulib modules should better provide .h files that can be #included
    on any platform. Thus, it's Gnulib's task to provide a readutmp.h
    and a read_utmp() function that can also be used on native Windows.
  - It gets rid of the horrible hack to pass the values of two uninitialized
    variables down to a function.

Pádraig Brady wrote:
> gnulib docs
> state the following platforms have neither getutent or getutxent,
> and so might have issues with this?

OpenBSD 6.7, Minix 3.1.8, mingw, MSVC 14

On these platforms the #include "readutmp.h" would already provoke a
mass of syntax errors.

Btw, we don't test on Minix any longer (since Minix is dead),
and OpenBSD 6.x is end-of-life already [1].

Bruno

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