bug#51466: bug#53355: guix shell --check: confusing error message

[Josselin Poiret via Bug reports for GNU Guix <bug-guix@gnu.org>]

Hello everyone, 

Maxime Devos <maximedevos@telenet.be> writes:

> Chris Marusich schreef op za 25-06-2022 om 09:52 [-0700]:
>> [...]
>> the problem was that I could not control Guile's choice
>> of
>> file descriptors.  Guile chose file descriptor 19 for one end of the
>> pipe, and I don't know how to make it use anything else.  If we can
>> arrange for Guile to consistently use file descriptor 7, for example,
>> then probably it would work in all the shell I've tested.
> Have a look at ‘(guile)Ports and File Descriptors’.  It has lots of
> procedures for duplicating and renumbering.  That's fragile though, you
> might accidentally overwrite an fd that's being used for something
> else.

Just my 2¢, from my experience, Guile uses a lot of fds (`guile -q` uses
15).  I'm not sure it would be safe or advisable to move fds, since we
cannot be sure that they're backing ports or not, and if they're not it
would break things.  In general, the Guile ports/fds interface works ok,
but there is a lot of code that is fragile and doesn't handle
edge-cases.

Best,
-- 
Josselin Poiret