bug#47138: 28.0.50; comp-tests suite creates a /nonexistent directory

[Eli Zaretskii]

> From: Andrea Corallo <akrl@sdf.org>
> Cc: 47138@debbugs.gnu.org
> Date: Sun, 21 Mar 2021 08:43:36 +0000
> 
> >   $ cd test
> >   $ make src/comp-tests SELECTOR='(not comp-tests-bootstrap)'
> 
> Is /nonexistent... really created in the root?

Yes.  (Well, no, because MinGW maps "/" to some place else, but that's
an internal detail of how MinGW and MSYS work with Posix file names.)

> AFAICS on my system the usual 'native-lisp' directory is used for
> these compilations.

Really? that's peculiar, because test/Makefile says:

  # Set HOME to a nonexistent directory to prevent tests from accessing
  # it accidentally (e.g., popping up a gnupg dialog if ~/.authinfo.gpg
  # exists, or writing to ~/.bzr.log when running bzr commands).
  TEST_HOME = /nonexistent
  ...
  %.log: %.elc
        $(AM_V_at)${MKDIR_P} $(dir $@)
        $(AM_V_GEN)HOME=$(TEST_HOME) $(emacs) \
          -l ert ${ert_opts} -l $(testloadfile) \
          $(TEST_RUN_ERT)

Does Emacs on GNU/Linux ignore a nonexistent home directory, and uses
the original one instead?  That'd mean the above trick isn't working.

> Might be this Windows specific?

I hope not.