bug#30350: 27.0.50; Newest master can't run processes on macOS

[Alan Third]

On Mon, Feb 05, 2018 at 04:36:13PM -0800, Paul Eggert wrote:
> The Gnulib manual says that macOS faccessat (..., "FILE/", ...) incorrectly
> succeeds when FILE is a regular file, and Gnulib has code to work around
> that bug that should be in effect for Emacs. However, the Gnulib manual
> doesn't say that faccessat (..., "FILE/.", ...) incorrectly succeeds in this
> situation, nor that faccessat (..., "FILE/./", ...) does the right thing;
> and the test program I gave you didn't illustrate any bugs in this area so
> I'm not sure what's going on.

Bear in mind that file-accessible-directory-p works prior to
call-process being run. Call-process does something that breaks it.

Interestingly it breaks file-accessible-directory-p for *all* files in
the same directory, so

    (call-process "/usr/bin/true")
    (file-accessible-directory-p "/usr/bin/false")

fails, while

    (call-process "/usr/bin/true")
    (file-accessible-directory-p "/bin/zsh")

works correctly. (Well, call-process itself fails, but
file-accessible-directory-p works.)

I haven’t been able to work out what it is that call-process is doing
that causes this.

-- 
Alan Third