Re: master fails to build on FreeBSD when ACL support is on

[Glenn Morris <rgm@gnu.org>]

Glenn Morris wrote:

> IMO the change in 4fd446e is obviously correct.
> The current (reverted) code is wrong by inspection when target-file is
> relative. In normal use, it never is, but it will be if
> byte-compile-dest-file is changed to return a non-absolute value.
>
> For example, this can be the case for automake, as we saw in
>
> http://lists.gnu.org/archive/html/emacs-devel/2017-11/msg00551.html
>
> since Makefiles normally use relative filenames, and automake changes
> byte-compile-dest-file-function to return "$@".
>
> Eg I predict the following will fail on a FreeBSD system like the one in
> the original message in this thread:
>
> ./src/emacs --batch \
>  --eval '(setq byte-compile-dest-file-function (lambda (x) "foo.elc"))'
>   -f batch-byte-compile foo.el
>
> This simulates how automake may call Emacs to compile a file.
>
> (It fails on RHEL 7.4 with TMPDIR=/does/not/exist. Obviously this is not
> sensible, but the point is that it should not be writing to TMPDIR at all.)


Here is an instance of the failure that I predicted:

http://lists.nongnu.org/r/bbdb-user/2018-11/msg00003.html

Please consider backporting 64c8467 (the master version of the reverted
4fd446e from emacs-26) to the emacs-26 branch.