bug#47067: 28.0.50; [feature/native-comp] Crash while scrolling through dispnew.c

[Eli Zaretskii <eliz@gnu.org>]

> From: Andrea Corallo <akrl@sdf.org>
> Cc: 47067@debbugs.gnu.org
> Date: Sun, 04 Apr 2021 20:52:51 +0000
> 
> > Ah, I see now.  The list of the files that could be preloaded is in
> > $shortlisp, see src/Makefile.in.  The file names are read from
> > src/lisp.mk.
> 
> Here I'm, 6f8ec14491 should introduce the behaviour we wanted, preloaded
> files are now deposed in the 'preloaded' subfolder.
> 
> Also, 1ad0ecea2b reinstablish the fact that at each re-compilation we
> clean-up stale eln files in all the directories in `comp-eln-load-path',
> indeed this is excluding the introduced 'preloaded' subfolder.

Thanks.  Things seem to work quite well, AFAICS, but there's a subtle
problem (or maybe 2):

 . First, the problem with corrupted backtraces is back, although I
   verified that comp-debug is 1.  Strangely, it happens only for some
   *.eln files; others show full backtraces as expected.  The telltale
   sign of a "problematic" .eln file is that even when functions are
   shown in the backtrace with their fill names, the arguments of
   function calls aren't shown, something that shouldn't happen when
   there's debug info.

 . If I manually recompile a preloaded .el file, like this:

     emacs -batch -l comp -f batch-byte-native-compile-for-bootstrap ../lisp/isearch.el

   then the produced .eln file is written not into the preloaded
   folder, but into its parent, i.e. native-lisp/28.0.50-NNNNNN/.

And here is the possible link between these two issues: if I start
Emacs after compiling preloaded files manually as above, then Emacs
seems to load the *.eln files from native-lisp/28.0.50-NNNNNN/, not
from native-lisp/28.0.50-NNNNNN/preloaded, and the problems with the
backtraces miraculously disappear!

Any idea what is going on here?