bug#22086: 25.1.50; [PATCH] Integrate the musl hybrid mallo

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 22086@debbugs.gnu.org, Rich Felker <dalias@aerifal.cx>,
>  Daniel Colascione <dancol@dancol.org>, Ken Brown <kbrown@cornell.edu>,
>  Eli Zaretskii <eliz@gnu.org>
> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Sat, 30 Jan 2016 01:17:21 -0800
> 
> The recent emacs-devel thread "Removal of unexec support" has raised the 
> priority of this bug, so I redid the patches to separate out Rich Felker's 
> contribution, which is so small as to not require copyright papers, and fixed 
> several problems I found with the resulting approach. I came up with the 
> attached set of patches relative to commit 
> ef760b899ad89f941f552ed2d3ac9e45156f3e3c. I would like to commit this patch set 
> to the emacs-25 branch soon, and am sending this email to give you (particularly 
> Eli) a heads-up about this.

I'm sorry, I can't afford testing this large patchset at this time,
while preparations to the pretest are under way.  I also don't think
such pervasive changes should be done on the release branch.  I think
when the time comes you should commit this to the master branch, not
to emacs-25.  In the meantime, a public feature branch will allow
people to try it and see if it breaks anything.

Thanks.

> These patches attempt to be more conservative than the other alternatives 
> discussed in Bug#22086. They don't try to build a better dumper or remove 
> gmalloc.c or anything like that. All they try to do, is to disentangle Emacs 
> from glibc malloc internals, by renaming functions whose APIs are no longer 
> compatible with glibc, and by using glibc's <malloc.h> rather than guessing what 
> it will say, and that sort of thing. The goal is for the resulting Emacs to not 
> only port to musl, but also to port to future glibc with less likelihood of trouble.

As the issue with glibc is only relevant to GNU/Linux systems, I
wonder if a solution that is limited to some file(s) specific to that
target could be possible.  Even then I'd hesitate to do this on the
release branch, since making Emacs less stable even on that single
platform will most probably delay the v25.1 release too much -- we
cannot possibly release Emacs 25 that is not stable on GNU/Linux.  But
at least we won't need to review and debug the results of this on
platforms that don't need these changes at all.

The glibc guys said the change won't happen too soon, so I see no
reason to delay Emacs 25 on behalf of this issue.

Thanks again for doing this work.