bug#28882: [bug-gnu-emacs] emacs-26.0.90 build feedback

[Nelson H. F. Beebe]

I now have more than 230 build attempts for emacs-26.0.90 in our
growing test lab with about 180 flavors of Unix(-like) operating
systems.

Of the initial 160 automated builds, 57 completed, and all that
I had to do manually was the "make install" step (at my site,
that is hidden in wrapper so that the installed executable is
named nemacs, for new emacs, so as not to overwrite any existing
version called emacs).

Unfortunately, a further 77 automated builds were broken by this
obnoxious failure:

>> ...
>>     configure: error: The following required libraries were not found:
>>       gnutls
>>     Maybe some development libraries/packages are missing?
>>     If you don't want to link with them give
>>       --with-gnutls=no
>>     as options to configure
>> ...

My suspicion is that the gnutls package is needed only for editing
files across a network, which few users ever do.  Thus, my strong view
is that, while it is fine for configure to test for the availability
of gnutls, it should NOT be a show-stopper that requires a manual
override and a fresh build attempt with that extra option.

I've expressed the view before on this list that the same should apply
for the various options for libraries that allow emacs to view
bitmap-graphics files, again a feature that few people are ever likely
to use.

With as many test systems as I have, it is utterly impractical to know
in advance which of the --with-XXX=no options are needed to avoid
configure-time termination.  Even if I wrote down once what those
options are for each system, subsequent system updates would likely
invalidate those choices, as would different versions of emacs.  On
several of my systems, there are GIF, JPEG, PNG, RSVG, TIFF,
... libraries installed, but configure may still reject them because
of version-number tests, or feature tests.

I strongly recommend that configure.ac be revised so that all
--with-XXX=[no|yes] options allow configuration and building to
proceed, regardless of their settings.  It is just too painful to have
to spend several unnecessary hours restarting builds to work around
the current undesirable behavior.

I still have a few systems where emacs-26.0.90 has not yet
successfully been built and installed, and I'm continuing to work on
finding solutions.  However, I wanted to get this report posted now
that I've done 125 successful installs.

On our old CentOS 5 systems (packages frozen by Red Hat), I got a
surprise message that has never appeared with any earlier version of
emacs (I have almost 6000 logs for emacs builds going back as far as
20-Aug-1998):

>> ...
>> loading /local/build/cc/emacs-26.0.90/lisp/leim/leim-list.el (source)...
>> Finding pointers to doc strings...
>> Finding pointers to doc strings...done
>> Dumping under the name emacs
>> **************************************************
>> Warning: Your system has a gap between BSS and the
>> heap (258966655 bytes).  This usually means that exec-shield
>> or something similar is in effect.  The dump may
>> fail because of this.  See the section about
>> exec-shield in etc/PROBLEMS for more information.
>> **************************************************
>> make[1]: *** [bootstrap-emacs] Segmentation fault (core dumped)
>> ...

I'm doubtful that CentOS 5 had any protection against stack/heap/bss
collision, because such discussions have only shown up on security
lists in the last several months.  Thus, it may be that the emacs test
for the unexpected gap is faulty.

The one class of operating systems for which emacs is known not to
work out-of-the-box from standard GNU distribution channels is Alpine
Linux. I have 5 VMs running various versions of that O/S.  Alpine uses
muscl instead of glibc, and has a different memory model that breaks
emacs, and also the tcsh shell.  Some Alpine versions have a patched
emacs in the package system, but the latest ones do not.  Thus,
emacs-26.0.90 will not build at all on Alpine Linux.

In no case has a build been stopped by emacs source code errors, but
some builds were stopped by link-time failures to find particular
functions.  In most cases, I could later get a successful build by
adding a suitable --with-XXX=no option to suppress use of a particular
library.

One final point: as far as I recall, in emacs-25 and earlier, the
Makefiles were carefully written to be usable by traditional Unix
make.  Sadly, that is no longer the case, and I think the changes that
now mandate GNU make for building emacs should be rescinded.

Even though most Unix-(like) systems other than GNU Hurd and GNU/Linux
have a gmake package, when bootstrapping a new system, usually the
first GNU package that I'm likely to build is GNU tar, and the second,
GNU emacs.  That means that both need to be buildable with traditional
make, and both are far too complex to do a build by manually running
cc.

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- Nelson H. F. Beebe                    Tel: +1 801 581 5254                  -
- University of Utah                    FAX: +1 801 581 4148                  -
- Department of Mathematics, 110 LCB    Internet e-mail: beebe@math.utah.edu  -
- 155 S 1400 E RM 233                       beebe@acm.org  beebe@computer.org -
- Salt Lake City, UT 84112-0090, USA    URL: http://www.math.utah.edu/~beebe/ -
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