Re: Emacs 25.1 build failures on Ubuntu arm64

[Rob Browning <rlb@defaultvalue.org>]

Barry Warsaw <barry@python.org> writes:

> On Mar 29, 2017, at 04:46 PM, Barry Warsaw wrote:
>
>>I'll see if I can do a build of the Debian version of 25.1 in an Ubuntu 17.04
>>PPA to see if there are any different results.
>
> Indeed, Debian unstable's version of Emacs 25.1 also fails with the same
> segfault in the Ubuntu 17.04 PPA, as expected.  We can rule out any Ubuntu
> deltas.
>
> https://launchpadlibrarian.net/313465977/buildlog_ubuntu-zesty-arm64.emacs25_25.1+1-4~ppa0_BUILDING.txt.gz

I spent a bit of time on one of the porterboxes and gathered a little
more information, though in the end, we just added -O0 on arm64 for now
as well.

I was able to reproduce this on asachi using a git checkout of
origin/emacs-25.2 (i.e. clean upstream tree, no debian adjustments),
though I did emulate our VPATH build (see below).

One notable oddity -- while trying to narrow down the cause, I found
that the crash could be reliably triggered by adding the .git dir to the
(copied) build tree.  For example, this either builds, or crashes,
depending on whether or not the .git dir is introduced.

  rm -rf debian
  mkdir -p debian/build-src
  cp -a $(ls -A | egrep -v '^(\.git|\.pc|debian)$') debian/build-src

  # If this line is removed, the build works fine, otherwise it crashes
  cp -a .git debian/build-src/

  pushd debian/build-src
  ./autogen.sh
  popd
  mkdir debian/build-x
  cd debian/build-x
  ../build-src/configure ...
  make -j

When the build crashes, it's always while trying to produce c-by.el, and
the crash looks similar to the one reported earlier in this thread,
i.e.:

  Starting program: /home/rlb/git/emacs25-25.2+1/debian/build-x/src/emacs -batch --no-site-file --no-site-lisp -l semantic/bovine/grammar -f bovine-batch-make-parser -o /home/rlb/git/emacs25-25.2+1/debian/build-x/../../../emacs25-25.2+1/debian/build-src/lisp/cedet/semantic/bovine/c-by.el /home/rlb/git/emacs25-25.2+1/debian/build-x/../../../emacs25-25.2+1/debian/build-src/admin/grammars/c.by
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib/aarch64-linux-gnu/libthread_db.so.1".
  [New Thread 0xffffb36dbe10 (LWP 22399)]
  ../../../build-src/lisp/emacs-lisp/eieio.el: `eieio-object-name-string' is an obsolete generic function (as of 25.1); use `eieio-named' instead.
  ../../../build-src/lisp/emacs-lisp/eieio-base.el: `eieio-object-name-string' is an obsolete generic function (as of 25.1); use `eieio-named' instead.
  ../../../build-src/lisp/cedet/semantic/db-ref.el: Obsolete name arg "DEBUG" to constructor semanticdb-ref-adebug

  Thread 1 "emacs" received signal SIGSEGV, Segmentation fault.
  unchain_marker (marker=marker@entry=0x188d850) at ./debian/build-src/src/marker.c:605
  605     ./debian/build-src/src/marker.c: No such file or directory.
  (gdb) where
  #0  unchain_marker (marker=marker@entry=0x188d850) at ./debian/build-src/src/marker.c:605
  #1  0x000000000053608c in free_marker (marker=marker@entry=25745489)
      at ./debian/build-src/src/alloc.c:3850
  #2  0x0000000000508688 in signal_before_change (preserve_ptr=0x0, end_int=9894256, 
      start_int=9890072) at ./debian/build-src/src/insdel.c:2041
  ...

I wondered if the presence of the .git dir was altering the behavior of
autogen.sh (or something else) in a way that exposes the problem.

Hope this helps
-- 
Rob Browning
rlb @defaultvalue.org and @debian.org
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