Thank you, Paul, for taking the time to try and reproduce the behavior that I am experiencing on my end. I am assuming that this round of tests is with a current version of the master branch (0b8117ed1abfc17bb0bc1690a8997736f1e8f98c) and _after_ applying the x.diff patch. I built the Emacs master branch (current version) without any modifications so that the build could complete without errors, and then I applied the x.diff patch and built again and then performed the gdb test. The build with the patch will crash on my end when garbage collection occurs; however, the ptype test is able to complete and I have attached a gdb printout 0b8117ed1abfc17bb0bc1690a8997736f1e8f98c.txt. The current issue is beyond my current level of programming abilities to resolve, so other than performing a standard M-x diff between your ptype test (relabeled as ptype_by_paul.txt) and my own test (0b8117ed1abfc17 bb0bc1690a8997736f1e8f98c.txt), I would need further guidance regarding how best to be of assistance. My setup on Windows XP SP-3 didn't recognize a build option of -m32, so I just used the same old build options that I have used previously; i.e.,: CFLAGS='-O0 -g3' ./configure \ --enable-checking='yes,glyphs' \ --enable-check-lisp-object-type \ --without-compress-install \ --without-makeinfo \ --with-gnutls=no \ --with-mailutils \ --without-makeinfo Keith ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; > Date: [04-07-2019 22:23:07] <7 Apr 2019 22:23:07 -0700> > From: Paul Eggert > To: Keith David Bershatsky > Cc: emacs-devel@gnu.org, Stefan Monnier , > Andreas Schwab , Alan Mackenzie , > Daniel Colascione > Subject: Re: buffer.c/buffer.h: How to add new buffer-local variables? > > Keith David Bershatsky wrote: > > Perhaps there is something that may stand out (to a trained programmer) in the 01/31/2019 commit .... > > It did change the buffer struct layout, so it's a good candidate for a culprit. > > For what it's worth, I cannot reproduce the problem in a 32-bit build under Fedora 29 x86-64 (GCC 8.3.1). I configured this way: > > ./configure CC=gcc -m32 -march=native --enable-gcc-warnings --without-imagemagick --without-gif --with-modules --enable-checking=yes,glyphs --enable-check-lisp-object-type --with-gnutls=no > > and built Emacs master with the attached patch x.diff. > > My guess is that the problem has something to do with the unportable assumptions we've long made about struct buffer layout. I am attaching ptype.txt, the output of the GDB command "ptype /o current_buffer" that Eli suggested; please compare it to your ptype output.