My primary systems are Fedora 25 and Ubuntu 14, and latest xemacs runs fine there. (One minor nit:  menus are displayed with strange colors and backgrounds. I worked around that by using --with-xft=emacs,menubars.)

However, I've been trying to build on 26 and 17.10.  (And some random Debian test at work).  It doesn't work.

On fedora 26 and ubuntu, I configure using --with-mule --with-xft=emacs,menubars

In both systems, I gt errors that __getpagesize is implicitly declared and that sbrk has conflicting types.

I just removed the erroneous declaration of sbrk (in favor of the definition from unistd.h), and just changed __getpagesize to getpagesize.  This allows compile to finish, but running

xemacs -no-packages -batch -no-autoloads -l update-elc-2.el -f batch-update-elc-2

causes a segfault.  Indeed, just src/xemacs segfaults.

Any ideas?  Configuring with --with-system-malloc gets around the problem but it still segfaults in the same place.