XEmacs on Fedora 26, Ubuntu 17.10

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. -- Ray