bootstrap problem with union Lisp_Object

[Ken Raeburn]

I'm still trying to track this down, but just for the record: If I  
build recent sources with CC='gcc -DENABLE_CHECKING - 
DUSE_LISP_UNION_TYPE', bootstrapping fails:

Compiling /var/raeburn/emacs-hacking/fsf/source/lisp/emacs-lisp/byte- 
opt.el
Error: Invalid function: 4
Error: Invalid function: 4
Error: Invalid function: 4
Error: Invalid function: 4
Error: Invalid function: 4
Error: Invalid function: 4

In toplevel form:
../../source/lisp/emacs-lisp/byte-opt.el:186:1:Error: Invalid  
function: 4
../../source/lisp/emacs-lisp/byte-opt.el:186:1:Error: Invalid  
function: 4
../../source/lisp/emacs-lisp/byte-opt.el:186:1:Error: Invalid  
function: 4
../../source/lisp/emacs-lisp/byte-opt.el:186:1:Error: Invalid  
function: 4
../../source/lisp/emacs-lisp/byte-opt.el:186:1:Error: Invalid  
function: 4
../../source/lisp/emacs-lisp/byte-opt.el:186:1:Error: Invalid  
function: 4
../../source/lisp/emacs-lisp/byte-opt.el:186:1:Error: Invalid  
function: 4
make[2]: *** [compile] Error 1

With the usual (integral) Lisp_Object type, bootstrapping works fine.

Ken