Didier> * gdb xemacs Didier> * break Fmake_device Didier> * run -vanilla Didier> Breakpoint 1, Fmake_device (type=-268435457, connection=-1606340604, Didier> props=-1606340604) at device.c:504 Didier> * call debug_print (type) Didier> #<EMACS BUG: ILLEGAL DATATYPE (#o 7) Save your buffers immediately and please Didier> report this bug> Didier> What's going on ? Martin, any idea ? If you have a proper .gdbinit (see src/gdbinit), you should get: (martin＠lasker) ~//build/mde/src $ dv. GNU gdb 4.17 ... (gdb) br Fmake_device Breakpoint 1 at 0x80a7788: file /home/martin/x/dev/src/device.c, line 504. (gdb) run -vanilla Starting program: /home/martin/x/build/mde/src/./xemacs -vanilla Breakpoint 1, Fmake_device (type={...}, connection={...}, props={...}) at /home/martin/x/dev/src/device.c:504 504 Lisp_Object device = Qnil; (gdb) pobj type $1 = (struct Lisp_Symbol *) 0x83af18c $2 = {lheader = {type = 5, mark = 0, pure = 0}, next = 0x0, name = 0x8281ce8, value = {...}, function = {...}, obarray = {...}, plist = {...}} Symbol name: x (gdb) ldp type Lisp => x