unexec causes crash in Xt [was: Re: XEmacs 21.1 CVS updates]

[ Alexandre, are you reading xemacs-beta? this crash occurs with the latest 21.1 version in CVS, i.e. including your patch <orbt8826hb.fsf(a)garnize.lsd.ic.unicamp.br&gt; ] Gunnar Evermann <ge204(a)eng.cam.ac.uk&gt; writes: OK, I have looked a bit closer at this and now I could use some help. first of all this X crash is indeed a dumping problem. run-temacs works fine even under X. All the following info is gleamed from a debug build on IRIX64 ruby 6.2 06101031 IP28 mips with gcc version 2.7.2.3 linking against X11R6.4 and NOT using motif. The phenomenon of temacs working and xemacs crashing is the same on the IRIX6.5/SGIcc build mentioned previously. The crash occurs in X11R6.4's XtInitializeWidgetClass() at the following place: ----- XtInitializeWidgetClass(wc) WidgetClass wc; { [...snip by ge...] WidgetClass pc; #define LeaveIfClass(c, d) if (pc == c) { inited = d; break; } for (pc = wc; pc; pc = pc->core_class.superclass) ------ the wc is actually our topLevelEmacsShellClassRec. In temacs directly before calling unexec it looks like this: $1 = {core_class = {superclass = 0x40ebcf4, class_name = 0x101285e0 "TopLevelEmacsShell", ... even after unexec() finishes it's the same. Now if I use 'gdb xemacs' and then immediately (i.e. before running) print it again it's still the same. Now I put a breakpoint at main() and 'run -vanilla' and it has changed to: $2 = {core_class = {superclass = 0xa81dbcf4, class_name = 0x101285e0 "TopLevelEmacsShell", ... i.e. the first two bytes were overwritten! As I have no clue what exactly is happening when a program is loaded/started I would appreciate some hints from the experts :-) Feel free to request more info or to provide instructions what to check. Please note that we have received a couple of reports of similar crashes (i.e. same C backtrace) from people using Solaris 7. Gunnar