I was trying to debug another bug by putting a debug_print(tag) into Fthrow, when temacs starts to sigsegv while dumping. After a few hours bug tracing I found inhibit_non_essential_conversion_operations changes while print_internal in print.c is active. I'm not sure which function down the call path makes this change, but actually, I think print_internal should not be sensitive to such a change, whether the sub-functions of print_internal are allowed to change inhibit_..._operations or not. This patch saves a local copy of inhibit_.._operations on the stack, so the behaviour is guaranteed to be consistant across the whole stack frame lifetime of print_internal. Inconsistant behaviour results in an unbind_to(specdepth = 0), which results in a crash.. Diffed against sjt-xft. Index: ChangeLog =================================================================== RCS file: /pack/xemacscvs/XEmacs/xemacs/src/ChangeLog,v retrieving revision 1.758.2.27 diff -u -r1.758.2.27 ChangeLog --- ChangeLog 2005/09/20 16:05:56 1.758.2.27 +++ ChangeLog 2005/09/22 13:13:11 ＠＠ -1,3 +1,10 ＠＠ +2005-09-22 Clemens Fruhwirth <clemens(a)endorphin.org&gt; + + * print.c (print_internal): Incorrectly calls unbind_to, when + inhibit_non_essential_conversion_operations is changed while this + function is active. Hence, save a local copy of this variable when + entering print_internal. + 2005-09-14 Stephen J. Turnbull <stephen(a)xemacs.org&gt; * XEmacs 21.5.22 "cucumber" is released. Index: print.c =================================================================== RCS file: /pack/xemacscvs/XEmacs/xemacs/src/print.c,v retrieving revision 1.51.2.3 diff -u -r1.51.2.3 print.c --- print.c 2005/07/13 04:46:55 1.51.2.3 +++ print.c 2005/09/22 13:13:15 ＠＠ -1541,6 +1541,7 ＠＠ { /* This function can GC */ int specdepth = 0; + int local_inhibit_non_ess_conv_ops = inhibit_non_essential_conversion_operations; struct gcpro gcpro1, gcpro2; QUIT; ＠＠ -1586,7 +1587,7 ＠＠ /* Avoid calling internal_bind_int, which conses, when called from debug_prin1. In that case, we have bound print_depth to 0 anyway. */ - if (!inhibit_non_essential_conversion_operations) + if (!local_inhibit_non_ess_conv_ops) { specdepth = internal_bind_int (&print_depth, print_depth + 1); ＠＠ -1679,7 +1680,7 ＠＠ debug_print() or we're already crashing. In such cases, (further) crashing is counterproductive. */ - if (inhibit_non_essential_conversion_operations && + if (local_inhibit_non_ess_conv_ops && !debug_can_access_memory (lheader, sizeof (*lheader))) { write_fmt_string (printcharfun, "#<EMACS BUG: BAD MEMORY %p>", ＠＠ -1725,7 +1726,7 ＠＠ (e.g. under Unix we typically have to set a SIGSEGV handler and try to trigger a seg fault). */ - if (inhibit_non_essential_conversion_operations) + if (local_inhibit_non_ess_conv_ops) { if (!debug_can_access_memory (lheader, detagged_lisp_object_size (lheader))) ＠＠ -1768,7 +1769,7 ＠＠ } } - if (!inhibit_non_essential_conversion_operations) + if (!local_inhibit_non_ess_conv_ops) unbind_to (specdepth); UNGCPRO; }