I get reproducable crashes with various betas (21.0-b57, 21.0-prelim, 21.2-b2) and optimization. The strange things is that these errors which are reported as Pid 5479 killed due to trashed stack. Pid 5479 was killed due to failure in writing the signal context. [2] Illegal instruction /opt/src/xemacs-21.0-b57/src/xemacs -f vm (core dumped) are always placed around calls to make_uninit_string () (gdb) where #0 0xc00f2240 in _brk () from /usr/lib/libc.2 #1 0xc00fb514 in sbrk () from /usr/lib/libc.2 #2 0x24bb98 in __default_morecore () #3 0x24a3d8 in morecore () #4 0x24aca8 in malloc () #5 0x62b90 in make_uninit_string () #6 0x632d8 in make_string () #7 0x14afb8 in 291_12d6_cl_concat () #8 0xc0 in TBS$pngrtran () #9 0xc00fb514 in sbrk () from /usr/lib/libc.2 (gdb) where #0 0x62b24 in make_uninit_string () #1 0x632d8 in make_string () #2 0x14afb8 in 291_12d6_cl_concat () #3 0x40177014 in ?? () #4 0x632d8 in make_string () Are there any related problems known so far? --Marcus BTW, any reason why --error-checking=all doesn't work with configure anymore?