Damon Lipparelli <lipp(a)primus.com&gt; writes: I assume you mean line 3186? Which version of alloc.c are you using anyway? The line numbers in your backtrace look like the latest one from CVS, i.e. including Martin's patch after 21.0-b65? I am afraid I just realized that the gdb commands cannot currently handle marked lrecords properly (at least for !USE_INDEXED_LRECORD_IMPLEMENTATION), so if you mean by 'corrupted' that pobj say 'unknown Lisp_Object' then that is expected :-( I noted below the following line numbers what kind of object is about to be marked at each point in your backtrace: Lisp_Type_Record marker function Lisp_Type_symbol sym->value Lisp_Type_Vector element i staticvec[i] If I read this right we're trying to mark a chartable which is the value of a symbol which is an element of a Vector which is staticpro'd. Could you check what this vector contains? possibly before the actual marking? Presumably it is already corrupted before the GC -- do you always get the crash on marking this particular vector? Then you might want to try the watchpoint or always_gc stuff Martin mentioned... FWIW I have an additional report of such a crash under 21.0b65... -- Gunnar Evermann Speech, Vision & Robotics Group Engineering Department Cambridge University