Hrvoje Niksic <hniksic(a)srce.hr&gt; writes: I can't reproduce this, but it looks similar to crashes Simon Josefsson (in <ilulnipy61u.fsf(a)xiphias.pdc.kth.se>) and Colin Rafferty (in <vgvogiwhqqz.fsf(a)ms.com>) have reported before. Martin has rewritten mapcar1() last year. The changes relevant here seem to be that fn and seq are no longer GCPRO'd as before (see fns.c:3174 in 20.4) and that Ffuncall is used directly instead of going via call1. This latter change implies that the two arguments (the function and the element) are not GCPRO'd anymore (that's what the callx functions do). GCPROing should not be necessary because of "caller gcpros" but we are not protecting in the caller either (Fmapconcat only protects its third argument sep for some reason). Actually the caller of Fmapconcat should do it (execute_optimized_program() presumably). I suggest someone who *can* reproduce the problem adds some GCPROs and checks whether they make a difference. Otherwise please post a backtrace of a crash from a debug non-optimised build. Martin, are you still reading xemacs-beta? any comments? Gunnar -- Gunnar Evermann Speech, Vision & Robotics Group Engineering Department Cambridge University