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[RFA] Fix inline frame crash in handle_inferior_event


 Jan's recent change to enable mcheck has triggered a segfault in 
gdb.opt/inline-cmds.exp on mips-sde-elf and mips-linux-gnu targets (any 
multilibs).  I have tracked the problem down to dereferencing a pointer to 
a frame structure that has been already freed.  The cause is in 
handle_inferior_event, where skip_inline_frames is called and that may 
invalidate the frame cache.  That doesn't stop handle_inferior_event 
though from trying to use a stale pointer to the current frame structure 
in the next step.  This path is only used for targets that have delay 
slots (gdbarch_single_step_through_delay_p is true; that applies to CRIS 
and MIPS targets only), which I infer is why it wasn't caught straight 
away.  This must be a long-standing bug.

 The change below works for me, the gdbarch_single_step_through_delay_p 
check that guards the problematic pointer dereference uses gdbarch 
determined by the invalidated frame too, so I've decided to reinit both 
frame and gdbarch unconditionally.

 No regressions in mips-sde-elf, mips-linux-gnu or i686-linux-gnu targets.  

 OK to apply?

2012-06-13  Maciej W. Rozycki  <>

	* infrun.c (handle_inferior_event): Re-fetch frame and gdbarch
	after hiding inline functions.


Index: gdb-fsf-trunk-quilt/gdb/infrun.c
--- gdb-fsf-trunk-quilt.orig/gdb/infrun.c	2012-06-08 23:45:43.000000000 +0100
+++ gdb-fsf-trunk-quilt/gdb/infrun.c	2012-06-12 08:29:31.063547656 +0100
@@ -4084,7 +4084,13 @@ handle_inferior_event (struct execution_
                && pc_at_non_inline_function (aspace,
-	skip_inline_frames (ecs->ptid);
+	{
+	  skip_inline_frames (ecs->ptid);
+	  /* Re-fetch current thread's frame in case that invalidated
+	     the frame cache.  */
+	  frame = get_current_frame ();
+	  gdbarch = get_frame_arch (frame);
+	}
   if (ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP

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