* arm-tdep.c (arm_stub_unwind_sniffer): Add comment.

gdb/ChangeLog

@@ -1,3 +1,7 @@
+2010-03-04  Doug Evans  <dje@google.com>
+
+	* arm-tdep.c (arm_stub_unwind_sniffer): Add comment.
+
 2010-03-04  Pedro Alves  <pedro@codesourcery.com>
 
 	* breakpoint.c (update_watchpoint): Create a sentinel location if

gdb/arm-tdep.c

@@ -1236,6 +1236,8 @@ arm_stub_unwind_sniffer (const struct frame_unwind *self,
 
   addr_in_block = get_frame_address_in_block (this_frame);
   if (in_plt_section (addr_in_block, NULL)
+      /* We also use the stub winder if the target memory is unreadable
+	 to avoid having the prologue unwinder trying to read it.  */
       || target_read_memory (get_frame_pc (this_frame), dummy, 4) != 0)
     return 1;