Hello, I am running emacs 25.1 on a fully updated Fedora 25 linux. I have stumbled upon the bug when editing the attached file and I can not figure out the issues. In the above file, if I go to before "Usage..." and start typing anything, including whitespace, emacs crashes. Here is gdb output with bt full and backtrace. (gdb) bt full #0 0x000000000053af6b in re_match_2_internal () #1 0x000000000053850a in fast_looking_at () #2 0x00000000004a983b in bidi_at_paragraph_end () #3 0x00000000004ada9f in bidi_move_to_visually_next () #4 0x00000000004446b0 in set_iterator_to_next () #5 0x000000000044eafe in display_line () #6 0x0000000000451268 in try_window () #7 0x000000000046544e in redisplay_window () #8 0x000000000046852b in redisplay_window_0 () #9 0x00000000005644be in internal_condition_case_1 () #10 0x000000000043227d in redisplay_windows () #11 0x0000000000454dd9 in redisplay_internal () #12 0x00000000004fb44b in read_char () #13 0x00000000004fdf3d in read_key_sequence.constprop () #14 0x00000000004ffb84 in command_loop_1 () #15 0x0000000000564432 in internal_condition_case () #16 0x00000000004f1614 in command_loop_2 () #17 0x00000000005643d3 in internal_catch () #18 0x00000000004f15d0 in command_loop () #19 0x00000000004f5dd7 in recursive_edit_1 () #20 0x00000000004f6128 in Frecursive_edit () #21 0x0000000000419d52 in main () (gdb) backtrace #0 0x000000000053af6b in re_match_2_internal () #1 0x000000000053850a in fast_looking_at () #2 0x00000000004a983b in bidi_at_paragraph_end () #3 0x00000000004ada9f in bidi_move_to_visually_next () #4 0x00000000004446b0 in set_iterator_to_next () #5 0x000000000044eafe in display_line () #6 0x0000000000451268 in try_window () #7 0x000000000046544e in redisplay_window () #8 0x000000000046852b in redisplay_window_0 () #9 0x00000000005644be in internal_condition_case_1 () #10 0x000000000043227d in redisplay_windows () #11 0x0000000000454dd9 in redisplay_internal () #12 0x00000000004fb44b in read_char () #13 0x00000000004fdf3d in read_key_sequence.constprop () #14 0x00000000004ffb84 in command_loop_1 () #15 0x0000000000564432 in internal_condition_case () #16 0x00000000004f1614 in command_loop_2 () #17 0x00000000005643d3 in internal_catch () #18 0x00000000004f15d0 in command_loop () #19 0x00000000004f5dd7 in recursive_edit_1 () #20 0x00000000004f6128 in Frecursive_edit () #21 0x0000000000419d52 in main () Note that I have no command for xbacktrace. (gdb) xbacktrace Undefined command: "xbacktrace". Try "help". This has really been a major block for me. So, I was wondering if anyone can help track down the error. Please feel free to ask questions if something is not clear. Thanks again! Best wishes, Ranjan -- Ranjan Maitra