bug#24109: 24.5; Long lines in message mode make Emacs irresponsive

[Yuri D'Elia <wavexx@thregr.org>]

[-- Attachment #1: Type: text/plain, Size: 2549 bytes --]

I've also stumbled on this bug when using mu4e.
I've rebuilt the current emacs from git (4961cc3f368d9114c305efe6243987bcfa3fd29b) with:

  '--with-x-toolkit=lucid' 'CFLAGS=-O0 -ggdb3'

I've used lucid as that's the normal tk I use. I managed to hang emacs the same
way I currently do on 24.5 (from debian), by scrolling through a *mu4e-headers*
view. C-g does nothing.

The backtrace is as follows:

#0  forward_to_next_line_start (it=0x7fffffff8960, skipped_p=0x7fffffff74be, bidi_it_prev=0x7fffffff6ba0)
    at xdisp.c:6244
#1  0x0000000000443cfa in reseat_at_next_visible_line_start (it=0x7fffffff8960, on_newline_p=false)
    at xdisp.c:6435
#2  0x000000000047053b in display_line (it=0x7fffffff8960) at xdisp.c:21175
#3  0x0000000000462fb3 in try_window (window=20150677, pos=..., flags=1) at xdisp.c:17290
#4  0x0000000000460334 in redisplay_window (window=20150677, just_this_one_p=true) at xdisp.c:16727
#5  0x0000000000459061 in redisplay_window_1 (window=20150677) at xdisp.c:14476
#6  0x00000000005e47f1 in internal_condition_case_1 (bfun=0x45901f <redisplay_window_1>, arg=20150677, 
    handlers=13786163, hfun=0x458f99 <redisplay_window_error>) at eval.c:1337
#7  0x000000000045849b in redisplay_internal () at xdisp.c:14101
#8  0x0000000000456325 in redisplay () at xdisp.c:13263
#9  0x000000000054f480 in read_char (commandflag=1, map=43265955, prev_event=0, 
    used_mouse_menu=0x7fffffffdbaf, end_time=0x0) at keyboard.c:2482
#10 0x000000000055c63c in read_key_sequence (keybuf=0x7fffffffdd60, bufsize=30, prompt=0, 
    dont_downcase_last=false, can_return_switch_frame=true, fix_current_buffer=true, 
    prevent_redisplay=false) at keyboard.c:9094
#11 0x000000000054cb9b in command_loop_1 () at keyboard.c:1370
#12 0x00000000005e4757 in internal_condition_case (bfun=0x54c791 <command_loop_1>, handlers=19104, 
    hfun=0x54bf7e <cmd_error>) at eval.c:1313
#13 0x000000000054c49b in command_loop_2 (ignore=0) at keyboard.c:1112
#14 0x00000000005e4089 in internal_catch (tag=46368, func=0x54c472 <command_loop_2>, arg=0) at eval.c:1079
#15 0x000000000054c43d in command_loop () at keyboard.c:1091
#16 0x000000000054bb63 in recursive_edit_1 () at keyboard.c:697
#17 0x000000000054bcda in Frecursive_edit () at keyboard.c:768
#18 0x0000000000549b5c in main (argc=1, argv=0x7fffffffe208) at emacs.c:1658

Lisp Backtrace:
"redisplay_internal (C function)" (0x0)

Emacs is stuck in try_window calling display_line, where the "it" parameter remains constant.
I'm attaching the output of *it in the email, hoping it might be useful.


[-- Attachment #2: it_ptr.txt --]
[-- Type: text/plain, Size: 12681 bytes --]

$4158 = {
  window = 20150677, 
  w = 0x1337990, 
  f = 0x1336980, 
  method = GET_FROM_BUFFER, 
  stop_charpos = 26551, 
  prev_stop = 26550, 
  base_level_stop = 26550, 
  end_charpos = 31953, 
  s = 0x0, 
  string_nchars = 0, 
  redisplay_end_trigger_charpos = 0, 
  multibyte_p = true, 
  header_line_p = true, 
  string_from_display_prop_p = false, 
  string_from_prefix_prop_p = false, 
  from_disp_prop_p = false, 
  ellipsis_p = false, 
  avoid_cursor_p = false, 
  dp = 0x21bbac0, 
  dpvec = 0x0, 
  dpend = 0x0, 
  dpvec_char_len = 0, 
  dpvec_face_id = 0, 
  saved_face_id = 11, 
  ctl_chars = {0 <repeats 16 times>}, 
  start = {
    pos = {
      charpos = 26551, 
      bytepos = 27815
    }, 
    overlay_string_index = -1, 
    string_pos = {
      charpos = -1, 
      bytepos = -1
    }, 
    dpvec_index = -1
  }, 
  current = {
    pos = {
      charpos = 26551, 
      bytepos = 27815
    }, 
    overlay_string_index = -1, 
    string_pos = {
      charpos = -1, 
      bytepos = -1
    }, 
    dpvec_index = -1
  }, 
  n_overlay_strings = 0, 
  overlay_strings_charpos = 26550, 
  overlay_strings = {0 <repeats 16 times>}, 
  string_overlays = {0 <repeats 16 times>}, 
  string = 0, 
  from_overlay = 0, 
  stack = {{
      string = 0, 
      string_nchars = 0, 
      end_charpos = 0, 
      stop_charpos = 0, 
      prev_stop = 0, 
      base_level_stop = 0, 
      cmp_it = {
        stop_pos = 0, 
        id = 0, 
        ch = 0, 
        rule_idx = 0, 
        lookback = 0, 
        nglyphs = 0, 
        reversed_p = false, 
        charpos = 0, 
        nchars = 0, 
        nbytes = 0, 
        from = 0, 
        to = 0, 
        width = 0
      }, 
      face_id = 0, 
      u = {
        image = {
          object = 0, 
          slice = {
            x = 0, 
            y = 0, 
            width = 0, 
            height = 0
          }, 
          image_id = 0
        }, 
        stretch = {
          object = 0
        }, 
        xwidget = {
          object = 0
        }
      }, 
      position = {
        charpos = 0, 
        bytepos = 0
      }, 
      current = {
        pos = {
          charpos = 0, 
          bytepos = 0
        }, 
        overlay_string_index = 0, 
        string_pos = {
          charpos = 0, 
          bytepos = 0
        }, 
        dpvec_index = 0
      }, 
      from_overlay = 0, 
      area = LEFT_MARGIN_AREA, 
      method = GET_FROM_BUFFER, 
      paragraph_embedding = NEUTRAL_DIR, 
      multibyte_p = false, 
      string_from_display_prop_p = false, 
      string_from_prefix_prop_p = false, 
      display_ellipsis_p = false, 
      avoid_cursor_p = false, 
      bidi_p = false, 
      from_disp_prop_p = false, 
      line_wrap = TRUNCATE, 
      voffset = 0, 
      space_width = 0, 
      font_height = 0
    }, {
      string = 0, 
      string_nchars = 0, 
      end_charpos = 0, 
      stop_charpos = 0, 
      prev_stop = 0, 
      base_level_stop = 0, 
      cmp_it = {
        stop_pos = 0, 
        id = 0, 
        ch = 0, 
        rule_idx = 0, 
        lookback = 0, 
        nglyphs = 0, 
        reversed_p = false, 
        charpos = 0, 
        nchars = 0, 
        nbytes = 0, 
        from = 0, 
        to = 0, 
        width = 0
      }, 
      face_id = 0, 
      u = {
        image = {
          object = 0, 
          slice = {
            x = 0, 
            y = 0, 
            width = 0, 
            height = 0
          }, 
          image_id = 0
        }, 
        stretch = {
          object = 0
        }, 
        xwidget = {
          object = 0
        }
      }, 
      position = {
        charpos = 0, 
        bytepos = 0
      }, 
      current = {
        pos = {
          charpos = 0, 
          bytepos = 0
        }, 
        overlay_string_index = 0, 
        string_pos = {
          charpos = 0, 
          bytepos = 0
        }, 
        dpvec_index = 0
      }, 
      from_overlay = 0, 
      area = LEFT_MARGIN_AREA, 
      method = GET_FROM_BUFFER, 
      paragraph_embedding = NEUTRAL_DIR, 
      multibyte_p = false, 
      string_from_display_prop_p = false, 
      string_from_prefix_prop_p = false, 
      display_ellipsis_p = false, 
      avoid_cursor_p = false, 
      bidi_p = false, 
      from_disp_prop_p = false, 
      line_wrap = TRUNCATE, 
      voffset = 0, 
      space_width = 0, 
      font_height = 0
    }, {
      string = 0, 
      string_nchars = 0, 
      end_charpos = 0, 
      stop_charpos = 0, 
      prev_stop = 0, 
      base_level_stop = 0, 
      cmp_it = {
        stop_pos = 0, 
        id = 0, 
        ch = 0, 
        rule_idx = 0, 
        lookback = 0, 
        nglyphs = 0, 
        reversed_p = false, 
        charpos = 0, 
        nchars = 0, 
        nbytes = 0, 
        from = 0, 
        to = 0, 
        width = 0
      }, 
      face_id = 0, 
      u = {
        image = {
          object = 0, 
          slice = {
            x = 0, 
            y = 0, 
            width = 0, 
            height = 0
          }, 
          image_id = 0
        }, 
        stretch = {
          object = 0
        }, 
        xwidget = {
          object = 0
        }
      }, 
      position = {
        charpos = 0, 
        bytepos = 0
      }, 
      current = {
        pos = {
          charpos = 0, 
          bytepos = 0
        }, 
        overlay_string_index = 0, 
        string_pos = {
          charpos = 0, 
          bytepos = 0
        }, 
        dpvec_index = 0
      }, 
      from_overlay = 0, 
      area = LEFT_MARGIN_AREA, 
      method = GET_FROM_BUFFER, 
      paragraph_embedding = NEUTRAL_DIR, 
      multibyte_p = false, 
      string_from_display_prop_p = false, 
      string_from_prefix_prop_p = false, 
      display_ellipsis_p = false, 
      avoid_cursor_p = false, 
      bidi_p = false, 
      from_disp_prop_p = false, 
      line_wrap = TRUNCATE, 
      voffset = 0, 
      space_width = 0, 
      font_height = 0
    }, {
      string = 0, 
      string_nchars = 0, 
      end_charpos = 0, 
      stop_charpos = 0, 
      prev_stop = 0, 
      base_level_stop = 0, 
      cmp_it = {
        stop_pos = 0, 
        id = 0, 
        ch = 0, 
        rule_idx = 0, 
        lookback = 0, 
        nglyphs = 0, 
        reversed_p = false, 
        charpos = 0, 
        nchars = 0, 
        nbytes = 0, 
        from = 0, 
        to = 0, 
        width = 0
      }, 
      face_id = 0, 
      u = {
        image = {
          object = 0, 
          slice = {
            x = 0, 
            y = 0, 
            width = 0, 
            height = 0
          }, 
          image_id = 0
        }, 
        stretch = {
          object = 0
        }, 
        xwidget = {
          object = 0
        }
      }, 
      position = {
        charpos = 0, 
        bytepos = 0
      }, 
      current = {
        pos = {
          charpos = 0, 
          bytepos = 0
        }, 
        overlay_string_index = 0, 
        string_pos = {
          charpos = 0, 
          bytepos = 0
        }, 
        dpvec_index = 0
      }, 
      from_overlay = 0, 
      area = LEFT_MARGIN_AREA, 
      method = GET_FROM_BUFFER, 
      paragraph_embedding = NEUTRAL_DIR, 
      multibyte_p = false, 
      string_from_display_prop_p = false, 
      string_from_prefix_prop_p = false, 
      display_ellipsis_p = false, 
      avoid_cursor_p = false, 
      bidi_p = false, 
      from_disp_prop_p = false, 
      line_wrap = TRUNCATE, 
      voffset = 0, 
      space_width = 0, 
      font_height = 0
    }, {
      string = 0, 
      string_nchars = 0, 
      end_charpos = 0, 
      stop_charpos = 0, 
      prev_stop = 0, 
      base_level_stop = 0, 
      cmp_it = {
        stop_pos = 0, 
        id = 0, 
        ch = 0, 
        rule_idx = 0, 
        lookback = 0, 
        nglyphs = 0, 
        reversed_p = false, 
        charpos = 0, 
        nchars = 0, 
        nbytes = 0, 
        from = 0, 
        to = 0, 
        width = 0
      }, 
      face_id = 0, 
      u = {
        image = {
          object = 0, 
          slice = {
            x = 0, 
            y = 0, 
            width = 0, 
            height = 0
          }, 
          image_id = 0
        }, 
        stretch = {
          object = 0
        }, 
        xwidget = {
          object = 0
        }
      }, 
      position = {
        charpos = 0, 
        bytepos = 0
      }, 
      current = {
        pos = {
          charpos = 0, 
          bytepos = 0
        }, 
        overlay_string_index = 0, 
        string_pos = {
          charpos = 0, 
          bytepos = 0
        }, 
        dpvec_index = 0
      }, 
      from_overlay = 0, 
      area = LEFT_MARGIN_AREA, 
      method = GET_FROM_BUFFER, 
      paragraph_embedding = NEUTRAL_DIR, 
      multibyte_p = false, 
      string_from_display_prop_p = false, 
      string_from_prefix_prop_p = false, 
      display_ellipsis_p = false, 
      avoid_cursor_p = false, 
      bidi_p = false, 
      from_disp_prop_p = false, 
      line_wrap = TRUNCATE, 
      voffset = 0, 
      space_width = 0, 
      font_height = 0
    }}, 
  sp = 0, 
  selective = 0, 
  what = IT_CHARACTER, 
  face_id = 0, 
  selective_display_ellipsis_p = true, 
  ctl_arrow_p = true, 
  face_box_p = false, 
  start_of_box_run_p = false, 
  end_of_box_run_p = false, 
  overlay_strings_at_end_processed_p = false, 
  ignore_overlay_strings_at_pos_p = false, 
  glyph_not_available_p = false, 
  starts_in_middle_of_char_p = false, 
  face_before_selective_p = false, 
  constrain_row_ascent_descent_p = false, 
  line_wrap = TRUNCATE, 
  base_face_id = 0, 
  c = 10, 
  len = 1, 
  cmp_it = {
    stop_pos = 26551, 
    id = -1, 
    ch = -2, 
    rule_idx = 0, 
    lookback = 0, 
    nglyphs = 0, 
    reversed_p = false, 
    charpos = 0, 
    nchars = 0, 
    nbytes = 0, 
    from = 0, 
    to = 0, 
    width = 0
  }, 
  char_to_display = 10, 
  glyphless_method = GLYPHLESS_DISPLAY_THIN_SPACE, 
  image_id = 0, 
  xwidget = 0x0, 
  slice = {
    x = 0, 
    y = 0, 
    width = 0, 
    height = 0
  }, 
  space_width = 0, 
  voffset = 0, 
  tab_width = 8, 
  font_height = 0, 
  object = 40630229, 
  position = {
    charpos = 26550, 
    bytepos = 27814
  }, 
  truncation_pixel_width = 9, 
  continuation_pixel_width = 0, 
  first_visible_x = 0, 
  last_visible_x = 946, 
  last_visible_y = 504, 
  extra_line_spacing = 0, 
  max_extra_line_spacing = 0, 
  override_ascent = -1, 
  override_descent = 0, 
  override_boff = 0, 
  glyph_row = 0x2bf8410, 
  area = TEXT_AREA, 
  nglyphs = 1, 
  pixel_width = 9, 
  ascent = 17, 
  descent = 3, 
  max_ascent = 0, 
  max_descent = 0, 
  phys_ascent = 10, 
  phys_descent = 0, 
  max_phys_ascent = 0, 
  max_phys_descent = 0, 
  current_x = 0, 
  continuation_lines_width = 0, 
  eol_pos = {
    charpos = 0, 
    bytepos = 0
  }, 
  current_y = 80, 
  first_vpos = 1, 
  vpos = 3, 
  hpos = 0, 
  left_user_fringe_bitmap = 0, 
  right_user_fringe_bitmap = 0, 
  left_user_fringe_face_id = 0, 
  right_user_fringe_face_id = 0, 
  bidi_p = true, 
  bidi_it = {
    bytepos = 27815, 
    charpos = 26551, 
    ch = 4194302, 
    nchars = 1, 
    ch_len = 2, 
    type = STRONG_L, 
    type_after_wn = STRONG_L, 
    orig_type = STRONG_L, 
    resolved_level = 0 '\000', 
    isolate_level = 0 '\000', 
    invalid_levels = 0, 
    invalid_isolates = 0, 
    prev = {
      charpos = 26550, 
      type = NEUTRAL_B, 
      orig_type = NEUTRAL_B
    }, 
    last_strong = {
      charpos = 26549, 
      type = UNKNOWN_BT, 
      orig_type = UNKNOWN_BT
    }, 
    next_for_neutral = {
      charpos = -1, 
      type = UNKNOWN_BT, 
      orig_type = UNKNOWN_BT
    }, 
    prev_for_neutral = {
      charpos = 26550, 
      type = STRONG_L, 
      orig_type = STRONG_L
    }, 
    next_for_ws = {
      charpos = -1, 
      type = UNKNOWN_BT, 
      orig_type = UNKNOWN_BT
    }, 
    bracket_pairing_pos = -1, 
    bracket_enclosed_type = UNKNOWN_BT, 
    next_en_pos = 0, 
    next_en_type = UNKNOWN_BT, 
    sos = L2R, 
    scan_dir = 1, 
    disp_pos = 26795, 
    disp_prop = 0, 
    stack_idx = 0, 
    level_stack = {{
        next_for_neutral_pos = 0, 
        next_for_neutral_type = 0, 
        last_strong_type = 0, 
        prev_for_neutral_type = 0, 
        level = 0 '\000', 
        flags = 0 '\000'
      } <repeats 128 times>}, 
    string = {
      lstring = 0, 
      s = 0x0, 
      schars = 0, 
      bufpos = 0, 
      from_disp_str = false, 
      unibyte = false
    }, 
    w = 0x1337990, 
    paragraph_dir = L2R, 
    separator_limit = -1, 
    first_elt = false, 
    new_paragraph = false, 
    frame_window_p = true
  }, 
  paragraph_embedding = NEUTRAL_DIR
}