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Avoid infloop in 'format-mode-line'

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* src/xdisp.c (decode_mode_spec): Don't use W->start if it is
outside of the buffer's accessible region.  (Bug#42220)
This commit is contained in:
Eli Zaretskii 2020-07-07 17:08:19 +03:00
parent 247dcb4b1b
commit 71fc003860
1 changed files with 16 additions and 0 deletions
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16
src/xdisp.c
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@ -26342,6 +26342,22 @@ decode_mode_spec (struct window *w, register int c, int field_width,
startpos = marker_position (w->start);
startpos_byte = marker_byte_position (w->start);
height = WINDOW_TOTAL_LINES (w);
/* We cannot cope with w->start being outside of the
accessible portion of the buffer; in particular,
display_count_lines call below will infloop if called with
startpos_byte outside of the [BEGV_BYTE..ZV_BYTE] region.
Such w->start means we were called in some "creative" way
when the buffer's restriction was changed, but the window
wasn't yet redisplayed after that. If that happens, we
need to determine a new base line. */
if (!(BUF_BEGV_BYTE (b) <= startpos_byte
&& startpos_byte <= BUF_ZV_BYTE (b)))
{
startpos = BUF_BEGV (b);
startpos_byte = BUF_BEGV_BYTE (b);
w->base_line_pos = 0;
w->base_line_number = 0;
}
/* If we decided that this buffer isn't suitable for line numbers,
don't forget that too fast. */