`shell-resync-dir' hangs

[Jens Schmidt]

This bug report will be sent to the Free Software Foundation,
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Please write in English, because the Emacs maintainers do not have
translators to read other languages for them.

In GNU Emacs 20.7.1 (i386-*-nt4.0.1381)
 of Tue Jun 13 2000 on buffy
configured using `configure NT'

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

`shell-resync-dir' hangs if `comint-truncate-buffer' is in
`comint-output-filter-functions' and the shell buffer is at its
maximum size.

The reason is the following `while'-loop in `shell-resync-dir':

    (let ((pt (point))) ; wait for 1 line
      ;; This extra newline prevents the user's pending input from spoofing us.
      (insert "\n") (backward-char 1)
      (while (not (looking-at ".+\n"))
        (accept-process-output proc)
        (goto-char pt)))

In the scenario described above, calling `accept-process-output'
triggers `comint-truncate-buffer' which removes text *before* the
location `pt' point to.  As a result, `pt' points to (for
example) after `(point-max)', so the `looking-at' never
recognizes that process output has been inserted.  Another
variant may be that `pt' point to the middle of the process
output, leading to incorrect results.

Making `pt' a marker does not help, since `comint-output-filter'
uses `insert-before-markers' to insert its text.

A possible solution would be to replace the expression
`(goto-char pt)' by `(goto-char comint-last-output-start)' and
remove the surrounding `let' alltogether, but I am not sure about
correctness of this one.  However, I'll try it as a workaround.

Regards

Jens