On 2012-05-08 11:37 +0800, Chong Yidong wrote:
> I also am puzzled by where the display string "!" causing the problem
> comes from.  The only appearance of a "!" in Flymake is applied to the
> mode-line, not as a display string within the buffer text.  Neither
> Flymake nor Python mode seem to use overlay display strings.
>
> Do you have any idea what "!" is used for in your buffer?

Just realised this was triggered by me patching flymake to support
fringe indicator.

> Could you check the value of it->object, it->n_overlay_strings, and
> it->overlay_strings[0]?

On 2012-05-09 01:26 +0800, Eli Zaretskii wrote:
> I think Leo's time and energy will be better spent looking for a
> reproducible test case.  Then debugging will be much more efficient.

OK, I have prepared a test case. It requires python and the package
pyflakes¹ which is used by flymake. Normally one can install pyflakes by
using:

    pip install pyflakes
OR
    easy_install pyflakes

in a terminal.

Decompress the attached tar ball and go into the directory 11417/ in a
terminal and launch emacs like this:

 emacs -nw -q -L . -l bug.el setup.py

You should see a buffer with contents partially displayed. Move around
in that buffer by typing C-v, M-v, C-n or C-p until it freezes (it
usually takes me no more than 3 key strokes).

Footnotes: 
¹  http://pypi.python.org/pypi/pyflakes/0.5.0