bug#3521: 23.0.94; process-send-region errors / bug#2272 strikes again

[David Engster <deng@randomsample.de>]

Tassilo Horn <thorn@fastmail.fm> writes:
> Evaluating this code once again triggers an error (I already reported it
> in bug 2272 some times ago, and it was fixed and the bug closed):

[...]

> Here's the backtrace:

[...]

> This time I cannot reproduce this easily with emacs -Q, but with my
> usual config it always happens.  But the test case above uses only very
> low-level functions which shouldn't be influenced by any customization
> anyway, right?  At none of them is redefined or adviced by me...

I can confirm this bug, and I think I've found the culprit:
'display-time'. At least that one always triggers the bug for me. It
seems this happens when the modeline gets updated (i.e. at the full
minute).

Therefore, use this recipe to reproduce the bug:

* emacs -Q
* M-x display-time RET
* Evaluate the code Tassilo posted
* The error will appear at the next full minute.

Tassilo, if you do not have (display-time) in your .emacs, look for
other stuff that could update the modeline in the background.

-David