bug#1082: 23.0.60; read-char unexpectedly halts execution of script

["Lennart Borgman (gmail)" <lennart.borgman@gmail.com>]

Chong Yidong wrote:
>> Let filter.el consist of the forms:
>>
>>    (defun bc-filter (proc string)
>>      (message "%s" string))
>>
>>    (message "starting")
>>    (setq bc (start-process "bc" nil "/usr/bin/bc"))
>>    (set-process-filter bc 'bc-filter)
>>
>>    (while t
>>      (let ((char (read-char nil nil 0.1)))
>>        (message "char: %s" char)))
>>
>> Where "/usr/bin/bc" is the GNU arbitrary precision calculator. Now:
>>
>>    mt-computer:~ mt$ emacs --script filter.el
>>    starting
>>    mt-computer:~ mt$
>>
>> I expect non-termination in this case, as in eval-buffer on filter.el.
> 
> This broke when SYNC_INPUT became the default; it works when Emacs is
> recompiled without SYNC_INPUT, like Emacs 22.
> 
> I don't know what the specific cause of failure is, however.  Maybe the
> SYNC_INPUT code should only be active when Emacs is run interactively.
> 
> Thoughts?


What is the while loop supposed to do? I tested just that and I got a
bit weird results.