bug#30059: 25.3; Wrong value for comint-process-echoes will cause comint-send-input to hang

[Richard Sharman]

I’ve been hit by this a few times and it’s quite annoying.  Starting from emacs 
-Q evaluate the following 2 lines

(setq comint-process-echoes t)
(shell)

then at the shell command enter “cat -n” .  This completely locks up emacs (at 
least under macos 10.13);  control-G and control-C have no effect; the emacs 
process has to be killed.



In GNU Emacs 27.1 (build 2, x86_64-apple-darwin17.7.0, NS appkit-1561.61 
Version 10.13.6 (Build 17G14033))
 of 2020-12-13 built on henry.local
Windowing system distributor 'Apple', version 10.3.1561
System Description:  Mac OS X 10.13.6