bug#39075: 28.0.50; Emacs hangs on 100% CPU and grows beyond bounds in shell-mode

[Pieter van Oostrum]

Eli Zaretskii <eliz@gnu.org> writes:

>> Date: Fri, 10 Jan 2020 22:16:58 +0100
>> From: Pieter van Oostrum <pieter@vanoostrum.org>
>> 
>> 1) Emacs -Q
>> 2) M-x shell
>> 3) type some command, and use some filename completions on the way
>> (using TAB).
>> 4) Type a semicolon (;)
>> 
>> Now Emacs hangs, the ; does not appear, and it doesn't react to a C-g typed.
>> It uses 100% CPU and memory grows beyond bounds, eventually just making
>> my whole computer unresponsive.
>
> I cannot reproduce this on GNU/Linux, so it's probably macOS-specific.

It's not so clear what could be MacOS-specific.

I ran it under gdb, and interrupted it several times with C-z in gdb. Most of 
the stack traces were in the garbage collector, suggesting that it is 
collecting like crazy. This doesn't surprise me, as it is constantly allocating 
new memory. The rest of this stack trace doesn't have useful information.

I managed to get a stack trace where it is processing. I haven't analysed these 
yet, but I include both here.

semicolon-emacs-loop
Description: stack traces

-- 
Pieter van Oostrum
www: http://pieter.vanoostrum.org/
PGP key: [8DAE142BE17999C4]