bug#32438: 26.1; Long command in shell-mode results in ^G being displayed

[charles@aurox.ch (Charles A. Roelli)]

> From: Svend Sorensen <svend@svends.net>
> Date: Tue, 14 Aug 2018 09:39:52 -0700
> 
> To reproduce:
> 
> emacs -Q
> 
> M-x [execute-extended-command]
> s [self-insert-command]
> h [self-insert-command]
> e [self-insert-command]
> l [self-insert-command]
> l [self-insert-command]
> <return> [minibuffer-complete-and-exit]
> t [self-insert-command]
> r [self-insert-command]
> u [self-insert-command]
> e [self-insert-command]
> SPC [self-insert-command]
> C-u [universal-argument]
> 1 [digit-argument]
> 0 [digit-argument]
> 1 [digit-argument]
> 9 [digit-argument]
> a [self-insert-command]
> <return> [comint-send-input]
> 
> Expected result:
> 
> New shell prompt displayed with no output from "true" command:
> 
> $ true aaa...
> $
> 
> Actual result:
> 
> ^G displayed, pressing enter results in ^G again.
> 
> $ true aaa...
> ^G
> ^G
> 
> 
> In GNU Emacs 26.1 (build 2, x86_64-apple-darwin17.7.0, NS appkit-1561.60 Version 10.13.6 (Build 17G65))
>  of 2018-07-31 built on 200956
> Windowing system distributor 'Apple', version 10.3.1561

Thanks for reporting this.  It occurs for me in macOS in every version
of Emacs starting from 24.3, but not in version 23.4.  There must have
been a regression in between those two versions.