bug#6800: 23.1; EOT / ^D inserted into comint input string

bug#6800: 23.1; EOT / ^D inserted into comint input string

[David Fox]

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When an input longer than 255 characters is typed into comint (or
shell) an EOT character (ascii 4, ^D) is inserted into the string.
This can cause an error depending how the sub process handles these
extra characters.  For example, GHC doesn't like it when an EOT
appears inside of a string:

 ghci
 > Prelude> putStrLn "<a 241 character string>"
works fine, but
 > Prelude> putStrLn "<a 242 character string>"
<interactive>:1:255: lexical error at character '\EOT'

I inserted a function to break up the input into comint-send-string to work
around the problem:

(require 'comint)

(defun comint-send-string (process string)
  "Like `process-send-string', but also does extra bookkeeping for Comint
mode."
  (if process
      (with-current-buffer (if (processp process)
                   (process-buffer process)
                 (get-buffer process))
    (comint-snapshot-last-prompt))
    (comint-snapshot-last-prompt))
  (my-process-send-string process string))

;; Break up the string so that we don't get EOT characters in our input
stream.
(defun my-process-send-string (process string)
  (if (> (length string) 200)
      (progn (process-send-string process (substring string 0 200))
(my-process-send-string process (substring string 200)))
    (process-send-string process string)))

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bug#6800: 23.1; EOT / ^D inserted into comint input string

[Stefan Monnier]

> When an input longer than 255 characters is typed into comint (or
> shell) an EOT character (ascii 4, ^D) is inserted into the string.
> This can cause an error depending how the sub process handles these
> extra characters.  For example, GHC doesn't like it when an EOT
> appears inside of a string:

I believe this bug is fixed on the Emacs trunk (to become Emacs-24), but
the fix may introduce other problems.  Apparently nobody knows how to
fix it right and there is about as much as no documentation at all on
this part of the behavior of ttys.


        Stefan

bug#6800: 23.1; EOT / ^D inserted into comint input string

[Alan Third]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> When an input longer than 255 characters is typed into comint (or
>> shell) an EOT character (ascii 4, ^D) is inserted into the string.
>> This can cause an error depending how the sub process handles these
>> extra characters.  For example, GHC doesn't like it when an EOT
>> appears inside of a string:
>
> I believe this bug is fixed on the Emacs trunk (to become Emacs-24), but
> the fix may introduce other problems.  Apparently nobody knows how to
> fix it right and there is about as much as no documentation at all on
> this part of the behavior of ttys.

IIRC this code is no longer in Emacs. I'll close this bug.

-- 
Alan Third

bug#6800: 23.1; EOT / ^D inserted into comint input string

[David Fox]

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On Fri, Aug 12, 2016 at 11:36 AM, Alan Third <alan@idiocy.org> wrote:

> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
> >> When an input longer than 255 characters is typed into comint (or
> >> shell) an EOT character (ascii 4, ^D) is inserted into the string.
> >> This can cause an error depending how the sub process handles these
> >> extra characters.  For example, GHC doesn't like it when an EOT
> >> appears inside of a string:
> >
> > I believe this bug is fixed on the Emacs trunk (to become Emacs-24), but
> > the fix may introduce other problems.  Apparently nobody knows how to
> > fix it right and there is about as much as no documentation at all on
> > this part of the behavior of ttys.
>
> IIRC this code is no longer in Emacs. I'll close this bug.
>
> --
> Alan Third
>

I do know that commands longer than 4096 characters are truncated in emacs
24.3.1

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bug#6800: 23.1; EOT / ^D inserted into comint input string

[Alan Third]

On Fri, Aug 12, 2016 at 11:40:03AM -0700, David Fox wrote:
> On Fri, Aug 12, 2016 at 11:36 AM, Alan Third <alan@idiocy.org> wrote:
> 
> > Stefan Monnier <monnier@iro.umontreal.ca> writes:
> >
> > >> When an input longer than 255 characters is typed into comint (or
> > >> shell) an EOT character (ascii 4, ^D) is inserted into the string.
> > >> This can cause an error depending how the sub process handles these
> > >> extra characters.  For example, GHC doesn't like it when an EOT
> > >> appears inside of a string:
> > >
> > > I believe this bug is fixed on the Emacs trunk (to become Emacs-24), but
> > > the fix may introduce other problems.  Apparently nobody knows how to
> > > fix it right and there is about as much as no documentation at all on
> > > this part of the behavior of ttys.
> >
> > IIRC this code is no longer in Emacs. I'll close this bug.
> >
> >
> 
> I do know that commands longer than 4096 characters are truncated in emacs
> 24.3.1

I just looked at bug#7078 which talks about that. Perhaps these two
should be merged.

-- 
Alan Third