Re: [PATCH v2 16/16] Document pseudo-terminal and interrupting changes

[Eli Zaretskii via Gdb-patches <gdb-patches@sourceware.org>]

> From: Pedro Alves <pedro@palves.net>
> Cc: gdb-patches@sourceware.org
> Date: Wed, 16 Jun 2021 10:31:27 +0100
> 
> >> +On such systems, in some cases, like for example if you need to run
> >> +your program and then detach it, and you want the program to remain
> >> +associated with a terminal, you may prefer that @value{GDBN} starts
> >> +your program using the same device for standard input and output as
> >> +@value{GDBN} is using.
> > IMHO, this is a misfeature.  If the terminal from which GDB was run
> > remains on the system, it would be an unpleasant surprise for the user
> > that the program gets hit by SIGHUP when you detach.  I think we
> > should try to avoid this side effect, if that's feasible.
> > 
> 
> Hmm, I'm not sure I follow what you're saying here, maybe I'm misunderstanding.
> 
> We no longer get a SIGHUP on detach, that was fixed on v2.  What the text is saying now is
> different: because when you start your program with "run", the terminal the inferior is
> associated with was created by GDB, when you "detach", GDB destroys the terminal.  The
> result is that the program you detached from loses its terminal.

I understood that, and this is what I was calling "a misfeature"
above.

> From the detached
> program's perspective, it's the same as with current GDB when you do "run", then "detach",
> and then close the GDB terminal.

_Technically_ it is the same.  But from the user POV, it isn't, not
unless the user closes the terminal from which he/she invoked GDB.  As
long as that terminal stays, the user might be surprised to see the
program behaving as if the terminal was closed.

> If you really need to do "run" and then "detach" for some reason, _and_ you want
> your program to have a terminal, you should start the program with a specified
> terminal, like:
> 
>  - start the program outside gdb, and then use "attach".  Make sure the terminal
>    you started the program at remains alive.
> 
>  - use the "tty" command to tell GDB to start the program on some specified terminal 
>    (which will outlive gdb and gdb's terminal)
> 
> If you're sure gdb's terminal will stay around, and you want to tell GDB to start
> the program on that terminal, you can use the "tty /dev/tty" command before starting
> the program.

I understand.  Your description is clear.  I'm saying that it would be
good to avoid this side effect, if possible.  If not, users will have
to live with it.