Re: [PATCH 00/17] Interrupting programs that block/ignore SIGINT

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

> From: Pedro Alves <pedro@palves.net>
> Cc: gdb-patches@sourceware.org
> Date: Mon, 14 Jun 2021 18:55:17 +0100
> 
> On 2021-06-03 8:51 p.m., Eli Zaretskii wrote:
> >> From: Pedro Alves <pedro@palves.net>
> >> Date: Thu,  3 Jun 2021 20:02:26 +0100
> >>
> >> Currently, on GNU/Linux, it is not possible to interrupt with Ctrl-C
> >> programs that block or ignore SIGINT, with e.g., sigprocmask or
> >> signal(SIGINT, SIG_IGN).  You type Ctrl-C, but nothing happens.
> > 
> > I'm not sure I understand why this is a problem.  If a debuggee blocks
> > or ignores SIGINT, then SIGINT cannot be used to stop it, neither when
> > it runs outside the debugger nor when it runs under a debugger.  There
> > are enough other methods to stop such a debuggee (e.g., send it a
> > different signal), but basically such a program clearly tells that it
> > doesn't want to be interrupted by SIGINT, period.
> 
> It sounds like you're taking the view that Ctrl-C should be seen by the
> inferior first, and behave exactly as if you were not debugging
> the program?
> 
> My view is that, as a user, I see Ctrl-C as the standard way across configurations
> to interrupt programs so I can inspect them.  When I type Ctrl-C, I'm telling
> GDB that I want to stop the program.

Actually, my original problem was caused by your use of "interrupt a
program", when what you actually meant (AFAIU now) was "stop the
program".  This was what originally set me off: the above text you
posted as the preamble for your patch reads like it's saying that
something is wrong with the situation where programs that don't want
to be interrupted by Ctrl-C can't be interrupted by SIGINT under GDB.
Thus my reaction.

However, thinking about the issue some more, now that I understand
what you meant, I do indeed think that programs which block or ignore
SIGINT should not be stopped by Ctrl-C under GDB.  The reason is
simple: SIGINT is just another fatal signal.  Any fatal signal
delivered to a program being debugged will not stop the program if the
program blocks or ignores that signal, right?  So why should SIGINT be
special?

IOW, Are you sure your expectations are not based on old habits, where
"normally" Ctrl-C can be used to stop a debuggee, and thus it is a
convenient means of doing so?

I wonder how many others here think like you and how many think like
me.  If I'm the odd one out, then I won't continue talking about this
aspect of your patches.

I'm glad you found a way of making the effects of these changes less
surprising, but I still have a couple of issues with the changes,
which I will raise in response to your v2.