Re: [PATCH 3/3] Fix control-c handling on Windows

[Tom Tromey <tromey@adacore.com>]

>> If that's the issue then I can write a patch to change sigint_ours to be
>> a gdb::optional and check it that way.

Hannes> I should have been more clear about this.
Hannes> I started with 'new-console on', so sharing_input_terminal() returned false,
Hannes> and that's why sigint_ours was not set.

Hannes> So yes, gdb::optional would probably fix this.
Hannes> I just wonder if this is never an issue on Linux, e.g. if you attach,
Hannes> of does signal() maybe ignore NULL-pointer functions?

Normally SIG_DFL is NULL, but also on Linux I couldn't get this to
trigger inappropriately.  Maybe my theory about what's going on here is
incorrect.

Hannes> As far as I could tell, signal() calls SetConsoleCtrlHandler(), probably
Hannes> similar to how you handled this.

Yeah, that was my guess as well, but really we'd want more details.
Like, does calling signal reinstall the SetConsoleCtrlHandler?  If so
then why didn't that work for gdb?  But if not then why did we need to
call SetConsoleCtrlHandler again to tweak the ordering of callbacks?

Maybe I should go back and try to figure out what else is calling signal
and/or SetConsoleCtrlHandler.  I somewhat suspect Python but I don't
really know.

>> I did try 'new-console on' with my (x86-64) build, and that worked fine.
>> I can try an x86 build and see if that works any better.

Hannes> Again, I wasn't clear enough here.
Hannes> The difference is not because of i686 and x86_64, but that the x86_64 build
Hannes> has TUI+python enabled, but my i686 build has not.

Aha, I see, thanks.

Hannes> Some TUI startup code would later call install_sigint_handler() again,
Hannes> overriding the SIGINT handler again, and everything is fine.

Do you know where this happens?

Anyway I am wondering if we can have gdb_rl_deprep_term_function call
rl_clear_signals and then reinstall the gdb signal handlers.  This idea
makes me wonder if we even need SetConsoleCtrlHandler at all -- maybe gdb
could just use signal after all.

Tom