Re: Signal/gdb oddity in 2.5.61

[Daniel Jacobowitz <dan@debian.org>]

On Sun, Feb 16, 2003 at 05:00:36PM -0800, Roland McGrath wrote:
> > That said, I've still got two issues with your change.  For one thing,
> > the version of GDB that Russell was running, you'll note, was 5.0.  A
> > lot of people haven't upgraded GDB in years, and have some dispute with
> > the present version that means they don't want to upgrade.  I've only
> > just stopped seeing people using 4.18.  In conversation with Russell
> > I've already encountered another reason he doesn't want to upgrade. 
> 
> Anyone who wants to use an old gdb with a new kernel can use "handle
> SIGSTOP nopass".  Is that a real imposition?  Anyway, aside from the test
> suite, it only affects gdb users in a way that may confuse them for a few
> seconds but doesn't prevent them from debugging normally.
> 
> > And I'm also concerned that other programs may use it.
> 
> Other programs may use PTRACE_CONT with SIGSTOP and expect it to act like
> PTRACE_CONT with 0?  It's certainly possible.  But since the quirk with
> SIGSTOP was so counterintuitive to begin with, it seems unlikely to me that
> someone would have expected that behavior in particular.  Some programs
> like strace are written to treat all signals the same and pass them through
> to PTRACE_CONT (actually PTRACE_SYSCALL); they will now cause an endless
> stream of SIGSTOP stops until someone uses SIGCONT, instead of swallowing
> the SIGSTOP--now they do for SIGSTOP what they've always done for SIGTSTP
> et al.

I think I'm convinced.  Sorry for wasting your time.  If it comes up we
can put it on a GDB FAQ somewhere.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer