Re: [commit] Follow forks on HP-UX 11.xx

[Daniel Jacobowitz <drow at false dot org>]

On Wed, Jul 20, 2005 at 06:29:18PM +0200, Mark Kettenis wrote:
> Hmm yes, spamming the output while following the output doesn't really
> make sense.  On the other hand, I think I'd like to see some
> indication that GDB switched to following the child.  But we should
> make sure that all platforms that support this print the same message.
> We should really move the printing of those messages into platform
> independent code.

Yes, we should, and the logic to control them.

>    And, the testcases for following vfork all rely on following exec.  I
>    haven't enabled them, or that feature, because the current user
>    interface for following exec is so awful - it silently changes which
>    binary you're debugging, messes up configured breakpoints, etc etc.
> 
> Hmm yes, I noticed that following execs is still disabled.  And yes
> the code is a mess.  Any objection against removing it completely and
> start afresh.

I'd rather not touch it until we figure out a better interface; it's
mildly useful as an example of where all the hooks would need to go. 
Unless it gets in the way, of course.

>    I don't recall if you have GNU/Linux systems to test on.  If not, let
>    me know if you have testsuite changes you want to check with the
>    GNU/Linux implementation of fork following.
> 
> Trashed the old SuSE on my amd64 box recently, so I'm going to attempt
> installing Fedora Core 4 on it.  You know whether that has a recent
> enough kernel that has the fork/vfork following support in it?

It should, unless RH's patches managed to break it; that's happened in
the past, but I think it won't happen again in 2.6.x.  Should be fine.

> Anyway, to what extent does following vfork work on Linux?  Does it
> work flawlessly, or are there still some issues?

I believe there's a nasty bit if you try to kill both processes while
stopped at a vfork catchpoint, where you'll end up with a zombie.  I
haven't tried to reproduce that in at least a year, though, so it may
be gone now.  Otherwise it works quite just fine.

-- 
Daniel Jacobowitz
CodeSourcery, LLC