Re: [Expectperl-discuss] problem syncing with spawned process under debugger.

[Jim C. <jc...@di...>]

Roland Giersig wrote:

> Sorry for replying so late...


No problem - thanks for responding


In case its not clear (and it appears that it was clear - or at least 
that you understood me - I just want to be sure)
Im explicitly *not* trying to debug Expect or the external program it 
spawns,

I want to avoid the debugger in the middle problem, and was hoping that 
I was insufficiently clever
to have understood the debugger option that would suppress the 
sub-process' debugger.

 From what youve said, it would not be enough for the forked debugger to 
run in non-stop mode.

So, Im thinking about trying to pre-spawn the external program, then 
attaching to it
with my (modified) perl-prog under the debugger.

Do you have any quick tips or advice wrt this approach ?

tia
jimc


>
> >> When trying to debug my cruft (elided),
> >> I had a consistent problem hooking up to spawned process under the
> >> debugger.
>
> Well, debugging programs that fork is not easy, and even binary
> debuggers have their problems with such a case. It gets even worse for
> the perl debugger: when the perl interpreter forks, it also means that
> the debugger forks, in fact you are then dealing with two independent
> debuggers that don't know of each other, but continue to share their
> various filedescriptors, namely STDIN.  So the parent process now sees 
> not the child it expects to, but the child-behind-a-debugger, which 
> may and often does result in confusion.
>
> I don't think there is really a solution for that problem, apart from 
> "if that hurts, don't do that".
>
> Oh, and that's why I'm trying to discourage the use of Expect (well, 
> actually IO::Tty) and point to other solutions, e.g. Net::Telnet 
> instead of spawning a telnet client.  Expect still can be used with 
> Net::Telnet, but without the overhead of spawning another process.  
> There is even a
> pure-perl implementation of ssh, but unfortunately without a 
> filedescriptor-interface that is usable with Expect...
>
> This leaves the good olde, but not very powerful debug-with-print...
>
> Sorry that I cannot be of more help.
>
> Roland
>
>
>
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