From: Gin Mendi <gin18em@...>
Date: 2009-09-09T12:04:02+09:00
Subject: Re: Problems with cross-thread violation

Eleanor McHugh wrote:
> Are you certain that in the case of no feed being available, you're
> receiving a nil rather than a zero? Because if not then the following
> condition will always be true and then there'll be times when you try
> and access a non-existent feed.

Yep handle will be nil if log_on fails or encounters an error.

> 
> You could try installing Tenderlove's Never Say Die library from
> github, it allows you to rescue segfaults which might allow you to
> extract some useful program state or else continue as if nothing had
> gone wrong (but that's a really bad idea in the majority of cases).
> 
> You might also try coding your wrapper with ruby-ffi rather than ruby/
> dl.
> 

Ok I'll try looking and studying both of those suggestions. Might take a 
while for me to redo with ffi but I'll post back here what the results 
were.

You mentioned earlier that I may need a separate callback instance for 
each feed handle:

> Does get_live_feed use a separate thread internally? If so the cross-
> thread violation could well be related to garbage collection of the
> callback in which case you may need a separate callback instance for
> each feed handle.

Sorry but I don't fully understand how I could go about doing this? How 
would this work?

Also a little side problem I still haven't solved regarding my callback:

  fc = DL.callback('0PL') { |result_list, count| }
    if result_list
      result_list.struct('C16FF', :code, :value, :stat)
      puts result_list[:code].pack('C16')
      puts result_list[:value]
    end
  }

you'll notice I have a count parameter which is the number of records in 
result_list. I assume result list is an array if count > 1. Been trying 
to figure out how to extract each record if count > 1. Right now only 
managed to do this with just one record as you can see. How could I 
convert my pointer to an array then get each element/record? I'm 
assuming result_list is an array. I tried result_list.ptr.to_a but that 
just made the program crash back to the command prompt with no error.

Anyway thanks again for all the help!
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