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Re: Exception reading pipe from NSTask using debugger
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Re: Exception reading pipe from NSTask using debugger


  • Subject: Re: Exception reading pipe from NSTask using debugger
  • From: James Bucanek <email@hidden>
  • Date: Fri, 11 Mar 2005 08:42:49 -0700

email@hidden wrote on Thursday, March 10, 2005:

>Well, your code runs fine in the scenarios you give on my PB17 1.33GHz,
>10.3.8 (no haxies...) so it might be an issue that only shows up on
>dual CPU machines. If you have the CHUD tools installed you'll have a
>'Hardware' System Preference that can turn off one of your G5's cpus to
>see if that makes a difference. The CHUD tools are not installed by
>default, but they are located on the Xcode developer tools CD.

I had the CHUD tools installed already, so I turned off one CPU.  It didn't make any difference.  Maybe it's a G5 issue?

>If you know you will always have less data than the socket buffers
>(~32K if memory serves) you could try calling -waitUntilExit before
>-readDataToEndOfFile.

I don't like to make those kinds of assumptions.  I'm sure ps is unlikely to return more than 32K of data, but somewhere in the universe someone is going have a system that does; The app will hang, and I'll get blamed for it.  ;)

Regardless, I did try putting the waitUntilExit before the read and it works fine.  I also tried using a loop calling availableData, but that did the same thing.

It appears that almost any significant delay between launch and read prevents this from occurring.  I would guess some race condition introduced by the debugger, but I haven't a clue as to what it might be.

>(Also, in my code I wrap -launch in an exception handler since the
>documentation says it can raise an exception if something prevents the
>process from running...)

This whole block is wrapped in a NS_DURING block, which is how I was catching the exception.  But all that was superfluous to the example, so I left it out.

Thanks for the suggestion.

--
James Bucanek <mailto:email@hidden>
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