I have a few thoughts. For one thing, reading through the thread over on flashdevelop.org, some (and perhaps all) of the problems people encountered were due to a bug in the Flash player, which was fixed this past summer. (The Flash Builder record of the bug is here: http://bugs.adobe.com/jira/browse/FB-16153 -- but the bug was actually in the player.)
So please make sure you have the latest debugger version of the Flash player. You can get the latest version here: http://www.adobe.com/support/flashplayer/downloads.html
That is almost certainly the cause of the "WARNING: The Player that you are using does not support all fdb commands" message that member "elyon" described in his post on June 4, 2009. Hopefully it will help with whatever problems you are running into.
In another post that same day, elyon saw this output from FDB:
Adobe fdb (Flash Player Debugger) [build 4852]
Copyright (c) 2004-2007 Adobe, Inc. All rights reserved.
Waiting for Player to connect
Player connected; session starting.
Unexpected error while processing command.
For diagnostic purposes stack trace follows:
But apparently there was no stack after that message. If you can reproduce that error message, the way to get stack dumps to appear is to pass "-Dtrace.error=true" to Java when it launches FDB. This is a Java property, so it must be passed as an argument to Java, not to FDB. For example, if launching FDB from the command line, you can launch it like this:
java -Dtrace.error=true fdb.jar
> Does Flex Builder use the same apps as the Flex SDK?
Yes, but not in quite the same way FlashDevelop does. FDB has a public Java API that can be called by any Java app to control debugging, and that's what Flex Builder does, unlike FlashDevelop's approach. So, FlashDevelop and Flex Builder are using the exact same underlying debugger code; it's possible that there is some sort of problem with FlashDevelop's communication over the pipe, I just don't know.
You say you haven't seen this issue when "debugging by hand" -- you mean when using FDB directly? If so, then I suppose the Flash player version isn't the problem. I'd be interested to see a repro case that involved just FDB (perhaps reading commands from a file or a pipe if that's the easiest way to reproduce it).
There is nothing unusual about FDB's communication with stdin and stdout, it's pretty standard stuff. Also, it's all open source, http://opensource.adobe.com, so you can debug it if you want.
- Mike Morearty
Flash Builder team
Thank you for your feedback!
Please leave this thread open as I go over the items you mentioned to try and get to the bottom of this. Fixing this will make a lot of developers happy :)