[flex] IU-95.260 debugger 'Cannot evaluate expression'

While debugging a flex app, I am seeing a number of variables where IDEA says "Cannot evaluate expression".
One case was an Error local variable in catch clause.
Another was a static String.

Not sure what the problem is. I couldn't find any open youtrack issues.
This is Flex SDK 3.4.0



Catched error evaluation seems to work only with Flex SDK 4 currently. I'll see if it can be improved.
Couldn't reproduce problem with static String. I need some example.


I didn't mention this is with Flashplayer version  When debuggering, there are quite a few variables where I get 'Cannot evaluate expression', and it's not an expression just a simple variable.  If I find some time I can try creating self-contained examples and file a youtrack ticket, as I didn't see open issues on this.

I noticed there is a newer version of Flashplayer available  I will try that to see if it makes any difference.



I tried the new Flashplayer debug version and now flashplayer is crashing regulary after I connect a debugger to it.  Once the debugger stops at a breakpoint, if I just step through a few lines, it usually crashes.  The only thing changed was Adobe flashplayer, so I blame them :)  I will have to try in FlexBuilder and see if it crashes there too.

I got this IDE Error.

For input string: "199
[UnloadSWF] /jsp/swf/ngp.swf/[[DYNAMIC]]/7": For input string: "199
[UnloadSWF] /jsp/swf/ngp.swf/[[DYNAMIC]]/7"
java.lang.NumberFormatException: For input string: "199
[UnloadSWF] /jsp/swf/ngp.swf/[[DYNAMIC]]/7"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
    at java.lang.Integer.parseInt(Integer.java:458)
    at java.lang.Integer.parseInt(Integer.java:499)
    at com.intellij.lang.javascript.flex.debug.FlexSuspendContext$FlexExecutionStack.processFrames(FlexSuspendContext.java:94)
    at com.intellij.lang.javascript.flex.debug.FlexSuspendContext$FlexExecutionStack.access$100(FlexSuspendContext.java:32)
    at com.intellij.lang.javascript.flex.debug.FlexSuspendContext$FlexExecutionStack$1.onTextAvailable(FlexSuspendContext.java:56)
    at com.intellij.lang.javascript.flex.debug.FlexDebugProcess.processOneCommandLoop(FlexDebugProcess.java:385)
    at com.intellij.lang.javascript.flex.debug.FlexDebugProcess.access$200(FlexDebugProcess.java:66)
    at com.intellij.lang.javascript.flex.debug.FlexDebugProcess$3.run(FlexDebugProcess.java:250)
    at com.intellij.openapi.application.impl.ApplicationImpl$5.run(ApplicationImpl.java:331)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
    at java.util.concurrent.FutureTask.run(FutureTask.java:138)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:619)
    at com.intellij.openapi.application.impl.ApplicationImpl$1$1.run(ApplicationImpl.java:125)


Exceptions is already fixed.
Please describe the environment where Flash Player crashes: OS, browser version (if any), Flex SDK version. We know about Flash Player 10.1 crashes on Linux: http://youtrack.jetbrains.net/issue/IDEA-55328 , may be this is the same thing.


FlexSDK 3.4.0
FlashPlayer: (cannot evaluate some vars), (crashes frequently)
OS: Windows 2008 R2 x64
Browser: Firefox 3.6.6

The crash in flashplayer 10.1 that I am seeing frequently could be one and the same problem you mentioned. I've never looked at flashplayer crash files before, so I don't know how to tell if it is the same problem.

I wonder if it is also related to  firefox 3.6.4 update which added plugin crash protection ( http://blog.mozilla.com/blog/2010/06/22/firefox-3-6-4-with-crash-protection-now-available/).

Although, I tried on IE and was also able to get it to crash.



Expression evaluation works better with debugger from Flex SDK 4. As a hacky trick you may substitute /libs/fdb.jar in your Flex SDK 3.4.0 installation to the one from Flex SDK 4.0.0. (Also you'll need to substitute its dependency: swfutils.jar, but at the same time you shouldn't overwrite original file because it is also used by compiler, but you can give it a different name and fix MANIFEST.MF in fdb.jar accordingly :)).

The more interesting thing is Flash Player 10.1 crashes. I don't have Windows 2008 R2 near me, and didn't observe crashes on Vista/Mac, but observed regular crashes on Suse Linux. The problem occured to be in the Flash Player. Here are details: https://bugs.adobe.com/jira/browse/FP-1421?focusedCommentId=370454&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_370454

Can you please check my sample from Adobe's jira on Windows 2008 and add a comment (or better new issue) to Adobe's jira if the issue is not Linux-only?

Permanently deleted user

The hacky trick you mentioned does not really work. I tried it in many different ways including that of you proposed with substituting its dependency and so on. We (and I believe others) do need to use debugger out of Flex 4 for projects built with Flex 3. For team I'm a member its a main drawback to prefer IDEA to your rivals. Do not ask me why we don't move to Flex 4 instead :-).


Please be more specific on what expression can not be evaluated and
where the debugger is stopped (preferably with code example).

On 29.07.2010 23:30, Boris Byk wrote:

The hacky trick you mentioned does not really work. I tried it in many different ways including that of you proposed with substituting its dependency and so on. We (and I believe others) do need to use debugger out of Flex 4 for projects built with Flex 3. For team I'm a member its a main drawback to prefer IDEA to your rivals. Do not ask me why we don't move to Flex 4 instead :).


Original message URL: http://devnet.jetbrains.net/message/5268934#5268934

Best regards,
   Maxim Mossienko
IntelliJ Labs / JetBrains Inc.
"Develop with pleasure!"

Permanently deleted user

Here the example:

HelloWorld.as Game.as
package {

import flash.display.Sprite;

public class HelloWorld extends Sprite {
      public function HelloWorld() {
            var s:String = Game.str;

package {
public class Game {
      public static var str:String = "Hello world";

      public function Game() {

I put breakpoint in HelloWorld.as line 'var s:String = Game.str;'. Breakpoint is hit:

  1. when it's built on top of Flex4 SDK, the expression Game.str is evaluated successfully.
  2. when it's built on top of Flex 3 SDK (3.4.1/3.5.0), it results into 'Cannot evaluate expression'
  3. when it's built on top of Flex 3 SDK with the hacky trick I get

Exception in thread "main" java.lang.NoSuchMethodError: flex.tools.debugger.cli.ExpressionCache.appendVariable(Ljava/lang/StringBuilder;Lflash/tools/debugger/Variable;)V
at flex.tools.debugger.cli.DebugCLI.appendFrameInfo(DebugCLI.java:1210)
at flex.tools.debugger.cli.DebugCLI.doInfoStack(DebugCLI.java:1165)
at flex.tools.debugger.cli.DebugCLI.processLine(DebugCLI.java:6623)
at flex.tools.debugger.cli.DebugCLI.process(DebugCLI.java:725)
at flex.tools.debugger.cli.DebugCLI.execute(DebugCLI.java:567)
at flex.tools.debugger.cli.DebugCLI.main(DebugCLI.java:370)

when  the breakpoint is hit.

What I did for point 3:

  1. Coped fbd.jar from Flex SDK 4 over the one in Flex SDK3.
  2. Edited its fdb.jar/META-INF/MANIFEST.MF changing swfutils.jar->swfutils4.jar
  3. Copied swfutils.jar from Flex SDK 4 to Flex SDK 3 having renamed it to swfutils4.jar

What was wrong?

UPDATED: forgot to say, I use IDEA 9.0.3

Permanently deleted user

Thanks. But forgot to say that if I run fdb.exe from Flex SDK 4 everything works fine even on the code built on top of Flex Sdk 3.

  • run <flex-4-sdk-path>\bin\fdb.exe
  • issue 'run' command
  • break HelloWorld
  • continue
  • print Game.str

It seems like it is an issue with your  bindings for the debugger when/if using the hacky trick.


As described in the beginning of the thread:
FDB from Flex SDK 3 can not evaluate static members.
FDB from Flex SDK 4 can (as you also confirmed).
Mentioned hacky way describes how to get Flex SDK 3 + fdb from Flex SDK 4, you seems not copied enough files.
As workaround, I believe, you can launch FDB 4 if specify Flex SDK 4 as SDK, switch off automatic compile and compile via ANT.
Let's continue discussion on relevant stuff in the YouTrack ticket.


For complete hacky trick you need to copy (with giving different name and fixing MANIFEST.MF) not only swfutils.jar, but also mxmlc.jar, asc.jar, and all other dependencies mentioned in these jars.

Permanently deleted user

I think I was able to fix it. I did exactly what you suggested including ALL dependencies. But important thing to do is to rename {IDEA Intallation}\plugins\flex\lib\idea-fdb-3-fix.jar -> {IDEA Intallation}\plugins\flex\lib\idea-fdb-3-fix.jar.bak. Otherwise you will still be getting exceptions due to the explicit bindings.

For those lazy you can download the renamed patched files from http://www.borisbyk.com/idea-flex3sdk-patch.zip. Check out the readme.txt file for further instructions.

Now it works for me on my simple examples. I'm going to give it a whirl in a more complicated project.