I'm really struggling to resolve a stack underflow that I'm getting. The traceback I get at runtime is:
VerifyError: Error #1024: Stack underflow occurred.
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at flash.net::URLLoader/onComplete()
This is particularly difficult to debug because when I run in debug mode it does not happen at all. It only happens when compiled as a release.
Does anyone have any tips on how to debug a Stack Underflow? Are have a clean explanation of what that means for Flash?
In case it helps, this error is occurring when I click a button whose handler makes an RPC call, which uses a URLLoader, an AsyncToken, and then invokes the set of AsyncResponder instances associated with the AsyncToken. With some server-side logging as well as some logging hacked into the swf, I know that the UrlLoader is successfully doing and GET'ing a crossdomain.xml file, is correctly processing it (ie: if I wreck it, I get a security error), and is also successfully completing the "load" request (the server sends the data). The underflow seems to be happening in the Event.COMPLETE listening/handling process (as is, of course, implied by the traceback as well).
mxmlc used = from flex_sdk_4.5.0.20967
Example player (I've tried a few) = 10.2.153.1
UPDATE: My specific problem is solved... but I'm leaving the question as-is since I would like to know how to generally debug such a problem, rather than just getting my specific solution.
In my code I had the following Application definition:
<s:Application height="100%" width="100%"
xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx"
initialize="InitData();">
Note that the code is/was attached to the initialize event.
InitData() and relevant defintions are/were:
import classes.RpcServerProxy;
public var SP:RpcServerProxy;
public function InitData():void {
SP = new RpcServerProxy("http://192.168.1.102:1234");
}
When I switched the InitData() call to be on the onCompletion event instead of initialize (thanks J_A_X!), the problem goes away entirely. What seems to have been happening was that the Event.COMPLETE event handler (onComplete in the stack trace) was using the global SP object. Something about the release (vs debug) compilation must have been affecting the startup timing of the SP variable initialization. Moving the handler later to the onCompletion event resolved all issues.
As said above, I would still like to know what tricks/tools are available for debugging initialization issues like this.
UPDATE 2:
applicationComplete seems to be an even better event than creationComplete to put application initialization code. See this blog entry for some explanation, and and this video (around 4:25) by an Adobe Tech Evangelist for an example of simple "start of application" data initialization.
I got rid of this error by adding compiler argument:
-omit-trace-statements=false
Stack underflow basically means the compiler messed up.
You can use SWFWire Inspector to look at the bytecode of the event handler, if you want to know exactly how it messed up. You can also use SWFWire Debugger to see which methods were called, but in this case, you already knew where it was happening.
If you post the broken swf, I can give you more info.
Sean is right that to debug it you can look at the byte code, but that didn't sound appealing to me.
Based on my experience and research, it is often due to the presence of a trace statement that incorrectly gets compiled out in release mode, and generates invalid byte code. So, I would say to "debug" it, "Look for places where you are using trace. Try commenting them all out in the offending function and see if the issue goes away."
In my case, it was a trace statement as the first line of a catch block:
catch (e:TypeError) {
trace(e.getStackTrace()); //This line is the problem
throw new Error("Unexpected type encountered");
}
I found someone else with this exact issue here.
This code also leads to stack underflow only in release mode (flag -debug=false):
true && trace('123');
mxlmc flex sdk version 4.5.0.20967, flashplayer version 10.3.181.14 (linux).
Check your code for similar expressions.
This code caused me issues when I compiled a release candidate from flash builder 4.5
public function set configVO( value:PopupConfigVO ):void
{trace("CHANGING")
Resolved by inserting a space between the the trace and curly brace
public function set configVO( value:PopupConfigVO ):void
{ trace("CHANGING")
Hope this helps.
For people looking for the same problem, I just got this caused by a trace statement in the 'default' case of a switch statement. Commented out the trace, stack underflow resolved.
Interesting... I was getting this error with a SWF that I'd pulled off the web, an Away3D based graphics demo. At the time I was running this on the Tamarin VM rather than the actual Flash/AIR runtimes, so could stick a breakpoint on the "verifyFailed(kStackUnderflowError)" line and see what was happening.
The -Dverbose flag also helped find the culprit:
typecheck MethodInfo-1480()
outer-scope = [global]
[Object~ Object] {} ()
0:pop
VERIFY FAILED: Error #1024: Stack underflow occurred.
And looking at the ABC using SWFInvestigator, I found this:
var function(Object):void /* disp_id=0 method_id=1480 nameIndex = 0 */
{
// local_count=2 max_scope=0 max_stack=0 code_len=2
// method position=52968 code position=155063
0 pop
1 returnvoid
}
So there is an obvious issue where the 'trace' has been removed but the compiler has put a 'pop' in there: I wouldn't have thought this was needed as a trace call should presumably have been made via 'callpropvoid'?
Quite why this doesn't fail on AIR/Flash I don't know..
Anyway: looks to me like an ASC compiler problem i.e perhaps one of the ActionScript3 compilers had a fault with this - hence the workarounds that have been mentioned so far.
It's quite simple, and it doesn't have anything to do with spaces before or after brackets, trace commands or whatever else: it's just 1 really simple thingy:
DO NOT LOOP EMPTY!
Meaning, while developing, we all //comment some lines sometimes, and when that results in
for (...) {
// skip for now
}
the compiler gets :
for(...){}
and that my good friends, is something the compiler doesn't like!
so, NO empty loops, and you're on your way again...
Happy hunting,
P.
I had the exact same problem, but in my case the cause of the problem was a trace statement in a place where the compiler didn't expect it to find it, right after a package declaration at the beginning of the class:
package utils
{
trace ("trace something here");
And that's why compiling in debug mode removed the problem.
Related
I would like to have many devices testing a game, and I find the best way to debug a game and solve specific code problems is to have the device connected and in debug mode in Adobe ANIMATE, that way I can catch any Errors in the Output window.
For Example, if I am debugging and connected to Animate, the output window will throw errors like :
ReferenceError: Error #1065: Variable bg_storage is not defined.
at global/flash.utils::getDefinitionByName()
at Game/stageAdd()[/Users/**/Game.as:360]
Now I know exactly what the problem is and where to find it. I love errors like this.
My question :
If I didn't have a device connected to Animate in Debugging mode, is there a way to make the game detect any errors thrown and store them as a String, that way I can put up a big text block on the game of the error string and keep track.
or at least a way to log them some how?
Ex :
If an error is thrown, have that error text set as a String variable, then have a text box write out that String variable.
I hope that isn't too confusing. If I am going about debugging in a poor way, I would love to know what you guys do to keep track of errors without being connected to debug mode.
EDIT
I can see an approach is you to add an uncaughtErrorEvent event to each function to be able to catch these errors...
loadbar.uncaughtErrorEvents.addEventListener(UncaughtErrorEvent.UNCAUGHT_ERROR ... )
I am trying to make it so any error thrown in any part of the game will trace that error somewhere to a String value that I can call, so that I can see any error thrown during a play test session without being connected to debug mode.
Thanks!
Sure. There's a class intended exactly for that: https://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/events/UncaughtErrorEvent.html See examples at the bottom of the page to listen to the right instances for that event.
You are also free go grab my own class that does the thing you want: https://bitbucket.org/thydmitry/ru.delimiter/src/2756fadd741a6d44276fde1701470daf24cebfa8/classes/ru/delimiter/utils/Log.as?at=default&fileviewer=file-view-default
You will need to add it to your project and then call in the main document class (in constructor, preferably):
Log.create(this);
Log.handleExceptions(this, true);
I am getting, just for once every app runtime, an exception in the method saveContextToPersistentStore in RKManagedObjectRequestOperation.m: on line
success = [contextToSave save:&localError];
success is YES, localError is nil. I can continue the program execution in debugger.
I tried to wrap it with #try block but with no success (as something else took care of this) to get more information why it happens.
Can you help me to investigate the cause of this? Is this something I should pay attention to? This answer may targets this issues. But I am not sure, if the problem is local or caused in higher layers (Restkit mapping).
Stack:
I'm working on some flash app. Now, to test customer side of it I can use Flash Player debugger version that will save logs and show error messages. When it's deployed on the customer side - they will have a regular Flash Player version which means I will have no access to error messages if errors will happen. So I would like to equip it with some tool that would capture all of my trace messages in code and errors text. As for trace messages that's fairly simple, I just override the function in my code so it sends a POST request with trace message to a logger server, but how can I get a hold of the error message? Is there a known approach to this or some trick that somebody can suggest?
You can install the debug version of flash as your browser's default (in Chrome, you must disable the built-in player), so if you wanted to test user experience and debug, this would be the ideal solution.
However, to answer your question: there's no method for universally catching all errors, and redirecting them (that I know of). You'd have to encapsulate problem code ahead of time with try...catch statements, and send the property back on catch. For example:
try {
this["foo"]();
} catch (e:Error) {
trace(e);
}
In the debug version, the traced value would be TypeError: Error #1006: value is not a function. And while the standard version will only output TypeError: Error #1006, (a notably less descriptive error), what we're missing is any reference to where the error occured. To get this, we need to use Error.getStackTrace() to see the call stack and the line where the error occurred. In debug, this outputs the following:
TypeError: Error #1006: value is not a function.
at Shell_fla::MainTimeline/init()[C:\Projects\shell.as:91
In the standard client, we get a dissapointing null. In short, you cannot get any valuable info from the client versions.
The best advice I can give is to write around your problem code with your own custom error reports. For example, catch IO errors and trace the file it failed to load, or if you're expecting an object.foo, first try if (object.hasOwnProperty("foo")) { // do something } else { trace("foo not found in " + object.name) }. Code defensively.
Cheers,
I've discovered this post on StackOverflow:
How to catch all exceptions in Flex?
It answers my question, strange that I haven't ran into it while I was googling prior to asking.
Say I have below lines any in a Java class,
System.out.println("start");
if(true)//The compiler will give compile time error if I uncomment this.
throw new RuntimeException();
System.out.println("end");
The unreachable code error message will appear if the if(true) is commented. Why Don't the compiler know that the line under if(true) will always be executed?
Is the Java compiler is designed to work like this or is it a limitation?
It's deliberate part of the design around code reachability. See section 14.21 of the JLS which has a section at the bottom about this.
The rationale for this differing treatment is to allow programmers to define "flag variables" such as:
static final boolean DEBUG = false;
and then write code such as:
if (DEBUG) { x=3; }
The idea is that it should be possible to change the value of DEBUG from false to true or from true to false and then compile the code correctly with no other changes to the program text.
It is a limitation of how far you go to check you have dead code or code which will never run.
The JVM can detect the code is dead and not compile it.
I used a MFC virtual list control to enhance the performance and I handle GetDispInfo(NMHDR* pNMHDR, LRESULT* pResult) to populate the ListCtrl. The relevant code in that method is as follows:
if (pItem->mask && LVIF_TEXT)
{
switch(pItem->iSubItem)
{
case 0:
lstrcpy(pItem->pszText, rLabel.m_strText);
break;
case 1:
sprintf(pItem->pszText, "%d", p.o_Value);
break;
default:
ASSERT(0);
break;
}
}
Here, when I use lstrcpy(),when I'm srolling down/up, I get a whole lot of exceptions saying First-chance exception at 0x7c80c741 in test_list_control.exe: 0xC0000005: Access violation writing location 0xb70bf2ac. These messages appear in the debug output. But the program doesn't crash. Can anyone please explain what the matter here and how should I overcome that??
rLabel is a CLabelItem which I have declared earlier.
Thank you!
If all you see is the first chance exception thing, stop worrying. See for example Link but you can find similar pages all over the place (mostly from 5-10 years ago.) It means some code threw and the exception was caught and dealt with. I see this in MFC apps some times. As the blog entry says
First chance exception messages most
often do not mean there is a problem
in the code.
I would wait until you see actual errors before getting worked up about this one.
I think you should check if buffer that is pointed by pItem->pszText is large enough to hold rLabel.m_strText. Or if rLabel.m_strText is correct null terminated string. For me this looks like writing uninitialized memory. Use the debugger to check this.