I'm using Windows UIAutomation quite heavily and it works mostly well. But it's throwing some exceptions that I haven't been able to figure out.
The first of these is:
Exception thrown at 0x762D46D2 (KernelBase.dll) in MyApp.exe: 0x80040155: Interface not registered.
The offending section of code is the last line of:
IUIAutomationElementPtr element; //This is a valid element
IUIAutomationCacheRequestPtr cachePtr; //This is a valid cache pointer
IUIAutomationElement **first;
HRESULT hr = myControlWalker->GetFirstChildElementBuildCache(element, cachePtr, firstChild);
The second of these is:
Exception thrown at 0x762D46D2 (KernelBase.dll) in MyApp.exe: 0x40080202: WinRT transform error (parameters: 0x80040155, 0x80004002, 0x0000001D, 0x0565DB4C).
which happens at the same line of code as the previous.
And the last is:
Exception thrown at 0x762D46D2 (KernelBase.dll) in MyApp.exe: 0x8001010D: An outgoing call cannot be made since the application is dispatching an input-synchronous call.
once again, from the same line of code.
The program runs fine and it does what it needs to do, it just bothers me to have zillions of these exceptions being thrown left and right. Any suggestions?
Related
In Lablgtk, whenever there is an exception in a callback, the exception is automatically caught and an error message is printed in the console, such as:
(prog:12345) LablGTK-CRITICAL **: gtk_tree_model_foreach_func:
callback raised an exception
This gives no stack trace and no details about the exception, and because it is caught I cannot retrieve this information myself.
Can I enable more detailed logging information for this case? Or prevent the exception from being caught automatically?
I guess the best way to do so is to catch your exception manually and handle it yourself.
let callback_print_exn f () =
try f () with
e -> my_exn_printer e
Assuming val my_exn_printer : exn -> unit is your custom exception printer, you can simply print your callbacks exceptions by replacing ~callback:f by ~callback:(callback_print_exn f) in your code.
Of course, you can also with that method send that exception to another
thread, register a "callback id" that would be passed along with your exception...
About the stack trace, I'm not sure you can retrieve it easily. As it's launched as a callback, you probably want to know the signal used and that can be stored in your callback handler.
I had another similar issue, but this time it was harder to find where to put the calls to intercept the exception.
Fortunately, this time there was a very specific error message coming from the Glib C code:
GLib-CRITICAL **: Source ID ... was not found when attempting to remove it`
Stack Overflow + grep led me to the actual C function, but I could not find which of the several Lablgtk functions bound to this code was the culprit.
So I downloaded the Glib source, added an explicit segmentation fault to the code, compiled it and used LD_LIBRARY_PATH to force my modified Glib version to be loaded.
Then I ran the OCaml binary with gdb, and I got my stack trace, with the precise line number where the Lablgtk function was being called. And from there it was a quick 3-line patch.
Hacks like this one (which was still faster than trying to find where to intercept the call) could be avoided by having a "strict mode" preventing exceptions from being automatically caught. I still believe such a switch should be available for Lablgtk users, and hope it will eventually be available.
I stumbled upon a very weird issue in ColdFusion which might very well be a bug, but I wanted to post it here in case I was missing something.
It seems that cfindex is throwing an uncatchable exception when trying to index invalid files.
I'm not entirely sure yet what consists of an invalid file, but the issue occurs with a valid PDF file, but that doesn't have a PDF extension. Obviously, the problem can easily be fixed by adding a valid extension, but that's not the scope of the question.
<cftry>
<cfindex
collection="some_collection"
action="update"
key="//someserver/some_file_without_extension">
After index
<cfcatch type="any">
Exception caught
</cfcatch>
<cffinally>
Finally block
</cffinally>
</cftry>
Completed
When running the above code, the only thing that is output is Finally block, therefore it's like if there is an exception thrown, but which cannot be caught.
I even tried with type="java.lang.Exception", type="java.lang.Throwable" and type="searchengine" and nothing works.
The only way I found to detect such exceptions is to check a boolean flag in the finally block, but gracefully recovering form those errors is very cumbersome.
Another very weird thing that occurs is that right after the issue is encountered, if I refresh the page in the browser, I'll get the following error:
HTTP Error 503.0 - Server Error
The service is unavailable.
Module IsapiModule
Notification ExecuteRequestHandler
Handler JWildCardHandler
Error Code 0x00000000
Then after refreshing again, I get Finally block and if I keep refreshing the same behavior occurs over and over (Finally block then 503 error).
In the EFContextProvider (EF6) SaveChangesCore method, the exception handling looks like this:
} catch (Exception e) {
while (e.InnerException != null) {
e = e.InnerException;
}
throw e;
}
This throws only the most internal exception and hides the relevant information revealed by the external exceptions.
When the SaveChanges process goes through multiple layers the next direct layer exception is lost, and only the last exception in the chain is thrown. It doesn't allow to handle well the exceptions for the caller.
Updated Post
As of Breeze 1.4.6, any .NET Exceptions thrown on the server are now available in their original form in the httpResponse.data property of any async breeze result. Breeze will still drill down to extract a "good" error message, but will no longer obscure the initial exception.
Original Post Below -------------------
It's an interesting point. The reason we did this was because most client side apps aren't written to navigate thru the exception chain and we wanted to expose the most 'relevant' error to the client. Most of the apps we looked at just exposed the client "error.message" property directly and with EF errors this was almost always useless.
However, your point is well taken. I think what we need to do is create a new Exception that has a top level message that is the innermost exception message but still expose the entire exception chain for those that want to drill. I've added an internal feature request for this and will try to get it into a near term release ( probably not the next one because we are already in testing for that one).
And thanks for the input.
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.
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.