I'm having trouble with my Deno program. I'm getting messages like this:
error: Uncaught (in promise) Error: No such host is known. (os error 11001)
at deno:core/01_core.js:106:46
at unwrapOpResult (deno:core/01_core.js:126:13)
at async Object.connect (deno:extensions/net/01_net.js:219:13)
Then deno exits.
I don't know how to debug this. This stack trace only points to code that comes with Deno, not to my code.
I've searched my code and I've put a .catch() or a try/catch everywhere I can think of, but that did not help.
Is there anything I can do to help me find the problem? I'd love it if I could get a complete stack dump. Or if I could have the debugger pause at the problem. Or if you have any other suggestions.
Thanks!
Edit 8/29/2021
I found two bugs in my code. Here are the actual bugs. It was a serious pain to track these down. I'm still looking for a tool or process to help the next time I make a silly mistake like this.
Bug #1:
I was using try/catch (shown in red) when I should have been using .catch() (shown in green). My try/catch did nothing. If there was an error sending the data, that would cause my program to crash.
Bug #2:
const promise = Deno.connect(options);
promise.catch(reportError);
promise.then(longRunningTask);
await someOtherPromise;
promise.then(connection => {
// We never get to here.
try {
connection.close();
} catch {
console.log("🙁");
}
});
// And we never get to here.
The code I've shown here was spread throughout a much longer program. I did not understand the rules regarding promises. The second .then() requires a second .catch().
Here was one of my attempts to solve this problem. I told VS code to break on all exceptions. It seems to ignore my request. I never got to a breakpoint, but the debug console shows that the program crashed because of an exception.
Here is the problem that I want to implement a solution, I have some data that needs to be writen in a database,data comes from network and it could arrive in "parallel", also for performance reasons the code is using async connection. The problem is that I have some bugs in my implementation ,I want to rewrite this code so it also uses transactions and rolloback,handle all possible errors and the code should be clean and easy to understand.
I am unable to find example code to read to get inspired or something to use directly, looking on what others done would help a lot.
So anyone know or has such example code?
I think I need to write some code that will allow me to chain this methods :begin->execute->commit->end transaction and in case of errors rollback
Update
what I want to find or implement is something like
Update2 so where things get confusing is when you want to insert an array of stuff, you will need to use a loop and then use the execute method async, and then when it succeds insert the next element and so on, this makes it a little more complicated especialy if I want to abstract this ito have all this section of code in a single place and not all over my code.
function executeAssyncAsTransaction(statement:SqlStatement,responder:Responder):void{
//step 1 begin transaction
//step 2 execute
//step 3 commit
//step 4 end transaction
//step 5 handle errors and rollback
//use responders above no event listeners
}
I think I know how to implement this but I know that there is a chance I do it wrong (my current implementation that is in production crashes sometimes on some machines so I I know is hard to write 100% error free code)
I am, also thinking to implement a queue that will store my statements if needed(if database is busy) so I don't get an error and have to try again later
Use event listeners, error and callback functions in Adobe Air for JavaScript like this:
var conn = new air.SQLConnection();
conn.addEventListener(air.SQLEvent.OPEN, openHandler);
conn.addEventListener(air.SQLErrorEvent.ERROR, errorHandler);
// The database file is in the application storage directory
var folder = air.File.applicationStorageDirectory;
var dbFile = folder.resolvePath("DBSample.db");
conn.openAsync(dbFile);
function openHandler(event)
{
air.trace("the database was created successfully");
}
function errorHandler(event)
{
air.trace("Error message:", event.error.message);
air.trace("Details:", event.error.details);
}
For ActionScript read these ressources:
http://de.slideshare.net/peterelst/introduction-to-sqlite-in-adobe-air-1627545
I was working on my flash project, which compiled the whole time just fine.
Then I did some changes, then, when testing the project, the project compiles,
the flash player comes up, showing the first frame, but no code executes.
No single trace output. Nothing. No Errors, No Warnings, very strange!!!
Can anybody help me???
You might have stumbled over a BUG in the FlashIDE/Flex Compiler.
Try this snippet and wonder:
// ------ Put in first frame of a fresh flash file
trace ("why won't i execute");
var dummy=function(a:int){
a:int = 0;
}
Instead of catching your coding mistake:
a:int = 0; should eihter be var a:int = 0; or a=0;
the compiler chokes, and dies, without even having the time to let you know.
Beware!
This mistake can be deeply hidden in some, over many intermediate classes imported, class.
So, to answer your question, look at the things you have changed, you might have changed a local var to be given as a function argument, took away the local var but forgot to remove the :type part as well.
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.
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.