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  • Is there a way to catch assignments to or reads from an undefined property in the Spider-Monkey Java

    - by avri
    The Spider-Monkey JavaScript engine implements the noSuchMethod callback function for JavaScript Objects. This function is called whenever JavaScript tries to execute an undefined method of an Object. I would like to set a callback function to an Object that will be called whenever an undefined property in the Object is accessed or assigned to. I haven't found a noSuchProperty function implemented for JavaScript Objects and I am curios if there is any workaround that will achieve the same result.

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  • Is there a way to catch assignments to or reads from an undefined property in JavaScript?

    - by avri
    JavaScript implements the noSuchMethod callback function for JavaScript Objects. This function is called whenever JavaScript tries to execute an undefined method of an Object. I would like to set a callback function to an Object that will be called whenever an undefined property in the Object is accessed or assigned to. I haven't found a noSuchProperty function implemented for JavaScript Objects and I am curios if there is any workaround that will achieve the same result.

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  • Cocoa : How do I catch drag operations initiated from an IKBrowserView?

    - by bucketmouse
    So I've got an IKBrowserView all wired up and happily dragging my custom datatype (provided lazily via PasteboardItem) from one window to another, but now I'm interested in detecting when the user drops some data onto the trashcan. Cocoa's documentation says to check the return type of the drag operation itself, but how exactly do I do this with an IKBrowserView? Once I call imageBrowser:writeItemsAtIndexes:toPasteboard: I don't seem to get any notifications other than the request for the pasteboard contents, which doesn't provide a pointer to the drag operation that invoked it.

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  • How can I catch a change event from an HTML text field when a user clicks on a link after editing?

    - by Eric the Red
    Our webapp has a form with fields and values that change depending on values entered. Each time there is a change event on one of the form elements, we use an expensive AJAX call to update other elements on the page. This works great for selects, radio buttons and checkboxes. The issue comes in when a user adds content to a text field, and then clicks a link without taking the focus from the text field. The browser moves to a new page, and the contents of the text field are never saved. Is there an easy way to code around this? The AJAX call is too expensive to call with each key press. Here's an example of my Prototype code at the moment: $$('.productOption input.text').invoke('observe', 'change', saveChangeEvent);

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  • Is the scope of what Xcode's "Build and Analyze" will catch as a leak supposed to be this limited?

    - by Ranking Stackingblocks
    It doesn't care about this: NSString* leaker() { return [[NSString alloc] init]; } I thought it would have been smart enough to check if any code paths could call that function without releasing its return value (I wouldn't normally code this way, I'm just testing the analyzer). It reports this as a leak: NSString* leaker() { NSString* s = [[NSString alloc] init]; [s retain]; return s; } but NOT this: NSString* leaker() { NSString* s = [[NSString alloc] init]; // [s retain]; return s; } which seems particularly weak to me. Does it only analyze within the local scope? If the tool can't pick up on things like this, how can I expect it to pick up on actual mistakes that I might make?

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  • XMLReader : how to catch syntax errors in the xml file ?

    - by mishal153
    Hi, I have an XML file with syntax errors. eg. <Viewport thisisbad Left="0" Top="0" Width="1280" Height="720" > When i create an XML reader it does not throw any errors. I there a way to do syntax checking automatically, like XMLDocument does ? I have tried setting various XmlReaderSettings flags but found nothing useful.

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  • Tool To Catch All The Inputs That Cause Crash?

    - by Barakat
    Hi all, I need a Windows tool records inputs and debugging informations that cause program's crashing. I don't mean a fuzzing tool ! Ammmmm ... let me show you a scenario may explain what I'm talking about. Sometimes during using a program, It's crashed without known reason ! and when I want to debug it, I will not find helpful informations to know how the crash happened. Because that the data that cause the crash no longer exist. So I need a tool records all the inputs and debugging informations to find helpful informations to reuse the inputs data to make the program crashes under a debaucher in order to understand how the crash happen.

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  • How do I best catch up with the latest developments in java?

    - by Fredriku73
    I am applying for a job as java developer. I programmed some hobby apps in java until 2001, after that I have mostly worked in c++ and other languages. Meanwhile, it feels like java has grown a lot, and there are all kinds of acronyms (EJB, spring, etc) unknown to me. Where can I find a concise, clear explanation of the recent (5 years) development of java? What are key elements to understand?

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  • how to catch the event when the particular application process is being suspended using task manager?

    - by Mohan
    I am developing a simple application where in we have predefined quotas on usage for each user on the system.. and if the quota is up..the system should logoff of the user account.. this will happen if the application is allowed to run.. but if the user is closing the application on his own ..the app should automaticaly logoff the account.. i did exactly that in writing forced logoff code in form-closing event.. but if we are closing the app/process using the taskmanager.. the form closing event is not being called. and so the user is able to continue even if his quota of time is up.. can anybody helpme out with this..

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  • Is there a way to catch an attempt to access a non existant property or method?

    - by Tor Valamo
    For instance this code: function stuff() { this.onlyMethod = function () { return something; } } // some error is thrown stuff().nonExistant(); Is there a way to do something like PHP's __call as a fallback from inside the object? function stuff() { this.onlyMethod = function () { return something; } this.__call__ = function (name, params) { alert(name + " can't be called."); } } // would then raise the alert "nonExistant can't be called". stuff().nonExistant();

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  • Examples of bad variable names and reasons [on hold]

    - by user470184
    I'll start with a class in the jdk package : public final class Sdp { should be : public final class SocketsDirectProtocol { Sdp is class name, this is ambigious, should be : Class<?> cl = Class.forName("java.net.SdpSocketImpl", true, null); should be : Class<?> clazz = Class.forName("java.net.SdpSocketImpl", true, null); cl is ambiguous private static void setAccessible(final AccessibleObject o) { should be : private static void setAccessible(final AccessibleObject accessibleObject) { There are various other examples in this class, do you have similar and/or differing examples of variables that were named badly ? package com.oracle.net; public final class Sdp { private Sdp() { } /** * The package-privage ServerSocket(SocketImpl) constructor */ private static final Constructor<ServerSocket> serverSocketCtor; static { try { serverSocketCtor = (Constructor<ServerSocket>) ServerSocket.class.getDeclaredConstructor(SocketImpl.class); setAccessible(serverSocketCtor); } catch (NoSuchMethodException e) { throw new AssertionError(e); } } /** * The package-private SdpSocketImpl() constructor */ private static final Constructor<SocketImpl> socketImplCtor; static { try { Class<?> cl = Class.forName("java.net.SdpSocketImpl", true, null); socketImplCtor = (Constructor<SocketImpl>)cl.getDeclaredConstructor(); setAccessible(socketImplCtor); } catch (ClassNotFoundException e) { throw new AssertionError(e); } catch (NoSuchMethodException e) { throw new AssertionError(e); } } private static void setAccessible(final AccessibleObject o) { AccessController.doPrivileged(new PrivilegedAction<Void>() { public Void run() { o.setAccessible(true); return null; } }); } /** * SDP enabled Socket. */ private static class SdpSocket extends Socket { SdpSocket(SocketImpl impl) throws SocketException { super(impl); } } /** * Creates a SDP enabled SocketImpl */ private static SocketImpl createSocketImpl() { try { return socketImplCtor.newInstance(); } catch (InstantiationException x) { throw new AssertionError(x); } catch (IllegalAccessException x) { throw new AssertionError(x); } catch (InvocationTargetException x) { throw new AssertionError(x); } } /** * Creates an unconnected and unbound SDP socket. The {@code Socket} is * associated with a {@link java.net.SocketImpl} of the system-default type. * * @return a new Socket * * @throws UnsupportedOperationException * If SDP is not supported * @throws IOException * If an I/O error occurs */ public static Socket openSocket() throws IOException { SocketImpl impl = createSocketImpl(); return new SdpSocket(impl); } /** * Creates an unbound SDP server socket. The {@code ServerSocket} is * associated with a {@link java.net.SocketImpl} of the system-default type. * * @return a new ServerSocket * * @throws UnsupportedOperationException * If SDP is not supported * @throws IOException * If an I/O error occurs */ public static ServerSocket openServerSocket() throws IOException { // create ServerSocket via package-private constructor SocketImpl impl = createSocketImpl(); try { return serverSocketCtor.newInstance(impl); } catch (IllegalAccessException x) { throw new AssertionError(x); } catch (InstantiationException x) { throw new AssertionError(x); } catch (InvocationTargetException x) { Throwable cause = x.getCause(); if (cause instanceof IOException) throw (IOException)cause; if (cause instanceof RuntimeException) throw (RuntimeException)cause; throw new RuntimeException(x); } } /** * Opens a socket channel to a SDP socket. * * <p> The channel will be associated with the system-wide default * {@link java.nio.channels.spi.SelectorProvider SelectorProvider}. * * @return a new SocketChannel * * @throws UnsupportedOperationException * If SDP is not supported or not supported by the default selector * provider * @throws IOException * If an I/O error occurs. */ public static SocketChannel openSocketChannel() throws IOException { FileDescriptor fd = SdpSupport.createSocket(); return sun.nio.ch.Secrets.newSocketChannel(fd); } /** * Opens a socket channel to a SDP socket. * * <p> The channel will be associated with the system-wide default * {@link java.nio.channels.spi.SelectorProvider SelectorProvider}. * * @return a new ServerSocketChannel * * @throws UnsupportedOperationException * If SDP is not supported or not supported by the default selector * provider * @throws IOException * If an I/O error occurs */ public static ServerSocketChannel openServerSocketChannel() throws IOException { FileDescriptor fd = SdpSupport.createSocket(); return sun.nio.ch.Secrets.newServerSocketChannel(fd); } }

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  • Unreleased Resource: Streams

    - by Vibhas
    Hi freinds i am getting a warning in the fortify report for the following code: if (null != serverSocket) { OutputStream socketOutPutStream = serverSocket .getOutputStream(); if (null != socketOutPutStream) { oos = new ObjectOutputStream(socketOutPutStream); if (null != oos) { int c; log.info("i am in Step 3 ooss " + oos); while ((c = mergedIS.read()) != -1) { oos.writeByte(c); } } log.info("i am in Step 4 "); } } in the catch block i have mentioned : catch (UnknownHostException e) { //catch exception Vibhas added log.info("UnknownHostException occured"); } catch (IOException e) { //catch exception Vibhas added log.info("IOException occured"); } catch (Exception e) { //catch exception //log.info("error occured in copyFile in utils-->"+e.getMessage()+"file name is-->"+destiFileName); }finally{ if (null != oos){ oos.flush(); oos.close(); } catch (Exception e) { //catch exception } } Warning which i am getting in the fortify report is: Abstract: The function copyFile() in ODCUtil.java sometimes fails to release a system resource allocated by getOutputStream() on line 61. Sink: ODCUtil.java:64 oos = new ObjectOutputStream(socketOutPutStream)() 62 if (null != socketOutPutStream) { 63 64 oos = new ObjectOutputStream(socketOutPutStream); 65 if (null != oos) { 66 int c;

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  • NetworkOnMainThreadException while using AsyncTask

    - by Fansher
    Im making an app that uses the internet to retrive information. I get an NetworkOnMainThreadException as i tried to run it on 3.0 and above and have therefore tried to set it up using AsyncTask, but it still gives the exception and i don't know what is wrong. Oddly enough i read on this thread Android NetworkOnMainThreadException inside of AsyncTask that if you just removes the android:targetSdkVersion="10" statement from the manifest file it will be able to run. This works but i don't find it as the right solution to solve the problem this way. So if anyone can tell me what im doing wrong with the AsyncTask i will really appriciate it. Also if there is anybody that knows why removing the statement in the manifest makes it work, im really interested in that also. My code looks like this: public class MainActivity extends Activity { static ArrayList<Tumblr> tumblrs; ListView listView; TextView footer; int offset = 0; ProgressDialog pDialog; View v; String responseBody = null; HttpResponse r; HttpEntity e; String searchUrl; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); final ConnectivityManager conMgr = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); final NetworkInfo activeNetwork = conMgr.getActiveNetworkInfo(); if (activeNetwork != null && activeNetwork.isConnected()) { setContentView(R.layout.main); try { tumblrs = getTumblrs(); listView = (ListView) findViewById(R.id.list); View v = getLayoutInflater().inflate(R.layout.footer_layout, null); footer = (TextView) v.findViewById(R.id.tvFoot); listView.addFooterView(v); listView.setAdapter(new UserItemAdapter(this, R.layout.listitem)); } catch (ClientProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (JSONException e) { e.printStackTrace(); } new GetChicks().execute(); footer.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { new loadMoreListView().execute(); } }); } else { setContentView(R.layout.nonet); } } public class UserItemAdapter extends ArrayAdapter<Tumblr> { public UserItemAdapter(Context context, int imageViewResourceId) { super(context, imageViewResourceId, tumblrs); } @Override public View getView(int position, View convertView, ViewGroup parent) { View v = convertView; if (v == null) { LayoutInflater vi = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE); v = vi.inflate(R.layout.listitem, null); } Tumblr tumblr = tumblrs.get(position); if (tumblr != null) { ImageView image = (ImageView) v.findViewById(R.id.avatar); if (image != null) { image.setImageBitmap(getBitmap(tumblr.image_url)); } } return v; } } public Bitmap getBitmap(String bitmapUrl) { try { URL url = new URL(bitmapUrl); return BitmapFactory.decodeStream(url.openConnection() .getInputStream()); } catch (Exception ex) { return null; } } public ArrayList<Tumblr> getTumblrs() throws ClientProtocolException, IOException, JSONException { searchUrl = "http://api.tumblr.com/v2/blog/"webside"/posts?api_key=API_KEY"; ArrayList<Tumblr> tumblrs = new ArrayList<Tumblr>(); return tumblrs; } private class GetChicks extends AsyncTask<Void, Void, Void> { @Override protected Void doInBackground(Void... unused) { // TODO Auto-generated method stub runOnUiThread(new Runnable() { public void run() { HttpClient client = new DefaultHttpClient(); HttpGet get = new HttpGet(searchUrl); HttpResponse r = null; try { r = client.execute(get); int status = r.getStatusLine().getStatusCode(); if (status == 200) { e = r.getEntity(); responseBody = EntityUtils.toString(e); } } catch (ClientProtocolException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } catch (IOException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } JSONObject jsonObject; try { jsonObject = new JSONObject(responseBody); JSONArray posts = jsonObject.getJSONObject("response") .getJSONArray("posts"); for (int i = 0; i < posts.length(); i++) { JSONArray photos = posts.getJSONObject(i) .getJSONArray("photos"); for (int j = 0; j < photos.length(); j++) { JSONObject photo = photos.getJSONObject(j); String url = photo.getJSONArray("alt_sizes") .getJSONObject(0).getString("url"); Tumblr tumblr = new Tumblr(url); tumblrs.add(tumblr); } } } catch (JSONException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }); return null; } } public class Tumblr { public String image_url; public Tumblr(String url) { this.image_url = url; } } private class loadMoreListView extends AsyncTask<Void, Void, Void> { @Override protected void onPreExecute() { // Showing progress dialog before sending http request pDialog = new ProgressDialog(MainActivity.this); pDialog.setMessage("More chicks coming up.."); pDialog.setIndeterminate(true); pDialog.setCancelable(false); pDialog.show(); } @Override protected Void doInBackground(Void... unused) { // TODO Auto-generated method stub runOnUiThread(new Runnable() { public void run() { // increment current page offset += 2; // Next page request tumblrs.clear(); String searchUrl = "http://api.tumblr.com/v2/blog/"webside"/posts?api_key=API_KEY&limit=2 + offset; HttpClient client = new DefaultHttpClient(); HttpGet get = new HttpGet(searchUrl); HttpResponse r = null; try { r = client.execute(get); int status = r.getStatusLine().getStatusCode(); if (status == 200) { HttpEntity e = r.getEntity(); responseBody = EntityUtils.toString(e); } } catch (ClientProtocolException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } catch (IOException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } JSONObject jsonObject; try { jsonObject = new JSONObject(responseBody); JSONArray posts = jsonObject.getJSONObject("response") .getJSONArray("posts"); for (int i = 0; i < posts.length(); i++) { JSONArray photos = posts.getJSONObject(i) .getJSONArray("photos"); for (int j = 0; j < photos.length(); j++) { JSONObject photo = photos.getJSONObject(j); String url = photo.getJSONArray("alt_sizes") .getJSONObject(0).getString("url"); Tumblr tumblr = new Tumblr(url); tumblrs.add(tumblr); } } } catch (JSONException e) { // TODO Auto-generated catch block e.printStackTrace(); } // Setting new scroll position listView.setSelectionFromTop(0, 0); } }); return null; } protected void onPostExecute(Void unused) { pDialog.dismiss(); } } @Override public boolean onCreateOptionsMenu(android.view.Menu menu) { // TODO Auto-generated method stub super.onCreateOptionsMenu(menu); MenuInflater blowUp = getMenuInflater(); blowUp.inflate(R.menu.cool_menu, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // TODO Auto-generated method stub switch (item.getItemId()) { case R.id.aboutUs: Intent i = new Intent("com.example.example.ABOUT"); startActivity(i); break; case R.id.refresh: Intent f = new Intent(MainActivity.this, MainActivity.class); startActivity(f); finish(); break; case R.id.exit: finish(); break; } return false; } } Thanks for helping out.

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  • Exception Handling Differences Between 32/64 Bit

    - by Alois Kraus
    I do quite a bit of debugging .NET applications but from time to time I see things that are impossible (at a first look). I may ask you dear reader what your mental exception handling model is. Exception handling is easy after all right? Lets suppose the following code:         private void F1(object sender, EventArgs e)         {             try             {                 F2();             }             catch (Exception ex)             {                 throw new Exception("even worse Exception");             }           }           private void F2()         {             try             {                 F3();             }             finally             {                 throw new Exception("other exception");             }         }           private void F3()         {             throw new NotImplementedException();         }   What will the call stack look like when you break into the catch(Exception) clause in Windbg (32 and 64 bit on .NET 3.5 SP1)? The mental model I have is that when an exception is thrown the stack frames are unwound until the catch handler can execute. An exception does propagate the call chain upwards.   So when F3 does throw an exception the control flow will resume at the finally handler in F2 which does throw another exception hiding the original one (that is nasty) and then the new Exception will be catched in F1 where the catch handler is executed. So we should see in the catch handler in F1 as call stack only the F1 stack frame right? Well lets try it out in Windbg. For this I created a simple Windows Forms application with one button which does execute the F1 method in its click handler. When you compile the application for 64 bit and the catch handler is reached you will find with the following commands in Windbg   Load sos extension from the same path where mscorwks was loaded in the current process .loadby sos mscorwks   Beak on clr exceptions sxe clr   Continue execution g   Dump mixed call stack container C++  and .NET Stacks interleaved 0:000> !DumpStack OS Thread Id: 0x1d8 (0) Child-SP         RetAddr          Call Site 00000000002c88c0 000007fefa68f0bd KERNELBASE!RaiseException+0x39 00000000002c8990 000007fefac42ed0 mscorwks!RaiseTheExceptionInternalOnly+0x295 00000000002c8a60 000007ff005dd7f4 mscorwks!JIT_Throw+0x130 00000000002c8c10 000007fefa6942e1 WindowsFormsApplication1!WindowsFormsApplication1.Form1.F1(System.Object, System.EventArgs)+0xb4 00000000002c8c60 000007fefa661012 mscorwks!ExceptionTracker::CallHandler+0x145 00000000002c8d60 000007fefa711a72 mscorwks!ExceptionTracker::CallCatchHandler+0x9e 00000000002c8df0 0000000077b055cd mscorwks!ProcessCLRException+0x25e 00000000002c8e90 0000000077ae55f8 ntdll!RtlpExecuteHandlerForUnwind+0xd 00000000002c8ec0 000007fefa637c1a ntdll!RtlUnwindEx+0x539 00000000002c9560 000007fefa711a21 mscorwks!ClrUnwindEx+0x36 00000000002c9a70 0000000077b0554d mscorwks!ProcessCLRException+0x20d 00000000002c9b10 0000000077ae5d1c ntdll!RtlpExecuteHandlerForException+0xd 00000000002c9b40 0000000077b1fe48 ntdll!RtlDispatchException+0x3cb 00000000002ca220 000007fefdaeaa7d ntdll!KiUserExceptionDispatcher+0x2e 00000000002ca7e0 000007fefa68f0bd KERNELBASE!RaiseException+0x39 00000000002ca8b0 000007fefac42ed0 mscorwks!RaiseTheExceptionInternalOnly+0x295 00000000002ca980 000007ff005dd8df mscorwks!JIT_Throw+0x130 00000000002cab30 000007fefa6942e1 WindowsFormsApplication1!WindowsFormsApplication1.Form1.F2()+0x9f 00000000002cab80 000007fefa71b5b3 mscorwks!ExceptionTracker::CallHandler+0x145 00000000002cac80 000007fefa70dcd0 mscorwks!ExceptionTracker::ProcessManagedCallFrame+0x683 00000000002caed0 000007fefa7119af mscorwks!ExceptionTracker::ProcessOSExceptionNotification+0x430 00000000002cbd90 0000000077b055cd mscorwks!ProcessCLRException+0x19b 00000000002cbe30 0000000077ae55f8 ntdll!RtlpExecuteHandlerForUnwind+0xd 00000000002cbe60 000007fefa637c1a ntdll!RtlUnwindEx+0x539 00000000002cc500 000007fefa711a21 mscorwks!ClrUnwindEx+0x36 00000000002cca10 0000000077b0554d mscorwks!ProcessCLRException+0x20d 00000000002ccab0 0000000077ae5d1c ntdll!RtlpExecuteHandlerForException+0xd 00000000002ccae0 0000000077b1fe48 ntdll!RtlDispatchException+0x3cb 00000000002cd1c0 000007fefdaeaa7d ntdll!KiUserExceptionDispatcher+0x2e 00000000002cd780 000007fefa68f0bd KERNELBASE!RaiseException+0x39 00000000002cd850 000007fefac42ed0 mscorwks!RaiseTheExceptionInternalOnly+0x295 00000000002cd920 000007ff005dd968 mscorwks!JIT_Throw+0x130 00000000002cdad0 000007ff005dd875 WindowsFormsApplication1!WindowsFormsApplication1.Form1.F3()+0x48 00000000002cdb10 000007ff005dd786 WindowsFormsApplication1!WindowsFormsApplication1.Form1.F2()+0x35 00000000002cdb60 000007ff005dbe6a WindowsFormsApplication1!WindowsFormsApplication1.Form1.F1(System.Object, System.EventArgs)+0x46 00000000002cdbc0 000007ff005dd452 System_Windows_Forms!System.Windows.Forms.Control.OnClick(System.EventArgs)+0x5a   Hm okaaay. I see my method F1 two times in this call stack. Looks like we did get some recursion bug. But that can´t be given the obvious code above. Let´s try the same thing in a 32 bit process.  0:000> !DumpStack OS Thread Id: 0x33e4 (0) Current frame: KERNELBASE!RaiseException+0x58 ChildEBP RetAddr  Caller,Callee 0028ed38 767db727 KERNELBASE!RaiseException+0x58, calling ntdll!RtlRaiseException 0028ed4c 68b9008c mscorwks!Binder::RawGetClass+0x20, calling mscorwks!Module::LookupTypeDef 0028ed5c 68b904ff mscorwks!Binder::IsClass+0x23, calling mscorwks!Binder::RawGetClass 0028ed68 68bfb96f mscorwks!Binder::IsException+0x14, calling mscorwks!Binder::IsClass 0028ed78 68bfb996 mscorwks!IsExceptionOfType+0x23, calling mscorwks!Binder::IsException 0028ed80 68bfbb1c mscorwks!RaiseTheExceptionInternalOnly+0x2a8, calling KERNEL32!RaiseExceptionStub 0028eda8 68ba0713 mscorwks!Module::ResolveStringRef+0xe0, calling mscorwks!BaseDomain::GetStringObjRefPtrFromUnicodeString 0028edc8 68b91e8d mscorwks!SetObjectReferenceUnchecked+0x19 0028ede0 68c8e910 mscorwks!JIT_Throw+0xfc, calling mscorwks!RaiseTheExceptionInternalOnly 0028ee44 68c8e734 mscorwks!JIT_StrCns+0x22, calling mscorwks!LazyMachStateCaptureState 0028ee54 68c8e865 mscorwks!JIT_Throw+0x1e, calling mscorwks!LazyMachStateCaptureState 0028eea4 02ffaecd (MethodDesc 0x7af08c +0x7d WindowsFormsApplication1.Form1.F1(System.Object, System.EventArgs)), calling mscorwks!JIT_Throw 0028eeec 02ffaf19 (MethodDesc 0x7af098 +0x29 WindowsFormsApplication1.Form1.F2()), calling 06370634 0028ef58 02ffae37 (MethodDesc 0x7a7bb0 +0x4f System.Windows.Forms.Control.OnClick(System.EventArgs))   That does look more familar. The call stack has been unwound and we do see only some frames into the history where the debugger was smart enough to find out that we have called F2 from F1. The exception handling on 64 bit systems does work quite differently which seems to have the nice property to remember the called methods not only during the first pass of exception filter clauses (during first pass all catch handler are called if they are going to catch the exception which is about to be thrown)  but also when the actual stack unwind has taken place. This makes it possible to follow not only the call stack right at the moment but also to look into the “history” of the catch/finally clauses. In a 64 bit process you only need to look at the ExceptionTracker to find out if a catch or finally handler was called. The two frames ProcessManagedCallFrame/CallHandler does indicate a finally clause whereas CallCatchHandler/CallHandler indicates a catch clause. That was a interesting one. Oh and by the way if you manage to load the Microsoft symbols you can also find out the hidden exception which. When you encounter in the call stack a line 0016eb34 75b79617 KERNELBASE!RaiseException+0x58 ====> Exception Code e0434f4d cxr@16e850 exr@16e838 Then it is a good idea to execute .exr 16e838 !analyze –v to find out more. In the managed world it is even easier since we can dump the objects allocated on the stack which have not yet been garbage collected to look at former method parameters. The command !dso which is the abbreviation for dump stack objects will give you 0:000> !dso OS Thread Id: 0x46c (0) ESP/REG  Object   Name 0016dd4c 020737f0 System.Exception 0016dd98 020737f0 System.Exception 0016dda8 01f5c6cc System.Windows.Forms.Button 0016ddac 01f5d2b8 System.EventHandler 0016ddb0 02071744 System.Windows.Forms.MouseEventArgs 0016ddc0 01f5d2b8 System.EventHandler 0016ddcc 01f5c6cc System.Windows.Forms.Button 0016dddc 020737f0 System.Exception 0016dde4 01f5d2b8 System.EventHandler 0016ddec 02071744 System.Windows.Forms.MouseEventArgs 0016de40 020737f0 System.Exception 0016de80 02071744 System.Windows.Forms.MouseEventArgs 0016de8c 01f5d2b8 System.EventHandler 0016de90 01f5c6cc System.Windows.Forms.Button 0016df10 02073784 System.SByte[] 0016df5c 02073684 System.NotImplementedException 0016e2a0 02073684 System.NotImplementedException 0016e2e8 01ed69f4 System.Resources.ResourceManager From there it is easy to do 0:000> !pe 02073684 Exception object: 02073684 Exception type: System.NotImplementedException Message: Die Methode oder der Vorgang sind nicht implementiert. InnerException: <none> StackTrace (generated):     SP       IP       Function     0016ECB0 006904AD WindowsFormsApplication2!WindowsFormsApplication2.Form1.F3()+0x35     0016ECC0 00690411 WindowsFormsApplication2!WindowsFormsApplication2.Form1.F2()+0x29     0016ECF0 0069038F WindowsFormsApplication2!WindowsFormsApplication2.Form1.F1(System.Object, System.EventArgs)+0x3f StackTraceString: <none> HResult: 80004001 to see the former exception. That´s all for today.

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  • CLR 4.0: Corrupted State Exceptions

    - by Scott Dorman
    Corrupted state exceptions are designed to help you have fewer bugs in your code by making it harder to make common mistakes around exception handling. A very common pattern is code like this: public void FileSave(String name) { try { FileStream fs = new FileStream(name, FileMode.Create); } catch (Exception e) { MessageBox.Show("File Open Error"); throw new Exception(IOException); } The standard recommendation is not to catch System.Exception but rather catch the more specific exceptions (in this case, IOException). While this is a somewhat contrived example, what would happen if Exception were really an AccessViolationException or some other exception indicating that the process state has been corrupted? What you really want to do is get out fast before persistent data is corrupted or more work is lost. To help solve this problem and minimize the chance that you will catch exceptions like this, CLR 4.0 introduces Corrupted State Exceptions, which cannot be caught by normal catch statements. There are still places where you do want to catch these types of exceptions, particularly in your application’s “main” function or when you are loading add-ins.  There are also rare circumstances when you know code that throws an exception isn’t dangerous, such as when calling native code. In order to support these scenarios, a new HandleProcessCorruptedStateExceptions attribute has been added. This attribute is added to the function that catches these exceptions. There is also a process wide compatibility switch named legacyCorruptedStateExceptionsPolicy which when set to true will cause the code to operate under the older exception handling behavior. Technorati Tags: CLR 4.0, .NET 4.0, Exception Handling, Corrupted State Exceptions

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  • Good SQL error handling in Strored Procedure

    - by developerit
    When writing SQL procedures, it is really important to handle errors cautiously. Having that in mind will probably save your efforts, time and money. I have been working with MS-SQL 2000 and MS-SQL 2005 (I have not got the opportunity to work with MS-SQL 2008 yet) for many years now and I want to share with you how I handle errors in T-SQL Stored Procedure. This code has been working for many years now without a hitch. N.B.: As antoher "best pratice", I suggest using only ONE level of TRY … CATCH and only ONE level of TRANSACTION encapsulation, as doing otherwise may not be 100% sure. BEGIN TRANSACTION; BEGIN TRY -- Code in transaction go here COMMIT TRANSACTION; END TRY BEGIN CATCH -- Rollback on error ROLLBACK TRANSACTION; -- Raise the error with the appropriate message and error severity DECLARE @ErrMsg nvarchar(4000), @ErrSeverity int; SELECT @ErrMsg = ERROR_MESSAGE(), @ErrSeverity = ERROR_SEVERITY(); RAISERROR(@ErrMsg, @ErrSeverity, 1); END CATCH; In conclusion, I will just mention that I have been using this code with .NET 2.0 and .NET 3.5 and it works like a charm. The .NET TDS parser throws back a SQLException which is ideal to work with.

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  • Subterranean IL: Exception handling 2

    - by Simon Cooper
    Control flow in and around exception handlers is tightly controlled, due to the various ways the handler blocks can be executed. To start off with, I'll describe what SEH does when an exception is thrown. Handling exceptions When an exception is thrown, the CLR stops program execution at the throw statement and searches up the call stack looking for an appropriate handler; catch clauses are analyzed, and filter blocks are executed (I'll be looking at filter blocks in a later post). Then, when an appropriate catch or filter handler is found, the stack is unwound to that handler, executing successive finally and fault handlers in their own stack contexts along the way, and program execution continues at the start of the catch handler. Because catch, fault, finally and filter blocks can be executed essentially out of the blue by the SEH mechanism, without any reference to preceding instructions, you can't use arbitary branches in and out of exception handler blocks. Instead, you need to use specific instructions for control flow out of handler blocks: leave, endfinally/endfault, and endfilter. Exception handler control flow try blocks You cannot branch into or out of a try block or its handler using normal control flow instructions. The only way of entering a try block is by either falling through from preceding instructions, or by branching to the first instruction in the block. Once you are inside a try block, you can only leave it by throwing an exception or using the leave <label> instruction to jump to somewhere outside the block and its handler. The leave instructions signals the CLR to execute any finally handlers around the block. Most importantly, you cannot fall out of the block, and you cannot use a ret to return from the containing method (unlike in C#); you have to use leave to branch to a ret elsewhere in the method. As a side effect, leave empties the stack. catch blocks The only way of entering a catch block is if it is run by the SEH. At the start of the block execution, the thrown exception will be the only thing on the stack. The only way of leaving a catch block is to use throw, rethrow, or leave, in a similar way to try blocks. However, one thing you can do is use a leave to branch back to an arbitary place in the handler's try block! In other words, you can do this: .try { // ... newobj instance void [mscorlib]System.Exception::.ctor() throw MidTry: // ... leave.s RestOfMethod } catch [mscorlib]System.Exception { // ... leave.s MidTry } RestOfMethod: // ... As far as I know, this mechanism is not exposed in C# or VB. finally/fault blocks The only way of entering a finally or fault block is via the SEH, either as the result of a leave instruction in the corresponding try block, or as part of handling an exception. The only way to leave a finally or fault block is to use endfinally or endfault (both compile to the same binary representation), which continues execution after the finally/fault block, or, if the block was executed as part of handling an exception, signals that the SEH can continue walking the stack. filter blocks I'll be covering filters in a separate blog posts. They're quite different to the others, and have their own special semantics. Phew! Complicated stuff, but it's important to know if you're writing or outputting exception handlers in IL. Dealing with the C# compiler is probably best saved for the next post.

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  • Optimizing a thread safe Java NIO / Serialization / FIFO Queue [migrated]

    - by trialcodr
    I've written a thread safe, persistent FIFO for Serializable items. The reason for reinventing the wheel is that we simply can't afford any third party dependencies in this project and want to keep this really simple. The problem is it isn't fast enough. Most of it is undoubtedly due to reading and writing directly to disk but I think we should be able to squeeze a bit more out of it anyway. Any ideas on how to improve the performance of the 'take'- and 'add'-methods? /** * <code>DiskQueue</code> Persistent, thread safe FIFO queue for * <code>Serializable</code> items. */ public class DiskQueue<ItemT extends Serializable> { public static final int EMPTY_OFFS = -1; public static final int LONG_SIZE = 8; public static final int HEADER_SIZE = LONG_SIZE * 2; private InputStream inputStream; private OutputStream outputStream; private RandomAccessFile file; private FileChannel channel; private long offs = EMPTY_OFFS; private long size = 0; public DiskQueue(String filename) { try { boolean fileExists = new File(filename).exists(); file = new RandomAccessFile(filename, "rwd"); if (fileExists) { size = file.readLong(); offs = file.readLong(); } else { file.writeLong(size); file.writeLong(offs); } } catch (FileNotFoundException e) { throw new RuntimeException(e); } catch (IOException e) { throw new RuntimeException(e); } channel = file.getChannel(); inputStream = Channels.newInputStream(channel); outputStream = Channels.newOutputStream(channel); } /** * Add item to end of queue. */ public void add(ItemT item) { try { synchronized (this) { channel.position(channel.size()); ObjectOutputStream s = new ObjectOutputStream(outputStream); s.writeObject(item); s.flush(); size++; file.seek(0); file.writeLong(size); if (offs == EMPTY_OFFS) { offs = HEADER_SIZE; file.writeLong(offs); } notify(); } } catch (IOException e) { throw new RuntimeException(e); } } /** * Clears overhead by moving the remaining items up and shortening the file. */ public synchronized void defrag() { if (offs > HEADER_SIZE && size > 0) { try { long totalBytes = channel.size() - offs; ByteBuffer buffer = ByteBuffer.allocateDirect((int) totalBytes); channel.position(offs); for (int bytes = 0; bytes < totalBytes;) { int res = channel.read(buffer); if (res == -1) { throw new IOException("Failed to read data into buffer"); } bytes += res; } channel.position(HEADER_SIZE); buffer.flip(); for (int bytes = 0; bytes < totalBytes;) { int res = channel.write(buffer); if (res == -1) { throw new IOException("Failed to write buffer to file"); } bytes += res; } offs = HEADER_SIZE; file.seek(LONG_SIZE); file.writeLong(offs); file.setLength(HEADER_SIZE + totalBytes); } catch (IOException e) { throw new RuntimeException(e); } } } /** * Returns the queue overhead in bytes. */ public synchronized long overhead() { return (offs == EMPTY_OFFS) ? 0 : offs - HEADER_SIZE; } /** * Returns the first item in the queue, blocks if queue is empty. */ public ItemT peek() throws InterruptedException { block(); synchronized (this) { if (offs != EMPTY_OFFS) { return readItem(); } } return peek(); } /** * Returns the number of remaining items in queue. */ public synchronized long size() { return size; } /** * Removes and returns the first item in the queue, blocks if queue is empty. */ public ItemT take() throws InterruptedException { block(); try { synchronized (this) { if (offs != EMPTY_OFFS) { ItemT result = readItem(); size--; offs = channel.position(); file.seek(0); if (offs == channel.size()) { truncate(); } file.writeLong(size); file.writeLong(offs); return result; } } return take(); } catch (IOException e) { throw new RuntimeException(e); } } /** * Throw away all items and reset the file. */ public synchronized void truncate() { try { offs = EMPTY_OFFS; file.setLength(HEADER_SIZE); size = 0; } catch (IOException e) { throw new RuntimeException(e); } } /** * Block until an item is available. */ protected void block() throws InterruptedException { while (offs == EMPTY_OFFS) { try { synchronized (this) { wait(); file.seek(LONG_SIZE); offs = file.readLong(); } } catch (IOException e) { throw new RuntimeException(e); } } } /** * Read and return item. */ @SuppressWarnings("unchecked") protected ItemT readItem() { try { channel.position(offs); return (ItemT) new ObjectInputStream(inputStream).readObject(); } catch (ClassNotFoundException e) { throw new RuntimeException(e); } catch (IOException e) { throw new RuntimeException(e); } } }

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  • My java program seems to be skipping over the try{}, executing the catch{} and then throwing a NullPointerException. What should I do?

    - by Matt Bolopue
    I am writing a program that calculates the number of words, syllables, and sentences in any given text file. I don't need help finding those numbers, however my program (which currently should only find the number of words in the text file) will not import the text file even when I type in the name of the file correctly. The text file is in the same folder as the source code. Instead it tells me every time that what I typed in has the wrong file extension (see my catch{}) and then proceeds to throw a null pointer. I am at a loss for what could be causing it. Any suggestions? import java.io.*; import java.util.*; public class Reading_Lvl_Calc { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub int words = 0; String fileName; Scanner scan; Scanner keyread = new Scanner(System.in); System.out.println("Please enter a file name (or QUIT to exit)"); fileName = keyread.nextLine(); File doc = new File(fileName); //while(scan.equals(null)){ try { scan = new Scanner(doc); } catch(Exception e) { if(fileName.substring(fileName.indexOf(".")) != ".txt") System.out.println("I'm sorry, the file \"" + fileName + "\" has an invalid file extension."); else System.out.println("I am sorry, the file \"" + fileName + " \" cannot be found.\n The file must be in the same directory as this program"); scan = null; } // } while(scan.hasNext()){ words++; scan.next(); } System.out.println(words); } }

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