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• Administrator's shortcut to batch file with double quoted parameters

  - by XXB

  Take an excruciatingly simple batch file: echo hi pause Save that as test.bat. Now, make a shortcut to test.bat. The shortcut runs the batch file, which prints "hi" and then waits for a keypress as expected. Now, add some argument to the target of the shortcut. Now you have a shortcut to: %path%\test.bat some args The shortcut runs the batch file as before. Now, run the shortcut as administrator. (This is on Windows 7 by the way.) You can use either right-click - Run as Administrator, or go to the shortcut's properties and check the box in the advanced section. Tell UAC that it's okay and once again the shortcut runs the batch file as expected. Now, change the arguments in the target of the shortcut to add double quotes: %path%\test.bat "some args" Now try the shortcut as administrator. It doesn't work this time! A command window pops up and and disappears too fast to see any error. I tried adding test.log 2&1 to the shortcut, but no log is created in this case. Try running the same shortcut (with the double quotes) but not as Administrator. It runs the batch file fine. So, it seems the behavior is not because of the double quoted parameters, and it's not because it's run as Administrator. It's some weird combination of the two. I also tried running the same command from an administrator's command window. This ran the batch file as expected without error. Running the shortcut from the command window spawned a new command window which flashed and went away. So apparently the issue is caused by a combination of administrator, the shortcut, and the double quotes. I'm totally stumped, does anyone have any idea what's going on?

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• How to clean-up an Entity Framework object context?

  - by Daniel Brückner

  I am adding several entities to an object context. try { forach (var document in documents) { this.Validate(document); // May throw a ValidationException. this.objectContext.AddToDocuments(document); } this.objectContext.SaveChanges(); } catch { // How to clean-up the object context here? throw; } If some of the documents pass the the validation and one fails, all documents that passed the validation remain added to the object context. I have to clean-up the object context because it may be reused and the following can happen. var documentA = new Document { Id = 1, Data = "ValidData" }; var documentB = new Document { Id = 2, Data = "InvalidData" }; var documentC = new Document { Id = 3, Data = "ValidData" }; try { // Adding document B will cause a ValidationException but only // after document A is added to the object context. this.DocumentStore.AddDocuments(new[] { documentA, documentB, documentC }); } catch (ValidationException) { } // Try again without the invalid document B. this.DocumentStore.AddDocuments(new[] { documentA, documentC }); This will again add document A to the object context and in consequence SaveChanges() will throw an exception because of a duplicate primary key. So I have to remove all already added documents in the case of an validation error. I could of course perform the validation first and only add all documents after they have been successfully validated. But sadly this does not solve the whole problem - if SaveChanges() fails all documents still remain add but unsaved. I tried to detach all objects returned by this.objectContext.ObjectStateManager.GetObjectStateEntries(EntityState.Added) but I am getting a exception stating that the object is not attached. So how do I get rid of all added but unsaved objects?

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• Moq for Silverlight doesn't raise event

  - by Budda

  Trying to write Unit test for Silverlight 4.0 using Moq 4.0.10531.7 public delegate void DataReceived(ObservableCollection<TeamPlayerData> AllReadyPlayers, GetSquadDataCompletedEventArgs squadDetails); public interface ISquadModel : IModelBase { void RequestData(int matchId, int teamId); void SaveData(); event DataReceived DataReceivedEvent; } void MyTest() { Mock<ISquadModel> mockSquadModel = new Mock<ISquadModel>(); mockSquadModel.Raise(model => model.DataReceivedEvent += null, EventArgs.Empty); } Instead of raising the 'DataReceivingEvent' the following error is received: Object of type 'Castle.Proxies.ISquadModelProxy' cannot be converted to type 'System.Collections.ObjectModel.ObservableCollection`1[TeamPlayerData]'. Why attempt to convert mock to the type of 1st event parameter is performed? How can I raise an event? I've also tried another approach: mockSquadModel .Setup(model => model.RequestData(TestMatchId, TestTeamId)) .Raises(model => model.DataReceivedEvent += null, EventArgs.Empty) ; this should raise event if case somebody calls 'Setup' method... Instead the same error is generated... Any thoughts are welcome. Thanks

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• PDFView printWithInfo:autoRotate: fails

  - by Brian Postow

  I'm trying to print a PDFDocument that I am constructing from a series of images. In case it matters, I'm doing all of this from within a Mozilla plugin. I create the PDFDocument, and put it into a PDFView, then I call [printView printWithInfo: [NSPrintInfo sharedPrintInfo] autoRotate: YES]; The print dialog comes up (as a separate window, instead of panel. I assume that that comes from being inside a mozilla window, so I wasn't too worried about it. The dialog shows my document, and I can page through it correctly, and everything looks good. However, when I hit "Print" the dropdown with "Layout" etc becomes empty, and the view under that becomes empty. The window doesn't disappear, and the document doesn't print. Hitting Cancel does exactly the same thing. The only thing I can do then is force-quit Mozillla. I based the program off of PDFKitLinker2 from the apple dev site, and that program works. But I can't see any significant differences between it and my version. Any suggestions on where to look? thanks. EDIT: Yes, I know that this is pretty much an exact duplicate of http://stackoverflow.com/questions/2058501/printing-off-screen-pdfviews but that never got a sufficient answer... (And I didn't notice it until just now...)

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• Incoming connections from 2 different Internet connections

  - by RJClinton

  I am hosting a Gameserver on my Windows 2003 Server 32 Bit Server. Due to some limitations of my ISP, I have to take 2 Internet connections in order to satisfy my bandwidth requirement. I am facing serious problems here. The Internet is supplied using Wimax. I am given a POE and the RJ45 from both the POE (2 connections) are plugged into a Netgear 100mbps Switch and another RJ45 connects the server to the switch. I have tried to configure the IP addresses and gateway of both connections to the single NIC in the server. The IP series and the gateway of each Internet connection are very much different. I know that this is not the proper approach, because alternate gateways are meant to be only for backup in case of main gateway failure and the usage of the gateways depends upon the metric (correct me if I am wrong). I am planning to get a second PCI NIC so that I can connect each of the Internet connections into its respective NIC. If I use this approach, will I be able to accept connections on both NICs? Also, please suggest any other alternatives that I might use.

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• AbstractMethodError when invoking createArrayOf, with postgresql 8.4 jdbc4 and JBoss 5.1GA

  - by Francesco

  Hi, when using this method public List<Field> getFieldWithoutId(List<Integer> idSections) throws Exception { try { Connection conn = this.getConnection(); Array arraySections = conn.createArrayOf("int4", idSections.toArray()); this.log.info("Recupero field"); List<Field> fields = this.getJdbcTemplate().query(getFieldWithoutIdQuery, new Object[] {arraySections},ParameterizedBeanPropertyRowMapper.newInstance(Field.class)); /*if (!conn.isClosed()) conn.close(); */ releaseConnection(conn); return fields; } catch (Exception e) { e.printStackTrace(); throw new Exception("Errore."); } } I have an exception at conn.createArrayOf("int4", idSections.toArray());. The exception is: javax.ejb.EJBException : Unexpected Error java.lang.AbstractMethodError: org.jboss.resource.adapter.jdbc.jdk5.WrappedConnectionJDK5.createArrayOf(Ljava/lang/String;[Ljava/lang/Object;)Ljava/sql/Array; postgresql-8.4-701.jdbc4.jar is in jboss/server/all/lib dir. Application is spring based with ejb3. When working locally with the same setup everything is fine. This only happens on a preproduction environment. Only difference is locally I have jboss run in default mode, in the other case there are 2 jbosses in all configuration. I can't track down the cause of this error. Could someone help me please?

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• Named pipe blocking with user nobody

  - by dnagirl

  I have 2 short scripts. The first, an awk script, processes a large file and prints to a named pipe 'myfifo.dat'. The second, a Perl script, runs a LOAD DATA LOCAL INFILE 'myfifo.dat'... command. Both of these scripts work when run locally like so: lee.awk big.file & lee.pl However, when I call these scripts from a PHP webpage, the named pipe blocks: $awk="/path/to/lee.awk {$_FILES['uploadfile']['tmp_name']} &"; $sql="/path/to/lee.pl"; if(!exec($awk,$return,$err)) throw new ZException(print_r($err,true)); //blocks here if(!exec($sql,$return,$err)) throw new ZException(print_r($err,true)); If I modify the awk and Perl scripts so that they write and read to a normal file, everything works fine from PHP. The permissions on the fifo and the normal file are 666 (for testing purposes). These operations run much more quickly through a named pipe, so I'd prefer to use one. Any ideas how to unblock it? ps. In case you're wondering why I'm going to all this aggravation, see this SO question.

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• Django custom managers - how do I return only objects created by the logged-in user?

  - by Tom Tom

  I want to overwrite the custom objects model manager to only return objects a specific user created. Admin users should still return all objects using the objects model manager. Now I have found an approach that could work. They propose to create your own middleware looking like this: #### myproject/middleware/threadlocals.py try: from threading import local except ImportError: # Python 2.3 compatibility from django.utils._threading_local import local _thread_locals = local() def get_current_user(): return getattr(_thread_locals, 'user', None) class ThreadLocals(object): """Middleware that gets various objects from the request object and saves them in thread local storage.""" def process_request(self, request): _thread_locals.user = getattr(request, 'user', None) #### end And in the Custom manager you could call the get_current_user() method to return only objects a specific user created. class UserContactManager(models.Manager): def get_query_set(self): return super(UserContactManager, self).get_query_set().filter(creator=get_current_user()) Is this a good approach to this use-case? Will this work? Or is this like "using a sledgehammer to crack a nut" ? ;-) Just using: Contact.objects.filter(created_by= user) in each view doesn`t look very neat to me. EDIT Do not use this middleware approach !!! use the approach stated by Jack M. below After a while of testing this approach behaved pretty strange and with this approach you mix up a global-state with a current request. Use the approach presented below. It is really easy and no need to hack around with the middleware. create a custom manager in your model with a function that expects the current user or any other user as an input. #in your models.py class HourRecordManager(models.Manager): def for_user(self, user): return self.get_query_set().filter(created_by=user) class HourRecord(models.Model): #Managers objects = HourRecordManager() #in vour view you can call the manager like this and get returned only the objects from the currently logged-in user. hr_set = HourRecord.objects.for_user(request.user)

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• Rails: keeping DRY with ActiveRecord models that share similar complex attributes

  - by Greg

  This seems like it should have a straightforward answer, but after much time on Google and SO I can't find it. It might be a case of missing the right keywords. In my RoR application I have several models that share a specific kind of string attribute that has special validation and other functionality. The closest similar example I can think of is a string that represents a URL. This leads to a lot of duplication in the models (and even more duplication in the unit tests), but I'm not sure how to make it more DRY. I can think of several possible directions... create a plugin along the lines of the "validates_url_format_of" plugin, but that would only make the validations DRY give this special string its own model, but this seems like a very heavy solution create a ruby class for this special string, but how do I get ActiveRecord to associate this class with the model attribute that is a string in the db Number 3 seems the most reasonable, but I can't figure out how to extend ActiveRecord to handle anything other than the base data types. Any pointers? Finally, if there is a way to do this, where in the folder hierarchy would you put the new class that is not a model? Many thanks.

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• What causes exception in string.concat

  - by Budda

  Here are few classes: public class MyItem : ParamOut { public string Code { get { return _quoteCode; } } public InnerItem[] Skus { get { return _skus; } } public PriceSummary Price { get { return _price; } } public override string ToString() { return string.Concat("Code=", Code, "; SKUs=[", Skus != null ? "{" + string.Join("},{", Array.ConvertAll(Skus, item => item.ToString())) + "}" : "", "]" , "; Price={", Price.ToString(), "}", base.ToString() ); } ... } public abstract class ParamOut { public override string ToString() { return null; } public string ErrorMessage { get; set; } } Here is calling functionality: { MyItem item = new MyItem{ ErrorMessage = "Bla-bla-bla" }; string text = item.ToString(); } I am getting NullReference exception inside of 'ToString()' method (each property of item variable is null). Question: Q1. what overload of string.Concat will be called in this case? I have 9 parameters, so I guess one of the following: public static string Concat(params Object[] args) or public static string Concat(params string[] values) But which of them? Q2. Why exception is generated? Shouldn't 'null' be converted into something like 'null' or "" (empty string)? Thanks a lot!

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• x86 opcode alignment references and guidelines

  - by mrjoltcola

  I'm generating some opcodes dynamically in a JIT compiler and I'm looking for guidelines for opcode alignment. 1) I've read comments that briefly "recommend" alignment by adding nops after calls 2) I've also read about using nop for optimizing sequences for parallelism. 3) I've read that alignment of ops is good for "cache" performance Usually these comments don't give any supporting references. Its one thing to read a blog or a comment that says, "its a good idea to do such and such", but its another to actually write a compiler that implements specific op sequences and realize most material online, especially blogs, are not useful for practical application. So I'm a believer in finding things out myself (disassembly, etc. to see what real world apps do). This is one case where I need some outside info. I notice compilers will usually start an odd byte instruction immediately after whatever previous instruction sequence there was. So the compiler is not taking any special care in most cases. I see "nop" here or there, but usually it seems nop is used sparingly, if at all. How critical is opcode alignment? Can you provide references for cases that I can actually use for implementation? Thanks.

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• help in the Donalds B. Johnson's algorithm, i cannot understand the pseudo code

  - by Pitelk

  Hi , does anyone know the Donald B. Johnson's algorithm which enumarates all the elementary circuits (cycles) in a Directed graph? link text I have the paper he had published in 1975 but I cannot understand the pseudo-code. My goal is to implement this algorithm in java. Some questions i have is for example what is the matrix Ak it refers to. In the pseudo code mentions that Ak:=adjacency structure of strong component K with least vertex in subgraph of G induced by {s,s+1,....n}; Does that mean i have to implement another algorithm that finds the Ak matrix? Another question is what the following means? begin logical f; Does also the line "logical procedure CIRCUIT (integer value v);" means that the circuit procedure returns a logical variable. In the pseudo code also has the line "CIRCUIT := f;" . Does this mean? It would be great if someone could translate this 1970's pseudocode to a more modern type of pseudo code so i can understand it in case you are interested to help but you cannot find the paper please email me at [email protected] and i will send you the paper. Thanks in advance

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• T-SQL Right Joins to ALL Entries inc Selected Column

  - by Pace

  Hi Experts, I have the following Query which produces the output below; SELECT TBLUSERS.USERID, TBLUSERS.ADusername, TBLACCESSLEVELS.ACCESSLEVELID, TBLACCESSLEVELS.AccessLevelName FROM TBLACCESSLEVELS INNER JOIN TBLACCESSRIGHTS ON TBLACCESSLEVELS.ACCESSLEVELID = TBLACCESSRIGHTS.ACCESSLEVELID INNER JOIN TBLUSERS ON TBLACCESSRIGHTS.USERID = TBLUSERS.USERID The output is this; 29 administrator 1 AllUsers 29 administrator 2 JobQueue 29 administrator 3 Telephone Directory Admin 29 administrator 4 Jobqueueadmin 29 administrator 5 UserAdmin 29 administrator 6 Product System 27 alan 1 AllUsers 97 andy 1 AllUsers 26 barry 1 AllUsers 26 barry 2 JobQueue 26 barry 3 Telephone Directory Admin 26 barry 4 Jobqueueadmin 26 barry 5 UserAdmin 26 barry 6 Product System 26 barry 7 Newseditor 26 barry 8 GreetingBoard What I would like to do is modify the query so I get all Access Levels regardless of weather there is an entry for that user. What I would also like to do is some sort of exist case so that I get output like the following; 29 administrator 1 AllUsers True 29 administrator 2 JobQueue True 29 administrator 3 Telephone Directory Admin True 29 administrator 4 Jobqueueadmin True 29 administrator 5 UserAdmin True 29 administrator 6 Product System True 29 administrator 7 Newseditor False 29 administrator 8 GreetingBoard False 27 alan 1 AllUsers True 27 alan 2 JobQueue False 27 alan 3 Telephone Directory Admin False 27 alan 4 Jobqueueadmin False 27 alan 5 UserAdmin False 27 alan 6 Product System False 27 alan 7 Newseditor False 27 alan 8 GreetingBoard False 97 andy 1 AllUsers True 97 andy 2 JobQueue False 97 andy 3 Telephone Directory Admin False 97 andy 4 Jobqueueadmin False 97 andy 5 UserAdmin False 97 andy 6 Product System False 97 andy 7 Newseditor False 97 andy 8 GreetingBoard False 26 Barry 1 AllUsers True 26 Barry 2 JobQueue True 26 Barry 3 Telephone Directory Admin True 26 Barry 4 Jobqueueadmin True 26 Barry 5 UserAdmin True 26 Barry 6 Product System True 26 Barry 7 Newseditor True 26 Barry 8 GreetingBoard True ......................................... So the rules are ALWAYS show ALL Entries for ACCESSLEVELS and where EXISTS in ACCESSRIGHTS produce a true / false to show this. I hope this makes sense and hopefully you dont need the table definitions as everything I need to work with is in the original Query. I just need a way of manipulating it slightly and getting the join in the right place. Thank you. Pace

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• Scheme homework Black jack help....

  - by octavio

  So I need to do a game of blackjack simulator, butt can't seem to figure out whats wrong with the shuffle it's suppose to take a card randomly from the pack the put it on top of the pack. The delete it from the rest. so : (ace)(2)(3)(4)(5)...(k) if random card is let say 5 (5)(ace)(2)(3)(4)(5)...(k) then it deletes the 2nd 5 (5)(ace)(2)(3)(4)(6)...(k) here is the code: (define deck '((A . C) (2 . C) (3 . C) (4 . C) (5 . C) (6 . C) (7 . C) (8 . C) (9 . C) (10 . C) (V . C) (Q . C) (K . C))) ;auxilliary function for shuffle let you randomly select a card. (define shuffAux (lambda (t) (define cardR (lambda (t) (list-ref t (random 13)))) (cardR t))) ;auxilliary function used to remove the card after the car to prevent you from removing the randomly selected from the car(begining of the deck). (define (removeDupC card deck) (delete card (cdr deck)) ) (define shuffle2ndtry (lambda (deck seed) (define do-shuffle (lambda (deck seed) (if (> seed 0)( (cons (shuffAux deck) deck) (removeDupC (car deck) deck) (- 1 seed)) (write deck) ) ) ) (do-shuffle deck seed))) (define (shuffle deck seed) (define cards (cons (shuffAux deck) deck)) (write cards) (case (> seed 0) [(#t) (removeDupC (car cards) (cdr cards)) (shuffle cards (- seed 1))] [(#f) (write cards)])) (define random (let ((seed 0) (a 3141592653) (c 2718281829) (m (expt 2 35))) (lambda (limit) (cond ((and (integer? limit)) (set! seed (modulo (+ (* seed a) c) m)) (quotient (* seed limit) m)) (else (/ (* limit (random 34359738368)) 34359738368)))))) ;function in which you can delete an element from the list. (define delete (lambda (item list) (cond ((equal? item (car list)) (cdr list)) (else (cons (car list) (delete item (cdr list))))))) (

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• How to separate ear classloader and system classloader in JBoss 6?

  - by dskiles

  I'm trying to upgrade from JBoss 4.2.1 to JBoss 6. In JBoss 4.2.1, we are manually deploying our application as an exploded war and everything works beautifully. I'm running into problems because the application that I am trying to deploy uses versions of 3rd party libraries that are older than the ones that JBoss 6 now includes by default. The result of this is that I'm getting classloader conflicts all over the place and the application won't even start. At present, I have tried using the JBoss Classloading Documentation as well as the scanty bits of documentation for jboss-classloading.xml and haven't had any success. Has anyone out there managed to do this successfully? If you have, how did you do it? I've included a stack trace below in case it offers any useful information. Caused by: java.lang.Error: Error visiting "/C:/jboss6/server/default/deploy/app.war/WEB-INF/lib/jaxb-xjc-2.1.12.jar/1.0/com/sun/codemodel/JConditional.class" at org.jboss.classloading.plugins.vfs.VFSResourceVisitor.visit(VFSResourceVisitor.java:268) [jboss-classloading-vfs.jar:2.2.0.Alpha9] at org.jboss.vfs.VirtualFile.visit(VirtualFile.java:407) [jboss-vfs.jar:3.0.0.CR5] at org.jboss.vfs.VirtualFile.visit(VirtualFile.java:409) [jboss-vfs.jar:3.0.0.CR5] at org.jboss.vfs.VirtualFile.visit(VirtualFile.java:409) [jboss-vfs.jar:3.0.0.CR5] at org.jboss.vfs.VirtualFile.visit(VirtualFile.java:409) [jboss-vfs.jar:3.0.0.CR5] at org.jboss.vfs.VirtualFile.visit(VirtualFile.java:409) [jboss-vfs.jar:3.0.0.CR5] at org.jboss.vfs.VirtualFile.visit(VirtualFile.java:395) [jboss-vfs.jar:3.0.0.CR5] at org.jboss.classloading.plugins.vfs.VFSResourceVisitor.visit(VFSResourceVisitor.java:102) [jboss-classloading-vfs.jar:2.2.0.Alpha9] at org.jboss.deployers.vfs.plugins.classloader.VFSDeploymentClassLoaderPolicyModule.visit(VFSDeploymentClassLoaderPolicyModule.java:181) [:2.2.0.Alpha8] at org.jboss.scanning.plugins.DeploymentUnitScanner.scan(DeploymentUnitScanner.java:111) [:1.0.0.Alpha7] at org.jboss.scanning.spi.helpers.UrlScanner.scan(UrlScanner.java:96) [:1.0.0.Alpha7] at org.jboss.scanning.deployers.ScanningDeployer.deploy(ScanningDeployer.java:90) [:1.0.0.Alpha7] at org.jboss.deployers.plugins.deployers.DeployerWrapper.deploy(DeployerWrapper.java:179) [:2.2.0.Alpha8] ... 41 more

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• How to upgrade the project build in visual studio 2005 to visual studio 2008?

  - by Shailesh Jaiswal

  I have one OPC ( OLE for Process control ) server project which is developed into visual studio 2005. I want to run it in visual studio 2008. The coding for the OPC server project is done in VC++. I want to connect my OPC client to this OPC server. When I was opened the OPC server project which was build into visual studio 2005 into visual studio 2008 first time it was asking for conversion wizard. I gone through that wizard & successfully finished that wizard. But when I build ( by right clicking on the project & choosing build solution ) it is giving lots of error near about 64 errors. Most of the errors are like - fetal error C1083:Can not open type library file:'msxml4.dll':No such file or directory, fetal error LINK1181:can not open input file 'rpcndr.lib' , error C2051:case expression not constant. only these 3 types of errors in am getting. All these 3 errors are repeated in Error list & becoming bunch of 64 errors. Please provide me the solution for the above issue. Can you provide me any suusgestion or link or any way through whcih I can resolve the above issue?

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• Spaces and backslashes in Visual Studio build events

  - by gencha

  I have an application that is supposed to aid my project in terms of pre- and post-build event handling. I'm using ndesk.options for command line argument parsing. Which gave me weird results when my project path contains spaces. I thought this was the fault of ndesk.options but I guess my own application is to blame. I call my application as a post-built event like so: build.exe --in="$(ProjectDir)" --out="c:\out\" A simple foreach over args[] displays the following: --in=c:\my project" --out=c:\out" What happened is that the last " in each parameter was treated as if it was escaped. Thus the trailing backslash was removed. And the whole thing is treated as a single argument. Now I thought I was being smart by simply escaping the first " as well, like so: build.exe --in=\"$(ProjectDir)" --out=\"c:\out\" In that case the resulting args[] look like this: --path="c:\my project" --out="c:\out" The trailing backslash in the parameters is still swallowed and the first parameter is now split up. Passing this args[] to ndesk.options will then yield wrong results. How should the right command line look so that the correct elements end up in the correct args[] slots? Alternatively, how is one supposed to parse command line arguments like these with or without ndesk.options? Any suggestion is welcome. Thanks in advance

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• WPF Background Thread Invocation

  - by jeffn825

  Maybe I'm mis-remembering how Winforms works or I'm overcomplicating the hell out of this, but here's my problem. I have a WPF client app application that talks to a server over WCF. The current user may "log out" of the WPF client, which closes all open screens, leaves only the navigation pane, and minimizes the program window. When the user re-maximizes the program window, they are prompted to log in. Simple. But sometimes things happen on background threads - like every 5 minutes the client tries to make a WCF calls that refreshes some cached data. And what if the user is logged out when this 5 minute timer triggers? Well, then the user should be prompted to log back in...and this must of course happen on the UI thread. private static ISecurityContext securityContext; public static ISecurityContext SecurityContext { get { if (securityContext == null) { // Login method shows a window and prompts the user to log in Application.Current.Dispatcher.Invoke((Action)Login); } return securityContext; } } So far so good, right? But what happens when multiple threads hit this spot of code? Well, my first intuition was that since I'm syncrhonizing across the Application.Current.Dispatcher, I should be fine, and whichever thread hit first would be responsible for showing the login form and getting the user logged in... Not the case... Thread 1 will hit the code and call ShowDialog on the login form Thread 2 will also hit the code and will call Login as soon as Thread 1 has called ShowDialog, since calling ShowDialog unblocked Thread 1 (I believe because of the way the WPF message pump works) All I want is a synchronized way of getting the user logged back into the application...what am I missing here? Thanks in advance.

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• Beginner question - Loop invariants (Specifically Ch.3 of "Accelerated C++")

  - by Owen

  Hi - as I said, a complete beginner question here. I'm currently working my way through "Accelerated C++" and just came across this in chapter 3: // invariant: // we have read count grades so far, and // sum is the sum of the first count grades while (cin >> x) { ++count; sum += x; } The authors follow this by explaining that the invariant needs special attention paid to it because when the input is read into the variable x, we will have read count+1 grades and thus the invariant will be untrue. Similarly, when we have incremented the counter, the variable sum will no longer be the sum of the last count grades (in case you hadn't guessed, it's the traditional program for calculating student marks). What I don't understand is why this matters. Surely for just about any other loop, a similar statement would be true? For example, here is the book's first while loop (the output is filled in later): // invariant: we have written r rows so far while (r != rows) { // write a row of output std::cout << std::endl; ++r; } Once we have written the appropriate row of output, surely the invariant is false until we have incremented r, just as in the other example? It's probably something really obvious, anyone could enlighten me as to what makes these two cases different, that'd be great - and thanks in advance for taking the time to answer such a complete novice question. Owen

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• Large number of simultaneous long-running operations in Qt

  - by Hostile Fork

  I have some long-running operations that number in the hundreds. At the moment they are each on their own thread. My main goal in using threads is not to speed these operations up. The more important thing in this case is that they appear to run simultaneously. I'm aware of cooperative multitasking and fibers. However, I'm trying to avoid anything that would require touching the code in the operations, e.g. peppering them with things like yieldToScheduler(). I also don't want to prescribe that these routines be stylized to be coded to emit queues of bite-sized task items...I want to treat them as black boxes. For the moment I can live with these downsides: Maximum # of threads tend to be O(1000) Cost per thread is O(1MB) To address the bad cache performance due to context-switches, I did have the idea of a timer which would juggle the priorities such that only idealThreadCount() threads were ever at Normal priority, with all the rest set to Idle. This would let me widen the timeslices, which would mean fewer context switches and still be okay for my purposes. Question #1: Is that a good idea at all? One certain downside is it won't work on Linux (docs say no QThread::setPriority() there). Question #2: Any other ideas or approaches? Is QtConcurrent thinking about this scenario? (Some related reading: how-many-threads-does-it-take-to-make-them-a-bad-choice, many-threads-or-as-few-threads-as-possible, maximum-number-of-threads-per-process-in-linux)

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• How Can I Prevent Memory Leaks in IE Mobile?

  - by Jake Howlett

  Hi All, I've written an application for use offline (with Google Gears) on devices using IE Mobile. The devices are experiencing memory leaks at such a rate that the device becomes unusable over time. The problem page fetches entries from the local Gears database and renders a table of each entry with a link in the last column of each row to open the entry ( the link is just onclick="open('myID')" ). When they've done with the entry they return to the table, which is RE-rendered. It's the repeated building of this table that appears to be the problem. Mainly the onclick events. The table is generated in essence like this: var tmp=""; for (var i=0; i<100; i++){ tmp+="<tr><td>row "+i+"</td><td><a href=\"#\" id=\"LINK-"+i+"\""+ " onclick=\"afunction();return false;\">link</a></td></tr>"; } document.getElementById('view').innerHTML = "<table>"+tmp+"</table>"; I've read up on common causes of memory leaks and tried setting the onclick event for each link to "null" before re-rendering the table but it still seems to leak. Anybody got any ideas? In case it matters, the function being called from each link looks like this: function afunction(){ document.getElementById('view').style.display="none"; } Would that constitute a circular reference in any way? Jake

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• UniqueConstraint in EmbeddedConfiguration

  - by LantisGaius

  I just started using db4o on C#, and I'm having trouble setting the UniqueConstraint on the DB.. here's the db4o configuration static IObjectContainer db = Db4oEmbedded.OpenFile(dbase.Configuration(), "data.db4o"); static IEmbeddedConfiguration Configuration() { IEmbeddedConfiguration dbConfig = Db4oEmbedded.NewConfiguration(); // Initialize Replication dbConfig.File.GenerateUUIDs = ConfigScope.Globally; dbConfig.File.GenerateVersionNumbers = ConfigScope.Globally; // Initialize Indexes dbConfig.Common.ObjectClass(typeof(DAObs.Environment)).ObjectField("Key").Indexed(true); dbConfig.Common.Add(new Db4objects.Db4o.Constraints.UniqueFieldValueConstraint(typeof(DAObs.Environment), "Key")); return dbConfig; } and the object to serialize: class Environment { public string Key { get; set; } public string Value { get; set; } } everytime I get to commiting some values, an "Object reference not set to an instance of an object." Exception pops up, with a stack trace pointing to the UniqueFieldValueConstraint. Also, when I comment out the two lines after the "Initialize Indexes" comment, everything runs fine (Except you can save non-unique keys, which is a problem)~ Commit code (In case I'm doing something wrong in this part too:) public static void Create(string key, string value) { try { db.Store(new DAObs.Environment() { Key = key, Value = value }); db.Commit(); } catch (Db4objects.Db4o.Events.EventException ex) { System.Console.WriteLine (DateTime.Now + " :: Environment.Create\n" + ex.InnerException.Message +"\n" + ex.InnerException.StackTrace); db.Rollback(); } } Help please? Thanks in advance~

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• Programmatically implementing an interface that combines some instances of the same interface in var

  - by namin

  What is the best way to implement an interface that combines some instances of the same interface in various specified ways? I need to do this for multiple interfaces and I want to minimize the boilerplate and still achieve good efficiency, because I need this for a critical production system. Here is a sketch of the problem. Abstractly, I have a generic combiner class which takes the instances and specify the various combinators: class Combiner<I> { I[] instances; <T> T combineSomeWay(InstanceMethod<I,T> method) { // ... method.call(instances[i]) ... combined in some way ... } // more combinators } Now, let's say I want to implement the following interface among many others: Interface Foo { String bar(int baz); } I want to end up with code like this: class FooCombiner implements Foo { Combiner<Foo> combiner; @Override public String bar(final int baz) { return combiner.combineSomeWay(new InstanceMethod<Foo, String> { @Override public call(Foo instance) { return instance.bar(baz); } }); } } Now, this can quickly get long and winded if the interfaces have lots of methods. I know I could use a dynamic proxy from the Java reflection API to implement such interfaces, but method access via reflection is hundred times slower. So what are the alternatives to boilerplate and reflection in this case?

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• Handling mach exceptions in 64bit OS X application

  - by Brad S

  I have been able to register my own mach port to capture mach exceptions in my applications and it works beautifully when I target 32 bit. However when I target 64 bit, my exception handler catch_exception_raise() gets called but the array of exception codes that is passed to the handler are 32 bits wide. This is expected in a 32 bit build but not in 64 bit. In the case where I catch EXC_BAD_ACCESS the first code is the error number and the second code should be the address of the fault. Since the second code is 32 bits wide the high 32 bits of the 64 bit fault address is truncated. I found a flag in <mach/exception_types.h> I can pass in task_set_exception_ports() called MACH_EXCEPTION_CODES which from looking at the Darwin sources appears to control the size of the codes passed to the handler. It looks like it is meant to be ored with the behavior passed in to task_set_exception_ports(). However when I do this and trigger an exception, my mach port gets notified, I call exc_server() but my handler never gets called, and when the reply message is sent back to the kernel I get the default exception behavior. I am targeting the 10.6 SDK. I really wish apple would document this stuff better. Any one have any ideas?

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• C++ Exceptions and Inheritance from std::exception

  - by fbrereto

  Given this sample code: #include <iostream> #include <stdexcept> class my_exception_t : std::exception { public: explicit my_exception_t() { } virtual const char* what() const throw() { return "Hello, world!"; } }; int main() { try { throw my_exception_t(); } catch (const std::exception& error) { std::cerr << "Exception: " << error.what() << std::endl; } catch (...) { std::cerr << "Exception: unknown" << std::endl; } return 0; } I get the following output: Exception: unknown Yet simply making the inheritance of my_exception_t from std::exception public, I get the following output: Exception: Hello, world! Could someone please explain to me why the type of inheritance matters in this case? Bonus points for a reference in the standard.

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