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  • g++ C++0x enum class Compiler Warnings

    - by Travis G
    I've been refactoring my horrible mess of C++ type-safe psuedo-enums to the new C++0x type-safe enums because they're way more readable. Anyway, I use them in exported classes, so I explicitly mark them to be exported: enum class __attribute__((visibility("default"))) MyEnum : unsigned int { One = 1, Two = 2 }; Compiling this with g++ yields the following warning: type attributes ignored after type is already defined This seems very strange, since, as far as I know, that warning is meant to prevent actual mistakes like: class __attribute__((visibility("default"))) MyClass { }; class __attribute__((visibility("hidden"))) MyClass; Of course, I'm clearly not doing that, since I have only marked the visibility attributes at the definition of the enum class and I'm not re-defining or declaring it anywhere else (I can duplicate this error with a single file). Ultimately, I can't make this bit of code actually cause a problem, save for the fact that, if I change a value and re-compile the consumer without re-compiling the shared library, the consumer passes the new values and the shared library has no idea what to do with them (although I wouldn't expect that to work in the first place). Am I being way too pedantic? Can this be safely ignored? I suspect so, but at the same time, having this error prevents me from compiling with Werror, which makes me uncomfortable. I would really like to see this problem go away.

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  • Is it possible to use Indy 10.5.8.0 with Delphi XE?

    - by jachguate
    The case I'm trying to update the INDY to the latest version for my Delphi XE (Update 1), so I downloaded the latest INDY10 file (Indy_4545.zip) from indy.fulgan.com/ZIP. The packages compiles successfully and I can now even see the new version 10.5.8.0 on the about box dialog, but after a IDE restart I got a message saying: No se encuentra el punto de entrada del procedimiento @Idhttp@TIdCustomHTTP@GetRequestHeaders$qqrv en la biblioteca de vínculos dinámicos IndyProtocols150.bpl. My free translation to English: Entry point not found for procedure @Idhttp@TIdCustomHTTP@GetRequestHeaders$qqrv not found on the dynamic link library IndyProtocols150.bpl. After a quick comparision of old and new IdHTTP.pas I found a lot of changes on the TIdCustomHttp class, including the rename of some methods GetResponseHeaders to GetResponse GetRequestHeaders to GetRequest SetRequestHeaders to SetRequest Along with changed public/published method firms in this and other and classes interfaces. After the update, I got a lot of packages failing to load, including dclcxPivotGridOLAPD15.bpl, which in turns depends on dclDataSnapServer150.bpl which encounters the missing method on the bpl. AFAIK I can't recompile the dclDataSnapServer150.bpl (and maybe other failing packages, I just stopped here). DataSnap and DevExpress support on the IDE is a must for my day to day so The questions Is there a safe pre-established path to update to the newest INDY for Delphi XE? If not, am I on the safe side by just parching the source code by creating the old public methods and call the new ones on the implementation part? am I missing something else or am I really stuck with INDY 10.5.7 until the next Delphi minor/major release?

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  • perl multiple tasks problem

    - by Alice Wozownik
    I have finished my earlier multithreaded program that uses perl threads and it works on my system. The problem is that on some systems that it needs to run on, thread support is not compiled into perl and I cannot install additional packages. I therefore need to use something other than threads, and I am moving my code to using fork(). This works on my windows system in starting the subtasks. A few problems: How to determine when the child process exits? I created new threads when the thread count was below a certain value, I need to keep track of how many threads are running. For processes, how do I know when one exits so I can keep track of how many exist at the time, incrementing a counter when one is created and decrementing when one exits? Is file I/O using handles obtained with OPEN when opened by the parent process safe in the child process? I need to append to a file for each of the child processes, is this safe on unix as well. Is there any alternative to fork and threads? I tried use Parallel::ForkManager, but that isn't installed on my system (use Parallel::ForkManager; gave an error) and I absolutely require that my perl script work on all unix/windows systems without installing any additional modules.

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  • How to make Stack.Pop threadsafe

    - by user260197
    I am using the BlockingQueue code posted in this question, but realized I needed to use a Stack instead of a Queue given how my program runs. I converted it to use a Stack and renamed the class as needed. For performance I removed locking in Push, since my producer code is single threaded. My problem is how can thread working on the (now) thread safe Stack know when it is empty. Even if I add another thread safe wrapper around Count that locks on the underlying collection like Push and Pop do, I still run into the race condition that access Count and then Pop are not atomic. Possible solutions as I see them (which is preferred and am I missing any that would work better?): Consumer threads catch the InvalidOperationException thrown by Pop(). Pop() return a nullptr when _stack-Count == 0, however C++-CLI does not have the default() operator ala C#. Pop() returns a boolean and uses an output parameter to return the popped element. Here is the code I am using right now: generic <typename T> public ref class ThreadSafeStack { public: ThreadSafeStack() { _stack = gcnew Collections::Generic::Stack<T>(); } public: void Push(T element) { _stack->Push(element); } T Pop(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Pop(); } finally { System::Threading::Monitor::Exit(_stack); } } public: property int Count { int get(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Count; } finally { System::Threading::Monitor::Exit(_stack); } } } private: Collections::Generic::Stack<T> ^_stack; };

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  • Asynchronous daemon processing / ORM interaction with Django

    - by perrierism
    I'm looking for a way to do asynchronous data processing with a daemon that uses Django ORM. However, the ORM isn't thread-safe; it's not thread-safe to try to retrieve / modify django objects from within threads. So I'm wondering what the correct way to achieve asynchrony is? Basically what I need to accomplish is taking a list of users in the db, querying a third party api and then making updates to user-profile rows for those users. As a daemon or background process. Doing this in series per user is easy, but it takes too long to be at all scalable. If the daemon is retrieving and updating the users through the ORM, how do I achieve processing 10-20 users at a time? I would use a standard threading / queue system for this but you can't thread interactions like models.User.objects.get(id=foo) ... Django itself is an asynchronous processing system which makes asynchronous ORM calls(?) for each request, so there should be a way to do it? I haven't found anything in the documentation so far. Cheers

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  • Accessing class member variables inside a BackgroundWorker's DoWork event handler, and other Backgro

    - by Justin
    Question 1 In the DoWork event handler of a BackgroundWorker, is it safe to access (for both reading and writing) member variables of the class that contains the BackgroundWorker? Is it safe to access other variables that are not declared inside the DoWork event handler itself? Obviously DoWork should not be accessing any UI objects of, say, a WinForms application, as the UI should only be updated from the UI thread. But what about accessing other (not UI-related) member variables? The reason why I ask is that I've seen the occasional comment come up while Googling saying that accessing member variables is not allowed. The only example I can find at the moment is a comment on this MSDN page, which says: Note, that the BGW can cause exceptions if it attempts to access or modify class level variables. All data must be passed to it by delegates and events. And also: NEVER. NEVER. Never try to reference variables not declared inside of DoWork. It may seem to work at times, but in reality you are just getting lucky. As far as I know, MSDN itself does not document any restrictions of this kind (although if I'm wrong, I'd appreciate a link). But comments like these do seem to pop up every now and again. (Of course if DoWork does access/modify a member variable that could be accessed/modified by the main thread at the same time, it is necessary to synchronise access to that field, eg by using a locking object. But the above quotes seem to require a blanket ban of accessing member variables, rather than just synchronising access!) Question 2 To make this into a more general question, are there any other (not documented?) restrictions that users of the BackgroundWorker should be aware of, aside from the above? Any "best practices", perhaps?

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  • Emulating a web browser

    - by Sean
    Hello, we are tasked with basically emulating a browser to fetch webpages, looking to automate tests on different web pages. This will be used for (ideally) console-ish applications that run in the background and generate reports. We tried going with .NET and the WatiN library, but it was built on a Marshalled IE, and so it lacked many features that we hacked in with calls to unmanaged native code, but at the end of the day IE is not thread safe nor process safe, and many of the needed features could only be implemented by changing registry values and it was just terribly unflexible. Proxy support JavaScript support- we have to be able to parse the actual DOM after any javascript has executed (and hopefully an event is raised to handle any ajax calls) Ability to save entire contents of page including images FROM THE loaded page's CACHE to a separate location ability to clear cookies/cache, get the cookies/cache, etc. Ability to set headers and alter post data for any browser call And for the love of drogs, an API that isn't completely cryptic Languages acceptable C++, C#, Python, anything that can be a simple little console application that doesn't have a retarded syntax like Ruby. From my own research, and believe me I am terrible at google searches, I have heard good things about WebKit... would the Qt module QtWebKit handle all these features?

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  • Reference-type conversion operators: asking for trouble?

    - by Ben
    When I compile the following code using g++ class A {}; void foo(A&) {} int main() { foo(A()); return 0; } I get the following error messages: > g++ test.cpp -o test test.cpp: In function ‘int main()’: test.cpp:10: error: invalid initialization of non-const reference of type ‘A&’ from a temporary of type ‘A’ test.cpp:6: error: in passing argument 1 of ‘void foo(A&)’ After some reflection, these errors make plenty of sense to me. A() is just a temporary value, not an assignable location on the stack, so it wouldn't seem to have an address. If it doesn't have an address, then I can't hold a reference to it. Okay, fine. But wait! If I add the following conversion operator to the class A class A { public: operator A&() { return *this; } }; then all is well! My question is whether this even remotely safe. What exactly does this point to when A() is constructed as a temporary value? I am given some confidence by the fact that void foo(const A&) {} can accept temporary values according to g++ and all other compilers I've used. The const keyword can always be cast away, so it would surprise me if there were any actual semantic differences between a const A& parameter and an A& parameter. So I guess that's another way of asking my question: why is a const reference to a temporary value considered safe by the compiler whereas a non-const reference is not?

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  • Java: dangerous self-returning-recursive function by IOException?

    - by HH
    I had very errorsome Exception handling with if-clauses. An exception occurs if not found path. An exception returns the function again. The function is recursive. Safe? $ javac SubDirs.java $ java SubDirs Give me an path. . HELLO com TOASHEOU google common annotations base collect internal Give me an path. IT WON'T FIND ME, SO IT RETURNS ITSELF due to Exception caught Give me an path. $ cat SubDirs.java import java.io.*; import java.util.*; public class SubDirs { private List<File> getSubdirs(File file) throws IOException { List<File> subdirs = Arrays.asList(file.listFiles(new FileFilter() { public boolean accept(File f) { return f.isDirectory(); } })); subdirs = new ArrayList<File>(subdirs); List<File> deepSubdirs = new ArrayList<File>(); for(File subdir : subdirs) { deepSubdirs.addAll(getSubdirs(subdir)); } subdirs.addAll(deepSubdirs); return subdirs; } public static void search() { try{ BufferedReader in = new BufferedReader(new InputStreamReader(System.in)); String s; System.out.println("Give me an path."); while ((s = in.readLine()) != null && s.length() != 0){ SubDirs dirs = new SubDirs(); List<File> subDirs = dirs.getSubdirs(new File(s)); for ( File f : subDirs ) { System.out.println(f.getName()); } System.out.println("Give me an path."); } }catch(Exception e){ // Simple but is it safe? search(); } } public static void main(String[] args) throws IOException { search(); } }

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  • Socket Read In Multi-Threaded Application Returns Zero Bytes or EINTR (104)

    - by user309670
    Hi. Am a c-coder for a while now - neither a newbie nor an expert. Now, I have a certain daemoned application in C on a PPC Linux. I use PHP's socket_connect as a client to connect to this service locally. The server uses epoll for multiplexing connections via a Unix socket. A user submitted string is parsed for certain characters/words using strstr() and if found, spawns 4 joinable threads to different websites simultaneously. I use socket, connect, write and read, to interact with the said webservers via TCP on their port 80 in each thread. All connections and writes seems successful. Reads to the webserver sockets fail however, with either (A) all 3 threads seem to hang, and only one thread returns -1 and errno is set to 104. The responding thread takes like 10 minutes - an eternity long:-(. *I read somewhere that the 104 (is EINTR?), which in the network context suggests that ...'the connection was reset by peer'; or (B) 0 bytes from 3 threads, and only 1 of the 4 threads actually returns some data. Isn't the socket read/write thread-safe? I use thread-safe (and reentrant) libc functions such as strtok_r, gethostbyname_r, etc. *I doubt that the said webhosts are actually resetting the connection, because when I run a single-threaded standalone (everything else equal) all things works perfectly right, but of course in series not parallel. There's a second problem too (oops), I can't write back to the client who connect to my epoll-ed Unix socket. My daemon application will hang and hog CPU 100% for ever. Yet nothing is written to the clients end. Am sure the client (a very typical PHP socket application) hasn't closed the connection whenever this is happening - no error(s) detected either. Any ideas? I cannot figure-out whatever is wrong even with Valgrind, GDB or much logging. Kindly help where you can.

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  • PHP $_SERVER['HTTP_HOST'] vs. $_SERVER['SERVER_NAME'], am I understanding the man pages correctly?

    - by Jeff
    I did a lot of searching and also read the PHP $_SERVER man page. Do I have this right regarding which to use for my PHP scripts for simple link definitions used throughout my site? $_SERVER['SERVER_NAME'] is based on your web servers' config file (Apache2 in my case), and varies depending on a few directives: (1) VirtualHost, (2) ServerName, (3) UseCanonicalName, etc. $_SERVER['HTTP_HOST'] is based on the request from the client. Therefore, it would seem to me that the proper one to use in order to make my scripts as compatible as possible would be $_SERVER['HTTP_HOST']. Is this assumption correct? Followup comments: I guess I got a little paranoid after reading this article and noting that someone said "they wouldn't trust any of the $_SERVER vars": http://markjaquith.wordpress.com/2009/09/21/php-server-vars-not-safe-in-forms-or-links/ and also: http://www.php.net/manual/en/reserved.variables.server.php (comment: Vladimir Kornea 14-Mar-2009 01:06) Apparently the discussion is mainly about $_SERVER['PHP_SELF'] and why you shouldn't use it in the form action attribute without proper escaping to prevent XSS attacks. My conclusion about my original question above is that it is "safe" to use $_SERVER['HTTP_HOST'] for all links on a site without having to worry about XSS attacks, even when used in forms. Please correct me if I'm wrong.

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  • Can I configure the ResetPassword in Asp.Net's MembershipProvider?

    - by coloradotechie
    I have an C# asp.net app using the default Sql MembershipProvider. My web.config has a few settings that control how I'm using this Provider: enablePasswordRetrieval="false" enablePasswordReset="true" requiresUniqueEmail="true" passwordFormat="Hashed" minRequiredPasswordLength="5" The problem I'm running into is that when people reset their passwords, it seems the ResetPassword() method returns a password that is longer than I want and has characters that can be confusing (l,1,i,I,0,O). Furthermore, I'm sending my users an email with a plain-text message and an HTML message (I'm using MailMessage with AlternateViews). If the password has unsafe HTML characters in it, when the email clients render the HTML text the password might be different (e.g. the %, &, and < aren't exactly HTML safe). I've looked over the "add" element that belongs in the web.config, but I don't see any extra configuration properties to only include certain characters in the ResetPassword() method and to limit the password length. Can I configure the ResetPassword() method to limit the password length and limit the character set it is choosing from? Right now I have a workaround: I call ResetPassword() to make sure the supplied answer is correct, and then I use a RandomPassword generator I downloaded off the internet to generate a password that I like (without ambiguous characters, HTML safe, and only 8 characters long) and then I call ChangePassword() to change the user's password after I've already reset it. My workaround seems kludgy and I thought it would be better to configure ResetPassword() to do what I want. Thank you~! ColoradoTechie

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  • what exactly is the danger of an uninitialized pointer in C

    - by akh2103
    I am trying get a handle on C as I work my way thru Jim Trevor's "Cyclone: A safe dialect of C" for a PL class. Trevor and his co-authors are trying to make a safe version of C, so they eliminate uninitialized pointers in their language. Googling around a bit on uninitialized pointers, it seems like un-initialized pointers point to random locations in memory. It seems like this alone makes them unsafe. If you reference an un-itilialized pointer, you jump to an unsafe part of memory. Period. But the way Trevor talks about them seems to imply that it is more complex. He cites the following code, and explains that when the function FrmGetObjectIndex dereferences f, it isn’t accessing a valid pointer, but rather an unpredictable address — whatever was on the stack when the space for f was allocated. What does Trevor mean by "whatever was on the stack when the space for f was allocated"? Are "un-initialized" pointers initialized to random locations in memory by default? Or does their "random" behavior have to do with the memory allocated for these pointers getting filled with strange values (that are then referenced) because of unexpected behavior on the stack. Form *f; switch (event->eType) { case frmOpenEvent: f = FrmGetActiveForm(); ... case ctlSelectEvent: i = FrmGetObjectIndex(f, field); ... }

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  • How do I add IIS Virtual Directories and arbitrary files in TFS Solution

    - by chriscena
    We have a web portal product from which we customize portals from customers. We use the precompiled web app and create a virtual directory (vd) where the customization resides. In addition to this we do some changes web.config in the web app folder. We would obviously like to keep these customizations under TFS source control. When I try to add the precompiled web app (which I don't want to add to source control), a warning tells me that the vds cannot be added. If I only add the folder that is referenced to by the vd, I lose the references to assemblies in the precompiled web app. My questions are: How do I structure a solution for adding IIS (sub application level) virtual directories and still retain the references to assemblies? Is it possible to add other directories/files from the web application level (like App_Theme, web.config etc.) to the solution? Since we already use Visual Source Safe, we have established a tree structure for each customization project: Project Root | |-Custom Sql | |-Custom Portal Files (which is added as a virtual directory) | |-Other Customizations I could probably do a lot of this manually through the source control explorer, but I'd like to have everything done through a solution. I've followed the instructions using this article: http://msdn.microsoft.com/en-us/library/bb668986.aspx, but this doesn't address the exact problem that I have. Oh, and we are currently using Visual Source Safe for portal customizaton, but are eager to make the move to TFS. TIA

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  • Anonymous union definition/declaration in a macro GNU vs VS2008

    - by Alan_m
    I am attempting to alter an IAR specific header file for a lpc2138 so it can compile with Visual Studio 2008 (to enable compatible unit testing). My problem involves converting register definitions to be hardware independent (not at a memory address) The "IAR-safe macro" is: #define __IO_REG32_BIT(NAME, ADDRESS, ATTRIBUTE, BIT_STRUCT) \ volatile __no_init ATTRIBUTE union \ { \ unsigned long NAME; \ BIT_STRUCT NAME ## _bit; \ } @ ADDRESS //declaration //(where __gpio0_bits is a structure that names //each of the 32 bits as P0_0, P0_1, etc) __IO_REG32_BIT(IO0PIN,0xE0028000,__READ_WRITE,__gpio0_bits); //usage IO0PIN = 0x0xAA55AA55; IO0PIN_bit.P0_5 = 0; This is my comparable "hardware independent" code: #define __IO_REG32_BIT(NAME, BIT_STRUCT)\ volatile union \ { \ unsigned long NAME; \ BIT_STRUCT NAME##_bit; \ } NAME; //declaration __IO_REG32_BIT(IO0PIN,__gpio0_bits); //usage IO0PIN.IO0PIN = 0xAA55AA55; IO0PIN.IO0PIN_bit.P0_5 = 1; This compiles and works but quite obviously my "hardware independent" usage does not match the "IAR-safe" usage. How do I alter my macro so I can use IO0PIN the same way I do in IAR? I feel this is a simple anonymous union matter but multiple attempts and variants have proven unsuccessful. Maybe the IAR GNU compiler supports anonymous unions and vs2008 does not. Thank you.

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  • MSTest unit test passes by itself, fails when other tests are run

    - by Sarah Vessels
    I'm having trouble with some MSTest unit tests that pass when I run them individually but fail when I run the entire unit test class. The tests test some code that SLaks helped me with earlier, and he warned me what I was doing wasn't thread-safe. However, now my code is more complicated and I don't know how to go about making it thread-safe. Here's what I have: public static class DLLConfig { private static string _domain; public static string Domain { get { return _domain = AlwaysReadFromFile ? readCredentialFromFile(DOMAIN_TAG) : _domain ?? readCredentialFromFile(DOMAIN_TAG); } } } And my test is simple: string expected = "the value I know exists in the file"; string actual = DLLConfig.Domain; Assert.AreEqual(expected, actual); When I run this test by itself, it passes. When I run it alongside all the other tests in the test class (which perform similar checks on different properties), actual is null and the test fails. I note this is not a problem with a property whose type is a custom Enum type; maybe I'm having this problem with the Domain property because it is a string? Or maybe it's a multi-threaded issue with how MSTest works?

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  • VB.net httpwebrequest For loop hangs every 10 or so iterations

    - by user574632
    Hello, I am trying to loop through an array and perform an httpwebrequest in each iteration. The code seems to work, however it pauses for a while (eg alot longer than the set timeout. Tried setting that to 100 to check and it still pauses) after every 10 or so iterations, then carries on working. Here is what i have so far: For i As Integer = 0 To numberOfProxies - 1 Try 'create request to a proxyJudge php page using proxy Dim request As HttpWebRequest = HttpWebRequest.Create("http://www.pr0.net/deny/azenv.php") request.Proxy = New Net.WebProxy(proxies(i)) 'select the current proxie from the proxies array request.Timeout = 10000 'set timeout Dim response As HttpWebResponse = request.GetResponse() Dim sr As StreamReader = New StreamReader(response.GetResponseStream()) Dim pageSourceCode As String = sr.ReadToEnd() 'check the downloaded source for certain phrases, each identifies a type of proxy 'HTTP_X_FORWARDED_FOR identifies a transparent proxy If pageSourceCode.Contains("HTTP_X_FORWARDED_FOR") Then 'delegate method for cross thread safe UpdateListbox(ListBox3, proxies(i)) ElseIf pageSourceCode.Contains("HTTP_VIA") Then UpdateListbox(ListBox2, proxies(i)) Else UpdateListbox(ListBox1, proxies(i)) End If Catch ex As Exception 'MessageBox.Show(ex.ToString) used in testing UpdateListbox(ListBox4, proxies(i)) End Try completedProxyCheck += 1 lblTotalProxiesChecked.CustomInvoke(Sub(l) l.Text = completedProxyCheck) Next I have searched all over this site and via google, and most responses to this type of question say the response must be closed. I have tried a using block, eg: Using response As HttpWebResponse = request.GetResponse() Using sr As StreamReader = New StreamReader(response.GetResponseStream()) Dim pageSourceCode As String = sr.ReadToEnd() 'check the downloaded source for certain phrases, each identifies a type of proxy 'HTTP_X_FORWARDED_FOR identifies a transparent proxy If pageSourceCode.Contains("HTTP_X_FORWARDED_FOR") Then 'delegate method for cross thread safe UpdateListbox(ListBox3, proxies(i)) ElseIf pageSourceCode.Contains("HTTP_VIA") Then UpdateListbox(ListBox2, proxies(i)) Else UpdateListbox(ListBox1, proxies(i)) End If End Using End Using And it makes no difference (though i may have implemented it wrong) As you can tell im very new to VB or any OOP so its probably a simple problem but i cant work it out. Any suggestions or just tips on how to diagnose these types of problems would be really appreciated.

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  • BackgroundWorker and instance variables

    - by Alastair Pitts
    One thing that's always confused me is how a BackgroundWorker seems to have thread-safe access to the instance variables of the surrounding class. Given a basic class: public class BackgroundProcessor { public List<int> Items { get; private set; } public BackgroundProcessor(IEnumerable<int> items) { Items = new List<int>(items); } public void DoWork() { BackgroundWorker worker = new BackgroundWorker(); worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted); worker.DoWork += new DoWorkEventHandler(worker_DoWork); worker.RunWorkerAsync(); } void worker_DoWork(object sender, DoWorkEventArgs e) { var processor = new ProcessingClass(); processor.Process(this.Points); //Accessing the instance variable } void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { //Stuff goes here } } Am I erroneous in my assumption the the call to processor.Process(this.Points); is a thread-safe call? How don't I get a cross-thread access violation? I'm sure it's obvious, but it always has confused me.

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  • Change classes instantiated with loadNibNamed

    - by Nick H247
    I am trying to change the class of objects created with a nib with the iPhone SDK. The reason for this is; i dont know until runtime what the class is that i want the nib object to be (though they will have the same UIView based super class), and i dont want to create a different nib for every eventuality - as the .nib will be the same for each, apart from the class of one object. I have been successful, with a couple of methods, but either have some knock on effects or am unsure of how safe the methods I have used are: Method 1: Override alloc, on the super class and set a c variable to the class I require: + (id) alloc { if (theClassIWant) { id object = [theClassIWant allocWithZone:NSDefaultMallocZone()]; theClassIWant = nil; return object; } return [BaseClass allocWithZone:NSDefaultMallocZone()]; } this works well, and i assume is 'reasonably' safe, though if I alloc a subclass myself (without setting 'theClassIWant') - an object of the base class is created. I also dont really like the idea of overriding alloc... Method 2: use object_setClass(self,theClassIWant) in initWithCoder (before calling initWithCoder on the super class): - (id) initWithCoder:(NSCoder *)aDecoder { if (theClassIWant) { // the framework doesn't like this: //[self release]; //self = [theClassIWant alloc]; // whoa now! object_setClass(self,theClassIWant); theClassIWant = nil; return [self initWithCoder:aDecoder]; } if (self = [super initWithCoder:aDecoder]) { ... this also works well, but not all the subclasses are necessarily going to be the same size as the super class, so this could be very unsafe! To combat this i tried releasing and re-allocing to the correct type within initWithCoder, but i got the following error from the framework: "This coder requires that replaced objects be returned from initWithCoder:" dont quite get what this means! i am replacing an object in initWithCoder... Any comments on the validity of these methods, or suggestions of improvements or alternatives welcome!

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  • Can threads safely read variables set by VCL events?

    - by Tom1952
    Is it safe for a thread to READ a variable set by a Delphi VCL event? When a user clicks on a VCL TCheckbox, the main thread sets a boolean to the checkbox's Checked state. CheckboxState := CheckBox1.Checked; At any time, a thread reads that variable if CheckBoxState then ... It doesn't matter if the thread "misses" a change to the boolean, because the thread checks the variable in a loop as it does other things. So it will see the state change eventually... Is this safe? Or do I need special code? Is surrounding the read and write of the variable (in the thread and main thread respectively) with critical code calls necessary and sufficient? As I said, it doesn't matter if the thread gets the "wrong" value, but I keep thinking that there might be a low-level problem if one thread tries to read a variable while the main thread is in the middle of writing it, or vice versa. My question is similar to this one: http://stackoverflow.com/questions/1353096/cross-thread-reading-of-a-variable. (Also related to my previous question: http://stackoverflow.com/questions/2449183/using-entercriticalsection-in-thread-to-update-vcl-label)

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  • How to Send Headers Through PHP Proxy?

    - by blabus
    Okay, so I have an issue with an AJAX request. I currently have this URL: http://www.google.com/images?hl=en&safe=off&gbv=2&tbs=isch%3A1&sa=1&q=cars+imagesize%3A500x500&aq=f&aqi=&aql=&oq=&gs_rfai=&start=0 I then pass it to my proxy script by modifying the string to this: proxy.php?url=http://www.google.com/images?hl=en&safe=off&gbv=2&tbs=isch%3A1&sa=1&q=cars+imagesize%3A500x500&aq=f&aqi=&aql=&oq=&gs_rfai=&start=0 I need to use the PHP proxy script to grab that page's HTML so that I can then parse through it with javascript. However, the problem is that the headers in that URL are also being sent to the proxy script, and as a result, I get a 'malformed or illegal request' error. I'm pretty sure the two different sets of headers are the problem, because if I just replace the original URL string with 'http://wwww.google.com', the proxy returns the HTML of the page correctly. So basically, I don't know how to fix this. I'm a complete PHP noob, and I tried escaping the original URL before I appended it to the 'proxy.php?url=', but that doesn't fix anything. Any ideas? Thanks!

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  • MS hotfix delayed delivery.

    - by MOE37x3
    I just requested a hotfix from support.microsoft.com and put in my email address, but I haven't received the email yet. The splash page I got after I requested the hotfix said: Hotfix Confirmation We will send these hotfixes to the following e-mail address: (my correct email address) Usually, our hotfix e-mail is delivered to you within five minutes. However, sometimes unforeseen issues in e-mail delivery systems may cause delays. We will send the e-mail from the “[email protected]” e-mail account. If you use an e-mail filter or a SPAM blocker, we recommend that you add “[email protected]” or the “microsoft.com” domain to your safe senders list. (The safe senders list is also known as a whitelist or an approved senders list.) This will help prevent our e-mail from going into your junk e-mail folder or being automatically deleted. I'm sure that the email is not getting caught in a spam catcher. How long does it normally take to get one of these hotfixes? Am I waiting for some human to approve it, or something? Should I just give up and try to get the file I need some other way? (Update: Replaced "[email protected]" with "(my correct email address)" to resolve Martín Marconcini's ambiguity.)

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  • Achieving Thread-Safety

    - by Smasher
    Question How can I make sure my application is thread-safe? Are their any common practices, testing methods, things to avoid, things to look for? Background I'm currently developing a server application that performs a number of background tasks in different threads and communicates with clients using Indy (using another bunch of automatically generated threads for the communication). Since the application should be highly availabe, a program crash is a very bad thing and I want to make sure that the application is thread-safe. No matter what, from time to time I discover a piece of code that throws an exception that never occured before and in most cases I realize that it is some kind of synchronization bug, where I forgot to synchronize my objects properly. Hence my question concerning best practices, testing of thread-safety and things like that. mghie: Thanks for the answer! I should perhaps be a little bit more precise. Just to be clear, I know about the principles of multithreading, I use synchronization (monitors) throughout my program and I know how to differentiate threading problems from other implementation problems. But nevertheless, I keep forgetting to add proper synchronization from time to time. Just to give an example, I used the RTL sort function in my code. Looked something like FKeyList.Sort (CompareKeysFunc); Turns out, that I had to synchronize FKeyList while sorting. It just don't came to my mind when initially writing that simple line of code. It's these thins I wanna talk about. What are the places where one easily forgets to add synchronization code? How do YOU make sure that you added sync code in all important places?

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  • How to benchmark on multi-core processors

    - by Pascal Cuoq
    I am looking for ways to perform micro-benchmarks on multi-core processors. Context: At about the same time desktop processors introduced out-of-order execution that made performance hard to predict, they, perhaps not coincidentally, also introduced special instructions to get very precise timings. Example of these instructions are rdtsc on x86 and rftb on PowerPC. These instructions gave timings that were more precise than could ever be allowed by a system call, allowed programmers to micro-benchmark their hearts out, for better or for worse. On a yet more modern processor with several cores, some of which sleep some of the time, the counters are not synchronized between cores. We are told that rdtsc is no longer safe to use for benchmarking, but I must have been dozing off when we were explained the alternative solutions. Question: Some systems may save and restore the performance counter and provide an API call to read the proper sum. If you know what this call is for any operating system, please let us know in an answer. Some systems may allow to turn off cores, leaving only one running. I know Mac OS X Leopard does when the right Preference Pane is installed from the Developers Tools. Do you think that this make rdtsc safe to use again? More context: Please assume I know what I am doing when trying to do a micro-benchmark. If you are of the opinion that if an optimization's gains cannot be measured by timing the whole application, it's not worth optimizing, I agree with you, but I cannot time the whole application until the alternative data structure is finished, which will take a long time. In fact, if the micro-benchmark were not promising, I could decide to give up on the implementation now; I need figures to provide in a publication whose deadline I have no control over.

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  • Thread-safty of boost RNG

    - by Maciej Piechotka
    I have a loop which should be nicely pararellized by insering one openmp pragma: boost::normal_distribution<double> ddist(0, pow(retention, i - 1)); boost::variate_generator<gen &, BOOST_TYPEOF(ddist)> dgen(rng, ddist); // Diamond const std::uint_fast32_t dno = 1 << i - 1; // #pragma omp parallel for for (std::uint_fast32_t x = 0; x < dno; x++) for (std::uint_fast32_t y = 0; y < dno; y++) { const std::uint_fast32_t diff = size/dno; const std::uint_fast32_t x1 = x*diff, x2 = (x + 1)*diff; const std::uint_fast32_t y1 = y*diff, y2 = (y + 1)*diff; double avg = (arr[x1][y1] + arr[x1][y2] + arr[x2][y1] + arr[x2][y2])/4; arr[(x1 + x2)/2][(y1 + y2)/2] = avg + dgen(); } (unless I make an error each execution does not depend on others at all. Sorry that not all of code is inserted). However my question is - are boost RNG thread-safe? They seems to refer to gcc code for gcc so even if gcc code is thread-safe it may not be the case for other platforms.

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