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• Detecting a stale Mutex

  - by sum1stolemyname

  Is there any technique or tool available to detect this kind of a deadlock during runtime? picture this in a worker thread (one of several, normally 4-6) try WaitForSingleObject(myMutex); DoSTuffThatMightCauseAnException; Except ReleaseMutex(myMutex); end; or more generally is there a design-pattern to avoid these kind of bugs? I coded the above code in the little hous after a longer hacking run

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• WCF threading - non-responsive UI

  - by Sphynx

  Hi everyone. I'm trying to configure some WCF stuff. Currently, I have a server which allows remote users to download files, and client. In the server, I use a ServiceHost class. I assume it should be running on a separate thread, however, the server UI (WinForms) becomes locked when someone downloads a file. Is there a way to manage the WCF threading model? Thank you!

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• Constructor invokation returned null: what to do?

  - by strager

  I have code which looks like: private static DirectiveNode CreateInstance(Type nodeType, DirectiveInfo info) { var ctor = nodeType.GetConstructor(new[] { typeof(DirectiveInfo) }); if(ctor == null) { throw new MissingMethodException(nodeType.FullName, "ctor"); } var node = ctor.Invoke(new[] { info }) as DirectiveNode; if(node == null) { // ???; } return node; } I am looking for what to do (e.g. what type of exception to throw) when the Invoke method returns something which isn't a DirectiveNode or when it returns null (indicated by // ??? above). (By the method's contract, nodeType will always describe a subclass of DirectiveNode.) I am not sure when calling a constructor would return null, so I am not sure if I should handle anything at all, but I still want to be on the safe side and throw an exception if something goes wrong.

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• How to create base build and two simultaneously child builds?

  - by thoughts

  Using visual source safe, How to create a base build and on top of that two inherited new child builds of c# project. Base Build - Base Project - Base source version. [Should be able to modify source file and it reflacts in child builds] Child Build - First Project Child Build - Second Project I can able to modify individual source code of both child builds and also base build. If i change base build any source file then it should reflact to child build also. Is this possible with VSS? if yes how can i achieve it If any other source control provide this kind of facility then let me know.

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• Correct way to safely store token/secret/etc from OAuth?

  - by viatropos

  I just started looking into OAuth and it looks really nice. I have oauth with twitter working in ruby right now. Now I'm wondering, what is the recommended safe way to store the responses in my local database and session? What should I store? Where should I store it? This example twitter-oauth-with-rails app stores a user.id in the session, and the user table has the token and secret. But that seems like it'd be really easy to hack and get the secret by just passing in a slew of test user ids, no?

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• What is Erlang's concurrency model actually ?

  - by arun_suresh

  I was reading a paper recently Why Events are Bad. The paper is a comparative study of Event based and thread based highly concurrent servers and finally concludes stating that Threads are better than events in that scenario. I find that I am not able to classify what sort of concurrency model erlang exposes. Erlang provides Light Weight Processes, but those processes are suspended most of the time until it has received some event/message of some sort. /Arun

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• How to change the order of toolbar buttons in Internet Explorer?

  - by Rick

  I know I can simply write to the CommandBandLayout regkey but since I don't know what format it is I'm having doubts if that is safe. Also, this answer suggest it's the wrong solution: http://stackoverflow.com/questions/1239266/how-to-modify-commandbandlayout-reg-key-value But how can I change the order a bit? I have written an Internet Explorer Add-on and I've registered it by putting it in HKCU but by default it falls off the screen so users are having trouble finding it. I would like to make the bar wider or move the button back in the screen.

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• options.fetch . I don't get it

  - by dorelal

  Look at the discussion on this thread . I am not able to follow how having a block to a fetch is a better solution.

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• compile time if && return string reference optimization

  - by Truncheon

  Hi. I'm writing a series classes that inherit from a base class using virtual. They are INT, FLOAT and STRING objects that I want to use in a scripting language. I'm trying to implement weak typing, but I don't want STRING objects to return copies of themselves when used in the following way (instead I would prefer to have a reference returned which can be used in copying): a = "hello "; b = "world"; c = a + b; I have written the following code as a mock example: #include <iostream> #include <string> #include <cstdio> #include <cstdlib> std::string dummy("<int object cannot return string reference>"); struct BaseImpl { virtual bool is_string() = 0; virtual int get_int() = 0; virtual std::string get_string_copy() = 0; virtual std::string const& get_string_ref() = 0; }; struct INT : BaseImpl { int value; INT(int i = 0) : value(i) { std::cout << "constructor called\n"; } INT(BaseImpl& that) : value(that.get_int()) { std::cout << "copy constructor called\n"; } bool is_string() { return false; } int get_int() { return value; } std::string get_string_copy() { char buf[33]; sprintf(buf, "%i", value); return buf; } std::string const& get_string_ref() { return dummy; } }; struct STRING : BaseImpl { std::string value; STRING(std::string s = "") : value(s) { std::cout << "constructor called\n"; } STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } bool is_string() { return true; } int get_int() { return atoi(value.c_str()); } std::string get_string_copy() { return value; } std::string const& get_string_ref() { return value; } }; struct Base { BaseImpl* impl; Base(BaseImpl* p = 0) : impl(p) {} ~Base() { delete impl; } }; int main() { Base b1(new INT(1)); Base b2(new STRING("Hello world")); Base b3(new INT(*b1.impl)); Base b4(new STRING(*b2.impl)); std::cout << "\n"; std::cout << b1.impl->get_int() << "\n"; std::cout << b2.impl->get_int() << "\n"; std::cout << b3.impl->get_int() << "\n"; std::cout << b4.impl->get_int() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_ref() << "\n"; std::cout << b2.impl->get_string_ref() << "\n"; std::cout << b3.impl->get_string_ref() << "\n"; std::cout << b4.impl->get_string_ref() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_copy() << "\n"; std::cout << b2.impl->get_string_copy() << "\n"; std::cout << b3.impl->get_string_copy() << "\n"; std::cout << b4.impl->get_string_copy() << "\n"; return 0; } It was necessary to add an if check in the STRING class to determine whether its safe to request a reference instead of a copy: Script code: a = "test"; b = a; c = 1; d = "" + c; /* not safe to request reference by standard */ C++ code: STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } If was hoping there's a way of moving that if check into compile time, rather than run time.

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• Does WCF use the ThreadPool to bring up new instances for a PerCall service?

  - by theburningmonk

  Hi, for a PerCall WCF service whose throttling has been set to be high (say, 200 max concurrent calls) would WCF bring up a new instance and invoke the request on a threadpool thread? If it does, then does this have an impact on the total number of concurrent calls allowed? I ask because I don't seem to ever hit the max number of concurrent calls I've set in the service throttling config but instead a fraction of that number - up to 50 on a 100 MaxConcurrentCalls setting and 160 on a 200 MaxConcurrentCalls setting. Thanks,

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• PHP: System Timezone Setting error

  - by marknt15

  Hi, I'm trying to use PHP in the terminal under MAMP but I got an error related to the system's timezone settings. How can I fix this error? $/Applications/MAMP/bin/php5/bin/php echo.php PHP Strict Standards: PHP Startup: It is not safe to rely on the system's timezone settings. Please use the date.timezone setting, the TZ environment variable or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'Asia/Manila' for 'PHT/8.0/no DST' instead in Unknown on line 0 Thanks

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• Using MonadPlus in FRP.Reactive.FieldTrip

  - by ony

  I'm studying FRP at this moment through FieldTrip adaptor. And hit the problem with strange way of frames scheduling and integration. So now I'm trying to build own marker Event for aligning Behaviour stepping. So... flipflop :: Behavior String flipflop = stepper "none" (xflip 2) where xflip t0 = do t <- withTimeE_ (atTime t0) return "flip" `mplus` xflop (t+3) xflop t0 = do t <- withTimeE_ (atTime t0) return "flop" `mplus` xflip (t+2) txtGeom = ((uscale2 (0.5::Float) *%) . utext . show <$>) main = anim2 (txtGeom . pure flipflop) Questions is: Why this example leads to memory leak? Is there safe way to build sequence of events where each next one is scheduled depending on previous?

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• Enums and Annotations

  - by PeterMmm

  I want to use an Annotation in compile-safe form. To pass the value() to the Annotation i want to use the String representation of an enum. Is there a way to use @A with a value from enum E ? public class T { public enum E { a,b; } // C1: i want this, but it won't compile @A(E.a) void bar() { // C2: no chance, it won't compile @A(E.a.toString()) void bar2() { } // C3: this is ok @A("a"+"b") void bar3() { } // C4: is constant like C3, is'nt it ? @A(""+E.a) void bar4() { } } @interface A { String value(); }

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• Is it a good idea to return " const char * " from a function?

  - by AJ

  Now I have a function that has to return a string. I saw a particular implementation where he returns a const char * from the function. Something like this: const char * GetSomeString() { ........ return somestlstring.c_str(); } SomeOtherFoo () { const char * tmp = GetSomeString(); string s = tmp; } Now I felt there is something potentially wrong with this. Is my gut feel right? or Is this a perfectly safe code? Kindly give me ur suggestions. I have a feeling return const char * this way might result in havoc.. Thanks, Arjun

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• Problems crossing the boundary between protected greasemonkey execution space and the unsafeWindow l

  - by Chilly

  Hi guys. Here is my problem: I've registered some callbacks into a Yahoo event driven webpage (betfair.com market views) and am trapping the betsPlaced events with a handler. So far so simple. Next stage is to get the event back into greasemonkey land, and while I know that from greasemoney space you can call unsafeWindow.stuff, there is no reverse operation (by design). So if I want to send the contents of the event over, say, a cometd queue, my carefully set up jquery, greasemonkey, YUI2, betfair environment fails by telling me that unsafeWindow processes cant call GM_ajax stuff. This is obviously safe and sane, but it basically stops me doing what I want to do. Has anyone tried doing this (ignore the cometd stuff, just general ajax calls) and succeeded? I've had a look at pages like this: http://wiki.greasespot.net/0.7.20080121.0%2B_compatibility but it doesnt appear to work for all the calls.

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• converting string to valid datetime

  - by Ranjana

  strdate=15/06/2010 DateTime dt = DateTime.Parse(strdate, System.Threading.Thread.CurrentThread.CurrentCulture.DateTimeFormat); i cannot able to get the datetime value as dd/mm/yyyy. it is giving exception 'string is not recognized as a valid datetime' oly if it is in 06/15/2010 it is working. how to get the same format in dt.

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• Detecting type of webserive in httpmodule

  - by Marcus

  Hi, Is there any way to detect the type of a webservice inside a httpmodule? The reason for this is that I want to do some property injection to the webservice before it's processed. I found this: http://social.msdn.microsoft.com/Forums/en/asmxandxml/thread/0e848eee-d353-4e67-b47f-89fddb600009 but that is one h..l of an ugly solution. Anyone have a nice solution?

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• C# Using singleton instead of a global static instance

  - by Farstucker

  I ran into a problem today and a friend recommended I use a global static instance or more elegantly a singleton pattern. I spent a few hours reading about singletons but a few things still escape me. Background: What Im trying to accomplish is creating an instance of an API and use this one instance in all my classes (as opposed to making a new connection, etc). There seems to be about 100 ways of creating a singleton but with some help from yoda I found some thread safe examples. ..so given the following code: public sealed class Singleton { public static Singleton Instance { get; private set; } static Singleton() { Instance = new Singleton(); } } How/Where would you instantiate the this new class and how should it be called from a separate class? Thanks for your help.

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• Parallel programming in C#

  - by Alxandr

  I'm interested in learning about parallel programming in C#.NET (not like everything there is to know, but the basics and maybe some good-practices), therefore I've decided to reprogram an old program of mine which is called ImageSyncer. ImageSyncer is a really simple program, all it does is to scan trough a folder and find all files ending with .jpg, then it calculates the new position of the files based on the date they were taken (parsing of xif-data, or whatever it's called). After a location has been generated the program checks for any existing files at that location, and if one exist it looks at the last write-time of both the file to copy, and the file "in its way". If those are equal the file is skipped. If not a md5 checksum of both files is created and matched. If there is no match the file to be copied is given a new location to be copied to (for instance, if it was to be copied to "C:\test.jpg" it's copied to "C:\test(1).jpg" instead). The result of this operation is populated into a queue of a struct-type that contains two strings, the original file and the position to copy it to. Then that queue is iterated over untill it is empty and the files are copied. In other words there are 4 operations: 1. Scan directory for jpegs 2. Parse files for xif and generate copy-location 3. Check for file existence and if needed generate new path 4. Copy files And so I want to rewrite this program to make it paralell and be able to perform several of the operations at the same time, and I was wondering what the best way to achieve that would be. I've came up with two different models I can think of, but neither one of them might be any good at all. The first one is to parallelize the 4 steps of the old program, so that when step one is to be executed it's done on several threads, and when the entire of step 1 is finished step 2 is began. The other one (which I find more interesting because I have no idea of how to do that) is to create a sort of worker and consumer model, so when a thread is finished with step 1 another one takes over and performs step 2 at that object (or something like that). But as said, I don't know if any of these are any good solutions. Also, I don't know much about parallel programming at all. I know how to make a thread, and how to make it perform a function taking in an object as its only parameter, and I've also used the BackgroundWorker-class on one occasion, but I'm not that familiar with any of them. Any input would be appreciated.

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• Strategy to keep track of stored files in the documents directory?

  - by mystify

  In my app, the user can save his input to disk. This is done with NSKeyedArchiver. Currently I simply name my files with a timestamp. But of course, the user may want to load one of them back in to keep on editing them. What would be the most reliable / safe strategy to keep track of those files? I need to present the user a list of those files, so that he can choose one to open. Currently I think of making an archived NSMutableArray which simply stores the file names, but I feel that this strategy is not really good. We all know when we save files sometimes something goes wrong, and this seems very likely to get currupted easily, or not? How would you do it?

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• GUI and Threading

  - by cam

  Isn't there a better way to handle GUI (WinForms) from another thread than creating a delegate for every single method I need to use? It seems like there would be a better way. Here's the current code I use for every single GUI method: private delegate void SetStatusTextDelegate(string set_text); public void SetStatusText(string set_text) { if (status_prog.InvokeRequired) { status_prog.Invoke(new SetStatusTextDelegate(SetStatusText), set_text); } else { status_prog.Text = set_text; } }

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• Is there something like clock() that works better for parallel code?

  - by Jared P

  So I know that clock() measures clock cycles, and thus isn't very good for measuring time, and I know there are functions like omp_get_wtime() for getting the wall time, but it is frustrating for me that the wall time varies so much, and was wondering if there was some way to measure distinct clock cycles (only one cycle even if more than one thread executed in it). It has to be something relatively simple/native. Thanks

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• How to compile a svn python binding for windows from the source?

  - by yin-gang

  I'm setting up a new svn+trac environment, the svn server's version is 1.6.11, then I can't find any corresponding pre-compiled svn-python binding, finally I found the following thread: http://stackoverflow.com/questions/677252/python-svn-bindings-for-windows so, my question is: how to compile from these source? http://svn.apache.org/viewvc/subversion/trunk/subversion/bindings/swig/python/

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• Compressing a hex string in Ruby/Rails

  - by PreciousBodilyFluids

  I'm using MongoDB as a backend for a Rails app I'm building. Mongo, by default, generates 24-character hexadecimal ids for its records to make sharding easier, so my URLs wind up looking like: example.com/companies/4b3fc1400de0690bf2000001/employees/4b3ea6e30de0691552000001 Which is not very pretty. I'd like to stick to the Rails url conventions, but also leave these ids as they are in the database. I think a happy compromise would be to compress these hex ids to shorter collections using more characters, so they'd look something like: example.com/companies/3ewqkvr5nj/employees/9srbsjlb2r Then in my controller I'd reverse the compression, get the original hex id and use that to look up the record. My question is, what's the best way to convert these ids back and forth? I'd of course want them to be as short as possible, but also url-safe and simple to convert. Thanks!

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• Implementing coroutines in Java

  - by JUST MY correct OPINION

  This question is related to my question on existing coroutine implementations in Java. If, as I suspect, it turns out that there is no full implementation of coroutines currently available in Java, what would be required to implement them? As I said in that question, I know about the following: You can implement "coroutines" as threads/thread pools behind the scenes. You can do tricksy things with JVM bytecode behind the scenes to make coroutines possible. The so-called "Da Vinci Machine" JVM implementation has primitives that make coroutines doable without bytecode manipulation. There are various JNI-based approaches to coroutines also possible. I'll address each one's deficiencies in turn. Thread-based coroutines This "solution" is pathological. The whole point of coroutines is to avoid the overhead of threading, locking, kernel scheduling, etc. Coroutines are supposed to be light and fast and to execute only in user space. Implementing them in terms of full-tilt threads with tight restrictions gets rid of all the advantages. JVM bytecode manipulation This solution is more practical, albeit a bit difficult to pull off. This is roughly the same as jumping down into assembly language for coroutine libraries in C (which is how many of them work) with the advantage that you have only one architecture to worry about and get right. It also ties you down to only running your code on fully-compliant JVM stacks (which means, for example, no Android) unless you can find a way to do the same thing on the non-compliant stack. If you do find a way to do this, however, you have now doubled your system complexity and testing needs. The Da Vinci Machine The Da Vinci Machine is cool for experimentation, but since it is not a standard JVM its features aren't going to be available everywhere. Indeed I suspect most production environments would specifically forbid the use of the Da Vinci Machine. Thus I could use this to make cool experiments but not for any code I expect to release to the real world. This also has the added problem similar to the JVM bytecode manipulation solution above: won't work on alternative stacks (like Android's). JNI implementation This solution renders the point of doing this in Java at all moot. Each combination of CPU and operating system requires independent testing and each is a point of potentially frustrating subtle failure. Alternatively, of course, I could tie myself down to one platform entirely but this, too, makes the point of doing things in Java entirely moot. So... Is there any way to implement coroutines in Java without using one of these four techniques? Or will I be forced to use the one of those four that smells the least (JVM manipulation) instead?

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