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  • Java Thread - Memory consistency errors

    - by Yatendra Goel
    I was reading a Sun's tutorial on Concurrency. But I couldn't understand exactly what memory consistency errors are? I googled about that but didn't find any helpful tutorial or article about that. I know that this question is a subjective one, so you can provide me links to articles on the above topic. It would be great if you explain it with a simple example.

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  • `enable_shared_from_this` has a non-virtual destructor

    - by Shtééf
    I have a pet project with which I experiment with new features of the upcoming C++0x standard. While I have experience with C, I'm fairly new to C++. To train myself into best practices, (besides reading a lot), I have enabled some strict compiler parameters (using GCC 4.4.1): -std=c++0x -Werror -Wall -Winline -Weffc++ -pedantic-errors This has worked fine for me. Until now, I have been able to resolve all obstacles. However, I have a need for enable_shared_from_this, and this is causing me problems. I get the following warning (error, in my case) when compiling my code (probably triggered by -Weffc++): base class ‘class std::enable_shared_from_this<Package>’ has a non-virtual destructor So basically, I'm a bit bugged by this implementation of enable_shared_from_this, because: A destructor of a class that is intended for subclassing should always be virtual, IMHO. The destructor is empty, why have it at all? I can't imagine anyone would want to delete their instance by reference to enable_shared_from_this. But I'm looking for ways to deal with this, so my question is really, is there a proper way to deal with this? And: am I correct in thinking that this destructor is bogus, or is there a real purpose to it?

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  • Same address, multiple shared_ptr counters, is it forbidden by C++ standard?

    - by icando
    Suppose I have some needs to do the following (This is just some imaginative code for discussion of the C++ standard, thus I won't discuss why I design it this way, so don't bother me something like: your design is wrong.) T* ptr = new T; shared_ptr<T> p(ptr); shared_ptr<T> q(ptr, SomeDeleterThatDoesnotDeleteButDoSomeOtherStuff()); Suppose the logic guarantees that p or some of its copies lives longer than any copies of q, so practically there won't be any problem. My question is, is it forbidden by C++ standard, e.g. explicitly stated as UB by C++ standard, that different shared_ptr counters share the same address? Thanks.

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  • How can I debug a session

    - by Organ Grinding Monkey
    I have been asked to work of a very large web application and deploy it. The problem that I'm facing here is that when I deploy the application and more that 1 user logs into the system, the sessions seem to cross over i.e: Person A logs in and works on the site, all good. When person B logs in, person A will then be logged in as person B as well. I have been asked to work of a very large web application and deploy it. The problem that I'm facing here is that when I deploy the application and more that 1 user logs into the system, the sessions seem to cross over i.e: Person A logs in and works on the site, all good. When person B logs in, person A will then be logged in as person B as well. If anyone has experienced this behaviour before and can steer me in the right direction, that would be first prize, Second prize would be to show me how I can debug this situation so that I can find out where the problem is and fix it. Some information about the application. From what I've been told and what I've seen within the app is that it started as a .Net 1.1 application and got upgraded to .Net 2 and that's why the log in system was done the way it is. (The application is huge and now complete and that's why I cant rewrite the whole user authentication process, it will just take to long and I don't know what effect it might have) All the Logged in User information is stored in properties that have been added in the Global.asax.vb file. (could this be the problem?) Any help here would be greatly appreciated

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  • Android full Screen flag gives an exception

    - by sukitha
    In my android app I set this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN ); Then my touch screen event doesnt’ work any more. Further Explaining, I have a button and onClick it changes the contentView by setContentView(R.layout.choose_player);. It works fine. But if you take the focus to the button by the trackball(making it yellow) and tap on it, it gives the exception. java.lang.IllegalArgumentException: parameter must be a descendant of this view

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  • Advice for keeping large C++ project modular?

    - by Jay
    Our team is moving into much larger projects in size, many of which use several open source projects within them. Any advice or best practices to keep libraries and dependancies relatively modular and easily upgradable when new releases for them are out? To put it another way, lets say you make a program that is a fork of an open source project. As both projects grow, what is the easiest way to maintain and share updates to the core? Advice regarding what I'm asking only please...I don't need "well you should do this instead" or "why are you"..thanks.

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  • Why isn't the boost::shared_ptr -> operator inlined?

    - by Alan
    Since boost::shared_ptr could be called very frequently and simply returns a pointer, isn't the -> operator a good candidate for being inlined? T * operator-> () const // never throws { BOOST_ASSERT(px != 0); return px; } Would a good compiler automatically inline this anyway? Should I lose any sleep over this? :-)

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  • PHP: Mapped Network Drives

    - by Abs
    Hello all, I have mapped a network drive to a computer in my home network. Now I am trying to access it via PHP - I did this quick test: echo opendir('Z:\\'); This gives me: Warning: opendir(Z:\) [function.opendir]: failed to open dir: No error in C:\wamp\www\webs\tester-function.php on line 3 What have I done wrong here? I don't want my users typing in the UNC path so is there a way to get the UNC path for them and maybe that will work when I try to access it? This is possible in Microsoft languages but I am not sure how to get PHP to do this - maybe using a cmd.exe command? Please note, the mapped drive does exist as I can see it and I can access it. It also does not appear to be a permissions problem as I am assuming it would of complained about this IF it could access that drive...right? Thanks all for any help

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  • Which libraries use the "We Know Where You Live" optimization for std::make_shared?

    - by KnowItAllWannabe
    Over two years ago, Stephan T. Lavavej described a space-saving optimization he implemented in Microsoft's implementation of std::make_shared, and I know from speaking with him that Microsoft has nothing against other library implementations adopting this optimization. If you know for sure whether other libraries (e.g., for Gnu C++, Clang, Intel C++, plus Boost (for boost::make_shared)) have adopted this implementation, please contribute an answer. I don't have ready access to that many make_shared implementations, nor am I wild about digging into the bowels of the ones I have to see if they've implemented the WKWYL optimization, but I'm hoping that SO readers know the answers for some libraries off-hand. I know from looking at the code that as of Boost 1.52, the WKWYL optimization had not been implemented, but Boost is now up to version 1.55. Note that this optimization is different from std::make_shared's ability to avoid a dedicated heap allocation for the reference count used by std::shared_ptr. For a discussion of the difference between WKWYL and that optimication, consult this question.

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  • shared_ptr as class member

    - by idimba
    It's common to declared contained objects as a pointers to that class, while "forward declarating" them in header file. This in order to reduce physical dependencies in code. For example class B; // forward declaration class A { private: B* pB; }; Would it be good idea to declare such a member as shared_ptr, instead of naked pointer? I would prefer scoped_ptr, but AFAIKit it won't be in standard.

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  • How do I create two mutual producer/consumers with internal state in Haskell?

    - by Keith
    I've got an agent that takes in states and returns actions, while keeping an internal representation of the utility of state/action pairs. I've also got an environment that takes in actions and returns state/reward pairs. I need to be able to set the agent up with a start state and then continuously go from agent -(action)- environment -(state, reward)- agent -(action)-... However, the internal states (which need to be updated every iteration) need to stay private (that is, within the agent or the environment). This means that I can't simply call environment as a function within the agent using state and action as arguments. I'm somewhat of a Haskell noobie, so I'm not even sure if this is possible.

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  • Force an object to be allocated on the heap

    - by Warren Seine
    A C++ class I'm writing uses shared_from_this() to return a valid boost::shared_ptr<>. Besides, I don't want to manage memory for this kind of object. At the moment, I'm not restricting the way the user allocates the object, which causes an error if shared_from_this() is called on a stack-allocated object. I'd like to force the object to be allocated with new and managed by a smart pointer, no matter how the user declares it. I thought it could be done through a proxy or an overloaded new operator, but I can't find a proper way of doing that. Is there a common design pattern for such usage? If it's not possible, how can I test it at compile time?

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  • C++ static classes & shared_ptr memory leaks

    - by HardCoder1986
    Hello! I can't understand why does the following code produce memory leaks (I am using boost::shared_ptr with static class instance). Could someone help me? #include <crtdbg.h> #include <boost/shared_ptr.hpp> using boost::shared_ptr; #define _CRTDBG_MAP_ALLOC #define NEW new(_NORMAL_BLOCK, __FILE__, __LINE__) static struct myclass { static shared_ptr<int> ptr; myclass() { ptr = shared_ptr<int>(NEW int); } } myclass_instance; shared_ptr<int> myclass::ptr; int main() { _CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF | _CRTDBG_CHECK_ALWAYS_DF | _CrtSetDbgFlag(_CRTDBG_REPORT_FLAG)); return 0; }

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  • C - fork() and sharing memory

    - by Ben
    I need my parent and child process to both be able to read and write the same variable (of type int) so it is "global" between the two processes. I'm assuming this would use some sort of cross-process communication and have one variable on one process being updated. I did a quick google and IPC and various techniques come up but I don't know which is the most suitable for my situation. So what technique is best and could you provide a link to a noobs tutorial for it. Thanks.

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  • What factors could cause the scalability issue on a 10-core CPU?

    - by JackWM
    I am tuning the performance of parallel Java programs. And want to check the impacts from the Architecture. I'm look into the Intel 10-core CPU, Intel(R) Xeon(R) CPU E7-L8867. I found my program only scales up to 5 cores. What could be the causes? I'm considering the Architecture effects. e.g. memory contention? More specifically, Are the 10 cores symmetric to each other? How many memory controllers does it have?

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  • Why is std::tr1::shared_ptr<>.reset() so expensive?

    - by Paul Oyster
    Profiling some code that heavily uses shared_ptrs, I discovered that reset() was surprisingly expensive. For example: struct Test { int i; Test() { this->i = 0; } Test(int i) { this->i = i; } } ; ... auto t = make_shared<Test>(1); ... t.reset(somePointerToATestObject); Tracing the reset() in the last line (under VC++ 2010), I discovered that it creates a new reference-counting object. Is there a cheaper way, that reuses the existing ref-count and does not bother the heap?

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  • Using jquery to change checkbox status

    - by Jeff
    Hi everyone! I have a list of items that have checkboxes associated with them, and the items are beneath a list header, which also has a checkbox(for db purposes only) which is actually hidden from view. I need to make it so that if any of the checkboxes beneath the header is checked, then the header checkbox is checked as well. BUT I also need to make it so that if all of the checkboxes are unchecked, then the header one is unchecked...how hard is this going to be? This is how I have it setup now: if($('.childCheckBox').is(":checked")){ $('#parentBox').attr('checked', true); } Now I am thinking that if I were to do something where I add an else if clause: else if($('.proBox2').is(not)(":checked"){ alert("uncheck parent"); } But I don't know the correct syntax for is-not, or isn't, or even if there is anything that will do that. Are there any thoughts out there? I need the box to check if one is selected and uncheck if none are selected. Thanks!!

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  • Put objects which are decorated with [DataContract] into a StateServer?

    - by Dave
    Is there anyway to stick objects which are decorated with DataContract attributes but not decorated with Serializable attributes in to a SqlServer StateServer? In other words, I would prefer not having to decorate these objects with the Serializable attribute as I will also have to implement IXmlSerizable on all of these objects because they do not have empty contstructors, and non-public setters for properties.

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  • Unsafe, super-fast cross-process memory buffer?

    - by John
    Cross-process memory buffers always have some overhead, and my understanding is this is quite high. But what if you're implementing a cross-process render-buffer, this isn't critically important in the same way as other data so are there techniques we can use to get 'raw' access to a chunk of memory from multiple processes, with no safety nets apart from it not crashing? Or do modern operating systems simply not work with unabstracted memory in a way to make this possible? I'm working in C++ but the question applies to Win XP/Vista/7, MacOSX 10.5+ (& Linux less importantly).

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  • Can Silverlight be linked with a C++ static library ?

    - by Niklaos
    Hi, I'm currently doing research to start a new project. This project will be in 2 parts a light Client (probably console) and an heavy one using silverlight. The light client must be cross-platform. However, they will both use the same Core (by the way, the core will need to use the sockets). I'd like to use C++ to build the light client but given that the core is common to both applications, it would be much appreciated if it's could be the same code. So the question is quite simple : Can Silverlight be compilated with a C++ static library ? And if it's possible, what about cross-platform issues (with moonlight) ? If it's not possible. Which language can i use to work with silverlight while being cross-platform ? Because of performance, a compilated language will be better ! Thanks for your expertise :)

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