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  • C++/Qt - Memory allocation question

    - by HardCoder1986
    Hello! I recently started investigating Qt for myself and have the following question: Suppose I have some QTreeWidget* widget. At some moment I want to add some items to it and this is done via the following call: QList<QTreeWidgetItem*> items; // Prepare the items QTreeWidgetItem* item1 = new QTreeWidgetItem(...); QTreeWidgetItem* item2 = new QTreeWidgetItem(...); items.append(item1); items.append(item2); widget->addTopLevelItems(items); So far it looks ok, but I don't actually understand who should control the objects' lifetime. I should explain this with an example: Let's say, another function calls widget->clear();. I don't know what happens beneath this call but I do think that memory allocated for item1 and item2 doesn't get disposed here, because their ownage wasn't actually transfered. And, bang, we have a memory leak. The question is the following - does Qt have something to offer for this kind of situation? I could use boost::shared_ptr or any other smart pointer and write something like shared_ptr<QTreeWidgetItem> ptr(new QTreeWidgetItem(...)); items.append(ptr.get()); but I don't know if the Qt itself would try to make explicit delete calls on my pointers (which would be disastrous since I state them as shared_ptr-managed). How would you solve this problem? Maybe everything is evident and I miss something really simple?

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  • Allocation of IP Address in Ad hoc systems

    - by Kasturi
    Me and my friends play Age of Empires every weekend and create an Ad-hoc network each time before playing. But each time we all get the SAME IP Address even if a new ad-hoc network is created. Is this something to do with the Game's algorithm or does the laptop remember our previous IP Address. EDIT: What is the algorithm that is used to distribute the IP Addresses? If the algorithm uses random function how come same IP addresses are being allocated.

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  • How to increase memory allocation to program

    - by Vaibhav
    When I try to initialize a 3D array of size 300*300*4 in a C program, my program stops running and reports stack overflow error. The system I am using has 3GB RAM, which should be sufficeint. Is there any way to increase memory allocated to a program? I am using Dev C++ on Windows Vista.

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  • C++ std::vector memory/allocation

    - by aaa
    from a previous question about vector capacity, http://stackoverflow.com/questions/2663170/stdvector-capacity-after-copying, Mr. Bailey said: In current C++ you are guaranteed that no reallocation occurs after a call to reserve until an insertion would take the size beyond the value of the previous call to reserve. Before a call to reserve, or after a call to reserve when the size is between the value of the previous call to reserve and the capacity the implementation is allowed to reallocate early if it so chooses. So, if I understand correctly, in order to assure that no relocation happens until capacity is exceeded, I must do reserve twice? can you please clarify it? I am using vector as a memory stack like this: std::vector<double> memory; memory.reserve(size); memory.insert(memory.end(), matrix.data().begin(), matrix.data().end()); // smaller than size size_t offset = memory.size(); memory.resize(memory.capacity(), 0); I need to guarantee that relocation does not happen in the above. thank you. ps: I would also like to know if there is a better way to manage memory stack in similar manner other than vector

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  • I have an Xcode static library project, how do I add a test target to it so I can run it there? (Ins

    - by zekel
    I want to be able to test library code in the library target so I don't have to switch over to a separate project to run it. I see how to add a target, but I'm not sure how to set it up to run like the "Command Line Tool" project template does. I tried adding a new "Shell Tool" target, but I don't know how to make it run like one. What build settings do I have to add to that target? What files (main.m?) do I need to start it up?

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  • How to static analyze C++ and Objective-C++ code?

    - by Plumenator
    The "Build and analyze" option doesn't seem to work for .cpp and .mm files. I tried "clang --analyze" on individual files without any standard #includes and it works well. However I'm not able to run it on my Xcode project. I couldn't figure out a way to make clang find the standard #includes like even UIKit.h. Any clues?

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  • C++: Allocation of variables in a loop

    - by Rosarch
    Let's say I have a loop like this: vector<shared_ptr<someStruct>> vec; int i = 0; while (condition) { i++ shared_ptr<someStruct> sps(new someStruct()); WCHAR wchr[20]; memset(wchr, i, 20); sps->pwsz = wchr; vec.push_back(sps); } At the end of this loop, I see that for each sps element of the vector, sps->pwsz is the same. Is this because I'm passing a pointer to memory allocated in a loop, which is destructed after each iteration, and then refilling that same memory on the next iteration?

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  • Objective-C: Allocation in one thread and release in other

    - by user423977
    Hi I am doing this in my Main Thread: CCAnimation *anim; //class variable [NSThread detachNewThreadSelector:@selector(loadAimation) toTarget:self withObject:nil]; In loadAimation: -(void) loadAimation { NSAutoreleasePool *autoreleasepool = [[NSAutoreleasePool alloc] init]; anim = [[CCAnimaton alloc] init]; [autoreleasepool drain]; } And in main thread I release it: [anim release]; Now I want to ask if this is fine regarding memory management.

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  • Limiting object allocation over multiple threads

    - by John
    I have an application which retrieves and caches the results of a clients query. The client then requests different chunks of data and the application sends the relevant results and removes them from the cache. A new requirement for this application is that there needs to be a run-time configurable maximum number of results which may be cached. I've taken the naive approach and implemented this by using a counter under a lock which is incremented every time a result is cached and decremented whenever a result is removed from the cache. Unfortunately, this has drastically reduced the applications performance when processing a large number of concurrent requests. I have tried both a critical section lock and spin-lock; the performance improves a bit with a spin-lock, but is still unacceptably slow. Is there a better way to solve this problem which may improve performance? Right now I have a thread pool that services requests and each request is tied to a Request object which stores that cached results for that particular request. Here is a simplified pseudo code version of my current implementation: void ResultCallback( Result result, Request *request ) { lock totalResultsCached lock cachedLimit if( totalResultsCached + 1 > cachedLimit ) { unlock cachedLimit unlock totalResultsCached //cancel the request return; } ++totalResultsCached; unlock cachedLimit unlock totalResultsCached request.add(result) } void SendResults( int resultsToSend, Request *request ) { while ( resultsToSend > 0 ) { send(request.remove()) lock totalResultsCached --totalResultsCached unlock totalResultsCached --resultsToSend; } }

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  • Dynamic allocation in C

    - by Kerby82
    I'm writing a program and I have the following problem: char *tmp; sprintf (tmp,"%ld",(long)time_stamp_for_file_name); Could someone explain how much memory allocate for the string tmp. How many chars are a long variable? Thank you, I would appreciate also a link to an exahustive resource on this kind of information. Thank you

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  • dynamic memory allocation [closed]

    - by gcc
    i wanna write a program that creates (allocating memory) and manipulates (adding elements and increasing memory etc.) integer arrays dynamically according to given input sequences. input sequence which starts with the maximum number of arrays, includes integers to be put into arrays and some one letter characters which are commands to carry out some tasks (activating next array, deleting an array etc). also, i wanna create *c_arrays which is the address of the array whose elements are the actual capacities (How many integer slots are already allocated for an array?) of arrays how should i organize(set up) the algorithm?

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  • Dynamic memory allocation with default values

    - by viswanathan
    class A { private: int m_nValue; public: A() { m_nValue = 0; } A(int nValue) { m_nValue = nValue); ~A() {} } Now in main if i call A a(2);// 2 will be assigned for m_nValue of object A. Now how do we do this if i want to define an array of objects. Also how do we do this if i dynamically create objects using operator new like A *pA; pA = new A[5];// while creating the object i want the parameterised constructor to be //called I hope the question is clear. Do let me know if more explanation is needed

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  • Translate Java class with static attributes and Annotation to Scala equivalent

    - by ifischer
    I'm currently trying to "translate" the following Java class to an equivalent Scala class. It's part of a JavaEE6-application and i need it to use the JPA2 MetaModel. import javax.persistence.metamodel.SingularAttribute; import javax.persistence.metamodel.StaticMetamodel; @StaticMetamodel(Person.class) public class Person_ { public static volatile SingularAttribute<Person, String> name; } A dissassembling of the compiled class file reveals the following information for the compiled file: > javap Person_.class : public class model.Person_ extends java.lang.Object{ public static volatile javax.persistence.metamodel.SingularAttribute name; public model.Person_(); } So now i need an equivalent Scala file that has the same structure, as JPA depends on it, cause it resolves the attributes by reflection to make them accessible at runtime. So the main problem i think is that the attribute is static, but the Annotation has to be on an (Java)Object (i guess) My first naive attempt to create a Scala equivalent is the following: @StaticMetamodel(classOf[Person]) class Person_ object Person_ { @volatile var name:SingularAttribute[Person, String] = _; } But the resulting classfile is far away from the Java one, so it doesn't work. When trying to access the attributes at runtime, e.g. "Person_.firstname", it resolves to null, i think JPA can't do the right reflection magic on the compiled classfile (the Java variant resolves to an instance of org.hibernate.ejb.metamodel.SingularAttributeImpl at runtime). > javap Person_.class : public class model.Person_ extends java.lang.Object implements scala.ScalaObject{ public static final void name_$eq(javax.persistence.metamodel.SingularAttribute); public static final javax.persistence.metamodel.SingularAttribute name(); public model.Person_(); } > javap Person_$.class : public final class model.Person__$ extends java.lang.Object implements scala.ScalaObject public static final model.Person__$ MODULE$; public static {}; public javax.persistence.metamodel.SingularAttribute name(); public void name_$eq(javax.persistence.metamodel.SingularAttribute); } So now what i'd like to know is if it's possible at all to create a Scala equivalent of the Java class? It seems to me that it's absolutely not, but maybe there is a workaround or something (except just using Java, but i want my app to be in Scala where possible) Any ideas, anyone? Thanks in advance!

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  • UITableView: Handle cell selection in a mixed cell table view static and dynamic cells

    - by AlexR
    I am trying to mix dynamic and static cells in a grouped table view: I would like to get two sections with static cells at the top followed by a section of dynamic cells (please refer to the screenshot below). I have set the table view contents to static cells. Edit Based on AppleFreak's advice I have changed my code as follows: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell; if (indexPath.section <= 1) { // section <= 1 indicates static cells cell = [super tableView:tableView cellForRowAtIndexPath:indexPath]; } else { // section > 1 indicates dynamic cells CellIdentifier = [NSString stringWithFormat:@"section%idynamic",indexPath.section]; cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath]; } return cell; } However, my app crashes with error message Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'UITableView dataSource must return a cell from tableView:cellForRowAtIndexPath:' for section 0 and row 0. The cell returned from cell = [super tableView:tableView cellForRowAtIndexPath:indexPath] for section 0 and row 0 is nil. What is wrong with my code? Could there be any problems with my outlets? I haven't set any outlets because I am subclassing UITableViewController and supposedly do not any outlets for tableview to be set (?). Any suggestions on how to better do it? Edit II I have recreated my scene in storyboard (please refer to my updated screen shot above) and rewritten the view controller in order to start from a new base. I have also read the description in Apple's forum as applefreak suggested. However, I run in my first problem with the method numberOfSectionsInTableView:tableView, in which I increment the number of static sections (two) by one. - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return [super numberOfSectionsInTableView:tableView] + 1 ; } The app crashed with the error message: Terminating app due to uncaught exception 'NSRangeException', reason: '* -[__NSArrayI objectAtIndex:]: index 2 beyond bounds [0 .. 1]' Why is this code not working for me even though I followed Apple's and applefreak recommendations? It is possible that the tableView has changed a bit in iOS 6? Solution: I got this to work now using AppleFreaks code sample in his answer below. Thank you, AppleFreak! Edit III: Cell Selection: How can I handle cell selection in a mixed (dynamic and static cells) cell table view? When do I call super and when do I call self tableView? When I use [[super tableView] selectRowAtIndexPath:indexPath animated:NO scrollPosition:UITableViewScrollPositionNone] and try to check for the selected index paths with: UITableView *tableView = [super tableView]; if ( [[tableView indexPathForSelectedRow] isEqual:customGrowthIndexPath] ) { .. } I get an return value of nil. As I can't find the source of my error, I really would appreciate your help

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  • C++: Templates for static functions?

    - by Rosarch
    I have a static Utils class. I want certain methods to be templated, but not the entire class. How do I do this? This fails: #pragma once #include <string> using std::string; class Utils { private: template<class InputIterator, class Predicate> static set<char> findAll_if_rec(InputIterator begin, InputIterator end, Predicate pred, set<char> result); public: static void PrintLine(const string& line, int tabLevel = 0); static string getTabs(int tabLevel); template<class InputIterator, class Predicate> static set<char> Utils::findAll_if(InputIterator begin, InputIterator end, Predicate pred); }; Error: utils.h(10): error C2143: syntax error : missing ';' before '<' utils.h(10): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int utils.h(10): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int utils.h(10): error C2238: unexpected token(s) preceding ';' utils.h(10): error C2988: unrecognizable template declaration/definition utils.h(10): error C2059: syntax error : '<' What am I doing wrong? What is the correct syntax for this? Incidentally, I'd like to templatize the return value, too. So instead of: template<class InputIterator, class Predicate> static set<char> findAll_if_rec(InputIterator begin, InputIterator end, Predicate pred, set<char> result); I'd have: template<class return_t, class InputIterator, class Predicate> static return_t findAll_if_rec(InputIterator begin, InputIterator end, Predicate pred, set<char> result); How would I specify that: 1) return_t must be a set of some sort 2) InputIterator must be an iterator 3) InputIterator's type must work with return_t's type. Thanks.

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  • Set up two IP addresses with one gateway?

    - by Ahmed
    I would like to ask if it is possible to set up two static IPs from same subnet through one gateway? and How if it is? What I am interested in is described here Routing for multiple uplinks/providers, but in my case I have two IP addresses from one provider, both are on same subnet and off course I have internet access on both. I have two NICs, but I don't mind to go with one if that makes it possible. Any thought is appreciated!

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  • MMGR Questions, code use and thread-saftey

    - by chadb
    1) Is MMGR thread safe? 2) I was hoping someone could help me understand some code. I am looking at something where a macro is used, but I don't understand the macro. I know it contains a function call and an if check, however, the function is a void function. How does wrapping "(m_setOwner (FILE,_LINE_,FUNCTION),false)" ever change return types? #define someMacro (m_setOwner(__FILE__,__LINE__,__FUNCTION__),false) ? NULL : new ... void m_setOwner(const char *file, const unsigned int line, const char *func); 3) What is the point of the reservoir? 4) On line 770 ("void *operator new(size_t reportedSize)" there is the line "// ANSI says: allocation requests of 0 bytes will still return a valid value" Who/what is ANSI in this context? Do they mean the standards? 5) This is more of C++ standards, but where does "reportedSize" come from for "void *operator new(size_t reportedSize)"? 6) Is this the code that is actually doing the allocation needed? "au-actualAddress = malloc(au-actualSize);"

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  • SQL Scenario of allocating ids to user

    - by Enjoy coding
    Hi, I have an sql scenario as follows which I have been trying to improve. There is a table 'Returns' which is having ids of the returned goods against a shop for an item. Its structure is as below. Returns ------------------------- Return ID | Shop | Item ------------------------- 1 Shop1 Item1 2 Shop1 Item1 3 Shop1 Item1 4 Shop1 Item1 5 Shop1 Item1 There is one more table Supplier with Shop, supplier and Item as shown below. Supplier --------------------------------- Supplier | Shop | Item | Volume --------------------------------- supp1 Shop1 Item1 20% supp2 Shop1 Item1 80% Now as you see supp1 is supplying 20 % of total item1 volume and supp2 is supplying 80% of Item1 to shop1. And there were 5 return of items against the same Item1 for same Shop1. Now I need to allocate any four return IDs to Supp1 and remaining one return Id to supp2. This allocation of numbers is based on the ratio of the supplied volume percentage of the supplier. This allocation varies depending on the ratio of volume of supplied items. Now I have tried a method of using RANKs as shown below by use of temp tables. temp table 1 will have Shop, Return Id, Item, Total count of return IDs and Rank of the return id. temp table 2 will have shop, Supplier, Item and his proportion and rank of proportion. Now I am facing the difficulty in allocating top return ids to top supplier as illustrated above. As SQL doesnt have loops how can I achieve this. I have been tying several ways of doing this. Please advice. My environment is Teradata (ANSI SQL is enough). Thanks in advance.

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  • What to throw in a C++ class wrapping a C library ?

    - by ereOn
    I have to create a set of wrapping C++ classes around an existing C library. For many objects of the C library, the construction is done by calling something like britney_spears* create_britney_spears() and the opposite function void free_britney_spears(britney_spears* brit). If the allocation of a britney_spears fails, create_britney_spears() returns NULL. This is, as far as I know, a very common pattern. Now I want to wrap this inside a C++ class. //britney_spears.hpp class BritneySpears { public: BritneySpears(); private: boost::shared_ptr<britney_spears> m_britney_spears; }; And here is the implementation: // britney_spears.cpp BritneySpears::BritneySpears() : m_britney_spears(create_britney_spears(), free_britney_spears) { if (!m_britney_spears) { // Here I should throw something to abort the construction, but what ??! } } So the question is in the code sample: What should I throw to abort the constructor ? I know I can throw almost anything, but I want to know what is usually done. I have no other information about why the allocation failed. Should I create my own exception class ? Is there a std exception for such cases ? Many thanks.

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  • Serving static content from cookie less domain and mod_deflate

    - by Saif Bechan
    I have two domain. One domain with my main website and the other with js/css/etc.. files, static content. mod_deflate is enabled for both domains, but when i run ySlow in FireFox it says none of my static content is compressed. When i bring back the js or css file to my normal domain it gets compressed right. Only when its served from the other domain is it not compressed. Do i have to do some more configuration for this to work? I am using this line in my .htaccess file AddOutputFilterByType DEFLATE application/x-javascript text/css text/html text/xml text/plain application/x-httpd-php I tried to but the line in my httpd.conf file but it gives me the same results. PS. If this is more of a serverfault question i am sorry for this. But i see a lot of questions here concerning mod_deflate and ySlow

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  • What Raid should I use for Website Static Files / Content

    - by Simon
    I'm building a Web server (IIS7) and would like to know the best practice for storing static content and the uploaded files of website's users (predominantly pictures, but also other documents like pdf's). I will keep the operating System on a Raid 1 array. Where should I be keeping the actual website's pages & files, it's own static content, and that of it's users? Should I be placing this content on a seperate raid array, and if so which type? I was considering using SLC SSD's (Such as the Intel's X25-e) but the following issues came to light. Will the SLC SSD's give any improvement over a 2.5" 15k SAS Drive for this type of content? If I did use SSD's, I'm under the belief I would still need to use Raid for redundancy, yet I've heard Intel X25-e's don't support TRIM. Does this scrap them as a legitimate option?

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  • Dell XPS 420: Turning computer on, video ports showing static

    - by Roy Rico
    I have a Dell XPS 420 which i recently upgraded with a EVGA GTX 550TI and a 80GB SSD Drive. I converted this machine into a home theater PC. Which I've always had on. The computer wasn't responding, and so i restarted it and when it started, video ports showing static. I was getting static on my TV thru both DVI ports and the mini HDMI port. I assumed my video card had gone bad, but i completely replaced it and still the same behavior is occurring. I do not know how to diagnosis this issue. Any thoughts?

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  • ignore ipv6 router advertisements for static addresses with bonded interfaces

    - by boran
    I need to attribute static IPv6 addresses (not use autoconfigured addresses, and ignore router advertisements). This can be done as follows for a standard interface like eth0 iface eth0 inet6 static address myprefix:mysubnet::myip gateway myprefix:mysubnet::mygatewayip netmask 64 pre-up /sbin/sysctl -q -w net.ipv6.conf.$IFACE.autoconf=0 pre-up /sbin/sysctl -q -w net.ipv6.conf.$IFACE.accept_ra=0 However, how can this be done for bonded interfaces? using the "all" interface does not work. Systems is Ubuntu 10.04, 2.6.24-24-server. If one uses the above sysctl command for the bond0, the networking hangs on boot, because /proc/sys/net/ipv6/conf/bond0 does not yet exist and cannot be written to. One the system has booted /proc/sys/net/ipv6/conf/bond0 exist, so one solution after booting is to add the following to /etc/rc.local: /sbin/sysctl -q -w net.ipv6.conf.bond0.autoconf=0 /sbin/sysctl -q -w net.ipv6.conf.bond0.accept_ra=0 /etc/init.d/networking restart and this has the desired effect, the autoconfig v6 address disappears. Seems like a bit of a hack though, are there better solutions?

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