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• Is there a way to cause a new C++ class instance to fail, if certain conditions in the contructor ar

  - by Jim Fell

  As I understand it, when a new class is instantiated in C++, a pointer to the new class is returned, or NULL, if there is insufficient memory. I am writing a class that initializes a linked list in the constructor. If there is an error while initializing the list, I would like the class instantiator to return NULL. For example: MyClass * pRags = new MyClass; If the linked list in the MyClass constructor fails to initialize properly, I would like pRags to equal NULL. I know that I can use flags and additional checks to do this, but I would like to avoid that, if possible. Does anyone know of a way to do this? Thanks.

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• Image gets slightly erased on SWT/Windows

  - by zvikico

  I have an Eclipse plugin which includes a view. The view has several icons in the toolbar. I'm experiencing a very strange problem: on Windows, in some occasions (after prolonged use), one of the icons gets slightly erased. This does not happen on other platforms. This looks like a memory leak or some other resource misuse, but I just can't figure out where. The rest of the icons, which are initialized and used in the exact same manner are not affected. I tried working with Sleak, but I really don't see anything out of the ordinary. Any help would be appreciated.

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• what mysql table structure is better

  - by Sergey

  I have very complicated search algorithm on my site, so i decided to make a table with cache or maybe all possible results. I wanna ask what structure would be better, or maybe not the one of them? (mySQL) 1) word VARCHAR, results TEXT or BLOB where i'll store ids of found objects (for example 6 chars for each id) 2) word VARCHAR, result INT, but words are not unique now i think i'll have about 200 000 rows in 1) with 1000-10000 ids each row or 200 000 000+ rows in 2) First way takes more storage memory but i think it would be much faster to find 1 unique row among 200 000, than 1000 rows among 200 mln non unique rows i think about index on word column and no sphinx. So that do YOU think? p.s. as always, sorry for my english if it's not very good.

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• iPhone xcode array losing state after load

  - by Frames84

  Right i've had a search around and can't find anything. @synthesize list; // this is an NSArry -(void) viewDidLoad { NSArray *arr = [self getJSONFeed]; self.List = [arr retain]; // if i copy the access code into here it works fine. } -(void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { NSUInteger row = [indexPath row]; NSArray *vals = [list objectAtIndex:row] retain]; NSString *id = [vals valueForKey:@"id"]; // ERROR } right i've taken some of the code to try and provide it as simple as possible, ignore typo's and memory leaks this is sorted. Basically when I select a row I can't get data out of my 'list' array object. Please can anyone help me out?

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• C string program

  - by mrblippy

  Hi, i have been given a task to do ar school that must read three strings in, store the third string in dynamically allocated memory and print out the last 4 letters of the first word alphabetically. Here is the program i have so far but the strings are all stored in different variables, making them hard to sort. if anyone could give me a hand and help me finish this program i would be very grateful. thanks #include <stdio.h> #include <stdlib.h> #include <string.h> int main() { char word1[101]; char word2[101]; char* word3; char buffer[101]; scanf("%s", word1); scanf("%s", word2); scanf("%s", buffer); word3 = (char *) malloc(strlen(buffer)+1); strcpy(word3, buffer); return 0; }

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• Question regrarding declaring a property

  - by Simon

  Hi. We declare properties using the @property keyword and synthesize it in the implementation file. My question is, What if I declare a property using the @property keyword and also declare a variable in the interface block with the same name? For example, consider the following code, Interface: @interface myClass : NSObject { NSString *myClass_name; // LINE 1 } @property(nonatomic, retain) NSString *myClass_name; // LINE 2 @end Implementation: @implementation myClass @synthesize myClass_name @end Declaring myClass_name in LINE 1 will make any problem? Like any reference problem or any unnecessary memory consumption problem?

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• Way around ASP.NET session being shared across multiple tab windows

  - by ace

  I'm storing some value in an asp.net session on the first page. On the next page, this session value is being read. However if multiple tabs are opened and there are multiple page 1-page 2 navigation going on, the value stored in session gets mixed up since the session is shared between the browser tabs. I'm wondering what are the options around this : Query String: Passing value between the pages using query string, I don't want to take this approach since there can be multiple anchor tags on page 1 linking to page 2 and I can not rewrite the URLs of each tag since they are dynamic. Cookies??? In-memory cookies are shared across browser tabs too, same as the session cookie, rite ? Any other option?

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• Byte order (endian) of int in NSLog?

  - by Eonil

  NSLog function accepts printf format specifiers. My question is about %x specifier. Does this print hex codes as sequence on memory? Or does it have it's own printing sequence style? unsigned int a = 0x000000FF; NSLog(@"%x", a); Results of above code on little or big endian processors are equal or different? And how about NSString's -initWithFormat method? Does it follows this rule equally?

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• Linq To Sql Entity Updated from Trigger

  - by James Helms

  I have a Table called Address. I have a Trigger for insert on that table that does some spacial calculations on the address that determines what neighborhood boundaries it is in. address = new Address { Street = this.Street, City = this.City, State = this.State, ZipCode = this.ZipCode, latitude = this.Latitude, longitude = this.Longitude, YearBuilt = this.YearBuilt, LotSize = this.LotSize, FinishedSize = this.FinishedSize, Bedrooms = this.Bedrooms, Bathrooms = this.Bathrooms, UseCode = this.UseCode, HOA = this.HOA, UpdateDate = DateTime.Now }; db.AddToAddresses(address); db.SaveChanges(); In the database i can clearly see that the Trigger ran and updated the neighborhoodID in the address table for the row. I tried to just reload that record to get the assigned id like this: address = (from a in db.Addresses where a.AddressID == address.AddressID select a).First(); In the debugger i can clearly see that the address.AddressID is correct, entity doesn't update in memory. Is there any work around for this?

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• Undefined behaviour with non-virtual destructors - is it a real-world issue?

  - by Roddy

  Consider the following code: class A { public: A() {} ~A() {} }; class B: public A { B() {} ~B() {} }; A* b = new B; delete b; // undefined behaviour My understanding is that the C++ standard says that deleting b is undefined behaviour - ie, anything could happen. But, in the real world, my experience is that ~A() is always invoked, and the memory is correctly freed. if B introduces any class members with their own destructors, they won't get invoked, but I'm only interested in the simple kind of case above, where inheritance is used maybe to fix a bug in one class method for which source code is unavailable. Obviously this isn't going to be what you want in non-trivial cases, but it is at least consistent. Are you aware of any C++ implementation where the above does NOT happen, for the code shown?

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• Processing large recordsets in Rails

  - by japancheese

  Hello, I'm trying to perform a daily operation on a larger than normal dataset (2m+ records). However, Rails seems to take a very long time performing operations on such a dataset. Operations like Dataset.all.each do |data| ... end take a very long time to complete (I assume this is because it can't fit all the items into memory at once, right?). Does anyone have any strategies on how I could handle this situation? I know SQL would probably speed up the process, but I'm looking to use the Rails environment as I can do many more complicated things to the data than I can with just SQL statements.

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• IPhone CoreData: How should I relate many child entities to thier parents

  - by Robert

  I am trying to import data from a database that uses primary key / forign key relations to a core data database in Xcode. I have code that creates hundreds of child entities in a managed object context: Each child has an ID that corresponds to a parent. child1 parentID = 3 child2 parentID = 17 child3 parentID = 17 ... childn parentID = 5 I now need to relate each child to its parent. The parents are all stored in persistent memory. My first thought was to preform a fetch for each child to get its parent. However, I think this would be slow. Am I correct? How should I do this instead?

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• Do you bother to write a pretty error page?

  - by Chacha102

  So, everyone is really used to the errors that PHP gives you. They look kind of like this: Fatal error: Allowed memory size of 8388608 bytes exhausted (tried to allocate 2 bytes) in /path/to/file(437) on line 21 My question is, do you put in the time to make your error pages more useful? I find that I am able to debug a lot faster using my own error page: I find this to be a lot better than the PHP errors because it gives me a stack trace, the usual error message, along with the actual location of the error, and more. Also, are there any downsides from creating your own development error pages. Obviously you wouldn't want to have a user see this page, but what about during development?

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• Streaming large result sets with MySQL

  - by configurator

  I'm developing a spring application that uses large MySQL tables. When loading large tables, I get an OutOfMemoryException, since the driver tries to load the entire table into application memory. I tried using statement.setFetchSize(Integer.MIN_VALUE); but then every ResultSet I open hangs on close(); looking online I found that that happens because it tries loading any unread rows before closing the ResultSet, but that is not the case since I do this: ResultSet existingRecords = getTableData(tablename); try { while (existingRecords.next()) { // ... } } finally { existingRecords.close(); // this line is hanging, and there was no exception in the try clause } The hangs happen for small tables (3 rows) as well, and if I don't close the RecordSet (which happened in one method) then connection.close() hangs.

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• Getting list of all existing vtables.

  - by Patrick

  In my application I have quite some void-pointers (this is because of historical reasons, application was originally written in pure C). In one of my modules I know that the void-pointers points to instances of classes that could inherit from a known base class, but I cannot be 100% sure of it. Therefore, doing a dynamic_cast on the void-pointer might give problems. Possibly, the void-pointer even points to a plain-struct (so no vptr in the struct). I would like to investigate the first 4 bytes of the memory the void-pointer is pointing to, to see if this is the address of the valid vtable. I know this is platform, maybe even compiler-version-specific, but it could help me in moving the application forward, and getting rid of all the void-pointers over a limited time period (let's say 3 years). Is there a way to get a list of all vtables in the application, or a way to check whether a pointer points to a valid vtable, and whether that instance pointing to the vtable inherits from a known base class?

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• Table Variables in SSIS

  - by aceinthehole

  In one SQL Task can I create a table variable DELCARE @TableVar TABLE (...) Then in another SQL Task or DataSource destination and select or insert into the table variable? The other option I have considered is using a Temp Table. CREATE TABLE #TempTable (...) I would prefer to use Table Variable so that it remains in memory. But can use temp table if it is not possible to use table variable. Also I cannot use the record set destination as I need to preform straight SQL tasks on it later on.

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• Less Mathematical Approaches to Machine Learning?

  - by Ed

  Out of curiosity, I've been reading up a bit on the field of Machine Learning, and I'm surprised at the amount of computation and mathematics involved. One book I'm reading through uses advanced concepts such as Ring Theory and PDEs (note: the only thing I know about PDEs is that they use that funny looking character). This strikes me as odd considering that mathematics itself is a hard thing to "learn." Are there any branches of Machine Learning that use different approaches? I would think that a approaches relying more on logic, memory, construction of unfounded assumptions, and over-generalizations would be a better way to go, since that seems more like the way animals think. Animals don't (explicitly) calculate probabilities and statistics; at least as far as I know.

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• Is there an automatic way to remove debugging methods for a release build?

  - by Lewis

  Note: This is an extension of an earlier question I asked here: Do additional function/method definitions increase a program's memory footprint? When I write a class, I usually end up writing several testing/debugging methods, used to make sure the class works as it should, or for printing data to help with debugging, or for unit testing, etc. Is there an easy/automatic way to make a release without these methods, or do I need to manually delete the extra code any time I want to compile a release version? I ask this question both from a C++ and a Java perspective. I'm using Code::Blocks and Eclipse as IDEs, if that plays into the answer somehow.

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• Program visible to Linux as normal directory

  - by Xam

  I'm trying to write program to work as programmable directory, in other words: User, or other systems open that directory and read/write files or dirs. I try to create program to cache most used files in memory (less I/O to HDD), but right now I don't know how to achive that. There are probably some docs about this but I can't find them. I know that there is FUSE, NFS and others, but reading their source is quite difficult. If any one has info about implementation in C lang I'll be very grateful. Sorry for my English..

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• node.js storing gamestate, how?

  - by expressnoob

  I'm writing a game in javascript, and to prevent cheating, i'm having the game be played on the server (it's a board game like a more complicated checkers). Since the game is fairly complex, I need to store the gamestate in order to validate client actions. Is it possible to store the gamestate in memory? Is that smart? Should I do that? If so, how? I don't know how that would work. I can also store in redis. And that sort of thing is pretty familiar to me and requires no explanation. But if I do store in redis, the problem is that on every single move, the game would need to get the data from redis and interpret and parse that data in order to recreate the gamestate from scratch. But since moves happen very frequently this seems very stupid to me. What should I do?

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• Netbeans or Eclipse for C++?

  - by Robert Gould

  I'm currently working on a pet project and need to do C++ development on Windows, Mac, Linux, and Solaris, and I've narrowed it down to Netbeans and Eclipse, so I was wonderig which is more solid as a C++ editor. I just need solid editing, good autocompletion for templated code ad external libraries, and project file management, the build tools are external, so thats irrelevant here, for my comparison. Thus which is a better choice? Note: I know I should be using emacs or vim, but the issue is, my theory at least, that I'm left handed, so I use my right side (design,creativity) of the brain more than the left side (logic, memory), so I just simply cannot use emacs or vim, my brain simply isn't compatible, I tried them many times too, even used emacs for a few months but it drove me crazy... Thanks

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• Recognize active objects with a capacitive touch screen display

  - by lucgian84

  I'm trying to develop an app that can recognize an active object (for example: a memory) that touch the smartphone display. Before I start to develop I've to know if there's any objects that my touch screen display can recognize? Which device can be recognizable by a smartphone display? I'm interested to know that for iPhone or for Android phone. I found this app and you can see that with a card I can interact with a mobile device, now I'm asking you if anyone know how to do this kind of app with an iPhone or with an Android phone. Does anyone knows how to do that? There's a library (iOS or Android) to recognize object that I put over the display?

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• save state of external running program

  - by SuitUp

  Hi, my goal is to save state of running process and later start from this point. This is not necessary need to be state from this exact moment, let's say save after 5 seconds is good too. Problem is, i can't alter in code of this external program, i am even don't aware of it's architecture. I have resources to save whole program to disk from memory, but i need some tips, where to start. I can't use any VM like Virtual Box to save state of whole operating system, and program can be written in c++ or c or c#...

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• NULL In a Class Destructor

  - by Hyper-DarkStar

  Simple question; Is it pointless to set a pointer( which allocates heap memory ) to NULL in the destructor? class SampleClass { public: SampleClass( int Init = 0 ) { Value = new int( Init ); } ~SampleClass( void ) { delete Value; Value = NULL; // Is this pointless? } int *Value; }; While on the subject of classes, when should I use the explicit keyword? Thanks.

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• What's the reason why core data takes care of the life-cycle of modeled properties?

  - by mystify

  The docs say that I should not release any modeled property in -dealloc. For me, that feels like violating the big memory management rules. I see a big retain in the header and no -release, because Core Data seems to do it at any other time. Is it because Core Data may drop the value of a property dynamically, at any time when needed? And what's Core Data doing when dropping an managed object? If there's no -dealloc, then how and when are the properties getting freed up?

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