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  • Could I ever want to access the address zero?

    - by Joel
    The constant 0 is used as the null pointer in C and C++. But as in http://stackoverflow.com/questions/2389251/pointer-to-a-specific-fixed-address there seems to be some possible use of assigning fixed addresses. Is there ever any conceivable need, in any system, for whatever low level task, for accessing the address 0? If there is, how is that solved with 0 being the null pointer and all? If not, what makes it certain that there is not such a need?

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  • Implementing Barrier system solution in C or C++

    - by hardikpatel172
    Actually I have been assigned to implement Barrier system solution in either C or C++ programming language... But I have zero knowledge about it ... I know the problem as well as solution theoritically.. But I have no idea how to implement it.... How can it be possible in C++ to stop or run or wait any process.... Plz yaar... Anyone help me... It's urgent...

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  • Big time Leaking in Objective-C Category

    - by Daniel Amitay
    I created a custom NSString Category which lets me find all strings between two other strings. I'm now running into the problem of finding that there are a lot of kBs leaking from my script. Please see code below: #import "MyStringBetween.h" @implementation NSString (MyStringBetween) -(NSArray *)mystringBetween:(NSString *)aString and:(NSString *)bString; { NSAutoreleasePool *autoreleasepool = [[NSAutoreleasePool alloc] init]; NSArray *firstlist = [self componentsSeparatedByString:bString]; NSMutableArray *finalArray = [[NSMutableArray alloc] init]; for (int y = 0; y < firstlist.count - 1 ; y++) { NSString *firstObject = [firstlist objectAtIndex:y]; NSMutableArray *secondlist = [firstObject componentsSeparatedByString:aString]; if(secondlist.count > 1){ [finalArray addObject:[secondlist objectAtIndex:secondlist.count - 1]]; } } [autoreleasepool release]; return finalArray; } @end I admit that I'm not super good at releasing objects, but I had believed that the NSAutoreleasePool handled things for me. The line that is leaking: NSMutableArray *secondlist = [firstObject componentsSeparatedByString:aString]; Manually releasing secondlist raises an exception. Thanks in advance!

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  • Released object crashes app

    - by John Smith
    I am using objective-C++ (+Boost) for iPhone development. I am in a rather tight loop and need to allocate and release a certain object. The code is something like this. for (int i=0;i<100;i++) { opt = [[FObj alloc] init]; //do stuff with opt [opt release]; } The FObj object is something like @interface FObj MyCPPObj * cppobj; @end In the implementation of FObj there is a dealloc method: -(void) dealloc { delete cppobj; //previously allocated with 'new' [super dealloc]; } I am afraid that if i don't release then the 'MyCPPObj's will just pile up. But releasing makes the app crash after the first loop. What am I doing wrong? Or perhaps should I make cppobj and boost::shared_ptr? (do boost shared pointers automatically release their objects when an objective-C++ object is deleted?)

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  • What collection object is appropriate for fixed ordering of values?

    - by makerofthings7
    Scenario: I am tracking several performance counters and have a CounterDescription[] correlate to DataSnapshot[]... where CounterDescription[n] describes the data loaded within DataSnapshot[n]. I want to expose an easy to use API within C# that will allow for the easy and efficient expansion of the arrays. For example CounterDescription[0] = Humidity; DataSnapshot[0] = .9; CounterDescription[1] = Temp; DataSnapshot[1] = 63; My upload object is defined like this: Note how my intent is to correlate many Datasnapshots with a dattime reference, and using the offset of the data to refer to its meaning. This was determined to be the most efficient way to store the data on the back-end, and has now reflected itself into the following structure: public class myDataObject { [DataMember] public SortedDictionary<DateTime, float[]> Pages { get; set; } /// <summary> /// An array that identifies what each position in the array is supposed to be /// </summary> [DataMember] public CounterDescription[] Counters { get; set; } } I will need to expand each of these arrays (float[] and CounterDescription[] ), but whatever data already exists must stay in that relative offset. Which .NET objects support this? I think Array[] , LinkedList<t>, and List<t> Are able to keep the data fixed in the right locations. What do you think?

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  • C#. Struct design. Why 16 byte is recommended size?

    - by maxima120
    I read Cwalina book (recommendations on development and design of .NET apps). He says that good designed struct has to be less than 16 bytes in size (for performance purpose). My questions is - why exactly is this? And (more important) can I have larger struct with same efficiency if I run my .NET 3.5 (soon to be .NET 4.0) 64-bit application on i7 under Win7 x64 (is this limitation CPU / OS based)? Just to stress again - I need as efficient struct as it is possible. I try to keep it in stack all the time, the application is heavily multi-threaded and runs on sub-millisecond intervals, the current size of the struct is 64 byte.

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  • Can I use MFC objects in STL containers?

    - by Jesse Stimpson
    The following code doesn't compile for me in MSVC2005: std::vector<CMenu> vec(10); CMenu is an MFC menu object (such as a context menu). Through some testing I learned that CMenu does not have a public copy constructor. To do what I wanted to do, I needed to use a dynamic array. CMenu* menus = new CMenu[10]; // ... delete [] menus; Of course, now I've lost all the benefits of using an STL container. Do I have any other options?

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  • NSMutableArray accessing issue.

    - by Danegraphics
    I've searched and have no answer. I've created an NSMutableArray and am getting an EXC_BAD_ACCESS error in one place of access. Here. This is declaring in the .h file: NSMutableArray *buttons; ... @property (nonatomic, retain)NSMutableArray *buttons; And this is the synthesizing and implimenting: @synthesize buttons; ... - (id)init { self = [super init]; if(self != nil) { buttons = [[NSMutableArray alloc] init]; } return self; } ... -(void)addButtonWithImage:(Image*)image { Image *button = image; [buttons addObject:button]; [button release]; } ... -(void)replaceButtonAt:(int)num with:(Image*)image { Image *button = image; [buttons replaceObjectAtIndex:num withObject:button]; <<===EXC_BAD_ACCESS [button release]; } But when I use this: -(void)renderButton:(int)num atPoint:(CGPoint)point center:(BOOL)center{ Image *button = [buttons objectAtIndex:num]; [button renderAtPoint:point centerOfImage:center]; } It works

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  • Developing Bots__Where can I start?

    - by user947659
    i have a pet programming goal: to develop a bot for a game. Now, this won't be anything malicious, and I just want to do this to further my knowledge in programming. Can anyone help me out by pointing to where i can start learning how to develop a bot? the type of bots i want to make are video game bots (online multiplayer, first person shooters, and offline games(like solitaire and such)). Thanks!

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  • Release resources in .Net C#

    - by zaidwaqi
    Hi, I'm new to C# and .NET, ,and have been reading around about it. I need to know why and when do I need to release resources? Doesn't the garbage collector take care of everything? When do I need to implement IDisposable, and how is it different from destructor in C++? Also, if my program is rather small i.e. a screensaver, do I need to care about releasing resources? Thanks.

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  • Can I catch bad pointer errors in C++?

    - by Simon
    Hi there, I was wondering if there is a possibility to catch errors like this in C++: object* p = new object; delete p; delete p; //this would cause an error, can I catch this? Can I check if the pointer is valid? Can I catch some exception? I know I could set the pointer p to NULL after the first object deletion. But just imagine you wouldn't do that. I am using VC++ with Visual Studio 2008/2010. Thank you

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  • Iphone release problem

    - by xger86x
    Hi, i have the following code in a .h @property (nonatomic, copy) NSString *username; Then, username is assigned in this way when the user enter text in a TextField: self.username = textField.text; And then, in dealloc method i call release: NSLog(@"%d",[username retainCount]); [username release]; NSLog(@"%d",[username retainCount]); But in the console it prints: 2011-01-11 23:09:52.468 IApp[2527:307] 1 2011-01-11 23:09:52.480 IApp[2527:307] 1 What is the problem? Thanks

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  • Why is the Java VM so popular?

    - by sdudo
    There are more and more programming languages (Scala, Clojure,...) coming out that are made for the Java VM and are therefore compatible with the Java Byte-Code. I'm beginning to ask myself: Why the Java VM? What makes it so powerful or popular that there are new programming languages, which seem gaining popularity too, created for it? Why don't they write a new VM for a new language?

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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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  • Will this be garbage collected in JVM?

    - by stjowa
    I am running the following code every two minutes via a Timer: object = new Object(this); Potentially, this is a lot of objects being created and a lot of objects being overwritten. Do the overwritten objects get garbage collected, even with a reference to itself being used in the newly created object? I am using JDK 1.6.0_13. Thanks for the help.

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  • What does CPU Time consist of? [closed]

    - by Sid
    What does CPU time exactly consist of? For instance, is the time taken to access a page from the RAM (at which point, the CPU is most likely idling) part of the CPU time? I'm not talking about fetching the page from the disk here, just fetching it from the RAM. Thanks

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  • Using std::bad_alloc for C pointers

    - by otibom
    I'm using a library written in C in a C++ project. I'd like to use C++ exceptions to handle C errors. In particular, it would be nice to have an exception thrown if an allocation fails. I can do this in constructors of classes which hold C-style pointers to C structs : if (c_object == NULL) throw std::bad_alloc(); But if the class is responsible for several C objects they are no ways of free-ing all already allocated pointers since the destructor isn't called. I have a feeling I could use smart-pointers, but I don't have much experience with them. What's more, I have to have access to the original C pointers to use the C api properly. Is there an elegant solution to this ?

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  • Should repeated use of the camera crash an app?

    - by Sam
    I have an app that builds a slideshow from user images. They can grab from their library or take a picture. I have found that repeated use of grabbing an image from the library is fine. But repeated use of taking a picture causes erratic behavior. I have been getting crashes but mostly what happens seems to be a reloading of the view after "didFinishPickingMediaWithInfo", which messes things up. I have no leaks and it seems to be releasing properly after each picture is taken. I am resizing the image and saving it in a data base. Is anyone else running into this situation? Was the camera not designed to be called this often?

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  • Linking to a Large address aware DLL.

    - by Canopus
    Suppose I have a DLL which is built with LARGEADDRESSAWARE linker flag set. Now I have an application dynamically linking to this DLL. Does this make my application LARGEADDRESSAWARE? If not then, does it make sense to have this flag set for any DLL?

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  • How much RAM used by Python dict or list?

    - by Who8MyLunch
    My problem: I am writing a simple Python tool to help me visualize my data as a function of many parameters. Each change in parameters involves a non-trivial amount of time, so I would like to cache each step's resulting imagery and supporting data in a dictionary. But then I worry that this dictionary could grow too large over time. Most of my data is in the form of Numpy arrays. My question: How would one go about computing the total number of bytes used by a Python dictionary. The dictionary itself may contain lists and other dictionaries, each of which contain data stored in Numpy arrays. Ideas?

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  • C#: How to implement a smart cache

    - by Svish
    I have some places where implementing some sort of cache might be useful. For example in cases of doing resource lookups based on custom strings, finding names of properties using reflection, or to have only one PropertyChangedEventArgs per property name. A simple example of the last one: public static class Cache { private static Dictionary<string, PropertyChangedEventArgs> cache; static Cache() { cache = new Dictionary<string, PropertyChangedEventArgs>(); } public static PropertyChangedEventArgs GetPropertyChangedEventArgsa(string propertyName) { if (cache.ContainsKey(propertyName)) return cache[propertyName]; return cache[propertyName] = new PropertyChangedEventArgs(propertyName); } } But, will this work well? For example if we had a whole load of different propertyNames, that would mean we would end up with a huge cache sitting there never being garbage collected or anything. I'm imagining if what is cached are larger values and if the application is a long-running one, this might end up as kind of a problem... or what do you think? How should a good cache be implemented? Is this one good enough for most purposes? Any examples of some nice cache implementations that are not too hard to understand or way too complex to implement?

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