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  • Problem intialising 2D array

    - by TeeJay
    Ok, so I have a 2D Array that is initialised with values from a file (format: x y z). My file reads in the values correctly but when adding the z value to the matrix/2DArray, I run into a segfault and I have no idea why. It is possibly incorrect use of pointers? I still don't quite have the hang of them yet. This is my intialiser, works fine, even intialises all "z" values to 0. int** make2DArray(int rows, int columns) { int** newArray; newArray = (int**)malloc(rows*sizeof(int*)); if (newArray == NULL) { printf("out of memory for newArray.\n"); } for (int i = 0; i < rows; i++) { newArray[i] = (int*)malloc(columns*sizeof(int)); if (newArray[i] == NULL) { printf("out of memory for newArray[%d].\n", i); } } //intialise all values to 0 for (int i = 0; i < rows; i++) { for (int j = 0; j < columns; j++) { newArray[i][j] = 0; } } return newArray; } This is how I call the initialiser (and problem function). int** map = make2DArray(rows, columns); fillMatrix(&map, mapFile); And this is the problem code. void fillMatrix(int*** inMatrix, FILE* inFile) { int x, y, z; char line[100]; while(fgets(line, sizeof(line), inFile) != NULL) { sscanf(line, "%d %d %d", &x, &y, &z); *inMatrix[x][y] = z; } } From what I can gather through the use of ddd, the problem comes when y gets to 47. The map file has a max "x" value of 47 and a max "y" value of 63, I'm pretty sure I haven't got the order mixed up, so I don't know why the program is segfault-ing? I'm sure it's some newbie mistake...

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  • How to get the type of the class for comparison

    - by Halo
    I have this object which is an instance of a superclass. I want to know which subclass that object really is, so that I can decide what to do with it. There is this getClass() method but it's apparently not used for comparison issues. How can I get the sub-type of my object?

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  • When is `x IS NOT NULL` not the same as `NOT(x IS NULL)`

    - by Mark Hurd
    For what x is The expression x IS NOT NULL is not equal to NOT(x IS NULL), as is the case in 2VL (quote from this answer, which is quoting Fabian Pascal Practical Issues in Database Management - A Reference for the Thinking Practitioner -- near the end of that answer) My guess is when x IS NULL is NULL, but I cannot guess when that would be (i.e. I haven't checked the SQL standard).

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  • Alias for a C++ template?

    - by porgarmingduod
    typedef boost::interprocess::managed_shared_memory::segment_manager segment_manager_t; // Works fine, segment_manager is a class typedef boost::interprocess::adaptive_pool allocator_t; // Can't do this, adaptive_pool is a template The idea is that if I want to switch between boost interprocess' several different options for shared memory and allocators, I just modify the typedefs. Unfortunately the allocators are templates, so I can't typedef the allocator I want to use. Is there a way to achieve an alias to a template in C++? (Except for the obvious #define ALLOCATOR_T boost::interprocess::adaptive_pool)

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  • Viewing large XML files in eclipse?

    - by Paul Wicks
    I'm working on a project involving some large XML files (from 50MB to over 1GB) and it would be nice if I could view them in eclipse (simple text view is fine) without Java running out of heap space. I've tried tweaking the amount of memory available to the jvm in eclipse.ini but haven't had much success. Any ideas?

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  • Inlining an array of non-default constructible objects in a C++ class

    - by porgarmingduod
    C++ doesn't allow a class containing an array of items that are not default constructible: class Gordian { public: int member; Gordian(int must_have_variable) : member(must_have_variable) {} }; class Knot { Gordian* pointer_array[8]; // Sure, this works. Gordian inlined_array[8]; // Won't compile. Can't be initialized. }; As even beginner C++ users know, the language guarantees that all members are initialized when constructing a class. And it doesn't trust the user to initialize everything in the constructor - one has to provide valid arguments to the constructors of all members before the body of the constructor even starts. Generally, that's a great idea as far as I'm concerned, but I've come across a situation where it would be a lot easier if I could actually have an array of non-default constructible objects. The obvious solution: Have an array of pointers to the objects. This is not optimal in my case, as I am using shared memory. It would force me to do extra allocation from an already contended resource (that is, the shared memory). The entire reason I want to have the array inlined in the object is to reduce the number of allocations. This is a situation where I would be willing to use a hack, even an ugly one, provided it works. One possible hack I am thinking about would be: class Knot { public: struct dummy { char padding[sizeof(Gordian)]; }; dummy inlined_array[8]; Gordian* get(int index) { return reinterpret_cast<Gordian*>(&inlined_array[index]); } Knot() { for (int x = 0; x != 8; x++) { new (get(x)) Gordian(x*x); } } }; Sure, it compiles, but I'm not exactly an experienced C++ programmer. That is, I couldn't possibly trust my hacks less. So, the questions: 1) Does the hack I came up with seem workable? What are the issues? (I'm mainly concerned with C++0x on newer versions of GCC). 2) Is there a better way to inline an array of non-default constructible objects in a class?

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  • Enterprise Library Review?

    Hi, Is enterprise library for exception handling and logging efficient in terms of its memory usage for the functionality provided? What are the pros and cons? Thanks

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  • JavaScript: How can I determine what objects are being collected by the garbage collector?

    - by shino
    I have significant garbage collection pauses. I'd like to pinpoint the objects most responsible for this collection before I try to fix the problem. I've looked at the heap snapshot on Chrome, but (correct me if I am wrong) I cannot seem to find any indicator of what is being collected, only what is taking up the most memory. Is there a way to answer this empirically, or am I limited to educated guesses?

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  • Is it a good practice to always use smart pointers ?

    - by Dony Borris
    Hi, I find smart pointers to be a lot more comfortable than raw pointers. So is it a good idea to always use smart pointers? ( Please note that I am from Java background and hence don't much like the idea of explicit memory management. So unless there are some serious performance issues with smart pointers, I'd like to stick with them. ) Any advice would be greatly appreciated. Thanks.

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  • How to format date from string?

    - by 4thSpace
    I have a string with this value: 2010-05-13 23:17:29 I'd like to format it and am using the following code: NSDateFormatter *formatter = [[NSDateFormatter alloc] init]; formatter.dateStyle = NSDateFormatterMediumStyle; NSDate *formattedDate = [formatter dateFromString:dateString]; [formatter release]; When the debugger reaches the release line, formattedDate shows "invalid CFStringRef" and Cannot access memory at address 0x0 Any ideas what I'm doing wrong?

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  • Object Oriented vs Relational Databases

    - by Dan
    Objects oriented databases seem like a really cool idea to me, no need to worry about mapping your domain model to your database model, no messing around with sql or ORM tools. The way I understand it, relational DBs offer some advantages when there is massive amounts of data, and searching an indexing need to be done. To my mind 99% of websites are not massive, and enterprise issues never need to be thought about, so why arn't OO DBs more widely used?

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  • Target Framework Mismatch

    - by Si Keep
    When adding a reference to a project I sometimes see the message... "The Target Framework version for the project is higher than the current project Target Framework version. Would you like to add this reference to your project anyway?" I understand what the message is indicating but can anyone explain what issues might arise from saying 'Yes'?

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  • string or nsstring with string

    - by joels
    Lets assume myProp is @property (retain) NSString * myProp and synthesized for us.... self.myProp = @"some value";//string literal? self.myProp = [NSString stringWithString:@"some value"]; Is there a difference here? Is the first one a string literal that doesnt get autoreleased or is it just in memory for it's current scope and I dont have to worry about it?

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  • Destructors in C++

    - by user265260
    does the Destructor deallocate memory assigned to the object which it belongs to or is it just called so that it can perform some last minute housekeeping before the object os deallocated by the compiler?

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