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  • Objects leaking immediately from allocation using either new or [[Object alloc] init];

    - by Sam
    While running Instruments to find leaks in my code, after I've loaded a file and populate an NSMutableArray with new objects, leaks pop up! I am correctly releasing the objects. Sample code below: //NSMutableArray declared as a retained property in the parent class if(!mutableArray) mutableArray = [[NSMutableArray alloc] initWithCapacity:objectCount]; else [mutableArray removeAllObjects]; //Iterates through the read in data and populate the NSMutableArray for(int i = 0; i < objectCount; i++){ //Initializes a new object with data MyObject *object = [MyObject new]; //Adds the object to the mutableArray [mutableArray addObject:object]; //Releases the object [object release]; } I get a number of leaks from Instruments terminating at the addition of the 'object' into the 'mutableArray', but also including the allocation of the 'object' and the 'mutableArray'. I don't get it. Not to mention, this is happening on the first call of the enclosing method so the allocation of the NSMutableArray is being hit in the logic block, not the 'removeAllObjects' selector. Lastly, does Core Foundation have a major bug in it that randomly creates CFStrings and mismanages their memory? My code does not even use those, nor do the leaks where they occur have anything to do with my code. Almost all of my applications so far deal with OpenGL (in case anyone knows of a threading issue that arises from trying to synch the backend of the program with the front end of displaying the contents of an NSOpenGLView class or whatever it is).

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  • When is a program limited by the memory bandwidth?

    - by hanno
    I want to know if a program that I am using and which requires a lot of memory is limited by the memory bandwidth. When do you expect this to happen? Did it ever happen to you in a real life scenario? I found several articles discussing this issue, including http://www.cs.virginia.edu/~mccalpin/papers/bandwidth/node12.html http://www.cs.virginia.edu/~mccalpin/papers/bandwidth/node13.html http://ispass.org/ucas5/session2_3_ibm.pdf The first link is a bit old, but suggests that you need to perform less than about 1-40 floating point operations per floating point variable in order to see this effect (correct me if I'm wrong). How can I measure the memory bandwidth that a given program is using and how do I measure the (peak) bandwidth that my system can offer? I don't want to discuss any complicated cache issues here. I'm only interested in the communication between the CPU and the memory.

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  • When are temporaries created as part of a function call destroyed?

    - by Michael Mrozek
    Is a temporary created as part of an argument to a function call guaranteed to stay around until the called function ends, even if the temporary isn't passed directly to the function? There's virtually no chance that was coherent, so here's an example: class A { public: A(int x) : x(x) {printf("Constructed A(%d)\n", x);} ~A() {printf("Destroyed A\n");} int x; int* y() {return &x;} }; void foo(int* bar) { printf("foo(): %d\n", *bar); } int main(int argc, char** argv) { foo(A(4).y()); } If A(4) were passed directly to foo it would definitely not be destroyed until after the foo call ended, but instead I'm calling a method on the temporary and losing any reference to it. I would instinctively think the temporary A would be destroyed before foo even starts, but testing with GCC 4.3.4 shows it isn't; the output is: Constructed A(4) foo(): 4 Destroyed A The question is, is GCC's behavior guaranteed by the spec? Or is a compiler allowed to destroy the temporary A before the call to foo, invaliding the pointer to its member I'm using?

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  • Is there memory usage profiler available?

    - by prosseek
    For time profiler for XYZ, I can just run 'time XYZ', or if I have the source code in C/C++, I even can use gprof to get profiled results. Is there any similar tool for memory usage? Is there any tool I can use something like 'memory XYZ', to get info such as min/max/median memory usage? What tool do you use for memory profile with C++/Objective C/C#/Java?

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  • Java: Best approach to have a long list of variables needed all the time without consuming memory?

    - by evilReiko
    I wrote an abstract class to contain all rules of the application because I need them almost everywhere in my application. So most of what it contains is static final variables, something like this: public abstract class appRules { public static final boolean IS_DEV = true; public static final String CLOCK_SHORT_TIME_FORMAT = "something"; public static final String CLOCK_SHORT_DATE_FORMAT = "something else"; public static final String CLOCK_FULL_FORMAT = "other thing"; public static final int USERNAME_MIN = 5; public static final int USERNAME_MAX = 16; // etc. } The class is big and contains LOTS of such variables. My Question: Isn't setting static variables means these variables are floating in memory all the time? Do you suggest insteading of having an abstract class, I have a instantiable class with non-static variables (just public final), so I instantiate the class and use the variables only when I need them. Or is what am I doing is completely wrong approach and you suggest something else?

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  • What do you do when a client ask for a feature which is a really bad idea?

    - by TAG
    Recently there was a SO question asking how to implement a feature which blocked users from copying text from a page in their browser. There were many negative comments on this feature, both because it's not practically possible to implement effectively and because it will interfere with the users' experience? What's a programmer to do in these sorts of situations in dealing with their clients or employers?

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  • Can I just release the top object (iPhone)?

    - by yar
    If I release the object that's holding a reference to the variable that I need to release, is that sufficient? Or must I release at every level of the containment hierarchy? I fear that my logic comes from working with a garbage collector for too long. For instance, I assigned to this property of a UIPickerView instance by hand instead of using IB @property(nonatomic, assign) id<UIPickerViewDelegate> delegate Since it's an assign property, I can't just release the reference after I assign it. When I finally release my UIPickerView instance, do I need to do this: [singlePicker.delegate release]; [singlePicker release]; or is the second line sufficient? Also: Are these assign properties the norm, or is that mostly for Interface Builder? I thought that retain properties were the normal thing to expect.

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  • How is an array stored in memory?

    - by George
    In an interest to delve deeper into how memory is allocated and stored, I have written an application that can scan memory address space, find a value, and write out a new value. I developed a sample application with the end goal to be able to programatically locate my array, and overwrite it with a new sequence of numbers. In this situation, I created a single dimensional array, with 5 elements, e.g. int[] array = new int[] {8,7,6,5,4}; I ran my application and searched for a sequence of the five numbers above. I was looking for any value that fell between 4 and 8, for a total of 5 numbers in a row. Unforuntately, my the sequential numbers in my array matched hundreds of results, as the numbers 4 through 8, in no particular sequence happened to be next to each other, in memory, in many situations. Is there any way to distinguish that a set of numbers within memory, represents an array, not simply integers that are next to each other? Is there any way of knowing that if I find a certain value, that the matching values proceeding it are that of an array? I would assume that when I declare int[] array, its pointing at the first address of my array, which would provide some kind of meta-data to what existed in the array, e.g. 0x123456789 meta-data, 5 - 32 bit integers 0x123456789 + 32 "8" 0x123456789 + 64 "7" 0x123456789 + 96 "6" 0x123456789 + 128 "5" 0x123456789 + 160 "4" Am I way off base?

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  • Memory interleaving

    - by Tim Green
    Hello, I have this question that has me rather confused. Suppose that a 1G x 32-bit main memory is built using 256M x 4-bit RAM chips and that this memory is byte-addressable. I have deduced that one would require 4*1G = 2^2*2*30 = 2^32 - so 32 bits to address the full memory. My problem now comes with, say, if you had memory (byte) address "14", determine which memory module this would go into. (There would have to be 8 chips per module to make the 32-bit wide memory, and 4 modules overall giving 32 chips in total. Modules are numbered from 0). In high-order interleave, it appears trivial that it's the first (0) memory module given a lot of the first few bits are 0. However, low-order interleave has me stumped. I can't figure out (for sure) how many bits are used to determine a memory module (possibly 2, given there are 4 in total?). The given solution is Module 3. This is not homework in the same sense so I will not be tagging it as such.

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  • Objective-c when to release objects

    - by Chris
    -(IBAction)registerUpdate:(id)sender { HTTPRequest* request = [[HTTPRequest alloc] initWithUrl:@"http://www.yahoo.com" delegate:self]; [request doRequest]; } The HTTPRequest makes an asynchronous request and calls the onHTTPResponse method in the current class. My question is do I have to release request? My guess is that I'm supposed to make it an instance variable? [NSString stringWithFormat:@"Data received: %@", [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding]]; How would I release that string object, or should I assign it to a variable?

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  • When to give in and start The Big Rewrite?

    - by John Cromartie
    I've had my share of projects where the first thing I think is "let's just rewrite it in ." Everybody feels the urge at some point. In fact, I think I've had the urge to rewrite pretty much every project I've ever been on. However, it is accepted wisdom that a total rewrite is generally a bad idea. The question is: when do you look at a project and say: "OK, it's time to start over." What sort of metrics or examples can you cite of where a rewrite was truly necessary? How bad does the code have to be? How old can a project get before there too much invested?

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  • C++: Unitialized variables garbage

    - by Hardware Problem
    int myInt; cout << myInt; // Garbage like 429948, etc If I output and/or work with unitialized variables in C++, what are their assumed values? Actual values in the memory from the "last user"? e.g.: Program A is closed, it had an int with the value 1234 at 0x1234 - I run my program, myInt gets the address 0x1234, I output it like above - 1234 Is it just random garbage?

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  • free( ) pointers

    - by user1043625
    I'm required to use a special library to keep track of my memory leaks where malloc()= allocate( ) and free( ) = unallocate( ). I'm trying to complete free a linked-list but it seems like the "root" value isn't being freed. typedef struct _node { struct _node *child; char *command; } Command_list; void delete_commands(Command_list **root) { Command_list *temp; while( *root != NULL ){ temp = (*root)->child; //printf("STRING: %s\n", *root->command ); unallocate( *root ); *root = temp; } } The function that's calling it void file_processing( .... ){ Command_list *root = allocate(sizeof (Command_list)); root = NULL; .... delete_commands( &root ); } } I believe that Command_list *root = allocate(sizeof (Command_list)) isn't being properly de-allocated for some reason. Anyone can give me some hints? UPDATE: I found out that instead of Command_list *root = allocate(sizeof (Command_list)); root = NULL; this works: Command_list *root = NULL;

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  • Optimize MySQL database query

    - by rajeeesh
    I had a commenting application in my web site. The comments will store in a MySQL table . table structure as follows id | Comment | user | created_date ------------------------------------------------------ 12 | comment he | 1245 | 2012-03-30 12:15:00 ------------------------------------------------------ I need to run a query for listing all the comments after a specific time. ie .. a query like this SELECT * FROM comments WHERE created_date > "2012-03-29 12:15:00" ORDER BY created_date DESC Its working fine.. My question is if I got a 1-2 lakh entry in this table is this query is sufficient for the purpose ? or this query will take time to execute ? In most cases I have to show last 2 days data + periodically ( interval of 10 mins ) checking for updates with ajax from this table ... Please help Thanks

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  • PHP - Setting Database Info

    - by user1710648
    First off, I'm sorry if this shows no code which is not what Stack Overflow is about..But I have no clue where to go on this. I have a basic CMS I made, and I am trying to distribute it. I want to make it so that upon going to /cms/install for example, they set the database info, and different info to integrate into the CMS. Now my issue is, what would be the best method to allow the user to store that database info? A cookie seems to not be the right way..Could I store database info inside of a database? Not too sure where to go on this. More or less. What is the best way to temporarily store the database information the user gave before arrival of the full CMS.

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  • Project manager programming background

    - by Henryk Konsek
    Do you think that project manager should have programming background? Do you consider this role as a natural way of evolution for the skilled/leader programmers (as an alternative for architect role)? Or maybe you believe that PM should be just a good manager with a basic understanding of the programming concepts and a fundamental knowledge about the technology you use. What is your experience with working with both kinds of managers (ex-programmers or just managers).

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  • Allocating 32-bit integer arrays in 64-bit machines

    - by Shredderroy
    I have a 64-bit i7 machine. Suppose I allocate memory for n 32-bit integers. How many physical registers will actually be used in the allocation: n, or n/2? I tried to write the following simple programme to find out. #include <iostream> #include <cstdlib> using namespace std; int main (int argc, char *argv[]) { int a[4]; cout << &a[0] << "\t" << &a[3] << endl; cin.ignore (1); return 0; } // End main () The output is: 0018FA04 0018FA10 They seem further apart than they should be. Why aren't the addresses 04 and 07? And does this mean that the system is actually allocating four (or more) integers, instead of packing the four 32-bit integers into two 64-bit registers? Thanks in advance for your help.

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  • Allocate from buffer in C

    - by Grimless
    I am building a simple particle system and want to use a single array buffer of structs to manage my particles. That said, I can't find a C function that allows me to malloc() and free() from an arbitrary buffer. Here is some pseudocode to show my intent: Particle* particles = (Particle*) malloc( sizeof(Particle) * numParticles ); Particle* firstParticle = <buffer_alloc>( particles ); initialize_particle( firstParticle ); // ... Some more stuff if (firstParticle->life < 0) <buffer_free>( firstParticle ); // @ program's end free(particles); Where <buffer_alloc> and <buffer_free> are functions that allocate and free memory chunks from arbitrary pointers (possibly with additional metadata such as buffer length, etc.). Do such functions exist and/or is there a better way to do this? Thank you!

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  • Separate "include" and "src" folders for application-level code?

    - by StackedCrooked
    This questions concerns mostly Unix/Linux style C++ development. I see that many C++ libraries store their header files in a "include" folder and source files in an "src" folder. For the sake of conformance I adopted this in my own code. But it is not clear to me whether this should be done for application code as well. I've seen a few cases where a flat directory structure is used for that. What would be the recommended approach?

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  • AS3/AIR: Managing Run-Time Image Data

    - by grey
    I'm developing a game with AS3 and AIR. I will have a large-ish quantity of images that I need to load for display elements. It would be nice not to embed all of the images that the game needs, thereby avoiding having them all in memory at once. That's okay in smaller projects, but doesn't make sense here. I'm curious about strategies for loading images during run time. Since all of the files are quite small and local ( in my current project ) loading them on request might be the best solution, but I'd like to hear what ideas people have for managing this. For bonus points, I'm also curious about solutions for loading images on-demand server-side as well.

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  • How can pointers to functions point to something that doesn't exist in memory yet? Why do prototypes have different addresses?

    - by Kacy Raye
    To my knowledge, functions do not get added to the stack until run-time after they are called in the main function. So how can a pointer to a function have a function's memory address if it doesn't exist in memory? For example: using namespace std; #include <iostream> void func() { } int main() { void (*ptr)() = func; cout << reinterpret_cast<void*>(ptr) << endl; //prints 0x8048644 even though func never gets added to the stack } Also, this next question is a little less important to me, so if you only know the answer to my first question, then that is fine. But anyway, why does the value of the pointer ( the memory address of the function ) differ when I declare a function prototype and implement the function after main? In the first example, it printed out 0x8048644 no matter how many times I ran the program. In the next example, it printed out 0x8048680 no matter how many times I ran the program. For example: using namespace std; #include <iostream> void func(); int main() { void ( *ptr )() = func; cout << reinterpret_cast<void*>(ptr) << endl; } void func(){ }

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