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  • C Programming: calling free() on error?

    - by kouei
    Hi all, This a follow up on my previous question. link here. My question is: Let's say I have the following code.. char* buf = (char*) malloc(1024); ... for(; i<20; i++) { if(read(fd, buf, 1024) == -1) { // read off a file and store in buffer perror("read failed"); return 1; } ... } free(buf); what i'm trying to get at is that - what if an error occurs at read()? does that mean my allocated memory never gets freed? If that's the case, how do I handle this? Should I be calling free() as part of error handling? Once again, I apologize for the bad English. ^^; Many thanks, K.

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  • How do I write Push and Pop in Scheme?

    - by kunjaan
    Right now I have (define (push x a-list) (set! a-list (cons a-list x))) (define (pop a-list) (let ((result (first a-list))) (set! a-list (rest a-list)) result)) But I get this result: Welcome to DrScheme, version 4.2 [3m]. Language: Module; memory limit: 256 megabytes. > (define my-list (list 1 2 3)) > (push 4 my-list) > my-list (1 2 3) > (pop my-list) 1 > my-list (1 2 3) What am I doing wrong? Is there a better way to write push so that the element is added at the end and pop so that the element gets deleted from the first?

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  • Excel workbooks produced by POI don't work when linked

    - by Eric Nicolas
    Here is what I'm doing : Create a workbook in memory (book = new HSSFWorkbook(), ...) Save it to disk (book.write(...)) Open in Excel (ok) Create another workbook in Excel, which links to the first one (=PoiWorkbook?xls!A1) Close Excel Then everytime I open the second workbook again, all the links are #N/A, unless I also open the POI-generated workbook at the same time. I never saw this behaviour with standard workbooks created in Excel. Anyone has seen this and found a workaround ? Thanks.

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  • Could someone give me their two cents on this optimization strategy

    - by jimstandard
    Background: I am writing a matching script in python that will match records of a transaction in one database to names of customers in another database. The complexity is that names are not unique and can be represented multiple different ways from transaction to transaction. Rather than doing multiple queries on the database (which is pretty slow) would it be faster to get all of the records where the last name (which in this case we will say never changes) is "Smith" and then have all of those records loaded into memory as you go though each looking for matches for a specific "John Smith" using various data points. Would this be faster, is it feasible in python, and if so does anyone have any recommendations for how to do it?

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  • how to generate large image in compact framework

    - by Buthrakaur
    I need to generate large images (A4 image at 200 DPI, PNG format would be fine) in my compact framework application. This is impossible to do in standard way due to memory limitations (such big image will throw OOMException). Is there any library which offers file-backed stream image generation? Or I could generate many smaller stripes of images (each stripe representing a row of the large image) using standard Bitmap approach, but I need to merge them together afterwards - is there any method how to merge many smaller images into one large without having to instantiate large Bitmap instance (which would again cause OOM)?

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  • Application disappears after starting - C++ linking managed code dll

    - by Axarydax
    Hello, we have a problem with our applications. We have recently upgraded our toolchain to Visual Studio 2010 and friends, it all works fine on Windows Vista + Windows 7 developer machines and Windows 7 customer machines. (all x86) Today we did a first installation to a client PC running Windows XP SP3 x86, and all applications linking managed code dll do not work. After starting the .exe seemingly nothing happens, no window pops up, no memory gets eaten, no task shows in task manager, nothing, nada. Event log is empty, everything is just as if the application returned to the OS right after the start. I am at loss about this, I really don't know how should I start even debugging this problem. I don't want to install VS2010 and everything onto a Windows XP box, I'd like to try something less time intensive first. This all is happening just to native C++ apps that link managed c++ DLL. Pure managed C# apps do work. Pure native C++ apps do work.

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  • Forcing a templated object to construct from a pointer

    - by SalamiArmi
    I have a fictional class: template<typename T> class demonstration { public: demonstration(){} ... T *m_data; } At some point in the program's execution, I want to set m_data to a big block of allocated memory and construct an object T there. At the moment, I've been using this code: void construct() { *m_data = T(); } Which I've now realised is probably not the best idea... wont work under certain cirumstances, if T has a private assignment operator for example. Is there a normal/better way to do what I'm attempting here?

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  • linux's fork and system resources

    - by Dmitry Bespalov
    Suppose I have following code in linux: int main() { FILE* f = fopen("file.txt", "w"); fork(); fwrite("A", 1, 1, f); fclose(f); return 0; } What I know about fork from documentation, is that it makes the copy of current process. It copies state of the memory as well, so *f should be equal in both instances. But what happens with system resources, such as a file handle? In this example I open the file with write intentions, so only one instance can write into file, right? Which of the instances will actually write into file? Who should care further about the file handle, and call fclose() ?

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  • Objective-C: Initializing char with char at index of string.

    - by Mr. McPepperNuts
    unichar myChar = [myString characterAtIndex:0]; [myNSMutableArray addObject:myChar]; I am trying to insert the first char of a string into an array, to create an array of chars. the first line does not give me an error. The second line however, provides the following error: warning: passing argument 1 of 'addObject:' makes pointer from integer without a cast This also crashes the application with a "bad address" error. I thought this error was due to a problem with memory allocation. Can someone shed some light on this.

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  • Detect movie being played (Windows)

    - by modosansreves
    Watching a movie is quite a different user activity. User doesn't touch neither mouse nor keyboard. Yet he 'actively' uses the computer. Thus, screensaver shouldn't run, indexing should be performed with care etc. On the other side, playing video requires either using direct write to video memory, or DirectShow, or some other API. This may be the key to the answer. What is the Dead Simple Way to determine that a video is being played?

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  • Easiest way to combine a dataset and other data in a single file?

    - by Tim Gradwell
    I have a dataset in C# which I can serialise using dataset.WriteXml(filename); but I want the file to contain other data as well (essentially some meta data about the dataset). I could add another table to the dataset which contained the metadata, but I'd prefer to keep it separate, if at all possible. Essentially I think I want to create a 'combination of files' file, that looks something like this: size_of_file1 file1 size_of_file2 file2 ... etc Then, I'd like to load the file into memory, and split the file into separate streams, so that I can feed the dataset into dataset.ReadXml(stream); and the metadata into something else. Sound possible? Can anyone tell me how I can do it? Thanks Tim

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  • Writing a PHP web crawler using cron

    - by Horse
    Hi all I have written myself a web crawler using simplehtmldom, and have got the crawl process working quite nicely. It crawls the start page, adds all links into a database table, sets a session pointer, and meta refreshes the page to carry onto the next page. That keeps going until it runs out of links That works fine however obviously the crawl time for larger websites is pretty tedious. I wanted to be able to speed things up a bit though, and possibly make it a cron job. Any ideas on making it as quick and efficient as possible other than setting the memory limit / execution time higher?

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  • How to create a NSAutoreleasePool without Objective-C?

    - by fbafelipe
    I have multiplatform game written in C++. In the mac version, even though I do not have any obj-c code, one of the libraries I use seems to be auto-releasing stuff, and I get memory leaks for that, since I did not create a NSAutoreleasePool. What I want is to be able to create (and destroy) a NSAutoreleasePool without using obj-c code, so I don't need to create a .m file, and change my build scripts just for that. Is that possible? How can that be done? OBS: Tagged C and C++, because a solution in any of those languages will do.

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  • C++ containers on classes, returning pointers

    - by otneil
    Hello, I'm having some trouble to find the best way to accomplish what I have in mind due to my inexperience. I have a class where I need to a vector of objects. So my first question will be: is there any problem having this: vector< AnyType container* and then on the constructor initialize it with new (and deleting it on the destructor)? Another question is: if this vector is going to store objects, shouldn't it be more like vector< AnyTipe* so they could be dynamically created? In that case how would I return an object from a method and how to avoid memory leaks (trying to use only STL)?

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  • C++ is there a difference between assignment inside a pass by value and pass by reference function?

    - by Rémy DAVID
    Is there a difference between foo and bar: class A { Object __o; void foo(Object& o) { __o = o; } void bar(Object o) { __o = o; } } As I understand it, foo performs no copy operation on object o when it is called, and one copy operation for assignment. Bar performs one copy operation on object o when it is called and another one for assignment. So I can more or less say that foo uses 2 times less memory than bar (if o is big enough). Is that correct ? Is it possible that the compiler optimises the bar function to perform only one copy operation on o ? i.e. makes __o pointing on the local copy of argument o instead of creating a new copy?

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  • How to create a new IDA project based on an existing one with different offsets?

    - by tbergelt
    I have an existing IDA Pro project for a C166 processor embedded application. This project already has many functions, variables, etc defined. There are different versions of the embedded application I am looking at. The different versions of the application are 99% the same, but with slight variations in code and data that cause functions and variables to be at different memory offsets. I want to create a new IDA project for a different version of the application. I would like to somehow import all of my function and variable definitions from my existing IDA project. I would like IDA to recognize the signatures of the existing function definitions and define them at there new location in the new project. How can I do this? Are there certain plugins for IDA I can chain together?

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  • Is it faster to use a complicated boolean to limit a ResultSet at the MySQL end or at the Java end?

    - by javanix
    Lets say I have a really big table filled with lots of data (say, enough not to fit comfortably in memory), and I want to analyze a subset of the rows. Is it generally faster to do: SELECT (column1, column2, ... , columnN) FROM table WHERE (some complicated boolean clause); and then use the ResultSet, or is it faster to do: SELECT (column1, column2, ... , columnN) FROM table; and then iterate over the ResultSet, accepting different rows based on a java version of your boolean condition? I think it comes down to whether the Java iterator/boolean evaluator is faster than the MySQL boolean evaluator.

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  • [CA_COLOR_OPAQUE] things that make a layer non-opaque. scaled CAGradientLayer?

    - by mahal tertin
    i spent some time with the environment variable CA_COLOR_OPAQUE = 1 and have my findings to share. things that make a CALayer non-opaque (slow, more memory, ...): * contents with alpha (like an NSImage with an icon) * NSImage/CGImage from a pdf as contents (even when the pdf does not contain any alpha and opaque=YES) * backgroundColor = nil * CATextLayer with text in a (because it is contents with alpha) * rounded corners? maybe/sometimes * masksToBounds? not necessarily as we scale most of tree with CATransform3DScale on sublayerTransform i found also these rather irritating non-opaque: * CAGradientLayer that is somewhere down in this scaled tree (even when set all the gradient colors without alpha) * edgeAntialiasingMask != 0 of a layer that is somewhere down in this scaled tree the last two do not make sense to me. why should it be non opaque? what do i see? if anyone has any thoughts on these findings, i'm happy to learn as i couldn't find such a list yet.

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  • Quick way to do data lookup in PHP

    - by Ghostrider
    I have a data table with 600,000 records that is around 25 megabytes large. It is indexed by a 4 byte key. Is there a way to find a row in such dataset quickly with PHP without resorting to MySQL? The website in question is mostly static with minor PHP code and no database dependencies and therefore fast. I would like to add this data without having to use MySQL if possible. In C++ I would memory map the file and do a binary search in it. Is there a way to do something similar in PHP?

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  • Freeing JavaScript object

    - by pion
    I am looking at the example from http://www.javascriptkit.com/javatutors/oopjs.shtml var person = new Object() person.name = "Tim Scarfe" person.height = "6Ft" But there is no mention how to "free" it in order to avoid memory leak. Will the following code free it? person = null; How do you free a JavaScript Object using "new Object()? How do you free a JavaScript Array allocated using "new Array(10)"? How do you free a JavaScript JSON allocated using "var json = {"width": 480, "height": 640}"? Thanks in advance for your help.

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  • Book resources for x86/x64 assembly programming on Win platform

    - by Scott Davies
    Hello, I ran a search for assembly language resources on stackoverflow.com and found some interesting results, but they seemed to boil down to two groups: 1) Assembly references to old ia32 architecture, such as the 80386 to Pentium 2) Windows agnostic books. Most of the commenters make the point that assembler is CPU dependent and that the OS is irrelevant, but it seems pointless to me to pick a book that has assembly examples that refer to MS-DOS interrupts and memory layouts. Likewise, learning assembler on Linux would seem to produce Linux executables Are there any: 1) Modern 2) x86/x64 3) on Windows platform - book resources available ? The reason I am targeting the Win platform is I would like to do low-level, OS internals programming, to supplement my Win C/C++ work. Thanks

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  • Problem with running a program from flashdrive

    - by rajivpradeep
    I have a USB drive with two partitions in it, one hidden and one normal. I have an application which swaps the memory and runs the flash application in hidden zone. The problem is that the application works fine on Windows 7 and when run on Win XP, it swaps the partitions but doesn't run the flash applications but just keeps running in the background. I can see it in task manager. But, when I copy the application to desktop and run, it runs with no glitch. I was facing the same problem on Win 7 too, but it was running as required when I ran it using "Run in XP mode" and then I applied a SHIM and is running since then as required. The application is built using VC++ 2008. does anyone know the solution?

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  • segmentation fault

    - by gcc
    int num_arrays; char *p[20]; char tempc; int i=0; do { p[i]=malloc(sizeof(int)); scanf("%s",p[i]); tempc=p[i]; ++i; }while(tempc=='x'); num_arrays=atoi(p[0]); When i write num_arrays=atoi(..),gcc give me segmentation fault or memory stack is exceeded, I don't understand why it behaves like that can anyone explain, why?

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  • Why does UITableViewCell have a contentView property?

    - by mystify
    What's the point of this contentView property? I mean: Why aren't all the subviews just added to self? Let me get that right: Every cell is a view (UITabvleViewCell is a UIView subclass). And this fat view has another fat view with same bounds sitting on top of it, called contentView. That contentView then carries all those other subviews. Now why didn't they save that extra chunk of memory? Is there any genius logic behind this decision? Would love to understand the reason for this.

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  • Java Web App: Passing form parameters across multiple pages

    - by digiarnie
    Hi, what is the best practice or best way of passing form parameters from page to page in a flow? If I have a flow where a user enters data in a form and hits next and repeats this process until they get to an approval page, what ways could I approach this problem to make the retention of data as simple as possible over the flow? I guess you could put all the information as you go in the session but could you get into memory issues if a lot of people are using your app and going through the flow at the same time?

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