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  • Constructing a function call in C

    - by 0x6adb015
    Given that I have a pointer to a function (provided by dlsym() for example) and a linked list of typed arguments, how can I construct a C function call with those arguments? Example: struct param { enum type { INT32, INT64, STRING, BOOL } type; union { int i32; long long i64; char *str; bool b; } value; struct param *next; }; int call_this(int (*function)(), struct param *args) { int result; /* magic here that calls function(), which has a prototype of f(int, long long, char *, bool); , when args consist of a linked list of INT32, INT64, STRING, BOOL types. */ return result; } The OS is Linux. I would like the solution to be portable across MIPS, PPC and x86 (all 32 bits) architecture, using GCC as the compiler. Thanks!

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  • When is C++ covariance the best solution?

    - by Neil Butterworth
    This question was asked here a few hours ago and made me realise that I have never actually used covariant return types in my own code. For those not sure what covariance is, it's allowing the return type of (typically) virtual functions to differ provided the types are part of the same inheritance hierarchy. For example: struct A { virtual ~A(); virtual A * f(); ... }; struct B : public A { virtual B * f(); ... }; The different return types of the two f() functions are said to be covariant. Older versions of C++ required the return types to be the same, so B would have to look like: struct B : public A { virtual A * f(); ... }; So, my question: Does anyone have a real-world example where covariant return types of virtual functions are required, or produce a superior solution to simply returning a base pointer or reference?

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  • Force an object to be allocated on the heap

    - by Warren Seine
    A C++ class I'm writing uses shared_from_this() to return a valid boost::shared_ptr<>. Besides, I don't want to manage memory for this kind of object. At the moment, I'm not restricting the way the user allocates the object, which causes an error if shared_from_this() is called on a stack-allocated object. I'd like to force the object to be allocated with new and managed by a smart pointer, no matter how the user declares it. I thought it could be done through a proxy or an overloaded new operator, but I can't find a proper way of doing that. Is there a common design pattern for such usage? If it's not possible, how can I test it at compile time?

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  • Trouble creating a makefile

    - by catia
    Hi everyone! I'm having some trouble making a Makefile. Write now I just compile everything every time. Although, the professor is ok with that, I do want to get it working faster and to avoid unnecessary compiling. Here's what I have. FILES= p6.cpp SetIter.cpp Node.cpp Set.cpp CFLAGS= -ansi -pendantic -Wall -Wextra CC= g++ MakePg6: p6.cpp SetIter.cpp Node.cpp Set.cpp $(CC) $(CFLAGS) $(FILES) -o pg6 Node.cpp - node class Set.cpp - uses nodes. Friend of Node. SetIter.cpp - gets a set and uses a pointer to iterator through I'm confused with some of the depencies arising from the friends thing and the point of lib.o being included in the Makefile as some sites have. Any help is greatly appreciated. Thanks in advance.

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  • Regular Expression to match unlimited number of options

    - by Pekka
    I want to be able to parse file paths like this one: /var/www/index.(htm|html|php|shtml) into an ordered array: array("htm", "html", "php", "shtml") and then produce a list of alternatives: /var/www/index.htm /var/www/index.html /var/www/index.php /var/www/index.shtml Right now, I have a preg_match statement that can split two alternatives: preg_match_all ("/\(([^)]*)\|([^)]*)\)/", $path_resource, $matches); Could somebody give me a pointer how to extend this to accept an unlimited number of alternatives (at least two)? Just regarding the regular expression, the rest I can deal with. The rule is: The list needs to start with a ( and close with a ) There must be one | in the list (i.e. at least two alternatives) Any other occurrence(s) of ( or ) are to remain untouched.

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  • Manage bad_alloc exception in C++ construtor

    - by Jimmy zhang
    I have Java experience and recently am doing some C++ coding. My question is that if I have class A, in which I have to instantiate class B and class C as two of the member variables of A. If in the constructor of A, should I assume that allocations of class B and C never fail, and handle the bad allocation exception in the destructor of A? If I don't make that assumption, meaning that I add some try catch block to catch bad_alloc of class B and class C, then if the allocation exception occurs, should I do clean up in the constructor of A? What are the recommended practices? If "new" generates a bad allocation, what value does the pointer carry?

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  • Please explain syntax rules and scope for "typedef"

    - by unknown google user
    What are the rules? OTOH the simple case seems to imply the new type is the last thing on a line. Like here Uchar is the new type. typedef unsigned char Uchar; But a function pointer is completely different. Here the new type is pFunc: typedef int (*pFunc) (int); I can't think of any other examples offhand but I have come across some very confusing usages. So are there rules or are people just suppose to know from experience that this is how it is done because they have seen it done this way before? ALSO: What is the scope of a typedef. Thanks to everyone.

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  • What elegant method callback design should be used ?

    - by ereOn
    Hi, I'm surprised this question wasn't asked before on SO (well, at least I couldn't find it). Have you ever designed a method-callback pattern (something like a "pointer" to a class method) in C++ and, if so, how did you do it ? I know a method is just a regular function with some hidden this parameter to serve as a context and I have a pretty simple design in mind. However, since things are often more complex than they seem to, I wonder how our C++ gurus would implement this, preferably in an elegant and standard way. All suggestions are welcome !

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  • How can i use listDictionary?

    - by Phsika
    i can fill my listdictinary but, if running error returns to me in " foreach (string ky in ld.Keys)"(invalid operation Exception was unhandled) Error Detail : After creating a pointer to the list of sample collection has been changed. C# ListDictionary ld = new ListDictionary(); foreach (DataColumn dc in dTable.Columns) { MessageBox.Show(dTable.Rows[0][dc].ToString()); ld.Add(dc.ColumnName, dTable.Rows[0][dc].ToString()); } foreach (string ky in ld.Keys) if (int.TryParse(ld[ky].ToString(), out QuantityInt)) ld[ky] = "integer"; else if(double.TryParse(ld[ky].ToString(), out QuantityDouble)) ld[ky]="double"; else ld[ky]="nvarchar";

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  • C++'s unordered_map / hash_map / Google's dense_hash - how to input binary data (buf+len) and insert

    - by shlomif
    Hi all, I have two questions about Google's dense_hash_map, which can be used instead of the more standard unordered_map or hash_map: How do I use an arbitrary binary data memory segment as a key: I want a buffer+length pair, which may still contain some NUL (\0) characters. I can see how I use a NUL-terminated char * string , but that's not what I want. How do I implement an operation where I look if a key exists, and if not - insert it and if it does return the pointer to the existing key and let me know what actually happened. I'd appreciate it if anyone can shed any light on this subject. Regards, -- Shlomi Fish

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  • CSS menu is flickering when scrolling through it with hover effects

    - by kritop
    I hope i described the problem well!? You can see it here: http://dealmob.de/index_dev.html when u hover over the menu up and down fast u see the that its not staying, insteads its flickering like you would change the margins/paddings by few pixels. Any advice on how to solve this problem? thanks a lot like requested: #topcities { float:right; } #topcities li { padding-left:5px; width:100px; } #topcities li:hover { cursor:pointer; color:#000; background: url(images/hover_menue_back.jpg) repeat-x #FFF; -moz-border-radius: 5px; -webkit-border-radius: 5px; border:grey 1px solid; width:100px; }

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  • Are self-described / auto-descriptive services loosely or tightly coupled in a SOA architecture ?

    - by snowflake
    I consider a self-described / auto-descriptive service as a good thing in a SOA architecture, since (almost) everything you know to call the service is present in the service contract (such a WSDL). Sample of a non self-described service for me is Facebook Query Language (FQL http://wiki.developers.facebook.com/index.php/FQL), or any web service exchanging XML flow in a one String parameter for then parsing XML and performing treatments. Last ones seem further more technically decoupled, since technically you can switch implementations without technical impact on the caller, handling compatibility between implementations/versions at a business level. On the other side, having no strong interface (diluted into the service and its version), make the service tightly coupled to the existing implementation (more difficulty to interchange the service and to ensure perfect compatibility). This question is related to http://stackoverflow.com/questions/2503071/how-to-implement-loose-coupling-with-a-soa-architecture So, are self-described / auto-descriptive services loosely or tightly coupled in a SOA architecture ? What are the impacts regarding ESBs ? Any pointer will be appreciated.

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  • Which tool can list writing access to a specific variable in C?

    - by Lichtblitz
    Unfortunately I'm not even sure how this sort of static analysis is called. It's not really control flow analysis because I'm not looking for function calls and I don't really need data flow analysis because I don't care about the actual values. I just need a tool that lists the locations (file, function) where writing access to a specific variable takes place. I don't even care if that list contained lines that are unreachable. I could imagine that writing a simple parser could suffice for this task but I'm certain that there must be a tool out there that does this simple analysis. As a poor student I would appreciate free or better yet open source tools and if someone could tell me how this type of static analysis is actually called, I would be equally grateful! EDIT: I forgot to mention there's no pointer arithmetic in the code base.

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  • How to save/export a DOM element to an image?

    - by Don Don
    Hi, I have a web page which has a form element (with its ID known) and inside the form there are multiple DIVs, and the position of each div may be changed. What I'd like to do is: a) Save the current state of this form // var currentForm=document.forms['myFrm'].innerHTML; would probably suffice... b) Save or export the entire form with the most current position of each DIV to an image file. // how to save/export the javascript var of currentForm to an image file is the key question. Any help/pointer would be appreciated.

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  • Get path to a file via flash

    - by jeffkolez
    I'm not a flash dev, but I'm turning to it to try and meet a requirement. I'm to allow a user to select a file on their computer, then pass it to my web application. I know it's not possible to do this using Javascript, hence wanting to use flash. First, is this possible? Second, can I get a pointer on how its done? To clarify: I'm just looking for the path to the file. I don't want to upload it.

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  • small string optimization for vector?

    - by BuschnicK
    I know several (all?) STL implementations implement a "small string" optimization where instead of storing the usual 3 pointers for begin, end and capacity a string will store the actual character data in the memory used for the pointers if sizeof(characters) <= sizeof(pointers). I am in a situation where I have lots of small vectors with an element size <= sizeof(pointer). I cannot use fixed size arrays, since the vectors need to be able to resize dynamically and may potentially grow quite large. However, the median (not mean) size of the vectors will only be 4-12 bytes. So a "small string" optimization adapted to vectors would be quite useful to me. Does such a thing exist? I'm thinking about rolling my own by simply brute force converting a vector to a string, i.e. providing a vector interface to a string. Good idea?

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  • delete & new in c++

    - by singh
    Hi This may be very simple question,But please help me. i wanted to know what exactly happens when i call new & delete , For example in below code char * ptr=new char [10]; delete [] ptr; call to new returns me memory address. Does it allocate exact 10 bytes on heap, Where information about size is stored.When i call delete on same pointer,i see in debugger that there are a lot of byte get changed before and after the 10 Bytes. Is there any header for each new which contain information about number of byte allocated by new. Thanks a lot

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  • Manipulating both unicode and ASCII character set in C#

    - by Murlex
    I have this mapping in my C# application string [,] unicode2Ascii = { { "&#3001;", "\x86" } }; ஹ - is the unicode value for a tamil literal "ஹ". This is the raw hex literal for the unicode value saved by MS Word as a byte sequence. I am trying to map these unicode value "strings" to a hex value under 255 (so as to accommodate non-unicode supported systems). I trying to use string.replace like this: S = S.replace(unicode2Ascii[0,0], unicode2Ascii[0,1]); However the resultant ouput has a ? instead of the actual hex 0x86 stored. Any pointer on how I could set the encoding for the second element of that array to something like windows-1252? Or is there a better way to do this conversion? thanks in advance

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  • How to create an image from canvas data?

    - by Jakub Hampl
    In my application I am trying to save an arbitrary part of a rendered HTML canvas to an image file. In my Javascript I call ctx.getImageData(x, y, w, h) and pass the resulting object to my macruby code (though if you know a solution in objc I am also very interested). There I'm trying to create a NSBitmapImageRep object so that I can then save to an image format the user desires. This is my code so far (the function gets a WebScriptObject as it's argument): def setimagedata(d) w = d.valueForKey("width").to_i h = d.valueForKey("height").to_i data = Pointer.new(:char, d.valueForKey("data").valueForKey("length").to_i) d.valueForKey("data").valueForKey("length").to_i.times do |i| data[i] = d.valueForKey("data").webScriptValueAtIndex(i).to_i end puts "data complete" # get's called @exported_image = NSBitmapImageRep.alloc.initWithBitmapDataPlanes(data, pixelsWide: w, pixelsHigh:h, bitsPerSample: 32, samplesPerPixel: 4, hasAlpha: true, isPlanar: false, colorSpaceName: NSCalibratedRGBColorSpace, bitmapFormat: NSAlphaNonpremultipliedBitmapFormat, bytesPerRow: 0, bitsPerPixel: 0) puts "done" # doesn't get called end The code doesn't seem to get through the initWithBitmapDataPlanes function but gives no error. My question is: what am I doing wrong? Is this approach reasonable (if not, what would be better?).

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  • Compiling C++ when two classes references one another

    - by Omry
    I am trying to write a simple wrapper around a connection pointer that will return it to the pool when the wrapper is destroyed. but it wont compile because the ConnectionPool and AutoConn need each other to be declared. I tried to use forward deceleration but it didn't work. how do I solve this? (using g++) class Connection {}; class ConnectionPool { Connection *m_c; public: AutoConn getConn() { return AutoConn(this, m_c); // by value } void releaseConnection(Connection *c) { } }; class AutoConn { ConnectionPool* m_pool; Connection *m_connection; public: AutoConn(ConnectionPool* pool, Connection *c) : m_pool(pool), m_connection(c) {} ~AutoConn() { m_pool->releaseConnection(m_connection); } };

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  • Symfony 1.3: different form filters generated

    - by user248959
    Hi, i have this class in rs1/lib/filter/doctrine/FelizFormFilter.class.php <?php /** * Feliz filter form. * * @package rs * @subpackage filter * @author Your name here * @version SVN: $Id: sfDoctrineFormFilterTemplate.php 23810 2009-11-12 11:07:44Z Kris.Wallsmith $ */ class FelizFormFilter extends BaseFelizFormFilter { public function configure() { } } and this in rs2/lib/filter/doctrine/FelizFormFilter.class.php <?php /** * Feliz filter form. * * @package filters * @subpackage Feliz * * @version SVN: $Id: sfDoctrineFormFilterTemplate.php 11675 2008-09-19 15:21:38Z fabien $ */ class FelizFormFilter extends BaseFelizFormFilter { public function configure() { } } Both were generated using "php symfony doctrine:build --all --and-load" and the version of symfony is 1.3.4 in both. This is the schema of both cases: Feliz: columns: name: string(20) Could you tell me why are different? One more thing in Eclipse: when i go with the mouse pointer to the word "BaseFelizFormFilter", in the second case (rs2) the yellow window with the information about the class is showed, but in the first case that yellow popup is not showed. Why? Javi

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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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  • Text indent is not working in ie7

    - by saorabh
    I am working on a website and on the top navigation bar there is a search box, I applied the following css on the search submit button #submit{background:url("img/new-search-icon.png") no-repeat scroll -1px 0 #FFFFFF; border:0 none; cursor:pointer; display:block; height:21px; padding:0; position:absolute; right:0; text-indent:-9999px; top:0; width:20px; z-index:2;} My Problem is in IE7 the text indent is not working please help me if you want to see the demo you can view it by clicking here Click here. Please help me.

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  • Strange behaviour of Android debugger in Eclipse when using Camera for preview.

    - by Buzzy
    Hi, I have an Android application that uses a SurfaceView subclass and Camera object to preview images before capture. Once I capture an image, I stop the preview and release the camera. Execution stops at any breakpoint after this. However, apart from the "Suspend" and "Terminate" icons, the rest are disabled. This is strange because the "Debug Current Instruction Pointer" is clearly at the said breakpoint and execution is already suspended. I can't perform any debugging operations and have no option but to terminate the session. Sometimes (very rarely), the session terminates by itself. I can confirm that this odd behavior takes place only after I preview the camera capture. I am fairly new to Android development. Is there some obvious mistake I am making? Any help would be highly appreciated.

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  • C++ associative array with arbitrary types for values

    - by Gerald Kaszuba
    What is the best way to have an associative array with arbitrary value types for each key in C++? Currently my plan is to create a "value" class with member variables of the types I will be expecting. For example: class Value { int iValue; Value(int v) { iValue = v; } std::string sValue; Value(std::string v) { sValue = v; } SomeClass *cValue; Value(SomeClass *v) { cValue = c; } }; std::map<std::string, Value> table; A downside with this is you have to know the type when accessing the "Value". i.e.: table["something"] = Value(5); SomeClass *s = table["something"].cValue; // broken pointer Also the more types that are put in Value, the more bloated the array will be. Any better suggestions?

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