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• Registering a delegate function with an ISO C++ callback (on mono)

  - by Stick it to THE MAN

  I am thinking of wrapping ISO C++ code in C# class. The only problem so far is how to deal with the C++ callbacks. In .Net languages (C# and Vb.Net), I believe the callback equivalent. Sticking with C# for now, can anyone recommend a way that I can register the C# delegate functions with my ISO C++ code. The ISO C++ code is a notification library, and I want to be able to "push" the notifications to the mono framework (i.e. C# delegates in this case). My underlying assumption is that the mechanism/steps to implement this would be the same for the .Net languages - I'll just have to code the actual delegates in the .Net language of choice - is that assumption correct? Last but not the least, is the question of thread saftey. The underlying ISO C++ code that I am exposing to .Net (mono to be more specific), is both re-ntrant and thread safe - do I have to do anything "extra" to call .Net delegate from my ISO C++ code?

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• use callback function to report stack backtrace

  - by user353394

  Assume I have the following: typedef struct { char *name; char binding; int address; } Fn_Symbol //definition of function symbol static Fn_Symbol *fnSymbols; //array of function symbols in a file statc int total; //number of symbol functions in the array and file static void PrintBacktrace(int sigum, siginfo_t * siginfo, void *context) { printf("\nSignal received %d (%s)\n", signum, strsignal(signum)); const int eip_index = 14; void *eip = (void *)((struct ucontext *)context)->uc_mcontext.gregs[eip_index]; printf("Error at [%p] %s (+0x%x), eip, fnName, offset from start); //????? exit(0); } I have this so far, but what is the best way using the fnSymbols static global pointer to identify the function where the error occured and then back trace through the stack to identify each calling function by address, name, and offset?

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• Facebook javascript in address bar, possible to replicate?

  - by DoMx

  This is my first experience with stackoverflow and I'm afraid my question asks of a lot for a first. I was looking at this thread: http://stackoverflow.com/questions/2634159/javascrypt-in-the-adress-bar-is-this-malicious and as you will see SLaks has very kindly deobfuscated the javascript and left us with what appears as the Javascript behind the automatic facebook invite code. As I'm fairly new to javascript, I was wondering, what other components were needed to get this code to work? You of course have the functions there and they are called by the obfuscated javascript but how exactly? Would it be possible to replicate this on a page of my own using the information available or is there more to this script I am missing? I am willing to financially assist somebody who could compile a solution for me. Thank you in advance.

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• Best practices for handling string in VC++?

  - by Hiren Gujarati

  As I am new to Visual C++, there are so many types for handling string. When I use some type and go ahead with coding but on next step, there are in-build functions that use other types & it always require to convert one type of string to other. I found so many blogs but so confused when see so many answers & try but some are working & some are not. Please give your answer or links that gives ultimate solution for handling different types of strings in visual c++.

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• Style of if: to nest or not to nest

  - by Marco

  A colleague of mine and me had a discussion about the following best-practice issue. Most functions/methods start with some parameter checking. I advocate the following style, which avoids nesting. if (parameter one is ugly) return ERROR; if (parameter two is nonsense || it is raining) return ERROR; // do the useful stuff return result; He, who comes from a more functional/logic programming background, prefers the following, because it reduces the number of exit points from the function. if (parameter one is ok) { if (parameter two is ok && the sun is shining) { // do the useful stuff return result } } return ERROR; Which one would you prefer and why?

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• correct way to store an exception in a variable

  - by Evan Teran

  I have an API which internally has some exceptions for error reporting. The basic structure is that it has a root exception object which inherits from std::exception, then it will throw some subclass of that. Since catching an exception thrown in one library and catching it in another can lead to undefined behavior (at least Qt complains about it and disallows it in many contexts). I would like to wrap the library calls in functions which will return a status code, and if an exception occurred, a copy of the exception object. What is the best way to store an exception (with it's polymorphic behavior) for later use? I believe that the c++0x futures API makes use of something like this. So what is the best approach? The best I can think of is to have a clone() method in each exception class which will return a pointer to an exception of the same type. But that's not very generic and doesn't deal with standard exceptions at all. Any thoughts?

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• Template type deduction with a non-copyable class

  - by Evan Teran

  Suppose I have an autolocker class which looks something like this: template <T> class autolocker { public: autolocker(T *l) : lock(l) { lock->lock(); } ~autolocker() { lock->unlock(); } private: autolocker(const autolocker&); autolocker& operator=(const autolocker&); private: T *lock; } Obviously the goal is to be able to use this autolocker with anything that has a lock/unlock method without resorting to virtual functions. Currently, it's simple enough to use like this: autolocker<some_lock_t> lock(&my_lock); // my_lock is of type "some_lock_t" but it is illegal to do: autolocker lock(&my_lock); // this would be ideal Is there anyway to get template type deduction to play nice with this (keep in my autolocker is non-copyable). Or is it just easiest to just specify the type?

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• "Ambiguous template specialization" problem

  - by Setien

  I'm currently porting a heap of code that has previously only been compiled with Visual Studio 2008. In this code, there's an arrangement like this: template <typename T> T convert( const char * s ) { // slow catch-all std::istringstream is( s ); T ret; is >> ret; return ret; } template <> inline int convert<int>( const char * s ) { return (int)atoi( s ); } Generally, there are a lot of specializations of the templated function with different return types that are invoked like this: int i = convert<int>( szInt ); The problem is, that these template specializations result in "Ambiguous template specialization". If it was something besides the return type that differentiated these function specializations, I could obviously just use overloads, but that's not an option. How do I solve this without having to change all the places the convert functions are called?

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• Best solution for language documentation.

  - by Simone Margaritelli

  I'm developing a new object oriented scripting language and the project itself is quite ready for audience now, so i'm starting to think about a serious (not as "drafty" as it is right now) way of document its grammar, functions from standard library and standard library classes. I've looked a bit around and almost every language hash its own web application for the documentation, Python uses Sphinx for instance. Which is the best PHP (don't have the time/will to install mod_who_knows_what on my server) application to accomplish this? I've used mediawiki a bit but i found its tag system a little bit hard to use in this context. Thanks for your answers.

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• How to create a string array in matlab?

  - by aduric

  I would like to pass a vector of strings from C++ to matlab. I have tried using the functions available such as mxCreateCharMatrixFromStrings but it doesn't give me the correct behavior. So, I have something like this: void mexFunction( int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) { vector<string> stringVector; stringVector.push_back("string 1"); stringVector.push_back("string 2"); //etc... The problem is how do I get this vector to the matlab environment? plhs[0] = ??? My goal is to be able to run: >> [strings] = MyFunc(...) >> strings(1) = 'string 1'

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• Why the macros in Objective-C / Cocoa?

  - by Joe

  I'm coming from a place without macros (Java/Python/C#/Scala) so perhaps my perspective is distorted but... Why are macros used in Cocoa? Two that spring to mind are NSLocalizedString and NSAssert (and STAssert). Would it be so hard / unsuitable to make them functions (which could be inlined)? I suppose I find them a little bizarre as an unnecessary throw-back to C (and yes, I am familiar with the pedigree of Obj-C). Is it just something that was done back in the day or is there a specific reason?

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• Other SecurityManager implementations available?

  - by mhaller

  Is there any other implementation (e.g. in an OSS project) of a Java SecurityManager available which has more features than the one in the JDK? I'm looking for features like configurable at runtime policies updateable at runtime, read from other data sources than a security.policy file Thread-aware, e.g. different policies per Thread Higher-level policies, e.g. "Disable network functions, but allow JDBC traffic" Common predefined policies, e.g. "Allow read-access to usual system properties like file.encoding or line.separator, but disallow read-access to user.home" Monitoring and audit trace logging, e.g. "Log all file access, log all network access going NOT to knownhost.example.org" Blocking jobs "requesting" a permission until an administrator grants permission, letting the thread/job continue ... I'm pretty sure that application servers (at least the commercial ones) have their own SecurityManager implementation or at least their own policy configuration. I'm wondering if there is any free project with similar requirements.

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• Is there a name for the technique of using base-2 numbers to encode a list of unique options?

  - by Lunatik

  Apologies for the rather vague nature of this question, I've never been taught programming and Google is rather useless to a self-help guy like me in this case as the key words are pretty ambiguous. I am writing a couple of functions that encode and decode a list of options into a Long so they can easily be passed around the application, you know this kind of thing: 1 - Apple 2 - Orange 4 - Banana 8 - Plum etc. In this case the number 11 would represent Apple, Orange & Plum. I've got it working but I see this used all the time so assume there is a common name for the technique, and no doubt all sorts of best practice and clever algorithms that are at the moment just out of my reach.

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• Is there any Prototype Javascript function similar to Jquery Live to trace dynamic dom elements?

  - by Wbdvlpr

  Hi Event.observe(window,"load",function() { $$(".elem_classs").findAll(function(node){ return node.getAttribute('title'); }).each(function(node){ new Tooltip(node,node.title); node.removeAttribute("title"); }); }); Using above method, I can retrieve all elements having ".elem_class" and apply some javascript functions on them. But I have a modal/popup box which has some elements also having ".elem_class" and these dont get in the scope of findAll/each as they are loaded into the dom thru ajax. How do I apply the same to dynamically loaded elements as well? I am using Prototype Library. (I have used JQuery's Live function which keeps track of all future elements, but need to achieve something similar using Prototype) Thanks.

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• Functional languages & support for memoization

  - by Joel

  Do any of the current crop of popular functional languages have good support for memoization & if I was to pick one on the strength of its memoisation which would you recommend & why? Update: I'm looking to optimise a directed graph (where nodes could be functions or data). When a node in the graph is updated I would like the values of other nodes to be recalculated only if they depend the node that changed. Update2: require free or open-source language/runtime.

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• Is it bad practice to use python's getattr extensively?

  - by Wilduck

  I'm creating a shell-like environment. My original method of handleing user input was to use a dictionary mapping commands (strings) to methods of various classes, making use of the fact that functions are first class objects in python. For flexibility's sake (mostly for parsing commands), I'm thinking of changing my setup such that I'm using getattr(command), to grab the method I need and then passing arguments to it at the end of my parser. Another advantage of this approach is not having to update my (currently statically implemented) command dictionary every time I add a new method/command. My question is, will I be taking a hit to the efficiency of my shell? Does it matter how many methods/commands I have? I'm currently looking at 30 some commands, which could eventually double.

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• Javascript / Flash : When exactly are flash external callback methods triggered ?

  - by felace

  I have a flash application using callbacks to javascript functions (eg. when it receives some data over a socket, it'll call a js script which would change the content of a div according to that given data). Afaik, there is no actual mutual exclusion in javascript so I'm not sure if I can/need to simulate something like : callbackFunc() { lock(mutex1) foo unlock(mutex1) } ... someOtherFunc() { lock(mutex1) bar unlock(mutex1) } So, the question is, when are those callbacks called ? Are they simply queued to be executed right after the browser finishes its task or are they triggered randomly ?

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• How to integrate access control with my ORM in a .net windows form application?

  - by Ying

  I am developing a general database query tools, a .Net 3.5 Windows Form application. In order to make the presentation layer is independent of the database layer. I use an ORM framework, XPO from DevExpress. But, I have no access control function built in. I surfed Internet and I found in WCF Data Services, there is an interesting concept, Interceptor, which is following AOP(Aspect Oriented Programming). I am wondering who has such an experience to build access control in ORM. My basic requirement is : It should be a general method and controlled by users in runtime. So any hard coding is not acceptable. It could be based on attribute, database table, or even an external assembly. I am willing to buy a ready solution. According to the idea of AOP, an access control function can be integrated with existing functions easily and nearly not knowingly to the previous developer;) Any suggestions are welcome.

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• c++ Using const in a copy constructor?

  - by Anton

  I have never written copy constructor, so in order to avoid pain i wanted to know if what i have coded is legit. It compiles but i am not sure that it works as a copy constructor should. Also do i have to use const in the copy constructor or i can simply drop it. (What i dont like about const is that the compiler cries if i use some non const functions). //EditNode.h class EditNode { explicit EditNode(QString elementName); EditNode(const EditNode &src); } //EditNodeContainer.h class EditNodeContainer : public EditNode { explicit EditNodeContainer(QString elementName); EditNodeContainer(const EditNodeContainer &src); } //EditNodeContainer.cpp EditNodeContainer::EditNodeContainer(QString elementName):EditNode(elementName) { } //This seems to compile but not sure if it works EditNodeContainer::EditNodeContainer(const EditNodeContainer &src):EditNode(src) { } //the idea whould be to do something like this EditNodeContainer *container1 = new EditNodeContainer("c1"); EditNodeContainer *copyContainer = new EditNodeContainer(container1);

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• How to inline a function for only release build.

  - by Benjamin

  // common.h // This is foo funtion. It has a body. __inline void foo() { /* something */ } // a.cpp #include "common.h" // for foo function // Call foo // b.cpp #include "common.h" // for foo function // Call foo I would like to inline the foo function only when I build for release. -I dont want to inline functions for Debug build. I tried it but linker errors annoyed me. In this case, foo function's body is defined in common.h header file. so if I just do //common.h #if !defined(_DEBUG) __inline #endif void foo() { /* something */ } I will be met a link error in DEBUG build. Because two modules try to include common.h. I have no idea to solve it. Is it possible?

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• Why not speed up testing by using function dependency graph?

  - by Maltrap

  It seems logical to me that if you have a dependency graph of your source code (tree showing call stack of all functions in your code base) you should be able to save a tremendous amount of time doing functional and integration tests after each release. Essentially you will be able to tell the testers exactly what functionality to test as the rest of the features remain unchanged from a source code point of view. If for instance you change a spelling mistake in once piece of the code, there is no reason to run through your whole test script again "just in case" you introduced a critical bug. My question, why are dependency trees not used in software engineering and if you use them, how do you maintain them? What tools are available that generate these trees for C# .NET, C++ and C source code?

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• Should I use implicit conversions to enforce preconditions?

  - by Malvolio

  It occurs to me that I could use use implicit conversions to both announce and enforce preconditions. Consider this: object NonNegativeDouble { implicit def int2nnd(d : Double) : NonNegativeDouble = new NonNegativeDouble(d) implicit def nnd2int(d : NonNegativeDouble) : Double = d.v def sqrt(n : NonNegativeDouble) : NonNegativeDouble = scala.math.sqrt(n) } class NonNegativeDouble(val v : Double ) { if (v < 0) { throw new IllegalArgumentException("negative value") } } object Test { def t1 = { val d : Double = NonNegativeDouble.sqrt(3.0); printf("%f\n", d); val n : Double = NonNegativeDouble.sqrt(-3.0); } } Ignore for the moment the actual vacuity of the example: my point is, the subclass NonNegativeDouble expresses the notion that a function only takes a subset of the entire range of the class's values. First is this: A good idea, a bad idea, or an obvious idea everybody else already knows about Second, this would be most useful with basic types, like Int and String. Those classes are final, of course, so is there a good way to not only use the restricted type in functions (that's what the second implicit is for) but also delegate to all methods on the underlying value (short of hand-implementing every delegation)?

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• Generating random numbers in C

  - by moonstruckhorrors

  While searching for Tutorials on generating random numbers in C I found This Topic When I try to use the rand() function with parameters, I always get the random number generated 0. When I try to use the rand() function with parameters, I always get the value 41. And whenever I try to use arc4random() and random() functions, I get a LNK2019 error. Here's what I'm doing: #include <stdlib.h> int main() { int x; x = rand(6); printf("%d", x); } This code always generate 41. Where am I going wrong?? P.S. : I'm running Windows XP SP3 and using VS2010 Command Prompt as compiler. P.P.S. : Took me 15 minutes to learn how to format properly.

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• Autorelease for CGMutablePathRef?

  - by huggie

  Hi, I am developing for iphone. I want to creating a mutable path via CGPathCreateMutable(), and I want to return it out of the function which creates it. I'm suppose to call a CGPathRelease() when I'm done with it. But since I'm returning it I wish to autorelease it. Since Quartz path is a C code (and doesn't look like an objective C object), is it correct that I cannot call autorelease on it? Edit: For others who stumble upon this question, the below advise is for C functions returning Core foundation objects only. For objective C methods returning Core foundation objects, see http://stackoverflow.com/questions/2901942/ownership-regarding-to-returned-quartz-objects

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• What is the easiest way to loop through a folder of files in C#?

  - by badpanda

  I am new to C# and am trying to write a program that navigates the local file system using a config file containing relevant filepaths. My question is this: What are the best practices to use when performing file I/O (this will be from the desktop app to a server and back) and file system navigation in C#? I know how to google, and I have found several solutions, but I would like to know which of the various functions is most robust and flexible. As well, if anyone has any tips regarding exception handling for C# file I/O that would also be very helpful. Thanks!!! badPanda

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