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• How to REALLY start thinking in terms of objects?

  - by Mr Grieves

  I work with a team of developers who all have several years of experience with languages such as C# and Java. Most of them are young enough to have been shown OOP as a standard way to develop software in university and are very comfortable with concepts such as inheritance, abstraction, encapsulation and polymorphism. Yet, many of them, and I have to include myself, still tend to create classes which are meant to be used in a very functional fashion. The resulting software is often several smaller classes which correctly represent business objects which get passed through larger classes which only supply ways to modify and use those objects (functions). Large complex difficult-to-maintain classes named Manager are usually the result of such behaviour. I can see two theoretical reasons why people might write this type of code: It's easy to start thinking of everything in terms of the database Deep down, for me, a computer handling a web request feels more like a functional operation than an object oriented operation when you think about Request Handlers, Threads, Processes, CPU Cores and CPU operations... I want source code which is easy to read and easy to modify. I have seen excellent examples of OO code which meet these objectives. How can I start writing code like this? How I can I really start thinking in an object oriented fashion? How can I share such a mentality with my colleagues?

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• Why is an anemic domain model considered bad in C#/OOP, but very important in F#/FP?

  - by Danny Tuppeny

  In a blog post on F# for fun and profit, it says: In a functional design, it is very important to separate behavior from data. The data types are simple and "dumb". And then separately, you have a number of functions that act on those data types. This is the exact opposite of an object-oriented design, where behavior and data are meant to be combined. After all, that's exactly what a class is. In a truly object-oriented design in fact, you should have nothing but behavior -- the data is private and can only be accessed via methods. In fact, in OOD, not having enough behavior around a data type is considered a Bad Thing, and even has a name: the "anemic domain model". Given that in C# we seem to keep borrowing from F#, and trying to write more functional-style code; how come we're not borrowing the idea of separating data/behavior, and even consider it bad? Is it simply that the definition doesn't with with OOP, or is there a concrete reason that it's bad in C# that for some reason doesn't apply in F# (and in fact, is reversed)? (Note: I'm specifically interested in the differences in C#/F# that could change the opinion of what is good/bad, rather than individuals that may disagree with either opinion in the blog post).

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• Soapi.CS : A fully relational fluent .NET Stack Exchange API client library

  - by Sky Sanders

  Soapi.CS for .Net / Silverlight / Windows Phone 7 / Mono as easy as breathing...: var context = new ApiContext(apiKey).Initialize(false); Question thisPost = context.Official .StackApps .Questions.ById(386) .WithComments(true) .First(); Console.WriteLine(thisPost.Title); thisPost .Owner .Questions .PageSize(5) .Sort(PostSort.Votes) .ToList() .ForEach(q=> { Console.WriteLine("\t" + q.Score + "\t" + q.Title); q.Timeline.ToList().ForEach(t=> Console.WriteLine("\t\t" + t.TimelineType + "\t" + t.Owner.DisplayName)); Console.WriteLine(); }); // if you can think it, you can get it. Output Soapi.CS : A fully relational fluent .NET Stack Exchange API client library 21 Soapi.CS : A fully relational fluent .NET Stack Exchange API client library Revision code poet Revision code poet Votes code poet Votes code poet Revision code poet Revision code poet Revision code poet Votes code poet Votes code poet Votes code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Votes code poet Comment code poet Revision code poet Votes code poet Revision code poet Revision code poet Revision code poet Answer code poet Revision code poet Revision code poet 14 SOAPI-WATCH: A realtime service that notifies subscribers via twitter when the API changes in any way. Votes code poet Revision code poet Votes code poet Comment code poet Comment code poet Comment code poet Votes lfoust Votes code poet Comment code poet Comment code poet Comment code poet Comment code poet Revision code poet Comment lfoust Votes code poet Revision code poet Votes code poet Votes lfoust Votes code poet Revision code poet Comment Dave DeLong Revision code poet Revision code poet Votes code poet Comment lfoust Comment Dave DeLong Comment lfoust Comment lfoust Comment Dave DeLong Revision code poet 11 SOAPI-EXPLORE: Self-updating single page JavaSript API test harness Votes code poet Votes code poet Votes code poet Votes code poet Votes code poet Comment code poet Revision code poet Votes code poet Revision code poet Revision code poet Revision code poet Comment code poet Revision code poet Votes code poet Comment code poet Question code poet Votes code poet 11 Soapi.JS V1.0: fluent JavaScript wrapper for the StackOverflow API Comment George Edison Comment George Edison Comment George Edison Comment George Edison Comment George Edison Comment George Edison Answer George Edison Votes code poet Votes code poet Votes code poet Votes code poet Revision code poet Revision code poet Answer code poet Comment code poet Revision code poet Comment code poet Comment code poet Comment code poet Revision code poet Revision code poet Votes code poet Votes code poet Votes code poet Votes code poet Comment code poet Comment code poet Comment code poet Comment code poet Comment code poet 9 SOAPI-DIFF: Your app broke? Check SOAPI-DIFF to find out what changed in the API Votes code poet Revision code poet Comment Dennis Williamson Answer Dennis Williamson Votes code poet Votes Dennis Williamson Comment code poet Question code poet Votes code poet About A robust, fully relational, easy to use, strongly typed, end-to-end StackOverflow API Client Library. Out of the box, Soapi provides you with a robust client library that abstracts away most all of the messy details of consuming the API and lets you concentrate on implementing your ideas. A few features include: A fully relational model of the API data set exposed via a fully 'dot navigable' IEnumerable (LINQ) implementation. Simply tell Soapi what you want and it will get it for you. e.g. "On my first question, from the author of the first comment, get the first page of comments by that person on any post" my.Questions.First().Comments.First().Owner.Comments.ToList(); (yes this is a real expression that returns the data as expressed!) Full coverage of the API, all routes and all parameters with an intuitive syntax. Strongly typed Domain Data Objects for all API data structures. Eager and Lazy Loading of 'stub' objects. Eager\Lazy loading may be disabled. When finer grained control of requests is desired, the core RouteMap objects may be leveraged to request data from any of the API paths using all available parameters as documented on the help pages. A rich Asynchronous implementation. A configurable request cache to reduce unnecessary network traffic and to simplify your usage logic. There is no need to go out of your way to be frugal. You may set a distinct cache duration for any particular route. A configurable request throttle to ensure compliance with the api terms of usage and to simplify your code in that you do not have to worry about and respond to 50X errors. The RequestCache and Throttled Queue are thread-safe, so can make as many requests as you like from as many threads as you like as fast as you like and not worry about abusing the api or having to write reams of management/compensation code. Configurable retry threshold that will, by default, make up to 3 attempts to retrieve a request before failing. Every request made by Soapi is properly formed and directed so most any http error will be the result of a timeout or other network infrastructure. A retry buffer provides a level of fault tolerance that you can rely on. An almost identical javascript library, Soapi.JS, and it's full figured big brother, Soapi.JS2, that will enable you to leverage your server cycles and bandwidth for only those tasks that require it and offload things like status updates to the client's browser. License Licensed GPL Version 2 license. Why is Soapi.CS GPL? Can I get an LGPL license for Soapi.CS? (hint: probably) Platforms .NET 3.5 .NET 4.0 Silverlight 3 Silverlight 4 Windows Phone 7 Mono Download Source code lives @ http://soapics.codeplex.com. Binary releases are forthcoming. codeplex is acting up again. get the source and binaries @ http://bitbucket.org/bitpusher/soapi.cs/downloads The source is C# 3.5. and includes projects and solutions for the following IDEs Visual Studio 2008 Visual Studio 2010 ModoDevelop 2.4 Documentation Full documentation is available at http://soapi.info/help/cs/index.aspx Sample Code / Usage Examples Sample code and usage examples will be added as answers to this question. Full API Coverage all API routes are covered Full Parameter Parity If the API exposes it, Soapi giftwraps it for you. Building a simple app with Soapi.CS - a simple app that gathers all traces of a user in the whole stackiverse. Fluent Configuration - Setting up a Soapi.ApiContext could not be easier Bulk Data Import - A tiny app that quickly loads a SQLite data file with all users in the stackiverse. Paged Results - Soapi.CS transparently handles multi-page operations. Asynchronous Requests - Soapi.CS provides a rich asynchronous model that is especially useful when writing api apps in Silverlight or Windows Phone 7. Caching and Throttling - how and why Apps that use Soapi.CS Soapi.FindUser - .net utility for locating a user anywhere in the stackiverse Soapi.Explore - The entire API at your command Soapi.LastSeen - List users by last access time Add your app/site here - I know you are out there ;-) if you are not comfortable editing this post, simply add a comment and I will add it. The CS/SL/WP7/MONO libraries all compile the same code and with the exception of environmental considerations of Silverlight, the code samples are valid for all libraries. You may also find guidance in the test suites. More information on the SOAPI eco-system. Contact This library is currently the effort of me, Sky Sanders (code poet) and can be reached at gmail - sky.sanders Any who are interested in improving this library are welcome. Support Soapi You can help support this project by voting for Soapi's Open Source Ad post For more information about the origins of Soapi.CS and the rest of the Soapi eco-system see What is Soapi and why should I care?

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• A programming language that does not allow IO. Haskell is not a pure language

  - by TheIronKnuckle

  (I asked this on Stack Overflow and it got closed as off-topic, I was a bit confused until I read the FAQ, which discouraged subjective theoratical debate style questions. The FAQ here doesn't seem to have a problem with it and it sounds like this is a more appropriate place to post. If this gets closed again, forgive me, I'm not trying to troll) Are there any 100% pure languages (as I describe in the Stack Overflow post) out there already and if so, could they feasibly be used to actually do stuff? i.e. do they have an implementation? I'm not looking for raw maths on paper/Pure lambda calculus. However Pure lambda calculus with a compiler or a runtime system attached is something I'd be interested in hearing about.

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• Building Single Page Apps on the Microsoft Stack

  - by Stephen.Walther

  Thank you everyone who came to my talk last night on Building Single Page Apps on the Microsoft Stack. I’ve attached the slides and code samples below. Here’s a quick summary of the talk. I argued that Single Page Apps are better than traditional Server Side Apps because: Single Page Apps are Stateful – In a traditional server-side app, whenever you navigate to a new page, all of your previous state is lost. It is like rebooting your computer whenever you perform any action In a Single Page App, Your Presentation Layer is Not Miles Away – In a traditional server-side app, because everything happens on the server, your presentation layer is separated from the user by space and time. In a Single Page App, the presentation layer is in the browser and not the server (which is the right place for a presentation layer). A Single Page App Respects the Web – It is easier to take advantage of HTML5 and related standards when building a Single Page App. Next, I recommended using the following four technologies when building a web application: Knockout – This is how you create your presentation layer. ASP.NET Web API – This is how you expose JSON data from your web server and perform server-side validation. HTML5 – This is how you implement client-side validation. Sammy – This is how you implement client-side routing and create a Single Page App with multiple virtual pages. There are code samples in the download (look in the Samples folder) which demonstrate how all of these technologies work when building Single Page Apps. Powerpoint Sample Code

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• MQTT, GWT, ActiveMQ stack to bring jms to the browser

  - by scphantm

  I am in the preliminary stages of architecting a legacy replacement project. They already have sub half second performance on their green screens and they want the same on their web app. We have a 390 mainframe that can handle anything we throw at it but they don't have a good jvm for it, so we have two tiers of websphere servers between the mainframe and the browser, The ui server, and the bl server. For the ui, I'm leaning towards GWT. But one thing that I think would seal the deal is to add messaging capabilities to the browser. The idea is say you click on a link that displays a second panel of information, instead of the classic GWT where it triggers a GWT-RPC call to the ui server, the ui server routs it to the bl server, the bl sends it to the mainframe and back out, it drops an MQTT message directly to the bl server or directly to the mainframe. Say writes go to the bl, reads go to the mainframe. This is an easy enough thing in classic jms because you can issue a message that has an expected response. Then have your callback ready to get the resonse. But from what I'm reading so far. It looks like mqtt doesn't have that. It looks like it's strictly fire and forget, which would make it really tough to come up with a way to get a response back to the workstation that called it. Am I right here? Has anyone tried this stack before with gwt.

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• Drawing the call stack in a recursive method

  - by Shaza

  Hey, I want to draw the call stack for any recursive method, so I've created a schema like this, recursiveMethod(){ //Break recursion condition if(){ // Add value here to the return values' list- No drawing return } else{ //Draw stack with the value which will be pushed to the stack here variable <- recursiveMethod() //Clear the drawing which represents the poped value from the stack here return variable }} Notes: This schema can draw recursive methods with n recursive call by making the recursive calls in a separate return statements. returnValues list, is a list which save all the return values, just for viewing issues. What do you think of this? any suggestions are extremely welcomed.

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• Creating a Stack Overflow notifier

  - by Trey

  I could not find a Stack Overflow notifier Android app so I am planning on making one. I hope that my app will serve a similar purpose as the Stack Overflow Notifier Chrome extension. This will be my first Android app so I am still unfamiliar with the platform. My main concern when creating this app is, what is the proper way to access the user's Recent Activity page? I thought of two different approaches but I'm not sure how to implement either one: Make the user login to Stack Overflow through the Browser application or an embedded browser and scrape their recent activity page occasionally for updates. Ask the user for their username and password and forward this information to Stack Overflow for authentication, storing cookies somehow to keep the session active. I think Astrid uses something similar to the first approach, but I haven't been able to figure it out yet from skimming their code. What is the correct way to handle a notification application like this that requires session management?

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• Problem with stack based implementation of function 0x42 of int 0x13

  - by IceCoder

  I'm trying a new approach to int 0x13 (just to learn more about the way the system works): using stack to create a DAP.. Assuming that DL contains the disk number, AX contains the address of the bootable entry in PT, DS is updated to the right segment and the stack is correctly set, this is the code: push DWORD 0x00000000 add ax, 0x0008 mov si, ax push DWORD [ds:(si)] push DWORD 0x00007c00 push WORD 0x0001 push WORD 0x0010 push ss pop ds mov si, sp mov sp, bp mov ah, 0x42 int 0x13 As you can see: I push the dap structure onto the stack, update DS:SI in order to point to it, DL is already set, then set AX to 0x42 and call int 0x13 the result is error 0x01 in AH and obviously CF set. No sectors are transferred. I checked the stack trace endlessly and it is ok, the partition table is ok too.. I cannot figure out what I'm missing... This is the stack trace portion of the disk address packet: 0x000079ea: 10 00 adc %al,(%bx,%si) 0x000079ec: 01 00 add %ax,(%bx,%si) 0x000079ee: 00 7c 00 add %bh,0x0(%si) 0x000079f1: 00 00 add %al,(%bx,%si) 0x000079f3: 08 00 or %al,(%bx,%si) 0x000079f5: 00 00 add %al,(%bx,%si) 0x000079f7: 00 00 add %al,(%bx,%si) 0x000079f9: 00 a0 07 be add %ah,-0x41f9(%bx,%si) I'm using qemu latest version and trying to read from hard drive (0x80), have also tried with a 4bytes alignment for the structure with the same result (CF 1 AH 0x01), the extensions are present.

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• stack implementation in C

  - by khurshid

  i want to implement stack in C. plz any one can help me

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• NSMutableArray Vs Stack

  - by Chandan Shetty SP

  I am developing 2D game for iphone in Objectice-C.In this project I need to use stack, I can do it using STL(Standard template library) stacks or NSMutableArray, since this stack is widely used in the game which one is more efficient? @interface CarElement : NSObject { std::stack<myElement*> *mBats; } or @interface CarElement : NSObject { NSMutableArray *mBats; } Thanks,

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• how to build website like stack overflow

  - by test

  I want to create website like stack overflow what do I need

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• Implementing a Stack using Test-Driven Development

  - by devoured elysium

  I am doing my first steps with TDD. The problem is (as probably with everyone starting with TDD), I never know very well what kind of unit tests to do when I start working in my projects. Let's assume I want to write a Stack class with the following methods(I choose it as it's an easy example): Stack<T> - Push(element : T) - Pop() : T - Seek() : T - Count : int - IsEmpty : boolean How would you approch this? I never understood if the idea is to test a few corner cases for each method of the Stack class or start by doing a few "use cases" with the class, like adding 10 elements and removing them. What is the idea? To make code that uses the Stack as close as possible to what I'll use in my real code? Or just make simple "add one element" unit tests where I test if IsEmpty and Count were changed by adding that element? How am I supposed to start with this?

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• What causes "Error C stack overflow" in haskell usually

  - by Pradeep

  What causes "Error C stack overflow" in haskell usually

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• How to determine values saved on the stack?

  - by Brian

  I'm doing some experimenting and would like to be able to see what is saved on the stack during a system call (the saved state of the user land process). According to http://lxr.linux.no/#linux+v2.6.30.1/arch/x86/kernel/entry_32.S it shows that the various values of registers are saved at those particular offsets to the stack pointer. Here is the code I have been trying to use to examine what is saved on the stack (this is in a custom system call I have created): asm("movl 0x1C(%esp), %ecx"); asm("movl %%ecx, %0" : "=r" (value)); where value is an unsigned long. As of right now, this value is not what is expected (it is showing a 0 is saved for the user value of ds). Am I correctly accessing the offset of the stack pointer? Another possibility might be could I use a debugger such as GDB to examine the stack contents while in the kernel? I don't have much extensive use with debugging and am not sure of how to debug code inside the kernel. Any help is much appreciated.

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• Unable to get values in ftl from value stack in custom Result Type

  - by Nagadev

  Hello, I am unable retrieve value from value stack in FTL file. Here is the code. Action class holds a property called 'name' private String name; public String getName() { return name; } public void setName(String name) { this.name = name; } public String execute(){ setName("From value stack .. "); return SUCCESS; } FTL code: ${name} Custom result Type deExecute Method Configuration configuration = new Configuration(); String templatePath = "/ftl"; ServletContext context = ServletActionContext.getServletContext(); configuration.setServletContextForTemplateLoading(context, templatePath); configuration.setObjectWrapper(new DefaultObjectWrapper()); Template template = configuration.getTemplate("sample.ftl"); OutputStreamWriter out = new OutputStreamWriter(System.out); template.process(ActionContext.getContext().getValueStack(), out); I am passing the value Stack which contains recently executed Action as well. But FTL is throwing an exception Expression name is undefined on line 1, column 3 in sample.ftl I tried with passing session instead of value stack and I could get the value in FTL. Please suggest me a way to get values from Action class to FTL from value stack. Thanks inadvance.

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• Stack trace with incorrect line number

  - by adrianbanks

  Why would a stack trace show "line 0", but only for one frame in the stack trace? eg. ... at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior) at System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader() at My.LibraryA.Some.Method():line 16 at My.LibraryB.Some.OtherMethod():line 0 at My.LibraryB.Some.Method():line 22 at My.LibraryA.Some.Method():line 10 Background: I have an application that is failing with an exception, and is logging a stack trace to its log file. When the applciation was built, all assemblies were compiled with full debug info (Project Properties - Build - Advanced - Debug Info - Full), and so PDB files were generated. To help me diagnose where the error is coming from, I dropped the PDB files into the application's bin directory, and reproduced the exception. All line numbers for each stack frame look correct, with the exception of one which displays "line 0" as its source.

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• OpenGL: Implementing transformation matrix stack

  - by Jakub M.

  In a newer OpenGL there is no matrix stack. I am working on a simple display engine, and I am going to implement the transformation stack. What is a common strategy here? Should I build a push/pop stack, and use it with a tree representing my model? I suppose this is the "old" approach, that was deprecated in the newer OpenGL versions. Maybe then it is not the best solution (it was removed for some reason)

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• infix operation to postfix using stacks

  - by Chris De La O

  We are writing a program that needs to convert an infix operation (4 5/3) to postfix (4 5 3 / ) using stacks. however my convert to postfix does not work as it doesnt not output the postFix array that is supposed to store the conversion from infix notation to postfix notation. here is the code for the convertToPostix fuction. //converts infix expression to postfix expression void ArithmeticExpression::convertToPostfix(char *const inFix, char *const postFix) { //create a stack2 object named cow Stack2<char> cow; cout<<postFix; char thing = '('; //push a left parenthesis onto the stack cow.push(thing); //append a right parenthesis to the end of inFix array strcat(inFix, ")"); int i = 0;//declare an int that will control posFix position //if the stack is not empty if (!cow.isEmpty()) { //loop to run until the last character in inFix array for (int x = 0; inFix[x]!= '\0'; x++ ) { //if the inFix element is a digit if (isdigit(inFix[x])) { postFix[i]=inFix[x];//it is assigned to the next element in postFix array i++;//move on to next element in postFix } //if the inFix element is a left parenthesis else if (inFix[x]=='(') { cow.push(inFix[x]);//push it unto the stack } //if the inFix element is an operator else if (isOperator(inFix[x])) { char oper2 = inFix[x];//char variable holds inFix operator if (isOperator(cow.stackTop()))//if the top node in the stack is an operator { while (isOperator(cow.stackTop()))//and while the top node in the stack is an operator { char oper1 = cow.stackTop();//char variable holds node operator if(precedence( oper1, oper2))//if the node operator has higher presedence than node operator { postFix[i] = cow.pop();//we pop such operator and insert it in postFix array's next element cow.push(inFix[x]);//and push inFix operator unto the stack i++;//move to the next element in posFix } } } //if the top node is not an operator //we push the current inFix operator unto the top of the stack else cow.push(inFix[x]); } //if the inFix element is a right parenthesis else if (inFix[x]==')') { //we pop everything in the stack and insert it in postFix //until we arrive at a left paranthesis while (cow.stackTop()!='(') { postFix[i] = cow.pop(); i++; } //we then pop and discard left parenthesis cow.pop(); } } postFix[i]='\0'; //print !!postFix array!! (not stack) print();//code for this is just cout<<postFix; }

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• Is stack address shared by Heap addresses ??

  - by numerical25

  I read On most operating systems, the addresses in memory starts from highest to lowest. So I am wondering if the heap, stack, and global memory all fall under the same ordering..? If I created... pointerType* pointer = new pointerType //creates memory address 0xffffff And then created a local varible on the stack localObject object would localObjects address be 0xfffffe Or is heap and stack ordering completely different.

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• Allocation Target of std::aligned_storage (stack or heap?)

  - by Zenikoder

  I've been trying to get my head around the TR1 addition known as aligned_storage. Whilst reading the following documents N2165, N3190 and N2140 I can't for the life of me see a statement where it clearly describes stack or heap nature of the memory being used. I've had a look at the implementation provided by msvc2010, boost and gcc they all provide a stack based solution centered around the use of a union. In short: Is the memory type (stack or heap) used by aligned_storage implementation defined or is it always meant to be stack based? and, What the is the specific document that defines/determines that?

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• Catching an exception class within a template

  - by Todd Bauer

  I'm having a problem using the exception class Overflow() for a Stack template I'm creating. If I define the class regularly there is no problem. If I define the class as a template, I cannot make my call to catch() work properly. I have a feeling it's simply syntax, but I can't figure it out for the life of me. #include<iostream> #include<exception> using namespace std; template <class T> class Stack { private: T *stackArray; int size; int top; public: Stack(int size) { this->size = size; stackArray = new T[size]; top = 0; } ~Stack() { delete[] stackArray; } void push(T value) { if (isFull()) throw Overflow(); stackArray[top] = value; top++; } bool isFull() { if (top == size) return true; else return false; } class Overflow {}; }; int main() { try { Stack<double> Stack(5); Stack.push( 5.0); Stack.push(10.1); Stack.push(15.2); Stack.push(20.3); Stack.push(25.4); Stack.push(30.5); } catch (Stack::Overflow) { cout << "ERROR! The stack is full.\n"; } return 0; } The problem is in the catch (Stack::Overflow) statement. As I said, if the class is not a template, this works just fine. However, once I define it as a template, this ceases to work. I've tried all sorts of syntaxes, but I always get one of two sets of error messages from the compiler. If I use catch(Stack::Overflow): ch18pr01.cpp(89) : error C2955: 'Stack' : use of class template requires template argument list ch18pr01.cpp(13) : see declaration of 'Stack' ch18pr01.cpp(89) : error C2955: 'Stack' : use of class template requires template argument list ch18pr01.cpp(13) : see declaration of 'Stack' ch18pr01.cpp(89) : error C2316: 'Stack::Overflow' : cannot be caught as the destructor and/or copy constructor are inaccessible EDIT: I meant If I use catch(Stack<double>::Overflow) or any variety thereof: ch18pr01.cpp(89) : error C2061: syntax error : identifier 'Stack' ch18pr01.cpp(89) : error C2310: catch handlers must specify one type ch18pr01.cpp(95) : error C2317: 'try' block starting on line '75' has no catch handlers I simply can not figure this out. Does anyone have any idea?

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• CLR 4.0 inlining policy? (maybe bug with MethodImplOptions.NoInlining)

  - by ControlFlow

  I've testing some new CLR 4.0 behavior in method inlining (cross-assembly inlining) and found some strage results: Assembly ClassLib.dll: using System.Diagnostics; using System; using System.Reflection; using System.Security; using System.Runtime.CompilerServices; namespace ClassLib { public static class A { static readonly MethodInfo GetExecuting = typeof(Assembly).GetMethod("GetExecutingAssembly"); public static Assembly Foo(out StackTrace stack) // 13 bytes { // explicit call to GetExecutingAssembly() stack = new StackTrace(); return Assembly.GetExecutingAssembly(); } public static Assembly Bar(out StackTrace stack) // 25 bytes { // reflection call to GetExecutingAssembly() stack = new StackTrace(); return (Assembly) GetExecuting.Invoke(null, null); } public static Assembly Baz(out StackTrace stack) // 9 bytes { stack = new StackTrace(); return null; } public static Assembly Bob(out StackTrace stack) // 13 bytes { // call of non-inlinable method! return SomeSecurityCriticalMethod(out stack); } [SecurityCritical, MethodImpl(MethodImplOptions.NoInlining)] static Assembly SomeSecurityCriticalMethod(out StackTrace stack) { stack = new StackTrace(); return Assembly.GetExecutingAssembly(); } } } Assembly ConsoleApp.exe using System; using ClassLib; using System.Diagnostics; class Program { static void Main() { Console.WriteLine("runtime: {0}", Environment.Version); StackTrace stack; Console.WriteLine("Foo: {0}\n{1}", A.Foo(out stack), stack); Console.WriteLine("Bar: {0}\n{1}", A.Bar(out stack), stack); Console.WriteLine("Baz: {0}\n{1}", A.Baz(out stack), stack); Console.WriteLine("Bob: {0}\n{1}", A.Bob(out stack), stack); } } Results: runtime: 4.0.30128.1 Foo: ClassLib, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null at ClassLib.A.Foo(StackTrace& stack) at Program.Main() Bar: ClassLib, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null at ClassLib.A.Bar(StackTrace& stack) at Program.Main() Baz: at Program.Main() Bob: ClassLib, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null at Program.Main() So questions are: Why JIT does not inlined Foo and Bar calls as Baz does? They are lower than 32 bytes of IL and are good candidates for inlining. Why JIT inlined call of Bob and inner call of SomeSecurityCriticalMethod that is marked with the [MethodImpl(MethodImplOptions.NoInlining)] attribute? Why GetExecutingAssembly returns a valid assembly when is called by inlined Baz and SomeSecurityCriticalMethod methods? I've expect that it performs the stack walk to detect the executing assembly, but stack will contains only Program.Main() call and no methods of ClassLib assenbly, to ConsoleApp should be returned.

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• iscsitarget suddenly broken after upgrade of the 12.04 Hardware Stack

  - by RapidWebs

  After an upgrade to the latest Hardware Stack using Ubuntu 12.04, my iscsi service is not longer operational. The error from the service is such: FATAL: Module iscsi_trgt not found. I have learned that I might need to reinstall the package iscsitarget-dkms. this package builds a driver or something during installation, from source. During this build process, it reports and error, and now has also broke my package manager. Here is the relevant output: Building module: cleaning build area.... make KERNELRELEASE=3.13.0-34-generic -C /lib/modules/3.13.0-34-generic/build M=/var/lib/dkms/iscsitarget/1.4.20.2/build........(bad exit status: 2) Error! Bad return status for module build on kernel: 3.13.0-34-generic (i686) Consult /var/lib/dkms/iscsitarget/1.4.20.2/build/make.log for more information. Errors were encountered while processing: iscsitarget E: Sub-process /usr/bin/dpkg returned an error code (1) and this is the information provided by make.log: or iscsitarget-1.4.20.2 for kernel 3.13.0-34-generic (i686) Fri Aug 15 22:07:15 EDT 2014 make: Entering directory /usr/src/linux-headers-3.13.0-34-generic LD /var/lib/dkms/iscsitarget/1.4.20.2/build/built-in.o LD /var/lib/dkms/iscsitarget/1.4.20.2/build/kernel/built-in.o CC [M] /var/lib/dkms/iscsitarget/1.4.20.2/build/kernel/tio.o CC [M] /var/lib/dkms/iscsitarget/1.4.20.2/build/kernel/iscsi.o CC [M] /var/lib/dkms/iscsitarget/1.4.20.2/build/kernel/nthread.o CC [M] /var/lib/dkms/iscsitarget/1.4.20.2/build/kernel/wthread.o /var/lib/dkms/iscsitarget/1.4.20.2/build/kernel/wthread.c: In function ‘worker_thread’: /var/lib/dkms/iscsitarget/1.4.20.2/build/kernel/wthread.c:73:28: error: void value not ignored as it ought to be /var/lib/dkms/iscsitarget/1.4.20.2/build/kernel/wthread.c:74:3: error: implicit declaration of function ‘get_io_context’ [-Werror=implicit-function-declaration] /var/lib/dkms/iscsitarget/1.4.20.2/build/kernel/wthread.c:74:21: warning: assignment makes pointer from integer without a cast [enabled by default] cc1: some warnings being treated as errors make[2]: * [/var/lib/dkms/iscsitarget/1.4.20.2/build/kernel/wthread.o] Error 1 make[1]: * [/var/lib/dkms/iscsitarget/1.4.20.2/build/kernel] Error 2 make: * [module/var/lib/dkms/iscsitarget/1.4.20.2/build] Error 2 make: Leaving directory `/usr/src/linux-headers-3.13.0-34-generic' I am at a loss on how to resolve this issue. any help would be appreciated!

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• Authenticating clients in the new WCF Http stack

  - by cibrax

  About this time last year, I wrote a couple of posts about how to use the “Interceptors” from the REST starker kit for implementing several authentication mechanisms like “SAML”, “Basic Authentication” or “OAuth” in the WCF Web programming model. The things have changed a lot since then, and Glenn finally put on our hands a new version of the Web programming model that deserves some attention and I believe will help us a lot to build more Http oriented services in the .NET stack. What you can get today from wcf.codeplex.com is a preview with some cool features like Http Processors (which I already discussed here), a new and improved version of the HttpClient library, Dependency injection and better TDD support among others. However, the framework still does not support an standard way of doing client authentication on the services (This is something planned for the upcoming releases I believe). For that reason, moving the existing authentication interceptors to this new programming model was one of the things I did in the last few days. In order to make authentication simple and easy to extend,  I first came up with a model based on what I called “Authentication Interceptors”. An authentication interceptor maps to an existing Http authentication mechanism and implements the following interface, public interface IAuthenticationInterceptor{ string Scheme { get; } bool DoAuthentication(HttpRequestMessage request, HttpResponseMessage response, out IPrincipal principal);} An authentication interceptors basically needs to returns the http authentication schema that implements in the property “Scheme”, and implements the authentication mechanism in the method “DoAuthentication”. As you can see, this last method “DoAuthentication” only relies on the HttpRequestMessage and HttpResponseMessage classes, making the testing of this interceptor very simple (There is no need to do some black magic with the WCF context or messages). After this, I implemented a couple of interceptors for supporting basic authentication and brokered authentication with SAML (using WIF) in my services. The following code illustrates how the basic authentication interceptors looks like. public class BasicAuthenticationInterceptor : IAuthenticationInterceptor{ Func<UsernameAndPassword, bool> userValidation; string realm;  public BasicAuthenticationInterceptor(Func<UsernameAndPassword, bool> userValidation, string realm) { if (userValidation == null) throw new ArgumentNullException("userValidation");  if (string.IsNullOrEmpty(realm)) throw new ArgumentNullException("realm");  this.userValidation = userValidation; this.realm = realm; }  public string Scheme { get { return "Basic"; } }  public bool DoAuthentication(HttpRequestMessage request, HttpResponseMessage response, out IPrincipal principal) { string[] credentials = ExtractCredentials(request); if (credentials.Length == 0 || !AuthenticateUser(credentials[0], credentials[1])) { response.StatusCode = HttpStatusCode.Unauthorized; response.Content = new StringContent("Access denied"); response.Headers.WwwAuthenticate.Add(new AuthenticationHeaderValue("Basic", "realm=" + this.realm));  principal = null;  return false; } else { principal = new GenericPrincipal(new GenericIdentity(credentials[0]), new string[] {});  return true; } }  private string[] ExtractCredentials(HttpRequestMessage request) { if (request.Headers.Authorization != null && request.Headers.Authorization.Scheme.StartsWith("Basic")) { string encodedUserPass = request.Headers.Authorization.Parameter.Trim();  Encoding encoding = Encoding.GetEncoding("iso-8859-1"); string userPass = encoding.GetString(Convert.FromBase64String(encodedUserPass)); int separator = userPass.IndexOf(':');  string[] credentials = new string[2]; credentials[0] = userPass.Substring(0, separator); credentials[1] = userPass.Substring(separator + 1);  return credentials; }  return new string[] { }; }  private bool AuthenticateUser(string username, string password) { var usernameAndPassword = new UsernameAndPassword { Username = username, Password = password };  if (this.userValidation(usernameAndPassword)) { return true; }  return false; }} This interceptor receives in the constructor a callback in the form of a Func delegate for authenticating the user and the “realm”, which is required as part of the implementation. The rest is a general implementation of the basic authentication mechanism using standard http request and response messages. I also implemented another interceptor for authenticating a SAML token with WIF. public class SamlAuthenticationInterceptor : IAuthenticationInterceptor{ SecurityTokenHandlerCollection handlers = null;  public SamlAuthenticationInterceptor(SecurityTokenHandlerCollection handlers) { if (handlers == null) throw new ArgumentNullException("handlers");  this.handlers = handlers; }  public string Scheme { get { return "saml"; } }  public bool DoAuthentication(HttpRequestMessage request, HttpResponseMessage response, out IPrincipal principal) { SecurityToken token = ExtractCredentials(request);  if (token != null) { ClaimsIdentityCollection claims = handlers.ValidateToken(token);  principal = new ClaimsPrincipal(claims);  return true; } else { response.StatusCode = HttpStatusCode.Unauthorized; response.Content = new StringContent("Access denied");  principal = null;  return false; } }  private SecurityToken ExtractCredentials(HttpRequestMessage request) { if (request.Headers.Authorization != null && request.Headers.Authorization.Scheme == "saml") { XmlTextReader xmlReader = new XmlTextReader(new StringReader(request.Headers.Authorization.Parameter));  var col = SecurityTokenHandlerCollection.CreateDefaultSecurityTokenHandlerCollection(); SecurityToken token = col.ReadToken(xmlReader);  return token; }  return null; }}This implementation receives a “SecurityTokenHandlerCollection” instance as part of the constructor. This class is part of WIF, and basically represents a collection of token managers to know how to handle specific xml authentication tokens (SAML is one of them). I also created a set of extension methods for injecting these interceptors as part of a service route when the service is initialized. var basicAuthentication = new BasicAuthenticationInterceptor((u) => true, "ContactManager");var samlAuthentication = new SamlAuthenticationInterceptor(serviceConfiguration.SecurityTokenHandlers); // use MEF for providing instancesvar catalog = new AssemblyCatalog(typeof(Global).Assembly);var container = new CompositionContainer(catalog);var configuration = new ContactManagerConfiguration(container); RouteTable.Routes.AddServiceRoute<ContactResource>("contact", configuration, basicAuthentication, samlAuthentication);RouteTable.Routes.AddServiceRoute<ContactsResource>("contacts", configuration, basicAuthentication, samlAuthentication); In the code above, I am injecting the basic authentication and saml authentication interceptors in the “contact” and “contacts” resource implementations that come as samples in the code preview. I will use another post to discuss more in detail how the brokered authentication with SAML model works with this new WCF Http bits. The code is available to download in this location.

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