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• should std::auto_ptr<>::operator = reset / deallocate its existing pointee ?

  - by afriza

  I read here about std::auto_ptr<::operator= Notice however that the left-hand side object is not automatically deallocated when it already points to some object. You can explicitly do this by calling member function reset before assigning it a new value. However, when I read the source code for header file C:\Program Files\Microsoft Visual Studio 8\VC\ce\include\memory template<class _Other> auto_ptr<_Ty>& operator=(auto_ptr<_Other>& _Right) _THROW0() { // assign compatible _Right (assume pointer) reset(_Right.release()); return (*this); } auto_ptr<_Ty>& operator=(auto_ptr<_Ty>& _Right) _THROW0() { // assign compatible _Right (assume pointer) reset(_Right.release()); return (*this); } auto_ptr<_Ty>& operator=(auto_ptr_ref<_Ty> _Right) _THROW0() { // assign compatible _Right._Ref (assume pointer) _Ty **_Pptr = (_Ty **)_Right._Ref; _Ty *_Ptr = *_Pptr; *_Pptr = 0; // release old reset(_Ptr); // set new return (*this); } What is the correct/standard behavior? How do other STL implementations behave?

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• What's correct way to remove a boost::shared_ptr from a list?

  - by Catskul

  I have a std::list of boost::shared_ptr<T> and I want to remove an item from it but I only have a pointer of type T* which matches one of the items in the list. However I cant use myList.remove( tPtr ) I'm guessing because shared_ptr does not implement == for its template argument type. My immediate thought was to try myList.remove( shared_ptr<T>(tPtr) ) which is syntactically correct but it will crash from a double delete since the temporary shared_ptr has a separate use_count. std::list< boost::shared_ptr<T> > myList; T* tThisPtr = new T(); // This is wrong; only done for example code. // stand-in for actual code in T using // T's actual "this" pointer from within T { boost::shared_ptr<T> toAdd( tThisPtr ); // typically would be new T() myList.push_back( toAdd ); } { //T has pointer to myList so that upon a certain action, // it will remove itself romt the list //myList.remove( tThisPtr); //doesn't compile myList.remove( boost::shared_ptr<T>(tThisPtr) ); // compiles, but causes // double delete } The only options I see remaining are to use std::find with a custom compare, or to loop through the list brute force and find it myself, but it seems there should be a better way. Am I missing something obvious, or is this just too non-standard a use to be doing a remove the clean/normal way?

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• Databinding to Classmember of Classmember

  - by Walter

  Hello, I need some help about WPF and Databinding. Let's say I have a ClassA with a member of ClassB. ClassB has again a member, maybe an int: ClassB { public int MemberOfB { get; set; } } ClassA { private ClassB _theB; public ClassB MemberOfA { get {return _theB;} set { _theB = value; // Need to do something here... } } } When I have a Databinding in XAML like this: <TextBox Text="{Binding Path=MemberOfA.MemberOfB}"/> Where the Datacontext of the Textbox is an object of type ClassA. As you can see, i need to do some computations in the setter of MemberOfA in ClassA. But with the databinding above, this setter is of course never called, because it binds to the member of ClassB. So, how can i get to be informed if the MemberOfA changes (when I Type something into the Textbox)? Are there any best practices? (Didn't check the code in Visual Studio, so there may be some syntax errors). Thanks, Walter

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• ASP.NET MVC 2 VB, Not recognising my import.

  - by SLC

  I had a problem with a project I converted from C# to VB, in that the VB version it cannot seem to find an object even though I declared it with an Import statement at the top. I created a new, default MVC 2 VB project, and the same problem occurs there. I create a new MVC 2 application, I then add a reference to System.Data.Services.Client, and in my Index.aspx, in the Content area, I type <% Dim x As DataServiceQueryContinuation %> which is what I want to use. It gives me a blue squiggly line and says Type 'DataServiceQueryContinuation' is not defined. At the top of the page, I add this: <%@ Import Namespace="System.Data.Services.Client" %> The error persists. My original C# version has no such error. I also get this warning: Warning 2 Namespace or type specified in the Imports 'System.Data.Services.Client' doesn't contain any public member or cannot be found. Make sure the namespace or the type is defined and contains at least one public member. Make sure the imported element name doesn't use any aliases. e:\ASPNETDEBUG\MvcApplication1\MvcApplication1\Views\Home\Index.aspx 10 9 MvcApplication1 Examining the DLL using the tool provided shows that it does have a public member. Also when typing the above, System.Data. provides intellisense but there is no 'Services'. Any ideas?

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• Modifying NSMutableDictionary from a single index format into nested (array within array)

  - by Michael Robinson

  I need to take the member ID off the top of this and create an array inside that contains the rest of the JSON return. Here is my JSON return. [{"F_Name_VC":"Frank", "L_Name_VC":"Johnson", "userid":"18", "age":"23", },] After it is json-deserialized it looks like this: I need convert it to be transformed into this, with children sub-array: Someone else posted a similar question but without the fact that it was coming from a JSON deserialization. There were two answers but no conclusion to the question. (Answer 1): NSDictionary *item1 = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:@" member",[NSNumber numberWithInt:3],nil] forKeys:[NSArray arrayWithObjects:@"Title",@"View",nil]]; Answer (2): NSMutableArray *Rows = [NSMutableArray arrayWithCapacity: 1]; for (int i = 0; i < 4; ++i) { NSMutableArray *theChildren = [NSMutableArray arrayWithCapacity: 1]; [theChildren addObject: [NSString stringWithFormat: @"tester %d", i]]; NSString *aTitle = [NSString stringWithFormat: @"Item %d", i]; NSDictionary *anItem = [NSDictionary dictionaryWithObjectsAndKeys: aTitle, @"Title", theChildren, @"Children"]; [Rows addObject: anItem]; } NSDictionary *Root = [NSDictionary withObject: Rows andKey: @"Rows"]; Here is my JSON return and save code: NSData *jsonData = [jsonreturn dataUsingEncoding:NSUTF32BigEndianStringEncoding]; NSError *error = nil; NSDictionary * dict = [[CJSONDeserializer deserializer] deserializeAsDictionary:jsonData error:&error]; if (dict) { rowsArray = [dict objectForKey:@"member"]; [rowsArray retain]; } Thanks in advance. Every tutorial on JSON only shows a simple array being returned, never with children..It's driving me crazy trying to figure this out.

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• What is the correct JNA mapping for UniChar on Mac OS X?

  - by Trejkaz

  I have a C struct like this: struct HFSUniStr255 { UInt16 length; UniChar unicode[255]; }; I have mapped this in the expected way: public class HFSUniStr255 extends Structure { public UInt16 length; // UInt16 is just an IntegerType with length 2 for convenience. public /*UniChar*/ char[] unicode = new char[255]; //public /*UniChar*/ byte[] unicode = new byte[255*2]; //public /*UniChar*/ UInt16[] unicode = new UInt16[255]; public HFSUniStr255() { } public HFSUniStr255(Pointer pointer) { super(pointer); } } If I use this version, I get every second character of the string into my char[] ("aits D" for "Macintosh HD".) I am assuming that this is something to do with being on a 64-bit platform and JNA mapping the value to a 32-bit wchar_t but then chopping off the high 16 bits on each wchar_t on copying them back. If I use the byte[] version, I get data which decodes correctly using the UTF-16LE charset. If I use the UInt16[] version, I get the right code point for each character but it is then inconvenient to convert them back into a string. Is there some way I can define my type as char[], and yet have it convert correctly?

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• COM-Objects containing maps / content error(0)

  - by Florian Berzsenyi

  I'm writing a small wrapper to get familiar with some important topics in C++ (WinAPI, COM, STL,OOP). For now, my class shall be able to create a (child) window. Mainly, this window is connected to a global message loop that distribute messages to a local loop of the right instance (global is static, local is virtual). Obviously, there are surely better ways to do that but I'm using std::maps to store HWND and their instance pointer in pairs (the Global loop looks for the pointer with the HWND-parameter, gets itself the pointer from the map and calls then the local loop). Now, it appears that the map does not accept any values because of a unknown reason. It seems to allocate enough space but something went wrong anyway [ (error) 0 is displayed instead of the entries in visual C++). I've looked that up in google as well and found out that maps cause some trouble when used in classes AND DLLs. May this be the reason and is there any solution?? Protected scope of class: static std::map<HWND,MAP_BASE_OBJECT*> m_LoopBuf Implementation in .cpp-file: std::map<HWND,MAP_BASE_OBJECT*> HWindow::m_LoopBuf;

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• Qt/C++, Problems with large QImage

  - by David Günzel

  I'm pretty new to C++/Qt and I'm trying to create an application with Visual Studio C++ and Qt (4.8.3). The application displays images using a QGraphicsView, I need to change the images at pixel level. The basic code is (simplified): QImage* img = new QImage(img_width,img_height,QImage::Format_RGB32); while(do_some_stuff) { img->setPixel(x,y,color); } QGraphicsPixmapItem* pm = new QGraphicsPixmapItem(QPixmap::fromImage(*img)); QGraphicsScene* sc = new QGraphicsScene; sc->setSceneRect(0,0,img->width(),img->height()); sc->addItem(pm); ui.graphicsView->setScene(sc); This works well for images up to around 12000x6000 pixel. The weird thing happens beyond this size. When I set img_width=16000 and img_height=8000, for example, the line img = new QImage(...) returns a null image. The image data should be around 512,000,000 bytes, so it shouldn't be too large, even on a 32 bit system. Also, my machine (Win 7 64bit, 8 GB RAM) should be capable of holding the data. I've also tried this version: uchar* imgbuf = (uchar*) malloc(img_width*img_height*4); QImage* img = new QImage(imgbuf,img_width,img_height,QImage::Format_RGB32); At first, this works. The img pointer is valid and calling img-width() for example returns the correct image width (instead of 0, in case the image pointer is null). But as soon as I call img-setPixel(), the pointer becomes null and img-width() returns 0. So what am I doing wrong? Or is there a better way of modifying large images on pixel level? Regards, David

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• Defining an implementation independent version of the global object in JavaScript

  - by Aadit M Shah

  I'm trying to define the global object in JavaScript in a single line as follows: var global = this.global || this; The above statement is in the global scope. Hence in browsers the this pointer is an alias for the window object. Assuming that it's the first line of JavaScript to be executed in the context of the current web page, the value of global will always be the same as that of the this pointer or the window object. In CommonJS implementations, such as RingoJS and node.js the this pointer points to the current ModuleScope. However, we can access the global object through the property global defined on the ModuleScope. Hence we can access it via the this.global property. Hence this code snippet works in all browsers and in at least RingoJS and node.js, but I have not tested other CommomJS implementations. Thus I would like to know if this code will not yield correct results when run on any other CommonJS implementation, and if so how I may fix it. Eventually, I intend to use it in a lambda expression for my implementation independent JavaScript framework as follows (idea from jQuery): (function (global) { // javascript framework })(this.global || this);

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• Common lisp, CFFI, and instantiating c structs

  - by andrew

  Hi, I've been on google for about, oh, 3 hours looking for a solution to this "problem." I'm trying to figure out how to instantiate a C structure in lisp using CFFI. I have a struct in c: struct cpVect{cpFloat x,y;} Simple right? I have auto-generated CFFI bindings (swig, I think) to this struct: (cffi:defcstruct #.(chipmunk-lispify "cpVect" 'classname) (#.(chipmunk-lispify "x" 'slotname) :double) (#.(chipmunk-lispify "y" 'slotname) :double)) This generates a struct "VECT" with slots :X and :Y, which foreign-slot-names confirms (please note that I neither generated the bindings or programmed the C library (chipmunk physics), but the actual functions are being called from lisp just fine). I've searched far and wide, and maybe I've seen it 100 times and glossed over it, but I cannot figure out how to create a instance of cpVect in lisp to use in other functions. Note the function: cpShape *cpPolyShapeNew(cpBody *body, int numVerts, cpVect *verts, cpVect offset) Takes not only a cpVect, but also a pointer to a set of cpVects, which brings me to my second question: how do I create a pointer to a set of structs? I've been to http://common-lisp.net/project/cffi/manual/html_node/defcstruct.html and tried the code, but get "Error: Unbound variable: PTR" (I'm in Clozure CL), not to mention that looks to only return a pointer, not an instance. I'm new to lisp, been going pretty strong so far, but this is the first real problem I've hit that I can't figure out. Thanks!

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• Modify static variables while debugging in Eclipse

  - by sleske

  As an extension the the question "Modify/view static variables while debugging in Eclipse", I'd like to be able to modify static variables while debugging in Eclipse. For instance and local variables, I can just choose the variable in the "Variables" view of Eclipse, and use the context menu "Change value..." to change the value. This is not possible for arbitrary static variables, because they do not appear in the "Variables" view. What I tried: If you choose "Java / Show static variables" from the triangle menu in the "Variables" view, you can see and modify static member variables of the variables listed in the "Variables view". However, I did not find how to access a static member of a class whose instance does not appear in the "Variables view". You can of course enter a static member as an expression into the "Expression view" (using fully qualified name). Then you can see the value, but the "Expression view" does not have an option to modify the value (it does allow to modify members of an expression, but not the expression itself, even if the expression is a field). So, if I have a static variable like a boolean MyClass.disableAllBugs, is there a way to change MyClass.disableAllBugs during debugging? As an aside: I realize that even having public mutable static fields (i.e. mutable global variables) is very bad style. But some codebases have it, and then it's sometimes useful to modify it while debugging.

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• Access cost of dynamically created objects with dynamically allocated members

  - by user343547

  I'm building an application which will have dynamic allocated objects of type A each with a dynamically allocated member (v) similar to the below class class A { int a; int b; int* v; }; where: The memory for v will be allocated in the constructor. v will be allocated once when an object of type A is created and will never need to be resized. The size of v will vary across all instances of A. The application will potentially have a huge number of such objects and mostly need to stream a large number of these objects through the CPU but only need to perform very simple computations on the members variables. Could having v dynamically allocated could mean that an instance of A and its member v are not located together in memory? What tools and techniques can be used to test if this fragmentation is a performance bottleneck? If such fragmentation is a performance issue, are there any techniques that could allow A and v to allocated in a continuous region of memory? Or are there any techniques to aid memory access such as pre-fetching scheme? for example get an object of type A operate on the other member variables whilst pre-fetching v. If the size of v or an acceptable maximum size could be known at compile time would replacing v with a fixed sized array like int v[max_length] lead to better performance? The target platforms are standard desktop machines with x86/AMD64 processors, Windows or Linux OSes and compiled using either GCC or MSVC compilers.

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• What are the use cases for this static reflection code?

  - by Maslow

  This is Oliver Hanappi's static reflection code he posted on stackoverflow private static string GetMemberName(Expression expression) { switch (expression.NodeType) { case ExpressionType.MemberAccess: var memberExpression = (MemberExpression)expression; var supername = GetMemberName(memberExpression.Expression); if (String.IsNullOrEmpty(supername)) return memberExpression.Member.Name; return String.Concat(supername, '.', memberExpression.Member.Name); case ExpressionType.Call: var callExpression = (MethodCallExpression)expression; return callExpression.Method.Name; case ExpressionType.Convert: var unaryExpression = (UnaryExpression)expression; return GetMemberName(unaryExpression.Operand); case ExpressionType.Parameter: return String.Empty; default: throw new ArgumentException("The expression is not a member access or method call expression"); } } I have the public wrapper methods: public static string Name<T>(Expression<Action<T>> expression) { return GetMemberName(expression.Body); } public static string Name<T>(Expression<Func<T, object>> expression) { return GetMemberName(expression.Body); } then added my own method shortcuts public static string ClassMemberName<T>(this T sourceType,Expression<Func<T,object>> expression) { return GetMemberName(expression.Body); } public static string TMemberName<T>(this IEnumerable<T> sourceList, Expression<Func<T,object>> expression) { return GetMemberName(expression.Body); } What are examples of code that would necessitate or take advantage of the different branches in the GetMemberName(Expression expression) switch? what all is this code capable of making strongly typed?

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• Extension methods for encapsulation and reusability

  - by tzaman

  In C++ programming, it's generally considered good practice to "prefer non-member non-friend functions" instead of instance methods. This has been recommended by Scott Meyers in this classic Dr. Dobbs article, and repeated by Herb Sutter and Andrei Alexandrescu in C++ Coding Standards (item 44); the general argument being that if a function can do its job solely by relying on the public interface exposed by the class, it actually increases encapsulation to have it be external. While this confuses the "packaging" of the class to some extent, the benefits are generally considered worth it. Now, ever since I've started programming in C#, I've had a feeling that here is the ultimate expression of the concept that they're trying to achieve with "non-member, non-friend functions that are part of a class interface". C# adds two crucial components to the mix - the first being interfaces, and the second extension methods: Interfaces allow a class to formally specify their public contract, the methods and properties that they're exposing to the world. Any other class can choose to implement the same interface and fulfill that same contract. Extension methods can be defined on an interface, providing any functionality that can be implemented via the interface to all implementers automatically. And best of all, because of the "instance syntax" sugar and IDE support, they can be called the same way as any other instance method, eliminating the cognitive overhead! So you get the encapsulation benefits of "non-member, non-friend" functions with the convenience of members. Seems like the best of both worlds to me; the .NET library itself providing a shining example in LINQ. However, everywhere I look I see people warning against extension method overuse; even the MSDN page itself states: In general, we recommend that you implement extension methods sparingly and only when you have to. So what's the verdict? Are extension methods the acme of encapsulation and code reuse, or am I just deluding myself?

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• Django Database design -- Is this a good stragety for overriding defaults

  - by rh0dium

  Hi SO's I have a question on good database design practices and I would like to leverage you guys for pointers. The project started out simple. Hey we have a bunch of questions we want answered for every project (no problem) Which turned into... Hey we have so many questions can we group them into sections (yup we can do that) Which lead into.. Can we weight these questions and I don't really want some of these questions for my project (Yes but we are getting difficult) And then I'm thinking they will want to have each section have it's own weight.. Requirements So there's the requirements - For n number of project Allow a admin member the ability select the questions for a project Allow the admin member to re-weigh or use the default weights for the questions Allow the admin member to re-weight the sections Allow team members to answer the questions. So here is what I came up with. Please feel free to comment and provide better examples models.py from django.db import models from django.contrib.sites.models import Site from django.conf import settings class Section(models.Model): """ This describes the various sections for a checklist: """ name = models.CharField(max_length=64) description = models.TextField() class Question(models.Model): """ This simply provides a simple way to list out the questions. """ question = models.CharField(max_length=255) answer_type = models.CharField(max_length=16) description = models.TextField() section = models.ForeignKey(Section) class ProjectQuestion(models.Model): """ These are the questions relevant to the project """ question = models.ForeignKey(Question) answer = models.CharField(max_length=255) required = models.BooleanField(default=True) weight = models.FloatField(default = XXX) class Project(models.Model): """ Here is where we want to gather our questions """ questions = models.ManyToManyField(ProjectQuestion) Immediate questions: - When I start a project - any ideas on how to "pre-populate" the questions (and ultimately the weights) for the project? - Is there a generally accepted method for doing this process that I am missing? Basically the idea that you refer to the questions overide your own default weight, and store the answer? - It appears that a good chuck of the work will be done in the views and that a lot of checking will need to occur there? Is that OK? Again - feel free to give me better strategies!! Thanks

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• The Implications of Modern Day Software Development Abstractions

  - by Andreas Grech

  I am currently doing a dissertation about the implications or dangers that today's software development practices or teachings may have on the long term effects of programming. Just to make it clear: I am not attacking the use abstractions in programming. Every programmer knows that abstractions are the bases for modularity. What I want to investigate with this dissertation are the positive and negative effects abstractions can have in software development. As regards the positive, I am sure that I can find many sources that can confirm this. But what about the negative effects of abstractions? Do you have any stories to share that talk about when certain abstractions failed on you? The main concern is that many programmers today are programming against abstractions without having the faintest idea of what the abstraction is doing under-the-covers. This may very well lead to bugs and bad design. So, in you're opinion, how important is it that programmers actually know what is going below the abstractions? Taking a simple example from Joel's Back to Basics, C's strcat: void strcat( char* dest, char* src ) { while (*dest) dest++; while (*dest++ = *src++); } The above function hosts the issue that if you are doing string concatenation, the function is always starting from the beginning of the dest pointer to find the null terminator character, whereas if you write the function as follows, you will return a pointer to where the concatenated string is, which in turn allows you to pass this new pointer to the concatenation function as the *dest parameter: char* mystrcat( char* dest, char* src ) { while (*dest) dest++; while (*dest++ = *src++); return --dest; } Now this is obviously a very simple as regards abstractions, but it is the same concept I shall be investigating. Finally, what do you think about the issue that schools are preferring to teach Java instead of C and Lisp ? Can you please give your opinions and your says as regards this subject? Thank you for your time and I appreciate every comment.

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• Help with GetGlyphOutline function(WinAPI)

  - by user146780

  I want to use this function to get contours and within these contours, I want to get cubic bezier. I think I have to call it with GGO_BEZIER. What puzzles me is how the return buffer works. "A glyph outline is returned as a series of one or more contours defined by a TTPOLYGONHEADER structure followed by one or more curves. Each curve in the contour is defined by a TTPOLYCURVE structure followed by a number of POINTFX data points. POINTFX points are absolute positions, not relative moves. The starting point of a contour is given by the pfxStart member of the TTPOLYGONHEADER structure. The starting point of each curve is the last point of the previous curve or the starting point of the contour. The count of data points in a curve is stored in the cpfx member of TTPOLYCURVE structure. The size of each contour in the buffer, in bytes, is stored in the cb member of TTPOLYGONHEADER structure. Additional curve definitions are packed into the buffer following preceding curves and additional contours are packed into the buffer following preceding contours. The buffer contains as many contours as fit within the buffer returned by GetGlyphOutline." I'm really not sure how to access the contours. I know that I can change a pointer another type of pointer but i'm not sure how I go about getting the contours based on this documentation. Thanks

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• Atomic swap in GNU C++

  - by Steve

  I want to verify that my understanding is correct. This kind of thing is tricky so I'm almost sure I am missing something. I have a program consisting of a real-time thread and a non-real-time thread. I want the non-RT thread to be able to swap a pointer to memory that is used by the RT thread. From the docs, my understanding is that this can be accomplished in g++ with: // global Data *rt_data; Data *swap_data(Data *new_data) { #ifdef __GNUC__ // Atomic pointer swap. Data *old_d = __sync_lock_test_and_set(&rt_data, new_data); #else // Non-atomic, cross your fingers. Data *old_d = rt_data; rt_data = new_data; #endif return old_d; } This is the only place in the program (other than initial setup) where rt_data is modified. When rt_data is used in the real-time context, it is copied to a local pointer. For old_d, later on when it is sure that the old memory is not used, it will be freed in the non-RT thread. Is this correct? Do I need volatile anywhere? Are there other synchronization primitives I should be calling? By the way I am doing this in C++, although I'm interested in whether the answer differs for C. Thanks ahead of time.

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• Using generics in F# to create an EnumArray type

  - by Matthew

  I've created an F# class to represent an array that allocates one element for each value of a specific enum. I'm using an explicit constructor that creates a dictionary from enum values to array indices, and an Item property so that you can write expressions like: let my_array = new EnumArray<EnumType, int> my_array.[EnumType.enum_value] <- 5 However, I'm getting the following obscure compilation error at the line marked with '// FS0670' below. error FS0670: This code is not sufficiently generic. The type variable ^e when ^e : enum<int> and ^e : equality and ^e : (static member op_Explicit : ^e -> int) could not be generalized because it would escape its scope. I'm at a loss - can anyone explain this error? type EnumArray< 'e, 'v when 'e : enum<int> and 'e : equality and ^e : (static member op_Explicit : ^e -> int) > = val enum_to_int : Dictionary<'e, int> val a : 'v array new() as this = { enum_to_int = new Dictionary<'e, int>() a = Array.zeroCreate (Enum.GetValues(typeof<'e>).Length) } then for (e : obj) in Enum.GetValues(typeof<'e>) do this.enum_to_int.Add(e :?> 'e, int(e :?> 'e)) member this.Item with get (idx : 'e) : 'v = this.a.[this.enum_to_int.[idx]] // FS0670 and set (idx : 'e) (c : 'v) = this.a.[this.enum_to_int.[idx]] <- c

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• What is the purpose of the s==NULL case for mbrtowc?

  - by R..

  mbrtowc is specified to handle a NULL pointer for the s (multibyte character pointer) argument as follows: If s is a null pointer, the mbrtowc() function shall be equivalent to the call: mbrtowc(NULL, "", 1, ps) In this case, the values of the arguments pwc and n are ignored. As far as I can tell, this usage is largely useless. If ps is not storing any partially-converted character, the call will simply return 0 with no side effects. If ps is storing a partially-converted character, then since '\0' is not valid as the next byte in a multibyte sequence ('\0' can only be a string terminator), the call will return (size_t)-1 with errno==EILSEQ. and leave ps in an undefined state. The intended usage seems to have been to reset the state variable, particularly when NULL is passed for ps and the internal state has been used, analogous to mbtowc's behavior with stateful encodings, but this is not specified anywhere as far as I can tell, and it conflicts with the semantics for mbrtowc's storage of partially-converted characters (if mbrtowc were to reset state when encountering a 0 byte after a potentially-valid initial subsequence, it would be unable to detect this dangerous invalid sequence). If mbrtowc were specified to reset the state variable only when s is NULL, but not when it points to a 0 byte, a desirable state-reset behavior would be possible, but such behavior would violate the standard as written. Is this a defect in the standard? As far as I can tell, there is absolutely no way to reset the internal state (used when ps is NULL) once an illegal sequence has been encountered, and thus no correct program can use mbrtowc with ps==NULL.

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• datareader.close is called in if - else branching. How to validate datareader is actually closed usi

  - by tanmay

  Hi, I have written couple of custom rules in for fxcop 1.36. I have written a code to find weather opened datareader is closed or not. But it does not check which datareader object is calling the close() method so I can't be sure if all opened datareader objs are closed!! 2nd: if I am using data reader in IF else like if 1=2 dr = cmd.executeReader(); else dr = cmd2.execureReader(); end if in this case it will search for 2 datareader objects to be closed.. I am putting my code for more clarity. public override ProblemCollection Check(Member member) { Method method = member as Method; int countCatch =0; int countErrLog = 0; Instruction objInstr = null; if (method != null) { for (int i = 0; i < method.Instructions.Count; i++) { objInstr = method.Instructions[i]; if (objInstr.Value != null) { if (objInstr.Value.ToString().Contains("System.Data.SqlClient.SqlDataReader")) { countCatch += 1; } if (countCatch>0) { if (objInstr.Value.ToString().Contains("System.Data.SqlClient.SqlDataReader.Close")) { countErrLog += 1; } } } } } if (countErrLog!=countCatch) { Resolution resolu = GetResolution(new string[] { method.ToString() }); Problems.Add(new Problem(resolu)); } return Problems; Thanks and regards, Tanmay.

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• Inheritance inside a template - public members become invisible?

  - by Juliano

  I'm trying to use inheritance among classes defined inside a class template (inner classes). However, the compiler (GCC) is refusing to give me access to public members in the base class. Example code: template <int D> struct Space { struct Plane { Plane(Space& b); virtual int& at(int y, int z) = 0; Space& space; /* <= this member is public */ }; struct PlaneX: public Plane { /* using Plane::space; */ PlaneX(Space& b, int x); int& at(int y, int z); const int cx; }; int& at(int x, int y, int z); }; template <int D> int& Space<D>::PlaneX::at(int y, int z) { return space.at(cx, y, z); /* <= but it fails here */ }; Space<4> sp4; The compiler says: file.cpp: In member function ‘int& Space::PlaneX::at(int, int)’: file.cpp:21: error: ‘space’ was not declared in this scope If using Plane::space; is added to the definition of class PlaneX, or if the base class member is accessed through the this pointer, or if class Space is changed to a non-template class, then the compiler is fine with it. I don't know if this is either some obscure restriction of C++, or a bug in GCC (GCC versions 4.4.1 and 4.4.3 tested). Does anyone have an idea?

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• C standard addressing simplification inconsistency

  - by Chris Lutz

  Section §6.5.3.2 "Address and indirection operators" ¶3 says (relevant section only): The unary & operator returns the address of its operand. ... If the operand is the result of a unary * operator, neither that operator nor the & operator is evaluated and the result is as if both were omitted, except that the constraints on the operators still apply and the result is not an lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor the unary * that is implied by the [] is evaluated and the result is as if the & operator were removed and the [] operator were changed to a + operator. ... This means that this: int *i = NULL; printf("%p", (void *) (&*i) ); printf("%p", (void *) (&i[10]) ); Should be perfectly legal, printing the null pointer (probably 0) and the null pointer plus 10 (probably 10). The standard seems very clear that both of those cases are required to be optimized. However, it doesn't seem to require the following to be optimized: struct { int a; short b; } *s = 0; printf("%p", (void *) (&s->b) ); This seems awfully inconsistent. I can see no reason that the above code shouldn't print the null pointer plus sizeof(int) (possibly 4). Simplifying a &-> expression is going to be the same conceptually (IMHO) as &[], a simple address-plus-offset. It's even an offset that's going to be determinable at compile time, rather than potentially runtime with the [] operator. Is there anything in the rationale about why this is so seemingly inconsistent?

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• Best way to determine variable type and treat each one differently in F#

  - by James Black

  I have a function that will create a select where clause, but right now everything has to be a string. I would like to look at the variable passed in and determine what type it is and then treat it properly. For example, numeric values don't have single quotes around them, option type will either be null or have some value and boolean will actually be zero or one. member self.BuildSelectWhereQuery (oldUser:'a) = let properties = List.zip oldUser.ToSqlValuesList sqlColumnList let init = false, new StringBuilder() let anyChange, (formatted:StringBuilder) = properties |> Seq.fold (fun (anyChange, sb) (oldVal, name) -> match(anyChange) with | true -> true, sb.AppendFormat(" AND {0} = '{1}'", name, oldVal) | _ -> true, sb.AppendFormat("{0} = '{1}'", name, oldVal) ) init formatted.ToString() Here is one entity: type CityType() = inherit BaseType() let mutable name = "" let mutable stateId = 0 member this.Name with get() = name and set restnameval=name <- restnameval member this.StateId with get() = stateId and set stateidval=stateId <- stateidval override this.ToSqlValuesList = [this.Name; this.StateId.ToString()] So, if name was some other value besides a string, or stateId can be optional, then I have two changes to make: How do I modify ToSqlValuesList to have the variable so I can tell the variable type? How do I change my select function to handle this? I am thinking that I need a new function does the processing, but what is the best FP way to do this, rather than using something like typeof?

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• Representing element as boolean with JAXB?

  - by Marcus

  We have this XML: <Summary> <ValueA>xxx</ValueA> <ValueB/> </Summary> <ValueB/> will never have any attributes or inner elements. It's a boolean type element - it exists (true) or it doesn't (false). JAXB generated a Summary class with a String valueA member, which is good. But for ValueB, JAXB generated a ValueB inner class and a corresponding member: @XmlElement(name = "ValueB") protected Summary.ValueB valueB; But what I'd like is a boolean member and no inner class: @XmlElement(name = "ValueB") protected boolean valueB; How can you do this? I'm not looking to regenerate the classes, I'd like to just make the code change manually. Update: In line with the accepted answer, we created a new method returning the boolean value conditional on whether valueB == null. As we are using Hibernate, we annotated valueB with @Transient and annotated the boolean getter with Hibernate's @Column annotation.

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