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• How to use a VB usercontrol on a C# page?

  - by ks78

  Hopefully someone will be able to point me in the right direction. I've created a usercontrol in VB that handles paging more efficiently than the DataPager (at least for very large datasets). I'd like to use it in a C# project, but I've been having trouble getting it to work. I've tried simply adding PagingControl.ascx to the C# project, but when I do that the markup and VB code behind don't seem to see each other. --Is this a namespace issue? I've tried adding the PagingControl.ascx to its own VB project, then adding that project to the C# project's solution, as well as a reference. --That almost works. I can register the PagingControl usercontrol in the markup. I can access the usercontrol's properties in the code behind, but any property that involves the UI of the usercontrol fails. Its seems as if the usercontrol's form hasn't had a chance to load by the time the C# page's Page_Load event handler fires. --Maybe this is an "order of operations" problem? At what point in the C# page's lifetime should a usercontrol's form be loaded? If anyone has any ideas or insight, I'd really appreciate it. Thanks in advance.

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• Question about memory allocation when initializing char arrays in C/C++.

  - by Carlos Nunez

  Before anything, I apologize if this question has been asked before. I am programming a simple packet sniffer for a class project. For a little while, I ran into the issue where the source and destination of a packet appeared to be the same. For example, the source and destination of an Ethernet frame would be the same MAC address all of the time. I custom-made ether_ntoa(char *) because Windows does not seem to have ethernet.h like Linux does. Code snippet is below: char *ether_ntoa(u_char etheraddr[ETHER_ADDR_LEN]) { int i, j; char eout[32]; for(i = 0, j = 0; i < 5; i++) { eout[j++] = etheraddr[i] >> 4; eout[j++] = etheraddr[i] & 0xF; eout[j++] = ':'; } eout[j++] = etheraddr[i] >> 4; eout[j++] = etheraddr[i] & 0xF; eout[j++] = '\0'; for(i = 0; i < 17; i++) { if(eout[i] < 10) eout[i] += 0x30; else if(eout[i] < 16) eout[i] += 0x57; } return(eout); } I solved the problem by using malloc() to have the compiler assign memory (i.e. instead of char eout[32], I used char * eout; eout = (char *) malloc (32);). However, I thought that the compiler assigned different memory locations when one sized a char-array at compile time. Is this incorrect? Thanks! Carlos Nunez

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• In a class with no virtual methods or superclass, is it safe to assume (address of first member vari

  - by Jeremy Friesner

  Hi all, I made a private API that assumes that the address of the first member-object in the class will be the same as the class's this-pointer... that way the member-object can trivially derive a pointer to the object that it is a member of, without having to store a pointer explicitly. Given that I am willing to make sure that the container class won't inherit from any superclass, won't have any virtual methods, and that the member-object that does this trick will be the first member object declared, will that assumption hold valid for any C++ compiler, or do I need to use the offsetof() operator (or similar) to guarantee correctness? To put it another way, the code below does what I expect under g++, but will it work everywhere? class MyContainer { public: MyContainer() {} ~MyContainer() {} // non-virtual dtor private: class MyContained { public: MyContained() {} ~MyContained() {} // Given that the only place Contained objects are declared is m_contained // (below), will this work as expected on any C++ compiler? MyContainer * GetPointerToMyContainer() { return reinterpret_cast<MyContainer *>(this); } }; MyContained m_contained; // MUST BE FIRST MEMBER ITEM DECLARED IN MyContainer int m_foo; // other member items may be declared after m_contained float m_bar; };

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• .Net lambda expression-- where did this parameter come from?

  - by larryq

  I'm a lambda newbie, so if I'm missing vital information in my description please tell me. I'll keep the example as simple as possible. I'm going over someone else's code and they have one class inheriting from another. Here's the derived class first, along with the lambda expression I'm having trouble understanding: class SampleViewModel : ViewModelBase { private ICustomerStorage storage = ModelFactory<ICustomerStorage>.Create(); public ICustomer CurrentCustomer { get { return (ICustomer)GetValue(CurrentCustomerProperty); } set { SetValue(CurrentCustomerProperty, value); } } private int quantitySaved; public int QuantitySaved { get { return quantitySaved; } set { if (quantitySaved != value) { quantitySaved = value; NotifyPropertyChanged(p => QuantitySaved); //where does 'p' come from? } } } public static readonly DependencyProperty CurrentCustomerProperty; static SampleViewModel() { CurrentCustomerProperty = DependencyProperty.Register("CurrentCustomer", typeof(ICustomer), typeof(SampleViewModel), new UIPropertyMetadata(ModelFactory<ICustomer>.Create())); } //more method definitions follow.. Note the call to NotifyPropertyChanged(p => QuantitySaved) bit above. I don't understand where the "p" is coming from. Here's the base class: public abstract class ViewModelBase : DependencyObject, INotifyPropertyChanged, IXtremeMvvmViewModel { public event PropertyChangedEventHandler PropertyChanged; protected virtual void NotifyPropertyChanged<T>(Expression<Func<ViewModelBase, T>> property) { MvvmHelper.NotifyPropertyChanged(property, PropertyChanged); } } There's a lot in there that's not germane to the question I'm sure, but I wanted to err on the side of inclusiveness. The problem is, I don't understand where the 'p' parameter is coming from, and how the compiler knows to (evidently?) fill in a type value of ViewModelBase from thin air? For fun I changed the code from 'p' to 'this', since SampleViewModel inherits from ViewModelBase, but I was met with a series of compiler errors, the first one of which statedInvalid expression term '=>' This confused me a bit since I thought that would work. Can anyone explain what's happening here?

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• Printing to different printers using mozilla.

  - by Nick-ACNB

  I am currently creating a web application that will be deployed in an intranet environment. I chose firefox to be the browser that will run it. However, in the application I am building, I need to be able to print to different printers quickly since they use different paper size depending on what client is coming. To avoid many time-wasting mistakes that could occur, for instance someone choosing the wrong printer and wasting paper. Also, the time used to find the right printer for the job and then pressing print is considered too long in the current context. Is there any solution to this problem? I understand the potential security flaw behind this, but please be aware that this is solely an intranet project and that I can reduce the browser's security to the lowest since they don't access internet. I know there could be something doable behind IE (ActiveX or VBScript) but I am using firefox. Also, I guess there could also be something rather tricky that when you press print on the browser, it saves what needs to be printed to a DB and then there is an exe app that runs and fetch that DB every set ammount of time and print to the right printer. Any suggestion would be greatly appreciated. I doubt I am the only one to ever face this issue! :) Thank you very much.

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• How to add namespaces to a flex AIR project in Flash Builder 4?

  - by milkplus

  In my ant build.xml script I have... <namespace uri="http://ns.foo.com/mxml/2011" manifest="src/manifest.xml"/> <namespace uri="library://ns.adobe.com/flex/spark" manifest="flex_src/spark-manifest.xml"/> <namespace uri="http://www.adobe.com/2006/mxml" manifest="flex_src/mx-manifest.xml"/> That works! But... I'm not sure how to add these namespaces to my project properties in Flash Builder 4 so I can debug. When I try, it changes this line in my .actionScriptProperties <compiler additionalCompilerArguments="-namespace http://ns.foo.com/mxml/2011 src/manifest.xml -namespace=library://ns.adobe.com/flex/spark flex_src/spark-manifest.xml -namespace http://www.adobe.com/2006/mxml flex_src/mx-manifest.xml" autoRSLOrdering="true" copyDependentFiles="true" fteInMXComponents="false" generateAccessible="true" htmlExpressInstall="true" htmlGenerate="false" htmlHistoryManagement="false" htmlPlayerVersionCheck="true" includeNetmonSwc="false" outputFolderPath="bin-debug" sourceFolderPath="src" strict="true" targetPlayerVersion="0.0.0" useApolloConfig="true" useDebugRSLSwfs="true" verifyDigests="true" warn="true"> but gives me a "no default arguments are expected" error. What is the reason for this error? The error location is "Unknown" and seems to refer to these compiler arguments.

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• Syntax error beyond end of program

  - by a_m0d

  I am experimenting with writing a toy compiler in ocaml. Currently, I am trying to implement the offside rule for my lexer. However, I am having some trouble with the ocaml syntax (the compiler errors are extremely un-informative). The code below (33 lines of it) causes an error on line 34, beyond the end of the source code. I am unsure what is causing this error. open Printf let s = (Stack.create():int Stack.t); let rec check x = ( if Stack.is_empty s then Stack.push x s else if Stack.top s < x then ( Stack.push x s; printf "INDENT\n"; ) else if Stack.top s > x then ( printf "DEDENT\n"; Stack.pop s; check x; ) else printf "MATCHED\n"; ); let main () = ( check 0; check 4; check 6; check 8; check 5; ); let _ = Printexc.print main () Ocaml output: File "lexer.ml", line 34, characters 0-0: Error: Syntax error Can someone help me work out what the error is caused by and help me on my way to fixing it?

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• Adding an ASP.NET Web User Control to a Control Dynamically

  - by RandomBen

  I have a simple ASP.NET Web User Control. It looks like this: <%@ Control Language="C#" AutoEventWireup="true" CodeBehind="NewsArticle.ascx.cs" Inherits="Website.Controls.NewsArticle" %> <div> <asp:Literal ID="ltlBody" runat="server" /> </div> My code behind looks like this: namespace Website.Controls { public partial class NewsArticle : System.Web.UI.UserControl { public String bodyText { //get { return ltlBody.Text; } set { ltlBody.Text = value; } } } } On a .aspx page I have <asp:Panel ID="pNews" runat="server" /> In the code behind I have: foreach (vwNews news in newsQuery) { NewsArticle article = new NewsArticle(); aticle.bodyText = news.Body; pNews.Controls.Add(article); } Every time I run this code the newsQuery is populated correctly and I get to the line aticle.bodyText = news.Body; and then I received the error article.bodyText threw an exception of type 'System.NullReferenceException' I am not sure what is causing this error message or how to fix it. I would think that there should not be an issue. I tried creating a constructor for my Web User Control so that it would give default values to my properties but that didn't work. Any idea how to make this work? It doesn't seem like it should be that

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• Are function-local typedefs visible inside C++0x lambdas?

  - by GMan - Save the Unicorns

  I've run into a strange problem. The following simplified code reproduces the problem in MSVC 2010 Beta 2: template <typename T> struct dummy { static T foo(void) { return T(); } }; int main(void) { typedef dummy<bool> dummy_type; auto x = [](void){ bool b = dummy_type::foo(); }; // auto x = [](void){ bool b = dummy<bool>::foo(); }; // works } The typedef I created locally in the function doesn't seem to be visible in the lambda. If I replace the typedef with the actual type, it works as expected. Here are some other test cases: // crashes the compiler, credit to Tarydon int main(void) { struct dummy {}; auto x = [](void){ dummy d; }; } // works as expected int main(void) { typedef int integer; auto x = [](void){ integer i = 0; }; } I don't have g++ 4.5 available to test it, right now. Is this some strange rule in C++0x, or just a bug in the compiler? From the results above, I'm leaning towards bug. Though the crash is definitely a bug. For now, I have filed two bug reports. All code snippets above should compile. The error has to do with using the scope resolution on locally defined scopes. (Spotted by dvide.) And the crash bug has to do with... who knows. :) Update According to the bug reports, they have both been fixed for the next release of Visual Studio 2010.

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• Warning: cast increases required alignment

  - by dash-tom-bang

  I'm recently working on this platform for which a legacy codebase issues a large number of "cast increases required alignment to N" warnings, where N is the size of the target of the cast. struct Message { int32_t id; int32_t type; int8_t data[16]; }; int32_t GetMessageInt(const Message& m) { return *reinterpret_cast<int32_t*>(&data[0]); } Hopefully it's obvious that a "real" implementation would be a bit more complex, but the basic point is that I've got data coming from somewhere, I know that it's aligned (because I need the id and type to be aligned), and yet I get the message that the cast is increasing the alignment, in the example case, to 4. Now I know that I can suppress the warning with an argument to the compiler, and I know that I can cast the bit inside the parentheses to void* first, but I don't really want to go through every bit of code that needs this sort of manipulation (there's a lot because we load a lot of data off of disk, and that data comes in as char buffers so that we can easily pointer-advance), but can anyone give me any other thoughts on this problem? I mean, to me it seems like such an important and common option that you wouldn't want to warn, and if there is actually the possibility of doing it wrong then suppressing the warning isn't going to help. Finally, can't the compiler know as I do how the object in question is actually aligned in the structure, so it should be able to not worry about the alignment on that particular object unless it got bumped a byte or two?

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• c++ use of winmain()

  - by Jack

  Hi, I just started learning programming for windows in c++. I had this crazy image, that win32 programming is based on calling windows functions and sending parameters to and from them. Like, when you want to create window, you call some win32 function that handles windows GUI and say "Hi, please, create me new window, 100 x 100 px, with two buttons", and that GUI function says "Hi, no problem, when something happends, like user clicks one button, I will change this variable xy located in this location". So, I thought that it will be very similiar to console programming. But the very first instruction surprised me. I always thought that every program executes main() function first. So, when I launch app, windows stores some parameters on top of stack and run that application. So I assumed that initializing main() is just a c++ way to tell the compiler where the first instruction should be. But in win32 programming, there is function called winmain() which starts first. So I am little confused. I thought it´s rule that compiler must have main() to start with, that main just defines where ti start, like some start point identifier. So, please, why is there winmain() function instead of main()? When I thought that C++ programming is as logical as assembler, it confuses me once again.

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• c++ use of winmain()

  - by Jack

  Hi, I just started learning programming for windows in c++. I had this crazy image, that win32 programming is based on calling windows functions and sending parameters to and from them. Like, when you want to create window, you call some win32 function that handles windows GUI and say "Hi, please, create me new window, 100 x 100 px, with two buttons", and that GUI function says "Hi, no problem, when something happends, like user clicks one button, I will change this variable xy located in this location". So, I thought that it will be very similiar to console programming. But the very first instruction surprised me. I always thought that every program executes main() function first. So, when I launch app, windows stores some parameters on top of stack and run that application. So I assumed that initializing main() is just a c++ way to tell the compiler where the first instruction should be. But in win32 programming, there is function called winmain() which starts first. So I am little confused. I thought it´s rule that compiler must have main() to start with, that main just defines where ti start, like some start point identifier. So, please, why is there winmain() function instead of main()? When I thought that C++ programming is as logical as assembler, it confuses me once again.

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• std::conditional compile-time branch evaluation

  - by cmannett85

  Compiling this: template < class T, class Y, class ...Args > struct isSame { static constexpr bool value = std::conditional< sizeof...( Args ), typename std::conditional< std::is_same< T, Y >::value, isSame< Y, Args... >, // Error! std::false_type >::type, std::is_same< T, Y > >::type::value; }; int main() { qDebug() << isSame< double, int >::value; return EXIT_SUCCESS; } Gives me this compiler error: error: wrong number of template arguments (1, should be 2 or more) The issue is that isSame< double, int > has an empty Args parameter pack, so isSame< Y, Args... > effectively becomes isSame< Y > which does not match the signature. But my question is: Why is that branch being evaluated at all? sizeof...( Args ) is false, so the inner std:conditional should not be evaluated. This isn't a runtime piece of code, the compiler knows that sizeof..( Args ) will never be true with the given template types. If you're curious, it's supposed to be a variadic version of std::is_same, not that it works...

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• Classes with the same name - is it restricted only within the same translation unit?

  - by LeopardSkinPillBoxHat

  Let's just I had the following code: foo.h class Foo { // ... }; foo.cpp #include "foo.h" // Functions for class Foo defined here... Let's say that Foo are built into a static library foo.lib. Now let's say I have the following: foo2.h class Foo { // ... }; foo2.cpp #include "foo2.h" // Functions for class Foo defined here... This is built into a separate static library foo2.lib. Now, if I re-link foo.lib and foo2.lib into an executable program foo.exe, should it be complaining that class Foo has been defined twice? In my experiences, neither the compiler or the linker are complaining. I wouldn't be expecting the compiler to complain, because they have been defined in separate translation units. But why doesn't the linker complain? How does the linker differentiate between the 2 versions of the Foo class? Does it work by decorating the symbols?

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• calling java script function then C# function after clicking ASP.NET button

  - by Eyla

  I have this serious: I have ASP.NET page, This page contents Update panel with ASP.NET control. I have Java script function to do validation so when I click the button I will use onclientclick to call the java function to do the validation and after this one done should call then event click button function from code behind. I tried vew methods but they did not work for me. here is sample of my code that after I click the button onclientclick will call the java script function for validation and if the validation is OK should call onclick event. .................... java script function ........................ <script type="text/javascript" > function add(){ if (tag == trye) { document.getElementById('<%=btnInfor.ClientID%>').click(); alert("DataAdded") } else { alert("Requiered Field Missing.") return false; } } </script> ..................... ASP.NET button ................... <asp:Button ID="btnInfor" runat="server" Text="Add Information" Style="position: absolute; top: 1659px; left: 433px;" onclientclick="JavaScript: return myAdd()" /> .................... code behind in C# ...................... protected void btnInfor_Click(object sender, EventArgs e) { \\mycode }

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• Java abstract visitor - guarantueed to succeed? If so, why?

  - by disown

  I was dealing with hibernate, trying to figure out the run-time class behind proxied instances by using the visitor pattern. I then came up with an AbstractVisitable approach, but I wonder if it will always produce correct results. Consider the following code: interface Visitable { public void accept(Visitor v); } interface Visitor { public void visit(Visitable visitorHost); } abstract class AbstractVisitable implements Visitable { @Override public void accept(Visitor v) { v.visit(this); } } class ConcreteVisitable extends AbstractVisitable { public static void main(String[] args) { final Visitable visitable = new ConcreteVisitable(); final Visitable proxyVisitable = (Visitable) Proxy.newProxyInstance( Thread.currentThread().getContextClassLoader(), new Class<?>[] { Visitable.class }, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { return method.invoke(visitable, args); } }); proxyVisitable.accept(new Visitor() { @Override public void visit(Visitable visitorHost) { System.out.println(visitorHost.getClass()); } }); } } This makes a ConcreteVisitable which inherits the accept method from AbstractVisitable. In c++, I would consider this risky, since this in AbstractVisitable could be referencing to AbstractVisitable::this, and not ConcreteVisitable::this. I was worried that the code under certain circumstances would print class AbstractVisible. Yet the code above outputs class ConcreteVisitable, even though I hid the real type behind a dynamic proxy (the most difficult case I could come up with). Is the abstract visitor approach above guaranteed to work, or are there some pitfalls with this approach? What guarantees are given in Java with respect to the this pointer?

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• Life Scope of Temporary Variable

  - by Yan Cheng CHEOK

  #include <cstdio> #include <string> void fun(const char* c) { printf("--> %s\n", c); } std::string get() { std::string str = "Hello World"; return str; } int main() { const char *cc = get().c_str(); // cc is not valid at this point. As it is pointing to // temporary string internal buffer, and the temporary string // has already been destroyed at this point. fun(cc); // But I am surprise this call will yield valid result. // It seems that the returned temporary string is valid within // scope (...) // What my understanding is, scope means {...} // Is this valid behavior guarantee by C++ standard? Or it depends // on your compiler vendor implementations? fun(get().c_str()); getchar(); } The output is : --> --> Hello World Hello, may I know the correct behavior is guarantee by C++ standard, or it depends on your compiler vendor implementations? I have tested this under VC2008 and VC6. Works fine for both.

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• Do variable references (alias) incure runtime costs in c++?

  - by cheshirekow

  Maybe this is a compiler specific thing. If so, how about for gcc (g++)? If you use a variable reference/alias like this: int x = 5; int& y = x; y += 10; Does it actually require more cycles than if we didn't use the reference. int x = 5; x += 10; In other words, does the machine code change, or does the "alias" happen only at the compiler level? This may seem like a dumb question, but I am curious. Especially in the case where maybe it would be convenient to temporarily rename some member variables just so that the math code is a little easier to read. Sure, we're not exactly talking about a bottleneck here... but it's something that I'm doing and so I'm just wondering if there is any 'actual' difference... or if it's only cosmetic.

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• How to insert zeros between bits in a bitmap?

  - by anatolyg

  I have some performance-heavy code that performs bit manipulations. It can be reduced to the following well-defined problem: Given a 13-bit bitmap, construct a 26-bit bitmap that contains the original bits spaced at even positions. To illustrate: 0000000000000000000abcdefghijklm (input, 32 bits) 0000000a0b0c0d0e0f0g0h0i0j0k0l0m (output, 32 bits) I currently have it implemented in the following way in C: if (input & (1 << 12)) output |= 1 << 24; if (input & (1 << 11)) output |= 1 << 22; if (input & (1 << 10)) output |= 1 << 20; ... My compiler (MS Visual Studio) turned this into the following: test eax,1000h jne 0064F5EC or edx,1000000h ... (repeated 13 times with minor differences in constants) I wonder whether i can make it any faster. I would like to have my code written in C, but switching to assembly language is possible. Can i use some MMX/SSE instructions to process all bits at once? Maybe i can use multiplication? (multiply by 0x11111111 or some other magical constant) Would it be better to use condition-set instruction (SETcc) instead of conditional-jump instruction? If yes, how can i make the compiler produce such code for me? Any other idea how to make it faster? Any idea how to do the inverse bitmap transformation (i have to implement it too, bit it's less critical)?

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• Gridview looses ItemTemplate after columns are removed

  - by Middletone

  I'm trying to bind a datatable to a gridview where I've removed some of the autogenerated columns in the code behind. I've got two template columns and it seems that when I alter the gridview in code behind and remove the non-templated columns that the templates loose the controls that are in them. Using the following as a sample, "Header A" will continue to be visible but "Header B" will dissapear after removing any columsn that are located at index 2 and above. I'm creating columns in my codebehind for the grid as a part of a reporting tool. If I don't remove the columns then there doesn't seem to be an issue. <asp:GridView ID="DataGrid1" runat="server" AutoGenerateColumns="false" AllowPaging="True" PageSize="10" GridLines="Horizontal"> <Columns> <asp:TemplateField HeaderText="Header A" > <ItemTemplate > Text A </ItemTemplate> </asp:TemplateField> <asp:TemplateField> <HeaderTemplate> Header B </HeaderTemplate> <ItemTemplate> Text B </ItemTemplate> </asp:TemplateField> </Columns> </asp:GridView> For i = 2 To DataGrid1.Columns.Count - 1 DataGrid1.Columns.RemoveAt(2) Next EDIT So from what I've read this seems to be a problem that occurs when the grid is altered. Does anyone know of a good workaround to re-initialize the template columns or set them up again so that when the non-template columns are removed that hte templates don't get removed as well?

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• Having trouble hiding keyboard using invisible button which sits on top of uiscrollview

  - by phil

  I have 3 items in play... 1) UIView sits at the base of the hierarchy and contains the UIScrollview. 2) UIScrollview that is presenting a lengthy user form. 3) An invisible button on the UIScrollview that I'm using to provide "hide the keyboard" features. Notice in the code below that I'm registering to be notified when the keyboard is going to appear and again when it's going to disappear. These are working great. My problem is seemingly one of "layers". See below where I insert the button into the view atIndex:0. This causes the button to be activated and "stuffed" behind the scrollview so that when you click on it, the scrollview grabs the touch and the button is unaware. There is no way to "reach" the button and suppress the keyboard. However, if I insert atIndex:1, the button gets super imposed on top of the text entry fields and so any touch at all is acted upon by the button, which immediately suppresses the keyboard and then disappears. How do I insert the button on top of the UIScrollview but behind the UITextfields that sit there? other logistics: I have a -(void) hidekeyboard function that I have setup with the UIButtion as an IBAction(). And I have the UIButton connected to "files owner" via a ctrl-drag/drop. (Do I need both of those conventions?) This code in ViewDidLoad()... [[NSNotificationCenter defaultCenter] addObserverForName:UIKeyboardWillShowNotification object:nil queue:nil usingBlock:^(NSNotification *notification){ [self.view insertSubview:self.keyboardDismissalButton atIndex:0]; }];

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• Where in the standard is forwarding to a base class required in these situations?

  - by pgast

  Maybe even better is: Why does the standard require forwarding to a base class in these situations? (yeah yeah yeah - Why? - Because.) class B1 { public: virtual void f()=0; }; class B2 { public: virtual void f(){} }; class D : public B1,public B2{ }; class D2 : public B1,public B2{ public: using B2::f; }; class D3 : public B1,public B2{ public: void f(){ B2::f(); } }; D d; D2 d2; D3 d3; EDG gives: sourceFile.cpp sourceFile.cpp(24) : error C2259: 'D' : cannot instantiate abstract class due to following members: 'void B1::f(void)' : is abstract sourceFile.cpp(6) : see declaration of 'B1::f' sourceFile.cpp(25) : error C2259: 'D2' : cannot instantiate abstract class due to following members: 'void B1::f(void)' : is abstract sourceFile.cpp(6) : see declaration of 'B and similarly for the MS compiler. I might buy the first case,D. But in D2 - f is unambiguously defined by the using declaration, why is that not enough for the compiler to be required to fill out the vtable? Where in the standard is this situation defined?

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• Common "truisms" needing correction the most

  - by Charles Bretana

  In addition to "I never met a man I didn't like", Will Rogers had another great little ditty I've always remembered. It went: "It's not what you don't know that'll hurt you, it's what you do know that ain't so." We all know or subscribe to many IT "truisms" that mostly have a strong basis in fact, in something in our professional careers, something we learned from others, lessons learned the hard way by ourselves, or by others who came before us. Unfortuntely, as these truisms spread throughout the community, the details—why they came about and the caveats that affect when they apply—tend to not spread along with them. We all have a tendency to look for, and latch on to, small "rules" or principles that we can use to avoid doing a complete exhaustive analysis for every decision. But even though they are correct much of the time, when we sometimes misapply them, we pay a penalty that could be avoided by understooding the details behind them. For example, when user-defined functions were first introduced in SQL Server it became "common knowledge" within a year or so that they had extremely bad performance (because it required a re-compilation for each use) and should be avoided. This "trusim" still increases many database developers' aversion to using UDFs, even though Microsoft's introduction of InLine UDFs, which do not suffer from this issue at all, mitigates this issue substantially. In recent years I have run into numerous DBAs who still believe you should "never" use UDFs, because of this. What other common not-so-"trusims" do you know, which many developers believe, that are not quite as universally true as is commonly understood, and which the developer community would benefit from being better educated about? Please include why it was "true" to start off with, and under what circumstances it's not true. Limit responses to issues that are technical, where the "common" application of a "rule or principle" is in fact correct most of the time, or was correct back when it was first elucidated, but—in the edge cases, or because of not understanding the principle thoroughly, because technology has changed since it first spread, or applying the rule today without understanding the details behind the rule—can easily backfire or cause the opposite of the intended effect.

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• How to modify Keyboard interrupt (under Windows XP) from a C++ Program ?

  - by rockr90

  Hi everyone ! We have been given a little project (As part of my OS course) to make a Windows program that modifies keyboard input, so that it transforms any lowercase character entered into an uppercase one (without using caps-lock) ! so when you type on the keyboard you'll see what you're typing transformed into uppercase ! I have done this quite easily using Turbo C by calling geninterrupt() and using variables _AH, _AL, i had to read a character using: _AH = 0x07; // Reading a character without echo geninterrupt(0x21); // Dos interrupt Then to transform it into an Upercase letter i have to mask the 5th bit by using: _AL = _AL & 0xDF; // Masking the entered character with 11011111 and then i will display the character using any output routine. Now, this solution will only work under old C DOS compilers. But what we intend to do is to make a close or similar solution to this by using any modern C/C++ compiler under Windows XP ! What i have first thought of is modifying the Keyboard ISR so that it masks the fifth bit of any entered character to turn it uppercase ! But i do not know how exactly to do this. Second, I wanted to create a Win32 console program to either do the same solution (but to no avail) or make a windows-compatible solution, still i do not know which functions to use ! Third I thought to make a windows program that modifies the ISR directly to suit my needs ! and i'm still looking for how to do this ! So please, If you could help me out on this, I would greatly appreciate it ! Thank you in advance ! (I'm using Windows XP on intel X86 with mingw-GCC compiler.)

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• virtual methods and template classes

  - by soxs060389

  Hi I got over a problem, I think a very specific one. I've got 2 classes, a B aseclass and a D erived class (from B aseclass). B is a template class ( or class template) and has a pure virtual method virutal void work(const T &dummy) = 0; The D erived class is supposed to reimplement this, but as D is Derived from B rather than D being another template class, the compiler spits at me that virtual functions and templates don't work at once. Any ideas how to acomplish what I want? I am thankfull for any thoughts and Ideas, especially if you allready worked out that problem this class is fixed aka AS IS, I can not edit this without breaking existing code base template <typename T> class B { public: ... virtual void work(const T &dummy) = 0; .. }; take int* as an example class D : public B<int*>{ ... virtual void work(const int* &dummy){ /* put work code here */ } .. }; Edit: The compiler tells me, that void B<T>::work(const T&) [with T = int*] is pure virtual within D

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