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• Why is the 'this' keyword not a reference type in C++ [closed]

  - by Dave Tapley

  Possible Duplicates: Why ‘this’ is a pointer and not a reference? SAFE Pointer to a pointer (well reference to a reference) in C# The this keyword in C++ gets a pointer to the object I currently am. My question is why is the type of this a pointer type and not a reference type. Are there any conditions under which the this keyword would be NULL? My immediate thought would be in a static function, but Visual C++ at least is smart enough to spot this and report static member functions do not have 'this' pointers. Is this in the standard?

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• How do C++ compilers actually pass reference parameters?

  - by T.E.D.

  This question came about as a result of some mixed-langauge programming. I had a Fortran routine I wanted to call from C++ code. Fortran passes all its parameters by reference (unless you tell it otherwise). So I thought I'd be clever (bad start right there) in my C++ code and define the Fortran routine something like this: extern "C" void FORTRAN_ROUTINE (unsigned & flag); This code worked for a while but (of course right when I needed to leave) suddenly started blowing up on a return call. Clear indication of a munged call stack. Another engineer came behind me and fixed the problem, declaring that the routine had to be deinfed in C++ as extern "C" void FORTRAN_ROUTINE (unsigned * flag); I'd accept that except for two things. One is that it seems rather counter-intuitive for the compiler to not pass reference parameters by reference, and I can find no documentation anywhere that says that. The other is that he changed a whole raft of other code in there at the same time, so it theoretically could have been another change that fixed whatever the issue was. So the question is, how does C++ actually pass reference parameters? Is it perhaps free to do copy-in, copy-out for small values or something? In other words, are reference parameters utterly useless in mixed-language programming? I'd like to know so I don't make this same code-killing mistake ever again.

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• Reference manager for Ubuntu

  - by user36511

  I'm in dire need of a reference/citation manager in Ubuntu. The features I need the most are: 1) Metadata extraction/editing of pdf 2) Fetch metadata from online databases such as Google Scholar 3) Attach pdf or other file to reference 4) Tag references and recall those with a given tag or set of tags 5) Provide APA style citation for references (in integration with OOffice and/or Latex) Optional: Would be great if it can annotate/highlight pdfs. Mendeley probably does all of these, but it's behavior has driven me insane, especially when the number of references it's trying to handle is large. It constantly tries to sync with the web and creates duplicate references. I've tried JabRef, and while it looks like a decent piece of freeware, it doesn't do some of the above. I found others like Bibus, Referencer, etc. to be lacking or buggy or inactive development. Is there another option, or should I give up the search.

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• When is it okay to reference WindowsBase.dll?

  - by Tyler

  I've heard/read about people not wanting to reference the assembly because of the Windows component (e.g. "I don't want to reference Windows for my Web App). I'd like to hear what a large community feels about this. For which project types (business, data access, etc.) is it considered acceptable to reference WindowsBase.dll.

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• In java are the parameters passed by reference or by value

  - by subran

  In java are the parameters passed by reference or by value

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• How to add a web service reference in a DLL

  - by dan

  I'm creating a DLL with a reference to web services (I don't have the choice to do so) but I have to add web service references to the project that uses the DLL for it to work. Example, I have the DLL called API.DLL that calls a web service called WebService.svc that I want to use in a project called WinForm. First, I have to add a "Service Reference" to WebService.svc in API.DLL. Then, I add a reference API.DLL to WinForm but it doesn't work unless I also add a service reference to WebService.svc in WinForm. What can I do to avoid that last step?

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• object reference set in java

  - by landon9720

  I need to create a Set of objects. The concern is I do not want to base the hashing or the equality on the objects' hashCode and equals implementation. Instead, I want the hash code and equality to be based only on each object's reference identity (i.e.: the value of the reference pointer). I'm not sure how to do this in Java. The reasoning behind this is my objects do not reliably implement equals or hashCode, and in this case reference identity is good enough.

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• error CS0133: Assigning the result of a function to a const in C#.net

  - by Greg

  Trying to tidy up scope and avoid possible multiple calls to RegisterWindowMessage. Currently have a class used once with the following member [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)] static extern int RegisterWindowMessage(string lpString); private int m_message = RegisterWindowMessage("MY_MSG"); As we only have one instance this seems ok, but think it would be more tidy to use. With my basic C# understanding this should call RegisterWindowMessage and assign the result to int and not allow it to change. private const int message = RegisterWindowMessage("MY_MSG"); however attempting to do so leads to a error CS0133: The expression being assigned to 'someclass.messageEvent' must be constant so now I'm confused, does this mean the function was being assigned and called each time m_message was used previously, is there something else missing?

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• Avoiding improper std::string initialization with NULL const char* using g++

  - by pachanga

  A there any g++ options which can detect improper initialization of std::string with NULL const char*? I was in the process of turning some int fields into std::string ones, i.e: struct Foo { int id; Foo() : id(0) {} }; ...turned into: struct Foo { std::string id; Foo() : id(0) {} //oooops! }; I completely overlooked bad 'id' initialization with 0 and g++ gave me no warnings at all. This error was detected in the run time(std::string constructor threw an exception) but I'd really like to detect such stuff in the compile time. Is there any way?

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• C++ Ambiguous call to Overloaded Function (const variety)

  - by Joe

  After researching this online, I've only found solutions that don't apply to my problem, so please bear with me. Code snippet: typedef my_map_t<int const *, float> _test; my_map_t::const_iterator not_found = my_map_t::end(); if (_test.find(&iKeyValue) == not_found) { _test[iKeyValue] = 4 + 5; // not the actual code, but here for simplicity } The compiler complains that there's an ambiguous call to my_map_t::end(). This makes sense, because the only difference is the return type. Output: error C2668: 'std::_Tree<_Traits>::end' : ambiguous call to overloaded function Normally you can disambiguate the call by casting the parameters, but end() has no parameters. Any ideas?

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• Unreachable code detected by using const variables

  - by Anton Roth

  I have following code: private const FlyCapture2Managed.PixelFormat f7PF = FlyCapture2Managed.PixelFormat.PixelFormatMono16; public PGRCamera(ExamForm input, bool red, int flags, int drawWidth, int drawHeight) { if (f7PF == FlyCapture2Managed.PixelFormat.PixelFormatMono8) { bpp = 8; // unreachable warning } else if (f7PF == FlyCapture2Managed.PixelFormat.PixelFormatMono16){ bpp = 16; } else { MessageBox.Show("Camera misconfigured"); // unreachable warning } } I understand that this code is unreachable, but I don't want that message to appear, since it's a configuration on compilation which just needs a change in the constant to test different settings, and the bits per pixel (bpp) change depending on the pixel format. Is there a good way to have just one variable being constant, deriving the other from it, but not resulting in an unreachable code warning? Note that I need both values, on start of the camera it needs to be configured to the proper Pixel Format, and my image understanding code needs to know how many bits the image is in. So, is there a good workaround, or do I just live with this warning?

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• error: 'QTabWidget::QTabWidget(const QTabWidget&)' is private

  - by Mahdi_Nine

  I develop a program and I have 10 backups of it. I added some lines to it and when I compiled the project and now it has the following error: C:\Qt\Qt5.0.1\5.0.1\mingw47_32\include\QtWidgets\qtabwidget.h:173: error: 'QTabWidget::QTabWidget(const QTabWidget&)' is private the error is from * line namespace Ui { class ContentControl; } class ContentControl : public QTabWidget // * from this line { Q_OBJECT public: . . . } All backups have this error now. Any idea why? I re-installed Qt but the problem is still present.

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• converting an array of characters to a const gchar*

  - by Mark Roberts

  I've got an array of characters which contains a string: char buf[MAXBUFLEN]; buf[0] = 'f'; buf[1] = 'o'; buf[2] = 'o'; buf[3] = '\0'; I'm looking to pass this string as an argument to the gtk_text_buffer_insert function in order to insert it into a GtkTextBuffer. What I can't figure out is how to convert it to a const gchar *, which is what gtk_text_buffer_insert expects as its third argument. Can anybody help me out?

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• How to pass a const unsigned char * from c++ to c#

  - by tzup

  So I have a function in unmanaged c++ that gets called when some text happens to have "arrived": #using <MyParser.dll> ... void dump_body(const unsigned char *Body, int BodyLen) { // Need to pass the body to DumpBody, but as what type? ... lMyParser::Parser::DumpBody(???); } DumpBody is a function defined in a C# DLL that should take one parameter of type? Body holds an array of characters (text) of length BodyLen. There's obviously some marshalling to be done here but I have no idea how. Please help.

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• Windows C++: LPCTSTR vs const TCHAR

  - by mrl33t

  In my application i'm declaring a string variable near the top of my code to define the name of my window class which I use in my calls to RegisterClassEx, CreateWindowEx etc.. Now, I know that an LPCTSTR is a typedef and will eventually follow down to a TCHAR (well a CHAR or WCHAR depending on whether UNICODE is defined), but I was wondering whether it would be better to use this: static LPCTSTR szWindowClass = TEXT("MyApp"); Or this: static const TCHAR szWindowClass[] = TEXT("MyApp"); I personally prefer the use of the LPCTSTR as coming from a JavaScript, PHP, C# background I never really considered declaring a string as an array of chars. But are there actually any advantages of using one over the other, or does it in fact not even make a difference as to which one I choose? Thank you, in advanced, for your answers.

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• std::cin >> *aa results in a bus error

  - by Koning Baard XIV

  I have this a class called PPString: PPString.h #ifndef __CPP_PPString #define __CPP_PPString #include "PPObject.h" class PPString : public PPObject { char *stringValue[]; public: char *pointerToCharString(); void setCharString(char *charString[]); void setCharString(const char charString[]); }; #endif PPString.cpp #include "PPString.h" char *PPString::pointerToCharString() { return *stringValue; } void PPString::setCharString(char *charString[]) { *stringValue = *charString; } void PPString::setCharString(const char charString[]) { *stringValue = (char *)charString; } I'm trying to set the stringValue using std::cin: main.cpp PPString myString; myString.setCharString("LOLZ"); std::cout << myString.pointerToCharString() << std::endl; char *aa[1000]; std::cin >> *aa; myString.setCharString(aa); std::cout << myString.pointerToCharString() << std::endl; The first one, which uses a const char works, but the second one, with a char doesn't, and I get this output: copy and paste from STDOUT LOLZ im entering a string now... Bus error where the second line is what I entered, followed by pressing the return key. Can anyone help me fixing this? Thanks...

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• I can't get that `bus error` to stop sucking.

  - by Koning Baard XIV

  I have this a class called PPString: PPString.h #ifndef __CPP_PPString #define __CPP_PPString #include "PPObject.h" class PPString : public PPObject { char *stringValue[]; public: char *pointerToCharString(); void setCharString(char *charString[]); void setCharString(const char charString[]); }; #endif PPString.cpp #include "PPString.h" char *PPString::pointerToCharString() { return *stringValue; } void PPString::setCharString(char *charString[]) { *stringValue = *charString; } void PPString::setCharString(const char charString[]) { *stringValue = (char *)charString; } I'm trying to set the stringValue using std::cin: main.cpp PPString myString; myString.setCharString("LOLZ"); std::cout << myString.pointerToCharString() << std::endl; char *aa[1000]; std::cin >> *aa; myString.setCharString(aa); std::cout << myString.pointerToCharString() << std::endl; The first one, which uses a const char works, but the second one, with a char doesn't, and I get this output: copy and paste from STDOUT LOLZ im entering a string now... Bus error where the second line is what I entered, followed by pressing the return key. Can anyone help me fixing this? Thanks...

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• AIA und die "IT Strategies from Oracle"

  - by Hans Viehmann

  Die Oracle Application Integration Architecture lässt sich gut nutzen, um eine SOA Initiative zügig zu starten. Naturgemäß berücksichtigt sie aber nicht alle Aspekte einer IT Strategie. Zu diesem Thema gibt es nun seit einigen Wochen eine umfassende Bibliothek von Handbüchern ("Practitioner's Guides") und Referenz-Architekturen, in denen die Erfahrung aus zahlreichen Projekten zusammengefasst ist.Hier ist beispielsweise ein IT Governance Framework beschrieben, das auch die wesentlichen Aspekte der SOA GovernanceSOA Portfolio GovernanceService Lifecycle GovernanceSOA Solution Lifecycle GovernanceSOA Vitality GovernanceSOA Organization Governancenäher beschreibt.In den Handbüchern sind zahlreiche wertvolle Hinweise und best practices enthalten; ich denke, es lohnt sich, einen Blick hinein zu werfen.Die gesamte Bibliothek findet sich unter http://www.oracle.com/goto/itstrategies; eine Übersicht über die verschiedenen Aspekte ist in dem Bild unten zusammengefasst.View image

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• Problem with MVC3 application

  - by Pravin Patil

  I am working on MVC3 application. I use entity framework, NInject, Fluent Validation and some more Nuget packages. I am using Tortoise SVN for versioning. Recently I changed the structure of my SVN repository, so my working copy of MVC3 app was moved to some different folder in the repository. Now when I checked out the copy from SVN, all the references that I had added through Nuget were lost(EF, NInject and rest nuget packages were showing yellow missing icon in references). This had happened to me prior to this also, when I tried to check out the app from svn to some other folder. I had to manually add all the references again through Nuget again. Am I doing anything wrong? Please guide. I hope I could explain my problem properly.

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• As a programmer, what would you use a personal Wiki for?

  - by Adam Harte

  Do any programmers out there keep a personal wiki? Either locally or online. What do you use your wiki for? or what might you use one for? I was thinking of starting a personal wiki as a place to record documentation and and other documents for my personal projects, and various notes etc, but how else is a personal (maybe private) Wiki useful to a programmer/developer? What type of things would you put in a personal Wiki?

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• Scrum got specific ways for testing software?

  - by joker13

  When reading Scrum Guide, as the official text for scrum, I find out there is no specific solution to provide software testing in scrum. (the only hint is on page15) I'm a little vague on whether scrum is considered a software development methodology or not? If it is not, then how come some of its practices opposes Extreme Programming? (I know that in scrum guide, the author notes that scrum is a framework not a methodology, but still I'm not pretty clear on that) And what's more, I'm not sure if there are any other important textbook that I'm missing so far about scrum. I need them to be official or of great deal of public acceptance.

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• How common are circular references? Would reference-counting GC work just fine?

  - by user9521

  How common are circular references? The less common they are, the fewer hard cases you have if you are writing in a language with only reference counting-GC. Are there any cases where it wouldn't work well to make one of the references a "weak" reference so that reference counting still works? It seems like you should be able to have a language only use reference counting and weak references and have things work just fine most of the time, with the goal of efficiency. You could also have tools to help you detect memory leaks caused by circular references. Thoughts, anyone? It seems that Python uses references counting (I don't know if it uses a tracing collector occasionally or not for sure) and I know that Vala uses reference counting with weak references; I know that it's been done before, but how well would it work?

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• Do objects maintain identity under all non-cloning conditions in PHP?

  - by Buttle Butkus

  PHP 5.5 I'm doing a bunch of passing around of objects with the assumption that they will all maintain their identities - that any changes made to their states from inside other objects' methods will continue to hold true afterwards. Am I assuming correctly? I will give my basic structure here. class builder { protected $foo_ids = array(); // set in construct protected $foo_collection; protected $bar_ids = array(); // set in construct protected $bar_collection; protected function initFoos() { $this->foo_collection = new FooCollection(); foreach($this->food_ids as $id) { $this->foo_collection->addFoo(new foo($id)); } } protected function initBars() { // same idea as initFoos } protected function wireFoosAndBars(fooCollection $foos, barCollection $bars) { // arguments are passed in using $this->foo_collection and $this->bar_collection foreach($foos as $foo_obj) { // (foo_collection implements IteratorAggregate) $bar_ids = $foo_obj->getAssociatedBarIds(); if(!empty($bar_ids) ) { $bar_collection = new barCollection(); // sub-collection to be a component of each foo foreach($bar_ids as $bar_id) { $bar_collection->addBar(new bar($bar_id)); } $foo_obj->addBarCollection($bar_collection); // now each foo_obj has a collection of bar objects, each of which is also in the main collection. Are they the same objects? } } } } What has me worried is that foreach supposedly works on a copy of its arrays. I want all the $foo and $bar objects to maintain their identities no matter which $collection object they become of a part of. Does that make sense?

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• What happens if we serialize and deserialize two objects which references to each other?

  - by Seregwethrin

  To make it more clear, this is a quick example: class A implements Serializable { public B b; } class B implements Serializable { public A a; } A a = new A(); B b = new B(); a.b = b; b.a = a; So what happens if we serialize a and b objects into a file and deserialize from that file? I thought we get 4 objects, 2 of each. Identical objects but different instances. But I'm not sure if there's anything else or is it right or wrong. If any technology needed to answer, please think based on Java. Thank you.

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• Partial specialization with reference template parameter fails to compile in VS2005

  - by Blair Holloway

  I have code that boils down to the following: template struct Foo {}; template & I struct FooBar {}; //////// template struct Baz {}; template & I struct Baz< FooBar { static void func(FooBar& value); }; //////// struct MyStruct { static const Foo s_floatFoo; }; // Elsewhere: const Foo MyStruct::s_floatFoo; void callBaz() { typedef FooBar FloatFooBar; FloatFooBar myFloatFooBar; Baz::func(myFloatFooBar); } This compiles successfully under GCC, however, under VS2005, I get: error C2039: 'func' : is not a member of 'Baz' with [ T=FloatFooBar ] error C3861: 'func': identifier not found However, if I change const Foo<T>& I to const Foo<T>* I (passing I by pointer rather than by reference), and defining FloatFooBar as: typedef FooBar FloatFooBar; Both GCC and VS2005 are happy. What's going on? Is this some kind of subtle template substitution failure that VS2005 is handling differently to GCC, or a compiler bug? (The strangest thing: I thought I had the above code working in VS2005 earlier this morning. But that was before my morning coffee. I'm now not entirely certain I wasn't under some sort of caffeine-craving-induced delirium...)

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