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  • Exception throws: encapsulate them or not?

    - by Simon
    Hi there. Once I read an MSDN article that encouraged the following programming paradigm: public class MyClass { public void Method1() { NewCustomException(); } public void Method2() { NewCustomException(); } void NewCustomException() { throw new CustomException("Exception message"); } } Do you think this paradigm makes sense? Wouldn't it be enough to store the exception message in a static const field and then pass it to the exception's constructor, instead of encapsulating the whole exception throw?

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  • Java reflection framework and security

    - by Jijoy
    Hi , Assume I have a singleton class in an external lib to my application. But still I can create instances of that particular class using reflection. Like this Class clas = Class.forName(Private.class.getName()); for(Constructor c : clas.getDeclaredConstructors()){ c.setAccessible(true); Private p = (Private) c.newInstance(); System.out.println(p); } How can I restrict this ? . Thanks J

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  • WP7 databinding displays int but not string?

    - by user1794106
    Whenever I test my app.. it binds the data from Note class and displays it if it isn't a string. But for the string variables it wont bind. What am I doing wrong? Inside my main: <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0"> <ListBox x:Name="Listbox" SelectionChanged="listbox_SelectionChanged" ItemsSource="{Binding}"> <ListBox.ItemTemplate> <DataTemplate> <Border Width="800" MinHeight="60"> <StackPanel> <TextBlock x:Name="Title" VerticalAlignment="Center" FontSize="{Binding TextSize}" Text="{Binding Name}"/> <TextBlock x:Name="Date" VerticalAlignment="Center" FontSize="{Binding TextSize}" Text="{Binding Modified}"/> </StackPanel> </Border> </DataTemplate> </ListBox.ItemTemplate> </ListBox> </Grid> </Grid> in code behind: protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e) { MessageBox.Show("enters onNav Main"); DataContext = null; DataContext = Settings.NotesList; Settings.CurrentNoteIndex = -1; Listbox.SelectedIndex = -1; if (Settings.NotesList != null) { if (Settings.NotesList.Count == 0) { Notes.Text = "No Notes"; } else { Notes.Text = ""; } } } and public static class Settings { public static ObservableCollection<Note> NotesList; static IsolatedStorageSettings settings; private static int currentNoteIndex; static Settings() { NotesList = new ObservableCollection<Note>(); settings = IsolatedStorageSettings.ApplicationSettings; MessageBox.Show("enters constructor settings"); } notes class: public class Note { public DateTimeOffset Modified { get; set; } public string Title { get; set; } public string Content { get; set; } public int TextSize { get; set; } public Note() { MessageBox.Show("enters Note Constructor"); Modified = DateTimeOffset.Now; Title = "test"; Content = "test"; TextSize = 32; } }

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  • More trivia than really important: Why no new() constraint on Activator.CreateInstance<T>() ?

    - by flq
    I think there are people who may be able to answer this, this is a question out of curiosity: The generic CreateInstance method from System.Activator, introduced in .NET v2 has no type constraints on the generic argument but does require a default constructor on the activated type, otherwise a MissingMethodException is thrown. To me it seems obvious that this method should have a type constraint like Activator.CreateInstance<T>() where T : new() { ... } Just an omission or some anecdote lurking here?

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  • Java homework help, Error <identifier> expected

    - by user2900126
    Help with java homework this is my assignment that I have, this assignment code I've tried. But when I try to compile it I keep getting errors which I cant seem to find soloutions too: Error says <identifier> expected for Line 67 public static void () Assignment brief To write a simple java classMobile that models a mobile phone. Details the information stored about each mobile phone will include • Its type e.g. “Sony ericsson x90” or “Samsung Galaxy S”; • Its screen size in inches; You may assume that this a whole number from the scale 3 to 5 inclusive. • Its memory card capacity in gigabytes You may assume that this a whole number • The name of its present service provider You may assume this is a single line of text. • The type of contract with service provider You may assume this is a single line of text. • Its camera resolution in megapixels; You should not assume that this a whole number; • The percentage of charge left on the phone e.g. a fully charged phone will have a charge of 100. You may assume that this a whole number • Whether the phone has GPS or not. Your class will have fields corresponding to these attributes . Start by opening BlueJ, creating a new project called myMobile which has a classMobile and set up the fields that you need, Next you will need to write a Constructor for the class. Assume that each phone is manufactured by creating an object and specifying its type, its screen size, its memory card capacity, its camera resolution and whether it has GPS or not. Therefore you will need a constructor that allows you to pass arguments to initialise these five attributes. Other fields should be set to appropriate default values. You may assume that a new phone comes fully charged. When the phone is sold to its owner, you will need to set the service provider and type of contract with that provider so you will need mutator methods • setProvider () - - to set service provider. • setContractType - - to set the type of contract These methods will be used when the phones provider is changed. You should also write a mutator method ChargeUp () which simulates fully charging the phone. To obtain information about your mobile object you should write • accessor methods corresponding to four of its fields: • getType () – which returns the type of mobile; • getProvider () – which returns the present service provider; • getContractType () – which returns its type of contract; • getCharge () – which returns its remaining charge. An accessor method to printDetails () to print, to the terminal window, a report about the phone e.g. This mobile phone is a sony Erricsson X90 with Service provider BigAl and type of contract PAYG. At present it has 30% of its battery charge remaining. Check that the new method works correctly by for example, • creating a Mobile object and setting its fields; • calling printDetails () and t=checking the report corresponds to the details you have just given the mobile; • changing the service provider and contract type by calling setprovider () and setContractType (); • calling printDetails () and checking the report now prints out the new details. Challenging excercises • write a mutator methodswitchedOnFor () =which simulates using the phone for a specified period. You may assume the phone loses 1% of its charge for each hour that it is switched on . • write an accessor method checkcharge () whichg checks the phone remaing charge. If this charge has a value less than 25%, then this method returns a string containg the message Be aware that you will soon need to re-charge your phone, otherwise it returns a string your phone charge is sufficient. • Write a method changeProvider () which simulates changing the provider (and presumably also the type of service contract). Finally you may add up to four additional fields, with appropriate methods, that might be required in a more detailed model. above is my assignment that I have, this assignment code I've tried. But when I try to oompile it I keep getting errors which I cant seem to find soloutions too: Error says <identifier> expected for Line 67 public static void () /** * to write a simple java class Mobile that models a mobile phone. * * @author (Lewis Burte-Clarke) * @version (14/10/13) */ public class Mobile { // type of phone private String phonetype; // size of screen in inches private int screensize; // menory card capacity private int memorycardcapacity; // name of present service provider private String serviceprovider; // type of contract with service provider private int typeofcontract; // camera resolution in megapixels private int cameraresolution; // the percentage of charge left on the phone private int checkcharge; // wether the phone has GPS or not private String GPS; // instance variables - replace the example below with your own private int x; // The constructor method public Mobile(String mobilephonetype, int mobilescreensize, int mobilememorycardcapacity,int mobilecameraresolution,String mobileGPS, String newserviceprovider) { this.phonetype = mobilephonetype; this.screensize = mobilescreensize; this.memorycardcapacity = mobilememorycardcapacity; this.cameraresolution = mobilecameraresolution; this.GPS = mobileGPS; // you do not use this ones during instantiation,you can remove them if you do not need or assign them some default values //this.serviceprovider = newserviceprovider; //this.typeofcontract = 12; //this.checkcharge = checkcharge; Mobile samsungPhone = new Mobile("Samsung", "1024", "2", "verizon", "8", "GPS"); 1024 = screensize; 2 = memorycardcapacity; 8 = resolution; GPS = gps; "verizon"=serviceprovider; //typeofcontract = 12; //checkcharge = checkcharge; } // A method to display the state of the object to the screen public void displayMobileDetails() { System.out.println("phonetype: " + phonetype); System.out.println("screensize: " + screensize); System.out.println("memorycardcapacity: " + memorycardcapacity); System.out.println("cameraresolution: " + cameraresolution); System.out.println("GPS: " + GPS); System.out.println("serviceprovider: " + serviceprovider); System.out.println("typeofcontract: " + typeofcontract); } /** * The mymobile class implements an application that * simply displays "new Mobile!" to the standard output. */ public class mymobile { public static void main(String[] args) { System.out.println("new Mobile!"); //Display the string. } } public static void buildPhones(){ Mobile Samsung = new Mobile("Samsung", "3.0", "4gb", "8mega pixels", "GPS"); Mobile Blackberry = new Mobile("Blackberry", "3.0", "4gb", "8mega pixels", "GPS"); Samsung.displayMobileDetails(); Blackberry.displayMobileDetails(); } public static void main(String[] args) { buildPhones(); } } any answers.replies and help would be greatly appreciated as I really lost!

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  • Trigger function on deserialization

    - by Tom Savage
    I have a class with a number of fields which are normally calculated in the constructor from other data in the class. They are not serialized to XML because any changes to the rest of the data will likely require their recalculation. Is there a way I can set up a function call to be triggered on deserialization?

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  • Qt gstreamer problem

    - by ZolaKt
    Ptterb can you post your full code please? I copied your code. Added fvidscale_cap to pipeline, with: self.player.add(self.source, self.scaler, self.fvidscale_cap, self.sink) gst.element_link_many(self.source,self.scaler, self.fvidscale_cap, self.sink) From the main program I create a new QWidget, and pass its winId() to Vid constructor. The widget start loading, but crashes. The output says: should be playing Segmentation fault

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  • How deep are your unit tests?

    - by John Nolan
    The thing I've found about TDD is that its takes time to get your tests set up and being naturally lazy I always want to write as little code as possible. The first thing I seem do is test my constructor has set all the properties but is this overkill? My question is to what level of granularity do you write you unit tests at? ..and is there a case of testing too much?

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  • Extend Javascript Date Object

    - by jAndy
    Hi Folks, I'm curious what would be the best practice to extend the Date constructor. The problem I'm facing is, that the Internet Explorer (< 7+8) can't parse a date like new Date('2010-05-11'); I have to admit that this is not a standard method to parse, anyways FireFox and Chrome perform well on that kind of date string. Now I'm wondering, should I just split/parse/rebuild the string before calling new Date() or is there a more elegant solution ?

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  • XNA and Ninject: Syntax for dependency arguments?

    - by Rosarch
    I have a class with a public constructor: public MasterEngine(IInputReader inputReader) { this.inputReader = inputReader; graphicsDeviceManager = new GraphicsDeviceManager(this); Components.Add(new GamerServicesComponent(this)); } How can I inject dependencies like graphicsDeviceManager and new GamerServicesComponent while still supplying the argument this?

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  • Erroneous/Incorrect C2248 error using Visual Studio 2010

    - by Dylan Bourque
    I'm seeing what I believe to be an erroneous/incorrect compiler error using the Visual Studio 2010 compiler. I'm in the process of up-porting our codebase from Visual Studio 2005 and I ran across a construct that was building correctly before but now generates a C2248 compiler error. Obviously, the code snippet below has been generic-ized, but it is a compilable example of the scenario. The ObjectPtr<T> C++ template comes from our codebase and is the source of the error in question. What appears to be happening is that the compiler is generating a call to the copy constructor for ObjectPtr<T> when it shouldn't (see my comment block in the SomeContainer::Foo() method below). For this code construct, there is a public cast operator for SomeUsefulData * on ObjectPtr<SomeUsefulData> but it is not being chosen inside the true expression if the ?: operator. Instead, I get the two errors in the block quote below. Based on my knowledge of C++, this code should compile. Has anyone else seen this behavior? If not, can someone point me to a clarification of the compiler resolution rules that would explain why it's attempting to generate a copy of the object in this case? Thanks in advance, Dylan Bourque Visual Studio build output: c:\projects\objectptrtest\objectptrtest.cpp(177): error C2248: 'ObjectPtr::ObjectPtr' : cannot access private member declared in class 'ObjectPtr' with [ T=SomeUsefulData ] c:\projects\objectptrtest\objectptrtest.cpp(25) : see declaration of 'ObjectPtr::ObjectPtr' with [ T=SomeUsefulData ] c:\projects\objectptrtest\objectptrtest.cpp(177): error C2248: 'ObjectPtr::ObjectPtr' : cannot access private member declared in class 'ObjectPtr' with [ T=SomeUsefulData ] c:\projects\objectptrtest\objectptrtest.cpp(25) : see declaration of 'ObjectPtr::ObjectPtr' with [ T=SomeUsefulData ] Below is a minimal, compilable example of the scenario: #include <stdio.h> #include <tchar.h> template<class T> class ObjectPtr { public: ObjectPtr<T> (T* pObj = NULL, bool bShared = false) : m_pObject(pObj), m_bObjectShared(bShared) {} ~ObjectPtr<T> () { Detach(); } private: // private, unimplemented copy constructor and assignment operator // to guarantee that ObjectPtr<T> objects are not copied ObjectPtr<T> (const ObjectPtr<T>&); ObjectPtr<T>& operator = (const ObjectPtr<T>&); public: T * GetObject () { return m_pObject; } const T * GetObject () const { return m_pObject; } bool HasObject () const { return (GetObject()!=NULL); } bool IsObjectShared () const { return m_bObjectShared; } void ObjectShared (bool bShared) { m_bObjectShared = bShared; } bool IsNull () const { return !HasObject(); } void Attach (T* pObj, bool bShared = false) { Detach(); if (pObj != NULL) { m_pObject = pObj; m_bObjectShared = bShared; } } void Detach (T** ppObject = NULL) { if (ppObject != NULL) { *ppObject = m_pObject; m_pObject = NULL; m_bObjectShared = false; } else { if (HasObject()) { if (!IsObjectShared()) delete m_pObject; m_pObject = NULL; m_bObjectShared = false; } } } void Detach (bool bDeleteIfNotShared) { if (HasObject()) { if (bDeleteIfNotShared && !IsObjectShared()) delete m_pObject; m_pObject = NULL; m_bObjectShared = false; } } bool IsEqualTo (const T * pOther) const { return (GetObject() == pOther); } public: T * operator -> () { ASSERT(HasObject()); return m_pObject; } const T * operator -> () const { ASSERT(HasObject()); return m_pObject; } T & operator * () { ASSERT(HasObject()); return *m_pObject; } const T & operator * () const { ASSERT(HasObject()); return (const C &)(*m_pObject); } operator T * () { return m_pObject; } operator const T * () const { return m_pObject; } operator bool() const { return (m_pObject!=NULL); } ObjectPtr<T>& operator = (T * pObj) { Attach(pObj, false); return *this; } bool operator == (const T * pOther) const { return IsEqualTo(pOther); } bool operator == (T * pOther) const { return IsEqualTo(pOther); } bool operator != (const T * pOther) const { return !IsEqualTo(pOther); } bool operator != (T * pOther) const { return !IsEqualTo(pOther); } bool operator == (const ObjectPtr<T>& other) const { return IsEqualTo(other.GetObject()); } bool operator != (const ObjectPtr<T>& other) const { return !IsEqualTo(other.GetObject()); } bool operator == (int pv) const { return (pv==NULL)? IsNull() : (LPVOID(m_pObject)==LPVOID(pv)); } bool operator != (int pv) const { return !(*this == pv); } private: T * m_pObject; bool m_bObjectShared; }; // Some concrete type that holds useful data class SomeUsefulData { public: SomeUsefulData () {} ~SomeUsefulData () {} }; // Some concrete type that holds a heap-allocated instance of // SomeUsefulData class SomeContainer { public: SomeContainer (SomeUsefulData* pUsefulData) { m_pData = pUsefulData; } ~SomeContainer () { // nothing to do here } public: bool EvaluateSomeCondition () { // fake condition check to give us an expression // to use in ?: operator below return true; } SomeUsefulData* Foo () { // this usage of the ?: operator generates a C2248 // error b/c it's attempting to call the copy // constructor on ObjectPtr<T> return EvaluateSomeCondition() ? m_pData : NULL; /**********[ DISCUSSION ]********** The following equivalent constructs compile w/out error and behave correctly: (1) explicit cast to SomeUsefulData* as a comiler hint return EvaluateSomeCondition() ? (SomeUsefulData *)m_pData : NULL; (2) if/else instead of ?: if (EvaluateSomeCondition()) return m_pData; else return NULL; (3) skip the condition check and return m_pData as a SomeUsefulData* directly return m_pData; **********[ END DISCUSSION ]**********/ } private: ObjectPtr<SomeUsefulData> m_pData; }; int _tmain(int argc, _TCHAR* argv[]) { return 0; }

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  • Proper exceptions to use for nulls

    - by user200295
    In the following example we have two different exceptions we want to communicate. //constructor public Main(string arg){ if(arg==null) throw new ArgumentNullException("arg"); Thing foo=GetFoo(arg); if(foo==null) throw new NullReferenceException("foo is null"); } Is this the proper approach for both exception types?

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  • IoC Dependancy injection into Custom HTTP Module - how? (ASP.NET)

    - by Sosh
    Hi, I have a custom HTTP Module. I would like to inject the logger using my IoC framework, so I can log errors in the module. However, of course I don't get a constructor, so can't inject it into that. What's the best way to go about this? If you need the specific IoC container - I'm currently using Windsor, but may soon move to AutoFac. Thanks

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  • javax.activation.DataSource size question

    - by folone
    How do I get the amount of physical memory, consumed by the DataSource (specifically — ByteArrayDataSource)? I use ByteArrayDataSource (byte[] bytes, String type) constructor, where I get bytes like this: String str = "test"; byte[] bytes = str.getBytes(); Would that be str.length() in bytes? Any other ideas?

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  • __proto__ of a function

    - by alter
    if I have a class called Person. var Person = function(fname, lname){ this.fname = fname; this.lname = lname; } Person.prototype.mname = "Test"; var p = new Person('Alice','Bob'); Now, p.proto refers to prototype of Person but, when I try to do Person.proto , it points to function(), and Person.constructor points to Function(). can some1 explain what is the difference between function() and Function() and why prototype of a Function() class is a function()

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  • CursorLoader, get URI for local database

    - by user1681358
    I'm a newbie android programmer and I recently followed a tutorial which shows how to create a local SQLite database by using SQLiteDatabase.rawQuery to return a Cursor. I would like to modify my app to use CursorLoader which is apparently a better way to access the database. My problem is the CursorLoader constructor expects a URI to be given. Do I just input "file:///[path to db]"? Seems a bit messy.

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  • Are reference attributes destroyed when class is destroyed in C++?

    - by Genba
    Suppose I have a C++ class with an attribute that is a reference: class ClassB { ClassA &ref; public: ClassB(ClassA &_ref); } Of course, the constructor is defined this way: ClassB::ClassB(ClassA &_ref) : ref(_ref) { /* ... */ } My question is: When an instance of class 'ClassB' is destroyed, is the object referenced by 'ClassB::ref' also destroyed?

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  • c# 3.5 class List<int> class initialisation

    - by josephj1989
    I can initialize a List like new List{1,2,3,4,5}; However List does not have a constructor which accepts a single parameter. So I tried to run this through the debugger and it seems to be calling the Add method. So how does the compiler know which method to invoke to add each individual element. This may be a silly question but I am a bit confused. Thanks

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  • How to generate a random BigInteger value in Java?

    - by Bill the Lizard
    I need to generate arbitrarily large random integers in the range 0 (inclusive) to n (exclusive). My initial thought was to call nextDouble and multiply by n, but once n gets to be larger than 253, the results would no longer be uniformly distributed. BigInteger has the following constructor available: public BigInteger(int numBits, Random rnd) Constructs a randomly generated BigInteger, uniformly distributed over the range 0 to (2numBits - 1), inclusive. How can this be used to get a random value in the range 0 - n, where n is not a power of 2?

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  • How to print structures in PLT Scheme so as to display their fields?

    - by tkf
    I would like code like this: (define-struct thing (a b c)) (define th (make-thing 1 2 3)) to print something like this: (make-thing 1 2 3) when I type "th" into either the DrScheme or MzScheme repl. I am using the language "pretty big" in DrScheme with output style set to "constructor". This is what I get in DrScheme: (make-thing ...) (i literally get the three dots) In MzScheme: #<thing>

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  • .NET: Start a thread as suspended

    - by Ikaso
    In unmanaged code you can create a thread in suspended state. In .NET Framework I can't find this option. Is it because the Thread constructor puts the thread in a suspended state? Is there other reasons why this is not supported?

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  • C++: type Length from float

    - by anon
    This is kinda like my earlier question: http://stackoverflow.com/questions/2451175/c-vector3-type-wall Except, now, I want to do this to a builtin rather then a user created type. So I want a type "Length" that behaves just like float -- except I'm going to make it's constructor explicit, so I have to explicitly construct Length objects (rather than have random conversions flying around). Basically, I'm going into the type-a-lot camp.

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  • Is it possible to create a C++ factory system that can create an instance of any "registered" object

    - by chrensli
    Hello, I've spent my entire day researching this topic, so it is with some scattered knowledge on the topic that i come to you with this inquiry. Please allow me to describe what I am attempting to accomplish, and maybe you can either suggest a solution to the immediate question, or another way to tackle the problem entirely. I am trying to mimic something related to how XAML files work in WPF, where you are essentially instantiating an object tree from an XML definition. If this is incorrect, please inform. This issue is otherwise unrelated to WPF, C#, or anything managed - I solely mention it because it is a similar concept.. So, I've created an XML parser class already, and generated a node tree based on ObjectNode objects. ObjectNode objects hold a string value called type, and they have an std::vector of child ObjectNode objects. The next step is to instantiate a tree of objects based on the data in the ObjectNode tree. This intermediate ObjectNode tree is needed because the same ObjectNode tree might be instantiated multiple times or delayed as needed. The tree of objects that is being created is such that the nodes in the tree are descendants of a common base class, which for now we can refer to as MyBase. Leaf nodes can be of any type, not necessarily derived from MyBase. To make this more challenging, I will not know what types of MyBase derived objects might be involved, so I need to allow for new types to be registered with the factory. I am aware of boost's factory. Their docs have an interesting little design paragraph on this page: o We may want a factory that takes some arguments that are forwarded to the constructor, o we will probably want to use smart pointers, o we may want several member functions to create different kinds of objects, o we might not necessarily need a polymorphic base class for the objects, o as we will see, we do not need a factory base class at all, o we might want to just call the constructor - without #new# to create an object on the stack, and o finally we might want to use customized memory management. I might not be understanding this all correctly, but that seems to state that what I'm trying to do can be accomplished with boost's factory. But all the examples I've located, seem to describe factories where all objects are derived from a base type. Any guidance on this would be greatly appreciated. Thanks for your time!

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  • In C++, what happens when you return a variable?

    - by wowus
    What happens, step by step, when a variable is returned. I know that if it's a built-in and fits, it's thrown into rax/eax/ax. What happens when it doesn't fit, and/or isn't built-in? More importantly, is there a guaranteed copy constructor call? edit: What about the destructor? Is that called "sometimes", "always", or "never"?

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