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Questions tagged [rvalue-reference]

An rvalue reference is a new language feature in C++11 representing a reference to an rvalue. Together with reference collapsing, they are used to implement and enable move semantics and perfect forwarding.

An rvalue reference is a language feature added in C++11 (formerly known as C++0x). It is used to bind to an rvalue thus extending the temporary object's lifetime.

Together with reference collapsing, they are used to implement and enable move semantics and perfect forwarding.

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Where are rvalues stored in C++?

I'm learning new C++ 11 features recently. However, I don't fully understand one thing about rvalues. Consider following code: string getText () { return "Fabricati diem"; } string newText = getText(); Call to getText() creates an r-value…
Kao
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Pass by reference, constant reference, rvalue-reference, or constant rvalue-reference?

I was learning passing by reference, and here is the test I did: #include using namespace std; int i = 0; //If this is uncommented, compiler gives ambiguous definition error. //void paramCheck (string s) { // cout << ++i << ". Param…
SwiftMango
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Perfect forwarding for void and non-void returning functions

Previously I was using a macro to measure the time a function call took whenever I wanted to quickly check that. Now, with C++11 available, I would like to finally remove that ugly peace of preprocessor code and replace it with something like…
user2573221
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C++ constructor with rvalue reference

Consider this class with three constructors: class Circle { public: Circle(int r) { _radius = r; } Circle(const Circle& c){ _radius = c.radius(); cout << endl << "Copy constructor with lvalue reference. Radius: " <<…
PoP
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C++: What are R-Value references on a technical level (ASM)?

Possible Duplicate: What is the difference between r-value references and l-value references? (CodeGen) I was wondering, can anyone explain what R-Value references are on a technical level? By that I mean: What happens on assembler level when…
PuerNoctis
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Are moved-from objects required to be destructed?

If I move-construct a from b, is it still necessary to destruct b, or can I get away without doing so? This question crossed my mind during the implementation of an optional template. Excerpt: ~optional() { if (initialized) { …
fredoverflow
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Rvalue reference or lvalue?

I've got a question of similiar nature like this one posted 5 years ago: Why are rvalues references variables not rvalue? My major concern is why can I do this: int&& k = 3; k++; but I cannot do this: (static_cast(3))++; I've always…
domdrag
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C++11 vector makes copies on rvalue

I have some strange behavior on std::vector with adding rvalues: #include #include class A { public: A():i_{5}{std::cout << "default" << std::endl;} A(const A &data) { std::cout << "copied!" << std::endl; } A(A…
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Can someone explain rvalue references with respect to exceptions?

Lets say I've this exception class: struct MyException : public std::exception { MyException(const std::exception &exc) : std::exception(exc) { cout << "lval\n"; } MyException(std::exception &&exc) :…
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C++: conversions of lvalue references and rvalue references

I wonder which parts of the standard specify that in the following code segment: #include class A { }; class B : public A { }; int main() { std::unique_ptr bptr = std::make_unique(); // (a) std::unique_ptr aptr =…
apriori
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Passing rvalue as reference

I have some Qt code that I downloaded from my svn repo. It's a while since I worked on it but I am sure it used to compile. I have a new version of Qt and compiler (to what I had in the last time). My current compiler is: mingw 4.9.2 32-bit. So here…
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Qt 5: unable to declare signal that takes rvalue reference

Probably I've missed something, but I can't find any information that signals can't take rvalue references. So, I have a class with the following signal declaration: signals: void messageDecoded(HTDataMsg &&msg); When I try to compile it, I got…
Dmitry Frank
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Overload between rvalue reference and const lvalue reference in template

I want to overload two functions based on whether the argument is a temporary object, so I write code like this: #include void f(int &&) { std::cout << "&&" << std::endl; } void f(const int&) { std::cout << "const &" <<…
delphifirst
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Problem with "moveable-only types" in VC++ 2010

I recently installed Visual Studio 2010 Professional RC to try it out and test the few C++0x features that are implemented in VC++ 2010. I instantiated a std::vector of std::unique_ptr, without any problems. However, when I try to populate it by…
Luc Touraille
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Using rvalue references for default arguments

I want to make a function that takes an optional reference to an object, and creates one for the duration of the function if it is not provided, i.e. void Foo(Bar& b = Bar()) { /* stuff */ } This is, of course, invalid code, as a Bar cannot be…
Matt Kline
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