rvalue-reference Questions

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I have TTempTable class with move symantics. I wrote TTempTable&& MyFunction() { TTempTable tmp = f(...); ... return std::move(tmp); } and got no compiler errors. Was this corr...
Wolsky asked 27/5, 2019 at 12:53

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I know that a named reference is an lvalue: int x = 1; int& ref1 = x; int&& ref2 = std::move(x); I've read the explanation — that is because we can take the address of those re...
Algor asked 26/5, 2019 at 19:35

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I'm trying to understand rvalue references. I have seen how they are used in constructors, with things like std::move and std::forward, but I still don't understand why this doesn't work: void fun...
Ihram asked 20/5, 2015 at 3:47

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What's the difference in practice between LVALUE and RVALUE in the following code when I pass the text? I mean, in this specific case of a string (where the string is a string literal), is there an...
Poltroon asked 10/4, 2019 at 18:56

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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)...
Flores asked 7/1, 2016 at 12:49

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I'm trying to understand rvalue references and move semantics of C++11. What is the difference between these examples, and which of them is going to do no vector copy? First example: std::vector&lt...
Heliacal asked 13/2, 2011 at 20:28

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I have encountered code which does this: SomeObject parse (std::istream && input) {.... The input argument is an rvalue reference, which normally means the function is intended to take o...
Inter asked 16/1, 2019 at 15:56

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Since we have move semantics in C++, nowadays it is usual to do void set_a(A a) { _a = std::move(a); } The reasoning is that if a is an rvalue, the copy will be elided and there will be just one...
Mclaurin asked 10/1, 2014 at 2:56

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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 messageDecode...
Analyze asked 16/6, 2015 at 17:5

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When given code of the following structure template <typename... Args> void foo(Args&&... args) { ... } I've often seen library code use static_cast<Args&&> within th...
Involution asked 12/11, 2018 at 7:50

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Background and Previous Search I'm looking for an elegant way to reverse-iterate over a container (e.g. std::vector) using a range-based for-loop in C++14. Searching for a solution I found this Q/...
Velleman asked 9/10, 2018 at 13:34

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I can't do this: int &&q = 7; int &&r = q; //Error Message: //cannot convert from 'int' to 'int &&' //You cannot bind an lvalue to an rvalue reference If I understand co...
Hemidemisemiquaver asked 24/8, 2018 at 6:4

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A C++Next blog post said that A compute(…) { A v; … return v; } If A has an accessible copy or move constructor, the compiler may choose to elide the copy. Otherwise, if A has a move construc...
Idiopathy asked 17/11, 2012 at 13:1

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I was hoping stringstream has a constructor that steals its initial content from a string&&. Do such inter-species "move constructors" generally not exist in the STL? If not, why not?
Private asked 25/6, 2018 at 0:19

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In several places I've seen the recommended signatures of copy and move constructors given as: struct T { T(); T(const T& other); T(T&& other); }; Where the copy constructor takes...
Eclosion asked 26/5, 2012 at 22:11

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What is the meaning of the following line? Why is this allowed as 0 is an r-value and not a variable name? What is the significance of const in this statement? const int &x = 0;
Copperplate asked 15/5, 2018 at 21:35

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I wonder how the following can be done void f(string &&s) { std::string i(move(s)); /* other stuff */ } int main() { std::string s; bind(f, s)(); // Error. bind(f, move(s))(); ...
Erzurum asked 26/2, 2011 at 9:55

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While trying to understand how rvalue references work I ended up with this piece of code: int* iptr = nullptr; int*&& irr = iptr; Compiling the above code gives the following error: e...
Calgary asked 20/4, 2018 at 7:56

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I suspect boost::optional's get_value_or was deprecated because it is unsafe if an rvalue is passed as the default parameter. However, it is occasionally useful to be able to reference the optional...
Elam asked 17/4, 2018 at 7:48

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for example: Beta_ab&& Beta::toAB() const { return move(Beta_ab(1, 1)); }
Babism asked 12/7, 2009 at 18:44

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I am reviewing some code like this, where A is a moveable type: // Returns true exactly when ownership of a is taken bool MaybeConsume(A&& a) { if (some condition) { Consume(std::move(a)...
Cyclograph asked 15/2, 2018 at 4:32

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I'm writing a network library and use move semantics heavily to handle ownership for file descriptors. One of my classes wishes to receive file descriptor wrappers of other kinds and take ownership...
Excavate asked 23/10, 2011 at 0:42

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Let's take std::pair<T1, T2> as an example. It has the following two constructors: constexpr pair( const T1& x, const T2& y ); // #1 template< class U1, class U2 > constexpr pa...

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According to cppreference.com, move has signature template< class T > typename std::remove_reference<T>::type&& move( T&& t ) noexcept; Why does it take a rvalue refe...
Cadaverous asked 17/12, 2017 at 5:5

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I have read these materials: What's the difference between std::move and std::forward std::move Vs std::forward this answer is very close to my question, but one is setImage, the other is r...
Spense asked 3/11, 2017 at 11:58

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