rvalue-reference Questions
2
In Effective Modern C++ item 12, there is a sample code about the C++11 functions' reference qualifiers:
class Widget {
public:
using DataType = std::vector<double>;
…
DataType& ...
Edging asked 26/1, 2019 at 13:48
1
Solved
I have a really simple function definition here:
void testRvalue(int&& r)
{
printf("rvalue ref is called\n");
testRvalue(r); // this line gives "no known conversion f...
Pennsylvanian asked 10/2, 2021 at 5:30
4
I suppose when a universal reference parameter is matched with an rvalue reference argument, an rvalue reference argument is returned. However, my testing shows that the rvalue reference is t...
Iranian asked 28/12, 2016 at 11:13
1
Reading Why does as_const forbid rvalue arguments? I understand that we can't convert a rvalue-ref into an lvalue-ref, of course.
But why not move the rvalue-ref into a value and return that, i.e. ...
Lulita asked 14/1, 2021 at 9:47
3
Solved
This is an rvalue reference:
void foo(int&& a);
It does not bind to lvalues:
int i = 42;
foo(i); // error
This is a universal reference:
template<typename T>
void bar(T&a...
Semiology asked 13/1, 2013 at 11:7
2
Solved
I have a struct F with a function foo that has different implementation whether F is a temporary or not
struct F{
void foo() & { std::cout << "F::foo() &" << std::end...
Preamble asked 14/10, 2020 at 11:28
2
Solved
I'm familiar, that the append in std::string returns std::string& and therefore it do not qualify to be moved from, so the result will not be moved.
#include <string>
int main()
{
std:...
Pythagoras asked 21/7, 2020 at 9:48
1
Solved
I have recently learned about r-value references. In order to more thoroughly experiment I decided to write a simple DenseMatrix class. My question is is it possible to write any function ( Transpo...
Gethsemane asked 17/7, 2020 at 16:50
1
Solved
According to en.cppreference.com (from what I can gather):
std::is_convertible is a trait class requiring types From & To to be such that a function with return type To that returns a From val...
Unrig asked 29/6, 2020 at 17:58
1
So basically my question is: When should I use an rvalue reference?
In this example, I'm working on a logger class (it just logs things to the console...). I have different functions to log message...
Sync asked 3/6, 2020 at 14:48
2
Solved
#include <utility>
template <typename Container>
decltype(auto) index(Container &&arr, int n) {
return std::forward<Container>(arr)[n];
}
Make a function call :
#inclu...
Soares asked 3/6, 2020 at 5:38
2
Solved
Consider the following function accept that takes a "universal reference" of type T and forwards that to a parse<T>() function object with an overload for lvalues and one for rvalues:
templa...
Indulgence asked 25/11, 2013 at 14:44
2
Solved
I've been switching Template Factory functions to use (and understand) std::forward to support rvalues and move semantics. My usual boilerplate factory functions for template classes have always ma...
Alvord asked 7/2, 2013 at 1:31
2
Solved
A note: this is an API design question, riding on the design of the constructors of unique_ptr and share_ptr for the sake of the question, but not aiming to propose any change to their current spec...
Tab asked 4/3, 2020 at 21:33
5
Solved
I think there's something I'm not quite understanding about rvalue references. Why does the following fail to compile (VS2012) with the error 'foo' : cannot convert parameter 1 from 'int' to 'int &...
Lifework asked 26/9, 2012 at 16:47
3
Solved
Consider the code below
void foo(std::vector<int> v)
{
//do something here
}
//calling the function
vector<int> v1 = {1,2,3};
foo(std::move(v1));
My question is, isn't the function ...
Respiration asked 20/1, 2020 at 20:52
2
Solved
Example:
typedef enum Color
{
RED,
GREEN,
BLUE
} Color;
void func(unsigned int& num)
{
num++;
}
int main()
{
Color clr = RED;
func(clr);
return 0;
}
I get the following error when I...
Doone asked 31/12, 2019 at 7:6
3
Solved
I found that lvalue lambda closures can always be passed as rvalue function parameters.
See the following simple demonstration.
#include <iostream>
#include <functional>
using namesp...
Scotopia asked 12/11, 2019 at 12:23
2
Solved
I was reading a book about data structure implemented in C++, I dont understand a code snippet， it's part of vector class
void push_back(object &&x) {
//do something
objects[size++] = s...
Grubb asked 8/11, 2019 at 5:54
3
Solved
In C++11, value parameters (and other values) enjoy implicit move when returned:
A func(A a) {
return a; // uses A::A(A&&) if it exists
}
At least in MSVC 2010, rvalue reference paramet...
Pyromania asked 19/3, 2012 at 22:49
1
Solved
I was always assuming that std::move() on a std::shared_ptr steals the pointer and sets the pointer of the original to nullptr-thus not increasing the reference count. That does not seem to be true...
Arleta asked 9/9, 2019 at 10:29
3
Solved
#include <set>
#include <string>
#include <cassert>
using namespace std::literals;
int main()
{
auto coll = std::set{ "hello"s };
auto s = "hello"s;
coll.insert(std::move(s))...
Antiquated asked 15/8, 2019 at 15:12
3
Solved
Using the return value of operator* from a "dead" unique_ptr is bad.
The following code compiles but results of course in Undefined Behavior:
auto& ref = *std::make_unique<int>(...
Scutum asked 24/7, 2019 at 14:36
4
Solved
I read that this is an rvalue and we cannot get its address by applying &this.
In my code, I have tried to use a reference binding to this. I'm wondering which way will give the address of thi...
Footstep asked 1/7, 2019 at 9:16
1
Solved
Let's consider the following code:
class X {
std::vector<int> _v;
public:
X(std::vector<int>&& v): _v(std::move(v)) {}
};
The compiler calls this constructor only for objec...
Popelka asked 30/6, 2019 at 18:24
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