lvalue-to-rvalue Questions
3
Solved
Today I ran into roughly the following code:
#include <iostream>
void f(float&& f) { std::cout << f << "f "; }
void f(int&& i) { std::cout <<...
Mayman asked 8/11, 2023 at 12:8
3
Solved
I see the term "lvalue-to-rvalue conversion" used in many places throughout the C++ standard. This kind of conversion is often done implicitly, as far as I can tell.
One unexpected (to me...
Cho asked 31/12, 2013 at 1:52
1
Solved
I'm encountering an unexpected behavior in my code when calling overloaded functions with different rvalue reference types. The code snippet below demonstrates the issue:
#include <iostream>
...
Rensselaerite asked 30/6, 2023 at 2:23
4
$4.2/1 - "An lvalue or rvalue of type
“array ofN T” or “array of unknown
bound of T” can be converted to an
rvalue of type “pointer to T.” The
result is a pointer to the first
element of the...
Scoutmaster asked 7/9, 2010 at 7:49
1
Solved
Consider a C++20 program where in function foo there is a structured binding auto [y]. The function returns y, which is converted in object of type A. A can be constructed either from const referen...
Anticipatory asked 26/8, 2021 at 15:32
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
Solved
The question related to this one. By tracing slt_pair. h and move. h, it's seems that the difference between Clang and G++ is internally. I have tried to simulate the assignment of the object (pair...
Peluso asked 1/6, 2020 at 8:42
1
Solved
Practically every example of lvalue-to-rvalue conversion I've seen on the web relates to fundamental types like int etc.
I couldn't find an example of l2r applicable to class types myself; in all t...
Bissextile asked 2/4, 2020 at 4:55
3
Solved
I'm writing a C compiler which follows this standard, and if I parse statements like this:
int i;
(i) = 1;
my compiler will report an error which point out that (i) is a rvalue and should not be...
Digitigrade asked 12/10, 2019 at 9:13
1
Solved
Is a C implementation required to ignore undefined behaviors occurring during the evaluation of void expressions as if the evaluation itself never took place?
Considering C11, 6.3.2.2 §1:
If an...
Carafe asked 24/7, 2019 at 12:12
2
Solved
The following function returns an rvalue:
int foo()
{
int x = 42;
return x; // x is converted to prvalue
}
Clang's AST also shows the conversion:
`-FunctionDecl <line:1:1, line:5:1> lin...
Turret asked 25/4, 2018 at 14:19
1
In the C++14 standard (n3797), the section on lvalue to rvalue conversions reads as follows (emphasis mine):
4.1 Lvalue-to-rvalue-conversion [conv.lval]
A glvalue (3.10) of a non-function, ...
Regulus asked 6/9, 2017 at 1:10
1
Solved
Say I have the following function
void doWork(Widget && param) // param is an LVALUE of RRef type
{
Widget store = std::move(param);
}
Why do I need to cast param back to an rval...
Malaysia asked 23/8, 2017 at 15:33
2
Solved
EDIT: Consider 2 following examples:
std::string x;
{
std::string y = "extremely long text ...";
...
x = y; // *** (1)
}
do_something_with(x);
struct Y
{
Y();
Y(const Y&);
Y(Y&&a...
Toothpick asked 19/7, 2017 at 1:21
2
Solved
class Test {
public:
int n1;
};
Test func() {
return Test();
}
int main() {
func() = Test();
}
This doesn't make sense to me. How and why is this allowed? Is it undefined behavior? If...
Kendo asked 13/2, 2016 at 9:11
2
Solved
Why is this code compiling? I thought that rvalues returned by the constructor are not located in memory and therefore can't be used as lvalues.
class Y {
public :
explicit Y(size_t num = 0) {}
};...
Matthewmatthews asked 17/1, 2016 at 6:13
1
Solved
I have a hard time understanding how this code (an example from the C++14 draft standard [conv.lval]) invokes undefined behavior for g(false). Why does constexpr make the program valid?
Also, wh...
Loydloydie asked 13/2, 2015 at 18:34
3
Solved
In the following code, I'm not able to pass a temporary object as argument to the printAge function:
struct Person {
int age;
Person(int _age): age(_age) {}
};
void printAge(Person &person)...
Runic asked 27/11, 2014 at 13:38
2
I'm trying to understand the conditions on std::swap from [C++11: utility.swap]. The template is defined as
template <typename T> void swap(T &, T &)
(plus some noexcept details) a...
Watchmaker asked 20/6, 2014 at 21:26
2
Solved
I've been reading quite many on the Internet and it seems that many people mentioned the following rules (but i couldn't find it in the standard),
The addition operator + (and all other binary ope...
Fealty asked 24/2, 2011 at 2:39
2
Solved
TL;DR
Given the following code:
int* ptr;
*ptr = 0;
does *ptr require an lvalue-to-rvalue conversion of ptr before applying indirection?
The standard covers the topic of lvalue-to-rvalue in ma...
Abroms asked 10/1, 2014 at 19:53
2
Solved
I have three function calls that I think should be treated (about) the same, but clearly they are not. I'm trying to understand why one of three doesn't compile (g++ -std=c++0x).
// Minimal exampl...
Inapposite asked 13/1, 2012 at 13:57
2
Solved
C++03 §4.2 N°1:
An lvalue or rvalue of type “array of N T” or “array of unknown bound of T” can be converted to an rvalue of type “pointer to T.” The result is a pointer to the first element of the...
Pulsate asked 30/10, 2010 at 10:0
1
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