Allowed to bind an rvalue to a non-const lvalue reference?

Question

In studying rvalues and rvalue references, I've been pointed to the excellent posting https://stackoverflow.com/a/11540204/368896, in which appears the following table:

            lvalue   const lvalue   rvalue   const rvalue
---------------------------------------------------------              
X&          yes
const X&    yes      yes            yes      yes
X&&                                 yes
const X&&                           yes      yes

Note that the table indicates that an rvalue cannot bind to a non-const lvalue reference.

However, in VS2010 I seem to be able to do so:

class A
{};

int main()
{
    A & a = A(); // Binding an rvalue to a non-const lvalue reference?
}

Where is my misunderstanding?

Try compiling with `/W4` it should give you a warning about the "evil extension". — Jesse Good, Dec 05 '12 at 23:47
Specifically, warning [C4239](http://msdn.microsoft.com/en-us/library/186yxbac.aspx). — ildjarn, Dec 06 '12 at 00:23

score 3 · Accepted Answer · answered Dec 05 '12 at 23:47

3

This is a compiler "extension" (or "bug", depending on your perspective) of the Microsoft compiler. C++ only allows non-const binding of an lvalue to a non-const lvalue reference.

answered Dec 05 '12 at 23:47

Kerrek SB

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Allowed to bind an rvalue to a non-const lvalue reference?

1 Answers1