[Bug c++/34700] New: rvalue erroneously binding to non-const lvalue reference

[Bug c++/34700] New: rvalue erroneously binding to non-const lvalue reference

[eric dot niebler at gmail dot com]

Consider the following code, compiled with the latest gcc built from sources,
with the -std=c++0x flag:

#include <iostream>
struct S
{
    S() {}
    S(S &s) { std::cout << "L-value ref" << std::endl; }
    S(S &&s) { std::cout << "R-value ref" << std::endl; }
};

S source() { static S s; return s; }

int main()
{
    std::cout << "here 1 \n";
    S s;
    std::cout << "here 2 \n";
    S t(s);
    std::cout << "here 3 \n";
    S u(source()); // ERROR HERE
}

For me, this prints:

here 1
here 2
L-value ref
here 3
L-value ref

It should print:

here 1
here 2
L-value ref
here 3
R-value ref

An rvalue should under no circumstance bind to a non-const lvalue reference.


-- 
           Summary: rvalue erroneously binding to non-const lvalue reference
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: eric dot niebler at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34700

[Bug c++/34700] C++0x: rvalue erroneously binding to non-const lvalue reference

[dgregor at gcc dot gnu dot org]

------- Comment #1 from dgregor at gcc dot gnu dot org  2008-01-15 05:38 -------
This is not a bug. In the line that prints "L-value ref" where the reporter
expected "R-value ref", the call to the lvalue reference constructor that we're
seeing comes from inside the body of the source() function, which is returning
a reference to a static variable. Since the variable is static, it is treated
as an lvalue, and therefore we do a construction with S's lvalue constructor
(which prints out "L-value ref"). Then, we don't actually need to perform
another construction to build "u" (since we constructed the result of the call
to source() in place), so there is no "R-value ref" at the end of the output/


-- 

dgregor at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34700