[Bug c++/50929] New: [C++0x] Wrong function selected for overload with template and rvalue reference

[jarrydb at cse dot unsw.edu.au]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50929

             Bug #: 50929
           Summary: [C++0x] Wrong function selected for overload with
                    template and rvalue reference
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jarrydb@cse.unsw.edu.au


When choosing between a constructor

  A(const A& a)

and

  template <typename T>
  A(T&& t)

given an object of type A&, the compiler chooses the second function. For the
following code:

class A
{
  public:
  A() : value(0) {}

  A(const A& rhs) : value(1) { }

  A(A&& rhs) : value(2) { }

  template <typename T>
  A(T&& t) : value(3) { }

  int value;
};

int main()
{
  A a;
  A b = a;
  return b.value;
}

compiled with:
  g++ -std=gnu++0x rvalue_deduction.cpp

then running:
  ./a.out
  echo $?

the output is 
  3

I expect the output to be 1, not 3.


Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/home/jarrydb/current/soft/install-latest/libexec/gcc/x86_64-unknown-linux-gnu/4.7.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /home/jarrydb/current/soft/src/gcc-git/configure
--prefix=/home/jarrydb/current/soft/install-latest --disable-multilib
--enable-languages=c,c++
Thread model: posix
gcc version 4.7.0 20111027 (experimental) (GCC)