[Bug c++/64385] New: odd behaviour of std::is_move_constructible< std::ostringstream >

[alan at birtles dot org.uk]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64385

            Bug ID: 64385
           Summary: odd behaviour of std::is_move_constructible<
                    std::ostringstream >
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alan at birtles dot org.uk

Created attachment 34320
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34320&action=edit
file to reproduce the bug

When compiling the attached code without "A" defined the code outputs 0, 0
which is expected as std::ostringstream doesn't have a move constructor in gcc
4.9. However when "A" is defined the code outputs 1, 1 which is incorrect.
Compiled with "g++ test.cpp -std=c++11 -D A" on Ubuntu 14.10.
g++ --version:
g++ (Ubuntu 4.9.1-16ubuntu6) 4.9.1