[Bug libstdc++/60555] New: std::system_category().default_error_condition() doesn't map system errno values to std::generic_category()

["c.m.brandenburg at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60555

            Bug ID: 60555
           Summary: std::system_category().default_error_condition()
                    doesn't map system errno values to
                    std::generic_category()
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: c.m.brandenburg at gmail dot com

Created attachment 32376
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32376&action=edit
Program that exposes the bug.

According to the C++ standard, if the value ev corresponds to the POSIX errno
value posv, then std::system_category().default_error_condition(ev) should
return std::error_condition(posv, generic_category()). The libstdc++
implementation doesn't do this. Instead, it always returns
std::error_condition(ev, std::system_category()).

Attached is a program that exposes this bug. I've seen this problem on 4.7.2,
but an inspection of the source code for 4.8.2 suggests the bug exists for that
version too.