[llvm-bugs] [Bug 35842] New: Clang 6 fails to compile boost variant code in unnamed namespace

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=35842

            Bug ID: 35842
           Summary: Clang 6 fails to compile boost variant code in unnamed
                    namespace
           Product: clang
           Version: 6.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: david at davidhallas.dk
                CC: dgregor at apple.com, llvm-bugs at lists.llvm.org

Created attachment 19640
  --> https://bugs.llvm.org/attachment.cgi?id=19640&action=edit
Simplified test case

Clang 6 fails to compile the simple example attached to the bug. It fails with
the following error:

In file included from test.cpp:1:
In file included from /usr/include/boost/variant/variant.hpp:30:
In file included from /usr/include/boost/variant/detail/initializer.hpp:21:
In file included from /usr/include/boost/detail/reference_content.hpp:19:
In file included from /usr/include/boost/type_traits/has_nothrow_copy.hpp:19:
In file included from
/usr/include/boost/type_traits/is_copy_constructible.hpp:17:
In file included from /usr/include/boost/type_traits/is_constructible.hpp:17:
In file included from /usr/include/boost/type_traits/is_destructible.hpp:19:
/usr/include/boost/type_traits/declval.hpp:40:44: error: function
'boost::declval<(anonymous namespace)::Pod &>' is used but not defined in this
translation unit, and cannot be defined in any other translation unit because
its
      type does not have linkage
    typename add_rvalue_reference<T>::type declval() BOOST_NOEXCEPT; // as
unevaluated operand
                                           ^
/usr/include/boost/variant/detail/apply_visitor_unary.hpp:112:30: note: used
here
        return vis()( boost::declval< value_t& >() );
                             ^
1 error generated.

If I move the Pod type out of the unnamed namespace it compiles fine. Also if
the visitor type is, say an int, it also compiles fine.

The same code compiles fine with clang-5 and gcc-6.

I have tested with boost-1.63.0 and boost-1.66.0 but with no difference.

The code is compiled with
clang++ -c test.cpp

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20180106/4598373f/attachment.html>