<html>
    <head>
      <base href="https://llvm.org/bugs/" />
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - clang rejects valid C++ code with nested template classes"
   href="https://llvm.org/bugs/show_bug.cgi?id=28404">28404</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>clang rejects valid C++ code with nested template classes
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>C++
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>su@cs.ucdavis.edu
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>dgregor@apple.com, llvm-bugs@lists.llvm.org
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>The current clang trunk rejects the following valid C++ test case (which is
accepted by GCC) on x86_64-linux-gnu in both 32-bit and 64-bit modes. 

It is accepted by 3.1, and rejected by 3.2 and later. 


$ clang++-trunk -v
clang version 3.9.0 (trunk 274430)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/tools/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.1.1
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

$ g++-6.1 -c -Wall -Wextra -pedantic -std=c++11 small.cpp

$ clang++-trunk -c -std=c++11 small.cpp
small.cpp:10:27: warning: dependent nested name specifier 'A<X>::B::' for
friend class declaration is not supported; turning off access control for 'S'
[-Wunsupported-friend]
  friend void A < X >::B::operator= (Y);
              ~~~~~~~~~~~~^
small.cpp:10:24: error: no member 'A' in 'S<int>'; it has not yet been
instantiated
  friend void A < X >::B::operator= (Y);
                       ^
small.cpp:13:11: note: in instantiation of template class 'S<int>' requested
here
S < int > s; 
          ^
small.cpp:3:29: note: not-yet-instantiated member is declared here
  template < class > struct A
                            ^
1 warning and 1 error generated.



----------------------------------------------


template < class > struct S
{
  template < class > struct A
  {
    struct B {};
  };

  template < class X > 
  template < class Y > 
  friend void A < X >::B::operator= (Y);
};

S < int > s;</pre>
        </div>
      </p>
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