[llvm-bugs] [Bug 28490] New: clang accepts illegal C++ code with ambiguous member lookup

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=28490

            Bug ID: 28490
           Summary: clang accepts illegal C++ code with ambiguous member
                    lookup
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: su at cs.ucdavis.edu
                CC: dgregor at apple.com, llvm-bugs at lists.llvm.org
    Classification: Unclassified

The current clang trunk (and all versions at least as early as 2.9) accepts the
following C++ code, which should be illegal according to the C++ standard
because of ambiguous member lookup.  

It is rejected by both GCC and MSVC (but accepted by ICC). 


$ clang++ -v
clang version 3.9.0 (trunk 274972)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/clang-trunk/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 small.cpp
small.cpp: In instantiation of ‘void C<T>::f() [with T = int]’:
small.cpp:13:7:   required from here
small.cpp:7:16: error: request for member ‘i’ is ambiguous
   void f () {  i ();  }
                ^
small.cpp:3:18: note: candidates are: void B::i()
 struct B {  void i () {}  };
                  ^
small.cpp:1:36: note:                 int A<int>::i
 template < class > struct A {  int i;  };
                                    ^
$ 
$ clang++-2.9 -c small.cpp
$      
$ clang++ -c small.cpp
$ 


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


template < class > struct A {  int i;  };

struct B {  void i () {}  };

template < class T > struct C : A < T >, B
{
  void f () {  i ();  }
}; 

int main ()
{
  C < int > c;
  c.f(); 
  return 0;
}

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