[cfe-dev] Clang bug under C++11 with new standard library

[Adam Peterson]

(Thanks to the guys at llvmdev at ... for pointing me here.)

I have a short 15-line C++ program using only one standard header that
clang fails to compile properly under C++11 with the new standard
library (although the code itself doesn't use any C++11-specific
syntax).  G++ (and Clang under C++98/03, or without the new standard
library) compiles it fine:

    #include <map>
    using std::map;

    template<typename K>
    struct Templ8 {
        struct Member {
            typename map<K,Member*>::iterator it;
        };
        typedef typename map<K,Member*>::iterator iterator_type;
    };

    int main() {
        Templ8<int> test;
    }



This is the command-line:
    clang++ -stdlib=libc++ -std=c++11 main_bug.cpp
If either of the flags are removed (to compile in C++03 mode, or to
use the non-clang standard library), the code compiles.  If the
typedef is removed or commented out, clang++ compiles the code fine.
If the typedef is moved inside the "Member" inner class, the code
compiles fine (even if a second typedef pulls the symbol back into the
main template scope).

My clang version information:
    Apple clang version 4.1 (tags/Apple/clang-421.11.65) (based on LLVM 3.1svn)
    Target: x86_64-apple-darwin12.2.0
    Thread model: posix

The error output:

main_bug.cpp:7:34: error: no type named 'iterator' in
'std::__1::map<int, Templ8<int>::Member *, std::__1::less<int>,
std::__1::allocator<std::__1::pair<const int, Templ8<int>::Member
*>>>'
        typename map<K,Member*>::iterator it;
        ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
/usr/bin/../lib/c++/v1/type_traits:1184:57: note: in instantiation of
member class 'Templ8<int>::Member' requested here
decltype((_VSTD::declval<_Tp>() = _VSTD::declval<_Arg>(),
true_type()))
                                                        ^
/usr/bin/../lib/c++/v1/type_traits:1186:1: note: while substituting
deduced template arguments into function template
'__is_assignable_test' [with _Tp = Templ8<int>::Member *&, _Arg = <no
value>]
__is_assignable_test(_Tp&&, _Arg&&);
^
/usr/bin/../lib/c++/v1/type_traits:1214:14: note: in instantiation of
template class 'std::__1::__is_assignable_imp<Templ8<int>::Member *&,
Templ8<int>::Member *&, false>' requested here
    : public __is_assignable_imp<_Tp, _Arg> {};
             ^
/usr/bin/../lib/c++/v1/type_traits:2616:38: note: in instantiation of
template class 'std::__1::is_assignable<Templ8<int>::Member *&,
Templ8<int>::Member *&>' requested here
    : public __is_nothrow_assignable<is_assignable<_Tp, _Arg>::value, _Tp, _Arg>
                                     ^
/usr/bin/../lib/c++/v1/type_traits:2667:14: note: in instantiation of
template class 'std::__1::is_nothrow_assignable<Templ8<int>::Member
*&, Templ8<int>::Member *&>' requested here
    : public is_nothrow_assignable<typename add_lvalue_reference<_Tp>::type,
             ^
/usr/bin/../lib/c++/v1/utility:250:20: note: (skipping 9 contexts in
backtrace; use -ftemplate-backtrace-limit=0 to see all)
                   is_nothrow_copy_assignable<second_type>::value)
                   ^
/usr/bin/../lib/c++/v1/__config:253:34: note: expanded from macro '_NOEXCEPT_'
#  define _NOEXCEPT_(x) noexcept(x)
                                 ^
/usr/bin/../lib/c++/v1/memory:2386:15: note: in instantiation of
template class 'std::__1::__libcpp_compressed_pair_imp<std::__1::__tree_end_node<std::__1::__tree_node_base<void
*> *>,
      std::__1::allocator<std::__1::__tree_node<std::__1::pair<int,
Templ8<int>::Member *>, void *>>, 2>' requested here
    : private __libcpp_compressed_pair_imp<_T1, _T2>
              ^
/usr/bin/../lib/c++/v1/__tree:813:56: note: in instantiation of
template class 'std::__1::__compressed_pair<std::__1::__tree_end_node<std::__1::__tree_node_base<void
*> *>,
      std::__1::allocator<std::__1::__tree_node<std::__1::pair<int,
Templ8<int>::Member *>, void *>>>' requested here
    __compressed_pair<__end_node_t, __node_allocator>  __pair1_;
                                                       ^
/usr/bin/../lib/c++/v1/map:711:22: note: in instantiation of template
class 'std::__1::__tree<std::__1::pair<int, Templ8<int>::Member *>,
std::__1::__map_value_compare<int, Templ8<int>::Member *,
      std::__1::less<int>, true>,
std::__1::allocator<std::__1::pair<int, Templ8<int>::Member *>>>'
requested here
    typedef typename __base::__node_traits                 __node_traits;
                     ^
main_bug.cpp:9:22: note: in instantiation of template class
'std::__1::map<int, Templ8<int>::Member *, std::__1::less<int>,
std::__1::allocator<std::__1::pair<const int, Templ8<int>::Member
*>>>'
      requested here
    typedef typename map<K,Member*>::iterator iterator_type;
                     ^
main_bug.cpp:13:17: note: in instantiation of template class
'Templ8<int>' requested here
    Templ8<int> test;
                ^
1 error generated.