[Bug c++/53786] New: [C++11] alias template causes g++ segfault

[Bug c++/53786] New: [C++11] alias template causes g++ segfault

[mustrumr97 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53786

             Bug #: 53786
           Summary: [C++11] alias template causes g++ segfault
    Classification: Unclassified
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: mustrumr97@gmail.com


template<class... types>
class list{
    public:
        template<class t, class... ts>
        using tail_=list<ts...>;
        using tail=tail_<types...>;
};
using l=list<int>;

will make gcc 4.7.1 segfault
test.cpp:5:32: internal compiler error: Segmentation fault

[Bug c++/53786] [C++11] alias template causes g++ segfault

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53786

Daniel Krügler <daniel.kruegler at googlemail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |daniel.kruegler at
                   |                            |googlemail dot com

--- Comment #1 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-06-27 22:18:16 UTC ---
The problem still persists in gcc 4.8.0 20120624 (experimental):

"5|internal compiler error: tree check: accessed elt 2 of tree_vec with 1 elts
in tsubst_pack_expansion, at cp/pt.c:9374"

[Bug c++/53786] [C++11] alias template causes g++ segfault

[mustrumr97 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53786

--- Comment #2 from Hristo Venev <mustrumr97 at gmail dot com> 2012-06-30 15:19:29 UTC ---
Reduced:

template<class... x>
class list{};
template<class a, class... b>
using tail=list<b...>;
template<class... x>
using tail2=tail<x...>;

[Bug c++/53786] [C++11] alias template causes g++ segfault

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53786

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-07-25
     Ever Confirmed|0                           |1

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-07-25 09:45:23 UTC ---
Confirmed.

[Bug c++/53786] [C++11] alias template causes g++ segfault

[mustrumr97 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53786

--- Comment #4 from Hristo Venev <mustrumr97 at gmail dot com> 2012-12-19 13:51:08 UTC ---
That bug was fixed. However there is still another one:

template<class... Data>
struct List{};
template<class T, class... Ts>
using Tail=List<Ts...>;
template<class... Ts>
using Tail2=Tail<Ts...>;
using A=Tail2<int, char, char>;

fail.cpp: In substitution of ‘template<class T, class ... Ts> using Tail =
List<Ts ...> [with T = int; Ts = char]’:
fail.cpp:6:24:   required by substitution of ‘template<class ... Ts> using
Tail2 = Tail<Ts ...> [with Ts = {int, char, char}]’
fail.cpp:7:30:   required from here
fail.cpp:4:23: error: template argument 1 is invalid
 using Tail=List<Ts...>;
                       ^
In the diagnostic it is said that in the instantiation of Tail<int, char, char>
Ts is char, it should be {char, char} - a list of types, not a single type.

Additionally when `using A=Tail2<>;` (which is invalid) the compiler still
crashes.

[Bug c++/53786] [C++11] alias template - error on valid code

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53786

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-invalid-code

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> 2013-04-04 16:55:32 UTC ---
This looks like issue 1430:

  http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1430

As in the example in the issue description, here there is no way to express
tail_<types...> in terms of list and types, so I think this will also be
ill-formed.  Other people on the committee seem to agree with me.

Of course, we shouldn't ICE.

[Bug c++/53786] [C++11] alias template - error on valid code

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53786

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |DUPLICATE

--- Comment #8 from Jason Merrill <jason at gcc dot gnu.org> 2013-04-05 16:29:42 UTC ---
Same issue, similar testcase to 51239.

*** This bug has been marked as a duplicate of bug 51239 ***