[Bug c++/56450] New: ICE with SFINAE when detecting non-static member variable

[Bug c++/56450] New: ICE with SFINAE when detecting non-static member variable

[d.frey at gmx dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56450

             Bug #: 56450
           Summary: ICE with SFINAE when detecting non-static member
                    variable
    Classification: Unclassified
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: d.frey@gmx.de


I tried to detect a non-static member variable of a given type and ran into an
ICE. Here's the code:

#include <type_traits>

template< typename, typename = void >
struct has_const_int_dummy
  : std::false_type
{};

template< typename T >
struct has_const_int_dummy< T, typename std::enable_if< std::is_same< decltype(
std::declval< T >().dummy ), const int >::value >::type >
  : std::true_type
{};

struct A0 { const int dummy; };
struct A1 {};
struct A2 { int dummy(); };
struct A3 { static const int dummy = 0; };

int main()
{
  static_assert( has_const_int_dummy< A0 >::value, "A0" );
  static_assert( !has_const_int_dummy< A1 >::value, "A1" );
  static_assert( !has_const_int_dummy< A2 >::value, "A2" );
  static_assert( !has_const_int_dummy< A3 >::value, "A3" ); // line 23
}

And here's the output from by shell:

frey@vbox$ clang++-3.2 -std=c++0x -O3 -Wall -Wextra t.cc -o t
frey@vbox$ g++-4.7 -std=c++0x -O3 -Wall -Wextra t.cc -o t
t.cc: In function ‘int main()’:
t.cc:23:44: internal compiler error: in finish_decltype_type, at
cp/semantics.c:5274
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-4.7/README.Bugs> for instructions.
Preprocessed source stored into /tmp/cclJIlZs.out file, please attach this to
your bugreport.
frey@vbox$ 

As you can see, the code is accepted by clang. Also, the same error as with
g++-4.7 is also produced by g++-4.6, just the line number in cp/semantics.c is
different.

[Bug c++/56450] ICE with SFINAE when detecting non-static member variable

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56450

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |jason at gcc dot gnu.org

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-02-26 07:36:33 UTC ---
I think the problem is that originally decltype is used on something that looks
like member access (COMPONENT_REF with IDENTIFIER_NODE as second operand), so
DECLTYPE_TYPE_ID_EXPR_OR_MEMBER_ACCESS_P is set on it, but then, as during
instantiation it is determined to be a static data member rather than member,
it is changed into COMPOUND_EXPR which first evaluates the former operand of
the COMPOUND_EXPR for side-effects and then has the VAR_DECL of the static data
member.  But for id_expression_or_member_access_p = true finish_decltype_type
doesn't handle COMPOUND_EXPR.

[Bug c++/56450] ICE with SFINAE when detecting non-static member variable

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56450

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |gessos.paul at yahoo dot gr

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> 2013-04-26 15:16:51 UTC ---
*** Bug 56949 has been marked as a duplicate of this bug. ***

[Bug c++/56450] ICE with SFINAE when detecting non-static member variable

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56450

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.9.0

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> 2013-04-28 22:58:13 UTC ---
Fixed for 4.9.0.

[Bug c++/56450] ICE with SFINAE when detecting non-static member variable

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56450

--- Comment #5 from Jason Merrill <jason at gcc dot gnu.org> 2013-04-29 14:03:25 UTC ---
Let's put this into 4.8.1 as well; it's completely safe.

[Bug c++/56450] ICE with SFINAE when detecting non-static member variable

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56450

--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> 2013-04-29 14:08:28 UTC ---
Ok.

[Bug c++/56450] ICE with SFINAE when detecting non-static member variable

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56450

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.9.0                       |4.8.1