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From: "leonid at volnitsky dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/51989] New: std::deque::iterator recognised as container
Date: Wed, 25 Jan 2012 06:59:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D51989

             Bug #: 51989
           Summary: std::deque::iterator recognised as container
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: leonid@volnitsky.com


Created attachment 26450
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=3D26450
deque-bug.cc

I need is_container<T> template which would recognize if T is a container.=
=20
Code below works as expected.  With exception for std::deque::iterator -  g=
cc
can not compile code below:

------------------------------------------------------------------
#include <iostream>
#include <type_traits>
#include <vector>
#include <list>
#include <set>
#include <deque>

    template <typename T>
struct is_container {
    template <typename U>
    static char test(
        U* u,
        typename U::const_iterator b =3D ((U*)0)->begin(),
        typename U::const_iterator e =3D ((U*)0)->end()
    );
    template <typename U> static long test(...);

    enum { value =3D sizeof test<T>(0) =3D=3D 1 };
};

int main() {
    std::cout <<  "void\t"            << is_container< void=20=20=20=20=20=
=20=20=20=20=20=20=20
>::value << '\n';
    std::cout <<  "int\t"            << is_container< int              >::v=
alue
<< '\n';
    std::cout <<  "int*\t"            << is_container< int*=20=20=20=20=20=
=20=20=20=20=20=20=20
>::value << '\n';
    std::cout <<  "vector<int>\t"        << is_container< std::vector<int>
>::value << '\n';
    std::cout <<  "deque<int>\t"        << is_container< std::deque<int>=20
>::value << '\n';
    std::cout <<  "set<int>::iterator\t"    << is_container<
std::set<int>::iterator >::value << '\n';
    std::cout <<  "vector<int>::iterator\t"    << is_container<
std::vector<int>::iterator >::value << '\n';

    // gcc error
    std::cout <<  "deque<int>::iterator\t"    << is_container<
std::deque<int>::iterator >::value << '\n';
}
-----------------------------------------------------------------------

Compiling it with GCC (4.7.0-alpha20111203):

gcc -std=3Dgnu++0x -Wall deque-bug.cc   -o deque-bug

Produce following error:

deque-bug.cc: In instantiation of =E2=80=98struct
is_container<std::_Deque_iterator<int, int&, int*> >=E2=80=99:
deque-bug.cc:31:84:   required from here
deque-bug.cc:18:7: error: =E2=80=98struct std::_Deque_iterator<int, int&, i=
nt*>=E2=80=99 has no
member named =E2=80=98begin=E2=80=99
deque-bug.cc:18:7: error: =E2=80=98struct std::_Deque_iterator<int, int&, i=
nt*>=E2=80=99 has no
member named =E2=80=98end=E2=80=99

Attached are source and -save-temps