[Bug c++/26205] New: pointer to member template parameter can't be null

[jeffp at doomsday dot org]

struct Simple
{
    int a;
};

template <typename T, int T::*U> struct Test
{
    void Foo(T *obj, int v)
    {
        if (U != 0)
            obj->*U = v;
    }
};

int main(int argc, const char **argv)
{
    Test<Simple, &Simple::a> t1;    // ok
    Test<Simple, 0> t2;             // error, but should not be (works in MSVC
7/8)

    Simple s;
    t1.Foo(&s, 5);
}


Note: it also won't let you specify a default parameter of 0 for the template
parameter:

template <typename T, int T::*U = 0> struct Test   // won't do this either

MSVC 7/8 handle the first case, but also can't handle the default parameter
(they crash with an internal compiler error).  MSVC 7/8 also won't handle
specialization of the Foo function for the 0 case, though the resultant code
generated is the same since the branch is optimized out.  I only mention this
to give you some other nuances to check for once the base bug is fixed.


-- 
           Summary: pointer to member template parameter can't be null
           Product: gcc
           Version: 3.4.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jeffp at doomsday dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26205