G++ fails when compiling the following program in
g++0x mode. It displays "spooky action at a distance"
when instantiating the member_ptr template, but I
expect the converting assignment operator from weak_ptr
to be selected instead.
-------------------------8<-----------------------
#include <type_traits>
class A {
};
class B : public A {
};
class C {
};
namespace gc {
template <typename T> class member_ptr;
}
template <typename T> class weak_ptr {
public:
weak_ptr() {}
template <typename X> weak_ptr(const weak_ptr<X>& v) {}
weak_ptr(const weak_ptr&) = default;
weak_ptr(const gc::member_ptr<T>& v);
~weak_ptr() = default;
// ------------------
weak_ptr& operator =(const weak_ptr&) = default;
template <typename X> weak_ptr& operator =(const weak_ptr<X>& v) {
return *this; }
};
namespace gc {
template <typename T> class member_ptr {
static_assert(std::is_base_of<C, T>::value,
"spooky action at a distance");
};
}
int main(int argc, char *argv[]) {
weak_ptr<A> ap1;
weak_ptr<B> bp1;
ap1 = bp1;
return 0;
}
-------------------------8<-----------------------
--
Summary: static_assert and SFINAE
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: piotr dot wyderski at gmail dot com
GCC host triplet: GCC-4.4.0 (20090309), Cygwin, Windows XP
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39413
