http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48451
Summary: [C++0x][SFINAE] Failures with n-ary initialization
expressions (with template default argument)
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: daniel.krueg...@googlemail.com
CC: ja...@redhat.com
Some n-ary initialization expressions in a SFINAE context used in function
template default arguments either give a hard error:
a) any T => abstract class
or give the wrong result:
b) when the destination is a class type constructed from valid arguments
#include <utility> // for declval
template<class T, class... Args,
class = decltype(T(std::declval<Args>()...))
>
char f(int);
template<class, class...>
char (&f(...))[2];
struct A { virtual ~A() = 0; };
struct From2Ints { From2Ints(int, int); };
static_assert(sizeof(f<A, int, int>(0)) != 1, "Error"); // a
static_assert(sizeof(f<From2Ints, int, int>(0)) == 1, "Error"); // b
a) "error: cannot allocate an object of abstract type 'A' because the
following virtual functions are pure within 'A': virtual A::~A()"
b) Assertion triggers!
