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* [Bug c++/51222] New: [C++11][SFINAE] Unevaluated combined delete new expression completely broken
@ 2011-11-19 18:39 daniel.kruegler at googlemail dot com
  2011-11-20  0:27 ` [Bug c++/51222] " paolo.carlini at oracle dot com
                   ` (6 more replies)
  0 siblings, 7 replies; 8+ messages in thread
From: daniel.kruegler at googlemail dot com @ 2011-11-19 18:39 UTC (permalink / raw)
  To: gcc-bugs

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51222

             Bug #: 51222
           Summary: [C++11][SFINAE] Unevaluated combined delete new
                    expression completely broken
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: daniel.kruegler@googlemail.com
                CC: jason@gcc.gnu.org


The following problem became obvious to me when I recently tried to provide a
both simpler and more general library emulation of is_constructible.

gcc 4.7 20111112 (experimental) in C++11 mode rejects the following code:

//---
template<class T>
struct add_rref {
  typedef T&& type;
};

template<>
struct add_rref<void> {
  typedef void type;
};

template<class T>
typename add_rref<T>::type declval();

template<class T, class U, class =
  decltype(::delete ::new T(declval<U>()))
>
auto f(int) -> char;

template<class, class>
auto f(...) -> char(&)[2];

template<class T, class =
  decltype(::delete ::new T())
>
auto g(int) -> char;

template<class>
auto g(...) -> char(&)[2];

struct C { };

struct A {
  virtual ~A() = 0;
};

struct D1 {
  D1() = delete;
};

struct D2 {
  ~D2() = delete;
};

static_assert(sizeof(g<void>(0)) == 2, "Ouch");
static_assert(sizeof(g<void()>(0)) == 2, "Ouch");
static_assert(sizeof(g<void() const>(0)) == 2, "Ouch");
static_assert(sizeof(g<A>(0)) == 2, "Ouch");
static_assert(sizeof(g<D1>(0)) == 2, "Ouch");
static_assert(sizeof(g<D2>(0)) == 2, "Ouch");
static_assert(sizeof(g<int&>(0)) == 2, "Ouch");
static_assert(sizeof(g<int&&>(0)) == 2, "Ouch");
static_assert(sizeof(g<void(&)()>(0)) == 2, "Ouch");
static_assert(sizeof(g<void(&&)()>(0)) == 2, "Ouch");
static_assert(sizeof(f<void, void>(0)) == 2, "Ouch");
static_assert(sizeof(f<void(), void()>(0)) == 2, "Ouch");
static_assert(sizeof(f<void() const, void() const>(0)) == 2, "Ouch");
static_assert(sizeof(f<int, void>(0)) == 2, "Ouch");
static_assert(sizeof(f<void, int>(0)) == 2, "Ouch");
static_assert(sizeof(f<C, void>(0)) == 2, "Ouch");
static_assert(sizeof(f<C, int>(0)) == 2, "Ouch");
static_assert(sizeof(f<int&, int&>(0)) == 2, "Ouch");
static_assert(sizeof(f<int&&, int&&>(0)) == 2, "Ouch");
static_assert(sizeof(f<void(&)(), void(&)()>(0)) == 2, "Ouch");
static_assert(sizeof(f<void(&&)(), void(&&)()>(0)) == 2, "Ouch");
//---

All static assertions fail, but they shouldn't. This is very unfortunate,
because above test expressions are extremely useful for emulating an effective
variable definition including destruction semantics.

The test code should be accepted.


^ permalink raw reply	[flat|nested] 8+ messages in thread
end of thread, other threads:[~2012-08-31 15:03 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2011-11-19 18:39 [Bug c++/51222] New: [C++11][SFINAE] Unevaluated combined delete new expression completely broken daniel.kruegler at googlemail dot com
2011-11-20  0:27 ` [Bug c++/51222] " paolo.carlini at oracle dot com
2011-11-21  8:08 ` daniel.kruegler at googlemail dot com
2011-11-22 22:34 ` paolo.carlini at oracle dot com
2012-05-24 12:32 ` paolo.carlini at oracle dot com
2012-06-11 16:02 ` paolo.carlini at oracle dot com
2012-08-31  2:50 ` jason at gcc dot gnu.org
2012-08-31 15:03 ` jason at gcc dot gnu.org

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