EricWF created this revision.
EricWF added a reviewer: mclow.lists.
EricWF added a subscriber: cfe-commits.
This patch implements the solution for LWG Issue #2367. See
http://cplusplus.github.io/LWG/lwg-active.html#2367
http://reviews.llvm.org/D13750
Files:
include/__config
include/utility
test/std/utilities/utility/pairs/pairs.pair/default.pass.cpp
Index: test/std/utilities/utility/pairs/pairs.pair/default.pass.cpp
===================================================================
--- test/std/utilities/utility/pairs/pairs.pair/default.pass.cpp
+++ test/std/utilities/utility/pairs/pairs.pair/default.pass.cpp
@@ -14,23 +14,145 @@
// constexpr pair();
#include <utility>
+#include <type_traits>
#include <cassert>
+#include "test_macros.h"
+
+
+#if TEST_STD_VER > 11
+#define CONSTEXPR_CXX14 constexpr
+ // Expands to 'constexpr' in C++14 and greater and '' otherwise.
+#define STATIC_ASSERT_CXX14(Pred) static_assert(Pred, "")
+ // Assert the specified expression 'Pred' using a static_assert in C++14 and
+ // greater and using assert(...) otherwise.
+#else
+#define CONSTEXPR_CXX14
+#define STATIC_ASSERT_CXX14(Pred) assert(Pred)
+#endif
+
+
+#if TEST_STD_VER >= 11
+#define ASSERT_CXX03_ONLY(Pred) ((void)0)
+ // Assert the specified expression 'Pred' only in C++98 and C++03. In C++11
+ // and greater 'ASSERT_CXX03_ONLY' expands to a nop expression.
+#else
+#define ASSERT_CXX03_ONLY(Pred) assert(Pred)
+#endif
+
+
+#if TEST_STD_VER >= 11
+struct DeletedDefault {
+ // A class with a deleted default constructor. Used to test the SFINAE
+ // on std::pairs default constructor.
+ constexpr explicit DeletedDefault(int x) : value(x) {}
+ constexpr DeletedDefault() = delete;
+ int value;
+};
+#endif
+
+template <class T>
+struct IllFormedDefaultImp {
+ TEST_CONSTEXPR explicit IllFormedDefaultImp(int v) : value(v) {}
+ TEST_CONSTEXPR IllFormedDefaultImp() : value(T::DoesNotExistAndShouldNotCompile) {}
+ int value;
+};
+
+typedef IllFormedDefaultImp<int> IllFormedDefault;
+ // A class which provides a constexpr default constructor with a valid
+ // signature but an ill-formed body. The A compile error will be emitted if
+ // the default constructor is instantiated.
+
+
+// Test that the defaulted constructor does not participate in overload
+// resolution when either of the types in the pair is not default constructible.
+// See LWG issue #2367
+void test_deleted_default()
+{
+#if TEST_STD_VER >= 11
+ {
+ typedef std::pair<int, int> P;
+ static_assert(std::is_default_constructible<P>::value, "");
+ static_assert(std::is_constructible<P>::value, "");
+ }
+ {
+ typedef std::pair<DeletedDefault, int> P;
+ static_assert(!std::is_default_constructible<P>::value, "");
+ static_assert(!std::is_constructible<P>::value, "");
+ static_assert(std::is_constructible<P, DeletedDefault, int>::value, "");
+ CONSTEXPR_CXX14 P p(DeletedDefault(42), -5);
+ STATIC_ASSERT_CXX14(p.first.value == 42 && p.second == -5);
+ }
+ {
+ typedef std::pair<int, DeletedDefault> P;
+ static_assert(!std::is_default_constructible<P>::value, "");
+ static_assert(!std::is_constructible<P>::value, "");
+ static_assert(std::is_constructible<P, int, DeletedDefault>::value, "");
+ constexpr DeletedDefault dd(-5);
+ CONSTEXPR_CXX14 P p(42, dd);
+ STATIC_ASSERT_CXX14(p.first == 42 && p.second.value == -5);
+ }
+ {
+ typedef std::pair<DeletedDefault, DeletedDefault> P;
+ static_assert(!std::is_default_constructible<P>::value, "");
+ static_assert(std::is_constructible<P, DeletedDefault, DeletedDefault>::value, "");
+ CONSTEXPR_CXX14 P p(DeletedDefault(42), DeletedDefault(-5));
+ STATIC_ASSERT_CXX14(p.first.value == 42 && p.second.value == -5);
+ }
+#endif
+}
+
+
+// Check that the SFINAE on the default constructor is not evaluated when
+// it isn't needed. If the default constructor of 'IllFormedDefault' is evaluated
+// in C++11, even with is_default_constructible, then this test should fail to
+// compile. In C++14 and greater evaluate each test is evaluated as a constant
+// expression. In C++03 evaluating is_default_constructible will compile return the
+// wrong answer because libc++ does not back-port this behavior.
+// See LWG issue #2367
+void test_illformed_default()
+{
+ {
+ typedef std::pair<IllFormedDefault, int> P;
+ static_assert((std::is_constructible<P, IllFormedDefault, int>::value), "");
+ CONSTEXPR_CXX14 P p(IllFormedDefault(42), -5);
+ STATIC_ASSERT_CXX14(p.first.value == 42 && p.second == -5);
+ ASSERT_CXX03_ONLY(std::is_default_constructible<P>::value); // ASSERTS BUG IN C++03
+ }
+ {
+ typedef std::pair<int, IllFormedDefault> P;
+ static_assert((std::is_constructible<P, int, IllFormedDefault>::value), "");
+ CONSTEXPR_CXX14 IllFormedDefault dd(-5);
+ CONSTEXPR_CXX14 P p(42, dd);
+ STATIC_ASSERT_CXX14(p.first == 42 && p.second.value == -5);
+ ASSERT_CXX03_ONLY(std::is_default_constructible<P>::value); // ASSERTS BUG IN C++03
+ }
+ {
+ typedef std::pair<IllFormedDefault, IllFormedDefault> P;
+ static_assert((std::is_constructible<P, IllFormedDefault, IllFormedDefault>::value), "");
+ CONSTEXPR_CXX14 P p(IllFormedDefault(42), IllFormedDefault(-5));
+ STATIC_ASSERT_CXX14(p.first.value == 42 && p.second.value == -5);
+ ASSERT_CXX03_ONLY(std::is_default_constructible<P>::value); // ASSERTS BUG IN C++03
+ }
+}
+
+
int main()
{
{
typedef std::pair<float, short*> P;
P p;
assert(p.first == 0.0f);
assert(p.second == nullptr);
}
-
-#if _LIBCPP_STD_VER > 11
+#if TEST_STD_VER >= 11
{
typedef std::pair<float, short*> P;
constexpr P p;
static_assert(p.first == 0.0f, "");
static_assert(p.second == nullptr, "");
}
#endif
+ test_deleted_default();
+ test_illformed_default();
}
Index: include/utility
===================================================================
--- include/utility
+++ include/utility
@@ -261,6 +261,12 @@
// pair(const pair&) = default;
// pair(pair&&) = default;
+#ifndef _LIBCPP_HAS_NO_DEFAULT_FUNCTION_TEMPLATE_ARGS
+ template <bool _Dummy = true, class = typename enable_if<
+ __dependent_type<is_default_constructible<_T1>, _Dummy>::value &&
+ __dependent_type<is_default_constructible<_T2>, _Dummy>::value
+ >::type>
+#endif
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR pair() : first(), second() {}
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
Index: include/__config
===================================================================
--- include/__config
+++ include/__config
@@ -295,6 +295,10 @@
#define _LIBCPP_UNUSED __attribute__((__unused__))
+#if !(__has_feature(cxx_default_function_template_args))
+#define _LIBCPP_HAS_NO_DEFAULT_FUNCTION_TEMPLATE_ARGS
+#endif
+
#if !(__has_feature(cxx_defaulted_functions))
#define _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
#endif // !(__has_feature(cxx_defaulted_functions))
@@ -464,6 +468,7 @@
#define _LIBCPP_HAS_NO_ADVANCED_SFINAE
#define _LIBCPP_HAS_NO_DECLTYPE
+#define _LIBCPP_HAS_NO_DEFAULT_FUNCTION_TEMPLATE_ARGS
#define _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
#define _LIBCPP_HAS_NO_DELETED_FUNCTIONS
#define _LIBCPP_HAS_NO_NULLPTR
@@ -480,6 +485,7 @@
#define _LIBCPP_HAS_NO_ALWAYS_INLINE_VARIADICS
#if _GNUC_VER < 403
+#define _LIBCPP_HAS_NO_DEFAULT_FUNCTION_TEMPLATE_ARGS
#define _LIBCPP_HAS_NO_RVALUE_REFERENCES
#endif
@@ -562,6 +568,7 @@
#define _NOEXCEPT_(x)
#define _NOEXCEPT_OR_FALSE(x) false
+#define _LIBCPP_HAS_NO_DEFAULT_FUNCTION_TEMPLATE_ARGS
#define _LIBCPP_HAS_NO_TEMPLATE_ALIASES
#define _LIBCPP_HAS_NO_ADVANCED_SFINAE
#define _LIBCPP_HAS_NO_ALWAYS_INLINE_VARIADICS
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
