[libcxx] Delay evaluation of __make_tuple_types to prevent blowing the max template instantiation depth. Fixes Bug #18345

Summary:
http://llvm.org/bugs/show_bug.cgi?id=18345

Tuple's constructor and assignment operators for "tuple-like" types evaluates __make_tuple_types unnecessarily. In the case of a large array this can blow the template instantiation depth.

Ex:
```
#include <array>
#include <tuple>
#include <memory>
 
typedef std::array<int, 1256> array_t;
typedef std::tuple<array_t> tuple_t;

int main() {
  array_t a;
  tuple_t t(a); // broken
  t = a; // broken

  // make_shared uses tuple behind the scenes. This bug breaks this code.
  std::make_shared<array_t>(a);
}
```

To prevent this from happening we delay the instantiation of `__make_tuple_types` until after we perform the length check. Currently `__make_tuple_types` is instantiated at the same time that the length check .


Test Plan: Two tests have been added. One for the "tuple-like" constructors and another for the "tuple-like" assignment operator. 

Reviewers: mclow.lists, EricWF

Reviewed By: EricWF

Subscribers: K-ballo, cfe-commits

Differential Revision: http://reviews.llvm.org/D4467

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@220769 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 51 insertions, 21 deletions

diff --git a/include/__tuple b/include/__tuple
index ee5b916fa..bffb95cb7 100644
--- a/include/__tuple
+++ b/include/__tuple
@@ -245,19 +245,30 @@ struct __make_tuple_types
 
 // __tuple_convertible
 
-template <bool, class _Tp, class _Up>
+template <class, class>
 struct __tuple_convertible_imp : public false_type {};
 
 template <class _Tp0, class ..._Tp, class _Up0, class ..._Up>
-struct __tuple_convertible_imp<true, __tuple_types<_Tp0, _Tp...>, __tuple_types<_Up0, _Up...> >
+struct __tuple_convertible_imp<__tuple_types<_Tp0, _Tp...>, __tuple_types<_Up0, _Up...> >
     : public integral_constant<bool,
                                is_convertible<_Tp0, _Up0>::value &&
-                               __tuple_convertible_imp<true, __tuple_types<_Tp...>, __tuple_types<_Up...> >::value> {};
+                               __tuple_convertible_imp<__tuple_types<_Tp...>, __tuple_types<_Up...> >::value> {};
 
 template <>
-struct __tuple_convertible_imp<true, __tuple_types<>, __tuple_types<> >
+struct __tuple_convertible_imp<__tuple_types<>, __tuple_types<> >
     : public true_type {};
 
+template <bool, class, class>
+struct __tuple_convertible_apply : public false_type {};
+
+template <class _Tp, class _Up>
+struct __tuple_convertible_apply<true, _Tp, _Up>
+  : public __tuple_convertible_imp<
+      typename __make_tuple_types<_Tp>::type
+    , typename __make_tuple_types<_Up>::type
+    >
+{};
+
 template <class _Tp, class _Up, bool = __tuple_like<typename remove_reference<_Tp>::type>::value,
                                 bool = __tuple_like<_Up>::value>
 struct __tuple_convertible
@@ -265,26 +276,36 @@ struct __tuple_convertible
 
 template <class _Tp, class _Up>
 struct __tuple_convertible<_Tp, _Up, true, true>
-    : public __tuple_convertible_imp<tuple_size<typename remove_reference<_Tp>::type>::value ==
-                                     tuple_size<_Up>::value,
-             typename __make_tuple_types<_Tp>::type, typename __make_tuple_types<_Up>::type>
+    : public __tuple_convertible_apply<tuple_size<typename remove_reference<_Tp>::type>::value ==
+                                     tuple_size<_Up>::value, _Tp, _Up>
 {};
 
 // __tuple_constructible
 
-template <bool, class _Tp, class _Up>
+template <class, class>
 struct __tuple_constructible_imp : public false_type {};
 
 template <class _Tp0, class ..._Tp, class _Up0, class ..._Up>
-struct __tuple_constructible_imp<true, __tuple_types<_Tp0, _Tp...>, __tuple_types<_Up0, _Up...> >
+struct __tuple_constructible_imp<__tuple_types<_Tp0, _Tp...>, __tuple_types<_Up0, _Up...> >
     : public integral_constant<bool,
                                is_constructible<_Up0, _Tp0>::value &&
-                               __tuple_constructible_imp<true, __tuple_types<_Tp...>, __tuple_types<_Up...> >::value> {};
+                               __tuple_constructible_imp<__tuple_types<_Tp...>, __tuple_types<_Up...> >::value> {};
 
 template <>
-struct __tuple_constructible_imp<true, __tuple_types<>, __tuple_types<> >
+struct __tuple_constructible_imp<__tuple_types<>, __tuple_types<> >
     : public true_type {};
 
+template <bool _SameSize, class, class>
+struct __tuple_constructible_apply : public false_type {};
+
+template <class _Tp, class _Up>
+struct __tuple_constructible_apply<true, _Tp, _Up>
+  : public __tuple_constructible_imp<
+      typename __make_tuple_types<_Tp>::type
+    , typename __make_tuple_types<_Up>::type
+    >
+{};
+
 template <class _Tp, class _Up, bool = __tuple_like<typename remove_reference<_Tp>::type>::value,
                                 bool = __tuple_like<_Up>::value>
 struct __tuple_constructible
@@ -292,26 +313,36 @@ struct __tuple_constructible
 
 template <class _Tp, class _Up>
 struct __tuple_constructible<_Tp, _Up, true, true>
-    : public __tuple_constructible_imp<tuple_size<typename remove_reference<_Tp>::type>::value ==
-                                     tuple_size<_Up>::value,
-             typename __make_tuple_types<_Tp>::type, typename __make_tuple_types<_Up>::type>
+    : public __tuple_constructible_apply<tuple_size<typename remove_reference<_Tp>::type>::value ==
+                                     tuple_size<_Up>::value, _Tp, _Up>
 {};
 
 // __tuple_assignable
 
-template <bool, class _Tp, class _Up>
+template <class, class>
 struct __tuple_assignable_imp : public false_type {};
 
 template <class _Tp0, class ..._Tp, class _Up0, class ..._Up>
-struct __tuple_assignable_imp<true, __tuple_types<_Tp0, _Tp...>, __tuple_types<_Up0, _Up...> >
+struct __tuple_assignable_imp<__tuple_types<_Tp0, _Tp...>, __tuple_types<_Up0, _Up...> >
     : public integral_constant<bool,
                                is_assignable<_Up0&, _Tp0>::value &&
-                               __tuple_assignable_imp<true, __tuple_types<_Tp...>, __tuple_types<_Up...> >::value> {};
+                               __tuple_assignable_imp<__tuple_types<_Tp...>, __tuple_types<_Up...> >::value> {};
 
 template <>
-struct __tuple_assignable_imp<true, __tuple_types<>, __tuple_types<> >
+struct __tuple_assignable_imp<__tuple_types<>, __tuple_types<> >
     : public true_type {};
 
+template <bool, class, class>
+struct __tuple_assignable_apply : public false_type {};
+
+template <class _Tp, class _Up>
+struct __tuple_assignable_apply<true, _Tp, _Up>
+  : __tuple_assignable_imp<
+      typename __make_tuple_types<_Tp>::type
+    , typename __make_tuple_types<_Up>::type
+    >
+{};
+
 template <class _Tp, class _Up, bool = __tuple_like<typename remove_reference<_Tp>::type>::value,
                                 bool = __tuple_like<_Up>::value>
 struct __tuple_assignable
@@ -319,9 +350,8 @@ struct __tuple_assignable
 
 template <class _Tp, class _Up>
 struct __tuple_assignable<_Tp, _Up, true, true>
-    : public __tuple_assignable_imp<tuple_size<typename remove_reference<_Tp>::type>::value ==
-                                    tuple_size<_Up>::value,
-             typename __make_tuple_types<_Tp>::type, typename __make_tuple_types<_Up>::type>
+    : public __tuple_assignable_apply<tuple_size<typename remove_reference<_Tp>::type>::value ==
+                                    tuple_size<_Up>::value, _Tp, _Up>
 {};
 
 _LIBCPP_END_NAMESPACE_STD