[libcxx-commits] [PATCH] D101661: [libc++] Fix template instantiation depth issues with std::tuple

[Louis Dionne via Phabricator via libcxx-commits]

ldionne updated this revision to Diff 342416.
ldionne added a comment.

Greatly simplify the implementation of _And, and hopefully fix C++03


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D101661/new/

https://reviews.llvm.org/D101661

Files:
  libcxx/include/type_traits
  libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/recursion_depth.pass.cpp


Index: libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/recursion_depth.pass.cpp
===================================================================
--- /dev/null
+++ libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/recursion_depth.pass.cpp
@@ -0,0 +1,35 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11
+
+// Make sure that we don't blow up the template instantiation recursion depth
+// for tuples of size <= 1024.
+
+#include <tuple>
+#include <cassert>
+#include <utility>
+
+template <size_t... I>
+constexpr void CreateTuple(std::index_sequence<I...>) {
+  std::tuple<decltype(I)...> tuple(I...);
+  assert(std::get<0>(tuple) == 0);
+  assert(std::get<sizeof...(I)-1>(tuple) == sizeof...(I)-1);
+}
+
+constexpr bool test() {
+  CreateTuple(std::make_index_sequence<1024>{});
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test(), "");
+  return 0;
+}
Index: libcxx/include/type_traits
===================================================================
--- libcxx/include/type_traits
+++ libcxx/include/type_traits
@@ -476,8 +476,6 @@
   using _EnableIfImpl _LIBCPP_NODEBUG_TYPE = _Tp;
   template <class _Result, class _First, class ..._Rest>
   using _OrImpl _LIBCPP_NODEBUG_TYPE = typename _MetaBase<_First::value != true && sizeof...(_Rest) != 0>::template _OrImpl<_First, _Rest...>;
-  template <class _Result, class _First, class ..._Rest>
-  using _AndImpl _LIBCPP_NODEBUG_TYPE = typename _MetaBase<_First::value == true && sizeof...(_Rest) != 0>::template _AndImpl<_First, _Rest...>;
 };
 
 template <>
@@ -488,8 +486,6 @@
   using _SelectApplyImpl _LIBCPP_NODEBUG_TYPE = _SecondFn<_Args...>;
   template <class _Result, class ...>
   using _OrImpl _LIBCPP_NODEBUG_TYPE = _Result;
-  template <class _Result, class ...>
-  using _AndImpl _LIBCPP_NODEBUG_TYPE = _Result;
 };
 template <bool _Cond, class _Ret = void>
 using _EnableIf _LIBCPP_NODEBUG_TYPE = typename _MetaBase<_Cond>::template _EnableIfImpl<_Ret>;
@@ -497,8 +493,6 @@
 using _If _LIBCPP_NODEBUG_TYPE = typename _MetaBase<_Cond>::template _SelectImpl<_IfRes, _ElseRes>;
 template <class ..._Rest>
 using _Or _LIBCPP_NODEBUG_TYPE = typename _MetaBase< sizeof...(_Rest) != 0 >::template _OrImpl<false_type, _Rest...>;
-template <class ..._Rest>
-using _And _LIBCPP_NODEBUG_TYPE = typename _MetaBase< sizeof...(_Rest) != 0 >::template _AndImpl<true_type, _Rest...>;
 template <class _Pred>
 struct _Not : _BoolConstant<!_Pred::value> {};
 template <class ..._Args>
@@ -506,6 +500,14 @@
 template <class ..._Args>
 using _SecondType _LIBCPP_NODEBUG_TYPE = typename _MetaBase<(sizeof...(_Args) >= 2)>::template _SecondImpl<_Args...>;
 
+template <class ...> using __expand_to_true = true_type;
+template <class ..._Pred>
+__expand_to_true<_EnableIf<_Pred::value>...> __and_helper(int);
+template <class ...>
+false_type __and_helper(...);
+template <class ..._Pred>
+using _And _LIBCPP_NODEBUG_TYPE = decltype(__and_helper<_Pred...>(0));
+
 template <template <class...> class _Func, class ..._Args>
 struct _Lazy : _Func<_Args...> {};
 


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