[libc++][modules] Add a header to forward-declare std::get #108285
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This is necessary because e.g. ranges::elements_view uses std::get but it needs to have in scope the declaration of all the versions of std::get that exist in the library. This need is what had originally led to elements_view.h gaining an include of __fwd/complex.h, but in reality it is a more general issue that requires a canonical declration point for all the std::get variations.
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@llvm/pr-subscribers-libcxx Author: Louis Dionne (ldionne) ChangesThis is necessary because e.g. ranges::elements_view uses std::get but it needs to have in scope the declaration of all the versions of std::get that exist in the library. This need is what had originally led to elements_view.h gaining an include of __fwd/complex.h, but in reality it is a more general issue that requires a canonical declration point for all the std::get variations. Full diff: https://github.com/llvm/llvm-project/pull/108285.diff 6 Files Affected:
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index ffff8114e5870d..23d9aa0adddce8 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -424,6 +424,7 @@ set(files
__fwd/format.h
__fwd/fstream.h
__fwd/functional.h
+ __fwd/get.h
__fwd/ios.h
__fwd/istream.h
__fwd/mdspan.h
@@ -440,6 +441,7 @@ set(files
__fwd/string_view.h
__fwd/subrange.h
__fwd/tuple.h
+ __fwd/variant.h
__fwd/vector.h
__hash_table
__ios/fpos.h
diff --git a/libcxx/include/__fwd/get.h b/libcxx/include/__fwd/get.h
new file mode 100644
index 00000000000000..6121ed0efd2bab
--- /dev/null
+++ b/libcxx/include/__fwd/get.h
@@ -0,0 +1,24 @@
+//===---------------------------------------------------------------------===//
+//
+// 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
+//
+//===---------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FWD_GET_H
+#define _LIBCPP___FWD_GET_H
+
+#include <__config>
+#include <__fwd/array.h>
+#include <__fwd/complex.h>
+#include <__fwd/pair.h>
+#include <__fwd/subrange.h>
+#include <__fwd/tuple.h>
+#include <__fwd/variant.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+#endif // _LIBCPP___FWD_GET_H
diff --git a/libcxx/include/__fwd/variant.h b/libcxx/include/__fwd/variant.h
new file mode 100644
index 00000000000000..a6b713208d9947
--- /dev/null
+++ b/libcxx/include/__fwd/variant.h
@@ -0,0 +1,73 @@
+//===---------------------------------------------------------------------===//
+//
+// 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
+//
+//===---------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___FWD_VARIANT_H
+#define _LIBCPP___FWD_VARIANT_H
+
+#include <__config>
+#include <__cstddef/size_t.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class... _Types>
+class _LIBCPP_TEMPLATE_VIS variant;
+
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS variant_size;
+
+template <class _Tp>
+inline constexpr size_t variant_size_v = variant_size<_Tp>::value;
+
+template <size_t _Ip, class _Tp>
+struct _LIBCPP_TEMPLATE_VIS variant_alternative;
+
+template <size_t _Ip, class _Tp>
+using variant_alternative_t = typename variant_alternative<_Ip, _Tp>::type;
+
+inline constexpr size_t variant_npos = static_cast<size_t>(-1);
+
+template <size_t _Ip, class... _Types>
+_LIBCPP_HIDE_FROM_ABI
+_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS constexpr variant_alternative_t<_Ip, variant<_Types...>>&
+get(variant<_Types...>&);
+
+template <size_t _Ip, class... _Types>
+_LIBCPP_HIDE_FROM_ABI
+_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS constexpr variant_alternative_t<_Ip, variant<_Types...>>&&
+get(variant<_Types...>&&);
+
+template <size_t _Ip, class... _Types>
+_LIBCPP_HIDE_FROM_ABI
+_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS constexpr const variant_alternative_t<_Ip, variant<_Types...>>&
+get(const variant<_Types...>&);
+
+template <size_t _Ip, class... _Types>
+_LIBCPP_HIDE_FROM_ABI
+_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS constexpr const variant_alternative_t<_Ip, variant<_Types...>>&&
+get(const variant<_Types...>&&);
+
+template <class _Tp, class... _Types>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS constexpr _Tp& get(variant<_Types...>&);
+
+template <class _Tp, class... _Types>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS constexpr _Tp&& get(variant<_Types...>&&);
+
+template <class _Tp, class... _Types>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS constexpr const _Tp& get(const variant<_Types...>&);
+
+template <class _Tp, class... _Types>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS constexpr const _Tp&&
+get(const variant<_Types...>&&);
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FWD_VARIANT_H
diff --git a/libcxx/include/__ranges/elements_view.h b/libcxx/include/__ranges/elements_view.h
index f159f53dc0a832..989d36fbcaaae5 100644
--- a/libcxx/include/__ranges/elements_view.h
+++ b/libcxx/include/__ranges/elements_view.h
@@ -16,7 +16,7 @@
#include <__concepts/derived_from.h>
#include <__concepts/equality_comparable.h>
#include <__config>
-#include <__fwd/complex.h>
+#include <__fwd/get.h>
#include <__iterator/concepts.h>
#include <__iterator/iterator_traits.h>
#include <__ranges/access.h>
diff --git a/libcxx/include/module.modulemap b/libcxx/include/module.modulemap
index add8726dead428..4e179d871e24c6 100644
--- a/libcxx/include/module.modulemap
+++ b/libcxx/include/module.modulemap
@@ -1813,6 +1813,7 @@ module std_private_tuple_tuple_like_no_subrange [system] {
module std_private_tuple_sfinae_helpers [system] { header "__tuple/sfinae_helpers.h" }
module std_private_tuple_tuple_element [system] { header "__tuple/tuple_element.h" }
module std_private_tuple_tuple_fwd [system] { header "__fwd/tuple.h" }
+module std_private_get_fwd [system] { header "__fwd/get.h" }
module std_private_tuple_tuple_indices [system] { header "__tuple/tuple_indices.h" }
module std_private_tuple_tuple_like [system] {
header "__tuple/tuple_like.h"
@@ -2103,5 +2104,6 @@ module std_private_utility_to_underlying [system] { header "__utility/
module std_private_utility_unreachable [system] { header "__utility/unreachable.h" }
module std_private_variant_monostate [system] { header "__variant/monostate.h" }
+module std_private_variant_fwd [system] { header "__fwd/variant.h" }
module std_private_vector_fwd [system] { header "__fwd/vector.h" }
diff --git a/libcxx/include/variant b/libcxx/include/variant
index 1cac603c27c243..2fa5623d4f118a 100644
--- a/libcxx/include/variant
+++ b/libcxx/include/variant
@@ -221,6 +221,7 @@ namespace std {
#include <__functional/invoke.h>
#include <__functional/operations.h>
#include <__functional/unary_function.h>
+#include <__fwd/variant.h>
#include <__memory/addressof.h>
#include <__memory/construct_at.h>
#include <__tuple/find_index.h>
@@ -307,15 +308,7 @@ __throw_bad_variant_access() {
# endif
}
-template <class... _Types>
-class _LIBCPP_TEMPLATE_VIS variant;
-
-template <class _Tp>
-struct _LIBCPP_TEMPLATE_VIS variant_size;
-
-template <class _Tp>
-inline constexpr size_t variant_size_v = variant_size<_Tp>::value;
-
+// variant_size
template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS variant_size<const _Tp> : variant_size<_Tp> {};
@@ -328,12 +321,7 @@ struct _LIBCPP_TEMPLATE_VIS variant_size<const volatile _Tp> : variant_size<_Tp>
template <class... _Types>
struct _LIBCPP_TEMPLATE_VIS variant_size<variant<_Types...>> : integral_constant<size_t, sizeof...(_Types)> {};
-template <size_t _Ip, class _Tp>
-struct _LIBCPP_TEMPLATE_VIS variant_alternative;
-
-template <size_t _Ip, class _Tp>
-using variant_alternative_t = typename variant_alternative<_Ip, _Tp>::type;
-
+// variant_alternative
template <size_t _Ip, class _Tp>
struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, const _Tp> : add_const<variant_alternative_t<_Ip, _Tp>> {};
@@ -349,8 +337,6 @@ struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, variant<_Types...>> {
using type = __type_pack_element<_Ip, _Types...>;
};
-inline constexpr size_t variant_npos = static_cast<size_t>(-1);
-
template <size_t _NumAlternatives>
_LIBCPP_HIDE_FROM_ABI constexpr auto __choose_index_type() {
# ifdef _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION
@@ -369,9 +355,6 @@ using __variant_index_t = decltype(std::__choose_index_type<_NumAlts>());
template <class _IndexType>
constexpr _IndexType __variant_npos = static_cast<_IndexType>(-1);
-template <class... _Types>
-class _LIBCPP_TEMPLATE_VIS variant;
-
template <class... _Types>
_LIBCPP_HIDE_FROM_ABI constexpr variant<_Types...>& __as_variant(variant<_Types...>& __vs) noexcept {
return __vs;
|
philnik777
requested changes
Sep 12, 2024
This is already caught by our existing tests. If you remove |
This also adds forward declarations for |
|
As we discussed during our 1:1, this issue is indeed caught by the existing tests when we modularized. The reason why things work right now is that |
philnik777
approved these changes
Sep 12, 2024
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/52/builds/2234 Here is the relevant piece of the build log for the reference |
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This is necessary because e.g. ranges::elements_view uses std::get but it needs to have in scope the declaration of all the versions of std::get that exist in the library. This need is what had originally led to elements_view.h gaining an include of __fwd/complex.h, but in reality it is a more general issue that requires a canonical declration point for all the std::get variations.