[libc++] Granularize the <new> header (#119270)

This disentangles the code which previously had a mix of many #ifdefs, a
non-versioned namespace and a versioned namespace. It also makes it
clearer which parts of <new> are implemented on Windows by including <new.h>.

Author: ldionne

libcxx/include/CMakeLists.txt

@@ -581,6 +581,16 @@ set(files
   __mutex/once_flag.h
   __mutex/tag_types.h
   __mutex/unique_lock.h
+  __new/align_val_t.h
+  __new/allocate.h
+  __new/destroying_delete_t.h
+  __new/exceptions.h
+  __new/global_new_delete.h
+  __new/interference_size.h
+  __new/launder.h
+  __new/new_handler.h
+  __new/nothrow_t.h
+  __new/placement_new_delete.h
   __node_handle
   __numeric/accumulate.h
   __numeric/adjacent_difference.h

libcxx/include/__hash_table

@@ -26,6 +26,7 @@
 #include <__memory/pointer_traits.h>
 #include <__memory/swap_allocator.h>
 #include <__memory/unique_ptr.h>
+#include <__new/launder.h>
 #include <__type_traits/can_extract_key.h>
 #include <__type_traits/conditional.h>
 #include <__type_traits/enable_if.h>
@@ -46,7 +47,6 @@
 #include <__utility/swap.h>
 #include <cstring>
 #include <limits>
-#include <new> // __launder
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header

libcxx/include/__memory/allocator.h

@@ -12,6 +12,7 @@
 
 #include <__config>
 #include <__cstddef/ptrdiff_t.h>
+#include <__cstddef/size_t.h>
 #include <__memory/addressof.h>
 #include <__memory/allocate_at_least.h>
 #include <__memory/allocator_traits.h>

libcxx/include/__memory/builtin_new_allocator.h

@@ -10,6 +10,7 @@
 #define _LIBCPP___MEMORY_BUILTIN_NEW_ALLOCATOR_H
 
 #include <__config>
+#include <__cstddef/size_t.h>
 #include <__memory/unique_ptr.h>
 #include <new>
 

libcxx/include/__memory/construct_at.h

@@ -14,12 +14,12 @@
 #include <__config>
 #include <__iterator/access.h>
 #include <__memory/addressof.h>
+#include <__new/placement_new_delete.h>
 #include <__type_traits/enable_if.h>
 #include <__type_traits/is_array.h>
 #include <__utility/declval.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
-#include <new>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header

libcxx/include/__memory/shared_ptr.h

@@ -43,6 +43,7 @@
 #include <__type_traits/is_bounded_array.h>
 #include <__type_traits/is_constructible.h>
 #include <__type_traits/is_convertible.h>
+#include <__type_traits/is_function.h>
 #include <__type_traits/is_reference.h>
 #include <__type_traits/is_same.h>
 #include <__type_traits/is_unbounded_array.h>

libcxx/include/__memory/uninitialized_algorithms.h

@@ -15,6 +15,7 @@
 #include <__algorithm/unwrap_iter.h>
 #include <__algorithm/unwrap_range.h>
 #include <__config>
+#include <__cstddef/size_t.h>
 #include <__iterator/iterator_traits.h>
 #include <__iterator/reverse_iterator.h>
 #include <__memory/addressof.h>

libcxx/include/__new/align_val_t.h

@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___NEW_ALIGN_VAL_T_H
+#define _LIBCPP___NEW_ALIGN_VAL_T_H
+
+#include <__config>
+#include <__cstddef/size_t.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+// purposefully not using versioning namespace
+namespace std {
+#if _LIBCPP_HAS_LIBRARY_ALIGNED_ALLOCATION && !defined(_LIBCPP_ABI_VCRUNTIME)
+#  ifndef _LIBCPP_CXX03_LANG
+enum class align_val_t : size_t {};
+#  else
+enum align_val_t { __zero = 0, __max = (size_t)-1 };
+#  endif
+#endif
+} // namespace std
+
+#endif // _LIBCPP___NEW_ALIGN_VAL_T_H

libcxx/include/__new/allocate.h

@@ -0,0 +1,101 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___NEW_ALLOCATE_H
+#define _LIBCPP___NEW_ALLOCATE_H
+
+#include <__config>
+#include <__cstddef/max_align_t.h>
+#include <__cstddef/size_t.h>
+#include <__new/align_val_t.h>
+#include <__new/global_new_delete.h> // for _LIBCPP_HAS_SIZED_DEALLOCATION
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_CONSTEXPR inline _LIBCPP_HIDE_FROM_ABI bool __is_overaligned_for_new(size_t __align) _NOEXCEPT {
+#ifdef __STDCPP_DEFAULT_NEW_ALIGNMENT__
+  return __align > __STDCPP_DEFAULT_NEW_ALIGNMENT__;
+#else
+  return __align > _LIBCPP_ALIGNOF(max_align_t);
+#endif
+}
+
+template <class... _Args>
+_LIBCPP_HIDE_FROM_ABI void* __libcpp_operator_new(_Args... __args) {
+#if __has_builtin(__builtin_operator_new) && __has_builtin(__builtin_operator_delete)
+  return __builtin_operator_new(__args...);
+#else
+  return ::operator new(__args...);
+#endif
+}
+
+template <class... _Args>
+_LIBCPP_HIDE_FROM_ABI void __libcpp_operator_delete(_Args... __args) _NOEXCEPT {
+#if __has_builtin(__builtin_operator_new) && __has_builtin(__builtin_operator_delete)
+  __builtin_operator_delete(__args...);
+#else
+  ::operator delete(__args...);
+#endif
+}
+
+inline _LIBCPP_HIDE_FROM_ABI void* __libcpp_allocate(size_t __size, size_t __align) {
+#if _LIBCPP_HAS_ALIGNED_ALLOCATION
+  if (__is_overaligned_for_new(__align)) {
+    const align_val_t __align_val = static_cast<align_val_t>(__align);
+    return __libcpp_operator_new(__size, __align_val);
+  }
+#endif
+
+  (void)__align;
+  return __libcpp_operator_new(__size);
+}
+
+template <class... _Args>
+_LIBCPP_HIDE_FROM_ABI void __do_deallocate_handle_size(void* __ptr, size_t __size, _Args... __args) _NOEXCEPT {
+#if !_LIBCPP_HAS_SIZED_DEALLOCATION
+  (void)__size;
+  return std::__libcpp_operator_delete(__ptr, __args...);
+#else
+  return std::__libcpp_operator_delete(__ptr, __size, __args...);
+#endif
+}
+
+inline _LIBCPP_HIDE_FROM_ABI void __libcpp_deallocate(void* __ptr, size_t __size, size_t __align) _NOEXCEPT {
+#if !_LIBCPP_HAS_ALIGNED_ALLOCATION
+  (void)__align;
+  return __do_deallocate_handle_size(__ptr, __size);
+#else
+  if (__is_overaligned_for_new(__align)) {
+    const align_val_t __align_val = static_cast<align_val_t>(__align);
+    return __do_deallocate_handle_size(__ptr, __size, __align_val);
+  } else {
+    return __do_deallocate_handle_size(__ptr, __size);
+  }
+#endif
+}
+
+inline _LIBCPP_HIDE_FROM_ABI void __libcpp_deallocate_unsized(void* __ptr, size_t __align) _NOEXCEPT {
+#if !_LIBCPP_HAS_ALIGNED_ALLOCATION
+  (void)__align;
+  return __libcpp_operator_delete(__ptr);
+#else
+  if (__is_overaligned_for_new(__align)) {
+    const align_val_t __align_val = static_cast<align_val_t>(__align);
+    return __libcpp_operator_delete(__ptr, __align_val);
+  } else {
+    return __libcpp_operator_delete(__ptr);
+  }
+#endif
+}
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___NEW_ALLOCATE_H

libcxx/include/__new/destroying_delete_t.h

@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___NEW_DESTROYING_DELETE_T_H
+#define _LIBCPP___NEW_DESTROYING_DELETE_T_H
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER >= 20
+// purposefully not using versioning namespace
+namespace std {
+// Enable the declaration even if the compiler doesn't support the language
+// feature.
+struct destroying_delete_t {
+  explicit destroying_delete_t() = default;
+};
+inline constexpr destroying_delete_t destroying_delete{};
+} // namespace std
+#endif
+
+#endif // _LIBCPP___NEW_DESTROYING_DELETE_T_H