[libc-commits] [libc] [libc] Implement cpp::unique_ptr utility (PR #206701)

[Michael Jones via libc-commits]

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@@ -0,0 +1,214 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Standalone implementation of std::unique_ptr.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_CPP_UNIQUE_PTR_H
+#define LLVM_LIBC_SRC___SUPPORT_CPP_UNIQUE_PTR_H
+
+#include "src/__support/CPP/new.h"
+#include "src/__support/CPP/type_traits.h"
+#include "src/__support/CPP/utility.h"
+#include "src/__support/macros/attributes.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace cpp {
+
+/// A wrapper for deleting objects by default.
+template <typename T> struct default_delete {
+  LIBC_INLINE constexpr default_delete() = default;
+
+  template <typename U, typename = typename enable_if<
+                            is_convertible<U *, T *>::value>::type>
+  LIBC_INLINE constexpr default_delete(const default_delete<U> &) {}
+
+  LIBC_INLINE constexpr void operator()(T *ptr) const {
+    static_assert(sizeof(T) > 0, "cannot delete an incomplete type");
+    delete ptr;
+  }
+};
+
+/// A wrapper for deleting array objects by default.
+template <typename T> struct default_delete<T[]> {
+  LIBC_INLINE constexpr default_delete() = default;
+
+  template <typename U, typename = typename enable_if<
+                            is_convertible<U (*)[], T (*)[]>::value>::type>
+  LIBC_INLINE constexpr default_delete(const default_delete<U[]> &) {}
+
+  template <typename U, typename = typename enable_if<
+                            is_convertible<U (*)[], T (*)[]>::value>::type>
+  LIBC_INLINE constexpr void operator()(U *ptr) const {
+    static_assert(sizeof(U) > 0, "cannot delete an incomplete type");
+    delete[] ptr;
+  }
+};
+
+/// A smart pointer that owns and manages another object through a pointer.
+template <typename T, typename Deleter = default_delete<T>> class unique_ptr {
+  T *ptr_ = nullptr;
+  Deleter deleter_;
+
+  template <typename U, typename E> friend class unique_ptr;
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michaelrj-google wrote:

why is this necessary?

https://github.com/llvm/llvm-project/pull/206701