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

[Pavel Labath 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_;
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labath wrote:

I don't think this (trailing `_`) is right style for members. It's definitely not llvm style, and the libc page doesn't have anything to override it. We don't have that many classes to use precedents but the ones I've found (`StreamString` and `expected`), use the same style as regular variables (no `_`).

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