From 21f34bd99c0403b34ae9301e309ef3430682827e Mon Sep 17 00:00:00 2001
From: mutouyun <orz@orzz.org>
Date: Sun, 27 Feb 2022 18:30:42 +0800
Subject: [PATCH] =?UTF-8?q?=E5=9C=A8=E5=8F=AF=E8=83=BD=E7=9A=84=E6=83=85?=
 =?UTF-8?q?=E5=86=B5=E4=B8=8B=E4=BD=BF=E7=94=A8std=E7=9A=84construct=5Fat/?=
 =?UTF-8?q?destroy=5Fat?=
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Content-Transfer-Encoding: 8bit

---
 src/libipc/utility/construct.h | 33 +++++++++++++++++++++++++++++++++
 test/test_utility.cpp          | 17 +++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/src/libipc/utility/construct.h b/src/libipc/utility/construct.h
index 1cf7f3a..ad21ffd 100644
--- a/src/libipc/utility/construct.h
+++ b/src/libipc/utility/construct.h
@@ -9,15 +9,27 @@
 #include <new>          // placement-new
 #include <type_traits>  // std::enable_if_t
 #include <utility>      // std::forward
+#include <memory>       // std::construct_at, std::destroy_at, std::addressof
+#include <cstddef>
 
 #include "libipc/def.h"
+#include "libipc/detect_plat.h"
 
 LIBIPC_NAMESPACE_BEG_
 
+/**
+ * @brief Creates an object at a given address, like 'construct_at' in c++20
+ * @see https://en.cppreference.com/w/cpp/memory/construct_at
+*/
+
 template <typename T, typename... A>
 auto construct(void *p, A &&... args)
   -> std::enable_if_t<::std::is_constructible<T, A...>::value, T *> {
+#if defined(LIBIPC_CPP_20)
+  return std::construct_at(static_cast<T *>(p), std::forward<A>(args)...);
+#else
   return ::new (p) T(std::forward<A>(args)...);
+#endif
 }
 
 template <typename T, typename... A>
@@ -26,9 +38,30 @@ auto construct(void *p, A &&... args)
   return ::new (p) T{std::forward<A>(args)...};
 }
 
+/**
+ * @brief Destroys an object at a given address, like 'destroy_at' in c++17
+ * @see https://en.cppreference.com/w/cpp/memory/destroy_at
+*/
+
 template <typename T>
 void *destroy(T *p) noexcept {
+#if defined(LIBIPC_CPP_17)
+  std::destroy_at(p);
+#else
   p->~T();
+#endif
+  return p;
+}
+
+template <typename T, std::size_t N>
+void *destroy(T (*p)[N]) noexcept {
+#if defined(LIBIPC_CPP_20)
+  std::destroy_at(p);
+#elif defined(LIBIPC_CPP_17)
+  std::destroy(std::begin(*p), std::end(*p));
+#else
+  for (auto &elem : *p) destroy(std::addressof(elem));
+#endif
   return p;
 }
 
diff --git a/test/test_utility.cpp b/test/test_utility.cpp
index 4d6e7d8..8d3751e 100644
--- a/test/test_utility.cpp
+++ b/test/test_utility.cpp
@@ -18,16 +18,33 @@ TEST(utility, construct) {
   EXPECT_EQ(pfoo->a_, 123);
   EXPECT_EQ(pfoo->b_, 321);
   EXPECT_EQ(pfoo->c_, '1');
+  ipc::destroy(pfoo);
 
   struct Bar : Foo {
     Bar(int a, short b, char c)
         : Foo{a, b, c} {}
+    ~Bar() { a_ = 0; }
   };
   std::aligned_storage_t<sizeof(Bar)> bar;
   Bar *pbar = ipc::construct<Bar>(&bar, 123, short(321), '1');
   EXPECT_EQ(pbar->a_, 123);
   EXPECT_EQ(pbar->b_, 321);
   EXPECT_EQ(pbar->c_, '1');
+  ipc::destroy(pbar);
+  EXPECT_EQ(pbar->a_, 0);
+
+  std::aligned_storage_t<sizeof(Bar)> bars[3];
+  for (auto &b : bars) {
+    auto pb = ipc::construct<Bar>(&b, 321, short(123), '3');
+    EXPECT_EQ(pb->a_, 321);
+    EXPECT_EQ(pb->b_, 123);
+    EXPECT_EQ(pb->c_, '3');
+  }
+  ipc::destroy(reinterpret_cast<Bar(*)[3]>(&bars));
+  for (auto &b : bars) {
+    auto pb = reinterpret_cast<Bar *>(&b);
+    EXPECT_EQ(pb->a_, 0);
+  }
 }
 
 namespace {