Add construct/destruct helper functions (#26906)

* Add construct/destruct helper functions

Will be used in upcoming promise implementation

* sanitized

BUILD

@@ -709,6 +709,7 @@ grpc_cc_library(
     public_hdrs = GPR_PUBLIC_HDRS,
     visibility = ["@grpc:alt_gpr_base_legacy"],
     deps = [
+        "construct_destruct",
         "debug_location",
         "google_api_upb",
         "gpr_codegen",
@@ -716,6 +717,12 @@ grpc_cc_library(
     ],
 )
 
+grpc_cc_library(
+    name = "construct_destruct",
+    language = "c++",
+    public_hdrs = ["src/core/lib/gprpp/construct_destruct.h"],
+)
+
 grpc_cc_library(
     name = "gpr_codegen",
     language = "c++",

build_autogenerated.yaml

@@ -316,6 +316,7 @@ libs:
   - src/core/lib/gpr/useful.h
   - src/core/lib/gprpp/arena.h
   - src/core/lib/gprpp/atomic.h
+  - src/core/lib/gprpp/construct_destruct.h
   - src/core/lib/gprpp/debug_location.h
   - src/core/lib/gprpp/examine_stack.h
   - src/core/lib/gprpp/fork.h

gRPC-C++.podspec

@@ -545,6 +545,7 @@ Pod::Spec.new do |s|
                       'src/core/lib/gpr/useful.h',
                       'src/core/lib/gprpp/arena.h',
                       'src/core/lib/gprpp/atomic.h',
+                      'src/core/lib/gprpp/construct_destruct.h',
                       'src/core/lib/gprpp/debug_location.h',
                       'src/core/lib/gprpp/dual_ref_counted.h',
                       'src/core/lib/gprpp/examine_stack.h',
@@ -1207,6 +1208,7 @@ Pod::Spec.new do |s|
                               'src/core/lib/gpr/useful.h',
                               'src/core/lib/gprpp/arena.h',
                               'src/core/lib/gprpp/atomic.h',
+                              'src/core/lib/gprpp/construct_destruct.h',
                               'src/core/lib/gprpp/debug_location.h',
                               'src/core/lib/gprpp/dual_ref_counted.h',
                               'src/core/lib/gprpp/examine_stack.h',

gRPC-Core.podspec

@@ -917,6 +917,7 @@ Pod::Spec.new do |s|
                       'src/core/lib/gprpp/arena.cc',
                       'src/core/lib/gprpp/arena.h',
                       'src/core/lib/gprpp/atomic.h',
+                      'src/core/lib/gprpp/construct_destruct.h',
                       'src/core/lib/gprpp/debug_location.h',
                       'src/core/lib/gprpp/dual_ref_counted.h',
                       'src/core/lib/gprpp/examine_stack.cc',
@@ -1795,6 +1796,7 @@ Pod::Spec.new do |s|
                               'src/core/lib/gpr/useful.h',
                               'src/core/lib/gprpp/arena.h',
                               'src/core/lib/gprpp/atomic.h',
+                              'src/core/lib/gprpp/construct_destruct.h',
                               'src/core/lib/gprpp/debug_location.h',
                               'src/core/lib/gprpp/dual_ref_counted.h',
                               'src/core/lib/gprpp/examine_stack.h',

grpc.gemspec

@@ -831,6 +831,7 @@ Gem::Specification.new do |s|
   s.files += %w( src/core/lib/gprpp/arena.cc )
   s.files += %w( src/core/lib/gprpp/arena.h )
   s.files += %w( src/core/lib/gprpp/atomic.h )
+  s.files += %w( src/core/lib/gprpp/construct_destruct.h )
   s.files += %w( src/core/lib/gprpp/debug_location.h )
   s.files += %w( src/core/lib/gprpp/dual_ref_counted.h )
   s.files += %w( src/core/lib/gprpp/examine_stack.cc )

package.xml

@@ -811,6 +811,7 @@
     <file baseinstalldir="/" name="src/core/lib/gprpp/arena.cc" role="src" />
     <file baseinstalldir="/" name="src/core/lib/gprpp/arena.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/gprpp/atomic.h" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/gprpp/construct_destruct.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/gprpp/debug_location.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/gprpp/dual_ref_counted.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/gprpp/examine_stack.cc" role="src" />

src/core/lib/gprpp/construct_destruct.h

@@ -0,0 +1,39 @@
+// Copyright 2021 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef GRPC_CORE_LIB_GPRPP_CONSTRUCT_DESTRUCT_H
+#define GRPC_CORE_LIB_GPRPP_CONSTRUCT_DESTRUCT_H
+
+#include <grpc/impl/codegen/port_platform.h>
+
+#include <utility>
+
+namespace grpc_core {
+
+// Call the destructor of p without having to name the type of p.
+template <typename T>
+void Destruct(T* p) {
+  p->~T();
+}
+
+// Call the constructor of p without having to name the type of p and forward
+// any arguments
+template <typename T, typename... Args>
+void Construct(T* p, Args&&... args) {
+  new (p) T(std::forward<Args>(args)...);
+}
+
+}  // namespace grpc_core
+
+#endif  // GRPC_CORE_LIB_GPRPP_CONSTRUCT_DESTRUCT_H

src/core/lib/gprpp/manual_constructor.h

@@ -31,6 +31,8 @@
 
 #include <grpc/support/log.h>
 
+#include "src/core/lib/gprpp/construct_destruct.h"
+
 namespace grpc_core {
 
 // this contains templated helpers needed to implement the ManualConstructors
@@ -182,7 +184,7 @@ class ManualConstructor {
   Type& operator*() { return *get(); }
   const Type& operator*() const { return *get(); }
 
-  void Init() { new (&space_) Type; }
+  void Init() { Construct(get()); }
 
   // Init() constructs the Type instance using the given arguments
   // (which are forwarded to Type's constructor).
@@ -192,17 +194,17 @@ class ManualConstructor {
   // "new Type();"), so it will leave non-class types uninitialized.
   template <typename... Ts>
   void Init(Ts&&... args) {
-    new (&space_) Type(std::forward<Ts>(args)...);
+    Construct(get(), std::forward<Ts>(args)...);
   }
 
   // Init() that is equivalent to copy and move construction.
   // Enables usage like this:
   //   ManualConstructor<std::vector<int>> v;
   //   v.Init({1, 2, 3});
-  void Init(const Type& x) { new (&space_) Type(x); }
-  void Init(Type&& x) { new (&space_) Type(std::move(x)); }
+  void Init(const Type& x) { Construct(get(), x); }
+  void Init(Type&& x) { Construct(get(), std::forward<Type>(x)); }
 
-  void Destroy() { get()->~Type(); }
+  void Destroy() { Destruct(get()); }
 
  private:
   typename std::aligned_storage<sizeof(Type), alignof(Type)>::type space_;

tools/doxygen/Doxyfile.c++.internal

@@ -1764,6 +1764,7 @@ src/core/lib/gpr/wrap_memcpy.cc \
 src/core/lib/gprpp/arena.cc \
 src/core/lib/gprpp/arena.h \
 src/core/lib/gprpp/atomic.h \
+src/core/lib/gprpp/construct_destruct.h \
 src/core/lib/gprpp/debug_location.h \
 src/core/lib/gprpp/dual_ref_counted.h \
 src/core/lib/gprpp/examine_stack.cc \

tools/doxygen/Doxyfile.core.internal

@@ -1603,6 +1603,7 @@ src/core/lib/gprpp/README.md \
 src/core/lib/gprpp/arena.cc \
 src/core/lib/gprpp/arena.h \
 src/core/lib/gprpp/atomic.h \
+src/core/lib/gprpp/construct_destruct.h \
 src/core/lib/gprpp/debug_location.h \
 src/core/lib/gprpp/dual_ref_counted.h \
 src/core/lib/gprpp/examine_stack.cc \