Make hazptr_obj copyable and moveable

Summary: hazptr_obj is copyable and moveable, but doing so would cause a bug, because the next ptr would point to the object that was copied/moved from, which can oftentimes be garbage or another object that has not yet retired. This diff changes the copy/move constructors and assignment operators to simply check that the rhs has not been retired.

Reviewed By: magedm

Differential Revision: D7539444

fbshipit-source-id: f9325c7b886fcf4b553344ee37f2355ca41268b6

folly/experimental/hazptr/hazptr.h

@@ -127,9 +127,20 @@ class hazptr_obj {
   hazptr_obj* next_;
 
  public:
-  hazptr_obj() {
-    // Only for catching misuse bugs like double retire
-    next_ = this;
+  // All constructors set next_ to this in order to catch misuse bugs like
+  // double retire.
+  hazptr_obj() noexcept : next_(this) {}
+
+  hazptr_obj(const hazptr_obj&) noexcept : next_(this) {}
+
+  hazptr_obj(hazptr_obj&&) noexcept : next_(this) {}
+
+  hazptr_obj& operator=(const hazptr_obj&) {
+    return *this;
+  }
+
+  hazptr_obj& operator=(hazptr_obj&&) {
+    return *this;
   }
 
  private:

folly/experimental/hazptr/test/HazptrTest.cpp

@@ -733,3 +733,31 @@ TEST_F(HazptrTest, ForkTest) {
     _exit(0); // Do not print gtest results
   }
 }
+
+TEST_F(HazptrTest, CopyAndMoveTest) {
+  struct Obj : hazptr_obj_base<Obj> {
+    int a;
+  };
+
+  auto p1 = new Obj();
+  auto p2 = new Obj(*p1);
+  p1->retire();
+  p2->retire();
+
+  p1 = new Obj();
+  p2 = new Obj(std::move(*p1));
+  p1->retire();
+  p2->retire();
+
+  p1 = new Obj();
+  p2 = new Obj();
+  *p2 = *p1;
+  p1->retire();
+  p2->retire();
+
+  p1 = new Obj();
+  p2 = new Obj();
+  *p2 = std::move(*p1);
+  p1->retire();
+  p2->retire();
+}