hazptr: add checks for double retire in non-debug modes

Summary: Add steps to hazptr_obj construction and retirement to catch misuse bugs such as double retire.

Reviewed By: yfeldblum

Differential Revision: D6851965

fbshipit-source-id: 026e578b595792e3118b6b4b9a22c8c1dce6acba

folly/experimental/hazptr/hazptr-impl.h

@@ -221,6 +221,7 @@ inline constexpr hazptr_domain::hazptr_domain(memory_resource* mr) noexcept
 template <typename T, typename D>
 inline void hazptr_obj_base<T, D>::retire(hazptr_domain& domain, D deleter) {
   DEBUG_PRINT(this << " " << &domain);
+  retireCheck();
   deleter_ = std::move(deleter);
   reclaim_ = [](hazptr_obj* p) {
     auto hobp = static_cast<hazptr_obj_base*>(p);
@@ -288,8 +289,8 @@ inline bool hazptr_obj_base_refcounted<T, D>::release_ref() {
 
 template <typename T, typename D>
 inline void hazptr_obj_base_refcounted<T, D>::preRetire(D deleter) {
-  DCHECK(next_ == nullptr);
   deleter_ = std::move(deleter);
+  retireCheck();
   reclaim_ = [](hazptr_obj* p) {
     auto hrobp = static_cast<hazptr_obj_base_refcounted*>(p);
     if (hrobp->release_ref()) {

folly/experimental/hazptr/hazptr.h

@@ -113,7 +113,25 @@ class hazptr_obj {
   friend struct hazptr_priv;
 
   void (*reclaim_)(hazptr_obj*);
-  hazptr_obj* next_{nullptr}; // nullptr for debugging
+  hazptr_obj* next_;
+
+ public:
+  hazptr_obj() {
+    // Only for catching misuse bugs like double retire
+    next_ = this;
+  }
+
+ private:
+  void retireCheck() {
+    // Only for catching misuse bugs like double retire
+    if (next_ != this) {
+      retireCheckFail();
+    }
+  }
+
+  FOLLY_NOINLINE void retireCheckFail() {
+    CHECK_EQ(next_, this);
+  }
 
   const void* getObjPtr() const;
 };