GH-44491: [C++] Static Status draft

apache · Oct 21, 2024 · 0634658 · 0634658
1 parent 375b21f
commit 0634658
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Showing 2 changed files with 19 additions and 9 deletions.
diff --git a/cpp/src/arrow/status.cc b/cpp/src/arrow/status.cc
@@ -35,9 +35,11 @@ Status::Status(StatusCode code, std::string msg, std::shared_ptr<StatusDetail> d
 }
 
 void Status::CopyFrom(const Status& s) {
-  delete state_;
+  DeleteState();
   if (s.state_ == nullptr) {
     state_ = nullptr;
+  } else if (s.state_->is_static) {
+    state_ = s.state_;
   } else {
     state_ = new State(*s.state_);
   }
@@ -155,6 +157,12 @@ void Status::Warn(const std::string& message) const {
   ARROW_LOG(WARNING) << message << ": " << ToString();
 }
 
+Status Status::MakeStatic(StatusCode code, std::string msg, std::shared_ptr<StatusDetail> detail) {
+  Status st{code, std::move(msg), std::move(detail)};
+  st.state_->is_static = true;
+  return st;
+} 
+
 #ifdef ARROW_EXTRA_ERROR_CONTEXT
 void Status::AddContextLine(const char* filename, int line, const char* expr) {
   ARROW_CHECK(!ok()) << "Cannot add context line to ok status";

diff --git a/cpp/src/arrow/status.h b/cpp/src/arrow/status.h
@@ -134,13 +134,7 @@ class ARROW_EXPORT [[nodiscard]] Status : public util::EqualityComparable<Status
  public:
   // Create a success status.
   constexpr Status() noexcept : state_(NULLPTR) {}
-  ~Status() noexcept {
-    // ARROW-2400: On certain compilers, splitting off the slow path improves
-    // performance significantly.
-    if (ARROW_PREDICT_FALSE(state_ != NULL)) {
-      DeleteState();
-    }
-  }
+  ~Status() noexcept { DeleteState(); }
 
   Status(StatusCode code, const std::string& msg);
   /// \brief Pluggable constructor for use by sub-systems.  detail cannot be null.
@@ -363,17 +357,25 @@ class ARROW_EXPORT [[nodiscard]] Status : public util::EqualityComparable<Status
   void AddContextLine(const char* filename, int line, const char* expr);
 #endif
 
+  // Construct a Status which is not destroyed and is cheap to copy.
+  static Status MakeStatic(StatusCode code, std::string msg,
+                           std::shared_ptr<StatusDetail> detail);
  private:
   struct State {
     StatusCode code;
     std::string msg;
     std::shared_ptr<StatusDetail> detail;
+    bool is_static = false;
   };
   // OK status has a `NULL` state_.  Otherwise, `state_` points to
   // a `State` structure containing the error code and message(s)
   State* state_;
 
   void DeleteState() {
+    // ARROW-2400: On certain compilers, splitting off the slow path improves
+    // performance significantly.
+    if (ARROW_PREDICT_TRUE(state_ == NULL)) return;
+    if (ARROW_PREDICT_FALSE(state_->is_static)) return;
     delete state_;
     state_ = NULLPTR;
   }
@@ -382,7 +384,7 @@ class ARROW_EXPORT [[nodiscard]] Status : public util::EqualityComparable<Status
 };
 
 void Status::MoveFrom(Status& s) {
-  delete state_;
+  DeleteState();
   state_ = s.state_;
   s.state_ = NULLPTR;
 }