Add error string to C++

include/grpc++/impl/codegen/call.h

@@ -574,7 +574,7 @@ class CallOpClientRecvStatus {
     op->data.recv_status_on_client.trailing_metadata = metadata_map_->arr();
     op->data.recv_status_on_client.status = &status_code_;
     op->data.recv_status_on_client.status_details = &error_message_;
-    op->data.recv_status_on_client.error_string = nullptr;
+    op->data.recv_status_on_client.error_string = &error_string_;
     op->flags = 0;
     op->reserved = NULL;
   }
@@ -591,14 +591,16 @@ class CallOpClientRecvStatus {
     *recv_status_ = Status(static_cast<StatusCode>(status_code_),
                            grpc::string(GRPC_SLICE_START_PTR(error_message_),
                                         GRPC_SLICE_END_PTR(error_message_)),
-                           binary_error_details);
+                           binary_error_details, grpc::string(error_string_));
     g_core_codegen_interface->grpc_slice_unref(error_message_);
+    g_core_codegen_interface->gpr_free((void*)error_string_);
     recv_status_ = nullptr;
   }
 
  private:
   MetadataMap* metadata_map_;
   Status* recv_status_;
+  const char* error_string_;
   grpc_status_code status_code_;
   grpc_slice error_message_;
 };

include/grpc++/impl/codegen/status.h

@@ -46,6 +46,16 @@ class Status {
         error_message_(error_message),
         binary_error_details_(error_details) {}
 
+  /// Construct an instance with \a code,  \a error_message and
+  /// \a error_details. It is an error to construct an OK status with non-empty
+  /// \a error_message and/or \a error_details.
+  Status(StatusCode code, const grpc::string& error_message,
+         const grpc::string& error_details, const grpc::string& error_string)
+      : code_(code),
+        error_message_(error_message),
+        binary_error_details_(error_details),
+        error_string_(error_string) {}
+
   // Pre-defined special status objects.
   /// An OK pre-defined instance.
   static const Status& OK;
@@ -59,6 +69,8 @@ class Status {
   /// Return the (binary) error details.
   // Usually it contains a serialized google.rpc.Status proto.
   grpc::string error_details() const { return binary_error_details_; }
+  /// Return the full fidelity error string, which includes all child errors.
+  grpc::string error_string() const { return error_string_; }
 
   /// Is the status OK?
   bool ok() const { return code_ == StatusCode::OK; }
@@ -72,6 +84,7 @@ class Status {
   StatusCode code_;
   grpc::string error_message_;
   grpc::string binary_error_details_;
+  grpc::string error_string_;
 };
 
 }  // namespace grpc