src: free memory before re-setting URLHost value

Fixes: #18302

Backport-PR-URL: #19639
PR-URL: #18357
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

src/node_url.cc

@@ -92,6 +92,16 @@ class URLHost {
   Value value_;
   HostType type_ = HostType::H_FAILED;
 
+  inline void Reset() {
+    using string = std::string;
+    switch (type_) {
+      case HostType::H_DOMAIN: value_.domain.~string(); break;
+      case HostType::H_OPAQUE: value_.opaque.~string(); break;
+      default: break;
+    }
+    type_ = HostType::H_FAILED;
+  }
+
   // Setting the string members of the union with = is brittle because
   // it relies on them being initialized to a state that requires no
   // destruction of old data.
@@ -101,25 +111,22 @@ class URLHost {
   // These helpers are the easiest solution but we might want to consider
   // just not forcing strings into an union.
   inline void SetOpaque(std::string* string) {
+    Reset();
     type_ = HostType::H_OPAQUE;
     new(&value_.opaque) std::string();
     value_.opaque.swap(*string);
   }
 
   inline void SetDomain(std::string* string) {
+    Reset();
     type_ = HostType::H_DOMAIN;
     new(&value_.domain) std::string();
     value_.domain.swap(*string);
   }
 };
 
 URLHost::~URLHost() {
-  using string = std::string;
-  switch (type_) {
-    case HostType::H_DOMAIN: value_.domain.~string(); break;
-    case HostType::H_OPAQUE: value_.opaque.~string(); break;
-    default: break;
-  }
+  Reset();
 }
 
 #define ARGS(XX)                                                              \