util: print External address from inspect

Fixes: #28250

Author: rosaxxny

lib/internal/util/inspect.js

@@ -63,6 +63,7 @@ const {
   kRejected,
   previewEntries,
   getConstructorName: internalGetConstructorName,
+  getExternalValue,
   propertyFilter: {
     ALL_PROPERTIES,
     ONLY_ENUMERABLE
@@ -977,8 +978,10 @@ function formatRaw(ctx, value, recurseTimes, typedArray) {
       }
     } else {
       if (keys.length === 0 && protoProps === undefined) {
-        if (isExternal(value))
-          return ctx.stylize('[External]', 'special');
+        if (isExternal(value)) {
+          const address = getExternalValue(value);
+          return ctx.stylize(`[External: ${address}]`, 'special');
+        }
         return `${getCtxStyle(value, constructor, tag)}{}`;
       }
       braces[0] = `${getCtxStyle(value, constructor, tag)}{`;

src/node_util.cc

@@ -11,6 +11,7 @@ using v8::Array;
 using v8::ArrayBufferView;
 using v8::Boolean;
 using v8::Context;
+using v8::External;
 using v8::FunctionCallbackInfo;
 using v8::FunctionTemplate;
 using v8::Global;
@@ -19,6 +20,7 @@ using v8::Integer;
 using v8::Isolate;
 using v8::KeyCollectionMode;
 using v8::Local;
+using v8::MaybeLocal;
 using v8::Object;
 using v8::ONLY_CONFIGURABLE;
 using v8::ONLY_ENUMERABLE;
@@ -68,6 +70,20 @@ static void GetConstructorName(
   args.GetReturnValue().Set(name);
 }
 
+static void GetExternalValue(
+    const FunctionCallbackInfo<Value>& args) {
+  CHECK(args[0]->IsExternal());
+  auto isolate = args.GetIsolate();
+  Local<External> external = args[0].As<External>();
+
+  void* ptr = external->Value();
+  char val[20];
+  snprintf(val, sizeof(val), "%p", ptr);
+
+  MaybeLocal<String> ret = String::NewFromUtf8(isolate, val);
+  args.GetReturnValue().Set(ret.ToLocalChecked());
+}
+
 static void GetPromiseDetails(const FunctionCallbackInfo<Value>& args) {
   // Return undefined if it's not a Promise.
   if (!args[0]->IsPromise())
@@ -314,6 +330,7 @@ void Initialize(Local<Object> target,
   env->SetMethodNoSideEffect(target, "getOwnNonIndexProperties",
                                      GetOwnNonIndexProperties);
   env->SetMethodNoSideEffect(target, "getConstructorName", GetConstructorName);
+  env->SetMethodNoSideEffect(target, "getExternalValue", GetExternalValue);
   env->SetMethod(target, "sleep", Sleep);
 
   env->SetMethod(target, "arrayBufferViewHasBuffer", ArrayBufferViewHasBuffer);

test/parallel/test-util-inspect.js

@@ -147,8 +147,8 @@ assert.strictEqual(
   "[String: 'hello'] { [length]: 5, [Symbol(foo)]: 123 }"
 );
 
-assert.strictEqual(util.inspect((new JSStream())._externalStream),
-                   '[External]');
+assert.match(util.inspect((new JSStream())._externalStream),
+             /^\[External: .*?\]$/);
 
 {
   const regexp = /regexp/;