[serializer] print reference stack when external reference is unknown

Print the reference stack when V8 is unable to encode an external
reference in debug builds so that it's easier for the embedder
to track the external reference down.

Refs: https://github.com/nodejs/node/pull/38905
Change-Id: Ia86eeb87833d7de0eccc7bc040301c78ddb3240c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2988831Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Joyee Cheung <joyee@igalia.com>
Cr-Commit-Position: refs/heads/master@{#75546}

src/snapshot/serializer.cc

@@ -318,6 +318,23 @@ void Serializer::ResolvePendingForwardReference(int forward_reference_id) {
   }
 }
 
+ExternalReferenceEncoder::Value Serializer::EncodeExternalReference(
+    Address addr) {
+  Maybe<ExternalReferenceEncoder::Value> result =
+      external_reference_encoder_.TryEncode(addr);
+  if (result.IsNothing()) {
+#ifdef DEBUG
+    PrintStack(std::cerr);
+#endif
+    void* addr_ptr = reinterpret_cast<void*>(addr);
+    v8::base::OS::PrintError("Unknown external reference %p.\n", addr_ptr);
+    v8::base::OS::PrintError("%s\n",
+                             ExternalReferenceTable::ResolveSymbol(addr_ptr));
+    v8::base::OS::Abort();
+  }
+  return result.FromJust();
+}
+
 void Serializer::RegisterObjectIsPending(Handle<HeapObject> obj) {
   if (*obj == ReadOnlyRoots(isolate()).not_mapped_symbol()) return;
 

src/snapshot/serializer.h

@@ -244,9 +244,8 @@ class Serializer : public SerializerDeserializer {
   // Returns true if the given heap object is a bytecode handler code object.
   bool ObjectIsBytecodeHandler(Handle<HeapObject> obj) const;
 
-  ExternalReferenceEncoder::Value EncodeExternalReference(Address addr) {
-    return external_reference_encoder_.Encode(addr);
-  }
+  ExternalReferenceEncoder::Value EncodeExternalReference(Address addr);
+
   Maybe<ExternalReferenceEncoder::Value> TryEncodeExternalReference(
       Address addr) {
     return external_reference_encoder_.TryEncode(addr);