[debugger] simplify fetching scripts for inspector.

src/api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 8929 matching lines @@
   return ToApiHandle<DebugInterface::Script>(
       handle_scope.CloseAndEscape(script_obj));
 }
 
 void DebugInterface::GetLoadedScripts(
     v8::Isolate* v8_isolate,
     PersistentValueVector<DebugInterface::Script>& scripts) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(v8_isolate);
   ENTER_V8(isolate);
   i::HandleScope handle_scope(isolate);
-  i::Handle<i::FixedArray> instances = isolate->debug()->GetLoadedScripts();
-  for (int i = 0; i < instances->length(); i++) {
-    i::Handle<i::Script> script =
-        i::Handle<i::Script>(i::Script::cast(instances->get(i)));
-    if (script->type() != i::Script::TYPE_NORMAL) continue;
-    scripts.Append(ToApiHandle<Script>(script));
+  i::Factory* factory = isolate->factory();
+  if (!factory->script_list()->IsWeakFixedArray()) return;
+  i::Handle<i::WeakFixedArray> array =
+      i::Handle<i::WeakFixedArray>::cast(factory->script_list());
+  {
+    i::Script::Iterator iterator(isolate);
+    i::Handle<i::Script> script;
+    while (!(script = i::Handle<i::Script>(iterator.Next())).is_null()) {

[kozy, 2016/10/31 14:59:11]

I think that i::Handle<i::Script>(Object*) tries to get isolate from passed
Object [1] and it will produce a crash. And will it work correctly if we pass
isolate as second argument to avoid mentioned crash? It looks for me that
is_null() check returns true only if handle was created with cstor without
arguments, otherwise it just allocates one more handle in handle scope, event if
it's null.

And I've question about how V8 works. Can we just not create a handle and
iterate through raw pointers?
i::Script* script = nullptr;
while ((script = iterator.Next()) != nullptr) {
...
if (script->HasValidSource())
scripts.Append(ToApiHandle<Script>(i::handle(script)));
}
It looks for me like nothing in loop code can call gc to move objects in memory.
What functions call are potentially can run gc?

[1] https://cs.chromium.org/chromium/src/v8/src/handles.h?rcl=1477898213&l=99

[Yang, 2016/11/02 12:25:55]

Good point. I changed the code after running tests. But we at least need the
handle to pass to ToApiHandle.

+      if (script->type() != i::Script::TYPE_NORMAL) continue;
+      if (script->HasValidSource()) scripts.Append(ToApiHandle<Script>(script));
+    }
   }
 }
 
 Local<String> CpuProfileNode::GetFunctionName() const {
   const i::ProfileNode* node = reinterpret_cast<const i::ProfileNode*>(this);
   i::Isolate* isolate = node->isolate();
   const i::CodeEntry* entry = node->entry();
   i::Handle<i::String> name =
       isolate->factory()->InternalizeUtf8String(entry->name());
   if (!entry->has_name_prefix()) {
@@ skipping 671 matching lines @@
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 }  // namespace internal
 }  // namespace v8