[debugger] Prevent shared function info duplicates

src/compiler.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/compiler.h"
 
 #include <algorithm>
 
 #include "src/ast/ast-numbering.h"
 #include "src/ast/prettyprinter.h"
@@ skipping 1224 matching lines @@
   DCHECK(!isolate->has_pending_exception());
   DCHECK(shared->is_compiled());
   DCHECK(shared->HasDebugCode());
   return true;
 }
 
 bool Compiler::CompileForLiveEdit(Handle<Script> script) {
   Isolate* isolate = script->GetIsolate();
   DCHECK(AllowCompilation::IsAllowed(isolate));
 
+  // In order to ensure that live edit function info collection finds the newly
+  // generated shared function infos, clear the script's list temporarily
+  // and restore it at the end of this method.
+  Handle<Object> old_function_infos(script->shared_function_infos(), isolate);
+  script->set_shared_function_infos(Smi::FromInt(0));
+
   // Start a compilation.
   Zone zone(isolate->allocator());
   ParseInfo parse_info(&zone, script);
   CompilationInfo info(&parse_info, Handle<JSFunction>::null());
   parse_info.set_global();
   info.MarkAsDebug();
   // TODO(635): support extensions.
-  if (CompileToplevel(&info).is_null()) {
-    return false;
+  const bool compilation_succeeded = CompileToplevel(&info).is_null();
+
+  // Restore the original function info list in order to remain 'side-effect
+  // free' as much as possible, since some code expects the old shared function
+  // infos to stick around.
+  script->set_shared_function_infos(*old_function_infos);
+
+  if (compilation_succeeded) {
+    // Check postconditions on success.
+    DCHECK(!isolate->has_pending_exception());

[Yang, 2016/05/12 07:43:14]

We could just rephrase this as DCHECK(!compilation_succeeded ||
!isolate->has_pending_exception());

[jgruber1, 2016/05/12 08:26:46]

Rewrote this part to again exit early on compilation failure since we have some
more logic coming up in the successful case.

   }
 
-  // Check postconditions on success.
-  DCHECK(!isolate->has_pending_exception());
-  return true;
+  return compilation_succeeded;
 }
 
 // TODO(turbofan): In the future, unoptimized code with deopt support could
 // be generated lazily once deopt is triggered.
 bool Compiler::EnsureDeoptimizationSupport(CompilationInfo* info) {
   DCHECK_NOT_NULL(info->literal());
   DCHECK_NOT_NULL(info->scope());
   Handle<SharedFunctionInfo> shared = info->shared_info();
   if (!shared->has_deoptimization_support()) {
     Zone zone(info->isolate()->allocator());
@@ skipping 491 matching lines @@
     MaybeHandle<Code> code;
     if (cached.code != nullptr) code = handle(cached.code);
     Handle<Context> native_context(function->context()->native_context());
     SharedFunctionInfo::AddToOptimizedCodeMap(shared, native_context, code,
                                               literals, BailoutId::None());
   }
 }
 
 }  // namespace internal
 }  // namespace v8