[blink_gc_plugin] Complain about stack-allocated classes with GC bases, but not arbitrary non-stack…

tools/clang/blink_gc_plugin/BlinkGCPluginConsumer.cpp

 // Copyright 2015 The Chromium 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 "BlinkGCPluginConsumer.h"
 
 #include <algorithm>
 #include <set>
 
 #include "CheckDispatchVisitor.h"
@@ skipping 159 matching lines @@
     return;
   }
 
   CheckClass(info);
 }
 
 void BlinkGCPluginConsumer::CheckClass(RecordInfo* info) {
   if (!info)
     return;
 
-  // Check consistency of stack-allocated hierarchies.
-  if (info->IsStackAllocated()) {
-    for (auto& base : info->GetBases())
-      if (!base.second.info()->IsStackAllocated())
-        reporter_.DerivesNonStackAllocated(info, &base.second);
-  }
-
   if (CXXMethodDecl* trace = info->GetTraceMethod()) {
     if (trace->isPure())
       reporter_.ClassDeclaresPureVirtualTrace(info, trace);
   } else if (info->RequiresTraceMethod()) {
     reporter_.ClassRequiresTraceMethod(info);
   }
 
   // Check polymorphic classes that are GC-derived or have a trace method.
   if (info->record()->hasDefinition() && info->record()->isPolymorphic()) {
     // TODO: Check classes that inherit a trace method.
     CXXMethodDecl* trace = info->GetTraceMethod();
     if (trace || info->IsGCDerived())
       CheckPolymorphicClass(info, trace);
   }
 
   {
     CheckFieldsVisitor visitor;
     if (visitor.ContainsInvalidFields(info))
       reporter_.ClassContainsInvalidFields(info, visitor.invalid_fields());
   }
 
   if (info->IsGCDerived()) {
+    // It is illegal for a class to be both stack allocated and garbage
+    // collected.
+    if (info->IsStackAllocated()) {
+      for (auto& base : info->GetBases()) {
+        RecordInfo* base_info = base.second.info();
+        if (Config::IsGCBase(base_info->name()) || base_info->IsGCDerived()) {
+          reporter_.StackAllocatedDerivesGarbageCollected(info, &base.second);
+        }
+      }
+    }
+
     if (!info->IsGCMixin()) {
       CheckLeftMostDerived(info);
       CheckDispatch(info);
       if (CXXMethodDecl* newop = info->DeclaresNewOperator())
         if (!Config::IsIgnoreAnnotated(newop))
           reporter_.ClassOverridesNew(info, newop);
     }
 
     {
       CheckGCRootsVisitor visitor;
@@ skipping 496 matching lines @@
   SourceLocation spelling_location = source_manager.getSpellingLoc(loc);
   PresumedLoc ploc = source_manager.getPresumedLoc(spelling_location);
   if (ploc.isInvalid()) {
     // If we're in an invalid location, we're looking at things that aren't
     // actually stated in the source.
     return false;
   }
   *filename = ploc.getFilename();
   return true;
 }