Add trampoline to enable pointer -> handle code calls

src/factory.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 546 matching lines @@
                                           PretenureFlag pretenure) {
   if (Smi::IsValid(static_cast<intptr_t>(value))) {
     return Handle<Object>(Smi::FromIntptr(static_cast<intptr_t>(value)),
                           isolate());
   } else {
     return NewNumber(static_cast<double>(value), pretenure);
   }
 }
 
 
+// Used to "safely" transition from pointer-based runtime code to Handle-based
+// runtime code. When a GC happens during the called Handle-based code, a
+// failure object is returned to the pointer-based code to cause it abort and
+// re-trigger a gc of it's own. Since this double-gc will cause the Handle-based
+// code to be called twice, it must be idempotent.
+class IdempotentHandleToPointerCodeTrampoline {

[Michael Starzinger, 2013/07/05 07:49:07]

nit: s/HandleToPointer/PointerToHandle/

[danno, 2013/07/05 09:35:54]

Done.

+ public:
+  explicit IdempotentHandleToPointerCodeTrampoline(Isolate* isolate)
+      : isolate_(isolate) {}
+
+  template<typename R>
+  MUST_USE_RESULT MaybeObject* Call(R (*function)()) {
+    int scavenges = isolate_->heap()->gc_count();

[Michael Starzinger, 2013/07/05 07:49:07]

nit: Since this doesn't only count minor GCs, but all GCs, let's rename this
local variable s/scavenges/collections/. Same comment applies several times
below.

[danno, 2013/07/05 09:35:54]

Done.

+    (*function)();
+    return (scavenges == isolate_->heap()->gc_count())
+        ? isolate_->heap()->true_value()
+        : reinterpret_cast<MaybeObject*>(Failure::RetryAfterGC());
+  }
+
+  template<typename R>
+  MUST_USE_RESULT MaybeObject* CallWithReturnValue(R (*function)()) {
+    int scavenges = isolate_->heap()->gc_count();
+    MaybeObject* result = (*function)();

[Michael Starzinger, 2013/07/05 07:49:07]

I think the called function is not allowed to return a MaybeObject of it's own.
Handlified code has to either return Handle<T> or something that is below Object
in the type hierarchy. Can we s/MaybeObject/Object/ here? Same comment applies
several times
below.

[danno, 2013/07/05 09:35:54]

Done.

+    return (scavenges == isolate_->heap()->gc_count())
+        ? result
+        : reinterpret_cast<MaybeObject*>(Failure::RetryAfterGC());
+  }
+
+  template<typename R, typename P1>
+  MUST_USE_RESULT MaybeObject* Call(R (*function)(P1), P1 p1) {
+    int scavenges = isolate_->heap()->gc_count();
+    (*function)(p1);
+    return (scavenges == isolate_->heap()->gc_count())
+        ? isolate_->heap()->true_value()
+        : reinterpret_cast<MaybeObject*>(Failure::RetryAfterGC());
+  }
+
+  template<typename R, typename P1>
+  MUST_USE_RESULT MaybeObject* CallWithReturnValue(
+      R (*function)(P1),
+      P1 p1) {
+    int scavenges = isolate_->heap()->gc_count();
+    MaybeObject* result = (*function)(p1);
+    return (scavenges == isolate_->heap()->gc_count())
+        ? result
+        : reinterpret_cast<MaybeObject*>(Failure::RetryAfterGC());
+  }
+
+  template<typename R, typename P1, typename P2>
+  MUST_USE_RESULT MaybeObject* Call(
+      R (*function)(P1, P2),
+      P1 p1,
+      P2 p2) {
+    int scavenges = isolate_->heap()->gc_count();
+    (*function)(p1, p2);
+    return (scavenges == isolate_->heap()->gc_count())
+        ? isolate_->heap()->true_value()
+        : reinterpret_cast<MaybeObject*>(Failure::RetryAfterGC());
+  }
+
+  template<typename R, typename P1, typename P2>
+  MUST_USE_RESULT MaybeObject* CallWithReturnValue(
+      R (*function)(P1, P2),
+      P1 p1,
+      P2 p2) {
+    int scavenges = isolate_->heap()->gc_count();
+    MaybeObject* result = (*function)(p1, p2);
+    return (scavenges == isolate_->heap()->gc_count())
+        ? result
+        : reinterpret_cast<MaybeObject*>(Failure::RetryAfterGC());
+  }
+
+ private:
+  Isolate* isolate_;
+};
+
 
 } }  // namespace v8::internal
 
 #endif  // V8_FACTORY_H_