[vmkit-commits] [PATCH] Add support for extra VM-only fields, use this to add fields to j.l.Class in OpenJDK

[Will Dietz]

On Fri, Oct 28, 2011 at 5:31 PM, Nicolas Geoffray
<nicolas.geoffray at gmail.com> wrote:
> Hi Will!
> I think this patch could work, but I would definitely try a more 'localized'
> approach before doing it this way.
> I think that in the bootstrap process of OpenJDK, you should update the
> Class::virtualSize field for java.lang.Class to include these two new
> fields, and that would be it. No need to extend the JavaField array (the
> Java side of things does not have to know we added new fields).
> Of course, you need to make sure no java.lang.Class objects are allocated
> *before* you change the size.
> Thanks, and let me know if that worked!
> Nicolas

I was playing nice with the JavaFields not so that anything from Java
could see the fields (I actually intentionally tried to hide them from
Java code), but so that the created LLVM types (LLVMInfo) for
java.lang.Class matched up.  Not knowing better, that seemed like
something to ensure was correct.

However, what you suggested is much simpler and seems to work equally
well, thanks for the good suggestion.

Updated patch inlined below :)

~Will

>From f57fed146de2962a5e3c1306515ab9374862647e Mon Sep 17 00:00:00 2001
From: Will Dietz <w at wdtz.org>
Date: Mon, 31 Oct 2011 15:23:24 -0500
Subject: [PATCH] Add extra fields to JavaObjectClass to hold CommonClass and
 protection domain.

---
 lib/J3/ClassLib/OpenJDK/ClasspathReflect.h |   13 +++++++------
 lib/J3/ClassLib/OpenJDK/JavaUpcalls.cpp    |    2 ++
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/lib/J3/ClassLib/OpenJDK/ClasspathReflect.h
b/lib/J3/ClassLib/OpenJDK/ClasspathReflect.h
index 75d35a7..4075a5f 100644
--- a/lib/J3/ClassLib/OpenJDK/ClasspathReflect.h
+++ b/lib/J3/ClassLib/OpenJDK/ClasspathReflect.h
@@ -38,30 +38,31 @@ private:
   JavaObject* annotations;
   JavaObject* declaredAnnotations;
   JavaObject* annotationType;
+  // Extra fields added by VM
+  UserCommonClass * internalClass;
+  JavaObject * pd;

 public:

   static UserCommonClass* getClass(JavaObjectClass* cl) {
     llvm_gcroot(cl, 0);
-    UNIMPLEMENTED();
-    return NULL;
+    return cl->internalClass;
   }

   static void setClass(JavaObjectClass* cl, UserCommonClass* vmdata) {
     llvm_gcroot(cl, 0);
-    UNIMPLEMENTED();
+    cl->internalClass = vmdata;
   }

   static void setProtectionDomain(JavaObjectClass* cl, JavaObject* pd) {
     llvm_gcroot(cl, 0);
     llvm_gcroot(pd, 0);
-    UNIMPLEMENTED();
+    cl->pd = pd;
   }

   static JavaObject* getProtectionDomain(JavaObjectClass* cl) {
     llvm_gcroot(cl, 0);
-    UNIMPLEMENTED();
-    return NULL;
+    return cl->pd;
   }

   static void staticTracer(JavaObjectClass* obj, word_t closure) {
diff --git a/lib/J3/ClassLib/OpenJDK/JavaUpcalls.cpp
b/lib/J3/ClassLib/OpenJDK/JavaUpcalls.cpp
index a4a48c8..476b6e3 100644
--- a/lib/J3/ClassLib/OpenJDK/JavaUpcalls.cpp
+++ b/lib/J3/ClassLib/OpenJDK/JavaUpcalls.cpp
@@ -468,6 +468,8 @@ void
Classpath::initialiseClasspath(JnjvmClassLoader* loader) {

   newClass =
     UPCALL_CLASS(loader, "java/lang/Class");
+  // Add space for extra fields, see ClasspathReflect.h
+  newClass->virtualSize += 2*sizeof(void*);

   newThrowable =
     UPCALL_CLASS(loader, "java/lang/Throwable");
-- 
1.7.5.1