From 000a42a913a0d4fee3868526512e087c4203aab9 Mon Sep 17 00:00:00 2001
From: Dan Heidinga <daniel_heidinga@ca.ibm.com>
Date: Tue, 14 May 2019 13:59:15 -0400
Subject: [PATCH 1/3] Correct buffer size to fix memory corruption

The analysis in eclipse/openj9#5696 shows that there
is a out of bounds access that is fixed by increasing
the buffer size by 8.  Validated by having the VM
increase all unsafe allocates by 8 and the problem
no longer occurs.

fixes: #79

Signed-off-by: Dan Heidinga <daniel_heidinga@ca.ibm.com>
---
 runtime/src/main/java/com4j/Variant.java | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/runtime/src/main/java/com4j/Variant.java b/runtime/src/main/java/com4j/Variant.java
index 92fae32..58d0c67 100644
--- a/runtime/src/main/java/com4j/Variant.java
+++ b/runtime/src/main/java/com4j/Variant.java
@@ -360,10 +360,10 @@ public int comEnumValue() {
      * Creates an empty {@link Variant}.
      */
     public Variant() {
-        image = ByteBuffer.allocateDirect(16);
+        image = ByteBuffer.allocateDirect(24);
         image.order(ByteOrder.LITTLE_ENDIAN);
         // The initial content of a buffer is, in general, undefined. See the documentation of java.nio.Buffer.
-        byte[] b = new byte[16]; // this initializes the array with zeros
+        byte[] b = new byte[24]; // this initializes the array with zeros
         image.put(b); // this prints the zeros to the buffer to guarantee, that the buffer is initialized with zeros.
         image.position(0);
     }

From f7344f4a6449e3e35195a2475a3122ec7d021fa3 Mon Sep 17 00:00:00 2001
From: Dan Heidinga <daniel_heidinga@ca.ibm.com>
Date: Wed, 15 May 2019 09:39:49 -0400
Subject: [PATCH 2/3] Determine Variant structure size correctly on 32 vs 64bit

Structure contains pointers so its size depends on whether
the system is 32 or 64 bit

Signed-off-by: Dan Heidinga <daniel_heidinga@ca.ibm.com>
---
 runtime/src/main/java/com4j/Variant.java | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/runtime/src/main/java/com4j/Variant.java b/runtime/src/main/java/com4j/Variant.java
index 58d0c67..04211f1 100644
--- a/runtime/src/main/java/com4j/Variant.java
+++ b/runtime/src/main/java/com4j/Variant.java
@@ -356,14 +356,30 @@ public int comEnumValue() {
         }
     }
 
+    /**
+     * Determine the correct size of {@link Variant}.
+     *
+     * The size of the variant depends on whether this is
+     * a 32 or 64 bit system due to pointers in the structure
+     * definition.  See https://docs.microsoft.com/en-gb/windows/desktop/api/oaidl/ns-oaidl-tagvariant
+     */
+    private static int variantSize() {
+        String model = System.getProperty("sun.arch.data.model");
+        if (model.equals("64")) {
+            return 24;
+        }
+        return 16;
+    }
+
     /**
      * Creates an empty {@link Variant}.
      */
     public Variant() {
-        image = ByteBuffer.allocateDirect(24);
+        final int variantSize = variantSize();
+        image = ByteBuffer.allocateDirect(variantSize);
         image.order(ByteOrder.LITTLE_ENDIAN);
         // The initial content of a buffer is, in general, undefined. See the documentation of java.nio.Buffer.
-        byte[] b = new byte[24]; // this initializes the array with zeros
+        byte[] b = new byte[variantSize]; // this initializes the array with zeros
         image.put(b); // this prints the zeros to the buffer to guarantee, that the buffer is initialized with zeros.
         image.position(0);
     }

From bf099f288a2ba86b7f0a18d810e2d2f8fd615d65 Mon Sep 17 00:00:00 2001
From: Dan Heidinga <daniel_heidinga@ca.ibm.com>
Date: Wed, 15 May 2019 10:18:46 -0400
Subject: [PATCH 3/3] Use `os.arch` and move variantSize check into static
 final variable

Signed-off-by: Dan Heidinga <daniel_heidinga@ca.ibm.com>
---
 runtime/src/main/java/com4j/Variant.java | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/runtime/src/main/java/com4j/Variant.java b/runtime/src/main/java/com4j/Variant.java
index 04211f1..8203244 100644
--- a/runtime/src/main/java/com4j/Variant.java
+++ b/runtime/src/main/java/com4j/Variant.java
@@ -364,18 +364,20 @@ public int comEnumValue() {
      * definition.  See https://docs.microsoft.com/en-gb/windows/desktop/api/oaidl/ns-oaidl-tagvariant
      */
     private static int variantSize() {
-        String model = System.getProperty("sun.arch.data.model");
-        if (model.equals("64")) {
+	/* Typical os.arch values: `x86_64`, `amd64` */
+        String model = System.getProperty("os.arch");
+        if (model.indexOf("64") != -1) {
             return 24;
         }
         return 16;
     }
 
+    private static final int variantSize = variantSize();
+
     /**
      * Creates an empty {@link Variant}.
      */
     public Variant() {
-        final int variantSize = variantSize();
         image = ByteBuffer.allocateDirect(variantSize);
         image.order(ByteOrder.LITTLE_ENDIAN);
         // The initial content of a buffer is, in general, undefined. See the documentation of java.nio.Buffer.