Prevent losing track of BSTRByReference memory

CHANGES.md

@@ -27,6 +27,8 @@ Bug Fixes
 * [#1279](https://github.com/java-native-access/jna/issues/1279): Remove `DLLCallback` import from `CallbackReference` - [@dyorgio](https://github.com/dyorgio).
 * [#1278](https://github.com/java-native-access/jna/pull/1278): Improve compatibility of `c.s.j.p.WindowUtils#getProcessFilePath` and fix unittests for windows 32bit intel - [@matthiasblaesing](https://github.com/matthiasblaesing).
 * [#1284](https://github.com/java-native-access/jna/pull/1284): Fix illegal access exceptions, when retrieving options for private library interfaces with an instance field - [@fkistner](https://github.com/fkistner).
+* [#1300](https://github.com/java-native-access/jna/pull/1300): Prevent losing track of `BSTRByReference` memory - [@dbwiddis](https://github.com/dbwiddis).
+
 
 Release 5.6.0
 =============

contrib/platform/src/com/sun/jna/platform/win32/WTypes.java

@@ -24,14 +24,15 @@
  */
 package com.sun.jna.platform.win32;
 
+import java.io.UnsupportedEncodingException;
+
 import com.sun.jna.Memory;
 import com.sun.jna.Native;
 import com.sun.jna.Pointer;
 import com.sun.jna.PointerType;
 import com.sun.jna.Structure;
 import com.sun.jna.platform.win32.WinDef.USHORT;
 import com.sun.jna.ptr.ByReference;
-import java.io.UnsupportedEncodingException;
 
 /**
  * Constant defined in WTypes.h
@@ -150,6 +151,9 @@ public String toString() {
  }
 
  public class BSTRByReference extends ByReference {
+
+ private BSTR bstr = null;
+
  public BSTRByReference() {
  super(Native.POINTER_SIZE);
  }
@@ -160,15 +164,29 @@ public BSTRByReference(BSTR value) {
  }
 
  public void setValue(BSTR value) {
+ // Save a local reference to prevent losing value's memory
+ this.bstr = value;
  this.getPointer().setPointer(0, value.getPointer());
  }
 
  public BSTR getValue() {
- return new BSTR(getPointer().getPointer(0));
+ // If memory address hasn't changed, return the stored BSTR
+ if (bstr != null) {
+ if (getPointer().equals(bstr.getPointer())) {
+ return bstr;
+ }
+ // The stored memory has been changed, memory is tracked elsewhere.
+ // Clean up unneeded reference.
+ bstr = null;
+ }
+ // Null check the pointer
+ Pointer p = getPointer().getPointer(0);
+ return p != null ? new BSTR(p) : null;
  }
 
  public String getString() {
- return this.getValue().getValue();
+ BSTR b = this.getValue();
+ return b != null ? b.getValue() : null;
  }
  }