Remove incorrect VirtualAllocEx usage

Before: Called VirtualAllocEx on the pointer from MapViewOfFile,
then unmapped both pointers.

After: Use only MapViewOfFile pointer directly.

Why this was wrong:
- VirtualAllocEx is for allocating memory in other processes,
  not the current one
- MapViewOfFile already returns a committed, writable pointer
- Cleanup was using UnmapViewOfFile on both pointers,
  but should use VirtualFreeEx for the VirtualAllocEx pointer
- This could cause subtle memory visibility issues on Windows

Changes in ShmWindows.java:
- Removed lines 118-128 (the VirtualAllocEx call and error handling)
- Removed writePointer from ShmInfo struct assignment
- Updated cleanup() to take only pointer and handle
  (removed writePointer parameter)

Changes in ShmBase.java:
- Removed writePointer field from ShmInfo<HANDLE> class
- Removed writePointer from toString() method

Co-authored-by: Claude <[email protected]>

Author: ctrueden

src/main/java/org/apposed/appose/shm/ShmBase.java

@@ -106,7 +106,6 @@ public String toString() {
 		sb.append(getClass().getSimpleName()).append("{");
 		sb.append("name='").append(name()).append("', size=").append(size());
 		if (info.pointer != null) sb.append(", pointer=").append(info.pointer);
-		if (info.writePointer != null) sb.append(", writePointer=").append(info.writePointer);
 		if (info.handle != null) sb.append("handle=").append(info.handle);
 		sb.append(", closed=").append(closed);
 		sb.append(", unlinked=").append(unlinked);
@@ -129,8 +128,6 @@ protected static class ShmInfo<HANDLE> {
 		/** Pointer referencing the shared memory. */
 		Pointer pointer;
 
-		Pointer writePointer;
-
 		/** File handle for the shared memory block's (pseudo-)file. */
 		HANDLE handle;
 

src/main/java/org/apposed/appose/shm/ShmWindows.java

@@ -64,7 +64,7 @@ private SharedMemoryWindows(final String name, final boolean create, final long
 
 		@Override
 		protected void doClose() {
-			cleanup(info.pointer, info.writePointer, info.handle);
+			cleanup(info.pointer, info.handle);
 		}
 
 		@Override
@@ -115,24 +115,15 @@ private static ShmInfo<WinNT.HANDLE> prepareShm(String name, boolean create, lon
 				throw new RuntimeException("Error mapping shared memory: " + lastError());
 			}
 
-			Pointer writePointer = Kernel32.INSTANCE.VirtualAllocEx(
-				Kernel32.INSTANCE.GetCurrentProcess(),
-				pointer,
-				new BaseTSD.SIZE_T(rsize),
-				WinNT.MEM_COMMIT,
-				WinNT.PAGE_READWRITE
-			);
-			if (isNull(writePointer)) {
-				cleanup(pointer, writePointer, hMapFile);
-				throw new RuntimeException("Error committing to the shared memory pages: " + lastError());
-			}
+			// Note: MapViewOfFile already returns a writable pointer.
+			// We do not need VirtualAllocEx, which is for allocating memory in other processes.
+			// The mapped view is already committed and accessible.
 
 			ShmInfo<WinNT.HANDLE> info = new ShmInfo<>();
 			info.name = shmName;
 			info.rsize = rsize; // REQUESTED size
 			info.size = shm_size; // ALLOCATED size
 			info.pointer = pointer;
-			info.writePointer = writePointer;
 			info.handle = hMapFile;
 			info.unlinkOnClose = create;
 			return info;
@@ -192,8 +183,7 @@ private static long getSHMSize(final WinNT.HANDLE hMapFile) {
 		}
 	}
 
-	private static void cleanup(Pointer pointer, Pointer writePointer, WinNT.HANDLE handle) {
-		if (!isNull(writePointer)) Kernel32.INSTANCE.UnmapViewOfFile(writePointer);
+	private static void cleanup(Pointer pointer, WinNT.HANDLE handle) {
 		if (!isNull(pointer)) Kernel32.INSTANCE.UnmapViewOfFile(pointer);
 		if (handle != null) Kernel32.INSTANCE.CloseHandle(handle);
 	}