BUG: withOwnerThread closes MappedMemorySegment

[sundararajan.athijegannathan at oracle.com]

javadoc of MemorySegment.withOwnerThread starts as follows:

"    * Obtains a new memory segment backed by the same underlying memory 
region as this segment,
      * but with different owner thread. As a side-effect, this segment 
will be marked as <em>not alive</em>,
      * and subsequent operations on this segment will result in runtime 
errors.
"

So the behavior seen is as the specification.

-Sundar

On 23/09/20 7:36 am, Ty Young wrote:
> A bug seems to have been introduced wherein using withOwnerThread 
> causes a MappedMemorySegment to close:
>
>
>     File file = new File("./test");
>
>         if(file.exists())
>             file.delete();
>
>         file.createNewFile();
>
>         MappedMemorySegment nativeFile = 
> MemorySegment.mapFromPath(file.toPath(), 0, 4096, 
> FileChannel.MapMode.READ_WRITE);
>
>         System.out.println(nativeFile.isAlive());
>
>         MappedMemorySegment segment = 
> (MappedMemorySegment)nativeFile.asSlice(4);
>         segment = (MappedMemorySegment)nativeFile.asSlice(4);
>         segment = 
> (MappedMemorySegment)nativeFile.asSlice(4).withOwnerThread(null);
>
>         System.out.println(nativeFile.isAlive());
>         System.out.println(segment.isAlive());
>
>
> which prints true, false, and then true. The original 
> MappedMemorySegment was never closed, so this is unexpected.
>