8357919: Arena::allocate returns segments with address zero if the segment length is zero after JDK-8345687

Reviewed-by: mcimadamore

Author: minborg

src/java.base/share/classes/jdk/internal/foreign/SegmentFactories.java

@@ -192,6 +192,13 @@ private static long allocateNativeInternal(long byteSize, long byteAlignment, Me
         }
         // Align the allocation size up to a multiple of 8 so we can init the memory with longs
         long alignedSize = init ? Utils.alignUp(byteSize, Long.BYTES) : byteSize;
+        // Check for wrap around
+        if (alignedSize < 0) {
+            throw new OutOfMemoryError();
+        }
+        // Always allocate at least some memory so that zero-length segments have distinct
+        // non-zero addresses.
+        alignedSize = Math.max(1, alignedSize);
 
         long allocationSize;
         long allocationBase;

test/jdk/java/foreign/TestSegments.java

@@ -24,6 +24,7 @@
 /*
  * @test
  * @requires vm.bits == 64
+ * @modules java.base/sun.nio.ch
  * @run testng/othervm -Xmx4G -XX:MaxDirectMemorySize=1M --enable-native-access=ALL-UNNAMED TestSegments
  */
 
@@ -58,6 +59,12 @@ public void testZeroLengthNativeSegment() {
         try (Arena arena = Arena.ofConfined()) {
             var segment = arena.allocate(0, 1);
             assertEquals(segment.byteSize(), 0);
+            if (segment.address() == 0) {
+                fail("Segment address is zero");
+            }
+            if (segment.address() == arena.allocate(0, 1).address()) {
+                fail("Segment address was not distinct");
+            }
             MemoryLayout seq = MemoryLayout.sequenceLayout(0, JAVA_INT);
             segment = arena.allocate(seq);
             assertEquals(segment.byteSize(), 0);
@@ -71,6 +78,20 @@ public void testZeroLengthNativeSegment() {
         }
     }
 
+    @Test
+    public void testZeroLengthNativeSegmentHyperAligned() {
+        long byteAlignment = 1024;
+        try (Arena arena = Arena.ofConfined()) {
+            var segment = arena.allocate(0, byteAlignment);
+            assertEquals(segment.byteSize(), 0);
+            if (segment.address() == 0) {
+                fail("Segment address is zero");
+            }
+            assertTrue(segment.maxByteAlignment() >= byteAlignment);
+        }
+    }
+
+
     @Test(expectedExceptions = { OutOfMemoryError.class,
                                  IllegalArgumentException.class })
     public void testAllocateTooBig() {