test/runtime/Unsafe/AllocateMemory.java

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/*
 * @test
 * @requires vm.compMode != "Xcomp"
 * @summary Verifies behaviour of Unsafe.allocateMemory
 * @library /testlibrary
 * @modules java.base/jdk.internal.misc
 *          java.management
 * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:MallocMaxTestWords=100m AllocateMemory
 */

import jdk.test.lib.*;
import sun.misc.Unsafe;
import static jdk.test.lib.Asserts.*;

public class AllocateMemory {
    public static void main(String args[]) throws Exception {
        Unsafe unsafe = Utils.getUnsafe();

        // Allocate a byte, write to the location and read back the value
        long address = unsafe.allocateMemory(1);
        assertNotEquals(address, 0L);

        unsafe.putByte(address, Byte.MAX_VALUE);
        assertEquals(Byte.MAX_VALUE, unsafe.getByte(address));
        unsafe.freeMemory(address);

        // Call to allocateMemory() with a negative value should result in an IllegalArgumentException
        try {
            address = unsafe.allocateMemory(-1);
            throw new RuntimeException("Did not get expected IllegalArgumentException");
        } catch (IllegalArgumentException e) {
            // Expected
            assertNotEquals(address, 0L);
        }

        // allocateMemory() should throw an OutOfMemoryError when the underlying malloc fails,
        // we test this by limiting the malloc using -XX:MallocMaxTestWords
        try {
            address = unsafe.allocateMemory(100 * 1024 * 1024 * 8);
        } catch (OutOfMemoryError e) {
            // Expected
            return;
        }
        throw new RuntimeException("Did not get expected OutOfMemoryError");
    }
}