TestStringEqualsBadLength.java

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 * 2 along with this work; if not, write to the Free Software Foundation,
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/*
 * @test
 * @bug 8027445
 * @summary String.equals() may be called with a length whose upper bits are not cleared
 *
 * @run main/othervm -XX:-UseOnStackReplacement -XX:-BackgroundCompilation
 *      compiler.intrinsics.string.TestStringEqualsBadLength
 */

package compiler.intrinsics.string;

import java.util.Arrays;

public class TestStringEqualsBadLength {

    int v1;
    int v2;

    boolean m(String s1) {
        int l = v2 - v1; // 0 - (-1) = 1. On 64 bit: 0xffffffff00000001
        char[] arr = new char[l];
        arr[0] = 'a';
        String s2 = new String(arr);
        // The string length is not reloaded but the value computed is
        // reused so pointer computation must not use
        // 0xffffffff00000001
        return s2.equals(s1);
    }

    // Same thing with String.compareTo()
    int m2(String s1) {
        int l = v2 - v1;
        char[] arr = new char[l+1];
        arr[0] = 'a';
        arr[1] = 'b';
        String s2 = new String(arr);
        return s2.compareTo(s1);
    }

    // Same thing with equals() for arrays
    boolean m3(char[] arr1) {
        int l = v2 - v1; // 0 - (-1) = 1. On 64 bit: 0xffffffff00000001
        char[] arr2 = new char[l];
        arr2[0] = 'a';
        return Arrays.equals(arr2, arr1);
    }

    static public void main(String[] args) {
        TestStringEqualsBadLength tse = new TestStringEqualsBadLength();
        tse.v1 = -1;
        tse.v2 = 0;
        char[] arr = new char[1];
        arr[0] = 'a';
        for (int i = 0; i < 20000; i++) {
            tse.m("a");
            tse.m2("ab");
            tse.m3(arr);
        }

        System.out.println("TEST PASSED");
    }
}