AndroidBugPOC.java

AndroidBugPOC.java

import java.util.*;
import java.lang.*;

/**
Output:
with 75 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 93 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 193 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 214 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 258 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 273 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 286 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 302 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 334 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 379 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 380 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 389 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 416 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 450 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 478 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 480 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 504 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 511 random hashcode items, 1 / 1000000 (9.999999999999999E-5%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
with 520 random hashcode items, 2 / 1000000 (1.9999999999999998E-4%) of sorts triggered an exception
java.lang.IllegalArgumentException: Comparison method violates its general contract!
java.lang.IllegalArgumentException: Comparison method violates its general contract!
 */
public class AndroidBugPOC {
  static abstract class Thing {
    public String toString() {
      return getClass().getName() + " (" + hashCode() + ")";
    }
  }
  static class HigherPriorityThing extends Thing {
  }
  static class LowerPriorityThing extends Thing {
  }

  // RandomHashcodeThing has a randomly-determined hashcode that stays constant
  // for each instance of itself.
  static class RandomHashcodeThing extends Thing {
    private int hash;
    RandomHashcodeThing() {
        this.hash = new Random().ints(Integer.MIN_VALUE, Integer.MAX_VALUE).findFirst().getAsInt();;
    }
    public int hashCode() { 
      return hash;
    }
  }
  // NormalHashcodeThing does not override hashCode.
  static class NormalHashcodeThing extends Thing {

  }
  static class StaticHashcodeThing extends Thing {
    public int hashCode() { 
      return 987654;
    }
  }
  public static void main(String[] args) {
      for (int i=0; i<1000; i++) {
          doesException(i, 1000000);
      }
  }

  public static int doesException(int thingCount, int testCount) {
    List<Thing> things = new ArrayList<>();
    things.add(new HigherPriorityThing());
    things.add(new LowerPriorityThing());

    for (int i=0; i<thingCount;i++) {
      things.add(new RandomHashcodeThing());
    }
    

    int times = 0;
    List<Exception> exceptions = new ArrayList<>();
    for (int i=0; i<testCount; i++) {
        try {
        test(things);
        } catch (IllegalArgumentException e) {
            times++;
            exceptions.add(e);
        }
    }
    if (times > 0) {
        System.out.println("with "+thingCount+" random hashcode items, "+times+" / "+testCount+" ("+((times*1.0/testCount)*100)+"%) of sorts triggered an exception");
        for (Exception e : exceptions) {
            System.out.println(e);
        }
    }
    return times;

  }
  public static void test(List<Thing> things) {
    things.sort((a, b) -> {
      // This sort is meant to be a loose approximation of sortSimPhoneAccountsForEmergency:
      // https://android.googlesource.com/platform/packages/services/Telecomm/+/725404c9d3c5fe4faf4afe87d96d624b3a511a77/src/com/android/server/telecom/CreateConnectionProcessor.java#587

       // Prioritize HigherPriorityThing
      if (a instanceof HigherPriorityThing ^ b instanceof HigherPriorityThing) {
        return a instanceof HigherPriorityThing ? -1 : 1;
      }

      // Also prioritize LowerPriorityThing
      if (a instanceof LowerPriorityThing ^ b instanceof LowerPriorityThing) {
        return a instanceof LowerPriorityThing ? -1 : 1;
      }

      // Otherwise subtract hashcodes (BUG)
      return a.hashCode() - b.hashCode();
      // Fixed code:
      // return Integer.compare(a.hashCode(), b.hashCode());
    });
    check(things);
  }

  public static void check(List<Thing> things) {
    if (things.get(0) instanceof HigherPriorityThing && things.get(1) instanceof LowerPriorityThing) {
      System.out.print("");
    } else {
      System.out.println("\nBAD - " + things);
    }
  }
}