From 7411dda919ba903b1c1e21fd66ee83a62a098e07 Mon Sep 17 00:00:00 2001
From: Teng Zhang <zhangt2333@gmail.com>
Date: Sat, 21 Sep 2024 16:44:04 +0800
Subject: [PATCH] Fix incorrect result when an empty bitset intersects with
 itself

---
 src/main/java/pascal/taie/util/collection/RegularBitSet.java | 3 +++
 src/main/java/pascal/taie/util/collection/SparseBitSet.java  | 3 +++
 src/test/java/pascal/taie/util/collection/IBitSetTest.java   | 3 +++
 3 files changed, 9 insertions(+)

diff --git a/src/main/java/pascal/taie/util/collection/RegularBitSet.java b/src/main/java/pascal/taie/util/collection/RegularBitSet.java
index 111dfcda8..ef12b31b3 100644
--- a/src/main/java/pascal/taie/util/collection/RegularBitSet.java
+++ b/src/main/java/pascal/taie/util/collection/RegularBitSet.java
@@ -312,6 +312,9 @@ public int previousClearBit(int fromIndex) {
 
     @Override
     public boolean intersects(IBitSet set) {
+        if (this.isEmpty() || set.isEmpty()) {
+            return false;
+        }
         if (this == set) {
             return true;
         }
diff --git a/src/main/java/pascal/taie/util/collection/SparseBitSet.java b/src/main/java/pascal/taie/util/collection/SparseBitSet.java
index b0599e164..b848b294e 100644
--- a/src/main/java/pascal/taie/util/collection/SparseBitSet.java
+++ b/src/main/java/pascal/taie/util/collection/SparseBitSet.java
@@ -482,6 +482,9 @@ public int previousClearBit(int fromIndex) {
 
     @Override
     public boolean intersects(IBitSet set) {
+        if (this.isEmpty() || set.isEmpty()) {
+            return false;
+        }
         if (this == set) {
             return true;
         }
diff --git a/src/test/java/pascal/taie/util/collection/IBitSetTest.java b/src/test/java/pascal/taie/util/collection/IBitSetTest.java
index 89692bee8..883848345 100644
--- a/src/test/java/pascal/taie/util/collection/IBitSetTest.java
+++ b/src/test/java/pascal/taie/util/collection/IBitSetTest.java
@@ -73,8 +73,10 @@ void testClear() {
     @Test
     void testIntersects() {
         IBitSet s1 = of();
+        assertFalse(s1.intersects(s1));
         IBitSet s2 = of();
         assertFalse(s1.intersects(s2));
+        assertFalse(s2.intersects(s1));
         s2 = of(1, 233, 666);
         assertFalse(s1.intersects(s2));
         assertFalse(s2.intersects(s1));
@@ -83,6 +85,7 @@ void testIntersects() {
         assertTrue(s2.intersects(s1));
         s1.clear(666);
         assertFalse(s1.intersects(s2));
+        assertFalse(s2.intersects(s1));
     }
 
     @Test