From b61da8675d9f9d30f264d85a8f19ba0c398836dc Mon Sep 17 00:00:00 2001
Date: Fri, 22 Jan 2021 16:54:50 +0800
Subject: 8015927: Class reference duplicates in constant pool

Summary: <javac>: Class reference duplicates in constant pool
LLT: test/tools/javac/jvm/ClassRefDupInConstantPoolTest.java
Bug url: https://bugs.openjdk.java.net/browse/JDK-8015927
---
 .../com/sun/tools/javac/jvm/ClassWriter.java  |  4 +-
 .../classes/com/sun/tools/javac/jvm/Pool.java | 10 ++-
 .../jvm/ClassRefDupInConstantPoolTest.java    | 63 +++++++++++++++++++
 3 files changed, 74 insertions(+), 3 deletions(-)
 create mode 100644 langtools/test/tools/javac/jvm/ClassRefDupInConstantPoolTest.java

diff --git a/langtools/src/share/classes/com/sun/tools/javac/jvm/ClassWriter.java b/langtools/src/share/classes/com/sun/tools/javac/jvm/ClassWriter.java
index eecd6807f..11b243419 100644
--- a/langtools/src/share/classes/com/sun/tools/javac/jvm/ClassWriter.java
+++ b/langtools/src/share/classes/com/sun/tools/javac/jvm/ClassWriter.java
@@ -461,11 +461,11 @@ public class ClassWriter extends ClassFile {
                 poolbuf.appendChar(pool.put(names.fromString((String)value)));
             } else if (value instanceof UniqueType) {
                 Type type = ((UniqueType)value).type;
-                if (type instanceof MethodType) {
+                if (type.hasTag(METHOD)) {
                     poolbuf.appendByte(CONSTANT_MethodType);
                     poolbuf.appendChar(pool.put(typeSig((MethodType)type)));
                 } else {
-                    if (type.hasTag(CLASS)) enterInner((ClassSymbol)type.tsym);
+                    Assert.check(type.hasTag(ARRAY));
                     poolbuf.appendByte(CONSTANT_Class);
                     poolbuf.appendChar(pool.put(xClassName(type)));
                 }
diff --git a/langtools/src/share/classes/com/sun/tools/javac/jvm/Pool.java b/langtools/src/share/classes/com/sun/tools/javac/jvm/Pool.java
index 4389d08bd..f87c10537 100644
--- a/langtools/src/share/classes/com/sun/tools/javac/jvm/Pool.java
+++ b/langtools/src/share/classes/com/sun/tools/javac/jvm/Pool.java
@@ -28,6 +28,7 @@ package com.sun.tools.javac.jvm;
 import com.sun.tools.javac.code.Kinds;
 import com.sun.tools.javac.code.Symbol;
 import com.sun.tools.javac.code.Symbol.*;
+import com.sun.tools.javac.code.TypeTag;
 import com.sun.tools.javac.code.Type;
 import com.sun.tools.javac.code.Types;
 import com.sun.tools.javac.code.Types.UniqueType;
@@ -126,7 +127,14 @@ public class Pool {
         } else if (o instanceof VarSymbol) {
             return new Variable((VarSymbol)o, types);
         } else if (o instanceof Type) {
-            return new UniqueType((Type)o, types);
+            Type t = (Type)o;
+            // ClassRefs can come from ClassSymbols or from Types.
+            // Return the symbol for these types to avoid duplicates
+            // in the constant pool
+            if (t.hasTag(TypeTag.CLASS))
+                return t.tsym;
+            else
+                return new UniqueType(t, types);
         } else {
             return o;
         }
diff --git a/langtools/test/tools/javac/jvm/ClassRefDupInConstantPoolTest.java b/langtools/test/tools/javac/jvm/ClassRefDupInConstantPoolTest.java
new file mode 100644
index 000000000..98c7cf8da
--- /dev/null
+++ b/langtools/test/tools/javac/jvm/ClassRefDupInConstantPoolTest.java
@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8015927
+ * @summary Class reference duplicates in constant pool
+ * @clean ClassRefDupInConstantPoolTest$Duplicates.class
+ * @run main ClassRefDupInConstantPoolTest
+ */
+
+import java.util.TreeSet;
+
+import com.sun.tools.classfile.*;
+import com.sun.tools.classfile.ConstantPool.*;
+
+public class ClassRefDupInConstantPoolTest {
+    public static void main(String[] args) throws Exception {
+        ClassFile cls = ClassFile.read(ClassRefDupInConstantPoolTest.class.
+                                       getResourceAsStream("ClassRefDupInConstantPoolTest$Duplicates.class"));
+        ConstantPool pool = cls.constant_pool;
+
+        int duplicates = 0;
+        TreeSet<Integer> set = new TreeSet<>();
+        for (CPInfo i : pool.entries()) {
+            if (i.getTag() == ConstantPool.CONSTANT_Class) {
+                CONSTANT_Class_info ci = (CONSTANT_Class_info)i;
+                if (!set.add(ci.name_index)) {
+                    duplicates++;
+                    System.out.println("DUPLICATE CLASS REF " + ci.getName());
+                }
+            }
+        }
+        if (duplicates > 0)
+            throw new Exception("Test Failed");
+    }
+
+    class Duplicates {
+        String concat(String s1, String s2) {
+            return s1 + (s2 == s1 ? " " : s2);
+        }
+    }
+}
-- 
2.19.0