From b4d0d09b54fa6a9666aa9d01045d37b3886bce01 Mon Sep 17 00:00:00 2001
Date: Fri, 22 Jan 2021 16:56:40 +0800
Subject: 8207160: ClassReader::adjustMethodParams can
 potentially return null if the args list is empty

Summary: <javac>: adjustMethodParams can potentially return null if the args list is empty
LLT: langtools/test/tools/javac/AvoidNPEAtClassReader/AvoidNPEAtClassReaderTest.java
Bug url: https://bugs.openjdk.java.net/browse/JDK-8207160
---
 .../com/sun/tools/javac/jvm/ClassReader.java  |  3 ++
 .../AvoidNPEAtClassReaderTest.java            | 43 +++++++++++++++++
 .../pkg/Outer$Inner.jasm                      | 42 ++++++++++++++++
 .../AvoidNPEAtClassReader/pkg/Outer.jasm      | 48 +++++++++++++++++++
 4 files changed, 136 insertions(+)
 create mode 100644 langtools/test/tools/javac/AvoidNPEAtClassReader/AvoidNPEAtClassReaderTest.java
 create mode 100644 langtools/test/tools/javac/AvoidNPEAtClassReader/pkg/Outer$Inner.jasm
 create mode 100644 langtools/test/tools/javac/AvoidNPEAtClassReader/pkg/Outer.jasm

diff --git a/langtools/src/share/classes/com/sun/tools/javac/jvm/ClassReader.java b/langtools/src/share/classes/com/sun/tools/javac/jvm/ClassReader.java
index 402489234..637d83b2f 100644
--- a/langtools/src/share/classes/com/sun/tools/javac/jvm/ClassReader.java
+++ b/langtools/src/share/classes/com/sun/tools/javac/jvm/ClassReader.java
@@ -2051,6 +2051,9 @@ public class ClassReader {
     }
 
     private List<Type> adjustMethodParams(long flags, List<Type> args) {
+        if (args.isEmpty()) {
+            return args;
+        }
         boolean isVarargs = (flags & VARARGS) != 0;
         if (isVarargs) {
             Type varargsElem = args.last();
diff --git a/langtools/test/tools/javac/AvoidNPEAtClassReader/AvoidNPEAtClassReaderTest.java b/langtools/test/tools/javac/AvoidNPEAtClassReader/AvoidNPEAtClassReaderTest.java
new file mode 100644
index 000000000..3b47d6944
--- /dev/null
+++ b/langtools/test/tools/javac/AvoidNPEAtClassReader/AvoidNPEAtClassReaderTest.java
@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2018, 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 8207160
+ * @summary ClassReader::adjustMethodParams can potentially return null if the args list is empty
+ * @compile pkg/Outer.jasm pkg/Outer$Inner.jasm AvoidNPEAtClassReaderTest.java
+ */
+
+
+/** this test is checking that javac doesn't fail with NPE when reading inner classes with constructors
+ *  that doesn't have as a parameter a reference to the outer class. Such constructors were generated by
+ *  versions of javac previous to JDK7.
+ */
+
+import pkg.*;
+
+public class AvoidNPEAtClassReaderTest {
+    public void bar(Outer outer) {
+        Object stuff = outer.foo();
+    }
+}
diff --git a/langtools/test/tools/javac/AvoidNPEAtClassReader/pkg/Outer$Inner.jasm b/langtools/test/tools/javac/AvoidNPEAtClassReader/pkg/Outer$Inner.jasm
new file mode 100644
index 000000000..d3ee1331c
--- /dev/null
+++ b/langtools/test/tools/javac/AvoidNPEAtClassReader/pkg/Outer$Inner.jasm
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2018, 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.
+ */
+
+package  pkg;
+
+super public final class Outer$Inner
+	version 52:0
+{
+
+final synthetic Field this$0:"Lpkg/Outer;";
+
+public Method "<init>":"()V"
+	stack 1 locals 1
+{
+		aload_0;
+		invokespecial	Method java/lang/Object."<init>":"()V";
+		return;
+}
+
+public final InnerClass Inner=class Outer$Inner of class Outer;
+
+} // end Class Outer$Inner
diff --git a/langtools/test/tools/javac/AvoidNPEAtClassReader/pkg/Outer.jasm b/langtools/test/tools/javac/AvoidNPEAtClassReader/pkg/Outer.jasm
new file mode 100644
index 000000000..29239b139
--- /dev/null
+++ b/langtools/test/tools/javac/AvoidNPEAtClassReader/pkg/Outer.jasm
@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package  pkg;
+
+super public class Outer
+	version 52:0
+{
+
+
+public Method "<init>":"()V"
+	stack 1 locals 1
+{
+		aload_0;
+		invokespecial	Method java/lang/Object."<init>":"()V";
+		return;
+}
+
+public Method foo:"()Lpkg/Outer$Inner;"
+	stack 1 locals 1
+{
+		aconst_null;
+		areturn;
+}
+
+public final InnerClass Inner=class Outer$Inner of class Outer;
+
+} // end Class Outer
-- 
2.19.0