From 784a7c1ef9996d166aedcd4aacd1fa12016dde7f Mon Sep 17 00:00:00 2001
From: wuwen <wuwen.55@aliyun.com>
Date: Sun, 8 Oct 2023 16:31:26 +0800
Subject: [PATCH] fixes GitHub Issue 462 (Internal class issues in the Java 21)

---
 .../bytecode/MethodParametersAttribute.java   |   9 +++--
 src/test/javassist/JvstTest5.java             |  32 ++++++++++++++++++
 ...nerClassWithoutParameters$InnerClass.class | Bin 0 -> 495 bytes
 .../Java21InnerClassWithoutParameters.class   | Bin 0 -> 358 bytes
 4 files changed, 38 insertions(+), 3 deletions(-)
 create mode 100644 src/test/resources/Java21InnerClassWithoutParameters$InnerClass.class
 create mode 100644 src/test/resources/Java21InnerClassWithoutParameters.class

diff --git a/src/main/javassist/bytecode/MethodParametersAttribute.java b/src/main/javassist/bytecode/MethodParametersAttribute.java
index b9c252a9..f78f6c72 100644
--- a/src/main/javassist/bytecode/MethodParametersAttribute.java
+++ b/src/main/javassist/bytecode/MethodParametersAttribute.java
@@ -32,7 +32,8 @@ public class MethodParametersAttribute extends AttributeInfo {
         byte[] data = new byte[names.length * 4 + 1];
         data[0] = (byte)names.length;
         for (int i = 0; i < names.length; i++) {
-            ByteArray.write16bit(cp.addUtf8Info(names[i]), data, i * 4 + 1);
+            String name = names[i];
+            ByteArray.write16bit(name == null ? 0 : cp.addUtf8Info(name), data, i * 4 + 1);
             ByteArray.write16bit(flags[i], data, i * 4 + 3);
         }
 
@@ -61,7 +62,8 @@ public class MethodParametersAttribute extends AttributeInfo {
      * @param i         the position of the parameter.
      */
     public String parameterName(int i) {
-        return getConstPool().getUtf8Info(name(i));
+        int index = name(i);
+        return index == 0 ? null : getConstPool().getUtf8Info(index);
     }
 
     /**
@@ -87,7 +89,8 @@ public class MethodParametersAttribute extends AttributeInfo {
         String[] names = new String[s];
         int[] flags = new int[s];
         for (int i = 0; i < s; i++) {
-            names[i] = cp.getUtf8Info(name(i));
+            int index = name(i);
+            names[i] = index == 0 ? null : cp.getUtf8Info(index);
             flags[i] = accessFlags(i);
         }
 
diff --git a/src/test/javassist/JvstTest5.java b/src/test/javassist/JvstTest5.java
index 4a370632..f1c56837 100644
--- a/src/test/javassist/JvstTest5.java
+++ b/src/test/javassist/JvstTest5.java
@@ -1,5 +1,8 @@
 package javassist;
 
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
 import java.lang.annotation.Annotation;
 import java.lang.reflect.TypeVariable;
 
@@ -9,6 +12,8 @@ import javassist.bytecode.AttributeInfo;
 import javassist.bytecode.ClassFile;
 import javassist.bytecode.ConstPool;
 import javassist.bytecode.InnerClassesAttribute;
+import javassist.bytecode.MethodInfo;
+import javassist.bytecode.MethodParametersAttribute;
 import javassist.bytecode.NestHostAttribute;
 import javassist.bytecode.NestMembersAttribute;
 import javassist.expr.ExprEditor;
@@ -593,4 +598,31 @@ public class JvstTest5 extends JvstTestRoot {
         }
         catch (CannotCompileException e) {}
     }
+
+    public void testGithubIssue462Java21WithoutParameters() throws IOException {
+
+        //This is a class file compiled by Java-21
+        //javac Java21InnerClassWithoutParameters.java
+        //public class Java21InnerClassWithoutParameters {
+        //    class InnerClass implements Runnable {
+        //        public void run() {
+        //        }
+        //    }
+        //}
+        String classFileName = "./Java21InnerClassWithoutParameters$InnerClass.class";
+        ClassLoader classLoader = getClass().getClassLoader();
+        File classFile = new File(classLoader.getResource(classFileName).getFile());
+        
+        CtClass cc = sloader.makeClass(new FileInputStream(classFile));
+        cc.getClassFile().compact();
+
+        ClassFile cf = cc.getClassFile2();
+        ConstPool cp = cf.getConstPool();
+        
+        MethodInfo minfo = cf.getMethod("<init>");
+        MethodParametersAttribute attr
+                = (MethodParametersAttribute)minfo.getAttribute(MethodParametersAttribute.tag);
+        assertEquals(1, attr.size());
+        assertNull(attr.parameterName(0));
+    }
 }
diff --git a/src/test/resources/Java21InnerClassWithoutParameters$InnerClass.class b/src/test/resources/Java21InnerClassWithoutParameters$InnerClass.class
new file mode 100644
index 0000000000000000000000000000000000000000..c1c6cab5287f14cf89edc70d4a69990df9ee01af
GIT binary patch
literal 495
zcmah_O-sW-5Pg%+8l#P^A9xTHL|PGxUKK$KqEf4<)bqAoG$q|YcH`N<<Vo=05Aa8c
zlX%F%Lk{z?Z{EzCo$sH|F97G*2w=hX;e>GE5u%xR6}?2L=icpjCMSmAoyICQX9T;`
z9r<Vw4z8JWd~~Ih%=(GY`YARqX>RUBCg#$}Oz&1T9|56NjlIv665~V?_Bw;wK_}f2
z!Re<{<~IkilEZvHmf7Rqgy=@H@U+t9C9_-+f`>HECh{UKb!t@(i}eVNq15Iw)yBsv
zVW+l@5LW+`nq{jew&C+>2@8B@i_OI%$B?rvMoVP>1N6=SVTrxRv7j!qcR78F7-*Jo
e(Y47|5dL*Iun}>=!U|etY-5dMz;qvNtOLJr9dgV7

literal 0
HcmV?d00001

diff --git a/src/test/resources/Java21InnerClassWithoutParameters.class b/src/test/resources/Java21InnerClassWithoutParameters.class
new file mode 100644
index 0000000000000000000000000000000000000000..a6208c524fd931d0d8839e2f9243612246e320dc
GIT binary patch
literal 358
zcmaiw&q~8U5XQf0(ynf!t=>HpL{!A0=ORd<plB5oJ#XruTha||Holi9!GjOrLltLp
z$+5dIGr#%A$Na5-egRx#U!#LWA<fW5k1$-CPctrzdmlgKOI`#*Z(^MdSA^vF<V9hN
zFuIkd%ZnT5*iQ>nRj)RDly!JC-mEyVuL$Y1d}G4k&N`mgtDOC_$qUKor?U17p4kXT
z8#kRtL4^LCt8mY8Po*#*oNb&uZ1oYc7Fg8j7BPa78^lNQ<qBfAg$^19x~JcuucoZU
a#&T>;&==o9h8^*#WOgx>NH>wf9`FyVAXNVV

literal 0
HcmV?d00001

-- 
2.39.5