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13  * accompanied this code).
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23 
24 /*
25  * @test
26  * @bug 8234687
27  * @summary change javap reporting on unknown attributes
28  * @modules jdk.jdeps/com.sun.tools.javap
29  * @run main BadAttributeName
30  */
31 
32 
33 import java.io.*;
34 import java.nio.file.*;
35 
36 public class BadAttributeName {
37 
38     public static String source = "public class Test {\n" +
39                                   "    public static void main(String[] args) {}\n" +
40                                   "}";
41 
main(String[] args)42     public static void main(String[] args) throws Exception {
43         final File srcFile = new File("Test.java");
44         Files.writeString(Path.of("Test.java"), source);
45 
46         final String[] javacOpts = {"Test.java"};
47 
48         if (com.sun.tools.javac.Main.compile(javacOpts) != 0) {
49             throw new Exception("Can't compile embedded test.");
50         }
51 
52         RandomAccessFile raf = new RandomAccessFile("Test.class", "rw");
53         String sourceFile = "SourceFile";
54         long namePos = getConstantPoolUTF8Pos(raf, sourceFile);
55         if (namePos < 0) {
56             throw new Exception("The class file contains no SourceFile attribute.");
57         }
58 
59         raf.seek(namePos); // Jump to the SourceFile name
60         // Create a "custom" attribute by reusing/renaming an unimportant existing one
61         String customAttr = "CustomAttribute".substring(0, sourceFile.length());
62         raf.writeUTF(customAttr);
63         raf.close();
64 
65         String[] opts = { "-v", "Test.class" };
66         StringWriter sw = new StringWriter();
67         PrintWriter pout = new PrintWriter(sw);
68 
69         com.sun.tools.javap.Main.run(opts, pout);
70         pout.flush();
71 
72         String expect = customAttr + ": length = 0x2 (unknown attribute)";
73         if (sw.toString().indexOf(expect) == -1) {
74             sw.toString().lines().forEach(System.out::println);
75             throw new Exception("expected text not found: " + expect);
76         }
77     }
78 
getConstantPoolUTF8Pos(RandomAccessFile cfile, String name)79     private static long getConstantPoolUTF8Pos(RandomAccessFile cfile, String name) throws Exception {
80         cfile.seek(0);
81         int v1, v2;
82         v1 = cfile.readInt();
83         // System.out.println("Magic: " + String.format("%X", v1));
84 
85         v1 = cfile.readUnsignedShort();
86         v2 = cfile.readUnsignedShort();
87         // System.out.println("Version: " + String.format("%d.%d", v1, v2));
88 
89         v1 = cfile.readUnsignedShort();
90         // System.out.println("CPool size: " + v1);
91         // Exhaust the constant pool
92         for (; v1 > 1; v1--) {
93             // System.out.print(".");
94             byte tag = cfile.readByte();
95             switch (tag) {
96                 case 7  : // Class
97                 case 8  : // String
98                     // Data is 2 bytes long
99                     cfile.skipBytes(2);
100                     break;
101                 case 3  : // Integer
102                 case 4  : // Float
103                 case 9  : // FieldRef
104                 case 10 : // MethodRef
105                 case 11 : // InterfaceMethodRef
106                 case 12 : // Name and Type
107                     // Data is 4 bytes long
108                     cfile.skipBytes(4);
109                     break;
110                 case 5  : // Long
111                 case 6  : // Double
112                     // Data is 8 bytes long
113                     cfile.skipBytes(8);
114                     break;
115                 case 1  : // Utf8
116                     long fp = cfile.getFilePointer();
117                     String s = cfile.readUTF();
118                     if (s.equals(name)) {
119                         return fp;
120                     }
121                     break;
122                 default :
123                     throw new Exception("Unexpected tag in CPool: [" + tag + "] at "
124                             + Long.toHexString(cfile.getFilePointer()));
125             }
126         }
127         // System.out.println();
128 
129         // Bummer! Name not found!
130         return -1L;
131     }
132 }
133