JVM throws ClassFormatError instead of NoClassDefFoundError.

Name: akC45999 Date: 12/03/98



Chapter 5.1.1 of the first specification revision reads :

  "Otherwise, if it is determined that the selected file is not a well-formed
  class file (pass 1 of 4.9.1) or is not of a class file of a supported major
  or minor version (?4.1), class or interface resolution throws a
  NoClassDefFoundError."

Chapter 5.3.1 of the revised specification reads :

  "If the purported representation is not in ClassFile format (pass 1 of 4.9.1),
  or is not of a supported major or minor version, loading throws a
  ClassFormatError."

This bug filed against JDK-116a.

Following test makes attempt to load truncated class-file and gets
ClassFormatError instead of NoClassDefFoundError.

=============================== test.java ==================================

import java.io.*;

class myClassLoader extends ClassLoader {

  public synchronized Class loadClass(String name, boolean resolve) {

Class c = null;
try{
c = findSystemClass(name);
} catch (ClassNotFoundException e) {
}

if (c == null) {
byte data[];

try {
FileInputStream in = new FileInputStream("badClass.class");
data = new byte[in.available()];
in.read(data);
} catch (Exception e) {
System.out.println(e);
return null;
}
c = defineClass(data, 0, data.length);
}
return c;
  }
}

public class test {

  public static void main(String argv[]) throws ClassNotFoundException {

myClassLoader c = new myClassLoader();
c.loadClass("badClass");
  }
}

=============================== badClass.jcod ==================================

class badClass {
  0xCAFEBABE;
  3; // minor version
  45; // version
  [] { // Constant Pool
    ; // first element is empty
    class #10; // #1
    class #12; // #2
    Method #2 #4; // #3
    NameAndType #6 #5; // #4
    Utf8 "()V"; // #5
    Utf8 "<init>"; // #6
    Utf8 "Code"; // #7
    Utf8 "LineNumberTable"; // #8
    Utf8 "SourceFile"; // #9
    Utf8 "badClass"; // #10
    Utf8 "badClass.java"; // #11
    Utf8 "java/lang/Object"; // #12
  } // Constant Pool

  0x0021; // access
  #1;// this_cpx
  #2;// super_cpx

  [] { // Interfaces
  } // Interfaces

  [] { // fields
  } // fields

  [] { // methods
    { // Member
      0x0001; // access
      #6; // name_cpx
      #5; // sig_cpx
      [] { // Attributes
        Attr(#7) { // Code
          1; // max_stack
          1; // max_locals
          Bytes[] {
            0x2AB70003B1;
          };
          [] { // Traps
          } // end Traps
          [] { // Attributes
            Attr(#8) { // LineNumberTable
              [] { // LineNumberTable
                0 1;
              }
            } // end LineNumberTable
          } // Attributes
/* } // end Code
      } // Attributes
    } // Member
  } // methods

  [] { // Attributes
    Attr(#9) { // SourceFile
      #11;
    } // end SourceFile
  } // Attributes
} // end class badClass
*/

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novo48% do
java full version "JDK1.1.6N"
java.lang.ClassFormatError: Truncated class file
at java.lang.ClassLoader.defineClass(ClassLoader.java)
at java.lang.ClassLoader.defineClass(ClassLoader.java)
at KlassLoader.loadClass(test.java:24)
at java.lang.ClassLoader.loadClass(ClassLoader.java)
at test.main(test.java:37)
novo48%

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