JavaSsist: toBytecode() throws exception java.lang.RuntimeException: remaper.by.moofMonkey.Main class is frozen but him isn't frozen

Question

If I calling toBytecode() method in my context it throws

java.lang.RuntimeException: remaper.by.moofMonkey.Main class is frozen at javassist.CtClassType.checkModify(CtClassType.java:515) at javassist.CtClass.getClassFile(CtClass.java:524) at com.moofMonkey.Main.writeFile(Main.java:340) at com.moofMonkey.Main.saveClasses(Main.java:324) at com.moofMonkey.Main.main(Main.java:309)

My context:

.....
for (CtClass cl : modClasses) {
    cl.stopPruning(true);
    writeFile(cl, "./ModifiedClasses"); //cl.writeFile("./ModifiedClasses");
    cl.stopPruning(false);
}
.....
public static void writeFile(CtClass cl, String directoryName) throws Throwable {
    System.out.println(">> " + cl.getName());

    byte[] bc = cl.toBytecode();

    String s = cl.getClassFile().getSourceFile();
    int index = new String(bc).indexOf(s);
    for(int i = 0; i < s.length(); i++)  //KILL SOURCEFILE (c) moofMonkey
        bc[index + i] = '-';

    DataOutputStream out = cl.makeFileOutput(directoryName);

    out.write(bc);

    out.flush();
    out.close();
}

BUT... But. If I calling analog of writeFile() - cl.writeFile() - all works!

I can do this:

1. Save File
2. Read bytes from him
3. Dp what I need
4. Save File

Answer 1

Having a look into the javadoc of CtClass reveals

Once this method is called, further modifications are not possible any more.

If you change the call order to

String s = cl.getClassFile().getSourceFile();
byte[] bc = cl.toBytecode();

you can call toBytecode.