Mapping to source code

Some notes on mapping back to source when analyzing bytecode. This does not include the CAst functionality.

This page is incomplete.

Getting the source file name

Note that IClass has a method getSourceFileName(). The ClassLoaderImpl attempts to set up a mapping between IClasses and source files during class loading. After loading all classes, the class loader goes back and looks at each .java file in the scope, and maps it to a loaded IClass. So, in order to use getSourceFileName(), be sure to include the source files in the analysis scope.

Mapping value numbers back to local names

If the information is available, you can retrieve it via IR.getLocalNames(). Note that not every value number corresponds to a local variable in Java source code. Some value numbers may represent multiple local variables, as a result of copy propagation during IR construction.

From IR instruction to bytecode index / source line number

Given the index i of some SSAInstruction in an IR ir produced from bytecode, you can get the corresponding bytecode index and source line number as follows:

    IBytecodeMethod method = (IBytecodeMethod)ir.getMethod();
    int bytecodeIndex = method.getBytecodeIndex(i);
    int sourceLineNum = method.getLineNumber(bytecodeIndex);

Note that source line information may not always be available.

From Slices to source line numbers

Given a Statement that came from a Java bytecode file (via Shrike), you can get the line number in the original source with the following:

if (s.getKind() == Statement.Kind.NORMAL) { // ignore special kinds of statements
  int bcIndex, instructionIndex = ((NormalStatement) s).getInstructionIndex();
  try {
    bcIndex = ((ShrikeBTMethod) s.getNode().getMethod()).getBytecodeIndex(instructionIndex);
    try {
      int src_line_number = s.getNode().getMethod().getLineNumber(bcIndex);
      System.err.println ( "Source line number = " + src_line_number );
    } catch (Exception e) {
      System.err.println("Bytecode index no good");
      System.err.println(e.getMessage());
    }
  } catch (Exception e ) {
    System.err.println("it's probably not a BT method (e.g. it's a fakeroot method)");
    System.err.println(e.getMessage());
  }
}

For Statements that came from a Java source file thru cast, there is no bytecode index, so (despite what the javadoc may lead you to believe) the parameter to getLineNumber() is simply an instruction index:

if (s.getKind() == Statement.Kind.NORMAL) {
  int instructionIndex = ((NormalStatement) s).getInstructionIndex();
  int lineNum = ((ConcreteJavaMethod) s.getNode().getMethod()).getLineNumber(instructionIndex);
  System.out.println("Source line number = " + lineNum );
}

This is useful when investigating the output of slicing.

Getting the .jar file for an IClass

If you have an IClass klass representing a .class file inside a .jar, you can do the following to figure out the .jar file name:

 ShrikeClass shrikeKlass = (ShrikeClass) klass;
 JarFileEntry moduleEntry = (JarFileEntry) shrikeKlass.getModuleEntry();
 String jarFile = moduleEntry.getJarFile();

Note that the casts may fail if it's not a .class file inside a .jar.