public String getSourcePositionFromStack(Context cx, int[] linep)
    {
        CallFrame frame = (CallFrame)cx.lastInterpreterFrame;
        InterpreterData idata = frame.idata;
        if (frame.pcSourceLineStart >= 0) {
            linep[0] = getIndex(idata.itsICode, frame.pcSourceLineStart);
        } else {
            linep[0] = 0;
        }
        return idata.itsSourceFile;
    }