RFR: 8061244 Use of stack-less ClassNotFoundException thrown from (URL)ClassLoader.findClass()

[Peter Levart]

On 10/23/2014 12:42 AM, Mandy Chung wrote:
> Talking about exceptions and fillInStackTrace, it's known to be 
> significant cost.  It'd be interesting to have the VM flag that can 
> measure the time it spends in filling in the backtrace of each 
> exception type (and perhaps the mean and max stack depth) that will 
> give a better idea of the performance distribution.   In addition, 
> doPrivileged wraps checked exception with PrivilegedActionException 
> that essentially has the same stack trace and it doubles the cost even 
> in the absence of security manager.   I have exchanged some mail with 
> the security team to see if this is a low-hanging fruit to improve the 
> performance.
>
> Mandy 

For such cases, where the purpose is to just change the type of 
exception, a Throwable constructor (+ Exception, RuntimeException and 
Error constructors chained to it) like the following would be helpful:

     protected Throwable(Throwable cause, boolean poseAsCause) {
         if (poseAsCause && cause != null) {
             backtrace = cause.backtrace;
             stackTrace = cause.stackTrace;
             suppressedExceptions = cause.suppressedExceptions;
             detailMessage = "Posing as: " + cause;
         } else {
             fillInStackTrace();
             detailMessage = (cause==null ? null : cause.toString());
         }
         this.cause = cause;
     }


Such exceptions would inherit the stack-trace from their cause, 
eliminating the need to construct their own stack-trace that would be 
basically a suffix of the stack-trace of the cause.


Regards, Peter