Updated ARM Spec

[Mandy Chung]

Hi Remi,

Rémi Forax wrote:
> Le 13/08/2010 05:28, Neal Gafter a écrit :
>> When a stack overflow exception suppresses another exception, I assume
>> it's suppressed exception list will be set.  But since there is only
>> one such exception allocated by the VM, this will overwrite any data
>> previously stored there.  Will the VM be modified to comply with this
>> specification by allocating a new stack-overflow exception each time?
>> Same question for out-of-memory error.
>>    
>
> This problem already exists with jdk6.
> This code change the stack trace of permanently allocated 
> OutOfMerroryError.
>
>   public static void main(String[] args) {
>     Error last = null;
>
>     for(int i=0; i<100; i++) {
>       try {
>         Object o = new int[Integer.MAX_VALUE];
>       } catch (Error e) {
>         StackTraceElement[] stackTrace = e.getStackTrace();
>         if (stackTrace != null && stackTrace.length>0 && 
> stackTrace[0].getLineNumber() == -3) {
>           e.printStackTrace();
>           return;
>         }
>
>         if (last == e) {
>           StackTraceElement element = new StackTraceElement("Foo", 
> "foo", null, -3);
>           e.setStackTrace(new StackTraceElement[]{element});
>         }
>         last = e;
>       }
>     }
>   }
>
>
>
> To avoid that the VM has to clear the stacktrace when using the 
> default error:
> in universe.cpp, in Universe::gen_out_of_memory_error:
>
>   if (next < 0) {
>       // all preallocated errors have been used.
>       // return default
> +    java_lang_Throwable::clear_stacktrace(default_err);
>       return default_err;
>     } else {
>
>

This is indeed a bug and I file 6978918 to fix it.   We should clear the 
stacktrace and the suppressed exception fields as you suggest. 

Thanks
Mandy

> And we should do the same for the field suppressed exceptions.
>
> Rémi
>