Updated ARM Spec

[Rémi Forax]

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 {


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

Rémi