[Bug libgcj/26858] NullPointerException not generated for large classes...

[ddaney at avtrex dot com]

------- Comment #4 from ddaney at avtrex dot com  2006-03-27 18:42 -------
Subject: Re:  NullPointerException not generated for large
 classes...

mckinlay at redhat dot com wrote:
> ------- Comment #3 from mckinlay at redhat dot com  2006-03-27 18:28 -------
> GCJ could be made to generate explicit null checks when large offsets are used.
> It is probably relatively rare to have a normal object that is larger than a
> page, so performance for most apps shouldn't be effected.
> 
> Note that array accesses should not need this as the "length" field will be
> dereferenced first, triggering NullPointerException, assuming bounds checks are
> used. I would also expect Strings should not have a problem.
> 
> Do we know who's heap exactly is mapped at such a low address? If its mapped by
> Java/Boehm GC, then we can probably just fix the GC to not map things at such
> low addresses (or to insert guard pages there instead).

It is libgcj's (Boehm GC) heap in my tests that is at 0x1000.

This message:

http://gcc.gnu.org/ml/java/2006-03/msg00206.html

Has more thoughts on the subject.

David Daney.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26858