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From: "ddaney at avtrex dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libgcj/26858] NullPointerException not generated for large classes...
Date: Mon, 27 Mar 2006 18:42:00 -0000	[thread overview]
Message-ID: <20060327184205.26630.qmail@sourceware.org> (raw)
In-Reply-To: <bug-26858-7151@http.gcc.gnu.org/bugzilla/>



------- 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.


-- 


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


  parent reply	other threads:[~2006-03-27 18:42 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-03-24 23:41 [Bug libgcj/26858] New: " daney at gcc dot gnu dot org
2006-03-25  1:56 ` [Bug libgcj/26858] " daney at gcc dot gnu dot org
2006-03-25  1:57 ` daney at gcc dot gnu dot org
2006-03-27 18:28 ` mckinlay at redhat dot com
2006-03-27 18:42 ` ddaney at avtrex dot com [this message]
2006-03-30 14:24 ` aph at gcc dot gnu dot org
2006-03-30 14:24 ` aph at gcc dot gnu dot org
2006-03-31 11:43 ` aph at gcc dot gnu dot org
2006-03-31 13:05 ` aph at gcc dot gnu dot org
2006-04-03 14:32 ` aph at gcc dot gnu dot org
2006-04-03 15:22 ` aph at gcc dot gnu dot org
2006-04-18 16:53 ` aph at gcc dot gnu dot org
2006-04-30  4:24 ` pinskia at gcc dot gnu dot org
2006-05-04 13:54 ` aph at gcc dot gnu dot org

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