Hi 未来阳光,
As David has pointed out, your proposed fix would break binary and
source compatibility of BitSet.size() method, so it is not acceptable.
BitSet API allows addressing individual bits using non-negative 'int'
typed indexes (analogous to indexes of Java arrays). The range of
indexes is: 0 ... 2^31 - 1 (0 ... Integer.MAX_VALUE). The maximum "size"
of BitSet is therefore 2^31. Unfortunately, this value can't be
"corectly" represented with signed 32 bit integer (int). Only in this
corner case, - 2^31 (Integer.MIN_VALUE) is the interpreted value
returned from size(). If one would interpret it as unsigned 32 bit
integer value, it is entirely correct. For example, this holds:
Integer.toUnsignedLong(new BitSet(Integer.MAX_VALUE).size()) == 1L << 31
It is also always true what javadoc says about size(): "The maximum
element in the set is the size - 1st element"
The following holds also for this corner case:
new BitSet(Integer.MAX_VALUE).size() - 1 == Integer.MAX_VALUE;
So perhaps, the fix could be just to describe this corner case in the
spec. And perhaps, to support the following use case in the corner case:
BitSet set1 = ...
...
BitSet set2 = new BitSet(set1.size());
... by modifying the BitSet constructor to accept the Integer.MIN_VALUE
in addition to all the non-negative values as the 'nbits' parameter.
What do you think?
Regards, Peter
On 9/5/19 8:31 AM, David Holmes wrote:
Hi,
On 5/09/2019 4:11 pm, 未来阳光 wrote:
Thanks very much.
*BUG-LINK:* https://bugs.openjdk.java.net/browse/JDK-8230557
*Describe: *
the return type of the method BitSet#size is int, so the method may
return a negative value in some case, for example, will return
-2147483648.
```
BitSet bitSet = new BitSet(Integer.MAX_VALUE);
for (int i = 0; i < Integer.MAX_VALUE - 1000; i++) {
bitSet.set(i);
}
System.out.println(bitSet.size());
```
EXPECTED: 2147483648, but ACTUAL: -2147483648.
*FIX*
I have put the patch in the attachment of the mail.
In case the attachment got stripped form the mailing list the proposed
fix is:
- public int size() {
- return words.length * BITS_PER_WORD;
+ public long size() {
+ return (long) words.length * BITS_PER_WORD;
Unfortunately this simple fix it not possible. You can't just change
the return type of the method to long as that is a source-incompatible
change and would not be approved [1]. Instead the return value should
be capped at Integer.MAX_VALUE - but I'll leave that for someone from
core-libs team to pick up. Also look at the evaluation in:
https://bugs.openjdk.java.net/browse/JDK-4213570
Cheers,
David
[1] https://wiki.openjdk.java.net/display/csr/CSR+FAQs
------------------ 原始邮件 ------------------
*发件人:* "David Holmes"<david.hol...@oracle.com>;
*发送时间:* 2019年9月5日(星期四) 下午2:00
*收件人:* "未来阳光"<2217232...@qq.com>;"core-libs-dev"<core-libs-
d...@openjdk.java.net>;
*主题:* Re: 回复： what to do next to fix JDK-8230557. thanks
On 5/09/2019 3:46 pm, 未来阳光 wrote:
>
> hi, developers.
>
> Can someone help me? thanks very much !!
Help you how exactly. As I stated your are up to step 2 of the how to
contribute process. If you have a suggested fix for the bug then put
that in an email as described.
Thanks,
David
>
> ------------------ 原始邮件 ------------------
> *发件人:* "David Holmes"<david.hol...@oracle.com>;
> *发送时间:* 2019年9月5日(星期四) 中午1:44
> *收件人:* "未来阳光"<2217232...@qq.com>;"core-libs-dev"<core-libs-
> d...@openjdk.java.net>;
> *主题:* Re: what to do next to fix JDK-8230557. thanks
>
> On 5/09/2019 3:35 pm, 未来阳光 wrote:
> > Hi, leaders.
>
> Hi,
>
> No "leaders" here only developers :)
>
> >
> > A few days ago, I report a bug in core lib[1]. According to the
> contribute document[2], I had send oca to oracle and my name has
> been listed on oca[3].
>
> Welcome aboard!
>
> > But I still can't push my changes to jdk, can someone tell me
how to
> do next? thanks very match!!
>
> You can't push anything until you become a Committer and before
that you
> have to become an Author. The steps for contributing are outlined
here:
>
> http://openjdk.java.net/contribute/
>
> and you would seem to be up to step 2. :)
>
> Cheers,
> David
>
> >
> >
> >
> >
> > [1]https://bugs.openjdk.java.net/browse/JDK-8230557
> >
> > [2]http://openjdk.java.net/contribute/
> > [3]https://www.oracle.com/technetwork/community/oca-486395.html
> >
> >
> >
> >
> >
> > ------------------ 原始邮件 ------------------
> > 发件人: "Bug Report
> Notification"<bug-report-daemon...@oracle.com>;
> > 发送时间: 2019年9月5日(星期四) 凌晨3:33
> > 收件人: "未来阳光"<2217232...@qq.com>;
> >
> > 主题: Update Notification: Bug Report - JDK-8230557
> >
> >
> >
> >
> [This is an automated response. Please
do not
> reply.]
> > Dear Java Developer,
> > We have finished evaluating your report and have assigned it a Bug
> ID: JDK-8230557. The issue is visible on bugs.java.com at the
following
> url JDK-8230557.
> > To provide more information about this issue,
> click here.
> > We work to resolve the issues that are
submitted to
> us according to their impact to the community as a whole, and make no
> promises as to the time or release in which a bug might be fixed. If
> this issue has a significant impact on your project you may want to
> consider using one of the technical support offerings available at
> Oracle Support.
> > Regards,
> > Java Developer Support
> >
> >
> >
> >
> >
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