Re: Reply： what to do next to fix JDK-8230557. thanks
Peter Levart
peter.levart at gmail.com
Thu Sep 5 14:24:55 UTC 2019
Hi Ivan,
On 9/5/19 11:22 AM, Ivan Gerasimov wrote:
> Hello!
>
> BitSet is known to be flawed in many ways: its size(), length(),
> cardinality() and nextClearBit() can return meaningless negative values.
>
> I was thinking about disallowing setting any index greater than
> (Integer.MAX_VALUE - 63), for example by throwing OutOfMemoryError.
An index of Integer.MAX_VALUE - 64 would be the greatest index then, an
index of Integer.MAX_VALUE - 63 already needs an array of longs of
length 2^25 which results in BitSet size() of 2^31 ...
>
> We could do it without changing the specification.
The calls to: new BitSet(Integer.MAX_VALUE - 63) ... new
BitSet(Integer.MAX_VALUE) would also have to throw then.
BitSet.valueOf(...) methods don't even check the passed in arguments
lengths, so size() can really return a meaningless negative or positive
number. They all would have to throw if the passed-in length of
array/buffer is too large.
So would you not specify when those methods throw?
Regards, Peter
>
> With kind regards,
>
> Ivan
>
>
> On 9/5/19 1:16 AM, 未来阳光 wrote:
>> Hi, Peter.
>>
>>
>> I understand your point, but I think it's unreasonable for the reason
>> that source code compatibility problem, it's really a bug.
>>
>>
>> User can't understand why the size method return a negative number.
>>
>>
>>
>>
>>
>>
>> Best, lamber-ken
>>
>>
>>
>>
>> ------------------ 原始邮件 ------------------
>> 发件人: "Peter Levart"<peter.levart at gmail.com>;
>> 发送时间: 2019年9月5日(星期四) 下午3:51
>> 收件人: "未来阳光"<2217232293 at qq.com>;"core-libs-dev"<core-libs-dev at openjdk.java.net>;
>>
>> 抄送: "David Holmes"<david.holmes at oracle.com>;
>> 主题: Re: 回复： 回复： what to do next to fix JDK-8230557. thanks
>>
>>
>>
>> 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.holmes at 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"<2217232293 at qq.com>;"core-libs-dev"<core-libs-
>> >> dev at 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.holmes at 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"<2217232293 at qq.com>;"core-libs-dev"<core-libs-
>> >> > dev at 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_WW at 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"<2217232293 at 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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