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&nbsp;my name has
>> >>  > been listed on&nbsp;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
>> >>  >  >
>> >>  >  >
>> >>  >  >
>> >>  >  >
>> >>  >  >
>> >>  >  > 
>> ------------------&nbsp;原始邮件&nbsp;------------------
>> >>  >  > 发件人:&nbsp;"Bug Report
>> >>  > 
>> Notification"<Bug-Report-Daemon_WW at ORACLE.COM&gt;;
>> >>  >  > 发送时间:&nbsp;2019年9月5日(星期四) 
>> 凌晨3:33
>> >>  >  > 
>> 收件人:&nbsp;"未来阳光"<2217232293 at qq.com&gt;;
>> >>  >  >
>> >>  >  > 主题:&nbsp;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
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>> >>  > this issue has a significant impact on your 
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>> >>  > consider using one of the technical support 
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>> >>  > Oracle Support.
>> >>  >  
>> >                               
>> Regards,
>> >>  >  
>> >                                       
>> Java Developer Support
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>> >>  >  >
>> >>  >  >
>> >>  >  >
>> >>  >  >
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