Request for sponsor: JDK-8221430: StringBuffer(CharSequence) constructor truncates when -XX:-CompactStrings specified

[Roger Riggs]

Hi Andrew,

Sorry to be late to the review.

For symmetry with the constructors StringBuffer(String), and 
StringBuilder(String)
the determine the coder based on the input argument, I would recommend
using the getCharSequenceCoder added in the -01 webrev and calling
it from the StringBuffer(CharSeq...), and StringBuilder(CharSeq...) 
constructors.

It would be symmetric with the getCoder() method (line 1635)
and select the appropriate coder base on the input value (if known.)

Thanks, Roger



On 03/26/2019 10:57 AM, Andrew Leonard wrote:
> Hi Ivan,
> Yes, i'm happy with that, as you say the simple constructor change fixes
> the immediate issue, but not necessarily the extended issue of a
> non-compactable CharSequence in COMPACT_STRINGS mode, but that's probably
> an enhanced issue to cover in a separate bug...
> I've created a new webrev.02 with just the constructor change and the
> testcase:
> http://cr.openjdk.java.net/~aleonard/8221430/webrev.02/
>
> Thanks
> Andrew
>
> Andrew Leonard
> Java Runtimes Development
> IBM Hursley
> IBM United Kingdom Ltd
> Phone internal: 245913, external: 01962 815913
> internet email: andrew_m_leonard at uk.ibm.com
>
>
>
>
> From:   Ivan Gerasimov <ivan.gerasimov at oracle.com>
> To:     Andrew Leonard <andrew_m_leonard at uk.ibm.com>
> Cc:     core-libs-dev at openjdk.java.net
> Date:   26/03/2019 01:18
> Subject:        Re: Request for sponsor: JDK-8221430:
> StringBuffer(CharSequence) constructor truncates when -XX:-CompactStrings
> specified
>
>
>
> Thanks Andrew!
> Introducing getCharSequenceCoder() is actually an enhancement, which may
> improve pre-allocation in certain cases.
> It's not actually required to restore correctness of StringBuilder/Buffer
> constructors.
> I recommend to separate it from this bug fix, so it can be discussed
> separately, and determined if this is the best approach to this
> enhancement.
> If you agree, I can adjust your latest patch accordingly, run it through
> the Mach5 test systems and push it on your behalf.
> With kind regards,
> Ivan
>
> On 3/25/19 5:00 PM, Andrew Leonard wrote:
> Hi Ivan,
> Here is my updated webrev:
> http://cr.openjdk.java.net/~aleonard/8221430/webrev.01/
>
> Thanks
> Andrew
>
> Andrew Leonard
> Java Runtimes Development
> IBM Hursley
> IBM United Kingdom Ltd
> Phone internal: 245913, external: 01962 815913
> internet email: andrew_m_leonard at uk.ibm.com
>
>
>
>
> From:        Ivan Gerasimov <ivan.gerasimov at oracle.com>
> To:        Andrew Leonard <andrew_m_leonard at uk.ibm.com>
> Cc:        core-libs-dev at openjdk.java.net
> Date:        25/03/2019 22:55
> Subject:        Re: Request for sponsor: JDK-8221430:
> StringBuffer(CharSequence) constructor truncates when -XX:-CompactStrings
> specified
>
>
>
> I was thinking of organizing code similar to what is done in
> AbstractStringBuilder(int):
>
> if (COMPACT_STRINGS && coderHint == LATIN1) {
>      value = new byte[capacity];
>      coder = LATIN1;
> } else {
>      value = StringUTF16.newBytesFor(capacity);
>      coder = UTF16;
> }
>
> With kind regards,
> Ivan
>
> On 3/25/19 3:45 PM, Andrew Leonard wrote:
> Hi Ivan,
> I think I see what you're saying, you mean we also need to correct this
> line in AbstractStringBuilder
> constructor:
> value = (coder == LATIN1)
>                 ? new byte[capacity] : StringUTF16.newBytesFor(capacity);
> to be maybe:
> value = (COMPACT_STRINGS && coder == LATIN1)
>                 ? new byte[capacity] : StringUTF16.newBytesFor(capacity);
>
> The passed in coder stills need to be correct, since with COMPACT_STRINGS
> a string could be UTF16 if
> it cannot be compacted, so it's more than just a hint isn't it?
>
> Thanks
> Andrew
>
> Andrew Leonard
> Java Runtimes Development
> IBM Hursley
> IBM United Kingdom Ltd
> Phone internal: 245913, external: 01962 815913
> internet email: andrew_m_leonard at uk.ibm.com
>
>
>
>
> From:        Ivan Gerasimov <ivan.gerasimov at oracle.com>
> To:        Andrew Leonard <andrew_m_leonard at uk.ibm.com>,
> core-libs-dev at openjdk.java.net
> Date:        25/03/2019 22:20
> Subject:        Re: Request for sponsor: JDK-8221430:
> StringBuffer(CharSequence) constructor truncates when -XX:-CompactStrings
> specified
>
>
>
> Hi Andrew!
>
> Thanks for finding this bug!
>
> Your fix solves the problem.
>
> However, I think the main issue is that the constructor
> AbstractStringBuilder(byte,int,int) is now broken:  as you discovered,
> it allows to create a string buffer with the coder LATIN1 when
> COMPACT_STRINGS is false.
>
> Wouldn't it make sense to rename the argument of the constructor to,
> say, coderHint, and then either use it as the coder if
> COMPACT_STRINGS==true, or discard it otherwise.
>
> What do you think?
>
> With kind regards,
> Ivan
>
> On 3/25/19 12:45 PM, Andrew Leonard wrote:
>> Hi,
>> Please can I request a sponsor for this fix to a JDK-13 regression?
>>
>> Patch with jtreg testcase here:
>> http://cr.openjdk.java.net/~aleonard/8221430/webrev.00/
>>
>> bug: https://bugs.openjdk.java.net/browse/JDK-8221430
>>
>> Many thanks
>> Andrew
>>
>> Andrew Leonard
>> Java Runtimes Development
>> IBM Hursley
>> IBM United Kingdom Ltd
>> Phone internal: 245913, external: 01962 815913
>> internet email: andrew_m_leonard at uk.ibm.com
>>
>> Unless stated otherwise above:
>> IBM United Kingdom Limited - Registered in England and Wales with number
>> 741598.
>> Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
> 3AU