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

Tue Mar 26 19:37:02 UTC 2019

So my creation of getCharSequenceCoder() was in trying to use the same 
method as the StringBuffer(String) constructors, ie.String.coder(), 
however with the StringBuffer(CharSequence,..) constructor the seq can be 
a String or a StringBuilder or a StringBuffer, hence I created the static 
getCharSequenceCoder() which switched on the sequence type to obtain the 
coder...
Isn't that in keeping with the (String) constructor? i'm not sure how else 
we can determine the coder from a CharSequence ? unless we change the 
constructor to delegate to the caller to pass in the coder?

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:   Roger Riggs <Roger.Riggs at oracle.com>
To:     Andrew Leonard <andrew_m_leonard at uk.ibm.com>
Cc:     core-libs-dev at openjdk.java.net, Ivan Gerasimov 
<ivan.gerasimov at oracle.com>
Date:   26/03/2019 19:15
Subject:        Re: Request for sponsor: JDK-8221430: 
StringBuffer(CharSequence) constructor truncates when -XX:-CompactStrings 
specified

Hi,

We've got the subject open and its fresh, there's no need for a separate 
review cycle.

The first fix (-01) does not seem to be consistent with the original 
design
and handling of the coder.  The StringBuilder(String) and 
StringBuffer(String)
constructors are the pattern that should be followed for determining
the coder for the new instance.

Checking for COMPACT_STRING in two places (the AbstractStringBuilder and 
the sub classes) is unnecessary and distributes the information about the 
correct coder across two classes where determining what it should be 
in the subclass has more complete  information and can correctly determine 

the coder once.

We can likely find a reviewer to be a tie-breaker if Ivan sees it as 
desirable.

Thanks, Roger

On 03/26/2019 02:38 PM, Andrew Leonard wrote:
Sorry chaps, I think my brain is getting confused!, I think we have 
conflicting reviews here? 

Roger, I added the getCharSequenceCoder() to AbstractStringBuilder so it 
was only defined in one place.. 
I agree with this being called in StringBuffer/Builder then we don't need 
the change to AbstractStringBuild() constuctor, however Ivan wants 
getCharSequenceCoder() that done as a separate "bug". 

So I think it comes down to do we do this as 2 "bugs" or 1 ? 

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:        Roger Riggs <Roger.Riggs at oracle.com> 
To:        Andrew Leonard <andrew_m_leonard at uk.ibm.com>, Ivan Gerasimov 
<ivan.gerasimov at oracle.com> 
Cc:        core-libs-dev at openjdk.java.net 
Date:        26/03/2019 18:19 
Subject:        Re: Request for sponsor: JDK-8221430: 
StringBuffer(CharSequence) constructor truncates when -XX:-CompactStrings 
specified 

Hi Andrew,

You are going to have to change the same code twice
because the changes should be the StringBuffer and StringBuilder
constructors and would remove the code that is added to
the AbstractStringBuilder constructor.  That's a waste of review cycles.

On 03/26/2019 11:45 AM, Andrew Leonard wrote: 
Hi Roger, 
No worries, the more the merrier! 
So that was one of my reasoning for adding getCharSequenceCode() was, I 
think what you're suggesting is my webrev.01, 
http://cr.openjdk.java.net/~aleonard/8221430/webrev.01/ 
Ivan's view is that behaviour was an extended issue, which it is, but I 
thought it was nice to add.. 

Which patch do we favour? webrev-01 or -02 ? 

Neither, there should be no change to the AbstractStringBuilder 
constructor
and the change should be done in the subclass constructors.

Roger

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:        Roger Riggs <Roger.Riggs at oracle.com> 
To:        core-libs-dev at openjdk.java.net 
Date:        26/03/2019 15:24 
Subject:        Re: Request for sponsor: JDK-8221430: 
StringBuffer(CharSequence) constructor truncates when -XX:-CompactStrings 
specified 
Sent by:        "core-libs-dev" <core-libs-dev-bounces at openjdk.java.net> 

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

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 