Request for sponsor: JDK-8221430: StringBuffer(CharSequence) constructor truncates when -XX:-CompactStrings specified
Andrew Leonard
andrew_m_leonard at uk.ibm.com
Thu Mar 28 16:13:41 UTC 2019
Roger, Ivan, thanks for your help discussing this issue. Fyi, I am off on
leave for the next week, so I +1 Ivan's last webrev if that's the way you
decide to go..
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: Ivan Gerasimov <ivan.gerasimov at oracle.com>, Andrew Leonard
<andrew_m_leonard at uk.ibm.com>
Cc: core-libs-dev at openjdk.java.net
Date: 27/03/2019 13:39
Subject: Re: Request for sponsor: JDK-8221430:
StringBuffer(CharSequence) constructor truncates when -XX:-CompactStrings
specified
Hi Ivan,
On 03/26/2019 07:30 PM, Ivan Gerasimov wrote:
The main source of confusion here seems to be due to that the coder is
passed in as an argument, so it either needs to be trusted or has to be
verified in the constructor.
The design for coder is that it *is* trusted in all
internal/implementation APIs.
Subsequent changes should not weaken this invariant, it will cause doubt
in the code and cast doubt on all of the performance work that has
been done to optimize its use.
So, let's instead introduce AbstractStringBuilder(CharSequence) and make
it do all manipulations.
http://cr.openjdk.java.net/~igerasim/8221430/01/webrev/
Note that the common case of StringBuilder(String) already gets
intrinsified by hotspot.
What do you think?
This looks good, the logic is in one place.
Since StringBuilder(String) is an intrinsic, my doubt about a slight
performance
impact is unwarranted in that specific case.
Are there any StringBuffer/Builder jmh tests than be easily rerun to
compare?
Thanks, Roger
With kind regards,
Ivan
On 3/26/19 1:04 PM, Ivan Gerasimov wrote:
>From the design point of view, I believe it is better to have the
constructor AbstractStringBuilder(int, int, int) to check if the coder
argument makes sense with respect to the value of COMPACT_STRING, so it
won't be possible to create a StringBuilder with the coder==LATIN1, when
it is not supported.
For calculating the coderHint then, it is not necessary to check
COMPACT_STRING: If the CharSequence argument is in fact String or
AbstractStringBuilder, the coder is known, otherwise LATIN1 can be passed
in as a hint (for an arbitrary CharSequence it is not 100% accurate
anyway).
The constructor AbstractStringBuilder(int, int, int) will then either use
the provided coder, or adjust it if necessary.
Will we agree on something like following?
http://cr.openjdk.java.net/~igerasim/8221430/00/webrev/
With kind regards,
Ivan
On 3/26/19 12:14 PM, Roger Riggs wrote:
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/_
<http://cr.openjdk.java.net/%7Ealeonard/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_
<mailto:andrew_m_leonard at uk.ibm.com>
From: Roger Riggs _<Roger.Riggs at oracle.com>_
<mailto:Roger.Riggs at oracle.com>
To: _core-libs-dev at openjdk.java.net_
<mailto: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>_
<mailto: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/_
<http://cr.openjdk.java.net/%7Ealeonard/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_
<mailto:andrew_m_leonard at uk.ibm.com>
>
>
>
>
> From: Ivan Gerasimov _<ivan.gerasimov at oracle.com>_
<mailto:ivan.gerasimov at oracle.com>
> To: Andrew Leonard _<andrew_m_leonard at uk.ibm.com>_
<mailto:andrew_m_leonard at uk.ibm.com>
> Cc: _core-libs-dev at openjdk.java.net_
<mailto: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/_
<http://cr.openjdk.java.net/%7Ealeonard/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_
<mailto:andrew_m_leonard at uk.ibm.com>
>
>
>
>
> From: Ivan Gerasimov _<ivan.gerasimov at oracle.com>_
<mailto:ivan.gerasimov at oracle.com>
> To: Andrew Leonard _<andrew_m_leonard at uk.ibm.com>_
<mailto:andrew_m_leonard at uk.ibm.com>
> Cc: _core-libs-dev at openjdk.java.net_
<mailto: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_
<mailto:andrew_m_leonard at uk.ibm.com>
>
>
>
>
> From: Ivan Gerasimov _<ivan.gerasimov at oracle.com>_
<mailto:ivan.gerasimov at oracle.com>
> To: Andrew Leonard _<andrew_m_leonard at uk.ibm.com>_
<mailto:andrew_m_leonard at uk.ibm.com>,
> _core-libs-dev at openjdk.java.net_ <mailto: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/_
<http://cr.openjdk.java.net/%7Ealeonard/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_
<mailto: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
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
More information about the core-libs-dev
mailing list