[OpenJDK 2D-Dev] [12] JDK-8212202: NPE in the print tests after JDK-8153732
Prasanta Sadhukhan
prasanta.sadhukhan at oracle.com
Mon Feb 18 12:08:41 UTC 2019
Hi Shashi,
I think if the overhead can be fixed with a small change, we should do
it as I think we need to keep the code optimized with whatever code is
present now.
If in future, if somebody changes the function order, like
doCompare(prev..., curr..) to doCompare(curr..., prev..) [what you are
trying to imply]
then it needs to be done with proper reasoning (which I am not sure what
it can be and then we can do these checks). That's my take. It other
reviewers feel the present changes are ok, you can commit the changes
with their approval.
Regards
Prasanta
On 18-Feb-19 12:26 PM, Shashidhara Veerabhadraiah wrote:
>
> Hi Prasanta, I hope I have answered your questions satisfactorily.
> Please let me know if you have any more questions.
>
> Thanks and regards,
>
> Shashi
>
> *From:*Shashidhara Veerabhadraiah
> *Sent:* Friday, February 15, 2019 12:37 PM
> *To:* Prasanta Sadhukhan <prasanta.sadhukhan at oracle.com>; Philip Race
> <philip.race at oracle.com>
> *Cc:* 2d-dev at openjdk.java.net
> *Subject:* RE: [OpenJDK 2D-Dev] [12] JDK-8212202: NPE in the print
> tests after JDK-8153732
>
> Hi Prasanta, The parameters for the function does not tells the order
> and is not implied by the way function definition is and more over
> this function is called in an interval of minimum refresh time(4
> mins). Rather than adding overhead of confusion since it is not
> implied by the function I think it is safe to keep it that way.
> Depending on reviewer’s comments is also not the right way to depend
> on. The current definition avoids that but with a small overhead and I
> think is not too much of a burden to bear.
>
> Thanks and regards,
>
> Shashi
>
> *From:*Prasanta Sadhukhan
> *Sent:* Friday, February 15, 2019 12:28 PM
> *To:* Shashidhara Veerabhadraiah
> <shashidhara.veerabhadraiah at oracle.com
> <mailto:shashidhara.veerabhadraiah at oracle.com>>; Philip Race
> <philip.race at oracle.com <mailto:philip.race at oracle.com>>
> *Cc:* 2d-dev at openjdk.java.net <mailto:2d-dev at openjdk.java.net>
> *Subject:* Re: [OpenJDK 2D-Dev] [12] JDK-8212202: NPE in the print
> tests after JDK-8153732
>
> Hi Shashi,
>
> In this case, we know doCompare() is called from one location only
> [and also is not a public method to be called by user] and the check I
> mentioned is redundant. It's in while(true) loop so any optimzation we
> can do to avoid unnecessary checks will be good in my opinion.
>
> If someone changed the doCompare() call without seeing the implication
> or giving thought, then he has to face the repurcussions, but I guess
> reviewers would be able to catch that beforehand.
>
> Regards
>
> Prasanta
>
> On 15-Feb-19 12:17 PM, Shashidhara Veerabhadraiah wrote:
>
> Hi Prasanta, doCompare(str1, str2) is a different function and one
> should not define a function based on how it is going to be
> called!! What if someone changed the caller to this:
> doCompare(currentRemotePrinters, prevRemotePrinters). There is no
> restriction if one calls like this. Here the function is taking 2
> strings and it does not say which one should be passed at what
> position. Probably if the function takes different parameters then
> it sets an automatic rule on which parameter needs to be passed at
> which position but otherwise function definition should take care
> this.
>
> Hope you agree with me.
>
> Thanks and regards,
>
> Shashi
>
> *From:*Prasanta Sadhukhan
> *Sent:* Friday, February 15, 2019 12:11 PM
> *To:* Phil Race <philip.race at oracle.com>
> <mailto:philip.race at oracle.com>; Shashidhara Veerabhadraiah
> <shashidhara.veerabhadraiah at oracle.com>
> <mailto:shashidhara.veerabhadraiah at oracle.com>
> *Cc:* 2d-dev at openjdk.java.net <mailto:2d-dev at openjdk.java.net>
> *Subject:* Re: [OpenJDK 2D-Dev] [12] JDK-8212202: NPE in the print
> tests after JDK-8153732
>
> Hi Shashi,
>
> I have one comment:
> doCompare(prevRemotePrinters, currentRemotePrinters) is only
> called from run() method when "prevRemotePrinters" is already
> checked to be not null [*if (prevRemotePrinters != null &&
> prevRemotePrinters.length > 0) ]*
> so I see no point in checking "str1" [which is prevRemotePrinters]
> to be null in doCompare(). I guess instead of
>
> *413 if (str1 == null && str2 == null) {*
>
> *414 return false;*
>
> *415 } else if (str1 == null || str2 == null) {*
>
> *416 return true;*
>
> *417 }*
>
> you can have
>
> if (str2 == null)
>
> return true;
>
> Regards
>
> Prasanta
>
> On 15-Feb-19 2:48 AM, Phil Race wrote:
>
> +1 .. remember to use the current bug synopsis in the push comment
>
> ie : "[Windows] Exception if no printers are installed."
>
> -phil.
>
> On 2/11/19 12:39 AM, Shashidhara Veerabhadraiah wrote:
>
> Hi Phil, Here is the new Webrev fixing those comments:
>
> http://cr.openjdk.java.net/~sveerabhadra/8212202/webrev.06/
> <http://cr.openjdk.java.net/%7Esveerabhadra/8212202/webrev.06/>
>
> Thanks and regards,
>
> Shashi
>
> *From:*Philip Race
> *Sent:* Saturday, February 9, 2019 2:25 AM
> *To:* Shashidhara Veerabhadraiah
> <shashidhara.veerabhadraiah at oracle.com>
> <mailto:shashidhara.veerabhadraiah at oracle.com>
> *Cc:* Prasanta Sadhukhan <prasanta.sadhukhan at oracle.com>
> <mailto:prasanta.sadhukhan at oracle.com>;
> 2d-dev at openjdk.java.net <mailto:2d-dev at openjdk.java.net>
> *Subject:* Re: [OpenJDK 2D-Dev] [12] JDK-8212202: NPE in
> the print tests after JDK-8153732
>
>
> 413 if (str1 == null && str2 == null) {
> 414 return false;
> 415 } else if ((str1 == null && str2 != null)
> || (str2 == null && str1 != null)) {
> 416 return true;
> 417 }
>
> When we get to 415 we already know at least one of str1 or
> str2 is non-null so 415 can just be
>
> } else if (str1 == null || str2 == null) {
>
> -phil.
>
> On 2/6/19, 12:31 AM, Shashidhara Veerabhadraiah wrote:
>
> Hi Phil, Here is the updated Webrev fixing those comments:
>
> http://cr.openjdk.java.net/~sveerabhadra/8212202/webrev.05/
> <http://cr.openjdk.java.net/%7Esveerabhadra/8212202/webrev.05/>
>
> Thanks and regards,
>
> Shashi
>
> *From:*Phil Race
> *Sent:* Thursday, January 31, 2019 4:36 AM
> *To:* Shashidhara Veerabhadraiah
> <shashidhara.veerabhadraiah at oracle.com>
> <mailto:shashidhara.veerabhadraiah at oracle.com>
> *Cc:* Prasanta Sadhukhan
> <prasanta.sadhukhan at oracle.com>
> <mailto:prasanta.sadhukhan at oracle.com>;
> 2d-dev at openjdk.java.net <mailto:2d-dev at openjdk.java.net>
> *Subject:* Re: [OpenJDK 2D-Dev] [12] JDK-8212202: NPE
> in the print tests after JDK-8153732
>
> Sorry .. this got lost ..
>
> I don't understand this line :
>
> 253 jobjectArray emptyArray =
> env->NewObjectArray(1, clazz, NULL);
>
>
> This is returning an array of length 1 and element 0
> is NULL.
> I think you want
>
> env->NewObjectArray(0, clazz, NULL);
>
> and I don't see why you need to create it there
>
> instead you can just have
>
> 304 if (nameArray != NULL) {
>
> 305 return nameArray;
>
> 306 } else {
>
> 307 return env->NewObjectArray(0, clazz, NULL);
>
> 308 }
>
> 449 if (prevRemotePrinters != null) {
>
> shouldn't this be
>
> 449 if (prevRemotePrinters != null &&
> prevRemotePrinters.length > 0) {
>
> ?
>
> -phil.
>
> On 12/10/18 10:19 PM, Shashidhara Veerabhadraiah wrote:
>
> Hi Phil, I have updated with small code updates:
>
> http://cr.openjdk.java.net/~sveerabhadra/8212202/webrev.04/
> <http://cr.openjdk.java.net/%7Esveerabhadra/8212202/webrev.04/>
>
> Thanks and regards,
>
> Shashi
>
> *From:*Shashidhara Veerabhadraiah
> *Sent:* Monday, December 10, 2018 3:19 PM
> *To:* Philip Race <philip.race at oracle.com>
> <mailto:philip.race at oracle.com>
> *Cc:* Prasanta Sadhukhan
> <prasanta.sadhukhan at oracle.com>
> <mailto:prasanta.sadhukhan at oracle.com>;
> 2d-dev at openjdk.java.net
> <mailto:2d-dev at openjdk.java.net>
> *Subject:* RE: [OpenJDK 2D-Dev] [12] JDK-8212202:
> NPE in the print tests after JDK-8153732
>
> Hi Phil, Please find the updated Webrev.
>
> http://cr.openjdk.java.net/~sveerabhadra/8212202/webrev.03/
> <http://cr.openjdk.java.net/%7Esveerabhadra/8212202/webrev.03/>
>
> Thanks and regards,
>
> Shashi
>
> *From:*Philip Race
> *Sent:* Friday, December 7, 2018 8:54 PM
> *To:* Shashidhara Veerabhadraiah
> <shashidhara.veerabhadraiah at oracle.com
> <mailto:shashidhara.veerabhadraiah at oracle.com>>
> *Cc:* Prasanta Sadhukhan
> <prasanta.sadhukhan at oracle.com
> <mailto:prasanta.sadhukhan at oracle.com>>;
> 2d-dev at openjdk.java.net
> <mailto:2d-dev at openjdk.java.net>
> *Subject:* Re: [OpenJDK 2D-Dev] [12] JDK-8212202:
> NPE in the print tests after JDK-8153732
>
> First off, I think the high order bit is that if a
> non-null array reference is returned there are NO
> null String entries in it. Whether a zero length
> or null array is returned when there are no printers
> is the less important issue.
>
> However an empty array also tells you there are no
> printers, and you are less likely to get an NPE
> from that.
> It is arguably easier for the caller, if they
> don't need the extra null check first.
> FWIW the javax.print public APIs return zero
> length arrays instead of null and applications
> seem to survive :-)
>
> I don't know what you mean by :
> > (And anyway we need to handle the first null
> string reference)?
>
> If you are referring to a small matter of coding
> in the native layer, then that is not an
> insurmountable problem.
>
> Basically if there are problems getting names or
> whatever in the native layer, handle it THERE,
> don't make
> everyone else have to deal with it.
>
> One caveat: JNI calls can theoretically fail due
> to OOME .. in such a case we are doomed and
> the main goal is to not crash in native and to
> obey all JNI rules. What is returned in that case
> can be a null array reference and an NPE in a
> Java-level user of that reference in such a case
> is not a big deal.
>
> -phil
>
> On 12/6/18, 8:10 PM, Shashidhara Veerabhadraiah
> wrote:
>
> Hi Phil, Is it advisable to return zero length
> array from native? The null return from native
> is telling the caller that there are no
> printers connected to the system. To tell this
> should we allocate a zero length array
> containing null back to the caller(And anyway
> we need to handle the first null string
> reference)? Handling the null on the caller
> isn’t an easier option?
>
> Thanks and regards,
>
> Shashi
>
> *From:*Phil Race
> *Sent:* Thursday, December 6, 2018 2:35 AM
> *To:* Shashidhara Veerabhadraiah
> <shashidhara.veerabhadraiah at oracle.com>
> <mailto:shashidhara.veerabhadraiah at oracle.com>;
> Prasanta Sadhukhan
> <prasanta.sadhukhan at oracle.com>
> <mailto:prasanta.sadhukhan at oracle.com>;
> 2d-dev at openjdk.java.net
> <mailto:2d-dev at openjdk.java.net>
> *Subject:* Re: [OpenJDK 2D-Dev] [12]
> JDK-8212202: NPE in the print tests after
> JDK-8153732
>
> But what I am saying is we should not return a
> NULL string reference
> from native. You are still allowing that and
> then having to handle
> it in Java code.
>
> And FWIW you can return a zero length array as
> well so there
> isn't a NULL array reference to deal with either.
>
> -phil.
>
> On 12/3/18 8:29 AM, Shashidhara Veerabhadraiah
> wrote:
>
> Hi Phil, There were 2 problems earlier.
> One is that, from the native it is
> possible to have no printers being
> associated with the system(causing to
> return null reference) and other problem
> in the implementation was that there may
> be no network printers and still return a
> valid array reference containing a null
> string. The first problem is fixed by
> handling null references returned from
> this function and other problem was that
> earlier there were different base
> conditions, for updating the reference and
> use it to create the printer name array
> which could produce a valid reference
> pointing to null string. Here is the
> updated Webrev which fixes these problems:
>
> http://cr.openjdk.java.net/~sveerabhadra/8212202/webrev.02/
> <http://cr.openjdk.java.net/%7Esveerabhadra/8212202/webrev.02/>
>
> The big problem was that I was not able to
> reproduce this problem neither at my end
> nor at the systems used for PIT testing.
> Only Sergey had produced this NPE till now.
>
> Thanks and regards,
>
> Shashi
>
> *From:*Phil Race
> *Sent:* Wednesday, November 28, 2018 11:19 PM
> *To:* Shashidhara Veerabhadraiah
> <shashidhara.veerabhadraiah at oracle.com>
> <mailto:shashidhara.veerabhadraiah at oracle.com>;
> Prasanta Sadhukhan
> <prasanta.sadhukhan at oracle.com>
> <mailto:prasanta.sadhukhan at oracle.com>;
> 2d-dev at openjdk.java.net
> <mailto:2d-dev at openjdk.java.net>
> *Subject:* Re: [OpenJDK 2D-Dev] [12]
> JDK-8212202: NPE in the print tests after
> JDK-8153732
>
> I am not understanding you. I thought the
> problem to be we got an array of (say) 3
> values
> (ie printer names) returned from native
> where some or all of the *values* were NULL.
> And I am saying we should in such a case
> in the native code, before returning,
> remove from the returned array all values
> that are NULL.
> That could result in an empty (zero
> length) array being returned from native but
> no null names ..
>
> -phil.
>
> On 11/26/18 10:23 PM, Shashidhara
> Veerabhadraiah wrote:
>
> The windows function EnumPrinters()
> returns a value that could be zero or
> greater. If it is zero we have no
> other option but to return null from
> the function. I do not think there is
> a way where we can always make sure we
> get a non-zero value considering the
> various system scenarios. So we should
> handle the null return values as well
> in the caller of this function I think.
>
> Here is the updated Webrev for test fix:
>
> http://cr.openjdk.java.net/~sveerabhadra/8212202/webrev.01/
> <http://cr.openjdk.java.net/%7Esveerabhadra/8212202/webrev.01/>
>
> Thanks and regards,
> Shashi
>
> *From:*Phil Race
> *Sent:* Tuesday, November 27, 2018 1:52 AM
> *To:* Prasanta Sadhukhan
> <prasanta.sadhukhan at oracle.com>
> <mailto:prasanta.sadhukhan at oracle.com>;
> Shashidhara Veerabhadraiah
> <shashidhara.veerabhadraiah at oracle.com>
> <mailto:shashidhara.veerabhadraiah at oracle.com>;
> 2d-dev at openjdk.java.net
> <mailto:2d-dev at openjdk.java.net>
> *Subject:* Re: [OpenJDK 2D-Dev] [12]
> JDK-8212202: NPE in the print tests
> after JDK-8153732
>
> [Removed swing-dev as this as nothing
> to do with swing].
>
> You mention in the bug eval that you
> don't need a new test because this
> is already covered by the test for
> 8153732. If that is the case then this
> bugid should be added to that test.
> Although it also looks like there are
> plenty of tests that provoke this ..
> if all you need is a system without
> any printers then this is a serious
> regression.
>
> I am not sure I am following why
> doCompare() is the place to fix this.
> If getRemotePrinterNames() is
> returning NULL strings, then maybe it
> should not !
>
> I suggest to fix it there.
>
> -phil.
>
>
>
>
>
>
>
> On 11/26/18 7:51 AM, Prasanta
> Sadhukhan wrote:
>
> I am not against doCompare()
> changes. I am just saying run()
> changes are not needed.
>
> Regards
> Prasanta
>
> On 26-Nov-18 9:15 PM, Shashidhara
> Veerabhadraiah wrote:
>
> There is a possible case and
> that is the reason for this
> fix. The possible states for
> prevRemotePinters and
> currentRemotePrinters are null
> and valid values and they can
> reach those states at any time
> either because of network
> disconnect or any other OS
> related changes. With that in
> mind, this fix tries to
> eliminate the possible NPE cases.
>
> Thanks and regards,
>
> Shashi
>
> *From:*Prasanta Sadhukhan
> *Sent:* Monday, November 26,
> 2018 8:01 PM
> *To:* Shashidhara
> Veerabhadraiah
> <shashidhara.veerabhadraiah at oracle.com>
> <mailto:shashidhara.veerabhadraiah at oracle.com>;
> swing-dev at openjdk.java.net
> <mailto:swing-dev at openjdk.java.net>;
> 2d-dev at openjdk.java.net
> <mailto:2d-dev at openjdk.java.net>
> *Subject:* Re: [OpenJDK
> 2D-Dev] [12] JDK-8212202: NPE
> in the print tests after
> JDK-8153732
>
> On 26-Nov-18 6:51 PM,
> shashidhara.veerabhadraiah at oracle.com
> <mailto:shashidhara.veerabhadraiah at oracle.com>
> wrote:
>
> Hi Prasanta, I think we
> should not create a
> behavior across the
> functions. doCompare()
> does only the comparison
> and it may be used for
> other purposes and is
> complete with respect to
> the comparison functionality.
>
> run() function has a
> different behavior as it
> needs to populate the
> prevRemotePrinters and
> then the
> currentRemotePrinters and
> then use the comparison
> functionality. I think
> this is a good way to do.
>
> Even without the if-else
> check, it does populates the
> prevRemotePrinters, no?
> if "prevRemotePrinters" is
> null and currentRemotePrinters
> is null, then no need to
> update. If
> currentRemotePrinters is null,
> then what is the point of
> using getRemotePrintersNames()
> to update prevRemotePrinters
> as currentRemotePrinters is
> also obtained from
> getRemotePrintersNames!!
> If "prevRemotePrinters" is
> null and currentRemotePrinters
> is not null, then doCompare()
> called from run() will be true
> and prevRemotePrinters will be
> populated with
> currentRemotePrinters.
> If "prevRemotePrinters" is not
> null and currentRemotePrinters
> is null, then also
> prevRemotePrinters will be
> populated with
> currentRemotePrinters.
>
> Regards
> Prasanta
>
>
>
>
>
>
>
> Thanks and regards,
>
> Shashi
>
> On 26/11/18 6:03 PM,
> Prasanta Sadhukhan wrote:
>
> Hi Shashi,
>
> I think l437 check of
> if-else *if
> (prevRemotePrinters !=
> null) {*
>
> is not required.
> prevRemotePrinters
> null check is
> addressed in
> str1==null case in
> doCompare().
> If prevRemotePrinters
> is null and
> currentRemotePrinters
> is not null, then you
> update
> prevRemotePrinters to
> currentRemotePrinters
> as per l415 where
> doCompare returns true.
> Also, If
> prevRemotePrinters is
> not null and
> currentRemotePrinters
> is null, then also you
> update
> prevRemotePrinters to
> currentRemotePrinters
> which is the output of
> getRemotePrintersNames().
>
> Regards
> Prasanta
>
>
>
>
>
>
>
> On 26-Nov-18 2:33 PM,
> Shashidhara
> Veerabhadraiah wrote:
>
> Hi All, Please
> review a NPE fix
> for the below bug.
>
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8212202
>
> Webrev:
> http://cr.openjdk.java.net/~sveerabhadra/8212202/webrev.00/
> <http://cr.openjdk.java.net/%7Esveerabhadra/8212202/webrev.00/>
>
> Function
> getRemotePrintersNames()
> may return null
> values and hence
> they need to be
> handled from the
> caller of that
> function which was
> missing earlier.
> This fix handles
> the null return
> values of the said
> function.
>
> Thanks and regards,
>
> Shashi
>
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