[OpenJDK 2D-Dev] [12] JDK-8212202: NPE in the print tests after JDK-8153732
Prasanta Sadhukhan
prasanta.sadhukhan at oracle.com
Fri Feb 15 06:57:50 UTC 2019
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>; Shashidhara Veerabhadraiah
> <shashidhara.veerabhadraiah 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 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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