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OK. Approved by me .. but .. it would be good if you can point out
any other cases<br>
where you think we can compatibly make changes to get rid of the
need for suppressing this new warning.<br>
<br>
-phil<br>
<br>
On 9/23/19, 12:54 PM, Joe Darcy wrote:
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<p>Hi Phil,</p>
<div class="moz-cite-prefix">On 9/22/2019 1:25 PM, Philip Race
wrote:<br>
</div>
<blockquote type="cite" cite="mid:5D87D8B1.2070708@oracle.com">
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<pre><span class="new">+ @SuppressWarnings("serial") // Not statically typed as Serializable
So is the comment being used to distinguish this overloading of what "serial" means ?
Why not introduce a new warning category ?</span></pre>
</blockquote>
<p><br>
</p>
<p>The -Xlint:serial check in javac has had an operational meaning
of "does a serializable type define a serialVersionUID?" The
work-in-progress is aiming to expand this to cover other aspect
of declaring serializable (and externalizable) types.</p>
<p>It would be possible to put the new checks in their own
category, but that would limit their use and some of new checks
find what are most likely semantic errors, such as declaring a
serialVersionUID in an enum type, which gets silently ignored.<br>
</p>
<p><br>
</p>
<blockquote type="cite" cite="mid:5D87D8B1.2070708@oracle.com">
<pre><span class="new">
</span></pre>
Randomly looking at <br>
====<br>
src/java.desktop/share/classes/java/awt/Container.java<br>
<br>
@@ -3849,10 +3849,11 @@<br>
<br>
/**<br>
* The handler to fire {@code PropertyChange}<br>
* when children are added or removed<br>
*/<br>
+ @SuppressWarnings("serial") // Not statically typed as
Serializable<br>
protected ContainerListener accessibleContainerHandler
= null;<br>
===<br>
<br>
I see that Container has a writeObject method which doesn't
write this field, so it is effectively transient.<br>
<br>
I recognise that it is difficult for the compiler to figure this
out, so perhaps there should just be a policy<br>
not to check classes that have writeObject methods ?<br>
</blockquote>
<p><br>
</p>
<p>Yes, it is not feasible for this level of analysis to decode
the semantics of writeObject and related methods. The analysis
does skip over classes using serialPersistentFields, which is an
alternative mechanism to indicate which fields are used for
serialization.</p>
<p>In terms of possible false positives, I think it is acceptable
to keep doing the checks in the presence of a writeObject method
since a writeObject can be used to make alterations to
serialization process other than changing the set of fields
written out.<br>
</p>
<p><br>
</p>
<blockquote type="cite" cite="mid:5D87D8B1.2070708@oracle.com"> <br>
Also in such a case, would it be an effectively compatible
change to add transient to the field, so that<br>
it presumably would no longer need this warning.<br>
</blockquote>
<p>And the class does define a serialVersionUID so adding
transient to the field should preserve serial compatibility.<br>
</p>
<p><br>
</p>
<blockquote type="cite" cite="mid:5D87D8B1.2070708@oracle.com"> <br>
I haven't looked but presumably there could be other such cases.<br>
<br>
Will you be filing bugs for all the fixable cases ?<br>
</blockquote>
<p>Someone should ;-)</p>
<p>To make sure my intentions are clear, nothing in this overall
cleanup effort should be construed as seeking to assume
ownership of all the serialization in the JDK. The primary
ownership will remain with the component team in question. The
new checks are meant to the an aid, especially to writing new
serializable types, while also prompting some examination of the
existing types in an effort to allow the warning to enabled by
default in the build.</p>
<p>Thanks,<br>
</p>
<p>-Joe</p>
<p><br>
</p>
<blockquote type="cite" cite="mid:5D87D8B1.2070708@oracle.com"> <br>
-phil<br>
<br>
On 9/21/19, 12:48 PM, Joe Darcy wrote:
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cite="mid:ed084e59-bebd-714e-d8af-893115f0e6b3@oracle.com"
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<p>Hello,</p>
<p>Quick background, I'm working on expanding the compile-time
serialization checks of javac's -Xlint:serial option. Ahead
of that work going back, I'm analyzing the JDK sources and
plan to pre-suppress the coming-soon new warnings, fixing or
at least filing follow-up bugs for any problems that are
found. Corresponding suppression bugs are already out for
review against core libs (JDK-8231202) and security libs
(JDK-8231262).</p>
<p>The new check in development is if a serializable class has
an instance field that is not declared to be a serializable
type. This might actually be fine in practice, such as if
the field in question always points to a serializable object
at runtime, but it is arguably worth noting as an item of
potential concern. This check is skipped if the class using
the serialPersistentFields mechanism.</p>
<p>For the client libs, the webrev with the new
@SuppressedWarnings annotations is:<br>
</p>
<p> JDK-8231334: Suppress warnings on non-serializable
instance fields in client libs serializable classes <br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="http://cr.openjdk.java.net/%7Edarcy/8231334.0/">http://cr.openjdk.java.net/~darcy/8231334.0/</a></p>
<p>The changes are mostly in awt, but also some in beans, a
few in printing, and one in sound.<br>
</p>
<p>As discussed with Phil off-line, the new checks also found
an existing known issue, the auxiliary class <span
class="c-message__body" dir="auto" data-qa="message-text">java.awt.ImageMediaEntry
declared in </span><span class="c-message__body"
dir="auto" data-qa="message-text"><span
class="c-message__body" dir="auto"
data-qa="message-text">MediaTracker.java is not
serializable/deserializable in practice (JDK-4397681).</span></span></p>
<p><span class="c-message__body" dir="auto"
data-qa="message-text"><span class="c-message__body"
dir="auto" data-qa="message-text">Thanks,</span></span></p>
<p><span class="c-message__body" dir="auto"
data-qa="message-text"><span class="c-message__body"
dir="auto" data-qa="message-text">-Joe<br>
</span></span></p>
</blockquote>
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