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<font size="4"><font face="monospace">I like how this leans on the
existing Transform abstraction -- and it is useful beyond just
tracking -- it means existing transforms can be combined with
generation if that is convenient. <br>
<br>
If the user wants to chain some transforms together *and* wants
to retain references to each element in the chain -- which they
will probably want to do if there are multiple kinds of
"trackers" here, such as tracking stack + tracking locals --
then there is a little trickiness to setting the pipeline up
right. The user will have to do something like:<br>
<br>
withMethodBody(b -> { <br>
StackTracker st = StackTracker.of();<br>
LocalTracker lt = LocalTracker.of();<br>
transforming(st.andThen(lt), cb -> { ... build here,
can use st/lt ... });<br>
});<br>
<br>
What's happening here is that the transforms are stateful, but
the user is creating the transform instances directly, rather
than through a factory, so they can retain references to them.
This is totally OK, as long as the user doesn't try to reuse the
same StackTracker instance across multiple methods at the same
time. <br>
<br>
The spec for StackTracker and friends will probably need some
extensive examples to guide users to the right idiom. <br>
</font></font><br>
<div class="moz-cite-prefix">On 8/26/2022 9:58 AM, Adam Sotona
wrote:<br>
</div>
<blockquote type="cite" cite="mid:CY4PR1001MB215076DCE613CC1D91DCE6A38C759@CY4PR1001MB2150.namprd10.prod.outlook.com">
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<div class="WordSection1">
<p class="MsoNormal"><span style="font-size:11.0pt">Based on
various optiona how to expose the StackTracker through the
Classfile API I’ve decided to refactor the proposal in:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><a href="https://github.com/openjdk/jdk-sandbox/pull/34" moz-do-not-send="true" class="moz-txt-link-freetext">https://github.com/openjdk/jdk-sandbox/pull/34</a>
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Instead of
embedded implementation and Classfile.Option here is a
proposal to expose StackTracker as CodeTransform and
implement CodeBuilder::transforming method:<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:#969696">/**</span><span style="font-family:"Courier
New",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:#969696">*
<b>Builds</b></span><span style="font-family:"Courier
New",serif;color:black"> </span>
<b><span style="font-family:"Courier
New",serif;color:#969696">code</span></b><span style="font-family:"Courier
New",serif;color:black">
</span><b><span style="font-family:"Courier
New",serif;color:#969696">fragment</span></b><span style="font-family:"Courier
New",serif;color:black">
</span><b><span style="font-family:"Courier
New",serif;color:#969696">generated</span></b><span style="font-family:"Courier
New",serif;color:black">
</span><b><span style="font-family:"Courier
New",serif;color:#969696">by</span></b><span style="font-family:"Courier
New",serif;color:black">
</span><b><span style="font-family:"Courier
New",serif;color:#969696">the</span></b><span style="font-family:"Courier
New",serif;color:black">
</span><b><span style="font-family:"Courier
New",serif;color:#969696">handler</span></b><span style="font-family:"Courier
New",serif;color:black">
</span><b><span style="font-family:"Courier
New",serif;color:#969696">and</span></b><span style="font-family:"Courier
New",serif;color:black">
</span><b><span style="font-family:"Courier
New",serif;color:#969696">synchronously</span></b><span style="font-family:"Courier
New",serif;color:black">
</span><b><span style="font-family:"Courier
New",serif;color:#969696">transformed.</span></b><span style="font-family:"Courier
New",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:#969696">*
<b>@param</b></span><span style="font-family:"Courier
New",serif;color:black"> transform
</span><span style="font-family:"Courier
New",serif;color:#969696">the</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">transform</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">to</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">apply</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">to</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">the</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">code</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">generated</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">by</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">the</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">handler</span><span style="font-family:"Courier
New",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:#969696">*
<b>@param</b></span><span style="font-family:"Courier
New",serif;color:black"> handler
</span><span style="font-family:"Courier
New",serif;color:#969696">handler</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">that</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">receives</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">a {<b>@linkplain</b></span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">BlockCodeBuilder} to</span><span style="font-family:"Courier
New",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:#969696">* generate</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">the</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">code.</span><span style="font-family:"Courier
New",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:#969696">*
<b>@return</b></span><span style="font-family:"Courier
New",serif;color:black"> </span>
<span style="font-family:"Courier
New",serif;color:#969696">this</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#969696">builder</span><span style="font-family:"Courier
New",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:black"></span><span style="font-family:"Courier
New",serif;color:#969696">*/</span><span style="font-family:"Courier
New",serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:#336BDD">default</span><span style="font-family:"Courier
New",serif;color:black"> CodeBuilder
<b>transforming</b>(CodeTransform transform,
Consumer<CodeBuilder> handler) {<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#336BDD">var</span><span style="font-family:"Courier
New",serif;color:black"> resolved = transform.resolve(</span><span style="font-family:"Courier
New",serif;color:#336BDD">this</span><span style="font-family:"Courier
New",serif;color:black">);<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:black">
resolved.startHandler().run();<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:black"> handler.accept(</span><span style="font-family:"Courier
New",serif;color:#336BDD">new</span><span style="font-family:"Courier
New",serif;color:black"> TransformingCodeBuilder(</span><span style="font-family:"Courier
New",serif;color:#336BDD">this</span><span style="font-family:"Courier
New",serif;color:black">, resolved.consumer()));<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:black">
resolved.endHandler().run();<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#336BDD">return</span><span style="font-family:"Courier
New",serif;color:black">
</span><span style="font-family:"Courier
New",serif;color:#336BDD">this</span><span style="font-family:"Courier
New",serif;color:black">;<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Courier
New",serif;color:black">}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Modified
usage of the StackTracker is reflected in the
StackTrackerTest:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<pre style="background:white"><span style="color:black">Classfile.<span class="st0"><i>build</i></span>(ClassDesc.<span class="st0"><i>of</i></span>(</span><span class="string"><span style="color:#1E9347">"Foo"</span></span><span style="color:black">), clb -><o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> clb.withMethodBody(</span><span class="string"><span style="color:#1E9347">"m"</span></span><span style="color:black">, MethodTypeDesc.<span class="st0"><i>of</i></span>(ConstantDescs.</span><span class="st1"><i><span style="color:#CE54B8">CD_Void</span></i></span><span style="color:black">), 0, cob -> {<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> </span><span class="literal"><span style="color:#336BDD">var</span></span><span style="color:black"> stackTracker = </span><span class="literal"><span style="color:#336BDD">new</span></span><span style="color:black"> StackTracker();<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> cob.<b>transforming</b>(stackTracker, stcb -> {<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertEquals</i></span>(stackTracker.stack().get(), List.<span class="st0"><i>of</i></span>());<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> stcb.aload(0);<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertEquals</i></span>(stackTracker.stack().get(), List.<span class="st0"><i>of</i></span>(</span><span class="st1"><i><span style="color:#CE54B8">ReferenceType</span></i></span><span style="color:black">));<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> stcb.lconst_0();<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertEquals</i></span>(stackTracker.stack().get(), List.<span class="st0"><i>of</i></span>(</span><span class="st1"><i><span style="color:#CE54B8">LongType</span></i></span><span style="color:black">, </span><span class="st1"><i><span style="color:#CE54B8">ReferenceType</span></i></span><span style="color:black">));<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> stcb.trying(tryb -> {<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertEquals</i></span>(stackTracker.stack().get(), List.<span class="st0"><i>of</i></span>(</span><span class="st1"><i><span style="color:#CE54B8">LongType</span></i></span><span style="color:black">, </span><span class="st1"><i><span style="color:#CE54B8">ReferenceType</span></i></span><span style="color:black">));<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> tryb.iconst_1();<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertEquals</i></span>(stackTracker.stack().get(), List.<span class="st0"><i>of</i></span>(</span><span class="st1"><i><span style="color:#CE54B8">IntType</span></i></span><span style="color:black">, </span><span class="st1"><i><span style="color:#CE54B8">LongType</span></i></span><span style="color:black">, </span><span class="st1"><i><span style="color:#CE54B8">ReferenceType</span></i></span><span style="color:black">));<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> tryb.ifThen(thb -> {<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertEquals</i></span>(stackTracker.stack().get(), List.<span class="st0"><i>of</i></span>(</span><span class="st1"><i><span style="color:#CE54B8">LongType</span></i></span><span style="color:black">, </span><span class="st1"><i><span style="color:#CE54B8">ReferenceType</span></i></span><span style="color:black">));<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> thb.constantInstruction(ClassDesc.<span class="st0"><i>of</i></span>(</span><span class="string"><span style="color:#1E9347">"Phee"</span></span><span style="color:black">));<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertEquals</i></span>(stackTracker.stack().get(), List.<span class="st0"><i>of</i></span>(</span><span class="st1"><i><span style="color:#CE54B8">ReferenceType</span></i></span><span style="color:black">, </span><span class="st1"><i><span style="color:#CE54B8">LongType</span></i></span><span style="color:black">, </span><span class="st1"><i><span style="color:#CE54B8">ReferenceType</span></i></span><span style="color:black">));<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> thb.athrow();<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertFalse</i></span>(stackTracker.stack().isPresent());<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> });<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertEquals</i></span>(stackTracker.stack().get(), List.<span class="st0"><i>of</i></span>(</span><span class="st1"><i><span style="color:#CE54B8">LongType</span></i></span><span style="color:black">, </span><span class="st1"><i><span style="color:#CE54B8">ReferenceType</span></i></span><span style="color:black">));<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> tryb.return_();<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertFalse</i></span>(stackTracker.stack().isPresent());<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> }, catchb -> catchb.catching(ClassDesc.<span class="st0"><i>of</i></span>(</span><span class="string"><span style="color:#1E9347">"Phee"</span></span><span style="color:black">), cb -> {<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertEquals</i></span>(stackTracker.stack().get(), List.<span class="st0"><i>of</i></span>(</span><span class="st1"><i><span style="color:#CE54B8">ReferenceType</span></i></span><span style="color:black">));<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> cb.athrow();<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertFalse</i></span>(stackTracker.stack().isPresent());<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> }));<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> });<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertTrue</i></span>(stackTracker.maxStackSize().isPresent());<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> <span class="st0"><i>assertEquals</i></span>((</span><span class="literal"><span style="color:#336BDD">int</span></span><span style="color:black">)stackTracker.maxStackSize().get(), 4);<o:p></o:p></span></pre>
<pre style="background:white"><span style="color:black"> }));<o:p></o:p></span></pre>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Adam<o:p></o:p></span></p>
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