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<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">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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