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Indeed, I noted that our StackMapGenerator eagerly checks if a newly encountered store instruction (the istore_1 in the exception handler range) breaks the stack maps, and our StackMapGenerator would have failed fast in that case.</div>
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Chen</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Adam Sotona <adam.sotona@oracle.com><br>
<b>Sent:</b> Wednesday, January 29, 2025 11:35 AM<br>
<b>To:</b> Mark Roberts <markro@cs.washington.edu>; classfile-api-dev@openjdk.org <classfile-api-dev@openjdk.org><br>
<b>Cc:</b> Chen Liang <chen.l.liang@oracle.com><br>
<b>Subject:</b> Re: [External] : RE: StackMap problem</font>
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<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif">I see, the
</span><span style="font-size:11.0pt">frame is listed at the end of the line.</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt">Key question still remains – how the instrumentation is done?</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif">Class- File API regenerates the stack map when I create similar method and inject the istore_1 and iload_1 instructions.
</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif">Adam</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif"> </span></p>
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<p class="x_MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:12.0pt; font-family:"Aptos",sans-serif; color:black">From:
</span></b><span style="font-size:12.0pt; font-family:"Aptos",sans-serif; color:black">Mark Roberts <markro@cs.washington.edu><br>
<b>Date: </b>Wednesday, 29 January 2025 at 17:45<br>
<b>To: </b>Adam Sotona <adam.sotona@oracle.com>, classfile-api-dev@openjdk.org <classfile-api-dev@openjdk.org><br>
<b>Cc: </b>Chen Liang <chen.l.liang@oracle.com><br>
<b>Subject: </b>[External] : RE: StackMap problem</span></p>
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<p class="x_MsoNormal"><span style="font-size:11.0pt">The ‘before’ was compiled with javac version 24-ea+22-269, but I compiled with javac version 17.0.11 and got the exact same binary. The stack map frames are there:</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> StackMapTable:</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> StackMap((SAME_LOCALS_1_STACK, offset delta=19, stack items={(type=Object, class=DataStructures.Overflow)}), (SAME, offset delta=0))</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt">The first (@19) is the target of the exception handler, the second (@20) is the target of the branch @16.</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt">It all looks good to me.</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt">Mark</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
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<p class="x_MsoNormal"><b><span style="font-size:11.0pt">From:</span></b><span style="font-size:11.0pt"> Adam Sotona <</span><a href="mailto:adam.sotona@oracle.com"><span style="font-size:11.0pt">adam.sotona@oracle.com</span></a><span style="font-size:11.0pt">>
<br>
<b>Sent:</b> Wednesday, January 29, 2025 1:07 AM<br>
<b>To:</b> Mark Roberts <</span><a href="mailto:markro@cs.washington.edu"><span style="font-size:11.0pt">markro@cs.washington.edu</span></a><span style="font-size:11.0pt">>;
</span><a href="mailto:classfile-api-dev@openjdk.org"><span style="font-size:11.0pt">classfile-api-dev@openjdk.org</span></a><span style="font-size:11.0pt"><br>
<b>Cc:</b> Chen Liang <</span><a href="mailto:chen.l.liang@oracle.com"><span style="font-size:11.0pt">chen.l.liang@oracle.com</span></a><span style="font-size:11.0pt">><br>
<b>Subject:</b> Re: StackMap problem</span></p>
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<p class="x_MsoNormal"> </p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif">Hi Mark,</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif">Both attached class listings are missing stack map frames at branch targets, and they seem to be invalid.</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif">I would like to ask what compiler generates the first class and how your tool adds the instrumentation code.</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif">My first impression is that I don’t see any trace of Class-File API stack map generator involment. Transformation of a method with missing or invalid stack map would generate
new stack maps, unless explicitly disabled.</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif">Thanks,</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif">Adam</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Aptos",sans-serif"> </span></p>
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<p class="x_MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:12.0pt; font-family:"Aptos",sans-serif; color:black">From:
</span></b><span style="font-size:12.0pt; font-family:"Aptos",sans-serif; color:black">classfile-api-dev <</span><a href="mailto:classfile-api-dev-retn@openjdk.org"><span style="font-size:12.0pt; font-family:"Aptos",sans-serif">classfile-api-dev-retn@openjdk.org</span></a><span style="font-size:12.0pt; font-family:"Aptos",sans-serif; color:black">>
on behalf of Mark Roberts <</span><a href="mailto:markro@cs.washington.edu"><span style="font-size:12.0pt; font-family:"Aptos",sans-serif">markro@cs.washington.edu</span></a><span style="font-size:12.0pt; font-family:"Aptos",sans-serif; color:black">><br>
<b>Date: </b>Tuesday, 28 January 2025 at 21:45<br>
<b>To: </b></span><a href="mailto:classfile-api-dev@openjdk.org"><span style="font-size:12.0pt; font-family:"Aptos",sans-serif">classfile-api-dev@openjdk.org</span></a><span style="font-size:12.0pt; font-family:"Aptos",sans-serif; color:black"> <</span><a href="mailto:classfile-api-dev@openjdk.org"><span style="font-size:12.0pt; font-family:"Aptos",sans-serif">classfile-api-dev@openjdk.org</span></a><span style="font-size:12.0pt; font-family:"Aptos",sans-serif; color:black">><br>
<b>Cc: </b>Chen Liang <</span><a href="mailto:chen.l.liang@oracle.com"><span style="font-size:12.0pt; font-family:"Aptos",sans-serif">chen.l.liang@oracle.com</span></a><span style="font-size:12.0pt; font-family:"Aptos",sans-serif; color:black">><br>
<b>Subject: </b>StackMap problem</span></p>
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<p class="x_MsoNormal"><span style="font-size:11.0pt">The existence of compiler generated, unnamed local temps (no LocalVariable code element) seems to cause a problem with stack maps.</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt">The ‘source’ attachment shows the problem method. The ‘before’ attachment shows the generated code before instrumentation. Note that the compiler generates an unnamed temp at slot 0 to store the exception
code. The stackmap for the branch target says same locals, which is correct.</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt">The ‘after’ attachment shows the code generated after our tool has added instrumentation code – note the addition of a new local variable at slot 1. The stackmap for the branch target still says same locals,
which is no longer correct. This causes the iload_1 @41 to fail.</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt">I tried to see if this issue has already been reported, but I was unable to figure out how to search
</span><a href="https://urldefense.com/v3/__https:/bugs.java.com/bugdatabase/__;!!ACWV5N9M2RV99hQ!Oxj6SR2NV9Ad-EfEdNCFmjPL0gx3yAPgZ8jQoj8jWrlF9W-NohRiSuxWzqdOPpnNxoTuYr4zSmL9s1LDi14H1ymI$"><span style="font-size:11.0pt">https://bugs.java.com/bugdatabase/</span></a><span style="font-size:11.0pt">
by keyword.</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt">Mark</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
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