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<p class="MsoNormal"><span style="font-size:11.0pt">So good news, after a brief scan I haven't found a single method in the JDK which would violate the LIFO of the exception region entries and exits.<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">FYI: I've also counted the max exception stack depth and number of gaps.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Here is a frequency table of the max exception stack depths:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">0: 205345 // methods with no exception regions<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">1: 11392 <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">2: 1866<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">3: 509<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">4: 205<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">5: 61<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">6: 23<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">7: 16<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">8: 10<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">9: 1<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">10: 3<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Across the JDK I found 9792 gaps in the exception regions (split exception regions).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">It would be interesting to see a model of the code with 10 layers of try/catch blocks ;)<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">Adam<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"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="color:black">From:
</span></b><span style="color:black">babylon-dev <babylon-dev-retn@openjdk.org> on behalf of Adam Sotona <adam.sotona@oracle.com><br>
<b>Date: </b>Thursday, 10 October 2024 at 10:04<br>
<b>To: </b>Paul Sandoz <paul.sandoz@oracle.com><br>
<b>Cc: </b>babylon-dev@openjdk.org <babylon-dev@openjdk.org><br>
<b>Subject: </b>Re: ExceptionRegion modeling issues and proposed improvements<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="color:black">From:
</span></b><span style="color:black">Paul Sandoz <paul.sandoz@oracle.com></span><o:p></o:p></p>
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<p class="MsoNormal">> Is the catch block stack order important? Can we encounter an exception region exit that refers to B when the top of the stack is C? <o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">Intuitively I would say the order should be preserved and my brain model for that is a lifo stack, however that idea is inferred from JLS.<o:p></o:p></p>
<p class="MsoNormal">Practically there is nothing preventing to have a bytecode with exception table entries starting and ending independently of each other.<o:p></o:p></p>
<p class="MsoNormal">Absolute order of the exception table entries is critical, however the whole exception region (a section of bytecode handling specific exception by a specific handler) can consist of multiple exception table entries and can (theoretically)
appear in a different relative order to other regions in different situations.<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">I'll scan some code to collect all real situations versus what is theoretically possible. I think I've seen gaps (instructions exclusions) of a top level try block, while the nested was uninterrupted (however
need to find it to confirm).</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Adam</span><o:p></o:p></p>
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