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<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">Paul Sandoz <paul.sandoz@oracle.com><br>
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<p class="MsoNormal">> In your modeling approach (ignoring multi-catch for now) I think it may be possible to refer directly to the catch blocks as successors for both exit and enter, thereby avoiding a level of indirection.
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">I think it would be a good start with significant effect. However, the position of each handler in the exception region stack would be very unclear and I would implicitly position them out of any stack. It
is much simple to calculate which exception regions should each handler re-enter, rather than which regions to exit. It will also make much simpler modeling of variables modified in the try blocks. Exception regions exit and immediate re-enter after the variable
modification fixes the flow graph. <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"><o:p> </o:p></p>
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<p class="MsoNormal">> It would be interesting to expand on your example to include finally
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Finally blocks are just complex compositions of try/catch blocks (with duplications of the finally block code to all exit points).
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">When lifting from bytecode I do not recognize try/finally, it would require further analysis to identify specific try/catch structures and lift it to try/finally.<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">The example code:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> static void nestedCatch(int i) {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> PrintStream out = System.out;</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> while (true) {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> try {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> try {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> if (i == 0) {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> break;</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> } else if (i == 1) {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> continue;</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> }</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> } catch (NullPointerException npe) {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("CATCH NPE");</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> } finally {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("FINALLY INNER");</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> }</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("AFTER TRY INNER");</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> } catch (RuntimeException re) {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("CATCH RE");</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> } finally {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("FINALLY OUTER");</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> }</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> }</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#212121"><o:p> </o:p></span></p>
<p class="MsoNormal">Can be desugar the try/finally as:</p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> static void nestedCatch(int i) {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> PrintStream out = System.out;</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> while (true) {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> try {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> try {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> try {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> try {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> if (i == 0) {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("FINALLY INNER");</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("FINALLY OUTER");</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> break;</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> } else if (i == 1) {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("FINALLY INNER");</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("FINALLY OUTER");</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> continue;</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> }</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> } catch (NullPointerException npe) {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("CATCH NPE");<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> }</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> } catch (Throwable t) {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("FINALLY INNER");<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> throw t;</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> }</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("FINALLY INNER");</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("AFTER TRY INNER");</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> } catch (RuntimeException re) {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("CATCH RE");<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> } catch (Throwable t) {</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("FINALLY OUTER");<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> throw t;</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> }</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> out.println("FINALLY OUTER");</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> }</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#212121"> }</span><span style="color:#212121"><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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