<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Mon, Mar 10, 2014 at 10:13 AM, Per Viberg <span dir="ltr"><<a href="mailto:Per.Viberg@evidente.se" target="_blank">Per.Viberg@evidente.se</a>></span> wrote:<br>
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<div style="direction:ltr;font-size:10pt;font-family:Tahoma">thanks guys for the quick reply,<br>
<br>
yeah, I suspected something like that. The only thing I was surprised about was that there is a Stmt at all inside a switch "label". I mean, if they are just like goto labels, then no statement at all would seem more intuitive. </div>
</div></blockquote><div><br></div><div>Consider this:</div><div><br></div><div>switch (x) {</div><div> if (a)</div><div> case 1: b;</div><div> c;</div><div>}</div><div><br></div><div>An 'if' statement can only have one substatement, so the case label *must* have 'b' as its child or we'd have no way to represent this code. And the case label must *not* have 'c' as its child, or we'd be representing this incorrectly.</div>
<div><br></div><div>Also, the relevant language standards say that labels have a single statement as a child, and we try to make our representations faithful to the relevant standards as far as is reasonably possible.</div>
<div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><div style="direction:ltr;font-size:10pt;font-family:Tahoma"><div class="">
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Per Viberg </span><span style="font-size:8pt;font-family:'Arial','sans-serif';color:gray" lang="EN-US">Senior Engineer</span><span style="font-size:8.5pt;font-family:'Arial','sans-serif';color:gray" lang="EN-US"><br>
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<div style="direction:ltr"><font color="#000000" face="Tahoma"><b>Från:</b> Jordan Rose [<a href="mailto:jordan_rose@apple.com" target="_blank">jordan_rose@apple.com</a>]<br>
<b>Skickat:</b> den 10 mars 2014 17:20<br>
<b>Till:</b> Per Viberg<br>
<b>Cc:</b> cfe-dev Developers; Tom Honermann<br>
<b>Ämne:</b> Re: [cfe-dev] SwitchStmt bug?<br>
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<div>On Mar 10, 2014, at 7:49 , Tom Honermann <<a href="mailto:thonermann@coverity.com" target="_blank">thonermann@coverity.com</a>> wrote:</div>
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<blockquote type="cite">On 03/10/2014 10:23 AM, Per Viberg wrote:<br>
<blockquote type="cite"><br>
Hi all,<br>
<br>
I was inspecting the AST dump of this switch:<br>
<br>
void test_switch(int t) {<br>
switch(t)<br>
{<br>
case 1:<br>
y = 11;<br>
case 2:<br>
y = 9;<br>
x = 12;<br>
break;<br>
default:<br>
break;<br>
}<br>
}<br>
<br>
and I got something I didn't expect. The second CaseStmt does only<br>
contain the first statement that is under it's label. The "x=12;" gets<br>
its own Stmt outside the CaseStmt but inside the CompoundStmt inside the<br>
SwitchStmt. I would anticipate that all statements under a label either<br>
are: inside the CaseStmt or: outside but inside the CompoundStmt. Any<br>
reason for this?.<br>
</blockquote>
<br>
This is expected. Case statements have just one sub statement.<br>
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<div>More generally, case statements are just labels, and have the same basic rules as regular old goto labels. Having case statements "just" be labels is what allows things like <a href="http://en.wikipedia.org/wiki/Duff's_device" target="_blank">Duff's Device</a> in
C:</div>
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</div>
<div>switch(count % 8) {<span style="white-space:pre-wrap"> </span>
<br>
case 0:<span style="white-space:pre-wrap"> </span>do {<span style="white-space:pre-wrap">
</span>*to = *from++;<br>
case 7:<span style="white-space:pre-wrap"> </span>*to = *from++;<br>
case 6:<span style="white-space:pre-wrap"> </span>*to = *from++;<br>
case 5:<span style="white-space:pre-wrap"> </span>*to = *from++;<br>
case 4:<span style="white-space:pre-wrap"> </span>*to = *from++;<br>
case 3:<span style="white-space:pre-wrap"> </span>*to = *from++;<br>
case 2:<span style="white-space:pre-wrap"> </span>*to = *from++;<br>
case 1:<span style="white-space:pre-wrap"> </span>*to = *from++;<br>
<span style="white-space:pre-wrap"></span>} while(--n > 0);<br>
}</div>
<div><br>
</div>
<div>This is the opposite situation, really, because here we need cases <i>inside</i> the loop that's inside the switch. But once you're supporting this, the representation as a simple label is just easier to work with.</div>
<div><br>
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<div>Jordan<br>
<br>
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