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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Cool. Although I have to wonder if there’s a consolidated 2011-as-amended document,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">or do I have to cruise the defects page every time I’m trying to look something up?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">--paulr<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> metafoo@gmail.com [mailto:metafoo@gmail.com]
<b>On Behalf Of </b>Richard Smith<br>
<b>Sent:</b> Wednesday, April 02, 2014 6:58 PM<br>
<b>To:</b> Robinson, Paul<br>
<b>Cc:</b> cfe-dev@cs.uiuc.edu<br>
<b>Subject:</b> Re: [cfe-dev] Q. on pointer/integer comparison<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">On Wed, Apr 2, 2014 at 5:47 PM, Robinson, Paul <<a href="mailto:Paul_Robinson@playstation.sony.com" target="_blank">Paul_Robinson@playstation.sony.com</a>> wrote:<o:p></o:p></p>
<p class="MsoNormal">With -std=c++11, clang will complain about the expression in<br>
bar() but not foo().<br>
<br>
bool foo(int *p) { return (p != 0); }<br>
bool bar(int* p) { return (p != (1 - 1)); }<br>
<br>
With -std=c++03, clang accepts both.<br>
<br>
[expr.const]p3 has a Note that says an integral constant expression<br>
can be used as a null pointer constant.<br>
So, I think Clang should accept both even in C++11 mode.<br>
<br>
Bug, or my usual confusion about the standard? (I can see issuing<br>
a warning, because it would be hard to contrive a real-world case<br>
where somebody would actually want to do this; but if it conforms,<br>
Clang should not reject it.)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">This was changed by DR 903:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"> <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#903">
http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#903</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">We implement this DR in C++11 onwards, since the C++98 rules are *really* broken when combined with C++11's generalized constant expressions. Without this change, ridiculous things like<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"> struct S { int n; };<o:p></o:p></p>
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<p class="MsoNormal"> int *p = S().n;<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">... would compile, because S().n is an integral constant expression with value 0.<o:p></o:p></p>
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