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</o:shapelayout></xml><![endif]--></head><body lang=EN-IE link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>Long before ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>deleted</span><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>’ was added to the C++ language, reserving implicitly defined members as ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>private</span><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>’ members was a very common pattern. Indeed, I can find many examples where I (and others) routinely used this pattern. For example, in from code I wrote in 1994 I have the following example (which I still use today -- if it ain’t broke don’t fix it):<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>class MemoryPool {<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>...<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>private: // Interface: remove copying and address-of from the interface<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'> MemoryPool ( const MemoryPool& );<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'> MemoryPool& operator = ( const MemoryPool& );<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'> MemoryPool* operator & ();<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>...<o:p></o:p></span></p><p class=MsoNormal style='margin-left:36.0pt'><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>};<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>Without this pattern, these methods were implicitly defined whether you liked it or not; but with the consistent use of this pattern if these methods were referenced by a non-member there was a compile-time error (access constraint), and if a member accidentally referenced them there was a link-time error (undefined symbol), ‘deleted’ just elevated this to being also a compile-time error.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>So aside from necessity in modern C++, I would expect that this pattern still persists, and that ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>deleted</span><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>’ has been added (probably as a macro whose definition is dependent on C++ Standard version for portability) to such declarations to bring it up to date with the Standard, but they are almost certainly more likely to be ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>private</span><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>’. This would make ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>private</span><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>/</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>deleted</span><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>’ more likely than ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>public</span><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>/</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>deleted</span><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>’, especially in portable legacy code-bases. The incredibly helpful ‘</span><span style='font-family:"Courier New";color:black;mso-fareast-language:EN-US'>overloaded</span><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>’ is often used in a similar way with a Standard dependent macro definition.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'> MartinO<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><b><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'>From:</span></b><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> cfe-dev [mailto:cfe-dev-bounces@lists.llvm.org] <b>On Behalf Of </b>James Dennett via cfe-dev<br><b>Sent:</b> 31 October 2017 15:12<br><b>To:</b> Nicolas Lesser <blitzrakete@gmail.com><br><b>Cc:</b> Clang Dev <cfe-dev@lists.llvm.org><br><b>Subject:</b> Re: [cfe-dev] Why does clang-tidy recommend deleted member functions should be public?<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><div><div><div><p class=MsoNormal>On Mon, Oct 30, 2017 at 11:34 PM, Nicolas Lesser via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a>> wrote:<o:p></o:p></p><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-right:0cm'><div><p class=MsoNormal>There's nothing inherently wrong with deleting member functions that are private, but if they are public, you will get a better error message (namely that the function is deleted) instead of an error message that says that the functions are private.<o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>AFAIK, Qt supports C++11, but also previous versions. I don't know how they implemented Q_DISABLE_COPY, but it probably expands to copy constructor and copy assignment declarations before C++11, and if you enable C++11 mode, deletes them instead. In pre-C++11, the declarations would have to be private, so you get an error at compile time and not at link time.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>If you're only compiling with C++11, it should be safe to put the macro in public. Alternately, you can always delete the copy constructor and assignment yourself.<o:p></o:p></p></div></div></blockquote></div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Another reason to prefer making these "public" is non-technical: they affect fundamental aspects of the client interface of a class, and hiding them in "private" as if they were implementation details is unhelpful. Unfortunately necessary in C++98, but no longer needed with C++11.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>-- James<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div></div></div></body></html>