[PATCH] D16376: clang-tidy check: rule-of-five

[David Blaikie via cfe-commits]

On Wed, Feb 3, 2016 at 10:23 AM, Jonathan Coe <jon at jbcoe.net> wrote:

> All the C++ compilers I have tried using (GCC,Clang,MSVC) will generate
> assignment operators even if the user defines a copy-constructor. This is
> the behaviour I set out to write a check for.
>
> The cpp core guide lines recommend defining all or none of the special
> functions
> https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c21-if-you-define-or-delete-any-default-operation-define-or-delete-them-all
>
> If the deprecation warning you mention will turn off the deprecated
> generation of special member functions when others are defined (or warn
> when deprecated compiler-generated functions are used) then the
> rule-of-five check is of reduced value.
>

It can't stop them being generated, because that's required behavior -
warnings don't change the program behavior.

Wording like this is in the C++11 standard:

"If the class definition does not explicitly declare a copy constructor,
one is declared implicitly. If the class definition declares a move
constructor or move assignment operator, the implicitly declared copy
constructor is defined as deleted; otherwise, it is defined as defaulted
(8.4). The latter case is deprecated if the class has a user-declared copy
assignment operator or a user-declared destructor."

(similar wording for the copy assignment operator, the dtor has a
different/special case if I recall correctly)


>
> Jon
>
> On 3 February 2016 at 17:40, David Blaikie <dblaikie at gmail.com> wrote:
>
>> Is this really that useful of a rule? The language does the right thing
>> for the most part already (you don't need to explicitly delete them -
>> they're implicitly deleted if you define any others - except for backcompat
>> with C++98, but those cases are deprecated & we should probably split out
>> the warning for that deprecation so it's easier to turn on separately)
>>
>> On Wed, Feb 3, 2016 at 5:25 AM, Jonathan B Coe via cfe-commits <
>> cfe-commits at lists.llvm.org> wrote:
>>
>>> jbcoe retitled this revision from "clang-tidy check: Assignment and
>>> Construction" to "clang-tidy check: rule-of-five".
>>> jbcoe removed rL LLVM as the repository for this revision.
>>> jbcoe updated this revision to Diff 46775.
>>> jbcoe added a comment.
>>>
>>> I've responded to review comments (thanks for those) and renamed the
>>> check to 'rule-of-five'.
>>>
>>> I think it needs moving to cppcoreguidelines and needs destructor
>>> handling adding to it. As suggested, I'll address that in a later patch if
>>> everything else looks ok.
>>>
>>>
>>> http://reviews.llvm.org/D16376
>>>
>>> Files:
>>>   clang-tidy/misc/CMakeLists.txt
>>>   clang-tidy/misc/MiscTidyModule.cpp
>>>   clang-tidy/misc/RuleOfFiveCheck.cpp
>>>   clang-tidy/misc/RuleOfFiveCheck.h
>>>   docs/clang-tidy/checks/list.rst
>>>   docs/clang-tidy/checks/misc-rule-of-five.rst
>>>   test/clang-tidy/misc-rule-of-five.cpp
>>>
>>>
>>> _______________________________________________
>>> cfe-commits mailing list
>>> cfe-commits at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>>>
>>>
>>
>
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