[lldb-dev] Unifying ctor+Clear() inits into in-class initializers?

[Zachary Turner via lldb-dev]

+1, this pattern looks like asking for UB
On Mon, Nov 20, 2017 at 11:57 AM Leonard Mosescu via lldb-dev <
lldb-dev at lists.llvm.org> wrote:

>         void Clear() {
>>           this->~ClassName();
>>           new (this) ClassName();
>>         }
>
>
> My 2c: this is clever, but not without downsides:
> 1. It may do more than intended (it will destroy all members / bases)
> 2. It forces construction and 'reset' to be exactly the same, which is not
> always desirable
> 3. Most importantly if you really want a freshly initialized object, just
> do that (create a new object)
>
> I like in-class initializers, but for clear/reset operations I prefer a
> standalone operation. And as Pavel suggested, calling 'clear' from the
> constructor is a good way to factor out commonality.
>
>
>
> On Sun, Nov 19, 2017 at 6:58 AM, Jan Kratochvil via lldb-dev <
> lldb-dev at lists.llvm.org> wrote:
>
>> Hi,
>>
>> https://reviews.llvm.org/D40212
>>
>> At least DWARFCompileUnit and I see even for example MachVMRegion
>> duplicate
>> intialization of fields in both their constructor and Clear().  Moreover
>> the
>> initialization is in different place than declaration of the member
>> variable.
>>
>> Is it OK to just use in-class member variable initializers and:
>>         void Clear() {
>>           this->~ClassName();
>>           new (this) ClassName();
>>         }
>> ?
>>
>> Pavel Labath otherwise suggests to just call Clear() from the constructor.
>> Still then I find the code could be more readable with in-class members
>> initializers - moreover during further refactorizations+extensions.
>>
>>
>> Thanks,
>> Jan Kratochvil
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>>
>
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