Re: [boost] [function] Placement new warnings from gcc 6

Subject: Re: [boost] [function] Placement new warnings from gcc 6
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2016-04-02 09:08:28

On 2016-04-02 15:45, Peter Dimov wrote:
> Andrey Semashev wrote:
>
>> Thanks. I've made a patch with a similar idea:
>>
>> https://github.com/boostorg/function/pull/9
>
> This works, although the following alternative:
>
> template<class T> union function_buffer_
> {
>    // as before
>    mutable T data;
> };
>
> size_t const function_buffer_size = sizeof(function_buffer_<char>);
>
> typedef function_buffer_<char[function_buffer_size]> function_buffer;
>
> seems slightly more maintainable as it doesn't perform the size
> computation separately.

That instantiates the template twice, maybe it'll affect compile times. 
Also, I'm a bit cautious about using an array type in template 
parameters - maybe it'll cause trouble on ancient compilers?

I guess, I could extract all members other than 'data' to a separate 
union and then:

   union function_buffer
   {
     mutable function_buffer_members m;
     mutable char data[sizeof(function_buffer_members)];
   };

This would require more modifications to the code though.

(Sigh... if only we could inherit unions...)