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: 2016-04-05 00:12:09

On 2016-04-05 06:39, Gavin Lambert wrote:
> On 4/04/2016 19:52, Andrey Semashev wrote:
>> On 2016-04-04 04:35, Gavin Lambert wrote:
>>> Could you do this with an anonymous union?  eg:
>>>
>>> union function_buffer
>>> {
>>>     mutable union function_buffer_members
>>>     {
>>>         ...
>>>     };
>>>     mutable char data[sizeof(function_buffer_members)];
>>> };
>>>
>>> Haven't tested this; not sure if it's legal to get the sizeof a subtype
>>> nested in the same scope like this, but it at least seems plausible.
>>
>> That is a named union in your example. And if it's anonymous then you
>> have no name to apply sizeof to.
>
> Type name != member name.  It is still an anonymous union.

It is not. My reading of the above code snippet is that there is a 
nested function_buffer_members union type definition. There is no member 
of that type in function_buffer, and since it is not an anonymous union, 
its members are not "inlined" into the containing scope (i.e. the 
function_buffer union). The mutable keyword is illegal in that context.