[Development] Changing container privates again

[João Abecasis]

Thiago Macieira wrote:
>> Following Olivier's suggestion I think it might be beneficial to have alloc
>> unconditionally in the base class, even if it is not being used at times.
>> If nothing else, it saves padding. Additionally, deleter function and token
>> would be more generally useful if they can be used with the alloc member.
> 
> Yes, if we move the alloc member to the main struct, then it will simply 
> occupy the space currently used for padding. The total overhead for an 
> allocation would be 24 bytes on 64-bit systems. Since glibc's allocator is 16-
> byte aligned, this means our data is always 8 bytes off.
> 
> In my opinion, that's actually worse than having a larger header.

But that's what we currently have and wouldn't change with you suggestion above, right?

Would it be worth to set the minimum alignment for the data as 16-bytes, at the expense of padding we explicitly add in QArrayData::allocate? (Since this decision can be done inside that function it would have no impact on ABI)

Cheers,


João