Re: [boost] [optional] memory use for optional refs and ptrs

Subject: Re: [boost] [optional] memory use for optional refs and ptrs
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2010-10-06 08:26:30

Sebastian Redl wrote:
> On 06.10.2010 14:09, Rutger ter Borg wrote:
> > On 2010-10-06 13:11, Stewart, Robert wrote:
> >
> >> (I haven't looked, but I do hope that the bool follows the
> >> optional value to reduce padding overhead.)
> >
> > It doesn't, the boolean is followed by the optional value (see
> > boost/optional/optional.hpp lines 447-448).
>
> I really don't think it makes a difference. Unless you're using
> compiler-specific packing instructions, the size of a struct
> will always be a multiple of the largest alignment of any of its
> subobjects. In other words, no matter where you place the bool,
> it will take as much space as the alignment of the value.

When the bool follows the value, it can occupy otherwise unused padding between data members.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer, Core Software      using std::disclaimer;
Susquehanna International Group, LLP  http://www.sig.com

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