Re: [boost] determining if an object is faster to pass by value or const reference

From: Alex MDC (alex.mdc_at_[hidden])
Date: 2008-07-03 20:35:17

Have a look at the Call Traits library, in particular "param_type".

Alex

2008/7/4 Michael Marcin <mike.marcin_at_[hidden]>:

> In general noone would write a function that took an int by const reference
> because doing so doesn't make sense from a performance standpoint. However
> often times we pass these trivial types to functions generically written to
> take const T&.
>
> It seems like type traits would make it simple to overload based on this
> convention. However I don't see a type trait that is fit for this use case.
>
> The has_trivial_copy trait would seem promising but it could return true
> for large pod objects that you wouldn't want to copy.
>
> The is_scalar trait seems promising but it will return false for
> lightweight user defined types and be suboptimal.
>
> Using has_trivial_copy together with some sizeof limit seems promising but
> a bit hand wavy.
>
> Is there a trait designed for this use case I'm overlooking?
>
> Thanks,
>
> Michael Marcin
>
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