Re: [boost] [call-traits][param_type] why is sizeof(void*) chosen as the limit for passing by value?

Subject: Re: [boost] [call-traits][param_type] why is sizeof(void*) chosen as the limit for passing by value?
From: Jeffrey Hellrung (jhellrung_at_[hidden])
Date: 2010-04-15 12:45:43

Thorsten Ottosen wrote:
> Hi Boosters,
> 
> It seems to me that many other slightly larger types could benefit from 
> pass by value. For example, I rarely write
[...]
> With this in mind, I think we should consider changing the limit for
> param_type to sizeof(long double) or even 2*sizeof(int). Of course,
> we should only pass types with a trivial assignment operator by value.

By "trivial assignment operator", you really mean "trivial copy 
constructor", right?

You might want the "by-value size limit" to be platform dependent.  I 
can imagine that the limit for 64-bit systems could arguably be twice 
that for 32-bit systems.

Do you find the same optimization opportunity when passing a 
pair<float,float> by value as you did for passing a double by value?

- Jeff