valid uses of shared

[Steven Schveighoffer]

On Fri, 08 Jun 2012 03:13:04 -0400, Dmitry Olshansky  
<dmitry.olsh at gmail.com> wrote:

> On 08.06.2012 8:03, Steven Schveighoffer wrote:

>> Yes, head stripping. I think it should be allowed. For instance, if you
>> wanted to read a shared double, and take the cosine of it, this should
>> be allowed:
>>
>> auto n = cos(sharedValue);
>
> what if it's a
> auto n = cos(sharedValues[k]); //type is shared(double) right?
>
> and somebody in the other thread is halfway through writing it?

At this point, I am not sure shared means synchronized or atomic.  It just  
means multiple threads can see it.  Perhaps you have already taken the  
lock that protects this variable.

My point is, the transfer of a shared type into an rvalue should strip the  
head-shared part of it *automatically*.  Especially since it would be  
illegal to store such a type on the stack (and quite literally, a shared  
rvalue makes no sense whatsoever), we don't want to force casting  
everywhere.

-Steve