Re: [boost] atomic_ops library

From: Roland Schwarz (roland.schwarz_at_[hidden])
Date: 2006-11-12 10:37:21

Neal Becker wrote:
> Perhaps of some interest:
> 
> http://www.hpl.hp.com/research/linux/atomic_ops/

You might also look at:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2047.html

Hans Boehm's proposal seems to build upon this library you
were pointing at. (Not surprisingly, since he is the author of it.)

I am currently trying to prototype something along his proposal, to
see how far I can get.

Until now I have found some loopholes I am trying to figure out.

E.g.:

atomic<int> i1;
atomic<int> i2;

i1 = 42; // assignment is atomic
i1 = i2; // assignment is not atomic !

--> should atomics be allowed to be copyable?

I would say: yes and no. I would expect that the value can be
transfered, but it should be semantically equivalent to:

int t;
t = i1;
i2 = t;

The current proposal as far as I can see does not address this
issue. It allows for a bitwise copy by the compiler.

Or :

struct a4 {
     char c[4];
};

atomic<a4> a;

Shall this be possible, if a4 is POD and has same alignment and
size of a type that can be manipulated atomically?
If yes, how can it be implemented?

If you like we can discuss this further.

Roland