Re: NSThread test failing

[David Chisnall]

On 12 Aug 2013, at 03:44, Doug Warren <address@hidden> wrote:

>     backgroundTid = 0;
>     [backThread performSelectorInBackground:@selector(run:) 
> withObject:backThread];
>     while(backgroundTid == 0)
>         sleep(1);
> 

I don't know if this is your issue, however your test relies on undefined 
behaviour.  In C99, backgroundTid is not volatile and so the compiler is 
entirely free to turn this into the equivalent of :

if (backgroundTid == 0)
        while (1) { sleep(1); }

I would expect this program never to terminate.  In C11, there is no 
happens-before relationship between the store and the load and so the same is 
allowed to happen but some other constraints are also in place.

David



-- Sent from my PDP-11