[boost] Re: Lock unification

From: Eric Niebler (eric_at_[hidden])
Date: 2004-07-15 18:50:52

Eric Niebler wrote:
> David Abrahams wrote:
>> BTW, it just occurred to me that
>>
>>      timed_lock(m, 0)
>>
>> could potentially generate different code from
>>
>>      timed_lock(m, some_int)
>>
>> If we can detect literal zero... which I think is possible.
>>
>> What about:
>>
>>   scoped_lock l(m);               // block
>>   scoped_lock l(m, 0);            // try
>>   scoped_lock l(m, 33);           // timed
>>
>>   scoped_lock l(m, deferred);     // deferred   scoped_lock 
>> l(deferred(m));     // alternate
>>  
>> ??
>>
> 
> Interesting. That's workable.
> 

On second thought, I think it's too subtle. You can detect literal zero, 
but you can't detect (at compile-time) an int with a value of zero. I'm 
not comfortable with this:

   scoped_lock l(m, 0);

meaning something different than:

   int t = 0;
   scoped_lock l(m, t);

Perhaps it's really OK because the effect is the same, but the fact that 
they would execute different code paths sets off bells in my head.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com