Subj : Re: double-checked locking in C
To   : comp.programming.threads
From : David Schwartz
Date : Fri Jul 08 2005 07:32 pm


"Peter Dimov" <pdimov@gmail.com> wrote in message 
news:dan5la$5qg$1@domitilla.aioe.org...

> "As if" means that the compiler can achieve the required observable 
> behavior
> in whatever way it likes. If we assume an implementation where "volatile
> access" maps to a load instruction and "volatile write" maps to a store
> instruction, "as if" means that the compiler can elide or reorder all 
> other
> memory accesses and optimize out or overlap all nonvolatile objects as 
> long
> as the sequence of loads/stores corresponding to volatile accesses/writes
> remains in place.

    What is "the sequence of loads/stores"? In the CPU instruction stream? 
On the memory bus? To the cache? You are doing the same thing you said you 
could not do. How can the C standard specify where the sequence of 
loads/stores is to be observed?

    DS

.