On Tue, 2014-02-18 at 22:40 +0100, Peter Zijlstra wrote: > On Tue, Feb 18, 2014 at 10:21:56PM +0100, Torvald Riegel wrote: > > Well, that's how atomics that aren't volatile are defined in the > > standard. I can see that you want something else too, but that doesn't > > mean that the other thing is broken. > > Well that other thing depends on being able to see the entire program at > compile time. PaulMck already listed various ways in which this is > not feasible even for normal userspace code. > > In particular; DSOs and JITs were mentioned.
No it doesn't depend on whole-program analysis being possible. Because if it isn't, then a correct compiler will just not do certain optimizations simply because it can't prove properties required for the optimization to hold. With the exception of access to objects via magic numbers (e.g., fixed and known addresses (see my reply to Paul), which are outside of the semantics specified in the standard), I don't see a correctness problem here.
