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Re: Heads-up: volatile and C++
On Thu, Apr 14, 2005 at 11:30:20PM +0200, Jason Merrill wrote:
> Consider Double-Checked Locking
> (http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html).
> I used DCL with explicit memory barriers to implement thread-safe
> initialization of function-local statics
> (libstdc++-v3/libsupc++/guard.cc). The proposed change to volatile
> semantics would allow me to write it more simply, by just making the
> initialized flag volatile. Yes, volatile would be stronger than is
> actually necessary for DCLP, but I don't have to use it if I want
> finer-grained control over the synchronization.
Is there any reason to want to overload volatile for this, rather than
template<classname T> T acquire(T *ptr);
template<classname T> void release(T *ptr, T val);
where the functions do the indirection plus the memory ordering?
The biggest problem that I see is that C and C++ have been around far
too long, and there are far too many existing uses of "volatile" to be
redefining it now.
r~