Gabriel Dos Reis <[EMAIL PROTECTED]> writes: | Richard Henderson <[EMAIL PROTECTED]> writes: | | | 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? | | My understanding what that some compilers may do "speculative register | promotion". | (I think the example given by Hans actually involved lock()/unlock() | not acquire/release).
Jason (seating next to me) just pointed out to me that "volatile" did not appear in the example shown by Hans -- as I mistakenly thought. So ignore my message. Sorry for the confusion. -- Gaby
