Alexander Terekhov wrote:
Peter Dimov wrote:
Eh, __asm__ is no better than a volatile. Both are non-portable.
Except that volatile has defined semantics (both must die too in favor of threads and exceptions) that has really nothing to do with multiple threads and msync. I mean "decoration function" for sig_atomic_t statics and setjmp/longjmp()-sensitive locals in C and POSIX (C++ aside for a moment).
Yes, but in this case threads are not a problem (we're in release, destroying the last remaining shared_ptr; if we read weak_count_ == 1, no other thread can be creating/destroying weak pointers because of basic guarantee). Msync is not a problem because we've just acquired in the decrement. Now that I think of it, compiler value propagation isn't a problem either because of the "memory" clobber on the decrement. So the cast to volatile can be removed. void release() // nothrow { if( atomic_exchange_and_add( &use_count_, -1 ) == 1 ) { dispose(); if( weak_count_ == 1 ) // no weak ptrs { destroy(); } else { weak_release(); } } }