Jason Hise <chaos@ezequal.com> writes:
John Maddock wrote:
The mutex is unique to both the calling process and the call_once flag, but not the function pointer (however there should always be a one to one correspondence between the once-flag and the function pointer).
I should probably elaborate on my problem a little bit more. I wanted to create a function that makes a given call atomic, but doesn't enforce that the function be called only once. I thought I could do so by using a once_flag allocated on the stack immediately before invoking call_once, so the flag would always be reinitialized to BOOST_ONCE_INIT and call_once could just offer me it's atomic guarantees, but apparently that won't work. I guess I'll just have to find some place to put my own mutex where it can be constructed safely.
Calls through call_once are only atomic with respect to other calls that reference the same once_flag. If you want mutual exclusion, you need a shared mutex --- why not just create a function-local static mutex, lock it before your function call, and unlock it afterwards? Anthony -- Anthony Williams Software Developer Just Software Solutions Ltd http://www.justsoftwaresolutions.co.uk