[Redirect to gcc-help] Hi, On 04/29/2014 02:11 PM, Leo Ferres wrote: > Suppose the following C code. > > int t = __sync_fetch_and_add(&s->r, 1); > > s is a struct with member r, which is an volatile int. > > Is this an atomic operation, even if you include the indirection? In > other words, can a thread come between the dereferencing operation and > the atomic increment of another thread? Yes. Or rather, which dereference? There are two. > If so, is there a solution besides whileing with a compare and swap? > > What about stdatomic.h in C11, is there a way to do what I want there? You need an atomic operation which covers a CAS and a fetch. Unless you want to use transactional memory you're going to have to use a lock. Andrew.
