Optimization of conditional access to globals: thread-unsafe?

[Ian Lance Taylor]

Tomash Brechko <tomash.brechko@gmail.com> writes:

>   - the compiler should not introduce speculative stores to the shared
>     objects.  This is what my original question was about.  I haven't
>     read all the papers yet, so one thing is still unclear to me: it
>     seems like atomic variables will be annotated as such
>     (atomic<int>).  But I found no proposal for annotation of
>     non-atomic objects that are protected by the ordinary locks (like
>     mutexes).  Will the compiler be forbiden to do all speculative
>     stores, or how will it recognize shared objects as such?

In practice, gcc will provide a variable attribute to mark the
variable as atomic.

The language standard does not forbid speculative stores to non-atomic
objects.

Ian