[cpp-threads] Relaxed reload example

[Herb Sutter]

> DEC Alpha would in fact permit this outcome.

Why doesn't that surprise me? :-)

> I am not aware of any other CPU that permits this outcome.

I was more specifically wondering what the draft C++MM said about it. At least one subquestion would be whether relaxed reads can be replicated (by the CPU, or the compiler, etc.). Not sure if there are other ways the result could happen.

Herb