While Boost.Atomic strives to implement the atomic operations from C++11 as faithfully as possible, there are a few limitations that cannot be lifted without compiler support:
results in undefined behavior: This means that any class containing
a constructor, destructor, virtual methods or access control specifications
is not a valid argument in C++98. C++11 relaxes this slightly by allowing
"trivial" classes containing only empty constructors. Advise: Use only POD types.
only affects computationally-dependent operations, but in general there
is nothing preventing a compiler from transforming a computation dependency
into a control dependency. A C++11 compiler would be forbidden from such
a transformation. Advise: Use
memory_order_consume only in conjunction
with pointer values, as the compiler cannot speculate and transform these
into control dependencies.
memory_order_release need to restrain
reordering of memory operations only in one direction. Since there is no
way to express this constraint to the compiler, these act as "full
compiler barriers" in this implementation. In corner cases this may
result in a less efficient code than a C++11 compiler could generate.
in shared memory only works correctly, if
atomic<T>::is_lock_free() == true.