Remarks:
The macro
ATOMIC_FLAG_INIT is defined in such a way that
it can be used to initialize an object of type
atomic_flag
to the clear state
. The macro can be used in the form:
atomic_flag guard = ATOMIC_FLAG_INIT;
It is unspecified whether the macro can be used
in other initialization contexts
.For a complete static-duration object, that initialization shall be static
.