[Bug libstdc++/54005] Use __atomic_always_lock_free in libstdc++ is_lock_free instead of __atomic_is_lock_free

[amacleod at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54005

--- Comment #5 from Andrew Macleod <amacleod at redhat dot com> 2012-08-14 03:27:28 UTC ---
huh, somehow this got submitted before I finished. :-P

For libstdc++, the macros SHOULD use __atomic_always_lock_free() since they are
intended to be used in #ifdef's and such and we want those resolved at compile
time for use with compiler sequences.   

The is_lock_free() method should continue to call the __atomic_is_lock_free().
That question may not be answerable without asking whatever libatomic is linked
into the executable.  Just because the compiler doesn't know a type is lock
free doesn't mean the library doesn't have a lock free implementation.