PFS_atomic class contains wrappers around my_atomic_* operations, which
are macros to GNU atomic operations (__atomic_*). Due to different
implementations of compilers, clang may encounter errors when compiling
on x86_32 architecture.
The following functions are replaced with C++ std::atomic type in
performance schema code base:
- PFS_atomic::store_*()
-> my_atomic_store*
-> __atomic_store_n()
=> std::atomic<T>::store()
- PFS_atomic::load_*()
-> my_atomic_load*
-> __atomic_load_n()
=> std::atomic<T>::load()
- PFS_atomic::add_*()
-> my_atomic_add*
-> __atomic_fetch_add()
=> std::atomic<T>::fetch_add()
- PFS_atomic::cas_*()
-> my_atomic_cas*
-> __atomic_compare_exchange_n()
=> std::atomic<T>::compare_exchange_strong()
and PFS_atomic class could be dropped completely.
Note that in the wrapper memory order passed to original GNU atomic
extensions are hard-coded as `__ATOMIC_SEQ_CST`, which is equivalent to
`std::memory_order_seq_cst` in C++, and is the default parameter for
std::atomic_* functions.
All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the
BSD-new license. I am contributing on behalf of my employer Amazon Web
Services.
