[cpp-threads] seq_cst compare_exchange and store-load fencing

[Alexander Terekhov]

compare_exchange performs both load and (conditional) store. This
leads to questions regarding store-load fencing for compare_exchange
in seq_cst mode:

Q1) Does it provide store-load fencing in the case of

   A.store(relaxed|release) ... B.compare_exchange(..., seq_cst)

regarding A's store and B's load (in either success or failure case of
B's compare_exchange)?

Q2) Does it provide store-load fencing in the case of

   B.compare_exchange(..., seq_cst) ... C.load(relaxed|acquire)

regarding B's store and C's load (in success case of B's compare_exchange)?

Under simple interpretation of "seq_cst" meaning "fully-fenced" the
answer to both questions is "yes"...

Do you agree with the same outcome under the proposed C/C++ memory model?

What is your reasoning in case you disagree?

TIA.

regards,
alexander.