jfb added a subscriber: jfb.
jfb added a comment.
Awesome, thanks for doing this!
Should this be a warning or an error?
================
Comment at: include/atomic:581
@@ +580,3 @@
+ || __f == memory_order_acq_rel, ""))) \
+ __attribute__ ((__unavailable__("memory order argument to atomic operation
is invalid")))
+#endif
----------------
This isn't checking for the following requirement from the standard:
> The failure argument shall be no stronger than the success argument.
I think that's OK because I intend to remove that requirement from C++ :)
Should we nonetheless enforce the requirement until the standard drops it? If
so, "stronger" isn't well defined by the standard, details here:
https://github.com/jfbastien/papers/blob/master/source/D0418r1.bs
================
Comment at: test/libcxx/atomics/diagnose_invalid_memory_order.fail.cpp:30
@@ +29,3 @@
+ vx.load(std::memory_order_release); // expected-error {{operation is
invalid}}
+ vx.load(std::memory_order_acq_rel); // expected-error {{operation is
invalid}}
+ }
----------------
Could you test that the other memory orders don't have any diagnostic (here and
below).
================
Comment at: test/libcxx/atomics/diagnose_invalid_memory_order.fail.cpp:55
@@ +54,3 @@
+ }
+ // compare exchange weak
+ {
----------------
For cmpxchg (weak and strong), should you also test the version with only a
`success` ordering? The `failure` one is auto-generated from `success`, but it
would be good to know that it never generates a diagnostic.
https://reviews.llvm.org/D22557
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