[libcxx-commits] [PATCH] D58201: Make std::memory_order an enum class (P0439R0)

[JF Bastien via Phabricator via libcxx-commits]

jfb added inline comments.


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Comment at: include/atomic:603
+
+#endif
 
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EricWF wrote:
> jwakely wrote:
> > zoecarver wrote:
> > > jfb wrote:
> > > > jwakely wrote:
> > > > > jfb wrote:
> > > > > > I think you want to keep the old `typedef enum memory_order` before C++20, and only enable the new thing in C++20 and later.
> > > > > That's what we did for libstdc++.
> > > > You did what I'm suggesting, or what @zoecarver did? 🤔
> > > Changing how `memory_order ` is defined changes how some of the code below is written -- if it is defined differently for different version then the code below also needs to be changed for different versions (actually a `static_cast` would work in both cases but it is only necessary in the latter). 
> > We did what you suggested: keeping it unchanged for C++11/14/17 and only making it a scoped enumeration (and adding the new enumerators) for C++20.
> > 
> > And we cast to `int` unconditionally, because as zoecarver said, that always works, even if the cast is redundant for C++11/14/17.
> Although I know it's not conforming. I would prefer to make it a scoped enum retroactively. In the past 3 months, I've had 3 separate users get burned by the implicit conversion to int. 
> 
I'd rather not do this: WG21 would have made the paper a defect and applied its resolution retroactively. I think we should conform here, and we could instead teach clang-tidy to catch this issue.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D58201/new/

https://reviews.llvm.org/D58201