[libcxx-commits] [PATCH] D115995: [libcxx] Add deprecation notices to macros deprecated in P0883R2

[Arthur O'Dwyer via Phabricator via libcxx-commits]

Quuxplusone requested changes to this revision.
Quuxplusone added a comment.
This revision now requires changes to proceed.

LGTM mod important comment.



================
Comment at: libcxx/include/atomic:2703
+#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_DISABLE_DEPRECATION_WARNINGS)
+#pragma clang deprecated(ATOMIC_FLAG_INIT)
+#pragma clang deprecated(ATOMIC_VAR_INIT)
----------------
tambre wrote:
> Separate macro deprecation macros didn't seem worth it as this is likely to be the only place we'd use them for a while. Since other compilers should simply ignore these guarding these shouldn't be necessary either.
Sadly "other compilers" includes "old Clang."
```
atomic:2703:15: error: unknown pragma ignored [-Werror,-Wunknown-pragmas]
#pragma clang deprecated(ATOMIC_FLAG_INIT)
              ^
```
So this should be guarded somehow.
Today, if I grepped correctly, libcxx has zero instances of //any// `pragma clang` or `pragma GCC` except for `pragma {clang,GCC} diagnostic`. So we're unlikely to have any precedent for how to deal with conditionally supported pragmas. I suggest just this:
```
#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_DISABLE_DEPRECATION_WARNINGS)
# if defined(_LIBCPP_CLANG_VER) && _LIBCPP_CLANG_VER >= 1400
#  pragma clang deprecated ~~~
# endif
#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_DISABLE_DEPRECATION_WARNINGS)
```
(Separating the "semantic, why" from the "compiler-specific, how" — but really I did that only so I wouldn't have to deal with a super-long line. ;))


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D115995/new/

https://reviews.llvm.org/D115995