aaron.ballman added inline comments.
================
Comment at: clang/lib/Headers/stddef.h:118-122
+#ifdef __cplusplus
+namespace std {
+typedef decltype(nullptr) nullptr_t;
+}
+using ::std::nullptr_t;
----------------
iana wrote:
> ldionne wrote:
> > iana wrote:
> > > aaron.ballman wrote:
> > > > Related:
> > > >
> > > > https://github.com/llvm/llvm-project/issues/37564
> > > > https://cplusplus.github.io/LWG/issue3484
> > > >
> > > > CC @ldionne
> > > I don't _think_ this change actually changes the way nullptr_t gets
> > > defined in C++, does it?
> > I think we absolutely don't want to touch `std::nullptr_t` from this
> > header. It's libc++'s responsibility to define that, and in fact we define
> > it in `std::__1`, so this is even an ABI break (or I guess it would be a
> > compiler error, not sure).
> I'm really not touching it though. All I did is move it from `__need_NULL` to
> `__need_nullptr_t`.
>
> The old behavior is that `std::nullptr_t` would only be touched if (no
> `__need_` macros were set or if `__need_NULL` was set), and (_MSC_EXTENSIONS
> and _NATIVE_NULLPTR_SUPPORTED are defined).
>
> The new behavior is that `std::nullptr_t` will only be touched if ((no
> `__need_` macros are set) and (_MSC_EXTENSIONS and _NATIVE_NULLPTR_SUPPORTED
> are defined)) or (the new `__need_nullptr_t` macro is set)
>
> So the only change is that C++ code that previously set `__need_NULL` will no
> longer get `std::nullptr_t`. @efriedma felt like that was a fine change.
Does libc++ provide the symbols for a freestanding compilation?
I was pointing out those links specifically because the C++ standard currently
says that stddef.h (the C standard library header) needs to provide a
definition of `std::nullptr_t`, but that LWG thinks that's perhaps not the
right way to do that and may be removing that requirement.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D157757/new/
https://reviews.llvm.org/D157757
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