Back in https://reviews.llvm.org/D109459, we stopped using the C++03
emulation for std::nullptr_t by default, which was an ABI break. We
still left a knob for users to turn it back on if they were broken by
the change, with a note that we would remove that knob after one release.
The time has now come to remove the knob and clean up the std::nullptr_t
emulation.
Differential Revision: https://reviews.llvm.org/D114786
Even if these comments have a benefit in .h files (for editors that
care about language but can't be configured to treat .h as C++ code),
they certainly have no benefit for files with the .cpp extension.
Discussed in D110794.
libc++ has started splicing standard library headers into much more
fine-grained content for maintainability. It's very likely that outdated
and naive tooling (some of which is outside of LLVM's scope) will
suggest users include things such as `<__algorithm/find.h>` instead of
`<algorithm>`, and Hyrum's law suggests that users will eventually begin
to rely on this without the help of tooling. As such, this commit
intends to protect users from themselves, by making it a hard error for
anyone outside of the standard library to include libc++ detail headers.
This is the first of four patches. Patch #2 will solve the problem for
pre-processor `#include`s; patches #3 and #4 will solve the problem for
`<__tree>` and `<__hash_table>` (since I've never touched the test cases
that are failing for these two, I want to split them out into their own
commits to be extra careful). Patch #5 will concern itself with
`<__threading_support>`, which intersects with libcxxabi (which I know
even less about).
Differential Revision: https://reviews.llvm.org/D105932
Louis Dionne