This patch implements the forwarding to frozen C++03 headers as
discussed in
https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc. In the
RFC, we initially proposed selecting the right headers from the Clang
driver, however consensus seemed to steer towards handling this in the
library itself. This patch implements that direction.
At a high level, the changes basically amount to making each public
header look like this:
```
// inside <vector>
#ifdef _LIBCPP_CXX03_LANG
# include <__cxx03/vector>
#else
// normal <vector> content
#endif
```
In most cases, public headers are simple umbrella headers so there isn't
much code in the #else branch. In other cases, the #else branch contains
the actual implementation of the header.
This PR deprecates `<ccomplex>`, `<cstdbool>`, `<ctgmath>`, and
`<ciso646>` in C++17 and "removes" them in C++20 by special deprecation
warnings.
`<cstdalign>` is previously missing. This PR also tries to add them, and
then deprecates and "removes" `<cstdalign>`.
Papers:
- https://wg21.link/P0063R3
- https://wg21.link/P0619R4Closes#99985.
---------
Co-authored-by: Louis Dionne <ldionne.2@gmail.com>
Some platforms don't provide all C library headers. In practice, libc++
only requires a few C library headers to exist, and only a few functions
on those headers. Missing functions that libc++ doesn't need for its own
implementation are handled properly by the using_if_exists attribute,
however a missing header is currently a hard error when we try to
do #include_next.
This patch should make libc++ more flexible on platforms that do not
provide C headers that libc++ doesn't actually require for its own
implementation. The only downside is that it may move some errors from
the #include_next point to later in the compilation if we actually try
to use something that isn't provided, which could be somewhat confusing.
However, these errors should be caught by folks trying to port libc++
over to a new platform (when running the libc++ test suite), not by end
users.
NOTE: This is a reapplicaton of 226409, which was reverted in 674729813
because it broke the build. The issue has now been fixed with
https://reviews.llvm.org/D138062.
Differential Revision: https://reviews.llvm.org/D136683
Some platforms don't provide all C library headers. In practice, libc++
only requires a few C library headers to exist, and only a few functions
on those headers. Missing functions that libc++ doesn't need for its own
implementation are handled properly by the using_if_exists attribute,
however a missing header is currently a hard error when we try to
do #include_next.
This patch should make libc++ more flexible on platforms that do not
provide C headers that libc++ doesn't actually require for its own
implementation. The only downside is that it may move some errors from
the #include_next point to later in the compilation if we actually try
to use something that isn't provided, which could be somewhat confusing.
However, these errors should be caught by folks trying to port libc++
over to a new platform (when running the libc++ test suite), not by end
users.
Differential Revision: https://reviews.llvm.org/D136683
We've stopped doing it in libc++ for a while now because these names
would end up rotting as we move things around and copy/paste stuff.
This cleans up all the existing files so as to stop the spreading
as people copy-paste headers around.
to reflect the new license. These used slightly different spellings that
defeated my regular expressions.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351648
