Works towards P0619R4/#99985.

- std::uncaught_exception was not previously deprecated. This patch
  deprecates it since C++17 as per N4259. std::uncaught_exceptions is
  used instead as libc++ unconditionally provides this function.

- _LIBCPP_ENABLE_CXX20_REMOVED_UNCAUGHT_EXCEPTION restores
  std::uncaught_exception.

- As a drive-by, this patch updates the C++20 status page to 
  explain that D.11 is already done, since it was done in 
  578d09c1b195d859ca7e62840ff6bb83421a77b5.

This patch runs clang-format on all of libcxx/include and libcxx/src, in
accordance with the RFC discussed at [1]. Follow-up patches will format
the benchmarks, the test suite and remaining parts of the code. I'm
splitting this one into its own patch so the diff is a bit easier to
review.

This patch was generated with:

   find libcxx/include libcxx/src -type f \
      | grep -v 'module.modulemap.in' \
      | grep -v 'CMakeLists.txt' \
      | grep -v 'README.txt' \
      | grep -v 'libcxx.imp' \
      | grep -v '__config_site.in' \
      | xargs clang-format -i

A Git merge driver is available in libcxx/utils/clang-format-merge-driver.sh
to help resolve merge and rebase issues across these formatting changes.

[1]: https://discourse.llvm.org/t/rfc-clang-formatting-all-of-libc-once-and-for-all

Our best guess is that the two syntaxes should have exactly equivalent
effects, so, let's be consistent with what we do in libcxx/include/.

I've left `#include "include/x.h"` and `#include "../y.h"` alone
because I'm less sure that they're interchangeable, and they aren't
inconsistent with libcxx/include/ because libcxx/include/ never
does that kind of thing.

Also, use the `_LIBCPP_PUSH_MACROS/POP_MACROS` dance for `<__undef_macros>`,
even though it's technically unnecessary in a standalone .cpp file,
just so we have consistently one way to do it.

Differential Revision: https://reviews.llvm.org/D119561

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.

Summary:
In a bunch of places, we used to check whether LIBCXX_BUILDING_LIBCXXABI
is defined OR we're building for an Apple platform. This used to
be necessary in a time when Apple's build script did NOT define
LIBCXX_BUILDING_LIBCXXABI. However this is not relevant anymore
since Apple's build does define LIBCXX_BUILDING_LIBCXXABI.

Reviewers: EricWF

Subscribers: christof, jkorous, dexonsmith, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D60842

llvm-svn: 358988

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

Summary:
This patch replaces __sync_* with __libcpp_atomic_* and adds a wrapper
function for __atomic_exchange to support _LIBCPP_HAS_NO_THREADS.

Reviewers: EricWF, jroelofs, mclow.lists, compnerd

Reviewed By: EricWF, compnerd

Subscribers: compnerd, efriedma, cfe-commits, joerg, llvm-commits

Differential Revision: https://reviews.llvm.org/D35235

llvm-svn: 313694

Summary:
This patch implements exception_ptr on Windows using the `__ExceptionPtrFoo` functions provided by MSVC.

The `__ExceptionPtrFoo` functions are defined inside the C++ standard library, `msvcprt`, which is unfortunate because it requires libc++ to link to the MSVC STL. However this doesn't seem to cause any immediate problems. However to be safe I kept all usages within the libc++ dylib so that user programs wouldn't have to link to MSVCPRT as well.

Note there are still 2 outstanding exception_ptr/nested_exception test failures.

* `current_exception.pass.cpp` needs to be rewritten for the Windows exception_ptr semantics which copy the exception every time.
* `rethrow_if_nested.pass.cpp` need investigation. It hits a stack overflow, likely from recursion.

This patch also gets most of the `<future>` tests passing as well.

Reviewers: mclow.lists, compnerd, bcraig, rmaprath, majnemer, BillyONeal, STL_MSFT

Subscribers: mgorny, cfe-commits

Differential Revision: https://reviews.llvm.org/D32927

llvm-svn: 302393

This recommits r294707 with additional fixes. The main difference is
libc++ now correctly builds without any ABI library.

exception.cpp is a bloody mess. It's full of confusing #ifdef branches for
each different ABI library we support, and it's getting unmaintainable.

This patch breaks down exception.cpp into multiple different header files,
roughly one per implementation. Additionally it moves the definitions of
exceptions in new.cpp into the correct implementation header.

This patch also removes an unmaintained libc++abi configuration.
This configuration may still be used by Apple internally but there
are no other possible users. If it turns out that Apple still uses
this configuration internally I will re-add it in a later commit.
See http://llvm.org/PR31904.

llvm-svn: 294730