Implement P2401 which adds a `noexcept` specification to
`std::exchange`. Treated as a defect fix which is the motivation for
applying this change to all standards mode rather than just C++23 or
later as the paper suggests.

Reviewed By: Quuxplusone, Mordante, #libc

Differential Revision: https://reviews.llvm.org/D111481

Implement P2251 which requires `span` and `basic_string_view` to be
trivially copyable. They already are - this just adds tests to bind that
behavior.

Reviewed By: ldionne, Quuxplusone, Mordante, #libc

Differential Revision: https://reviews.llvm.org/D111197

Due to reported failures in a local build.

FAIL: Something is wrong in the test framework.
Converting character sets: Invalid argument.

(was enabled in https://reviews.llvm.org/D111138)

Differential Revision: https://reviews.llvm.org/D110735

Replace `TEST_NOEXCEPT_FALSE` directly with `noexcept(false)` in
optional hash test which is only run in C++17 or later.
`TEST_NOEXCEPT_FALSE` is only useful in C++03 context where `noexcept`
isn't supported by clang. `TEST_NOEXCEPT_FALSE` now only has one remaining use
in `hash_unique_ptr.pass.cpp`.

There is an empty `namespace std` in `type_traits` which was originally
used when `std::byte` was added in
c97d8aa8. At some point, the bitwise operators
on `std::byte` got relocated but this empty namespace was left around.
Remove it.

Reviewed By: Quuxplusone, Mordante, #libc

Differential Revision: https://reviews.llvm.org/D111512

There is a stray tab character in a comment block. Replace the tab
character with a space for consistency with other comments.

`{ind.move.subsumption.compile.pass.cpp}` was accidentally commited in
https://reviews.llvm.org/D102639. Per the conversation on Discord in

As suggested in D110573 land the rename part separately.

Updated based on recent commits.

Implement parts of P1614, including three-way comparison for tuples, and expand testing.

Reviewed By: ldionne, Mordante, #libc

Differential Revision: https://reviews.llvm.org/D108250

Implement https://wg21.link/p1394 which allows span to be constructible
from any contiguous forwarding-range that has a compatible element type.

Fixes https://bugs.llvm.org/show_bug.cgi?id=51443

Reviewed By: ldionne, Quuxplusone, #libc

Differential Revision: https://reviews.llvm.org/D110503

Update the status with the approved papers and LWG-issues in the October 2021 plenary.

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D111166

This was missed in D95972 / 7c49052b,
as this codepath isn't exercised by CI yet.

Differential Revision: https://reviews.llvm.org/D111292

While looking at the review comments in D103765 there was an oddity in
the tests for the following functions:
- atomic_fetch_add
- atomic_fetch_add_explicit
- atomic_fetch_sub
- atomic_fetch_sub_explicit

Libc++ allows usage of
`atomic_fetch_add<int>(atomic<int*>*, atomic<int*>::difference_type);`
MSVC and GCC reject this code: https://godbolt.org/z/9d8WzohbE

This makes the atomic `fetch(add|sub).*` Standard conforming and removes the non-conforming extensions.

Fixes PR47908

Reviewed By: ldionne, #libc

Differential Revision: https://reviews.llvm.org/D103983

It is not used anywhere anymore since we're using the new runtimes build
in <monorepo>/runtimes now, so we can remove all traces of this build.

Differential Revision: https://reviews.llvm.org/D111351

When we recently started using DYLD_LIBRARY_PATH to run the test suite
on the Apple/System configuration of the library, the -fno-exceptions
variant started failing.

It started failing because under that configuration, libc++abi.dylib
doesn't provide support for exceptions. For example, it doesn't provide
some symbols such as ___gxx_personality_v0. Now, the problem is that
when the test suite is run with DYLD_LIBRARY_PATH, /usr/lib/libobjc.dylib
uses the just-built libc++abi.dylib, which doesn't support exceptions,
and we end up with an unresolved reference to ___gxx_personality_v0.

Previously, using -Wl,-rpath,path/to/lib, we would be loading both
/usr/lib/libc++abi.dylib and <just-built>/lib/libc++abi.dylib.
/usr/lib/libobjc.dylib would use the system libc++abi.dylib, which
contains support for exceptions, and the tests would be using the
just-built one, which doesn't.

Disentangling that led me to believe that we shouldn't try to test this
configuration where libc++/libc++abi are built as system libraries, but
where they don't support exceptions, since that just doesn't make any
sense. Doing so is like trying to build libc++/libc++abi and test it as
a system library after performing an ABI break -- of course nothing is
going to work.

For that reason, I am removing this configuration. Note that we could
still test the library on macOS without exceptions if we wanted, only
we wouldn't be building it as a system library. This patch doesn't add
that because we already have a -fno-exceptions CI job on Linux.

Differential Revision: https://reviews.llvm.org/D111349

Differential Revision: https://reviews.llvm.org/D111329

Vendors take libc++ and ship it in various ways. Some vendors might
ship it differently from what upstream LLVM does, i.e. the install
location might be different, some ABI properties might differ, etc.

In the past few years, I've come across several instances where
having a place to test some of these properties would have been
incredibly useful. I also just got bitten by the lack of tests
of that kind, so I'm adding some now.

The tests added by this commit for Apple platforms have numerous
TODOs that capture discrepancies between the upstream LLVM CMake
and the slightly-modified build we perform internally to produce
Apple's system libc++. In the future, the goal would be to upstream
all those differences so that it's possible to build a faithful
Apple system libc++ with the upstream LLVM sources only.

But this isn't only useful for Apple - this lays out the path for
any vendor being able to add their own checks (either upstream or
downstream) to libc++.

This is a re-application of 9892d164, which was reverted in 138dc271
because it broke the build. The issue was that we didn't apply the required
changes to libunwind and our CI didn't notice it because we were not
running the libunwind tests. This has been fixed now, and we're running
the libunwind tests in CI now too.

Differential Revision: https://reviews.llvm.org/D110736

Replace `&__rhs` with `_VSTD::addressof(__rhs)` to guard against ADL hijacking
of `operator&` in `operator=`. Thanks to @CaseyCarter for bringing it to our
attention.

Similar issues with hijacking `operator&` still exist, they will be
addressed separately.

Reviewed By: #libc, Quuxplusone, ldionne

Differential Revision: https://reviews.llvm.org/D110852

The script was recently updated to generate different output. This
breaks the CI due the patches which used the old version of the script.

Implements the formatter for Boolean types.
[format.formatter.spec]/2.3
For each charT, for each cv-unqualified arithmetic type ArithmeticT other
than char, wchar_t, char8_t, char16_t, or char32_t, a specialization
```
  template<> struct formatter<ArithmeticT, charT>;
```
This removes the stub implemented in D96664.

Implements parts of:
- P0645 Text Formatting
- P1652 Printf corner cases in std::format

Completes:
- P1868 width: clarifying units of width and precision in std::format

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D103670

Implements the formatter for all fundamental integer types.
[format.formatter.spec]/2.1
The specializations
```
  template<> struct formatter<char, char>;
  template<> struct formatter<char, wchar_t>;
  template<> struct formatter<wchar_t, wchar_t>;
```
This removes the stub implemented in D96664.

Implements parts of:
- P0645 Text Formatting

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D103466

Implements the formatter for all fundamental integer types
(except `char`, `wchar_t`, and `bool`).
[format.formatter.spec]/2.3
For each charT, for each cv-unqualified arithmetic type ArithmeticT other
than char, wchar_t, char8_t, char16_t, or char32_t, a specialization
```
  template<> struct formatter<ArithmeticT, charT>;
```
This removes the stub implemented in D96664.

As an extension it adds partial support for 128-bit integer types.

Implements parts of:
- P0645 Text Formatting
- P1652 Printf corner cases in std::format

Completes:
- LWG-3248 #b, #B, #o, #x, and #X presentation types misformat negative numbers

Reviewed By: #libc, ldionne, vitaut

Differential Revision: https://reviews.llvm.org/D103433

Implements the formatter for all string types.
[format.formatter.spec]/2.2
For each charT, the string type specializations
```
  template<> struct formatter<charT*, charT>;
  template<> struct formatter<const charT*, charT>;
  template<size_t N> struct formatter<const charT[N], charT>;
  template<class traits, class Allocator>
    struct formatter<basic_string<charT, traits, Allocator>, charT>;
  template<class traits>
    struct formatter<basic_string_view<charT, traits>, charT>;
```
This removes the stub implemented in D96664.

Implements parts of:
- P0645 Text Formatting
- P1868 width: clarifying units of width and precision in std::format

Reviewed By: #libc, ldionne, vitaut

Differential Revision: https://reviews.llvm.org/D103425

Missing "global" meant that we set a local "has_run_tests"
so the global was False by the time everything has run.

If you don't have ptrace permissions this test will fail to run
silently, this adds a check for that and anything else that
might do similar things.

The output will now be:
```
FAILED test program did not run correctly, check gdb warnings

/usr/bin/gdb: warning: Couldn't determine a path for the index cache
directory.
No symbol table is loaded.  Use the "file" command.
warning: Error disabling address space randomization: Operation not
permitted
warning: Could not trace the inferior process.
warning: ptrace: Operation not permitted

error: command failed with exit status: 255
```

We already have a feature to check for a compatible python enabled
gdb, so I think it's reasonable to check for this at test runtime.

Note that this is different to the catch all at the end of the test
script. That would be a case where you can trace but something else
made it stop mid way that wasn't our test breakpoints.

Reviewed By: saugustine

Differential Revision: https://reviews.llvm.org/D110936

When the locale is not some UTF-8 these tests fail.
(different results for python2 linked gdbs vs. python3
but same issue)

Setting the locale just for the test works around this.
By default Ubuntu comes with just C.UTF-8. I've chosen
to use en_US.UTF-8 instead given that my Mac doesn't have
the former and there's a slim chance this test might run there.

This also enables the u16string tests which are now passing.

Reviewed By: #libc, ldionne, saugustine

Differential Revision: https://reviews.llvm.org/D111138

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D111235

The unique (ha!) thing about this range type is that it's move-only.
Its contiguity is unsurprising (most of our test ranges are contiguous).
Discussed in D111231 but committed separately for clarity.

If you have a `begin() const` member, you don't need a `begin()` member
unless you want it to do something different (e.g. have a different return
type). So in general, //view// types don't need `begin()` non-const members.

Also, static_assert some things about the types in "types.h", so that we
don't accidentally break those properties under refactoring.

Differential Revision: https://reviews.llvm.org/D111231

Priorities below 101 are reserved for the implementation, so that's what
we should be using here. That is unfortunately only supported on more
recent versions of Clang. See https://reviews.llvm.org/D31413 for details.

Differential Revision: https://reviews.llvm.org/D95972

Reduce code duplication by sharing most of the test suite setup across
the different from-scratch configs.

Differential Revision: https://reviews.llvm.org/D111196

Implement P1391 (https://wg21.link/p1391) which allows
`std::string_view` to be constructible from any contiguous range of
characters.

Note that a different paper (http://wg21.link/P1989) handles the generic
range constructor for `std::string_view`.

Reviewed By: ldionne, Quuxplusone, Mordante, #libc

Differential Revision: https://reviews.llvm.org/D110718

We should arguably have always been doing that. The state of libunwind
is quite sad, so this commit adds several XFAILs to make the CI pass.
We need to investigate why so many tests are not passing in some
configurations, but I'll defer that to folks who actually work on
libunwind for lack of bandwidth.

Differential Revision: https://reviews.llvm.org/D110872

In basic_string and vector, we've been encapsulating all exception
throwing code paths in helper functions of a base class, which are defined
in the compiled library. For example, __vector_base_common defines two
methods, __throw_length_error() and __throw_out_of_range(), and the class
is externally instantiated in the library. This was done a long time ago,
but after investigating, I believe the goal of the current design was to:

1. Encapsulate the code to throw an exception (which is non-trivial) in
   an externally-defined function so that the important code paths that
   call it (e.g. vector::at) are free from that code. Basically, the
   intent is for the "hot" code path to contain a single conditional jump
   (based on checking the error condition) to an externally-defined function,
   which handles all the exception-throwing business.

2. Avoid defining this exception-throwing function once per instantiation
   of the class template. In other words, we want a single copy of
   __throw_length_error even if we have vector<int>, vector<char>, etc.

3. Encapsulate the passing of the container-specific string (i.e. "vector"
   and "basic_string") to the underlying exception-throwing function
   so that object files don't contain those duplicated string literals.
   For example, we'd like to have a single "vector" string literal for
   passing to `std::__throw_length_error` in the library, instead of
   having one per translation unit.

However, the way this is achieved right now has two problems:

- Using a base class and exporting it is really weird - I've been confused
  about this ever since I first saw it. It's just a really unusual way of
  achieving the above goals. Also, it's made even worse by the fact that
  the definitions of __throw_length_error and __throw_out_of_range appear
  in the headers despite always being intended to be defined in the compiled
  library (via the extern template instantiation).

- We end up exporting those functions as weak symbols, which isn't great
  for load times. Instead, it would be better to export those as strong
  symbols from the library.

This patch fixes those issues while retaining ABI compatibility (e.g. we
still export the exact same symbols as before). Note that we need to
keep the base classes as-is to avoid breaking the ABI of someone who
might inherit from std::basic_string or std::vector.

Differential Revision: https://reviews.llvm.org/D111173

This is less brittle than hand-picking the substitutions that we
pass to the test, since a config could theorically use non-base
substitutions as well (such as defining %{flags} in terms of another
substitution like %{include}).

Also, print the decoded substitutions, which makes it much easier
to debug the test when it fails.

Differential Revision: https://reviews.llvm.org/D111179

That makes it possible to store that value in a CMake cache if needed.

Differential Revision: https://reviews.llvm.org/D110843

This was most likely an oversight, since we're running all other jobs on
the new configs.

Differential Revision: https://reviews.llvm.org/D111168