[libc++] Remove <tuple> from <variant> (#83183)

This moves a utility from `<tuple>` into an implementation detail header
and refactors the selection of the variant index type to use.

Fix EBO on std::optional and std::variant when targeting the MSVC ABI

Committing on behalf of davidben. Reviewed as D146190

Patch originally by Jan Dörrie in https://reviews.llvm.org/D120064. I've

Fix EBO on std::optional and std::variant when targeting the MSVC ABI

Committing on behalf of davidben. Reviewed as D146190

Patch originally by Jan Dörrie in https://reviews.llvm.org/D120064. I've just updated it to include tests, and update documentation that MSVC ABI is not stable.

In the current implementation both `std::optional` and `std::variant` don't perform the EBO on MSVC's ABI. This is because both classes inherit from multiple empty base classes, which breaks the EBO for MSVC. This patch fixes this issue by applying the `empty_bases` declspec attribute, which is already used to fix a similar issue for `std::tuple`.

See https://reviews.llvm.org/D120064 for discussion on MSVC ABI stability. From the discussion, libc++ doesn't have users that expect a stable ABI on MSVC. The fix is thus applied unconditionally to benefit more users. Documentation has been updated to reflect this.

Fixes https://github.com/llvm/llvm-project/issues/61095.

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[libc++] Qualifies size_t.

This has been done using the following command

find libcxx/test -type f -exec perl -pi -e 's|^([^/]+?)((?<!::)size_t)|\1std::\2|' \{} \;

And manually removed some fals

[libc++] Qualifies size_t.

This has been done using the following command

find libcxx/test -type f -exec perl -pi -e 's|^([^/]+?)((?<!::)size_t)|\1std::\2|' \{} \;

And manually removed some false positives in std/depr/depr.c.headers.

The `std` module doesn't export `::size_t`, this is a preparation for that module.

Reviewed By: ldionne, #libc, EricWF, philnik

Differential Revision: https://reviews.llvm.org/D146088

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[libc++] Remove "// -*- C++ -*-" comments from all .cpp files. NFCI.

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+

[libc++] Remove "// -*- C++ -*-" comments from all .cpp files. NFCI.

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.

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[libc++] Remove Lit annotations for unsupported GCC versions from the test suite

Since we officially don't support several older compilers now, we can
drop a lot of the markup in the test suite. Thi

[libc++] Remove Lit annotations for unsupported GCC versions from the test suite

Since we officially don't support several older compilers now, we can
drop a lot of the markup in the test suite. This helps keep the test
suite simple and makes sure that UNSUPPORTED annotations don't rot.

This is the first patch of a series that will remove annotations for
compilers that are now unsupported.

Differential Revision: https://reviews.llvm.org/D107787

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[libc++] Mark some tests as unsupported on GCC 5

There used to be a workaround where we'd pretend that GCC 5 didn't support
C++14 because it doesn't implement it properly. Since that workaround has

[libc++] Mark some tests as unsupported on GCC 5

There used to be a workaround where we'd pretend that GCC 5 didn't support
C++14 because it doesn't implement it properly. Since that workaround has
been removed (in 1eb211ada17a), we need to mark a few individual tests as
failing with GCC 5.

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[libc++] Remove the c++98 Lit feature from the test suite

C++98 and C++03 are effectively aliases as far as Clang is concerned.
As such, allowing both std=c++98 and std=c++03 as Lit parameters is
ju

[libc++] Remove the c++98 Lit feature from the test suite

C++98 and C++03 are effectively aliases as far as Clang is concerned.
As such, allowing both std=c++98 and std=c++03 as Lit parameters is
just slightly confusing, but provides no value. It's similar to allowing
both std=c++17 and std=c++1z, which we don't do.

This was discovered because we had an internal bot that ran the test
suite under both c++98 AND c++03 -- one of which is redundant.

Differential Revision: https://reviews.llvm.org/D80926

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Add include for 'test_macros.h' to all the tests that were missing them. Thanks to Zoe for the (big, but simple) patch. NFC intended.

llvm-svn: 362252

Support tests in freestanding

Summary:
Freestanding is *weird*. The standard allows it to differ in a bunch of odd
manners from regular C++, and the committee would like to improve that
situation. I

Support tests in freestanding

Summary:
Freestanding is *weird*. The standard allows it to differ in a bunch of odd
manners from regular C++, and the committee would like to improve that
situation. I'd like to make libc++ behave better with what freestanding should
be, so that it can be a tool we use in improving the standard. To do that we
need to try stuff out, both with "freestanding the language mode" and
"freestanding the library subset".

Let's start with the super basic: run the libc++ tests in freestanding, using
clang as the compiler, and see what works. The easiest hack to do this:

In utils/libcxx/test/config.py add:

self.cxx.compile_flags += ['-ffreestanding']

Run the tests and they all fail.

Why? Because in freestanding `main` isn't special. This "not special" property
has two effects: main doesn't get mangled, and main isn't allowed to omit its
`return` statement. The first means main gets mangled and the linker can't
create a valid executable for us to test. The second means we spew out warnings
(ew) and the compiler doesn't insert the `return` we omitted, and main just
falls of the end and does whatever undefined behavior (if you're luck, ud2
leading to non-zero return code).

Let's start my work with the basics. This patch changes all libc++ tests to
declare `main` as `int main(int, char**` so it mangles consistently (enabling us
to declare another `extern "C"` main for freestanding which calls the mangled
one), and adds `return 0;` to all places where it was missing. This touches 6124
files, and I apologize.

The former was done with The Magic Of Sed.

The later was done with a (not quite correct but decent) clang tool:

https://gist.github.com/jfbastien/793819ff360baa845483dde81170feed

This works for most tests, though I did have to adjust a few places when e.g.
the test runs with `-x c`, macros are used for main (such as for the filesystem
tests), etc.

Once this is in we can create a freestanding bot which will prevent further
regressions. After that, we can start the real work of supporting C++
freestanding fairly well in libc++.

<rdar://problem/47754795>

Reviewers: ldionne, mclow.lists, EricWF

Subscribers: christof, jkorous, dexonsmith, arphaman, miyuki, libcxx-commits

Differential Revision: https://reviews.llvm.org/D57624

llvm-svn: 353086

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Update more file headers across all of the LLVM projects in the monorepo
to reflect the new license. These used slightly different spellings that
defeated my regular expressions.

We understand that

Update more file headers across all of the LLVM projects in the monorepo
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

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Work around GCC 9.0 regression

llvm-svn: 349663

[libc++] Shrink variant's index type when possible

Summary:
Currently `std::variant` always uses an unsigned int to store the variant index. However this isn't nessesary and causes `std::variant` to

[libc++] Shrink variant's index type when possible

Summary:
Currently `std::variant` always uses an unsigned int to store the variant index. However this isn't nessesary and causes `std::variant` to be larger than it needs to be in most cases.

This patch changes the index type to be `unsigned char` when possible, and `unsigned short` or `unsigned int` otherwise, depending on the size (Although it's questionable if it's even possible to create a variant with 65535 elements.

Unfortunately this change is an ABI break, and as such is only enabled in ABI v2.

Reviewers: mpark

Reviewed By: mpark

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D40210

llvm-svn: 318621

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