[libc++] Implement P2273R3 (`constexpr` `unique_ptr`)

Reviewed By: mordante, #libc

Differential Revision: https://reviews.llvm.org/D131315

[libc++] Value-initialize unique_ptr's deleter_type

According to the C++ standard, the stored pointer and the stored deleter
should be value-initialized.

Differential Revision: https://reviews.llvm

[libc++] Value-initialize unique_ptr's deleter_type

According to the C++ standard, the stored pointer and the stored deleter
should be value-initialized.

Differential Revision: https://reviews.llvm.org/D113612

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[libcxx][test][NFC] Fix comment typos.

(Testing git commit access.)

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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Overhaul unique_ptr - Implement LWG 2801, 2905, 2520.

This patch overhauls both specializations of unique_ptr while implementing
the following LWG issues:

* LWG 2801 - This issue constrains unique_

Overhaul unique_ptr - Implement LWG 2801, 2905, 2520.

This patch overhauls both specializations of unique_ptr while implementing
the following LWG issues:

* LWG 2801 - This issue constrains unique_ptr's constructors when the deleter type
is not default constructible. Additionally it adds SFINAE conditions
to unique_ptr<T[]>::unique_ptr(Up).

* LWG 2905 - This issue reworks the unique_ptr(pointer, /* see below */ deleter)
constructors so that they correctly SFINAE when the deleter argument cannot
be used to construct the stored deleter.

* LWG 2520 - This issue fixes initializing unique_ptr<T[]> from nullptr.
Libc++ had previously implemented this issue, but the suggested resolution
still broke initialization from NULL. This patch re-works the
unique_ptr<T[]>(Up, deleter) overloads so that they accept NULL as well
as nullptr.

llvm-svn: 300406

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Rewrite and cleanup unique_ptr tests.

This patch almost entirely rewrites the unique_ptr tests. There are a couple
of reasons for this:

A) Most of the *.fail.cpp tests were either incorrect or coul

Rewrite and cleanup unique_ptr tests.

This patch almost entirely rewrites the unique_ptr tests. There are a couple
of reasons for this:

A) Most of the *.fail.cpp tests were either incorrect or could be better written
as a *.pass.cpp test that uses <type_traits> to check if certain operations
are valid (Ex. Using static_assert(!std::is_copy_constructible_v<T>) instead
of writing a failure test).

B) [unique.ptr.runtime] has very poor test coverage. Many of the constructors
and assignment operators have to tests at all. The special members that have
tests have very few test cases and are typically way out of date.

C) The tests for [unique.ptr.single] and [unique.ptr.runtime] are largely
duplicates of each other. This means common requirements have two different
sets of tests in two different test files. This makes the tests harder to
maintain than if there was a single copy.

To address (A) this patch changes almost all of the *.fail.cpp tests into
.pass.cpp tests using type traits; Allowing the *.fail.cpp tests to be removed.

The address (B) and (C) the tests for [unique.ptr.single] and [unique.ptr.runtime]
have been combined into a single directory, allowing both specializations to share
common tests. Tests specific to the single/runtime specializations are given the
suffix "*.single.pass.cpp" or "*.runtime.pass.cpp".

Finally the unique.ptr test have been moved into the correct directory according
to the standard. Specifically they have been removed from "utilities/memory" into
"utilities/smartptr".

PS. This patch also adds newly written tests for upcoming unique_ptr changes/fixes.
However since these tests don't currently pass they are guarded by the macro
TEST_WORKAROUND_UPCOMING_UNIQUE_PTR_CHANGES. This allows other STL's to validate
the tests before libc++ implements the changes. The relevant libc++ changes should
land in the next week.

llvm-svn: 300388

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