Summary:
> Under the following circumstances, the compilers are permitted to omit the copy and move construction of class objects:

> In a return statement, when the operand is the name of a non-volatile object with automatic storage duration, which isn't a function parameter or a catch clause parameter, and which is of the same class type (ignoring cv-qualification) as the function return type. This variant of copy elision is known as NRVO, "named return value optimization".

`std::move()` prevents this optimization.

GCC 9.1.0 warning:
```
moving a local object in a return statement prevents copy elision [-Wpessimizing-move]
```
Pull Request resolved: https://github.com/facebook/folly/pull/1217

Reviewed By: LeeHowes

Differential Revision: D17173234

Pulled By: yfeldblum

fbshipit-source-id: ed63ef89dfd01883ddd6fd775285997f96a029fd

Summary: [OpenSource] Cut `mstch` manifest, which was but is no longer used by `fbthrift`.

Reviewed By: avalonalex, davidtgoldblatt

Differential Revision: D17160816

fbshipit-source-id: 3b96142455d6990870e8ed3e5ce330d339d5a657

Summary:
Feed the first-party oncall data through to the testpilot
invocation.  This will set the owner of the test in continuous runs.

The oncall is passed through via the sandcastle module, which means
that you will have to manually pass it through for local testing
(see test plan), but it should automatically get picked up when
sandcastle schedules the `test` step of the job.

Reviewed By: chadaustin

Differential Revision: D17146802

fbshipit-source-id: a4f0e65853a46ed8709594c96db859ede2530b00

Summary: when trying to build openr with `getDeps.py` constant definitions where not available since they were not part of the generated thrift lib. this fixes it.

Reviewed By: chadaustin

Differential Revision: D16064417

fbshipit-source-id: ee2b3e061caf67235f4a873405cf6cd6fb663ef4

Summary: This algorithm multiplexes values from a stream-of-streams into a single stream of events that identifies the stream index the event originated from and also the end-of-stream and stream-error events.

Reviewed By: lewissbaker

Differential Revision: D15643142

fbshipit-source-id: a309a485f11465d9068ea81f4bc32823dd34291f

Summary: The `transform()` algorithm uses the provided function to transform each value in the provided input stream and produces each transformed value on the returned output stream.

Reviewed By: lewissbaker

Differential Revision: D16774893

fbshipit-source-id: 7ab33706c667b1706c0cb0b1c0ecb9046f47a325

Summary: Adds a new `folly::coro::merge()` algorithm that accepts an async stream of async streams and returns an async stream that merges and interleaves the results.

Reviewed By: lewissbaker

Differential Revision: D15617383

fbshipit-source-id: cafb8e31725cdb21cfa00ce186901329828c2b68

Summary: fixes the CI build

Reviewed By: dddmello

Differential Revision: D17158685

fbshipit-source-id: 44ea871eab4d8c964b8372fb8d84879fa823ca50

Summary:
Range-v3 v0.9.1-pre deprecated and renamed a bunch of interfaces to harmonize with the direction of C++20's `std::ranges`. In this diff, I:

* Rename the `ranges::view` namespace qualification to `ranges::views` (plural),
* Rename the `ranges::action` namespace qualification to `ranges::actions` (plural),
* Rename `ranges::view::bounded` to `ranges::views::common`,
* Rename `ranges::to_` to `ranges::to`,
* Replace _some_ implicit conversions of views to containers with explicit invocations of `ranges::to` (more work to be done here, but can wait).

Reviewed By: mzlee

Differential Revision: D17061465

fbshipit-source-id: f28205ecf3965d3560e9cffe2805d0b404597b21

Summary:
Remove calls to Future::then(executor, callback).

This form of Future::then is ambiguous, and does not yet implement the stronger
typing of thenValue and thenTry. It is also tempting to use instead of via,
where it is not obvious that it has the behaviour of wrapping a via call in a
push and pop of the current executor:
.pushCurrentExecutor().via(executor).then(callback).popCurrentExecutor().

With the addition of inline continuations, we can instead make the nesting
explicit at low cost by making it an inline continuation that launches an
asynchronous task on the passed executor.

Reviewed By: yfeldblum

Differential Revision: D15100419

fbshipit-source-id: e929e2eaf2fc30313cb099150be3a9535ae729a6

Summary:
TimeKeeper::after and TimeKeeper::at return Futures that for the majority of implementations complete on a TimeKeeper owned executor. This can lead to problems.

Consistent with other API cleanups, this diff switches TimeKeeper APIs to return SemiFuture, requiring that the caller attach an explicit executor when work is to be scheduled downstream of the TimeKeeper.

Reviewed By: yfeldblum

Differential Revision: D17005944

fbshipit-source-id: 98d7e8aaf1ad40ce2180503f632f2f0003bb12be

Summary: Under some circumstances the DeferredExecutor might already have nested executors and this code adds more. Both incoming futures should instead nest within a fresh DeferredExecutor returned that is part of the SemiFuture from the operation.

Reviewed By: mpark

Differential Revision: D17121117

fbshipit-source-id: b4507bf5d7b0c98e5e5de6f73ff4bd3e2790374c

Summary:
[Folly] RTM re-nits for `xabort`.

* Remove param pack.
* Always noreturn.

Reviewed By: nbronson

Differential Revision: D17117350

fbshipit-source-id: b16056b1f02956d334da4494c689a4b988a961d4

Summary:
The `materialize()` algorithm meterializes values from a stream into a stream of events that represent each value and also the end-of-stream and stream-error events.

`dematerialize()` reverses a materialized stream by replaying the events recorded in the input stream to an output stream.

Reviewed By: lewissbaker

Differential Revision: D16772236

fbshipit-source-id: 27de543ea2d02691a376fd0f11d0113c5c39287d

Summary:
boost.fiber is not available on macos and is required by fbzmq,
so disable the build on darwin.

In D17128935 I tried to make libzmq build with cmake to build
on windows, but there's a problem with its cmake and it fails
to configure.

So let's just nop out the build for !linux for now.

Reviewed By: jstrizich

Differential Revision: D17129362

fbshipit-source-id: db89010d18707a4105b8d395b1758f738336495d

Summary:
In order to foster healthy open source communities, we're adopting the
[Contributor Covenant](https://www.contributor-covenant.org/). It has been
built by open source community members and represents a shared understanding of
what is expected from a healthy community.

Reviewed By: josephsavona, danobi, rdzhabarov

Differential Revision: D17104640

fbshipit-source-id: d210000de686c5f0d97d602b50472d5869bc6a49

Summary:
This module provides a `add_fbthrift_library()` convenience function that can
be used to generate thrift libraries for multiple languages with a single
call.

Reviewed By: wez

Differential Revision: D16742275

fbshipit-source-id: c13120cf9e051629951282141eb22f3e085782f9

Summary:
This module helps generate Python libraries from thrift files.
It is the Python equivalent of `FBThriftCppLibrary.cmake`

Reviewed By: wez

Differential Revision: D16742274

fbshipit-source-id: ef0dc7f24eb1c7375d2587ee6b71fd25bd6f35a7

Summary:
Fix a minor bug in the argument parsing for `add_fbthrift_cpp_library()`:
only a single value should be supplied for the `THRIFT_INCLUDE_DIR` argument.
This parameter should not accept a list of arguments.

Reviewed By: strager

Differential Revision: D17125810

fbshipit-source-id: 31f354e4d6299d3626a94f3b4b5ff8c58bb0cf7b

Summary:
An AsyncGenerator coroutine now has an implicit associate CancellationToken that is inherited from the calling context of each `co_await gen.next()` call.

This means that generators that correspond to long-running subscriptions now have an in-built channel that allows them to cancel the subscription.

This is also useful for algorithms that introduce concurrency in processing of stream data. eg. The `buffer()` or `merge()` algorithms.

Reviewed By: kirkshoop

Differential Revision: D16833864

fbshipit-source-id: be8faf1ec438c4248091e02d6a264d3760e2d73d

Summary:
Pull Request resolved: https://github.com/facebook/folly/pull/1212

MSVC has a bug and can't match definitions of some of the constructors to the corresponding declarations in a class body. This diff workarounds the bug by inlining constructors.

Reviewed By: LeeHowes

Differential Revision: D17119718

fbshipit-source-id: eb7a9d4916b962c718d047eb0ee7fa4a9761776e

Summary:
The `collectAll()`, `collectAllRange()` and `collectAllWindowed()` functions now cancel their subtasks when either the parent task is cancelled or when any of the subtasks fail with an exception.

The `collectAllTry()`, `collectAllTryRange()` and `collectAllTryWindowed()` functions now cancel their subtasks if the parent task is cancelled, but not if the child tasks fail with an exception.

The logic between the distinction here is that if you are calling one of the 'try' functions then you are intending to handle partial failure and so probably want each of the operations to run to completion independently of the others.

Reviewed By: kirkshoop

Differential Revision: D16820619

fbshipit-source-id: 5c203b41592a0145ff7be1c609dfccd39c41a3df

Summary: `clang-cl` on Windows also defines `__PRETTY_FUNCTION__` which has a format different from `__FUNCSIG__`. Therefore folly breaks users of this macro. Alias should be defined only when "real" MSVC compiler is used.

Reviewed By: akrieger, Orvid, blackm00n

Differential Revision: D17094657

fbshipit-source-id: 4b191a61201704382e6b6e178bcc1c673511c537

Summary:
Rename the `ThriftCppLibrary.cmake` file to `FBThriftCppLibrary.cmake`, and
also rename `add_thrift_cpp2_library()` to `add_fbthrift_cpp_library()`.

Explicitly calling this `fbthrift` helps clearly distinguish that this is
intended for use with fbthrift (https://github.com/facebook/fbthrift/), as
opposed to Apache thrift.

Reviewed By: wez

Differential Revision: D16738440

fbshipit-source-id: 9b255e06b71c98ad74a34989f564a211958dcdd5

Summary:
CacheLocality's parsing code for /proc/cpuinfo doesn't properly
handle systems in which there are offline CPUs. This diff makes it so
we fall back onto the sequential cache locality implementation in the
problematic scenarios.

This should address https://github.com/facebook/folly/issues/1208

Reviewed By: shixiao

Differential Revision: D17093176

fbshipit-source-id: 4da3a9dc53622f829af37ed70a2531c66fd92ddb

Summary:
Use folly::cacheline_align_v to prevent failures when running folly on platforms
where extended alignment is not supported.  The thread pools only used extended
alignment as an optimization; so it is safe to disable it when not needed

Reviewed By: yfeldblum

Differential Revision: D17077439

fbshipit-source-id: 63ba59aaf7ce45231bb25427af84292c3a3464a9

Summary:
The non-atomic field `inUse_` is protected by a lock in `getStackCache`, but not in `giveBack`. This
is a data race and it is caught by TSAN.

Reviewed By: yfeldblum

Differential Revision: D17109710

fbshipit-source-id: 7c0d5d948740516422efca0895a702566c804bb4

Summary:
Windows and macOS compilers are sensitive to this,
and this was overlooked in D16636130

Reviewed By: selat

Differential Revision: D17113825

fbshipit-source-id: 16fe9210b07a096a58f3370df64874514e28ea46

Summary:
Compiler passes rvalue reference for named local variable to return_value:
https://reviews.llvm.org/D51741

Reviewed By: lewissbaker

Differential Revision: D16963353

fbshipit-source-id: 98d846153adb2235b61bb8fb54d10f032d4c0055

Summary:
- Prior to commit 8cb615a2
  (Differential Revision: D3394612), `Range:size()` had an assert checking
  that the beginning iterator of the range is less than or equal to the end
  iterator. Unfortunately, due to GCC bug 71448, the `assert` was not allowed
  if we wanted `size()` to remain a `constexpr` function.
- This bug is no longer an issue with our current supported versions of GCC.
  As such, add the assert back in.
Pull Request resolved: https://github.com/facebook/folly/pull/1155

Reviewed By: ericniebler

Differential Revision: D15641627

Pulled By: yfeldblum

fbshipit-source-id: 0677053c18fa55aaa4727947c241f0675362861b

Summary:
Update install_fb_python_library() to work with CMake versions older than 3.7.

Previously the code used a generator expression in the directory argument
supplied to `install(DIRECTORY)`.  Support for generators in this parameter
was only added in CMake 3.5, but it was buggy and did not correctly handle
absolute paths until 3.7.

This updates the code to avoid using a generator expression.  This does
require that the corresponding `add_fb_python_library()` statement appear
before the `install_fb_python_library()` statement, but this seems like a
pretty reasonable restriction.

Reviewed By: chadaustin

Differential Revision: D17103597

fbshipit-source-id: 54d6af93a3f530373cfe3137db99436d8484f308

Summary:
[Folly] RTM nits.

* No nested namespace.
* All status values supported.
* Tests included in cmake builds.
* API functions avoid `SIGILL` at runtime.

Reviewed By: nbronson

Differential Revision: D16636130

fbshipit-source-id: 9f9dc99b0826abbda295b069eb4823b3416af5d1

Summary:
This is a useful testing utility that people can use if they use timeout APIs
like `folly::futures::sleep()`

Reviewed By: LeeHowes

Differential Revision: D17065352

fbshipit-source-id: f9ea8366af7fc9429bfb1065328ed746c824f810

Summary: The sorted vector types have constructors which "steal" capacity from a pre-filled container.  Add tests to cover the cases where this is a folly:small_vector, and a std::pmr::vector.

Reviewed By: nbronson

Differential Revision: D17074150

fbshipit-source-id: e94b7e136553653081abe86559c4c013b9aac031

Summary:
Adds static factory `CancellationSource::invalid()`.

This can be used to construct a `CancellationSource` that can't be cancelled but that doesn't perform any heap-allocations.

Reviewed By: kirkshoop

Differential Revision: D16816764

fbshipit-source-id: bb87273903a6a8d245d207f4e6bda94e5c3d3dad

Summary: Tweak futures::within to be completely deferred, including the timeout path, allowing it to support a SemiFuture-returning TimeKeeper.

Reviewed By: yfeldblum

Differential Revision: D17006080

fbshipit-source-id: cbed58579d33f6d6ecf60dce5f9c8b886fc4d4c4

Summary:
wait() is guaranteed to succeed and not throw for either Baton type, so
using a reference here is safe. When the future is completed on another thread,
the shared_ptr causes cache contention.

```
Thread 1            Thread 2
make_shared/inc
inc
...
                    dec ref
dec ref/free
```

Reviewed By: yfeldblum

Differential Revision: D17077672

fbshipit-source-id: a6010ed159353decefbd5c51f4347370b16f7f60

Summary:
Update the generated `run_cmake.py` script to use `os.execve()` rather than
`subprocess.call()`, so that it now propagates CMake's return code back to its
caller.

Reviewed By: chadaustin

Differential Revision: D17089206

fbshipit-source-id: e01f05f492ccb842d4967e59fd0bc9a3e59b8a42

Summary:
Fix printing the manifest context in the error message if we cannot find a
project fetcher.  Previously the context in the message would be printed as
something like `<getdeps.manifest.ManifestContext object at 0x7fcce987e610>`,
now it shows instead as something like
`{distro=ubuntu, distro_vers=18.04, fb=off, os=linux, test=off}`

Reviewed By: chadaustin

Differential Revision: D17089208

fbshipit-source-id: c16549b61030d813b7b5ff9f65966436dc1e1898

Summary:
This just strips off a trailing '/' from the `INSTALL_DIR` property that we
set on python targets, to avoid having double-slashes in the paths that we use
during installation.  This shouldn't really have any material difference other
than cleaning up the paths that get printed during the installation phase.

Reviewed By: chadaustin

Differential Revision: D17089207

fbshipit-source-id: ab36bb76c19fa60fe037f7a5290ccfd6bdbf13b0