Summary:
This diff adds a new StrandExecutor executor-type that is similar
to SerialExecutor in that it serialises execution of work enqueued
to it, but is more general in that it allows different tasks to be
executed on different executors.

To do this, it separates the queue out into a StrandContext object
which can be passed to multiple StrandExecutor objects, allowing them
each to share a queue, while allowing each StrandExecutor to dispatch
work queued to it to a different parent Executor.

Reviewed By: andriigrynenko

Differential Revision: D21848165

fbshipit-source-id: 4dda6bd13a9cd5b275a11f13101242cd73b327e7

Summary:
We had to fork OpenNSA and clone from it, see D19437386 for details.
Broadcom has now started hosting OpenNSA as a tarball.
Thus, we no longer need to maintain a fork (yay!)

This patch points opennsa manifest to fetch opennsa from this new location.

Reviewed By: bkoray

Differential Revision: D22175932

fbshipit-source-id: 51cd777ab836e4f191d78fbb2312925e446ca38f

Summary: This bug can be triggered when your computer name contains emoji. getdeps.py will fail to create this file due to Python attempts to write the file as cp1252 (Windows's default encoding)

Reviewed By: wez

Differential Revision: D22171935

fbshipit-source-id: fc3be2d1050c17ddbe05a0fc91d6613865f092ce

Summary: F14 class member fields are often in headers, and often the default constructor is implicit. The current implementation unconditionally instantiates `reserve()`, which has non-negligible cost. By specializing the default constructor we can avoid that in the common case.

Reviewed By: philippv, luciang

Differential Revision: D22166465

fbshipit-source-id: d31ebc7f6ab71392d49a6722545f8df9027d034b

Summary:
As per https://github.com/actions/virtual-environments/issues/709 there started to be some issies with Ubuntu envs running out of space. This should fix it.

Also our Cargo builds use a lot of space, changing them to be non-incremental and removing debug symbols keeps the build fast, but greatly reduces the disk space usage leaving us enough space on GitHub Actions virtual machines.
Pull Request resolved: https://github.com/facebookexperimental/eden/pull/23

Reviewed By: farnz

Differential Revision: D22160020

Pulled By: lukaspiatkowski

fbshipit-source-id: c23393e310c15ebf5a18b80f0bb5f1f894d24849

Summary: Try to fix the OSS build

Reviewed By: yfeldblum

Differential Revision: D22145695

fbshipit-source-id: a1290441b982f8df78ffa8dcd772f0c02c4535aa

Summary: [Folly] Missing public base class for `unicode_error`. which should publicly inherit `std::runtime_error`.

Reviewed By: Mizuchi

Differential Revision: D22153547

fbshipit-source-id: 4c60e8e072f0fc9240d199b6d81c7e85c99eaf34

Summary:
These optimizations were introduced in D1793554, mostly to mitigate the high cost of `select64`. We've had an efficient implementation of `select64` for Haswell for a while, and Haswell is more than 5 years old, so we can drop the optimization, which actually harms performance on modern microarchitectures.

While on a real workload this shows significant benefits, the microbenchmarks for very small skips are degraded:
```
============================================================================  ====================
folly/experimental/test/EliasFanoCodingTest.cpp relative  time/iter  iters/s    time/iter  iters/s
============================================================================  ====================
Next                                                         2.58ns  388.22M       2.55ns  391.93M
Skip_ForwardQ128(1)                                          4.81ns  207.72M       4.31ns  231.79M
Skip_ForwardQ128(2)                                          5.96ns  167.75M       4.67ns  214.07M
Skip_ForwardQ128(4_pm_1)                                     7.40ns  135.16M       4.87ns  205.29M
Skip_ForwardQ128(16_pm_4)                                    8.20ns  121.97M       5.38ns  185.93M
Skip_ForwardQ128(64_pm_16)                                  12.04ns   83.06M       8.97ns  111.51M
Skip_ForwardQ128(256_pm_64)                                 16.84ns   59.39M      13.19ns   75.79M
Skip_ForwardQ128(1024_pm_256)                               17.67ns   56.61M      14.19ns   70.45M
Jump_ForwardQ128                                            25.37ns   39.41M      25.47ns   39.26M
----------------------------------------------------------------------------  --------------------
SkipTo_SkipQ128(1)                                           7.27ns  137.59M      10.77ns   92.87M
SkipTo_SkipQ128(2)                                          10.99ns   91.01M      14.39ns   69.51M
SkipTo_SkipQ128(4_pm_1)                                     13.53ns   73.93M      16.15ns   61.90M
SkipTo_SkipQ128(16_pm_4)                                    20.58ns   48.59M      17.72ns   56.45M
SkipTo_SkipQ128(64_pm_16)                                   32.08ns   31.18M      31.16ns   32.09M
SkipTo_SkipQ128(256_pm_64)                                  38.66ns   25.87M      38.22ns   26.16M
SkipTo_SkipQ128(1024_pm_256)                                42.32ns   23.63M      42.07ns   23.77M
JumpTo_SkipQ128                                             47.95ns   20.86M      47.85ns   20.90M
----------------------------------------------------------------------------  --------------------
Encode_10                                                  103.99ns    9.62M     104.89ns    9.53M
Encode                                                       7.60ms   131.53       7.55ms   132.46
----------------------------------------------------------------------------  --------------------
defaultNumLowerBits                                          3.59ns  278.69M       3.61ns  276.97M
slowDefaultNumLowerBits                                     10.88ns   91.90M      10.98ns   91.06M
============================================================================  ====================
```

It is important to note however that these micro-benchmarks have very little variability in terms of effective skip distance for small skips, producing almost perfect branch prediction in the linear scan loop. In a real workload, the overhead of branch misprediction ends up being significant.

Reviewed By: philippv

Differential Revision: D22139846

fbshipit-source-id: 8df17a74aa57c92413709d9e11c60a77d5462422

Summary: Without FDO Clang generates very suboptimal code, adding this hints brings it almost to parity with FDO-compiled code.

Reviewed By: philippv, luciang

Differential Revision: D22139847

fbshipit-source-id: 2cdaf383ca1afd21db1b7ad2aafb3d3c7ce335b0

Summary: `folly::get_default()` returns a copy of shared_ptr that gets immediately discarded. The change avoids that.

Reviewed By: yfeldblum

Differential Revision: D22119215

fbshipit-source-id: 36aab580d7042d19b6b076cad20586697fbfa5e3

Summary:
Provide an Async wrapper for fibers::await, which blocks current task until promise is fulfilled.
This isn't a build block that is used in very common scenario, so prefered to put it in its own file.

Differential Revision: D22135318

fbshipit-source-id: 753dbefc4ac9a907f5b1f656f70291c88187b5e8

Summary:
Currently RequestContext::getRootidsFromAllThreads() can access StaticContext root ids concurrently with RequestContext::setRequestContext() without synchronization guards, which is not safe cross other platforms than x64 and also causing TSAN warnings when used in server contexts.
Therefore we can make it std::atomic and access it with relaxed order. This won't affect performance in major platform like x64 since the loads/stores instructions will be the same.
Also as a side effect this prevents RequestContext::StaticContext from generating copy/move constructor, so we remove an extra copy of root id in StaticContext in setRequestContext path.

Reviewed By: yfeldblum

Differential Revision: D22083558

fbshipit-source-id: ed70e394f1172b07ba00c15f05a370f84265785c

Summary: Pull Request resolved: https://github.com/facebook/folly/pull/1386

Reviewed By: yfeldblum

Differential Revision: D21992975

Pulled By: Orvid

fbshipit-source-id: 7d52e3e9f8db899079263ef15e9f1bbfbedadc44

Summary: This macro has been deprecated and given that there are not that many uses, it seems relatively simple to remove it entirely.

Reviewed By: yfeldblum, aary

Differential Revision: D16904736

fbshipit-source-id: 56daffd480c586be2a5636b3ce20c6fe1d5ea018

Reviewed By: yfeldblum

Differential Revision: D22071829

fbshipit-source-id: c7f0e1bc5a4257731bafee09144c33c9fb474e10

Summary: The ValueType alias in the multiplex function is not used and caused a build failure when I tried to use it, possibly because we have some extra warnings enabled in our code.

Reviewed By: lewissbaker

Differential Revision: D21685780

fbshipit-source-id: 3235c6444a623d5f484f0849679b1497f9456fa9

cargo_from_buck: add the patch section to Cargo workspace and allow workspace appending to existing manifest

Summary:
Two changes here:
1. The `[patch.crates-io]` section of `third-party/rust/Cargo.toml` is being now copied over to workspaces generated by autocargo for OSS and in the runtime generated Cargo.toml file for cargo-fbcode builds. Without that some projects could be buildable in Buck internally, but not externally on GitHub due to missing patches.
2. If a `[workspace]` Cargo.toml file is being generated and there is already a generated Cargo.toml file in the same directory then instead of overriding that file the `[workspace]` (and `[patch]`) sections are appended to that Cargo.toml file.

Reviewed By: farnz

Differential Revision: D22023144

fbshipit-source-id: dec54491c36c2ee0ab29eefb722b3eceaef6ffe1

Summary:
Adjust `CxxAllocatorAdaptor` such that it becomes default constructible.  This makes `SysArenaAllocator` default constructible too, which makes it much easier to use.

A default-constructed `SysArenaAllocator` is not useful at all.  Any attempt to allocate just throws `std::bad_alloc`.  But it makes it possible to at least compile code like this:

```
using MyAlloc = SysArenaAllocator<char>;
struct Foo {
   Foo() = default;  // BOOM
   Foo(MyAlloc &a) : v(a) {};
   vector<int, MyAlloc> v;
}
```

Reviewed By: yfeldblum

Differential Revision: D21967640

fbshipit-source-id: 5b74c6db14d75364b374cad71d0069b17769e5d6

Differential Revision:
D22027490

Original commit changeset: 964d9fa19ca9

fbshipit-source-id: 2c92ea47c64450cb031be4a6df3c3be4901500b7

Summary:
On Linux platforms the folly::futexWait() functions are implemented using the
futex() syscall, which requires passing a timeout parameter that specifies a
an expiry time either in CLOCK_REALTIME or CLOCK_MONOTONIC.

The futexWait() implementation currently assumes that the std::chrono::system_clock
and std::chrono::steady_clock implementations are thin wrappers over these
clock types and that we can directly convert the .time_since_epoch() values to
a timespec value that we can pass to the futex() syscall.

The Futex.clock_source test is checking this assumption about the implementation
of the std::chrono clocks.

Unfortunately, this assumption does not hold on recent libc++ implementations for
Apple platforms, which now uses the CLOCK_UPTIME_RAW clock for the
std::chrono::steady_clock implementation and so this test was failing on the
Mac platforms.

However, since we aren't actually relying on this assumption on platforms other than
Linux, we can just disable this test for non-Linux platforms.

Reviewed By: yfeldblum

Differential Revision: D22075639

fbshipit-source-id: 229995ba7c01b52d1949ef5942774920876d0994

Summary: Thread fences are not supported by TSAN

Reviewed By: yfeldblum

Differential Revision: D22056483

fbshipit-source-id: dfe5b462656605f2e659302125e248b287037629

Summary:
Original commit changeset: 25d4049019e4

Base diff broke fboss build (using fbcode_builder) with the following error:

/tmp/fbcode_builder_getdeps-ZrootZfboss2.gitZbuildZfbcode_builder-root/installed/folly/include/folly/init/Init.h:22:10: fatal error: folly/experimental/symbolizer/SymbolizerMode.h: No such file or directory
 #include <folly/experimental/symbolizer/SymbolizerMode.h>

Revert this first to unblock fboss while I am investigating the failure.

Reviewed By: shri-khare

Differential Revision: D22077183

fbshipit-source-id: 8bafc0518df82c61922104b7d59ef5ee20fdd572

Summary: Move the tests for the async framework into the a test directory under folly/fibers/async/

Differential Revision: D22023986

fbshipit-source-id: c38aa2a63381c2aea1fd89a0cf2740ca028152c9

Summary:
[Folly] Add missing `#include <memory>` in `folly/memory/ReentrantAllocator.h`.

Closes: https://github.com/facebook/folly/pull/1379.

Reviewed By: Orvid

Differential Revision: D22062251

fbshipit-source-id: 30e2f5aa2708048c478a298cf7e12a012ba59540

Summary: Fixed the missed initialization in InitOptions.

Reviewed By: luciang

Differential Revision: D22023637

fbshipit-source-id: 25d4049019e42708c98e5b589ed4838e2870d39b

Summary: F14 class member fields are often in headers, and often the default constructor is implicit. The current implementation unconditionally instantiates `reserve()`, which has non-negligible cost. By specializing the default constructor we can avoid that in the common case.

Reviewed By: philippv, luciang

Differential Revision: D22027490

fbshipit-source-id: 964d9fa19ca92797bcb209e09959dc4706af39d4

Summary:
This diff implements a deduction guide for explicitly creating and returning Async objects in lambdas and functions with deduced return types.

This saves the user from having to specify often lengthy return types when annotating such functions.

Reviewed By: A5he

Differential Revision: D21770141

fbshipit-source-id: f80898ef6eeadee7c5a7168aaae4031e224a0935

Summary: This diff implements traits to aid in the development of templated functions accepting annotated functions.

Reviewed By: yfeldblum, A5he

Differential Revision: D21770066

fbshipit-source-id: 40ae340aeeb484c4f9769c13b5c9a92a97723801

Summary:
This diff implements `coro_wait`, an annotated helper to block on the execution of a coroutine.

The goal here is to provide an easy way to migrate from fibers to coroutines.

Reviewed By: A5he

Differential Revision: D21978610

fbshipit-source-id: d59a222978d9db2963656312e71c7dcb2b9a11e9

Summary:
This diff adds `future_wait`, an annotated helper to run blocking `get` operations on futures.

`future_wait` will help annotate functions (and their caller stack) that block on futures.

For semifutures, deferred work is performed on fiber-main context, so there is no concern of bleeding fibers.

Reviewed By: yfeldblum

Differential Revision: D21965552

fbshipit-source-id: 79941c3b73c67d63d83dcdc778c62a0fc9051de3

Summary:
I think LZ4 was disabled accidentally in our rocksdb getdeps build in
D21319896. Enable it again on macOS and Linux, because otherwise this
breaks people with EdenFS mounts containing LZ4-compressed proxy
hashes.

Reviewed By: xavierd

Differential Revision: D21990356

fbshipit-source-id: b9166c2992ae51f09de3fa9a4f114143aa008f43

Summary:
Adds a helper utility called 'tag_invoke' for defining CPOs that dispatch to a call to an overload of the ADL-name 'tag_invoke()' that takes the CPO as the first argument instead of to a CPO-specific ADL-name.

This makes it possible to build generic adapters, such as type-erasing adapters, that can forward through calls to all CPOs through to an underlying object.

Adds FOLLY_DECLVAL(T) helper macro used in the implementation of some of the traits.

Reviewed By: yfeldblum

Differential Revision: D17867173

fbshipit-source-id: fadae6ec97498008a5238036b7310a1e0ae119a2

Summary:
folly::Hash<Range<T>> uses SpookyHashV2::Hash64 (for integral
T). On 32-bit platforms we need an explicit cast to avoid a narrowing
warning when converting this to size_t.

(Note: this ignores all push blocking failures!)

Reviewed By: shixiao

Differential Revision: D21491467

fbshipit-source-id: 1cbd05553c61b8dccb664ec4478cfb0b049dc5b5

Differential Revision:
D21918702

Original commit changeset: 3213e9536147

fbshipit-source-id: 4e9394b2026f0d6d74e668c7c72b3612a42770ea

Summary: This header is widely included (via `Future.h`) and instantiations of `UnboundedQueue`'s methods are expensive, so outline them (note that the template methods will only be instantiated if used, so that's fine).

Reviewed By: philippv

Differential Revision: D22014083

fbshipit-source-id: b6a71c38c142917e9e0d86fbb64a88462382952a

Summary: This would allow us have better stack trace with inline functions in signal handler output.

Reviewed By: luciang

Differential Revision: D21918702

fbshipit-source-id: 3213e9536147759a4e59f5b6f68d22d941d36c7f

Summary: [Folly] Wrap `_r_debug` per platform, since the way to get it varies by platform.

Reviewed By: ot, luciang

Differential Revision: D22004737

fbshipit-source-id: 6f6a6163c9709da0a5042b807cdd88fcdf2e57eb

Summary: Thread fences are not supported by TSAN

Reviewed By: yfeldblum

Differential Revision: D21989519

fbshipit-source-id: bb657c82a64abe025e8f4c030916c0cacc3c0b81

Summary:
The `collectSemiFuture` method doesn't exist.  Use `collectAllSemiFuture` instead.
Pull Request resolved: https://github.com/facebook/folly/pull/1385

Reviewed By: yfeldblum

Differential Revision: D21991532

Pulled By: DerekTBrown

fbshipit-source-id: 4ba3378fe34b7e6bb910f7045267fdbab87ebb14

Summary:
Original commit changeset: 8eb472ce50bf

This breaks time measurement to include measuring the wait preceding handler/callback invocation.

Reviewed By: w-o-o

Differential Revision: D21986042

fbshipit-source-id: 42701b929878c3f56d736de5ca0417814c64fce1