Summary:
Adds a new awaitable that extracs the current async stack-trace as a vector
of program counters from within the current coroutine.

Usage:
```
std::vector<std::uintptr_t> programCounters =
  co_await folly::coro::co_current_async_stack_trace;
```

Reviewed By: andriigrynenko

Differential Revision: D21130683

fbshipit-source-id: bf67a9969f73bdb8b91b4cc2858883b8e87762e2

Summary: Defined new callback - ReadAncillaryDataCallback, which enables getting ancillary data when receive a message using recvmsg API.

Reviewed By: cgrushko

Differential Revision: D24246707

fbshipit-source-id: 3363b5fafe8d370cf5560afe00476fc8ea723e7a

Summary: Also re-order the test slightly to catch this.

Reviewed By: yfeldblum

Differential Revision: D25704580

fbshipit-source-id: 1421daed11a0d41e1b99d573b38fc8fc70381486

Summary: All changes were automated

Reviewed By: Orvid

Differential Revision: D25507505

fbshipit-source-id: 4a1ae7578876975e20fd8eba194b9f8ed43d3530

Summary: All changes were automated

Reviewed By: Orvid

Differential Revision: D25507540

fbshipit-source-id: 71279e19ddad29622c14729d73f5d0d45f0ba410

Summary: All changes were automated

Reviewed By: Orvid

Differential Revision: D25507581

fbshipit-source-id: 5c936f1f81c5c754d3b64fb17b7dab253a178a39

Summary:
Fix gso typo

(Note: this ignores all push blocking failures!)

Reviewed By: kevin-vigor

Differential Revision: D25699054

fbshipit-source-id: bac1a7a5c13efa5a58ecec11edf72c500b0783b5

Summary: [folly] Add `co_cancelled`, effectively a shorthand for `co_error(OperationCancelled{})`.

Reviewed By: Mizuchi, lewissbaker

Differential Revision: D25627993

fbshipit-source-id: 91f80772a8b179a4de0fe3b29dfe7eecaafb8e1b

Summary: Fix nullptr dereference

Reviewed By: kevin-vigor

Differential Revision: D25687105

fbshipit-source-id: 59b0f3e4adc810f6e1a89447667cd167c52f7fb5

Differential Revision: D25683616

fbshipit-source-id: 7f199b0e43e0a5a76c4cf16412b22abdc28833ac

Summary: Fix `Arena` bytes-used accounting across calls to member `merge`.

Reviewed By: luciang

Differential Revision: D25656949

fbshipit-source-id: b230b0cdbf51b146fd566cbf688f49817bdf874d

Summary: [folly] Rename coro `Error.h` to `Result.h` since it has multiple result types.

Reviewed By: Mizuchi

Differential Revision: D25625178

fbshipit-source-id: 45f8194922b764429969329563a4695b1c13da6f

Summary: Fix `Arena` bytes-used accounting across calls to member `clear` after a sequence of all-large allocations.

Reviewed By: luciang

Differential Revision: D25656875

fbshipit-source-id: e79aca5f58b61bf1bd4790f8badd0dad6063a6ed

Summary: folly::Singleton is used for singletons that manage resources (thread, fds etc.) and it's generally not safe to use previously created folly::Singletons in child process after fork.

Reviewed By: yfeldblum

Differential Revision: D25292667

fbshipit-source-id: 5343d26c72bb9203429a918a3bb5d458c44e9f3b

Summary:
Recently I found that its impossible to access elevated Watchman daemon from non-elevated process on Windows.

```
events.js:174
      throw er; // Unhandled 'error' event
      ^
Error: connect EPERM \\.\pipe\watchman
    at PipeConnectWrap.afterConnect [as oncomplete] (net.js:1106:14)
Emitted 'error' event at:
    at Socket.<anonymous> (C:\open\ovrsource\unity\socialvr\_js\node_modules\fb-watchman\index.js:118:12)
    at Socket.emit (events.js:198:13)
    at emitErrorNT (internal/streams/destroy.js:91:8)
    at emitErrorAndCloseNT (internal/streams/destroy.js:59:3)
    at process._tickCallback (internal/process/next_tick.js:63:19)
```

To fix this, it was suggested by wez to use [his library](https://github.com/wez/EleDo) to force Watchman daemon always start in normal mode on Windows. In this stack of commits I did integrated his library into project and used it to force daemon restart in normal mode when spawned from elevated terminal.

To make it happen, I checked-in library sources and created proxy project which depends on the initial library and contains header bindings and cmake configuration. I did copy pasted Rust cmake macroses from another facebook project - eden, and also created analogue of autogen.sh but for Windows - autogen.cmd.

Pull Request resolved: https://github.com/facebook/watchman/pull/878

Test Plan:
Launch elevated terminal
Start watchman.exe produced from sources
Observe daemon starting and answering
In process monitor, observe watchman.exe process running under user group

Reviewed By: fanzeyi

Differential Revision: D25595879

Pulled By: arhelmus

fbshipit-source-id: 15eb29adcf5bd4a5708b6533a1b2bacbf13f431c

Summary: [Folly] Cut `FOLLY_HAVE_MEMRCHR` since it is now unused.

Reviewed By: Orvid

Differential Revision: D22130149

fbshipit-source-id: b10c5a52354f5c549d96b54e0c165f08b96612b1

Summary: Since this API is discouraged from use, users should call `folly::observer_detail::ObserverManager::waitForAllUpdates` (and face whatever consequences may come with it).

Reviewed By: yfeldblum

Differential Revision: D25629064

fbshipit-source-id: 141b27bbc4f7cf9b628f15f837c38dd4d8a04f31

Reviewed By: zertosh

Differential Revision: D25662961

fbshipit-source-id: f5811a5797fd6dc8733fdf86f35c93d12a08d53a

Summary: Fix `Arena` total-size accounting across calls to `clear`, as reported by member `totalSize`.

Reviewed By: luciang

Differential Revision: D25656867

fbshipit-source-id: b5c7bb0e95199a9fa2c94c04de65b8f494eef146

Summary: Don't use gtest/gtest.h directly.

Reviewed By: yfeldblum

Differential Revision: D25659806

fbshipit-source-id: a8dd0da814465a787ab7904bdd0256f22b6e3ed8

Summary: As per title

Reviewed By: yfeldblum

Differential Revision: D25636982

fbshipit-source-id: a59c2325558175e122941000ab645c8735a3a425

Summary: Use `throw_exception` consistently in `Arena` for consistency.

Differential Revision: D25637401

fbshipit-source-id: 92cda5acc09b871fed78044fa3f3fa2c41b01609

Summary: [folly] `asan_region_is_poisoned` to wrap Address Sanitizer's `__asan_region_is_poisoned`.

Reviewed By: ot, luciang, markisaa

Differential Revision: D25651040

fbshipit-source-id: 0c8f1d0203ada43746b5e2e71c1bd8b883248f68

Summary: All changes were automated

Reviewed By: Orvid

Differential Revision: D25507555

fbshipit-source-id: c0be9a04b8a5f502f4753ce6e163a78c428bfad6

Summary:
Fix QUIC OSS build

(Note: this ignores all push blocking failures!)

Reviewed By: danobi

Differential Revision: D25645282

fbshipit-source-id: fcb71d4e930d7ac3802f31d71599338fb346eb80

Summary: Required for Windows with the more strict include order via upcoming formatting diffs.

Reviewed By: yfeldblum

Differential Revision: D25636437

fbshipit-source-id: 0a5fd400f63220400f89affb11b66e9692e9b352

Summary: Because folly can't depend on common.

Reviewed By: yfeldblum

Differential Revision: D25636772

fbshipit-source-id: d7b049330c9ca68eb4013fde5ca6de9413433823

Summary: Allow scheduling a "poison" task to indicate shutdown

Reviewed By: andriigrynenko

Differential Revision: D25609015

fbshipit-source-id: 8a42b99b402d78db7cfa3bd194730bb6948567c6

Summary: Currently doesn't do anything since TLS 1.3 is not yet enabled by default. Once it is, calling disableTLS13() on a context will set the max TLS version to TLS 1.2.

Reviewed By: mingtaoy

Differential Revision: D25642589

fbshipit-source-id: 0e580916b929111ed9721ca142b59eab0ea187df

Summary: Allows use with std::optional when available

Reviewed By: WillerZ

Differential Revision: D25618828

fbshipit-source-id: 3e039406ff1e885fd1767148b907635b23f7a88b

Summary: Use comparison expectations like `EXPECT_GE` in `Arena` test as v.s. `EXPECT_TRUE` with the comparison inside.

Reviewed By: markisaa

Differential Revision: D25631097

fbshipit-source-id: 4fb430f34d7683e3b82dd3fbb4408360f8990353

Summary: All changes were automated

Reviewed By: Orvid

Differential Revision: D25507575

fbshipit-source-id: cbddef5a79008d9bf8b6e0234e6433084e5d8df9

Summary: These are the only files out of hundreds in folly that have them, so just remove them entirely.

Reviewed By: yfeldblum

Differential Revision: D25612198

fbshipit-source-id: 88d4f5c2ffa08d45d0a901c9ef874cddc2730291

Summary: Eliminate noisy log message and provide the intended deadlock clue in a function name.

Reviewed By: yfeldblum

Differential Revision: D25627130

fbshipit-source-id: 8d92007d4fa7eff1efb5857f7f49bebde2d59b70

Summary: Specifically, ending in Test, singular, and reflecting the file being tested in full.

Reviewed By: yfeldblum

Differential Revision: D25612187

fbshipit-source-id: 514477e08b9e231d8574cae19640717b689b7d56

Differential Revision:
D25549986 (https://github.com/facebook/folly/commit/9a83e4242a933f91c9339b4c6d223267a43a89c1)

Original commit changeset: fd323e2e8cbf

fbshipit-source-id: af2bdb9f66d23d144f7e2e96118727d8b158f83f

Summary:
folly::AsyncSocket: propagate finishFail ex

(Note: this ignores all push blocking failures!)

Reviewed By: yfeldblum

Differential Revision: D25479314

fbshipit-source-id: 683e1e118ace2ea983bde78d8afddb84dab69f6f

Summary:
AsyncUDPSocket: multi release pacing for UDP GSO

(Note: this ignores all push blocking failures!)

Reviewed By: mjoras

Differential Revision: D25451694

fbshipit-source-id: 3550a3744b407cbc40efebe759f472ee9f40a5b8

Summary:
The `StringPiece` overloads of comparisons operators are inefficient to compile, as they get in the overload set of every comparison and then get ruled out by SFINAE (which require trait instantiations).

Move them instead to friend inlines, where they enjoy the expected implicit conversion rules.

(Note: this ignores all push blocking failures!)

Reviewed By: yfeldblum

Differential Revision: D25549986

fbshipit-source-id: fd323e2e8cbf4f3dd29508b8aff1cfaba2784f4f

Summary:
Previously theFOLLY_HAVE_LIBUNWIND macro would evaluate to false even if LibUnwind was available.

Pull Request resolved: https://github.com/facebook/folly/pull/1501

Reviewed By: yfeldblum

Differential Revision: D25583562

Pulled By: Orvid

fbshipit-source-id: 7dac5afa1f0f24747f4accf2e08b804ab12e416f