Summary:
Add a new concept of a safe-point to folly::Task<...> with implementation-defined semantics.

Example usage:
```lang=c++
Task<> co_something() {
  while (is_work_available()) {
    co_await co_safe_point;
    do_work();
  }
}
```

Previously, a coroutine function which would cancel itself if cancellation is requested would need to spell cancellation pass-through a bit less elegantly:
```lang=c++
Task<> co_something() {
  while (is_work_available()) {
    auto token = co_await co_current_cancellation_token;
    if (token.isCancellationRequested()) {
      co_yield co_cancel;
    }
    do_work();
  }
}
```

Initial semantics include:
* If cancellation has been requested, finish the coroutine with cancellation.
* Otherwise, continue the coroutine.

In the future, it may be wise to add additional behavior:
* If the coroutine has been running for too long since its previous resumption, reschedule it.

Reviewed By: aary

Differential Revision: D25861265

fbshipit-source-id: 6da896f1529d652bfe222cf3a70e9dbe19778510

Summary: Use `LOG_FIRST_N` in `MemoryIdler` rather than reimplement it.

Reviewed By: praihan

Differential Revision: D26185702

fbshipit-source-id: c1045ef8bf6aabefa4c0806c35c156539d6e594f

Summary:
Delay registration of the timer and signal fds until running the loop first time
On some Linux kernel versions, io_uring will remove any fd registrations on thread exit. So creating the backend in a thread that exits later will cause us not to receive timer and signal fd events.

Reviewed By: kevin-vigor

Differential Revision: D26200805

fbshipit-source-id: dc3025964deb3cf87bf3e5a27141abcdb8698caf

Summary:
moving to 1.7.0 for open source github sai

also build fake with 1.7.0

Differential Revision: D26152792

fbshipit-source-id: 02e7bfb218d200666e506e3115ee8f5dba5ece0a

Differential Revision:
D26163397 (https://github.com/facebook/folly/commit/7c9f69f9c72b598c5dd942d93a94f371c6fa901d)

Original commit changeset: 48cd6cb57c48

fbshipit-source-id: fe0dd79a4e9ec77194cabf0edc697d9746542d3c

Summary:
Currently, when C++ threads communicate with python's event loop, they place
the items on the queue, notify the event loop, and when even loops starts
running, they would consume all items from this queue at once.
The downside of this approach is that we are unable to deprioritize the
upstream tasks to yield to internal python tasks. However, such ability to yield
is fundamental to how Thrift approaches load shedding under overload.
In this diff we change the approach to take only a single item from the queue at a
time. Notice that if queue is not emptied, the consumer will notify the event loop to
consume from this queue on the next iteration of the loop.

Reviewed By: andriigrynenko

Differential Revision: D26163397

fbshipit-source-id: 48cd6cb57c48ea67dce4eb5f0de6db5b0feb75ac

Summary:
Previous version does not compile when converting from `const folly::Optional`
to `std::optional`. This happens in a typical `for (const auto& x : vec)` where
`x` is or contains `folly::Optional`.

Add a new `const` version in case people case about `Value&` ctor as opposed to
`const Value&`.

Reviewed By: iahs

Differential Revision: D26137442

fbshipit-source-id: 649be596b67a01c6d1f4be341aad65f1099b74a1

Reviewed By: igorsugak

Differential Revision: D26142316

fbshipit-source-id: 6ee85228e58f5068ee14154d02ad07f731c039ec

Summary: This introduces the concept of a *concurrent* version of `folly::lazy` that stems from our own needs for use lazily instantiated class variables in a multi-threaded environment.

Reviewed By: ot, praihan, luciang

Differential Revision: D25958581

fbshipit-source-id: 6b85402708fe9ca31b4d93607cf92f23d6a3edb5

Summary: Fix broken build

Reviewed By: ispeters, Orvid

Differential Revision: D26138456

fbshipit-source-id: 8f46b268ecaf923e507db6706af7840095a151f7

Summary: DefaultCPUExecutor is the same as InlineExecutor, but hidden to avoid instantiating it to allow filtering on type, primarily in coro::task.

Reviewed By: mpark, terrelln

Differential Revision: D26077566

fbshipit-source-id: 06704134f2446727cbb9f093df0b1954b46d2e49

Summary:
The current data storage API code assumes that the MicroLock is 4-byte aligned and that the lock lives in the lowest byte of `word()`. This assumption is incorrect (see added test). We should instead rely on `baseShift()`.

This API is only used for `folly::compact_once_flag` which is new so low chance something broke.

Reviewed By: andriigrynenko, davidtgoldblatt

Differential Revision: D26091484

fbshipit-source-id: c6e6e9aa7a963cada16e0ef7783fcc6bf6d2aed6

Summary: Even though `folly::MicroLock` is 1 byte, `detail::Futex<>` (aka `std::atomic<uint32_t>`) operates on 4 bytes. So 3 bytes are accessed but not used in any way. So we need to disable memory sanitizer.

Reviewed By: andriigrynenko

Differential Revision: D26082888

fbshipit-source-id: fe585b60c96f48c02df69d182bd75a8eccde2a42

Summary:
Many protocols often only require certificate information at the beginning of
the connection (for authentication and authorization). Often, the
protocol implementation will itself store its own representation of a transport
identity.

Certain certificates, such as X509 certificates, may be large and unnecessary
to hold onto during the entirety of a connection past the initial connection
establishment / handshaking phase. It is desirable to hint to transport
implementations when certificate information is no longer needed.

Reviewed By: AjanthanAsogamoorthy

Differential Revision: D26031748

fbshipit-source-id: de5164acfc141755debc0aa4f36474b1c7fd3109

Summary:
`dynamic::merge_diff` currently fully replicates `target` within the
patch.

Reviewed By: psjanani, luciang

Differential Revision: D26100408

fbshipit-source-id: f6800e665281d87393fed0bb48bda888e24bbcfc

Summary: The linked paper, the implementation and the tests use the parameter as the old value, but the parameter name is called `expected`.

Reviewed By: aary

Differential Revision: D25975108

fbshipit-source-id: bb67a95b057973e31512e9f972e1646e5a0f7d77

Differential Revision: D26084514

fbshipit-source-id: ab7e94bb0f0da04d60af7112f34c7c221125feb7

Summary: Adding simple getdeps.py manifest for f4d.

Reviewed By: amitkdutta

Differential Revision: D25842791

fbshipit-source-id: eabc33ec526c454f301f8cd401156f6250e5eaa1

Summary: Fix flakey test

Reviewed By: kevin-vigor

Differential Revision: D26090290

fbshipit-source-id: f03d6abf389815993e8742d5c27c2ccbcb13949a

Summary:
Pull Request resolved: https://github.com/facebookincubator/resctl/pull/8076

D26025779 (https://github.com/facebook/folly/commit/4731bb0c37cc39a7a689a8369c9564eddeae146c) may have broken the getdeps build when logging
surrogates. Use errors=surrogateescape to try to avoid that.

Reviewed By: danobi

Differential Revision: D26079717

fbshipit-source-id: 98d938bfced417e0b39a6dcddb241225ffb69c06

Reviewed By: nilesr

Differential Revision: D26059442

fbshipit-source-id: d323ab38d7171b344c5a15863ec8d0a70b877853

Summary: Use the 1 byte version of `once_flag` such that there is no more memory overhead than `Optional`.

Reviewed By: andriigrynenko

Differential Revision: D25909346

fbshipit-source-id: 1bb2f41200917ba58b20815bfafe3314137e9680

Summary:
`folly::MicroLock` is actually 4 locks in one. Turns out that it's not very useful considering there is not a single use in fbcode. Instead `MicroLock` should allow a nicer API for exposing the 6 unused bits as user data.

By limiting the lock to one slot (least significant 2 bits), we can make the assumption that the 6 contiguous most significant bits are user data. This means that all the masking logic can go away (see `slotMask` and `LockGuardWithDataSlots`).

Now `lockAndLoad`, `unlockAndStore`, `LockGuardWithData` "just work" with needing to worry about user data interfering with the slots used for locking.

Reviewed By: davidtgoldblatt

Differential Revision: D25909068

fbshipit-source-id: 3f050fa7393b40cff949ed6e30b691d7f40d0edf

Summary:
This diff corrects two references to `MutableStringPiece` that are misspelled
as `MutablesStringPiece` which doesn't exist.

Reviewed By: Orvid

Differential Revision: D26011095

fbshipit-source-id: 2503e13b84e04654c242bcd1f7bb17f9c1b757dc

Summary: I thought that since I noticed it, and it tripped me up a bit, we might as well fix it.

Reviewed By: LeeHowes

Differential Revision: D26048767

fbshipit-source-id: 91ba9f834df411eb2d775691be4aec8a8d99776b

Summary: `folly::compact_once_flag` is implemented using 1 byte. `folly::MicroLock` slot0 is used as the mutex for the slow path and slot1 is used for the stored boolean.

Reviewed By: andriigrynenko

Differential Revision: D25797066

fbshipit-source-id: 529de84b50e61523318a19606bc24c54f1ffa3a4

Summary:
The log file should be opened with a defined encoding rather than
whatever the platform default is. On Windows, that might be cp1252,
which throws an encoding error when the text is unicode.

Reviewed By: genevievehelsel

Differential Revision: D26025779

fbshipit-source-id: 0102b2555e91812dfe94a7c332eb896ca2c9ef7e

Summary:
As title

https://gcc.godbolt.org/z/58Mqb6

Reviewed By: Orvid

Differential Revision: D26012680

fbshipit-source-id: 7c8859fec4a5f3a58b05e4ff7924273bd05891ec

Summary: Add co-routine interface to SImpleAsyncIO.

Reviewed By: iahs

Differential Revision: D25932969

fbshipit-source-id: df14e25a0fe293a218d6bef0c4bd1bc8e690efba

Summary:
Hello,
It seems it is a missing include.
Regards,
Laurent

Pull Request resolved: https://github.com/facebook/folly/pull/1464

Reviewed By: yfeldblum

Differential Revision: D25730356

Pulled By: Orvid

fbshipit-source-id: 61faa2fdc161450909de6678c1bb8aa331260f64

folly: symbolizer: add minimal folly-addr2line tool -- intented for validation tests/debugging, not as a full-featured replacement for addr2line

Reviewed By: Orvid

Differential Revision: D25991335

fbshipit-source-id: fcdc1b1cdeab7623c67b69ce2f80b062c0935436

Summary:
Trying to use `ZeroSizeMutex` in `CallOnce.h` causes a circular dependency:
```
//folly/synchronization:call_once ->
//folly/synchronization:call_once-module ->
//folly/synchronization:call_once-module-helper ->
//folly/synchronization:zero_size_mutex ->
//folly/synchronization:baton ->
//folly/detail:memory_idler ->
//folly/synchronization:call_once
```
The benefits of `folly::once_flag` are as follows:
https://www.internalfb.com/intern/diffusion/FBS/browse/master/fbcode/folly/synchronization/CallOnce.h?commit=d0211e9462c39c4655a7d2ff9d313f6fb433d74a&lines=37-42

A fast path is not necessary here because it's just logging within an error case.
Exception-proof behavior is not needed because glog does not throw.

Reviewed By: yfeldblum, andriigrynenko

Differential Revision: D25797067

fbshipit-source-id: 4de20235ff4115b73ab8a2689e7697fc9fe4ba65

Summary: This allows `try_emplace_with` to receive objects by copy-ellision or specific moves; without it, any attempts to pass an object would result in a copy.

Reviewed By: praihan, luciang

Differential Revision: D26008949

fbshipit-source-id: b43d2dc941c7415e2189668a2b577cc0f1165665

Summary: `constexpr` is known to be broken in MSVC causing errors when using format string compilation so disable `FMT_COMPILE` there.

Reviewed By: neildhar

Differential Revision: D26019769

fbshipit-source-id: b823b24d4e73fcf9632f8e648ebb9a4e73c43bb1

Summary: As per title, as fmt doesn't currently handle them well.

Reviewed By: vitaut

Differential Revision: D26004515

fbshipit-source-id: dbbd1e6550fa10c4a6fcb0fc5597887c9411ca70

Differential Revision: D25985696

fbshipit-source-id: 52ede8dc494f8bf1991dbfed455fbc6bbba83d87

Summary:
It wasn't guarded at all, which is causing issues for non-sanitizer builds on platforms without shared library support.

Ref: https://github.com/facebook/folly/issues/1507

Reviewed By: meyering

Differential Revision: D25970872

fbshipit-source-id: f710e752fdf8ebc5529314d335f4559e690b787a

Summary: Switch to format string compilation to prevent pulling in too many symbols from the {fmt} library into `folly/detail:ip_address`. This change saves ~64k (fixed cost) in opt mode compared to the current master or ~36k compared to the old code using Folly Format. This doesn't matter for server projects especially since {fmt} will likely be linked anyway but matters for some mobile ones.

Reviewed By: Orvid

Differential Revision: D25904078

fbshipit-source-id: 56473cf9bf4456a3cb3c5aa375c16393e144b6e1

Summary: Allows us to use new APIs in libbpf

Reviewed By: anakryiko

Differential Revision: D25933787

fbshipit-source-id: f0988caae351760b814eba74f6f716db51f728bd

Summary:
Previously the `EXPECT_THROW_RE()` macro required the regular expression be
passed in as a `const char*`.  This updates the code to accept a
`std::string_view` instead.

This allows the API to accept either `const char*` arguments, `std::string`,
or `std::string_view` objects.

Reviewed By: yfeldblum

Differential Revision: D25837542

fbshipit-source-id: e6fb00034046ad7f2810367f946f0135858ed065