Summary:
- Use the hazptr library under folly/synchronization.
  - Use hazptr_obj_base_linked to manage counted links.

Reviewed By: djwatson

Differential Revision: D7674822

fbshipit-source-id: a87ece5dd1c7670677486af59988af8518abaf92

Summary:
CodeMod: `future-then-continuation-lvalue-ref`.

```
buck run mode/opt foundation/clangr:clangr_coordinator -- run foundation/clang/codemods:future-then-continuation-lvalue-ref --dev -p 7 --num-workers=200
```

There is no need to support continuations taking non-const lvalue-ref params; callers can get exactly the same semantics with non-const rvalue-ref params instead. Thsi codemod preserves semantics. Many of these cases could do just as well taking by value, but this codemod preserves semantics.

Reviewed By: Orvid

Differential Revision: D8166008

fbshipit-source-id: 84b635cccce24b6485ffb5b24b98f10422b9a517

Summary: Original commit changeset: adcd387e237d

Reviewed By: mzlee

Differential Revision: D8204982

fbshipit-source-id: 2c66f58ccf41dc70f55b3ecffc6e197c23c4f959

Summary: Fix typos

Reviewed By: Tingzhe

Differential Revision: D8160938

fbshipit-source-id: f4eaf496a33b7d2b6266a8424850640028660331

Summary:
As title.  These methods look like they never protected observers_ list, and relied on
the user not calling addObserver or removeObserver concurrently.  I don't see any downsides
to taking a write lock here, these methods aren't called often.

Reviewed By: davidtgoldblatt

Differential Revision: D8187184

fbshipit-source-id: dd20b809e851cc14a05aca3bc9722e0a9236665f

Summary: Causing perf issues.  Users must add explicitly to tests or other use cases.

Differential Revision: D8162835

fbshipit-source-id: 7095064209ced870768552307675dc1ebbf68bdc

Summary:
Add correct memory barrier to thread timeout / add path.

This seems like the fastest way to maintain safety here.  We could use
a read-biased rw lock instead, but that would mean taking a heavy memory
barrier in add() if we do have to add a thread.

Reviewed By: davidtgoldblatt

Differential Revision: D8161950

fbshipit-source-id: af2bd3a601ced9bb04a8206696e7a998c75f6369

Summary: Future::delayed could complete on Future::sleep's executor. Ensure instead that it completes on the future's executor.

Reviewed By: yfeldblum

Differential Revision: D8052038

fbshipit-source-id: adcd387e237dbd724d5f9deb5c80d1418987482d

Summary: Make onTimeout call thenError which maintains the executor rather than onError which does not.

Reviewed By: yfeldblum

Differential Revision: D8051906

fbshipit-source-id: 41ca5f657a441ff8eaacdfab6d4cfb45d5e5f0c2

Summary: This enables using Executor adaptors (e.g. SerialExecutor) with futures.

Reviewed By: yfeldblum

Differential Revision: D8198893

fbshipit-source-id: 48c59b618bd2bbad4277b7f0b0f0b19347266813

Summary:
Futures documentation was drifting out of date. The documentation index also had broken links to Futures and a core readme.

This change adds basic futures documentation in the docs tree and removed the README.md in the futures tree.

Reviewed By: marshallcline

Differential Revision: D7937360

fbshipit-source-id: 120610cca21db5a8b38199a5098551f10bb85251

Consistency with folly::SemiFuture continuations 5/n: make deferError use the same exception unpacking machinery as thenError

Summary:
Step 5 in adding full set of r-value-qualified unambiguous continuation methods to folly::Future for consistency with folly::SemiFuture.
 * Back point explicit exceptions election to deferError.

Reviewed By: marshallcline

Differential Revision: D8124828

fbshipit-source-id: 123b1cf460d2df4c8f359eff7329d34fbd8e0a9b

Summary: Add cleanup benchmark

Reviewed By: magedm

Differential Revision: D8162617

fbshipit-source-id: 5ef729913db889f999c8bb051c4291e748854000

Summary: Add a try_peek() member function valid only if SingleConsumer==true that returns folly::Optional<const T*> which (if has_value() is true) contains a pointer to the first element in the queue.

Reviewed By: djwatson

Differential Revision: D7969290

fbshipit-source-id: 3e15138f6c6523adce4da4cd99b74e0a83cd24d7

Summary:
Use folly::test::Barrier in benchmark instead of spin-waiting.  Benchmarks are more consistent now,
and perf output is useful instead of showing a bunch of spinning.

Also remove the DSched stuff from bench(), we don't want to benchmark DSched.

Reviewed By: davidtgoldblatt

Differential Revision: D8162600

fbshipit-source-id: 52a1218e7fc2b87f0926dbc29c13bf0c9478e804

Summary: Split barrier to separate file so it can be used in other tests.

Reviewed By: magedm

Differential Revision: D8162586

fbshipit-source-id: c3a239fe6fdb3f895557e7b93a5a960b9e871f0c

Summary:
[Folly] Avoid errnoeous deprecation warning in `F14BasicSet`.

The deprecation warning is emitted for instantiations like `F14FastSet<std::string>`.

The warning is triggered by looking for move-constructibility of the mapped type for maps or `void` for sets, but `void` is not move-constructible. There are a variety of techniques to solve this, and the smallest change is to use `lift_unit_t` in the right place. `Unit` is move-constructible where `void` is not.

Reviewed By: nbronson

Differential Revision: D8178045

fbshipit-source-id: 1ca06e84b4ed7acd415901afcbe80663513063ea

Summary: [Folly] Cut extra template instantiations from `Unit` traits - namely, `std::conditional` and `std::is_same`. The behavior can be done directly, while each extra template instantiations imposes some small compile-time cost.

Reviewed By: Orvid

Differential Revision: D8178033

fbshipit-source-id: 22ba5ae810e2bca616e7db332c1f635e2520f3a7

Summary:
Step 4 in adding full set of r-value-qualified unambiguous continuation methods to folly::Future for consistency with folly::SemiFuture.
 * Adds r-value qualified thenError that just call onError internally but in a more type safe obvious way.
 * Makes exception selection explicit to avoid exception_wrapper exception-type ambiguity in continuations.

Reviewed By: yfeldblum

Differential Revision: D7971326

fbshipit-source-id: 8aa94161abb629d94ee8da6fb0a4bca991cf24e4

Summary:
Step 3 in adding full set of r-value-qualified unambiguous continuation methods to folly::Future for consistency with folly::SemiFuture.
 * Undefs function-scoped defines to avoid leaking.

Reviewed By: yfeldblum

Differential Revision: D7997136

fbshipit-source-id: 4eb188bc55134da8349e984e9eb85466d7b0042c

Summary: MSVC was failing to resolve `AllocTraits` within this specific context.

Reviewed By: yfeldblum

Differential Revision: D8179354

fbshipit-source-id: 236094f704bc89ec81236e9a67054e2081590cf6

Summary:
There are quite a few things in Folly that are not compatible with C++11.

Closes: https://github.com/facebook/folly/issues/851

Reviewed By: yfeldblum

Differential Revision: D8179239

fbshipit-source-id: b4ce23b98311a7c5ac15c3b7c9787f568535c950

Summary:
Step 2 in adding full set of r-value-qualified unambiguous continuation methods to folly::Future for consistency with folly::SemiFuture.
 * Adds r-value qualified thenTry which directly forwards to then, but has compile-time restrictions on the continuations that can be passed to avoid ambiguity.

Reviewed By: yfeldblum

Differential Revision: D7944820

fbshipit-source-id: 55ee09455703bb73168694175e884b053caff426

Summary:
[Folly] Invoke SemiFutures defer-continuations with the same cvref as passed.
for example, if passed as const&&, invoke as const&&, and if passed as volatile&, invoke as volatile&.
This brings a little more consistency to the library.

Reviewed By: yfeldblum

Differential Revision: D8125144

fbshipit-source-id: f2cda643aaae40e0293d5d79608541771642ce06

Summary:
Step 1 in adding full set of r-value-qualified unambiguous continuation methods to folly::Future for consistency with folly::SemiFuture.

 * Add r-value qualified Future<T>::thenValue.
 * Make callableResult structs consistently named so they work for Future and SemiFuture.
 * Correct call behaviour for consistency with invokeCallbackReturningFutureAsRvalue test.

Reviewed By: yfeldblum

Differential Revision: D7944603

fbshipit-source-id: 081383a91749310472a8106289671cffa6139691

Summary: This gets Folly working with the zstd package provided by vcpkg.

Reviewed By: yfeldblum

Differential Revision: D8176531

fbshipit-source-id: 05fdd5915a677a862791cfcc5587f7a396fb4c51

Summary: We are changing `folly::collectAll` to return `SemiFuture` rather than `Future` and this is needed as an interim step. After all calls to `collectAll` are changed to `collectAllSemiFuture`, we'll be renaming it back to `collectAll`.

Reviewed By: yfeldblum

Differential Revision: D8157548

fbshipit-source-id: 27b768ac7ff0d6572bde57f01601045a1fd5d5e5

Summary:
Discussion in D7923362 included validity & behavior of `wait()` vs. fulfillment and `wait()` vs. `then()`.

18 test-cases:

8 cases with `.wait(...)` and fulfillment:

- Future vs. SemiFuture
- wait() vs. wait(dur)
- fulfilled before wait(...) call vs. during wait(...) call

10 cases with `.wait(...)` and `.then(...)`:

- 4 wait() cases: {Future vs. SemiFuture} that gets fulfilled {prior to, during} the wait() call.
- 6 wait(dur) cases: {Future vs. SemiFuture} that gets fulfilled {prior to, during, after} the wait(dur) call.

Reviewed By: yfeldblum

Differential Revision: D8048426

fbshipit-source-id: c79cc337706f08f8fb9c6057a114723320a90820

Summary:
This diff adds recurring tests of F14's ability to use stateful
functors with no default constructor.

This is a test-only diff.

Reviewed By: yfeldblum

Differential Revision: D8170593

fbshipit-source-id: 6ce8c7751ce32ed69b60c6884b5deb7e6378a5d1

Summary:
We are using facebook::proxygen to build Http-utility on top of it. One of the main server-connector class `Proxygen::HTTPConnector` requires `folly::HHWheelTimer` to perform timer stuff inside it.

Now, `folly::HHWheelTimer` is a very large object and we would like to avoid `folly::HHWheelTimer` creation for every new `Proxygen::HTTPConnector` therefore, we are thinking to reuse `EventBase::timer()` that creates one timer per EventBase (application creates it 1 per io thread).

But `EventBase::timer()` creates timer with default-time and caller can not modify it. Because of that other dependent component can't use it and proxygen gives below error:
```
F0522 23:50:19.629158  7775 WheelTimerInstance.cpp:71] Check failed: defaultTimeoutMS_.count() >= 0 (-1 vs. 0)
*** Check failure stack trace: ***
    @     0x7f5e6ce26e6d  (unknown)
    @     0x7f5e6ce28ced  (unknown)
    @     0x7f5e6ce26a5c  (unknown)
    @     0x7f5e6ce2963e  (unknown)
    @     0x7f5e6de8c1ad  proxygen::WheelTimerInstance::scheduleTimeout()
    @     0x7f5e6de7c059  proxygen::HTTPTransaction::HTTPTransaction()
    @     0x7f5e6deacff1  ...
    @     0x7f5e6deaa23a  proxygen::HTTPSession::createTransaction()
    @           0x4f7f93  proxygen::HTTPUpstreamSession::newTransaction()
    @           0x4ad9a4  Sherpa::HttpSession::sendRequest()
    @           0x4aee08  Sherpa::HttpSession::connectSuccess()
    @           0x4f5c69  proxygen::HTTPConnector::connectSuccess()
    @     0x7f5e6d47e414  folly::AsyncSocket::handleConnect()
    @     0x7f5e6d48769d  folly::AsyncSocket::handleWrite()
    @     0x7f5e6d47a05c  folly::AsyncSocket::ioReady()
```

- add `setDefaultTimeout()` method into timer so, application can configure it.

- No functional change but it facilitates application to configure defaultTimeout after `folly::HHWheelTimer` is created.
Closes https://github.com/facebook/folly/pull/850

Reviewed By: djwatson

Differential Revision: D8123617

Pulled By: yfeldblum

fbshipit-source-id: 4dd9b19506bea380239200b6207ac05a40a0686c

Summary:
The move constructor and move assignment operator for
allocator-aware containers is supposed to allocate new memory and
move values across when the underlying allocators are not equal.
Previously F14 just checked that this wasn't the case.  This diff
implements this feature.  This allows F14 tables to be moved into and
out of allocator-managed memory segments, such as arenas or shared
memory extents.

Reviewed By: yfeldblum

Differential Revision: D8022286

fbshipit-source-id: ff0b220450bb76822cc68cebad079a7ef43e2429

Summary:
The value passed to the eraseInto beforeDestroy callback will
be immediately destroyed, so it makes more sense for it to be an rvalue
reference than an lvalue reference.

Reviewed By: yfeldblum, shixiao

Differential Revision: D7986157

fbshipit-source-id: 9dcc5371635a860033fe901aaad3a73230d652f6

Summary:
F14 maps and sets support fancy pointers and stateful allocators.
This diff includes tests that verify this functionality and show how
boost::interprocess's location-relative pointers can be used to construct
address-independent F14 maps and sets in shared memory segments.

This is a test-only diff.

Reviewed By: shixiao

Differential Revision: D7969966

fbshipit-source-id: 77b3e2705bc7462518246a96b73e0f3f9c542c6a

Summary:
[Folly] Cut `Try` ctor taking `std::exception_ptr`.

It is legacy, from a time before `exception_wrapper`.

Reviewed By: marshallcline

Differential Revision: D8110107

fbshipit-source-id: 2d8f4d56fdf1043012d72813a8686a8d02392a0b

Summary:
[Folly] Cut `Promise::setException` overload taking `std::exception_ptr`.

It is from a time before `exception_wrapper`.

Reviewed By: marshallcline

Differential Revision: D8110117

fbshipit-source-id: f3a3f150267efc8c22a83dc90c7f52a728ef3de7

Summary:
[Folly] Cut `SharedPromise::setException` overload taking `std::exception_ptr`.

It is from a time before `exception_wrapper`.

Reviewed By: marshallcline

Differential Revision: D8132039

fbshipit-source-id: eb82f6b766fd5cf82443ef447bbc751e7319f0ab

Summary:
Currently, scheduling only allows specifying an interval, not the next run time. This makes it impossible to schedule for a given startDelay modulo the interval. This refactors things internally to use a customizable NextRunTimeFunc, and exposes a way to run at a consistent startDelay or pass in a NextRunTimeFunc.

A use case: if we have n FunctionSchedulers schedule with different startDelays but the same interval, and they sync up (e.g. they all get blocked on some IO call, which eventually gets fixed), then they won't unsync or will unsync slowly.

Reviewed By: yfeldblum

Differential Revision: D7651111

fbshipit-source-id: 3c7a49dbfaa073b913107474f039a53a0a03cfa0

Summary: This fixes a compile error on 32-bit platforms.

Reviewed By: Orvid

Differential Revision: D8147916

fbshipit-source-id: 86b66b684bed5ffb262630a361cf239948b8bb97

Reviewed By: yfeldblum

Differential Revision: D8134836

fbshipit-source-id: 0b736bd61aa024574756634358ddc0e45c31944b

Summary: Add contracts to Promise

Reviewed By: LeeHowes

Differential Revision: D7923804

fbshipit-source-id: f7f29646d523ee69f00ac8576e2edf7e003f25e3