Summary:
This is part of "the great r-valuification of folly::Future":

* This is something we should do for safety in general.
* Using lvalue-qualified `Future::get()` has caused some failures around D7840699 since lvalue-qualification hides that operation's move-out semantics - leads to some use of future operations that are really not correct, but are not obviously incorrect.
* Problems with `Future::get() &`: it moves-out the result but doesn't invalidate the Future - the Future remains (technically) valid even though it actually is partially moved-out. Callers can subsequently access that moved-out result via things like `future.get()`, `future.result()`, `future.value()`, etc. - these access an already-moved-out result which is/can be surprising.
* Reasons `Future::get() &&` is better: its semantics are more obvious and user-testable. It moves-out the Future, leaving it with `future.valid() == false`.

Codemod steps (where `get(...)` means both `Future::get()` and `Future::get(Duration)`):

* expr.get(...) ==> std::move(expr).get(...)  // if expr is not already an xvalue
* expr->get(...) ==> std::move(*expr).get(...)

Note: operator precedence of that last step is safe - no need to parenthesize `expr`. Reason: `->` binds more tightly than unary `*`.

Reviewed By: yfeldblum

Differential Revision: D8683752

fbshipit-source-id: 593bcd92ca4e11244e0f912cf956538889a2c777

Summary:
We built folly with upcoming Visual Studio 15.8, which failed with the following message:
error C2338: You've instantiated std::aligned_storage<Len, Align> with an extended alignment (in other words, Align > alignof(max_align_t)). Before VS 2017 15.8, the member type would non-conformingly have an alignment of only alignof(max_align_t). VS 2017 15.8 was fixed to handle this correctly, but the fix inherently changes layout and breaks binary compatibility (only for uses of aligned_storage with extended alignments). Please define either (1) _ENABLE_EXTENDED_ALIGNED_STORAGE to acknowledge that you understand this message and that you actually want a type with an extended alignment, or (2) _DISABLE_EXTENDED_ALIGNED_STORAGE to silence this message and get the old non-conformant behavior.

This enables the `_ENABLE_EXTENDED_ALIGNED_STORAGE`.

Closes https://github.com/facebook/folly/pull/881

Reviewed By: Orvid

Differential Revision: D8689152

Pulled By: yfeldblum

fbshipit-source-id: fada301a163b0b09adc76807dc0e7bd26d9740a9

Summary:
In the same vein as some previous diffs: some `boost` headers are expensive.  These `iterator_facade` and related headers (which include -facade.h) are examples of super expensive ones.

`boost/iterator/iterator_adaptor.hpp` in particular shows up as being responsible for appx. 7.5% (avg) of translation units built.

The solution here is: since this bloats `folly/dynamic-inl.h`, in that "private" impl file, I added a workalike class, which is minimal and works well enough to do the job for dynamic's iterators.

Reviewed By: yfeldblum

Differential Revision: D8329532

fbshipit-source-id: deaab7b52d110cd29c613d687a6a74c6a42b515d

Summary:
Iterator helper classes are used in several places around Folly; they're convenient because they take care of some of the details while letting your class provide only a few of the necessary pieces.

Boost has `iterator_facade` and `iterator_adaptor` to help in these cases, but the header for these classes are absurdly expensive to include (their transitive includee tree is quite large).

For this reason, we'll add similar helper classes, with minimal dependencies, under detail.  In subsequent diffs we'll migrate some existing code using these boost classes (or implementing iterators itself) to use these helpers.

Reviewed By: yfeldblum

Differential Revision: D8345073

fbshipit-source-id: 3e6656e544349fe228358074de30c89c805e2628

Summary: [Folly] Fix incorrect copy constructions in `ConcurrentHashMap`, where the `ConstIterator` is move-only but the code attempts to copy it.

Reviewed By: magedm

Differential Revision: D8678003

fbshipit-source-id: 89d47b811fb27ecbbd42cae03a2af13becd0082a

Summary:
[Folly] `invoke_type` members for free- and member-invoke traits containers.

Usable as:

```
FOLLY_CREATE_FREE_INVOKE_TRAITS(swap_invoke_traits, swap, std);
// ...
swap_invoke_traits::invoke_type my_swap;
my_swap(obj1, obj2);

Reviewed By: aary

Differential Revision: D8670799

fbshipit-source-id: 0c24912721aa20ca9647261e24ed3eb0e340ab20

Summary:
[Folly] Refactor apply-invoke traits. Can make them smaller by extracting a common denominator and then falling back on the base invoke traits.

Also fixes the build for MSVC2015.

Reviewed By: aary

Differential Revision: D8676590

fbshipit-source-id: f59c7014d3294f3b0978c2fd027cf3a87411f639

Summary:
If `MemoryIdler` is used with threads that are backed by huge pages, the
`madvise(..., MADV_DONTNEED)` calls will fail with an `EINVAL`. Prior to this
diff, this would lead to an assertion failure. Now, if `EINVAL` is returned, we
warn the user, as `MemoryIdler` may not be able to function as expected.

Reviewed By: yfeldblum

Differential Revision: D8669399

fbshipit-source-id: f97ea7549deffdbf283b3516b9e8feafe18a036c

Summary: [Folly] Simpler free-invoke traits. Only supports one namespace housing a base definition. For the typical case of `swap`, with a base definition in `namespace std`, this works.

Reviewed By: aary

Differential Revision: D8666221

fbshipit-source-id: abfd302e430ad7151c119e98a706201265d302d3

Summary: Make the pthread key a singleton

Reviewed By: yfeldblum

Differential Revision: D8663589

fbshipit-source-id: 1e0c328104bd8c3d3c689dc4955a185336e74276

Summary:
`throw` within a `noexcept` function triggers a compiler warning on the latest clang in C++17 mode.

As the behavior of uncaught `throw` within a `noexcept` context is to terminate the program, do so explicitly.

Reviewed By: yfeldblum

Differential Revision: D8651221

fbshipit-source-id: 004c4c132ad9b5b873a92cf2710b9d1ebe4e705b

Summary:
The compiler will likely remove the branch on destruction because
it's never used

Reviewed By: yfeldblum

Differential Revision: D8651868

fbshipit-source-id: ef16b9d11569f72aa0fa89cb6aa2450a58d783e7

Summary:
D8395569 added a prefetch instruction as part of iterator advance
for F14Value and F14Node maps.  This caused the work to advance the
iterator returned by erase to no longer be recognized as dead code by the
GCC optimizer.  This diff separates out advance() and advanceLikelyDead()
methods, avoiding prefetch in the latter case.

Reviewed By: shixiao

Differential Revision: D8656038

fbshipit-source-id: 86cecf40e8622f815d34a98709b90d6ef73dd618

Summary:
D8586283 added an implicit conversion from allocator_type to a
uint8_t-rebound allocator, but allocators might provide only an explicit
rebinding constructor.  This diff makes F14 use the explicit form.
It also adds a binary that when debugged (in a buck build environment)
is useful for evaluating code size.

Reviewed By: shixiao

Differential Revision: D8655289

fbshipit-source-id: c977edb041ce2056f3ce23c52a7f8464a6b9f1bd

Reviewed By: igorsugak

Differential Revision: D8653359

fbshipit-source-id: 5bb33792aa96a0ed7f88a672100955f366c568da

Summary: [Folly] Free function invoke traits.

Reviewed By: andriigrynenko

Differential Revision: D8632204

fbshipit-source-id: 1f5f6e31072ef3a711edab02b6b7bbad8c894a95

Summary:
[Folly] Tweaks to member-invoke traits.
* `const`.
* No need to delegate to `invoke`.

Reviewed By: aary

Differential Revision: D8632393

fbshipit-source-id: 08ae3bc6e3ede3766ec646a5d2588996ff734538

Summary: To avoid affecting existing use cases that were caught by the check.

Reviewed By: itomatik

Differential Revision: D8657069

fbshipit-source-id: 55a54022c5d5bc4a5d332270df7f2fa9a9b5e05e

Summary: To accommodate a use case.

Reviewed By: itomatik

Differential Revision: D8656154

fbshipit-source-id: 9d2961d7921bdd399fc8c46820d1ba3aa5006c6f

Summary:
The type must provide a StringPiece constructor or be convertible
via `folly::to<UserDefinedType>(string)`; toAppend() must also be defined for
the reverse construction.

Differential Revision: D8586230

fbshipit-source-id: 80159bc1cc9d32f0ae40af8f053387f341bea835

Summary: Use FOLLY_EXPORT for StaticMetaBase::getThreadEntryList()

Reviewed By: yfeldblum

Differential Revision: D8640044

fbshipit-source-id: 0907af4b091681a986ac2b0e963bc1c5258dd5c1

Summary:
Similar to the invoke family of traits
https://en.cppreference.com/w/cpp/types/is_invocable, this introduces the same
for the case where arguments are wrapped in a tuple

Reviewed By: yfeldblum

Differential Revision: D8626830

fbshipit-source-id: 145eb71c7bb142ff07ebad716572b5e8340d2c9c

Summary: Detect frequent calls to hazptr_tc::fill. This is usually indicative of unnecessary overhead, either due to insufficient thread cache capacity for legitimate use cases, or due to unnecessary allocation of extra hazard pointers in user code.

Reviewed By: yfeldblum

Differential Revision: D8606484

fbshipit-source-id: e75223f8bc3e180a1ee651ee2989522d6b0a89df

Summary: A simple helper to construct an index sequence from a given tuple type

Reviewed By: yfeldblum

Differential Revision: D8626776

fbshipit-source-id: a4ea412293981d58e91a921dcae8468849f5f0bf

Summary: As title

Reviewed By: elsteveogrande

Differential Revision: D8643234

fbshipit-source-id: 989cdc53ed071fd78a1eba4b2955eff7651274f1

Summary: Disable unsafe iterator operations: copying and operator++ (because it copies the iterator). Copying is unsafe because starting to protect buckets and nodes after their removal is not guaranteed to be effective.

Reviewed By: yfeldblum, djwatson

Differential Revision: D8594743

fbshipit-source-id: 0990d8fe979a3217db855641d23e24cc853a25bf

Summary:
Add a backport of `std::apply` with a similar implementation that makes it easy
to reason about.  Also implement `applyTuple` in terms of `apply`, `invoke` and
`tuple_cat`

The implementation of `apply` has been taken straight from the standard,
reducing chances of churn in incompatible assumptions (if any).  Note that the
definition and declaration of `apply` has been changed from the way it is
specified in the standard for better SFINAE compatibility, if needed, will
followup with a paper proposing the same change in the standard

Reviewed By: spacedentist

Differential Revision: D8248199

fbshipit-source-id: e3e76193a30b1599eca3fe986a33f61addad7a59

Summary: title

Reviewed By: yfeldblum

Differential Revision: D8631916

fbshipit-source-id: be4ef689b9c2b0dcdd92f8ea61787f70f9a71f9c

Summary:
This diff adds 32-bit support for F14, so SSE and NEON
intrinsics can be used on x86 and arm architectures (rather than just
x86_64 and aarch64).  The portability fallback to std::unordered_map
and std::unordered_set is now used only when vector intrinsics are not
available, or on PPC.

Reviewed By: shixiao

Differential Revision: D8586283

fbshipit-source-id: 1c4d090e80381fe7ad071c3059b3cb242c04c9f7

Summary:
This diff adds helper methods for allocating
possibly-over-aligned types using C++ allocators.  It uses one of three
strategies:

* REBINDING - When there is a type that is not over-aligned with the
requested alignment, the allocator is rebound to that a type with the
correct alignment (this allows allocating 1 char with alignment 8,
for example).

* BYPASSING - When the requested alignment is larger than max_align_t
but the standard allocator is in use, the allocator is bypassed and
aligned_malloc/aligned_free are used directly to manage the allocation.

* OVER-ALLOCATING - When the type is truly over-aligned and the allocator
is custom, extra memory is requested and a delta is stored before the
returned memory to allow the original base location to be recovered.

Reviewed By: shixiao

Differential Revision: D8592767

fbshipit-source-id: 487b5ff7f7f6b1b29a3f2a80d07129afd50bda24

Summary: Increase thread cache capacity from 3 to 6 hazard pointers to accommodate 2 ConcurrentHashMap iterators.

Reviewed By: yfeldblum

Differential Revision: D8595800

fbshipit-source-id: 53275c3cf6fb11c976a4da987d79ec33b9e5e617

Summary:
To reduce unnecessary copying for user code handling ConstIterator-s.

Added move test and change UpdateStressTest to use few concurrent iterators.

Reviewed By: yfeldblum

Differential Revision: D8587056

fbshipit-source-id: d6b592a3aa40ca8a7599b258b45a1d339088c978

Summary: `folly::as_const` instead

Reviewed By: yfeldblum

Differential Revision: D8248219

fbshipit-source-id: 22853d86c93065ee584458f18b7cd0e8d528d2f0

Summary: Faster thread local iteration using the ThreadEntryNode

Reviewed By: djwatson

Differential Revision: D8551597

fbshipit-source-id: 9118852c0a823851a95b63fe807bfc2679112beb

Summary:
Change the folly/future/... tests to use mainly[*] the rvalue-qualified versions of get() and get(dur).

[*] Although the lvalue-qualified get is deprecated, it is not yet removed, so this diff leaves a test for the lvalue-qualified version. But the bulk of the tests are for the rvalue-qualified get.

Reviewed By: yfeldblum

Differential Revision: D8239792

fbshipit-source-id: c8a2e90cb5ab97a59ec97994c8c6a6ca27dab86e

Summary: [Folly] Fix forwarding/moving in Futures `reduce`.

Reviewed By: marshallcline

Differential Revision: D8601105

fbshipit-source-id: 96c1632821e9e5088a900ccecdaff9f8d108b905

Summary: We have to extend DeferredExecutor to be aware of nested DeferredExecutor, so that it can propagate various signals to them.

Reviewed By: LeeHowes

Differential Revision: D8600961

fbshipit-source-id: 2b9520598cad65bd80f0346e6f76e224903780a1

Summary:
[Folly] Let Futures `Barrier::ControlBlock` ctor fully construct.

Invoke the constructor when allocating the control block, rather than try to initialize each field afterward.

Differential Revision: D8605292

fbshipit-source-id: d51648a1267ed7e3e13d9a9e8d8e5d1c18e24a98

Summary:
[Folly] Be explicit about memory orders in Futures.

This clarifies the basic purpose of each atomic variable - namely, whether it protects control flow (relaxed) v.s. state (typically acq/rel).

Reviewed By: davidtgoldblatt

Differential Revision: D8472791

fbshipit-source-id: 350ec9b38d7c36cfb6d9ae9f1abf758b1f2e97ba

Summary: When converting to folly::Future we have to perform the void -> folly::Unit conversion.

Differential Revision: D8463177

fbshipit-source-id: 96312d0447dfc381a0ee586030f21b9cdbf4bee4