Summary:
C++ up to and including C++17 lacks an alternative to std::back_inserter() that uses emplace_back() instead of push_back(). This causes unnecessary temporary objects in some cases, when using std::back_inserter() together with STL functions such as std::copy() or std::transform(). The same holds for std::front_inserter() and std::inserter().
This diff introduces folly::back_emplacer(), folly::front_emplacer(), folly::emplacer(), and related iterator classes, which call emplace_back(), emplace_front(), and emplace() respectively, with perfect forwarding of any arguments to the output iterator's operator=.
Includes support for variadic emplacement / multi-argument constructors through a utility function folly::make_emplace_args() which packs its arguments into a special tuple for use with operator=.

Reviewed By: ericniebler

Differential Revision: D4897174

fbshipit-source-id: c85c30c457e0c946938051819baa662d1a0b8ca1

Summary: There are still some upstream references to `folly::make_unique` that need to be removed before it can be full killed, but this gets it most of the way there.

Reviewed By: yfeldblum

Differential Revision: D5024310

fbshipit-source-id: 6cfe8ea93662be18bb55588c8200dec72946e205

Summary:
Change every instance of EXPECT_EQ(false, ... to the simpler/shorter EXPECT_FALSE(...
Likewise, convert each EXPECT_EQ(true, ... to EXPECT_TRUE(...

Differential Revision: D5019004

fbshipit-source-id: 0203f10fa47237f869a75a057ac4456ef03e1f53

Summary:
There's nothing io/async/ssl-specific in this file. Moving to the
top-level directory will help this be more discoverable. Part of general cleanup
for io/async/ssl

Reviewed By: yfeldblum

Differential Revision: D5005566

fbshipit-source-id: 66a05a2139ee80a6d63791d1851da3f1858e8abf

Summary:
A faster crc32 impl for folly.  Similar to crc32c, except
intel doesn't provide crc32 directly in hardware - instead, pclmul can be used,
which is ~2x slower than crc32c, but still ~5-10x faster than software implementation.

Reviewed By: Orvid, yfeldblum

Differential Revision: D4994761

fbshipit-source-id: ad8ba856649eea6dc7b541d561329ff7d7fe2d60

Summary: std::call_once implementation is broken if function throws. This fixes folly::call_once to not depend on std::call_once.

Reviewed By: yfeldblum

Differential Revision: D5015897

fbshipit-source-id: bcbda68becf0930cdbf0b09125cbee61d75c2015

Summary: [Folly] Mark future-core get-state members as `const noexcept`.

Reviewed By: andrewjcg

Differential Revision: D5014358

fbshipit-source-id: e39b0b63c59267a4ecfab5aac02e6d96ce2e7e00

Summary:
[Folly] Stop trying to `setrlimit(RLIMIT_AS)` in ASAN builds.

ASAN needs to reserve plenty of memory outside of the limited address space imposed by the call to `setrlimit`.

Reviewed By: andriigrynenko

Differential Revision: D5014679

fbshipit-source-id: 2ab71b1cca9297d3a276cf72154fac30a2057f86

Summary: It should be possible to perform simple comparison operations between a FixedString and a std::string. By adding asymmetric comparison operators with FixedString and Range, we make FixedString comparable with anything convertible to Range, including std::string.

Reviewed By: yfeldblum

Differential Revision: D5007704

fbshipit-source-id: fee89d8807ac2d5378eec0d0a51eb8684976a271

Summary: OSX was sad. Now it should be happy.

Reviewed By: mzlee

Differential Revision: D5011751

fbshipit-source-id: 77f22ff461036d8530d8f650396d8e12503448e7

Summary:
[Folly] Control the number of threads in `TestExecutor`.

Let the caller control the number of threads to use in each given case.

Reviewed By: spacedentist

Differential Revision: D4999699

fbshipit-source-id: 4acf68cf17fbca14f0779daf0268d54c5606e4a8

Summary:
We have tests that check that the Future implementation deals
cleanly with executors discarding tasks. The existing tests destroy
the tasks immediately when they are passed to Executor::add. This
diff adds corresponding tests for the scenario where the task is
not destroyed right away, but after the call to Future::then has
completed.

This diff also adds a mechanism to detect that the passed callback
function is actually destroyed. We have tested already that the
promise returned by folly::then will be set to a BrokenPromise
exception when the executor discards the task. However, the task
passed to the executor is not only the callback we pass to
folly::then, as the Future implementation wraps it with some code
that stores the return value in a Promise. Existing tests check
that this Promise is destroyed. The added mechanism in this diff
checks that the orignal callback function itself gets destroyed.

Reviewed By: Krigpl

Differential Revision: D5002100

fbshipit-source-id: 4155f61b075d9fe8d1869ad229f4d350571ff4c6

Summary:
[Folly] Add full `noexcept` annotations to `Indestructible`.

And do it without requiring `<type_traits>`.

Reviewed By: Orvid

Differential Revision: D4999243

fbshipit-source-id: f3521237ef4d03d2b187e9ebd6d0c90887872c42

Summary: This can only ever be used unsafely, so delete it.

Reviewed By: yfeldblum

Differential Revision: D4951294

fbshipit-source-id: bbc266d1550fceb48946c7c48e76af07292b4a53

Summary:
The setThreadName API is in the process of being changed to not accept a thread id, which means the thread itself needs to set the name.
There are times where a `ScopedEventBaseThread` needs to be named, and this makes that possible.

Reviewed By: yfeldblum

Differential Revision: D4916781

fbshipit-source-id: dab05b520a715183ce069151ed16864fa1331abc

Summary: It's primarily for use in testing, but is useful for log output as well.

Reviewed By: yfeldblum

Differential Revision: D4943072

fbshipit-source-id: 0ca259d6c90f439e733a6179e7cba85dcd1ec9e7

Summary: This template uses flat combining and takes any sequential priority queue implementation that supports the `std::priority_queue` interface (`empty()`, `size()`, `push()`, `top()`, `pop()`) and any lock that meets the standard //Lockable// requirements to implement a thread-safe priority queue that supports arbitrary priorities. The template supports both unbounded and bounded size, and blocking, non-blocking, and timed variants of push, pop, and peek operations.

Reviewed By: djwatson

Differential Revision: D4873602

fbshipit-source-id: 96e1548b4f7427ecd2ee2ead7a19993df4441b33

Summary: Access the RTTI of the incomming exception before it is potentially moved from when testing for slicing

Reviewed By: yfeldblum

Differential Revision: D4999189

fbshipit-source-id: 3e6c0a9f10a27810484330e9b37a5b0ec450ff88

Summary:
folly::File's throwing constructor results in many try-catches in the callsites
or bugs where the exception is not caught.

This is a helper method to return an Expected with system_error wrapped into an
exception_wrapper.

Reviewed By: yfeldblum

Differential Revision: D4995702

fbshipit-source-id: be0e22b37c21c35bf157ada598916b05dfd32631

Summary:
No need to store the pointers to forward and skip arrays if
they're not used.

Reviewed By: luciang

Differential Revision: D4977014

fbshipit-source-id: 2ed13fdcd1561da1a294f5895f3a5e1b77f1701c

Summary: Shrink the reader type if less than 64 bits are sufficient for sizes. Do the same for `BitVectorCoding`, where we don't need an extra template parameter because the size is limited by the value domain.

Reviewed By: philippv, luciang

Differential Revision: D4976756

fbshipit-source-id: 685047da81a556d049fb924c612f99cea3056a82

Summary: It is not used anywhere except for `previousValue`, but there it can be computed from the other fields. This reduces the `EliasFanoReader` size by 8 bytes.

Reviewed By: philippv, yfeldblum

Differential Revision: D4976704

fbshipit-source-id: 62bc63248b66649e483b59cb9ddf48dfd2c0e992

Summary:
Computing the mask on access has negligible cost as it can be
hoisted out of the linear search loop, and furthermore on Haswell we
can use the the `BZHI` instruction.

I also experimented with `BEXTR` but it ended up being slower because
computing the pattern operand requires a shift and an or (it's
probably meant for when the pattern is precomputed).

Reviewed By: philippv

Differential Revision: D4976657

fbshipit-source-id: e4c4ca5f0a785595587e6d6ad4676f5b216291cf

Summary:
If a retired object's destructor retire()s other hazard pointers, currently
these are not cleaned up correctly when the domain destructs.

Retired pointers must be cleaned up before destroying hazptr_recs, and must be done
iteratively until no more garbage is generated.

Reviewed By: magedm

Differential Revision: D4987333

fbshipit-source-id: bcdd61abb47caca0892a8c4dbb864d17d4f2fa30

Summary:
The first issue is that I was missing a `G` in `LIBGFLAGS_INCLUDE_DIR` meaning that it always claimed it couldn't find gflags even though it did, and worked just fine anyways.
The second issue is that it was passing `/permissive-` to MSVC 2015 builds, even though MSVC 2015 doesn't support the permissive flag.

Reviewed By: yfeldblum

Differential Revision: D4988813

fbshipit-source-id: f1ea009226baee54032409ce7add3c41f1fe7a19

Summary: I was bad and didn't follow through on my previous test plan, and so didn't check that it completely fixed the issue, instead only fixing one of the two problems. This fixes the other one.

Reviewed By: yfeldblum

Differential Revision: D4988408

fbshipit-source-id: 44389bc67bcb7d6db984075f3600948460fa8c5a

Summary: Besides this code being utterly bizzare, it doesn't work under MSVC 2015 Update 3, so rather than doing a `static_cast<bool>(std::conjunction<>())` just do `std::conjunction<>::value`.

Reviewed By: yfeldblum

Differential Revision: D4988341

fbshipit-source-id: ededdbf3f3d945d9e2f140f4e87643ec3c0d4239

Summary: MSVC 2015 Update 3 is even worse in this particular case, and requires it to be explicitly referenced as being within the `folly` namespace >_>...

Reviewed By: ot, yfeldblum

Differential Revision: D4988025

fbshipit-source-id: dea311dd42f40b442951b8df3c5f68cf70d13769

Summary: I broke things, so now I have to fix them.

Reviewed By: yfeldblum

Differential Revision: D4981674

fbshipit-source-id: 7df4d78cf4f984df158051a3a8b277a0bcad583b

Summary: MSVC requires the declaration to match a bit closer than GCC does.

Reviewed By: yfeldblum, ot

Differential Revision: D4981404

fbshipit-source-id: 92ee40c40f66725c09a3087e49d99ebae222c2f2

Summary: In the subscribe callback It's possible that we lock the Context shared_ptr and while update is running, all other shared_ptr's are released. This will result in Context to be destroyed from the wrong thread (thread runnning subcribe callback), which is not desired.

Reviewed By: yfeldblum

Differential Revision: D4964605

fbshipit-source-id: 285327a6873ccb7393fa3067ba7e612c29dbc454

Summary: A bunch of changes to make fbcode targets build with OpenSSL 1.1.0

Reviewed By: ivmaykov

Differential Revision: D4949822

fbshipit-source-id: 35eda632d8335c4194352196264afeff69d87519

Summary:
Superseded by `<folly/portability/Constexpr.h>`'s `constexpr_strlen()`.
Closes https://github.com/facebook/folly/pull/585

Reviewed By: yfeldblum

Differential Revision: D4973136

Pulled By: Orvid

fbshipit-source-id: ada9bedf53ce219b0924c3f7aaad75bce9605f0f

Summary:
- `FunctionScheduler` and `EventBase` are great for sharing one thread for many functions, but one-function-per-thread is messy.
- Both of those implementations are complicated, but `FunctionThreads` is dead-simple.
- I made it even simpler by eliminating the former `incrementalSleep` in favor of `std::future::wait_for`, which allows instant interruption without a tweakable param. h/t aru777 for suggesting `std::future` instead of `std::condition_variable`.

Reviewed By: yfeldblum

Differential Revision: D4742134

fbshipit-source-id: b520bbcd5f218b2276200ffe8926722ae8a8d6ca

Reviewed By: yfeldblum

Differential Revision: D4965608

fbshipit-source-id: db8d67ca7174e0296fbd8da2e1fe90cbbcef9496

Summary:
Class template that wraps a reference to an rvalue. Similar to std::reference_wrapper but with three important differences:
1) folly::rvalue_reference_wrappers can only be moved, not copied;
2) the get() function and the conversion-to-T operator are destructive and not const, they invalidate the wrapper;
3) the constructor-from-T is explicit.
These restrictions are designed to make it harder to accidentally create a a dangling rvalue reference, or to use an rvalue reference multiple times. (Using an rvalue reference typically implies invalidation of the target object, such as move-assignment to another object.)

Reviewed By: yfeldblum

Differential Revision: D4931483

fbshipit-source-id: 68453553bf4656ec41976699669a4491fcab79c9

Summary:
`cpuid` uses all of `eax`, `ebx`, `ecx`, `edx` for output, but we
aren't providing such information to GCC in a couple of cases, which might
result in incorrect code being produced;

GCC (unlike clang) doesn't allow the same register to appear both in input and
clobber list, so put `eax` into output list where required.

Reviewed By: ot, lbrandy

Differential Revision: D4961841

fbshipit-source-id: 07ca1977373496bfd794d3b0c8a4ba21333820e4

Summary: There's a gotcha case for IOBufQueue::split when  n==0, it will then return an unique_ptr wrapping a nullptr, which many call sites do not expect.

Reviewed By: meyering

Differential Revision: D4868228

fbshipit-source-id: 418256dba8ca3bcfbae420b6099baa240055b9bb

Summary: Added a lock holder with deferred option for cases where the caller may want to call try_lock() later.

Reviewed By: djwatson

Differential Revision: D4949736

fbshipit-source-id: 31e0dc349dc3af9d04a33878e26cef1e48cce674

Summary: [Folly] Casing consistency for `exception_wrapper::throw_exception`.

Reviewed By: Orvid

Differential Revision: D4944818

fbshipit-source-id: 72056fb24ab6362e9a0319f73b5bbf8c92d658ca