Summary:
The Folly `make check` build is broken with Clang on OS X.

This diff fixes the following break in `make check`:

  make[3]: *** No rule to make target `../futures/test/ThreadedExecutorTest.cpp', needed by `../futures/test/ThreadedExecutorTest.o'.  Stop.

The problem is a reference to a file which was moved to `wangle` in D3286988.

Reviewed By: simpkins

Differential Revision: D3361287

fbshipit-source-id: a9ae794374982b4accf806bd9608988430c75cfd

Summary: AsyncSocket::handleWrite may trigger HTTPSession::onWriteSuccess which may totally delete the HTTPSession. AsyncSocket::handleWrite also calls bufferCallback_->onEgressBufferCleared(). That bufferCallback_ is the HTTPSession. So in this diff resets bufferCallback_ to nullptr upon HTTPSession shutdown. afrind had a suggestion of adding a DestructorGuard in AsyncSocket::handleWrite. But i don't know DestructorGuard that well. I think it will keep AsyncSocket from being deleted but not the HTTPSession? Or maybe I can DestructorGuard dg(bufferCallback_) ?

Reviewed By: afrind

Differential Revision: D3311058

fbshipit-source-id: cdb5fcbd53837a3effbc096eab87fca4e5d17291

Summary:
Min rto is now 50ms, so change the
test accordingly

Reviewed By: w-o-o

Differential Revision: D3357140

fbshipit-source-id: 5a807fabc1a3c216a5120b8eb4930e5c1eb52b7a

Summary:
Contrary to the other `append` flavors, `fbstring::append(size_type n, value_type c)`
does not use exponential growth, which can trigger quadratic behavior.

Reviewed By: philippv

Differential Revision: D3357315

fbshipit-source-id: 2301ed1a9953544368663107113890a25c6621ae

Summary:
MSVC generates warnings if you define multiple assignment operators or multiple copy constructors on the same type. This is deliberate in `folly::Function`, so just disable the warnings for the struct instead.
Note that the warnings have to be disabled for the entire struct for them to actually be disabled. Disabling them just around the declarations of the constructors and operators in question does not actually disable the warnings.

Reviewed By: yfeldblum

Differential Revision: D3347746

fbshipit-source-id: abb53a1e62bcfb7ce02759a7ce8637d824a82081

Summary:
The two function definitions in this file are both normal function definitions,
not template functions.  Therefore this should be just a normal .cpp file, and
not a -defs.h header file.

Reviewed By: igorsugak

Differential Revision: D3348439

fbshipit-source-id: 3ebe49c84493f5aab06c568d9df15a37c2c48836

Summary:
The default constructor creates the Subprocess in an uninitialized state.  This
makes it possible to default-construct a Subprocess, but only initialize it
later using the move assignment operator.

Even before this diff, it was possible to have Subprocess objects in
uninitialized states after using the move assignment operator to move the data
out of a Subprocess object.

Reviewed By: yfeldblum

Differential Revision: D3348490

fbshipit-source-id: aa6acef9be770de8f0ee118da294cb134f04a466

Summary: There is no equivalent functionality for Windows, so disable it completely.

Reviewed By: andriigrynenko

Differential Revision: D3348481

fbshipit-source-id: 52a104f5a8013113f54d5b10c2f0f9b720eeb4f6

Summary: Because, as MSVC rightly tells us, it's not actually defined anywhere.

Reviewed By: yfeldblum

Differential Revision: D3347654

fbshipit-source-id: 2162bc745136ee0129caa4de78f38e1361083cd1

Summary:
Because apparently I didn't actually add the `Windows.h` include when I added support for MSVC.
This is safe for all platforms because the portability header only includes `Windows.h` when compiling on Windows.

Reviewed By: yfeldblum

Differential Revision: D3347785

fbshipit-source-id: 4f3e4e6c11953e2588b6fed287324a92e3ef8873

Summary: Apparently I failed to accurately transfer this particular change to fbcode, which meant it didn't actually compile on Windows.

Reviewed By: yfeldblum

Differential Revision: D3347976

fbshipit-source-id: 775682f10ab68672f6463ccc69a222ae0a52a097

Summary:
The existing Cursor::peek() method pre-dates the existence of folly::ByteRange,
and so it returns a std::pair containing a pointer and length.  This is usually
more awkward to use than ByteRange.

This adds a peekBytes() method that returns a ByteRange object, and updates all
users of peek() in folly to use peekBytes() instead.  Eventually I think we
should add a FOLLY_DEPRECATED attribute to peek().  I will wait to add this tag
until after converting a few other projects to use peekBytes(), though.

Reviewed By: alandau

Differential Revision: D3337302

fbshipit-source-id: 14220a059d915bf5adc66b8b283f7228b796a4dc

Summary:
We should use folly::make_unique instead of std::make_unique in order to support
compilers without support for C++14.

Reviewed By: pavlo-fb

Differential Revision: D3343288

fbshipit-source-id: 9150af752e57988962a7580851ffa32086c669d7

Summary: MSVC is a massive pain in this respect, and, after testing many workarounds, and only ending up with it just emitting a dynamic initializer for them, it's easier to just generate the table as a `uint64_t` and load it explicitly.

Reviewed By: yfeldblum

Differential Revision: D3270226

fbshipit-source-id: 77bc84e58d393373de05a28a30dcb80b66c09c9f

Summary:
If a TemporaryDirectory with scope DELETE_ON_DESTRUCTION gets moved
and then goes out of scope, the directory will be deleted while the moved
object still holds that path; we just clear the path from the old object to
prevent this

Reviewed By: yfeldblum

Differential Revision: D3331079

fbshipit-source-id: 9c99413661e2436ccec937d3fa652da810133b34

Summary:
As part of my campaign to get `HHWheelTimer` away from intrusive ref-counting semantics, (cf. D3237530), I am redefining `HHWheelTimer::SharedPtr`. It is now a true `std::shared_ptr`. This will break clients that attempt the following:

  HHWheelTimer::UniquePtr timer1{HHWheelTimer::newTimer()};
  HHWheelTimer::SharedPtr timer2{timer1};

In the past, that code would compile, because `timer2` could use the intrusive ref-counting, and `timer1` would still be valid. After this change, the second timer would need to be initialized with `std::move(timer1)` instead. The `UniquePtr` is starting to actually be unique.

There is only one place in the code that actually tries to do such a copy. It's in a test, which I have changed. Any other instances of that behavior would create a compilation error, so it's impossible for one to be overlooked.

Reviewed By: djwatson

Differential Revision: D3337038

fbshipit-source-id: 085e4da41c9a142d253a1ac0b1dd0fc508dff704

Summary: Actually __assume when we assume.

Reviewed By: meyering

Differential Revision: D3336033

fbshipit-source-id: 6c931e9f832dd1d861d03e3ad8e308f612522401

Summary:
[Folly] Avoid `std::initializer_list` ctor in `folly::dynamic::array`.

This will help deprecate the dangerous initializer-list constructor. The init-list construction is dangerous because its semantics vary by compiler and by compiler version.

Reviewed By: ot

Differential Revision: D3333148

fbshipit-source-id: 031e7593b7e28b299d5eeeb5ce7aed9216dd3a5c

Summary:
LoopKeepAlive handle can be grabbed to signal that some external event will later be scheduled on the EventBase via runInEventBaseThread. Usually the code which will be calling runInEventBaseThread only has a raw pointer to an EventBase, so it doesn't have any way to know it was destroyed.

This change ensures that EventBase destructor will keep running the event loop until all such LoopKeepAlive handles are released.

Reviewed By: yfeldblum

Differential Revision: D3323835

fbshipit-source-id: 4071dae691a61dfebe2f1759cf99f661b161fa4a

Summary:
The configure script doesn't define `FOLLY_HAVE_PREADV` if `preadv` isn't supported, so these checks were wrong. Undefined defines expand to `0`, so this is safe.
Fixes https://github.com/facebook/folly/issues/412

Reviewed By: mzlee, yfeldblum

Differential Revision: D3329405

fbshipit-source-id: faee8951c68d4c67e06e7720dfc142e63a9dbd9f

Summary:
This diff templates folly::fibers::await by Baton.
This would be helpful in passing in custom BatonType's, which is needed for D3007734

Depends on: D3314891

Reviewed By: andriigrynenko

Differential Revision: D3314925

fbshipit-source-id: 9052dc503b9509f16cd41b5e3ede0479a98067aa

Summary:
The current use case of `std::memory_order_consume` in this project was intended to provide the appropriate synchronization in cases where a consumer spins on `while( spsc_queue.empty() ) {} `, and then attempts to use an element of the queue since the loop was broken out of, according to comments [here](https://reviews.facebook.net/D48141). Consume semantics do not provide this guarantee according to the standard since there is no data dependency from the producer that can be carried to the consumer by doing a load-consume from the corresponding functions. What is needed is a load-acquire. Current compilers promote `memory_order_consume` to `memory_order_acquire`. Thus, this example appears to work simply due to the promotion from consume to acquire, but would fail to generate the right synchronization instructions on weaker architectures once `memory_order_consume` is implemented as intended.  Therefore, the `memory_order` should be tightened to `memory_order_acquire` to guarantee visibility to the consumer
Closes https://github.com/facebook/folly/pull/381

Reviewed By: djwatson

Differential Revision: D3173574

Pulled By: nbronson

fbshipit-source-id: b109be2e74f016750a3fe1f848e3fc66e609b9d2

Summary:
[Folly] Extract `Try` to top-level.

It was in `folly/futures/`, but this diff moves it to `folly/`.

It is needed for futures, but it is are more general than futures and can be used separately.

Use `folly/Try.h` instead of `folly/futures/Try.h`.

Also fixes up all `#include` sites:

    hg grep -lw folly/futures/Try | xargs perl -pi -e 's,\bfolly/futures/Try\b,folly/Try,g'

Reviewed By: markisaa

Differential Revision: D3309908

fbshipit-source-id: cdf13f0ac0b0e36aa07e0f1d04870d06500c5874

Summary:
```
buck-out/gen/folly/__default_headers__#default,headers/folly/FBString.h:365:7: runtime error: null pointer passed as argument 2, which is declared to never be null
third-party-buck/build/glibc/include/string.h:70:33: note: nonnull attribute specified here
    #0 0x433a39 in _ZZN5folly13fbstring_coreIcEC1EPKcmbENKUlvE_clEv ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////buck-out/gen/folly/__default_headers__#default,headers/folly/FBString.h:365:7
    #1 0x4335a9 in _ZN5folly14ScopeGuardImplIZNS_13fbstring_coreIcEC1EPKcmbEUlvE_E7executeEv ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////buck-out/gen/folly/__default_headers__#default,headers/folly/ScopeGuard.h:153:29
    #2 0x4335a9 in _ZN5folly14ScopeGuardImplIZNS_13fbstring_coreIcEC1EPKcmbEUlvE_ED2Ev ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////buck-out/gen/folly/__default_headers__#default,headers/folly/ScopeGuard.h:130
    #3 0x4335a9 in folly::fbstring_core<char>::fbstring_core(char const*, unsigned long, bool) ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////buck-out/gen/folly/__default_headers__#default,headers/folly/FBString.h:427
    #4 0x4353fa in folly::basic_fbstring<char, std::char_traits<char>, std::allocator<char>, folly::fbstring_core<char> >::basic_fbstring(char const*, unsigned long, std::allocator<char> const&) ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////buck-out/gen/folly/__default_headers__#default,headers/folly/FBString.h:1038:9
```

Reviewed By: Gownta

Differential Revision: D3321266

fbshipit-source-id: 28d5aef16e91a98066a1de6bab95403fbc63eaab

Summary: folly::fibers have been used by mcrouter for more than 2 years, so not really experimental.

Reviewed By: pavlo-fb

Differential Revision: D3320595

fbshipit-source-id: 68188f92b71a4206d57222993848521ca5437ef5

Summary:
This diff adds a static await method to Promise.
Also after this, folly::fibers::await is just a wrapper around Promise::await.
This also removes the friend relationship between Promise and await.

This would be helpful in making the folly::fibers::await templated by Baton changes easier to make.

Reviewed By: andriigrynenko

Differential Revision: D3314891

fbshipit-source-id: 361546c078caafd067734d2f474c617d7fb888b0

Summary:
[Folly] Make `Try` independent of `Future`.

`Try` is useful for futures, but it can be used independently from futures as well.

Reviewed By: djwatson

Differential Revision: D3319130

fbshipit-source-id: badfcaa482dee6e7bdef14a501b4efc91634fa51

Reviewed By: yfeldblum

Differential Revision: D3317666

fbshipit-source-id: f5558b117c8da74789ee444cdaa00231e75dc31e

Summary: Closes https://github.com/facebook/folly/pull/403

Reviewed By: yfeldblum

Differential Revision: D3320043

Pulled By: elliottneilclark

fbshipit-source-id: 5d21421216180fb601015a40a3de79e3dd2a162e

Summary:
[Folly] Flesh out the comments about `Unit`.

* Remove mention of `Future`.
* Compare `unit` to `void`.

Reviewed By: djwatson

Differential Revision: D3316114

fbshipit-source-id: d30cf36cc029025734bb16c5bdbd640a289cad79

Summary:
[Folly] Extract `Unit` to top-level.

It was in `folly/futures/`, but this diff moves it to `folly/`. It is needed for futures, but it is more general than futures and can be used separately.

Users must replace `folly/futures/Unit.h` with `folly/Unit.h`.

Also codemods existing usage sites:

```
hg grep -lw folly/futures/Unit.h | xargs perl -pi -e 's,\bfolly/futures/Unit\.h\b,folly/Unit.h,g'
```

Reviewed By: igorsugak

Differential Revision: D3314280

fbshipit-source-id: 16279b76b1d24529bec49077ccb36cd7d39f23b8

Summary:
Added a version of IOBuf::wrapBuffer() which returns the new IOBuf by value rather than heap-allocating it.
Motivation: we have a lot of places in the crypto code that do something like this:

  // take a string or vector parameter
  auto buf = folly::IOBuf::wrapBuffer( /* string or vector goes here */);
  // do something with buf
  // return

In these cases, a stack-allocated IOBuf would save us from an unnecessary heap allocation. But calling `folly::IOBuf(folly::IOBuf::WrapBufferOp::WRAP_BUFFER, ...)` is gross and in practice people just call the much more readable `wrapBuffer()` function. Hypothesis: readability trumps performance, but if we had a readable version that returned a stack-allocated IOBuf, it might see usage.

Reviewed By: yfeldblum

Differential Revision: D3314037

fbshipit-source-id: 4d4b5ec1d067762a27de1d7d6f7cac406388bfa3

Summary:
Baton::post has to be the last step of Promise::setTry. If Promise is not owned by
the posting thread, it may be destroyed right after Baton::post is called.

Reviewed By: pavlo-fb

Differential Revision: D3312506

fbshipit-source-id: 6d5c3f0925c3bb9cd3f981e7550f888d5ed76189

Summary:
[Folly] Keep the `Unit` test suite free of `Promise` and `Future`.

Move the `Promise`-related tests to the `Promise` test suite and the `Future`-related tests to the `Future` test suite.

Reviewed By: djwatson

Differential Revision: D3313635

fbshipit-source-id: 05c82c8719719d7709063ad58a4806036ca10fb3

Summary:
[Folly] Simplify `Unit`.

Specifically:
* Make `Unit::Lift` and `Unit::Drop` simply be aliases to `std::conditional<...>`. No need for anything more complicated.
* Remove `is_void_or_unit`, which is unused and unnecessary.

Reviewed By: djwatson

Differential Revision: D3312481

fbshipit-source-id: 280d40aa8ef91c52f96a51b03e0a109d76c939ec

Reviewed By: meyering, luciang

Differential Revision: D3310683

fbshipit-source-id: c86471d54062b2f3455f15fb73340fac486d9e44

Summary: [Folly] `IPAddress::validate`.

Reviewed By: igorsugak

Differential Revision: D3308683

fbshipit-source-id: 48af18d6930f16718372021a4cc08062bf17327e

Summary:
This fixes a race which can only be exposed if Promise is owned by the same thread which was calling await and Promise is fulfilled from a different thread. What could happen then was:
1. Thread 2 fulfills the promise and thus saves the value and posts Baton.
2. Thread 1 wakes up, await returns and then Thread 1 destroys the Promise.
3. Promise destructor checks value_, which is still not null, so it tries to fulfil it with exception.

Reviewed By: spalamarchuk

Differential Revision: D3306969

fbshipit-source-id: adf799cfd7b75b0201fa675a9e44ac7c7c42ac95

Summary: This fixes fibers::await to correctly handle exception thrown by user-passed lambda. Await still always waits for the promise to be fulfilled (if the promise was not moved out, it will be destroyed and thus auto-fulfilled with "promise not fulfilled" exception). However if user-passed lambda throws, promise result is ignored (even if exception) and exception thrown by lambda is re-thrown.

Reviewed By: pavlo-fb

Differential Revision: D3303393

fbshipit-source-id: c4ba01fde0e156cc88e5d07aaf763e3abe121d11

Summary:
[Folly] Prefer `constexpr` to preprocessor conditionals when checking endianness.

Using `if (folly::kIsLittleEndian) {` v.s. `#if __BYTE_ORDER__ == __LITTLE_ENDIAN__`.

Reviewed By: meyering

Differential Revision: D3296770

fbshipit-source-id: b26df83fdd42a50663746fc7c9d5fbe67e6671eb