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

Summary:
[Wangle] A thread-per-task executor.

Moved from Folly into Wangle and fleshed out.
* Starts task threads from a control thread, rather than starting task threads from the submitter thread. Because starting task threads is likely to be more expensive than moving a functor.
* Joins task threads as they finish, rather than joining all task threads in the executor's destructor.

Suitable for running tasks which spend most of their time sleeping. Such as blocking IO, blocking fork-exec-wait, etc., when it is inconvenient to use the nonblocking variants with an IO executor.

Reviewed By: simpkins

Differential Revision: D3286988

fbshipit-source-id: 4b91133a7d55332ebbae020c1515c60e816906b3

folly: fbstring: ubsan: memcpy/memmove are marked as nonnull - avoid calling them when size == 0 and (likely) source is nullptr

Summary: Also see {D3295811}

Differential Revision: D3302564

fbshipit-source-id: 3f2dbf5a6cfa8199682cb4af90aac372d501919a

Reviewed By: ot

Differential Revision: D3300437

fbshipit-source-id: 7e0add5dab6dc1c891b742b4bcedea656c8284a9

Reviewed By: meyering

Differential Revision: D3283226

fbshipit-source-id: 7ae2ec7741ca53c494e8325e30f2995a241674c0

Summary: ^, as discussed on D3279644

Reviewed By: andriigrynenko

Differential Revision: D3299473

fbshipit-source-id: dc302132db64399f768d69c641f848d0da1075c4

Summary: To make sure RequestContext is properly unset when we stop processing request on a thread. This changes the API in Fibers, NotificationQueue, HHWheelTimer and AsyncTimeout, and fixes RequestContext handling in Futures (reset RC after the callback is done)

Reviewed By: andriigrynenko

Differential Revision: D3279644

fbshipit-source-id: a6a1c2840cdce179334aa1a3b28fa514cd5358c1

Summary:
This diff standardizes `HHWheelTimer` construction. It's not that safe to allow anyone to call `new HHWheelTimer` because the caller needs to remember to call `DelayedDestruction::destroy`.

Once callers are made to be safer, I'll be able to change the `HHWheelTimer` to use standard smart pointers instead of `DelayedDestruction`.

This picks up some work that I started in D2627941 but had to postpone.

This was mostly a mechanical change:

  ( fbgs -ls 'new HHWheelTimer' ; fbgs -ls 'new folly::HHWheelTimer' ) | xargs perl -pi -e 's/\bnew\s+((?:folly::)?HHWheelTimer)\b/$1::newTimer/g'

Then I manually inspected the code. I reverted `folly/io/async/HHWheelTimer.h`, since the `newTimer` factory method is the one place that we still want to call `new HHWheelTimer`. I manually edited `proxygen/lib/utils/SharedWheelTimer.cpp`, since that was using a `shared_ptr` with a custom destructor, which isn't needed anymore. I reverted `common/io/async/d` since the D shim is meant to pass around only raw pointers. I had to replace each instance of `foo.reset(…)` with `foo = …` . Then I made manual edits to `common/clientpool/ClientPool2-inl.h` because that code wants to store the timer in a `ThreadLocalPtr`.

Reviewed By: yfeldblum

Differential Revision: D3237530

fbshipit-source-id: 96bfb6987098618ad5430c21b1314f385f04a93d

Summary: This -Wbool-compare is apparently new in GCC 5.  We should ignore it, similar to the existing suppression of -Wsign-compare.

Reviewed By: pixelb, yfeldblum

Differential Revision: D3293675

fbshipit-source-id: 5f90b0dbf049a06c0f6c3df2cdfcc8055358e367

Summary:
Error message might be < 256 bytes
in which case buf.size() would be greater
than the size of the message written out
and we might have garbled bytes at the end.

ERR_error_string_n null terminates the string
so just use that.

Reviewed By: anirudhvr

Differential Revision: D3297320

fbshipit-source-id: 2ae626ce4c49ca478806c0bcc40a390e5a84f24b

Summary: This updates FiberManager to automatically register custom stack for signal handlers. This ensures signal handlers will work correctly not only in case of stack overflow, but also if fiber stack size is just not enough for them.

Reviewed By: yfeldblum

Differential Revision: D3289912

fbshipit-source-id: 44959b727f70e1f1748d837b1a06c7414433e5ec

Summary:
This `ThreadLocalPtr::reset` overload will accept a `unique_ptr`. It's actually not totally exception safe, simply because `ElementWrapper::set` is not exception safe. The best I can say is that my additional code is exactly as safe as the underlying implemenation.

liketolivedangerously

Reviewed By: ericniebler

Differential Revision: D3271563

fbshipit-source-id: 774bcf31924b1ed4e29a6cb1c0a36ad710ab6034

Summary: While making an unrelated change, (D3271563, which was needed from an unrelated change, (D3237530)), I noticed a lack of exception safety here. If `std::bad_alloc` were thrown, then we don't want to leak memory.

Reviewed By: ericniebler

Differential Revision: D3271911

fbshipit-source-id: 0d316c0fa865a7d64622c1d62160bb0c2b061d78

Summary:
According to the POSIX definition, IOV_MAX is defined in
limits.h. Given that IOVec.h is used to provide IOV_MAX and similar,
it seems like we should add limits.h as well.

Differential Revision: D3291996

fbshipit-source-id: 238140ebef7b1b90a28f3a67a25c5f5863538fc7

Summary: Windows doesn't have sys/uio.h, so implement it. This doesn't adjust any includes of it yet, I'll leave that for a separate diff.

Reviewed By: yfeldblum

Differential Revision: D2978042

fbshipit-source-id: 16d398a856de50b6c662f739eb11dfb851096592

Summary: Add server support for TFO to wangle.

Reviewed By: Orvid

Differential Revision: D3275427

fbshipit-source-id: 466baa342e2e0c4751e9c96d1e660cffb90e0634

Summary:
abs(-INT_MIN) is UB. Avoid it by first casting the number to
its unsigned equivalent and then negating that.

Reviewed By: yfeldblum

Differential Revision: D3280835

fbshipit-source-id: 40922d686173e6467e15d5a6dc2b62ad718349b5

Summary:
MSVC builds of libevent expect `evutil_socket_t` to be `HANDLE` values, but Folly, HHVM, and Thrift all use them as file descriptors.
This adds a `folly_event_set` function that always expects a file descriptor rather than a socket. This also changes the places in Folly that use it.

Reviewed By: mzlee, yfeldblum

Differential Revision: D2874655

fbshipit-source-id: 66cfd86fd69a9fbac30d150445e4814cd5ca799e

Summary:
We shouldn't rely on the internal buffer size of openssl
for errors.

This makes it more explicit.

Reviewed By: knekritz

Differential Revision: D3285918

fbshipit-source-id: 452bf16a3de151d0aa79c774f2fdfc1e08ee6f9c

Summary: Add NETWOR_ERROR to switch so it doesn't fall into Invalid Exception block.

Differential Revision: D3282448

fbshipit-source-id: 2cc5d21e436e6ac8f2f6581d99341ac47cf5b023

Reviewed By: siyengar

Differential Revision: D3264727

fbshipit-source-id: fb10558096e73a3cbb6f2fb93296524c0206910d

Summary:
These are pretty trivial. Debian's lint tool (lintian) warns about those
in its verbose mode, and since we saw them when packaging for Debian, we
thought of fixing them and forwarding them upstream.
Closes https://github.com/facebook/folly/pull/345

Reviewed By: Orvid

Differential Revision: D2769801

Pulled By: elliottneilclark

fbshipit-source-id: ad37cc53792f21aae6558ba256f20cb56c6caab5

Summary:
These didn't work properly in GitHub.
Closes https://github.com/facebook/folly/pull/375

Differential Revision: D3281872

Pulled By: elliottneilclark

fbshipit-source-id: b5398267ff5856bb6a7c4a3b963ae5cb47859bc3

Summary:
It would be nice to fix, but it's going to be easier to do when folly
support is for GCC>=5 which adds `__builtin_add_overflow`.

For now disable the check as the Histgram code handles overflow
correctly and has tests for these cases.

Fixes need to be done for both float and integer types as Histogram is used with both.

Reviewed By: meyering

Differential Revision: D3280260

fbshipit-source-id: 56e524c517566a4547346859be7770eda2acee96

Summary:
The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated
  bits are filled with zeros.

  If E1 has a signed type and non-negative value, and E1 × 2E2 is
  representable in the result type, then that is the resulting value;
  otherwise, the behavior is undefined.

The code assumed the signed left shift worked like an unsigned left
shift, so make that explicit.

Reviewed By: meyering

Differential Revision: D3280325

fbshipit-source-id: 178b95ee36b7a1126a79bb825c2ad2ffa6fa9464

Summary:
third-party-buck/build/libgcc/include/c++/4.9.x/bits/stl_vector.h:866:9: runtime error: reference binding to null pointer of type 'char'

```
Breakpoint 2, 0x0000000000494894 in __ubsan_handle_type_mismatch_abort ()
(gdb) bt
```

Reviewed By: meyering, yfeldblum

Differential Revision: D3279234

fbshipit-source-id: 63a761587e5b3f79ece09fc99b9a593da0e44b75

Summary: MSVC's preprocessor is different in how it deals with passing arguments expanded from `__VA_ARGS__`, so we have to add a stub to force it to expand the arguments.

Reviewed By: yfeldblum

Differential Revision: D3256328

fbshipit-source-id: 551434833d40e55498a9ab352eb74acdfd094835

Summary: MSVC doesn't define `__cplusplus` as a high enough value to trigger this, so add an explicit check for MSVC instead.

Reviewed By: yfeldblum

Differential Revision: D3271647

fbshipit-source-id: a1e5a5a7eb75dce066dfc7fae8b2086880dc4c3d

Summary:
before:

  [ RUN      ] RangeFunc.Vector
  bits/stl_vector.h:866:9: runtime error: reference binding to null pointer of type 'int'

Reviewed By: yfeldblum

Differential Revision: D3279253

fbshipit-source-id: 957a8ec050f5c3b27febf7e6cd16ad1d307da169