Add an exception for building on OSX.

Summary: The Homebrew setup fails to compile on OSX.

Reviewed By: @paulbiss

Differential Revision: D2212084

folly::Unit::Drop.

Summary: [Folly] folly::Unit::Drop.

Antisymmetric to folly::Unit::Lift.

Reviewed By: @fugalh

Differential Revision: D2211725

minor Timekeeper bug

Summary: Fix so `Timekeeper::at(now() - something)` works. Also introduce a test which explicitly tests when <= now codepath, which wasn't broken per se here, but which test also tickled this bug.

Reviewed By: @jsedgwick

Differential Revision: D2209166

Discourage Duration in code comments and tests

Reviewed By: @yfeldblum

Differential Revision: D2209095

Future<Unit> global fixup

Summary: This is three codemods:

* `(folly::(Future|Promise|Try))<void>` -> `\1<folly::Unit>`
* `(Future|Promise|Try)<void>` -> `\1<Unit>`
* add `using folly::Unit` statements where needed

Then
* undo false positives in javascript files and fibers::Promise

cf D2201259, which this will land with

Reviewed By: @djwatson

Differential Revision: D2201801

Future<Unit> wangle fixup

Summary: Mostly this is `s/(Promise|Future|Try)<void>/\1<Unit>/`

Reviewed By: @djwatson

Differential Revision: D2201272

Nuke Future<void> (folly/futures)

Summary: Nuke Future<void> in favor of Future<Unit>, for the `folly/futures` subdirectory.

Reviewed By: @djwatson

Differential Revision: D2201259

Do an explicit test for XSI strerror_r

Summary: The current #if directive is a laundry list of
"strerror_r defaults to XSI style on these platforms",
and we keep missing some, so let's just do a proper test
and simplify the code directives.

Closes #232

Reviewed By: @paulbiss

Differential Revision: D2208843

(easy) wrong test suite name

Reviewed By: @yfeldblum

Differential Revision: D2209197

Implement a BitVector-based list

Summary: Implemented a BitVector Encoder and BitVector Reader with the same interface as EliasFanoCoding.h

Reviewed By: @ot, @philippv

Differential Revision: D2198935

fix? AutoTimerTest

Summary: Apparently this test sometimes fails. @Gownta suggests it's because we're
storing temproaries in StringPiece. Change it to store in a std::string, which
should hopefully fix it.

Reviewed By: @Gownta

Differential Revision: D2208643

make it really clear that wangle/rx is deprecated

Summary: More people are starting to use Rx. Yay! But they're trying to use `wangle/rx`. So make sure there's no doubt about its deprecated status.

Reviewed By: @yfeldblum

Differential Revision: D2196273

Add missing include for flock()

Summary: flock() expects sys/file.h which on many platforms
is getting included as a side-effect, but on at least one
this isn't the case.

Add the explicit include to fix builds on those platforms.

Closes #232

Facebook

Unrelated runtime failures.

Reviewed By: @JoelMarcey

Differential Revision: D2196306

make folly/detail/FunctionalExcept.* work if FOLLY_HAVE_BITS_FUNCTEXCEPT_H is set or not

Summary: When doing android development, we need to compile with
FOLLY_HAVE_BITS_FUNCTEXCEPT_H set for some flavors, and
FOLLY_HAVE_BITS_FUNCTEXCEPT_H unset for others (primarily for tests
run in the local (xcode) development platform).  This diff adds some
more conditionals so it all works.

In this repro, these files are never used, so this is more or less a
noop, but this is the upstream so I'm making these changes here.

Reviewed By: @Gownta

Differential Revision: D2202107

check ReadCallback before using it

Summary: before the first setReadCallback(), the readCallback_ is nullptr.  Thanks @siyengar for pointing out this!

Reviewed By: @siyengar

Differential Revision: D2203489

move the socket setting into setReadCB()

Summary: refactor D2201181

Reviewed By: @afrind

Differential Revision: D2202245

Bump version to 48:0

a subset of folly now compiles with Windows mingw64 toolchain

Summary: a subset of folly now compiles with Windows mingw64 toolchain

Reviewed By: @djwatson

Differential Revision: D2171872

cleanup includes in folly/Format.h

Summary: `folly/Format.h` pulls in `folly/small_vector.h` and
`folly/FBVector.h`, which (according to @​oleksandr's analysis)
are the most expensive includes for multiple fbcode projects.

Reviewed By: @ot

Differential Revision: D2198904

Fix resplit | batch

Summary: Resplit violated the contract of `apply()`; it returned `false` even though the input sequence was fully consumed.

Reviewed By: @philippv

Differential Revision: D2195889

Remove double-conversion as a source dep in OS X script

Summary: double-conversion was recently added to homebrew, making it the last
folly dependency to do so. this diff modifies the existing OS X
bootstrap tool to account for that. I also added an rm for the gtest
wget, so there wasn't a leftover zip file in your repo. alternatively,
we could remove that and add it to the gitignore.

Reviewed By: @fugalh

Differential Revision: D2196000

Pulled By: @sgolemon

Fix passing RequestContext to executor thread

Summary: If x->add() executes its lambda on a different thread and
doesn't pass the context on its own, the callback wouldn't
have the correct context set.

Reviewed By: @djwatson

Differential Revision: D2189318

Fix stop_ thread race

Summary: make it std::atomic

Reviewed By: @tudor

Differential Revision: D2191861

to_shared_ptr.

Summary: [Folly] to_shared_ptr.

So you can write this:

    auto sptr = to_shared_ptr(getSomethingUnique<T>());

Instead of this:

    auto sptr = shared_ptr<T>(getSomethingUnique<T>());

Useful when `T` is long, such as `T = foobar::cpp2::FooBarServiceAsyncClient`.

Reviewed By: @meyering

Differential Revision: D2193572

opt proxygen with newly added OpenSSL functions

Summary: this taks advantage of SSL_write_iovec and SSL_read_buf functions to improve CPU.  This eliminates one malloc+memcpy+free operation for all HTTPS traffic, and save up to two for small packets.

It saves 10~15% CPU
https://fburl.com/99681397
https://fburl.com/99427544

Reviewed By: @djwatson

Differential Revision: D1993764

GroupBy

Reviewed By: @ot

Differential Revision: D2188740

(easy) remove cruft comment

Summary: We have this now.

Reviewed By: @jsedgwick

Differential Revision: D2191642

(Wangle) Fix possible race in updating FSM state

Summary: Storing the new state could be a memory race according to C++ (but wasn't in practice). I only checked GCC though.

Reviewed By: @nbronson

Differential Revision: D2189287

(Wangle) Clean up some data races in tests

Summary: Not 100% about the `ThreadWheelTimekeeper` test. It makes TSAN happy
though.

Reviewed By: @yfeldblum

Differential Revision: D2187901

(Wangle) Fix bug with CrappyExecutors, and bad PriorityExecutor

Summary: 1) We forgot to `--attached_` if `x` throws an exception
2) `PriorityExecutor` didn't execute `Func`, causing leaks in the test (not a bug in Futures)
3) I moved up the initialization for an empty `Core` into the constructor to make it easier to see

Reviewed By: @jsedgwick

Differential Revision: D2187343

Don't hardcode thread limit in ServerBootstrap

Summary: This was set to 32 which probably works fine for the
majority of FB servers, but not everyone's system is so endowed.

Closes #119

Reviewed By: @fredemmott

Differential Revision: D2187008

(Wangle) Remove unnecessary constructor argument to CollectAnyContext

Summary: See title.

Reviewed By: @fugalh

Differential Revision: D2186833

Fix tests for glog and gflags

Summary: The existing tests were trying to find undocumented
symbols in glog/glags which aren't guaranteed to be there on all
platforms.

Use AC_RUN_IFELSE() to try building and executing some code
typical of the usage of these libraries.

Closes #117

Reviewed By: @JoelMarcey

Differential Revision: D2183526

Change visibility of folly::Arena constructors to public

Summary: In the case of the copy constructor, this change
doesn't really matter, since it's deleted anyway.

In the case of the move constructor, it fixes what was probably
an unintentional hiding.  The class certainly looks like
it supports moving.

Closes #121

Reviewed By: @yfeldblum

Differential Revision: D2184131

Fix copy/pasta in docs

Summary: svformat explicitly takes a container for direct indexing,
but the format string used is per-arg, which corresponds to format/sformat.

Closes #228

Reviewed By: @JoelMarcey

Differential Revision: D2184334

Update README.md to refer to homebrew Formula

Summary: Release builds should probably favor using
@marpaia's brew Formula to get a release build.

Leave the boostrap script around to simplify building
from master.

Closes #229

Reviewed By: @jwatzman

Differential Revision: D2184416

(Wangle) Possibly undefined behavior in collect

Summary: Not sure if this is really undefined behavior or whether UBSAN is just super paranoid. Will try to read up on it later.

I also changed some other `std::atomic` initialization to always follow the same pattern, let me know if I should revert those. I couldn't resist, OCD kicked in.

idonthaveocd

Reviewed By: @fugalh

Differential Revision: D2181074

Provide backfill s6_addr16 on BSD platforms

Summary: Extend the MacOS s6_addr16 hack to Net/Open/FreeBSD

Closes #106

Reviewed By: @JoelMarcey

Differential Revision: D2182912

Futex: ignore errors on wake

Summary: See the comment for details

Reviewed By: @nbronson

Differential Revision: D2181231

rearrange Pipeline to have more functionality in PipelineBase

Summary: This way, handlers can carry out more complex manipulations of the pipeline via ctx->getPipeline() without knowing the R/W types

Reviewed By: @djwatson

Differential Revision: D2158736

Fix for clang (llvm 3.7.0+)

Summary: Roughly described in https://github.com/facebook/hhvm/issues/5344.

Closes #206

Reviewed By: @yfeldblum

Differential Revision: D2170803

Pulled By: @sgolemon

Remove -Wno-inconsistent-missing-override suppression in folly

Summary: It is fixed in gmock. No need to suppress it in sources.

Reviewed By: @meyering

Differential Revision: D2181564

instance Eq Unit

Summary: [Folly] instance Eq Unit

    Unit::operator==(const Unit&)
    Unit::operator!=(const Unit&)

Reviewed By: @Gownta

Differential Revision: D2179384

Add missing override and remove redundant virtual in folly

Summary: Running clang-tidy to fix this problem, using script D2171334.

I noticed that even without this change clang dev build succeeds for folly and opened a separate task to investigate why.

Reviewed By: @markisaa

Differential Revision: D2179299

Add ./configure check for vsnprintf returning negative on error

Summary: This is slightly more correct than assuming that
__APPLE__ is the only place this assumption breaks.

Pulled from relevant section of folly-PR#95, other sections
are either already applied by other fixes, or have been code-moved.

Closes #95

Reviewed By: @jwatzman

Differential Revision: D2178439

Building instructions for MAC OS X (MacPorts)

Summary: Tested on Mac OS X 10.10.3 and MacPorts 2.3.3.
Closes #227

Reviewed By: @yfeldblum

Differential Revision: D2176700

Pulled By: @sgolemon

Bump version to 47:0

new small_vector tests that fail on trunk and uncover a bug in emplace_back on references to memory inside the vector + a fix + perf improvement to const lvalue push_back

Summary: emplace_back() on a small_vector applied on data inside the vector doesn't work properly.
In standard vectors, this usage is required to work properly, but I'm not sure whether it should in small_vector. Consider fixing / adding a lint rule.

Reviewed By: @yfeldblum

Differential Revision: D2122931

ARM64 assembler fixes for Folly.

Summary: Wrap asm("pause") in an inline so that it becomes
asm("wfe") on aarch64.

Closes #187
Closes #190

Reviewed By: @yfeldblum

Differential Revision: D2152868

Pulled By: @sgolemon

then() ropagates exceptions properly

Summary: fixed then() exceptions propagation and added unit-test

Reviewed By: @fugalh

Differential Revision: D2159075

Move folly::compression::Instructions to a separate file

Summary: Moved abstraction layer for platform-specific bit-manipulation instructions from the EliasFanoCoding.h to Instructions.h since we will need to use it also for BitVectors:

Reviewed By: @ot

Differential Revision: D2165314

move SharedMutex from folly/experimental to folly

Summary: SharedMutex has been in heavy production use for a while with no
bugs reported and no API changes requested, it is no longer experimental.

Reviewed By: @yfeldblum

Differential Revision: D2165275

Check array get for < 0

Summary: dynamic's integer type is signed, so make sure array indices
are not negative.

(See https://our.intern.facebook.com/intern/tasks/?t=7445055)

Reviewed By: @Gownta

Differential Revision: D2145689

use Unit in Pipeline

Summary: Instead of the one-off Nothing struct

Reviewed By: @yfeldblum

Differential Revision: D2158621

various perf improvements

Summary: Three strategies
1. Optimistic locking
2. Acquire-release memory ordering instead of full sequential consistency
3. Some low-hanging branch miss optimizations

Please review carefully; the dogscience is strong with this one

```
Before:

============================================================================
folly/futures/test/Benchmark.cpp                relative  time/iter  iters/s
============================================================================
constantFuture                                             127.99ns    7.81M
promiseAndFuture                                  94.89%   134.89ns    7.41M
withThen                                          28.40%   450.63ns    2.22M
----------------------------------------------------------------------------
oneThen                                                    446.68ns    2.24M
twoThens                                          58.35%   765.55ns    1.31M
fourThens                                         31.87%     1.40us  713.41K
hundredThens                                       1.61%    27.78us   35.99K
----------------------------------------------------------------------------
no_contention                                                4.63ms   216.00
contention                                        80.79%     5.73ms   174.52
----------------------------------------------------------------------------
throwAndCatch                                               10.91us   91.64K
throwAndCatchWrapped                             127.14%     8.58us  116.51K
throwWrappedAndCatch                             178.22%     6.12us  163.32K
throwWrappedAndCatchWrapped                      793.75%     1.37us  727.38K
----------------------------------------------------------------------------
throwAndCatchContended                                        1.35s  741.33m
throwAndCatchWrappedContended                    139.18%   969.23ms     1.03
throwWrappedAndCatchContended                    169.51%   795.76ms     1.26
throwWrappedAndCatchWrappedContended            17742.23%     7.60ms   131.53
----------------------------------------------------------------------------
complexUnit                                                127.50us    7.84K
complexBlob4                                     100.14%   127.32us    7.85K
complexBlob8                                     100.16%   127.30us    7.86K
complexBlob64                                     96.45%   132.19us    7.57K
complexBlob128                                    92.83%   137.35us    7.28K
complexBlob256                                    87.79%   145.23us    6.89K
complexBlob512                                    81.64%   156.18us    6.40K
complexBlob1024                                   72.54%   175.76us    5.69K
complexBlob2048                                   58.52%   217.89us    4.59K
complexBlob4096                                   32.54%   391.78us    2.55K
============================================================================

After:
============================================================================
folly/futures/test/Benchmark.cpp                relative  time/iter  iters/s
============================================================================
constantFuture                                              85.28ns   11.73M
promiseAndFuture                                  88.63%    96.22ns   10.39M
withThen                                          30.46%   279.99ns    3.57M
----------------------------------------------------------------------------
oneThen                                                    231.18ns    4.33M
twoThens                                          60.57%   381.70ns    2.62M
fourThens                                         33.52%   689.71ns    1.45M
hundredThens                                       1.49%    15.48us   64.58K
----------------------------------------------------------------------------
no_contention                                                3.84ms   260.19
contention                                        88.29%     4.35ms   229.73
----------------------------------------------------------------------------
throwAndCatch                                               10.63us   94.06K
throwAndCatchWrapped                             127.17%     8.36us  119.61K
throwWrappedAndCatch                             179.83%     5.91us  169.15K
throwWrappedAndCatchWrapped                     1014.48%     1.05us  954.19K
----------------------------------------------------------------------------
throwAndCatchContended                                        1.34s  749.03m
throwAndCatchWrappedContended                    140.66%   949.16ms     1.05
throwWrappedAndCatchContended                    164.87%   809.77ms     1.23
throwWrappedAndCatchWrappedContended            49406.39%     2.70ms   370.07
----------------------------------------------------------------------------
complexUnit                                                 86.83us   11.52K
complexBlob4                                      97.42%    89.12us   11.22K
complexBlob8                                      96.63%    89.85us   11.13K
complexBlob64                                     92.53%    93.84us   10.66K
complexBlob128                                    90.85%    95.57us   10.46K
complexBlob256                                    82.56%   105.17us    9.51K
complexBlob512                                    74.13%   117.12us    8.54K
complexBlob1024                                   63.67%   136.37us    7.33K
complexBlob2048                                   50.25%   172.79us    5.79K
complexBlob4096                                   26.63%   326.05us    3.07K
============================================================================
```

Reviewed By: @djwatson

Differential Revision: D2139822

Using emplace_back to avoid temporary

Summary: Directly pass the arguments to respective constructors.
Instead of first making temporary and then pass that.

Closes #218

Reviewed By: @yfeldblum

Differential Revision: D2156978

Pulled By: @sgolemon

Bump version to 46:0

Fix leaks in tests

Summary: Fix leaks in unit tests

Reviewed By: @djwatson

Differential Revision: D2153681

Implement previousValue on EliasFanoReader

Summary: It is often useful to retrieve the value preceding the current value
in an Elias-Fano iterator, for example when the list represents
adjacent ranges. This diff implements a new method `previousValue` in
`EliasFanoReader`.

It also adds a new `kUnchecked` boolean template argument to
`EliasFanoReader` which skips bounds checking.

Reviewed By: @philippv

Differential Revision: D2155049

pipeline handler removal, fix service test

Summary: add remove<T>, remove(Handler*), removeFront(), removeBack() to Pipeline
employ these to fix up reusing client pipelines with client dispatchers, which in turn fixes the broken ServiceTest

Reviewed By: @djwatson

Differential Revision: D2152636

Move AtomicUnorderedInsertMap to folly.

Summary: AtomicUnorderedInsertMap is a concurrent hash table that firmly
at the performance end of the generality <-> performance spectrum.
If you don't need updates (or can use your own concurrency control when
overwriting values), you never need to delete, and you can predict your
capacity perfectly, then you will get wait-free reads, lock-free inserts,
safe concurrent iteration, and excellent cache and performance outlier
behavior.  Arbitrary key and value types are supported.

Reviewed By: @yfeldblum

Differential Revision: D2145281

do not suppurt compress and expand

Summary: the openssl improvement does not support compression and decompression.

Reviewed By: @Invalid auth token., @afrind

Differential Revision: D2151003

Revert "Using emplace_back to avoid temporary"

Summary: This reverts commit 0968dcc2f0e02998fa53007853e0c0aad0a423b7.

Reverts D2151582

Reviewed By: @​iainb

Differential Revision: D2153840

Check readCallback before calling handleRead

Summary: Since readCallback_ could be uninstalled in any of callbacks,
we need to ensure that readCallback_ != nullptr before calling
handleRead.

Reviewed By: @djwatson

Differential Revision: D2140054

ExceptionWrapper: use std::decay in implicit constructor

Summary: Because Ex resolves to SomeException&, and then all the tests in optimize<>
fail.

Reviewed By: @yfeldblum

Differential Revision: D2152893

Merge pull request #225 from wb14123/dup

Remove duplicate header file
Somehow this was already correct in the internal repo, but not the external one.
Thanks!

Remove duplicate header file

Using emplace_back to avoid temporary

Summary: Directly pass the arguments to respective constructors.
Instead of first making temporary and then pass that.

Closes #218

Reviewed By: @JoelMarcey

Differential Revision: D2151582

Pulled By: @sgolemon

Get *=default*ed default constructors

Summary: Defaulted (*=default*ed) default constructors are better
because they can be constexpr and/or noexcept when C++ Standard
thinks it is right to do so. And they remain user-declared rather
than user-provided. Regarding *=default*ed default constructor,
benifit is that the work might be done during compilation and we
might not need to worry about exception paths. And for destructors,
apart from that that =defaulted definition is in sync with defaulted
default constructor we might discover that in some cases "() {}" might
be ill-formed when "= default;" compiltion indicates so. If =defaulted
definition for destructor doesn't do any harm then why not go for it.

Closes #216

Reviewed By: @yfeldblum

Differential Revision: D2145322

Pulled By: @sgolemon

Needless temporary gone

Summary: We might be doing:
1) Create a temporary
2) Copy/Move out of it
3) Destroy that temporary.
Which isn't needed in many places.
And copy/move elision doesn't work for a temporary
bound to a reference.

We can forward arguments, directly.
To get the work done three constructors were added.

Closes #222

Reviewed By: @JoelMarcey, @yfeldblum

Differential Revision: D2151731

Pulled By: @sgolemon

Added fiber supported mutex to folly

Summary: To be able to use fiber lock in thrift

Reviewed By: @brianwatling, @yfeldblum

Differential Revision: D2149936

Add EOS checking to 'parseLeadingNumber' function.

Summary: parseLeadingNumber does not contain EOS validation and raise an exception when '/sys/devices/system/cpu/cpu0/index0/shared_cpu_list' contains only one number like '0'.
Closes #207

Reviewed By: @yfeldblum

Differential Revision: D2148015

Pulled By: @sgolemon

apple-gate ThreadLocal in fibers code

Summary: Some internal malloc shims broke on using folly::ThreadLocal, so only do that for `__APPLE__`.

Reviewed By: @brianwatling

Differential Revision: D2151318

Suppress clang memcpy warnings

Summary: Clang warns when types with vtables are memcpy'd. If the type
has declared itself to be relocatable, then this is the desired
behavior. If the type has not declared itself to be relocatable, then
the memcpy codepath is dead. However, the dead codepath is still
instantiated (it's inside an if block with a static check, but c++
doesn't have static-if), so the compiler spits out a nasty warning
anyways.

Each memcpy reference inside of fbvector has been void-ified. I have
looked at all the codepaths leading to the memcpys, and see that they
have isRelocatable or isTriviallyCopyable checks.

Reviewed By: @markisaa

Differential Revision: D2148286

Temporarily disable performWriteIovec

Summary: As in title

Reviewed By: @djwatson

Differential Revision: D2151092

Recycle heap on assignment

Summary: For standard containers, assignment tries to reuse heap space.
Dynamic assignment does not - it calls destroy(), and then reconstructs
a new dynamic. In the case that the old and new types are the same (eg
assigning a dynamic-vector to a dynamic-vector) we can call through to
the underlying type's assignment operator.

Reviewed By: @jdelong

Differential Revision: D2148093

opt proxygen with new SSL_write_iovec function

Summary: this taks advantage of the SSL_write_iovec function to improve CPU.  According our testing, it saves 10+% CPU.

Reviewed By: @djwatson

Differential Revision: D2119223

fix for Boost >= 1.56

Summary: Folly still continue to build and work on earlier boost versions(boost < 1.56).

**boost::context::make_fcontext() change history:**
* __1.55:__    fcontext_t * make_fcontext( void * sp, std::size_t size, void(* fn)(intptr_t) );
* __1.56:__    fcontext_t make_fcontext(void* sp,std::size_t size,void(*fn)(intptr_t));

**boost doc:**
http://www.boost.org/doc/libs/1_55_0/libs/context/doc/html/context/context/boost_fcontext.html
http://www.boost.org/doc/libs/1_56_0/libs/context/doc/html/context/context/boost_fcontext.html
Closes #205
Closes #210

Reviewed By: @jwatzman

Differential Revision: D2148069

Pulled By: @sgolemon

Check for python in configure

Summary: Some OSs have python named according to a version ID
e.g. `python2.7` without a symlink from plain `python`

Use autotool's AM_PATH_PYTHON to search for a suitable interpreter
and use that to generate the *Tables.cpp files.

Closes #109

Reviewed By: @yfeldblum

Differential Revision: D2147977

Keep Makefile.am from double-installing detail/Clock.h

Summary: On non-Linux systems, the autotools-based build system conditionally appends `detail/Clock.h` to `libfollybase_la_SOURCES` – even though that file is in there statically no matter what (as per [line 46](https://github.com/facebook/folly/blob/master/folly/Makefile.am#L46)), which causes the `install` command to error out trying to install the file twice, during `make install`… this patch takes out the conditional append.
Closes #201

Reviewed By: @yfeldblum

Differential Revision: D2148004

Pulled By: @sgolemon

Replace thread_local with FOLLY_TLS

Summary: OSX doesn't support C++11's `thread_local`. :-/ (yet? http://stackoverflow.com/questions/28094794/why-does-apple-clang-disallow-c11-thread-local-when-official-clang-supports/29929949#29929949)
We have `FOLLY_TLS` in `Portability.h` https://github.com/facebook/folly/blob/master/folly/Portability.h#L163-L175

So replace the usages of `thread_local` with `FOLLY_TLS`. But `__thread` is not drop-in compatible with `thread_local`, specifically the former requires global storage and needs a constexpr initializer, and a trivial destructor.

`futures/QueuedImmediateExecutor` now uses `folly::ThreadLocal` (because `std::queue` has a non-trivial destructor). It might end up in one more alloc, per thread. I also rearranged the code to clarify the fact that although there may be many `QueuedImmediateExecutor`s, they all share the same queue per thread.

I didn't use `folly::ThreadLocal` for fibers, because I thought it might be too expensive. But now I'm not so sure. I had to do the "check for default and then initialize" thing because of the requirement for constexpr initialization for `__thread` (and therefore `FOLLY_TLS`).

Reviewed By: @jsedgwick

Differential Revision: D2140369

disable ThreadExecutor in FutureTest.cpp, on OSX

Summary: Something's broken here, will track fixing in #7372389

Reviewed By: @jsedgwick

Differential Revision: D2144077

Build and run futures tests on OSX

Summary: They don't pass, but they build!

Reviewed By: @jsedgwick

Differential Revision: D2141717

Future::unit()

Summary: Discard a result but propagate an exception. cf https://www.facebook.com/groups/715931878455430/permalink/879624552086161/

Reviewed By: @​sammerat

Differential Revision: D2144567

refactor the interpretation of SSL errors into a function

Summary: This fucntion will be re-used for different SSL write functions in future.

Reviewed By: @djwatson

Differential Revision: D2117529

use LifoSem instead of sem_t for ManualExecutor

Summary: OSX apparently knows better than all of us plebes, and got rid of anonymous semaphores. Rather than try to work around that directly, I just switched to folly::LifoSem, which seems like a not-terrible idea anyway.

Reviewed By: @jsedgwick

Differential Revision: D2143566

folly::via(Executor*, Func)

Summary: ((not yet) more performant) sugar for `via(&x).then(func)`

Reviewed By: @​hannesr

Differential Revision: D2131246

Make IOBuf copyable

Summary: Give IOBuf a copy constructor, which clones the whole chain. (IOBufs have
shared pointer semantics). You could argue for cloning one single IOBuf,
but cloning the whole chain has the nice side effect of making Thrift
structures with IOBufs in them copyable, so there's that.

Reviewed By: @djwatson

Differential Revision: D2127209

RequestEventBaseCache -> IOObjectCache

Summary: Next step towards killing RequestEventBase hackery.
Use EBs from global IO executor instead

Reviewed By: @fugalh

Differential Revision: D2123142

wangle::getEventBase()

Summary: this is going to be a really common pattern, so I'm providing a shortcut

Reviewed By: @fugalh

Differential Revision: D2146008

optimize makeFuture and Future<T>::Future()

Summary: No reason to go through the whole Promise rigamarole. Add an appropriate Core ctor and use that to make a completed Future with just the core alloc

Note the big win in the `constantFuture` benchmark.

```
Before:
============================================================================
folly/futures/test/Benchmark.cpp                relative  time/iter  iters/s
============================================================================
constantFuture                                             120.50ns    8.30M
promiseAndFuture                                  91.99%   130.98ns    7.63M
withThen                                          28.17%   427.77ns    2.34M
----------------------------------------------------------------------------
oneThen                                                    430.48ns    2.32M
twoThens                                          58.03%   741.86ns    1.35M
fourThens                                         31.85%     1.35us  739.97K
hundredThens                                       1.61%    26.80us   37.32K
----------------------------------------------------------------------------
no_contention                                                4.58ms   218.48
contention                                        83.70%     5.47ms   182.86
----------------------------------------------------------------------------
throwAndCatch                                                8.09us  123.55K
throwAndCatchWrapped                              94.43%     8.57us  116.67K
throwWrappedAndCatch                             154.69%     5.23us  191.12K
throwWrappedAndCatchWrapped                      614.06%     1.32us  758.70K
----------------------------------------------------------------------------
throwAndCatchContended                                     967.54ms     1.03
throwAndCatchWrappedContended                    103.48%   935.04ms     1.07
throwWrappedAndCatchContended                    148.24%   652.70ms     1.53
throwWrappedAndCatchWrappedContended            14313.28%     6.76ms   147.94
============================================================================

After:
============================================================================
folly/futures/test/Benchmark.cpp                relative  time/iter  iters/s
============================================================================
constantFuture                                              69.11ns   14.47M
promiseAndFuture                                  55.12%   125.37ns    7.98M
withThen                                          16.49%   419.18ns    2.39M
----------------------------------------------------------------------------
oneThen                                                    370.39ns    2.70M
twoThens                                          55.11%   672.05ns    1.49M
fourThens                                         29.00%     1.28us  782.89K
hundredThens                                       1.23%    30.22us   33.09K
----------------------------------------------------------------------------
no_contention                                                4.56ms   219.46
contention                                        82.82%     5.50ms   181.77
----------------------------------------------------------------------------
throwAndCatch                                                8.30us  120.42K
throwAndCatchWrapped                              96.40%     8.61us  116.08K
throwWrappedAndCatch                             162.66%     5.11us  195.89K
throwWrappedAndCatchWrapped                      680.39%     1.22us  819.36K
----------------------------------------------------------------------------
throwAndCatchContended                                     979.17ms     1.02
throwAndCatchWrappedContended                    103.09%   949.84ms     1.05
throwWrappedAndCatchContended                    153.55%   637.71ms     1.57
throwWrappedAndCatchWrappedContended            10468.47%     9.35ms   106.91
============================================================================
```

Reviewed By: @fugalh, @​hannesr

Differential Revision: D2144664

Fix libc++ use

Summary: Use of std::max from libc++ resulted in error.
std::max found type of its arguments diffrent
whereas it expected them to be same.
This diff fix the error.
Closes #223

Reviewed By: @yfeldblum

Differential Revision: D2144639

Pulled By: @sgolemon

Fix capitalization error in README.md

Summary: Closes #211

Reviewed By: @Gownta, @lbrandy

Differential Revision: D2144702

Pulled By: @sgolemon

Fixing typos in README.md

Summary: Closes #202

Reviewed By: @paulbiss

Differential Revision: D2144850

Pulled By: @sgolemon

Update FBVector.md

Summary: Minor typo when referencing `std::allocator`
Closes #84

Reviewed By: @yfeldblum

Differential Revision: D2144830

Pulled By: @sgolemon

Update github.com/floitsch/double-conversion to new location

Summary: Closes #212

Reviewed By: @JoelMarcey, @paulbiss

Differential Revision: D2144749

Pulled By: @sgolemon

fix Baton.h typo

Summary: checked the sense
Closes #224

Reviewed By: @paulbiss

Differential Revision: D2144508

Pulled By: @sgolemon

(Wangle) Re-add race test

Summary: I figured this test would be useless since it tests a check added before
everything was converted to FSM. But since it appears to fail on Mac OS
X, it might be useful to have after all.

Reviewed By: @fugalh

Differential Revision: D2143500

Bump version to 45:0

fix typo in SharedPromise comment

Summary: ^

Test Plan: OK

Reviewed By: yfeldblum@fb.com

Subscribers: folly-diffs@, jsedgwick, yfeldblum, chalfant

FB internal diff: D2140212

Signature: t1:2140212:1433877717:86b7bf372091b455cdb25a377451e1ed4e21f50d