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

Reviewed By: @fugalh

Differential Revision: D2159075

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

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

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

Summary: Instead of the one-off Nothing struct

Reviewed By: @yfeldblum

Differential Revision: D2158621

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

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

Summary: Fix leaks in unit tests

Reviewed By: @djwatson

Differential Revision: D2153681

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

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

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

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

Reviewed By: @Invalid auth token., @afrind

Differential Revision: D2151003

Summary: This reverts commit 0968dcc2f0e02998fa53007853e0c0aad0a423b7.

Reverts D2151582

Reviewed By: @​iainb

Differential Revision: D2153840

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

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

Reviewed By: @yfeldblum

Differential Revision: D2152893

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

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

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

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

Summary: To be able to use fiber lock in thrift

Reviewed By: @brianwatling, @yfeldblum

Differential Revision: D2149936

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

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

Reviewed By: @brianwatling

Differential Revision: D2151318

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

Summary: As in title

Reviewed By: @djwatson

Differential Revision: D2151092

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

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

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

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

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

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

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

Reviewed By: @jsedgwick

Differential Revision: D2144077

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

Reviewed By: @jsedgwick

Differential Revision: D2141717

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

Reviewed By: @​sammerat

Differential Revision: D2144567

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

Reviewed By: @djwatson

Differential Revision: D2117529

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

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

Reviewed By: @​hannesr

Differential Revision: D2131246

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

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

Reviewed By: @fugalh

Differential Revision: D2123142