Summary:
The purpose of this reimplementation of `exception_wrapper` is threefold:

- Make `exception_wrapper` smaller. It goes from 48 bytes to 24.
- Give it `noexcept` ~~copy and~~ move
- Store small exception objects in an internal buffer; i.e., with zero allocations.

The ultimate goal is to change `folly::Try<T>` to a thin wrapper over `folly::Expected<T, exception_wrapper>`. (Currently, it stores the `exception_wrapper` on the heap.)

As part of this redesign, I:

- Remove `exception_wrapper::getCopied`. The user shouldn't care how the `exception_wrapper` stores the exception.
- Remove `exception_wrapper::operator==`. It was only used in 2 places in test code. The existing semantics (return true IFF two `exception_wrapper`s point to the //same// exception object) prevented the small-object optimization.
- Add new `handle()` API that behaves like cascading `catch` clauses. For instance:
```lang=c++
exception_wrapper ew = ...;
ew.handle(
    [&](const SomeException& e) { /*...*/ },
    [&](const AnotherException& e) { /*...*/ },
    [&](...) { /* catch all*/ }, // yes, lambda with ellipses works!
```
- Add a `type()` member for accessing the `typeid` of the wrapped exception, if it's known or can be determined with a `catch(std::exception&)`.

This table shows the percent improvement for the exception_wrapper_benchmark test:

| Test  | Percent improvement (gcc-5)  | Percent improvement (gcc-4)
| -----  | -----  | -----
| exception_wrapper_create_and_test  | 14.33%    | -6.50%
| exception_wrapper_create_and_test_concurrent | 11.91% | 20.15%
| exception_wrapper_create_and_throw | -0.82% | -0.25%
| exception_wrapper_create_and_cast | 15.02% | 14.31%
| exception_wrapper_create_and_throw_concurrent | 18.37% | 8.03%
| exception_wrapper_create_and_cast_concurrent | 28.18% | -10.77%

The percent win for gcc-5 is 15% on average. The non-throwing tests show a greater win since the cost of actually throwing an exception drowns out the other improvements. (One of the reasons to use `exception_wrapper` is to not need to throw in the first place.) On gcc-4, there is roughly no change since the gcc-4 standard exceptions (`std::runtime_error`, std::logic_error`) are non-conforming since they have throwing copy operations.

Reviewed By: yfeldblum

Differential Revision: D4385822

fbshipit-source-id: 63a8316c2923b29a79f8fa446126a8c37aa32989

Summary: On Windows, the OpenSSL headers have to be included in a specific order relative to WinSock. Fixing the issues ad-hock is not a viable way to continue, so treat it as completely non-portable and require all includes of it in Folly to go through the portability header.

Reviewed By: yfeldblum

Differential Revision: D4856858

fbshipit-source-id: 56aca1fb0fe095f41a8af12488c6c2080344603d

Summary:
It doesn't exist on OSX or Windows, so implement it.

Closes https://github.com/facebook/folly/issues/567

Reviewed By: yfeldblum

Differential Revision: D4783463

fbshipit-source-id: 0a2586aced7123b797a8e55a3e86124b449634e4

Summary: TSAN has a limitation for the number of locks held concurrently - https://github.com/llvm-mirror/compiler-rt/blob/master/lib/sanitizer_common/sanitizer_deadlock_detector.h#L126, so we have to work around that.

Reviewed By: yfeldblum

Differential Revision: D4866477

fbshipit-source-id: 958251e97d91c1c46ef4e907de2cf189fb04f88e

Summary: facepaw

Reviewed By: yfeldblum

Differential Revision: D4856227

fbshipit-source-id: 17a73d4d630c6efe1763bbd8aff8b7a2c7721c27

Summary: This reverts commit a80aabb5a223264746ab45e3138d065bce5fe99c

Differential Revision: D4832473

fbshipit-source-id: 1a78d61f3f09f1064876a786c15601a091f4402b

Summary: Cleanup: remove superfluous std::move for return values.

Reviewed By: yfeldblum

Differential Revision: D4856421

fbshipit-source-id: bf2cb66f3b43eb8f3b183e22b0acd31e0a0c0958

Summary:
`std::max(uint64_t, size_t)` was called.
Fixes https://github.com/facebook/folly/issues/576.

Reviewed By: Orvid

Differential Revision: D4861336

fbshipit-source-id: 1b6f67b291451048ba79d638d2c1184f9245dc0c

Summary: I landed a change to Folly that used a feature I had just re-written in Folly without updating the change. This has broken everything. Whoops.

Reviewed By: yfeldblum

Differential Revision: D4861562

fbshipit-source-id: 05beadbe233d1fdf90fb4435e65b718cdec7f63e

Summary:
It was defining the same functions as OpenSSL, but it was putting them in the `folly::ssl` namespace and requiring a manual `use namespace` everywhere to actually be able to use it. Proper portability headers require no interaction to function correctly other than including them in the build.
This adjusts it so including it is all that is required to get an OpenSSL 1.1.0 compatible API.
This also re-organizes the code to significantly lower the amount of nesting in the `#if`'s, and puts it in order from oldest APIs to newest, rather than haphazard.

Reviewed By: yfeldblum

Differential Revision: D4856784

fbshipit-source-id: 7c00fdf4a3e51e37287d2b1ef294046f38a96a43

Summary:
Use RequestChannel to construct Thrift Clients.

use folly/python/futures.h to marry up thrift client rpc futures to
asyncio futures. No gil exchanges

py3 clients are async context managers now.

Reviewed By: ambv, yfeldblum

Differential Revision: D4639677

fbshipit-source-id: 6b400747507446882d3cfcb1cf7e85c3daa07a2e

Reviewed By: yfeldblum

Differential Revision: D4856138

fbshipit-source-id: 19eee4f8c4108ef168d82d5e9b1f2d65ff9b03bd

Summary: Currently clang-format cannot be run on any file using the macro because it breaks it. By putting the warning name in a string clang-format no longer breaks it.

Reviewed By: yfeldblum

Differential Revision: D4856945

fbshipit-source-id: ebd2d223dd97f66224e9e2912610057e36287dae

Summary:
[Folly] All template params for `PriorityMPMCQueue`.

Mimic the suite of template params of `MPMCQueue`.

Reviewed By: magedm

Differential Revision: D4857179

fbshipit-source-id: 3d441099c46ea1223155bd3f4cc819595814c47b

Summary: When including OpenSSL on Windows, the portability header must be included before including any OpenSSL headers.

Reviewed By: yfeldblum

Differential Revision: D4856376

fbshipit-source-id: a8e6533b2ba3c003314ae2426605031fa67be05f

Summary: MSVC doesn't allow non-static locals to be accessed within a non-capturing lambda, and some were introduced into the json code.

Reviewed By: yfeldblum

Differential Revision: D4856242

fbshipit-source-id: b2db36ca37a79a41237d39cc7e7b839a5416922f

Summary: `EliasFanoCompressedList` requires explicit freeing.

Reviewed By: lbrandy, philippv, yfeldblum, luciang

Differential Revision: D4855200

fbshipit-source-id: ccee44b6371ae743ef15a72af9b691d5b56e37c2

Summary: Because these `atomic<int>` are referenced in the destructor of the `ReadMostlyMainPtr`, they must be declared before it, otherwise they are destroyed before it i.

Reviewed By: yfeldblum

Differential Revision: D4854964

fbshipit-source-id: 625a8f890bba166b682ca13558f8bcde86edcc75

Summary: This test actually stores references to `sum` in objects it puts into the `EvictingCacheMap`. Those references get accessed in the destructor of the objects, which is the destructor of the `EvictingCacheMap`. That means the `sum` variable must outlive (and be declared -before-) the `EvictingCacheMap` it's testing.

Reviewed By: yfeldblum, meyering

Differential Revision: D4854619

fbshipit-source-id: b0a3109278f48d10b4cd0c52a12cb2064f4a00c5

Summary:
D4406876 replaced EVP_MD_CTX and HMAC_CTX on the stack with heap-allocated
versions. We omitted the _cleanup functions thinking those didn't actually free
anything, but turns out HMAC_CTX_cleanup internally calls EVP_MD_CTX_cleanup
which OPENSSL_frees a bunch of stuff.

Reviewed By: yfeldblum

Differential Revision: D4850388

fbshipit-source-id: 4ef1413a4105f3638140e4d12aeae64afe43f099

Summary: Make sure that the last use of `s6` is sequenced before it is moved-from.

Reviewed By: nbronson

Differential Revision: D4850480

fbshipit-source-id: 5272c14475ae2c62bc613cfd54f5df482b19d3dc

Summary: The problem with catching the exception here is stack information is lost.  Just let it std::terminate if it throws

Reviewed By: ikobzar

Differential Revision: D4831909

fbshipit-source-id: 42139bd7caee0fedff13328d52fa3be1c517e730

Summary: Improve error message and change DFATAL to FATAL.

Reviewed By: yfeldblum, meyering

Differential Revision: D4837840

fbshipit-source-id: 54ae53c9356fc2e85266b037996aa7b2bae3d4e4

Summary:
Benchmark each type with its native key type and with its non-native key type.
This allows you to make a more-informed decision about which to use based on
the types you have available at insertion/lookup time.

Reviewed By: yfeldblum

Differential Revision: D4826527

fbshipit-source-id: ee4ef5255d2bdd955e9deb30dc4c28be183cee07

IndexedMemPool: Fix race condition on size_ that can cause the destructor to access nonexistent slots

Summary:
Contention on allocation when there is exactly one slot remaining can cause size_ to exceed actualCapacity_.
Without taking the min of size_ and actualCapacity_ the destructor may try to destroy out-of-bound slots.

Added a test to test/IndexedMemPoolTest.cpp that failed before the fix and passes after the fix.

Reviewed By: nbronson

Differential Revision: D4837251

fbshipit-source-id: a887487727f17eaf2ba66345f40fc91d2fe3bc00

Summary: There's a comment in that code that states that it *it* noexcept, and that is common for most folly async io callbacks.

Reviewed By: yfeldblum

Differential Revision: D4831800

fbshipit-source-id: 78894ad72504b9dfe540c14b8d7bbb29247aaf87

Summary:
Add trimAtMost start and trimAtMost end.
These are useful functions to have if you
don't care about trimming an exact amount.

Reviewed By: yfeldblum

Differential Revision: D4658087

fbshipit-source-id: f7dd62c0f4837503e59cdec75fdad433be20306c

Summary:
Implementing `clearenv()` correctly on multiple OS's without relying on underlying implementation details is significantly more complicated, and this is preventing being able to build on OSX.
This function isn't actually used anywhere currently.

Reviewed By: yfeldblum

Differential Revision: D4832473

fbshipit-source-id: a80aabb5a223264746ab45e3138d065bce5fe99c

Summary: fixing D4825412

Reviewed By: lbrandy

Differential Revision: D4826815

fbshipit-source-id: 94691ff293dad53b16e7a2f139c1df490a61e565

Summary: GMock can't mock class methods that are not virtual. This way classes relying on the non-virtual methods of AsyncSocket can't be efficiently tested using gtest/gmock.

Reviewed By: yfeldblum

Differential Revision: D4806838

fbshipit-source-id: fde852b75f7ac1d468c177e317c516cb0dc333b5

Summary:
We recently removed declarations of Function constructors and
assignment operators that took non-const Function references. They
were necessary at the time to make sure that the templated
constructor that can take any invokable object did not get
selected for copying Functions from non-const lvalues. This,
however, is now provided by some std::enable_if construct.

Reviewed By: ericniebler

Differential Revision: D4818736

fbshipit-source-id: 08197721beef009f6ae482b576df78ec6999d132

Summary:
More work to get wangle compiling. wangle/facebook/http pulls in
proxygen libs and that's another pain altogether, so this only makes the rest of
wangle build with 1.1.0 and BoringSSL

Depends on D4406876

Reviewed By: ngoyal

Differential Revision: D4767060

fbshipit-source-id: bd6bc6959d04028c84360e434f6bbdb2cde2faac

Summary: Add more layers to support compiling with OpenSSL 1.1.0

Reviewed By: yfeldblum

Differential Revision: D4406876

fbshipit-source-id: 8eff7e4f8e096605fc9e1093ef533b5afe0ee539

Summary: This is same as D4249032, but for now this is only enabled in dbg and dev builds. I'm planning to bump this to FATAL later, once we fix know problematic main()s.

Reviewed By: lbrandy, yfeldblum

Differential Revision: D4821763

fbshipit-source-id: 5f7930f8cbcb10275d23a89848f1ec8ee34a8020

Summary:
The use of generic lambdas caused compiler errors with gcc 4.8.2.
Fixes https://github.com/facebook/folly/issues/569.

Reviewed By: Orvid, yfeldblum

Differential Revision: D4821115

fbshipit-source-id: 8372ee7695a3d0a1df0d033623618a923c261737

Summary:
The priority queue in the manual executor implementation is backwards. This means that scheduled things run in reverse order, and a later thing will block an earlier thing if you advance to a timestamp in between the two.

This diff fixes the problem and adds tests to confirm the fix. These tests fail on the old implementation.

Reviewed By: yfeldblum

Differential Revision: D4739101

fbshipit-source-id: 6e429828460df5b3c656580568a9ae1eb4009527

Summary: Macros are not the best solution anymore.

Reviewed By: yfeldblum

Differential Revision: D4270626

fbshipit-source-id: 8acbd5b778d4effcfb587655b4397737bef0d379

Remove/make private the default ***Holder constructor to allow compile time detection of ***Holder(mutexPtr_) constructs

Summary: Avoid unintended C++ stuff - this is not the same as the "fleeting rvalue" - this change might break the build but I will fix it

Reviewed By: yfeldblum

Differential Revision: D4814104

fbshipit-source-id: 058a0eac44893c573062fcf5665d4fd022ee64a0

Summary:
A (almost) lock-free atomic_shared_ptr, matching the proposed concurrency TS interface.

See notes at top of file

Reviewed By: davidtgoldblatt

Differential Revision: D4716098

fbshipit-source-id: b9ca2443ba9e227ebb6f40807128073c6e14222a

Summary:
`escapeString` is very slow even when there's very little to nothing to escape. This diff adds a fast path to copy sequences of bytes that don't need escaping.
It also optimizes appending escape sequences: `string::push_back` is slow because it has to do a capacity check for every character.

Before:
```
  ============================================================================
  folly/test/JsonOtherTest.cpp                    relative  time/iter  iters/s
  ============================================================================
  jsonSerialize                                              818.55ns    1.22M
  jsonSerializeWithNonAsciiEncoding                            1.35us  738.06K
  jsonSerializeWithUtf8Validation                              1.42us  705.60K
  jsonSerializeAsciiWithUtf8Validation                         3.27us  306.06K
  parseSmallStringWithUtf                                      1.91us  522.38K
  parseNormalString                                            1.51us  660.27K
  parseBigString                                             384.44ns    2.60M
  toJson                                                     480.54ns    2.08M
  ============================================================================
```

After:
```
  ============================================================================
  folly/test/JsonOtherTest.cpp                    relative  time/iter  iters/s
  ============================================================================
  jsonSerialize                                              781.69ns    1.28M
  jsonSerializeWithNonAsciiEncoding                          847.68ns    1.18M
  jsonSerializeWithUtf8Validation                            928.68ns    1.08M
  jsonSerializeAsciiWithUtf8Validation                       199.85ns    5.00M
  parseSmallStringWithUtf                                      1.93us  518.39K
  parseNormalString                                            1.45us  689.11K
  parseBigString                                             378.66ns    2.64M
  toJson                                                     446.38ns    2.24M
  ============================================================================
```

All string escaping benchmarks are slightly faster, and ASCII-only with no escapes is 8x faster.

Reviewed By: luciang, evilmucedin, yfeldblum

Differential Revision: D4793233

fbshipit-source-id: c40d07708bd787799c8c00f9f23a417b862ee9ae