Summary:
Current `IsOneOf` implementation does unnecessary work because it instantiates all of the possible template specializations, even if type is same as the first of the tested ones. E.g.
`IsOneOf<char, char, int, float>` will instantiate:
```
IsOneOf<char, char, int, float>
IsOneOf<char, char, int>
IsOneOf<char, char>
IsOneOf<char>
```

With the proposed inheritance, compiler will stop initializing at the first match.
Closes https://github.com/facebook/folly/pull/643

Reviewed By: ericniebler

Differential Revision: D5482783

Pulled By: yfeldblum

fbshipit-source-id: 3d04c750ce72fa9b19b4d0588cccfb396a9e0715

Reviewed By: yfeldblum

Differential Revision: D5509756

fbshipit-source-id: 0b9581dafb073c5e3e5a229c032c6cf272ceb2e0

Summary:
std::ostream may be incomplete because Range.h doesn't use <ostream>,
only <iosfwd>. Changing the operator<< overloads to be templated on the char
type defers typechecking until callsites, which will avoid the potential problem.

Reviewed By: yfeldblum, ericniebler

Differential Revision: D5494648

fbshipit-source-id: e59b6fdfba6c08ec70ebb1e10c14a43307a1119f

Summary:
When attempting to output a FixedString into eg. glog or
some other ostream, it is first being implicitly converted to StringPiece
and then that is printed using the overloaded operator<<. If another
suitable implicit conversion is provided, eg. to `dynamic`, compilers
cannot choose between either one. Instead, overload operator<< directly
on FixedString to resolve the ambiguity.

Reviewed By: yfeldblum, ericniebler

Differential Revision: D5492779

fbshipit-source-id: 92d661e5471a91057d7a0d010420709c5d59232f

Summary: Older versions of libc++ do not support `std::aligned_storage_t`, switch to something more widely supported.

Differential Revision: D5506449

fbshipit-source-id: 3f5cf5dddf00bda76d4f16cfd4d8944ee5f1ba55

Summary:
[Folly] Add `FOLLY_HAS_FEATURE` and use it.

Use it in the definitions of `FOLLY_SANITIZE_ADDRESS` and `FOLLY_SANITIZE_THREAD`.

Reviewed By: meyering

Differential Revision: D5496915

fbshipit-source-id: e272137ad8ba891e64fc98444edf573115764ee2

Summary: [Folly] Cut `moveFromTry`. Not necessary, and is even longer than `std::move`.

Reviewed By: WillerZ, ericniebler

Differential Revision: D5478450

fbshipit-source-id: ecd01cb1bcd435e49268a76dd558e57ba8dd9b9e

Summary:
[Folly] Outline `throw` statements in `dynamic`.

There is no need for them to be inline - definitionally, they are always cold.

Reviewed By: WillerZ

Differential Revision: D5497457

fbshipit-source-id: 7b649c59b5b2609f838eb10e9329468d1bd1d558

Summary: It has been years since BEAST attack surfaced. The vulnerabilities have been patched and the mitigation using RC4 cipher is no longer needed. This diff removes the code relevant to mitigating BEAST years ago.

Reviewed By: anirudhvr

Differential Revision: D5409859

fbshipit-source-id: 58178e68a447f372b19491832a7be590af9402e9

Summary: Add an event base getter for AsyncUDPSocket similar to the other socket classes.

Reviewed By: knekritz

Differential Revision: D5498587

fbshipit-source-id: ac3179e03485328417ed9863f6bb790de7c691cb

Summary:
A ConcurrentHashMap with wait-free readers, as in Java's ConcurrentHashMap.

It's a pretty generic closed-addressing chaining hashtable, except find() uses two hazard pointers
to do hand-over-hand traversal of the list, so it never takes a lock.

On rehash, only the part of the chain that remains the same (i.e. is still hashed to the same bucket)
is reused, otherwise we have to allocate new nodes.

Reallocating nodes means we either have to copy the value_type, or add in an extra indirection
to access it.  Both are supported.

There's still a couple opportunities to squeeze some more perf out with optimistic loading
of nodes / cachelines, but I didn't go that far yet, it sill looks pretty good.

Reviewed By: davidtgoldblatt

Differential Revision: D5349966

fbshipit-source-id: 022e8adacd0ddd32b2a4563caa99c0c4878851d8

Summary:
Currently hazard pointers doesn't support stealing any of the pointer bits.
You can *almost* roll it yourself using try_protect, but this prevents
implementations from choosing their type of barrier.

This adds a new get_protected interface that you can use to steal bits, or
otherwise manipulate pointers as you would like.

This also adds a MWMR list based set example that uses it, that is wait-free
for readers (unlike the SWMR example, that is only lock-free).

Reviewed By: magedm

Differential Revision: D5455615

fbshipit-source-id: 53d282eda433e00b6b53cd804d4e1c32c74c2fb8

Summary: Now const-optimizer safe, and safe when the contained value overloads unary operator&

Reviewed By: yfeldblum

Differential Revision: D5480170

fbshipit-source-id: 3b53b0b6ce608857aa29d3f61eccd0b793b4cddc

Reviewed By: yfeldblum

Differential Revision: D5497522

fbshipit-source-id: bb208aeb37b5b9ce99619193d4cd2d0f3fb39178

Summary:
[Folly] Add `FOLLY_HAS_BUILTIN` and use it.

Use it in the definition of `folly::launder`. Of course, since GCC does not have `__has_builtin`, we still have to check its version.

Reviewed By: WillerZ

Differential Revision: D5496748

fbshipit-source-id: 3bd6e89424dfd2c9cb9795ee4d88f66c4294cc4c

Summary:
[Folly] Cut `throwOnFail`.

It is not necessary, and `CHECK_THROW`, its reason for existing, can be implemented without it.

It can also easily be a pessimization because there is no way to delay computation of the arguments to the exception ctor until after the check. So if there is, say, a computation using `sformat` to compute a string argument to the exception ctor, that will always be performed rather than being performed only should the check fail.

Reviewed By: Orvid

Differential Revision: D5478804

fbshipit-source-id: 71a125c126eae76c6e95ef1bd23ee883b1db39a5

Summary:
(1) small_vector.h line 1099: wrap the default return in an else statement to
avoid compiler warning of "unreachable statement".
(2) Constexpr.h: need to treat cudacc similarly to msvc.

(Note: this ignores all push blocking failures!)

Reviewed By: dzhulgakov

Differential Revision: D5387061

fbshipit-source-id: f002ab5ec00d4dcd85d86386f87a0327023afa1b

Summary: [Folly] Move `__CLANG_PREREQ` to `folly/CPortabiilty.h`.

Reviewed By: Orvid

Differential Revision: D5496372

fbshipit-source-id: 710af3d30aa8bd0e5f645beede354e3463f1bb25

Summary:
[Folly] There is no `HAVE_SHADOW_LOCAL_WARNINGS`

It is `FOLLY_HAVE_SHADOW_LOCAL_WARNINGS`.

Reviewed By: Orvid

Differential Revision: D5496247

fbshipit-source-id: 689f40180180465bdc44593059e44fb64cf3e415

Reviewed By: anirudhvr

Differential Revision: D5492790

fbshipit-source-id: 10e868976a7ea42673d5b5c906a53c6c9495a288

Summary: Closes https://github.com/facebook/folly/pull/642

Reviewed By: Orvid

Differential Revision: D5471368

Pulled By: yfeldblum

fbshipit-source-id: 3bbafd04b93828121ba829027959b6b3e0e55888

Summary:
OpenSSL 1.1.0 deprecates the callback based locking setup in favor
for platform native mutexes.

Added `OPENSSL_init_ssl` in the OpenSSL portability module for OpenSSL API < 1.1.0. This implements
the standard OpenSSL library initialization routines (taken from SSLContext::initializeOpenSSL).

Added `OPENSSL_cleanup` in the OpenSSL portability module for OpenSSL API < 1.1.0. This implements
the cleanup routine from SSLContext::cleanupOpenSSL.

Removed `SSLContext::SSLLockType`. Replaced with `folly::ssl::LockType`.

Reviewed By: mzlee, ngoyal

Differential Revision: D5404777

fbshipit-source-id: 7e5d9bf4a6683afb5560ada0a5b73cac3ff2662b

Summary:
If an exception is thrown during the construction of value in a container, then the Transformer iterator will not successfully reconstruct a cache_ object after explicitly calling its destructor (due to the exception being thrown), which results in a double-free when cache_ is destroyed as part of Transformer's destructor.

Conveniently, there exists a piece of code designed to solve just this problem: folly::Optional. Replace cache_ and valid_ with folly::Optional.

This also fixes the unnecessary requirement that container value types have default constructors, since cache_ is no longer default constructed inside of Transformer.

Reviewed By: markisaa

Differential Revision: D5472342

fbshipit-source-id: eade1f7ce260b9b3406d92af8255b5ffa4e4a51c

Summary:
An instance of `Replaceable<T>` wraps an instance of `T`.

You access the inner `T` instance with `operator*` and `operator->` (as if
it were a smart pointer).

`Replaceable<T>` adds no indirection cost and performs no allocations.

`Replaceable<T>` has the same size and alignment as `T`.

You can replace the `T` within a `Replaceable<T>` using the `emplace` method
(presuming that it is constructible and destructible without throwing
exceptions). If the destructor or constructor you're using could throw an
exception you should use `Optional<T>` instead, as it's not a logic error for
that to be empty.

Reviewed By: yfeldblum

Differential Revision: D5346528

fbshipit-source-id: c7d72e73ea04e371325327a7ff0b345315d6e5ac

Summary:
[Folly] Move the SpookyHash libraries into `folly/hash`.

And propagate the changes to `#include` lines, etc.

Reviewed By: Orvid

Differential Revision: D5477735

fbshipit-source-id: 94fe95ece05b52bde1466ab5f9fb8b53a4c59bed

Summary:
[Folly] Outline the `throw` statements in `Try`.

They are by definition cold and so we gain nothing from inlining them.

Reviewed By: Orvid

Differential Revision: D5478237

fbshipit-source-id: f413251a56ca4cbddcf3baea6679a552ae5bb19e

Summary:
Add fnv1-a 64 bit hash to Hash.h.
fnv1-a is supposed to be preferred over
fnv1.

Reviewed By: yfeldblum

Differential Revision: D5453401

fbshipit-source-id: c13f12ef11eb6745c95f3901b14ceafce90ea0ea

Summary:
This reverts commit 616b04579eb6c822023b04840b075f3ac9fbb720

bypass-lint

Differential Revision: D5455584

fbshipit-source-id: afc712fe40121232f52a5bad781350581cec6ce8

Summary:
[Folly] Move the SpookyHash libraries into `folly/hash`.

And propagate the changes to `#include` lines, etc.

Reviewed By: ot, ericniebler, Orvid

Differential Revision: D5455584

fbshipit-source-id: 616b04579eb6c822023b04840b075f3ac9fbb720

Summary: On the non sse42 path, we throw std::runtime_error, but Crc32cDetail.cpp is missing the header for it so it fails to compile on aarch64.

Reviewed By: yfeldblum

Differential Revision: D5468906

fbshipit-source-id: 2d5408621cb2b6758d3501407ed3d2a40d79f1b0

Summary: [Folly] Apply `clang-format` to `folly/experimental/symbolizer/`.

Reviewed By: Orvid

Differential Revision: D5468832

fbshipit-source-id: 94a0f82312769be0e8be724c11f97e14425ead10

Summary: [Folly] Apply `clang-format` to `folly/experimental/io/`.

Reviewed By: Orvid

Differential Revision: D5460571

fbshipit-source-id: d19aff829316dd277e65620196e12db8cad46787

Summary:
[Folly] Style tweaks to `max_align_v` calculation.

* Change ns from `folly::detail` since that can be crowded and many other folly libraries may include this header.
* Extract a 2-param `max` alias.
* Fix an incorrectly hardcoded `size_t`.

Reviewed By: WillerZ

Differential Revision: D5468758

fbshipit-source-id: 14a3f67323020a3cfce2b3b46f5f64f3e6125027

Summary: [Folly] Apply `clang-format` to `folly/tracing/`.

Reviewed By: Orvid

Differential Revision: D5460511

fbshipit-source-id: c7a7d34211044a1b76934f184a8552a96d0bad91

Summary: [Folly] Parse suffixes without switch-fallthrough in huge-pages. It is clever, but weird. We can use an immediately-executed lambda expression to make it convenient.

Reviewed By: Orvid

Differential Revision: D5467585

fbshipit-source-id: 02ddb97641db97e38e3f40388ecc522eccd436cb

Summary: [Folly] Apply `clang-format` to `folly/experimental/bser/`.

Reviewed By: Orvid

Differential Revision: D5460552

fbshipit-source-id: e103f8920eb29b7c14688f5bbb3e28129ef35e96

Summary: [Folly] Drop a remnant of gcc48 support in futures. Because gcc48 is no longer supported.

Reviewed By: Orvid, meyering

Differential Revision: D5460788

fbshipit-source-id: 86e2985a0980357641d18f59fd25b9667ec30ab0

Summary:
Fix comment for exception_wrapper's `operator bool()`.
It reads "return `true` if `*this` is not holding an exception"
but the actual behavior is to return `true` if `*this` *is* holding
an exception.

Reviewed By: yfeldblum

Differential Revision: D5456386

fbshipit-source-id: ec3a472ea441476d835881e94036a3957bb2ab32

Summary:
`folly::max_align_t` is a portable replacement for `std::max_align_t`.

`folly::max_align_v` is a `constexpr size_t` with the same value as `alignof(folly::max_align_t)`

32-bit iOS environments have `alignof(std::max_align_t) == 4`, which is not correct. This is more
correct in that I have not yet found a more-aligned basic type.

Reviewed By: yfeldblum

Differential Revision: D5442333

fbshipit-source-id: 0a93e48a730d65ef76e04f132b5976c93587b14c

Summary:
Add non null annotation to
folly to help with linters
complaining when a pointer could
be null, however it never is.

Reviewed By: yfeldblum

Differential Revision: D5453255

fbshipit-source-id: cf7ccbcc86d171ef4f6d373b6f751f709e4587b1