Summary: Add `count()` and `swap()` methods. Ensure that `operator==` works.

Reviewed By: yfeldblum

Differential Revision: D5169393

fbshipit-source-id: a8025f6fdf251e38b0d2f27733d18967a55c6a15

Summary: We are fully on C++14 now, so these warnings should never be firing.

Reviewed By: yfeldblum

Differential Revision: D5179124

fbshipit-source-id: 31c6ddbce5c45b60fe73990f49d65ac95d17fe87

Summary: Do this by moving the two helpers that need to refer to them into `folly/futures/helpers.h`.

Reviewed By: yfeldblum

Differential Revision: D5179109

fbshipit-source-id: bdb319ff3432d3629a955c1390dc8bf6f27f4ce6

Summary: It's deprecated, so use the non-deprecated form instead.

Reviewed By: yfeldblum

Differential Revision: D5179133

fbshipit-source-id: 91440bc3768ee68d2aada2299fbfbcdd852f946c

Summary:
[Folly] Apply `clang-format` to `folly/gen/` (partial: namespace).

With some manual rearrangement in the places where `clang-format` does awkward things, with the result that clang-format over `folly/gen/` becomes a no-op.

Reviewed By: Orvid

Differential Revision: D5177428

fbshipit-source-id: 17f51d00454a7be7f29dcf1a2ff3d0eaf1de72ab

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

With some manual rearrangement in the places where `clang-format` does awkward things, with the result that `clang-format` over `folly/portability/` becomes a no-op.

Reviewed By: igorsugak

Differential Revision: D5170107

fbshipit-source-id: ceadd96740b4877cbae947846f0e738e6aaf5ed1

Summary: Using extent_hooks mallctl to update hooks.

Reviewed By: jasone

Differential Revision: D5174623

fbshipit-source-id: 9313ee9ae55c85d973736077727e54a5825f4c3d

Hazard pointers: Optimize memory order, add bulk reclamation control, add stats, add implementation switches, add benchmarks.

Summary: Make the implementation partially performant by optimizing memory order and using asymmetric memory barrier for full fences. Also added more control for bulk reclamation implementation, stats, and quality of implementation switches.

Reviewed By: djwatson

Differential Revision: D5129614

fbshipit-source-id: c597edf711fdc8f16f80523bd8cae42c51fbe140

Summary:
jemalloc 5.0 comes replaced chunks with extents APIs. Make the API compatible
with both jemalloc 4 and 5.

Reviewed By: yfeldblum

Differential Revision: D5170925

fbshipit-source-id: ce25723975729b0b63371f89a96842a1b2e3b3cc

Summary: It is nothing but a file with the license header in it and has been since it was introduced nearly 4 years ago.

Reviewed By: yfeldblum

Differential Revision: D5163176

fbshipit-source-id: f510411cbb3d9d4c90d68c9b8d1f04d9f97fcb89

Reviewed By: yfeldblum

Differential Revision: D5105818

fbshipit-source-id: e3926a0c70a68855e0180bdd44cb0ec76e66bb94

Summary:
Add a few keywords people search for when looking for this that won't otherwise
find this file.

Add a reference to the usage notes for Singleton which are a good description
of how you should operate SingletoThreadLocal as well.

Reviewed By: nbronson

Differential Revision: D5094598

fbshipit-source-id: 9980850805e1564e5c394af713e2fa17fe8844fe

Summary:
Test output before the fix is applied:
```
folly/experimental/Bits.h:247:59: runtime error: signed integer overflow: -2147483648 - 1 cannot be represented in type 'int'
     #0 folly/experimental/Bits.h:247 folly::Bits<...>::set(int*, unsigned long, unsigned long, int)
     #1 folly/experimental/test/BitsTest.cpp:228 std::enable_if<...>::type (anonymous namespace)::testSet<...>(unsigned char*, unsigned long, unsigned long, int)
     #2 folly/experimental/test/BitsTest.cpp:263 Bits_Boundaries_Test::TestBody()
    #17 folly/experimental/test/BitsTest.cpp:381 main
```

Reviewed By: philippv

Differential Revision: D5160789

fbshipit-source-id: 43f1926d58f1a5c019d4f8794d10a7a80a5c4749

Summary: All functions in this file are defined in `folly/fibers/FiberManager-inl.h`. There are no remaining references to this file.

Reviewed By: yfeldblum

Differential Revision: D5163160

fbshipit-source-id: 2fcb782a4de78f5c067610c876d0cf98f3b69e63

Summary:
Code may pass a callback which captures an object with a destructor which mutates through a stored reference, triggering heap-use-after-free or stack-use-after-scope.

```lang=c++
void performDataRace() {
  auto number = std::make_unique<int>(0);
  auto guard = folly::makeGuard([&number] { *number = 1; });
  folly::via(getSomeExecutor(), [guard = std::move(guard)]() mutable {}).wait();
  // data race - we may wake and destruct number before guard is destructed on the
  // executor thread, which is both stack-use-after-scope and heap-use-after-free!
}
```

We can avoid this condition by always destructing the provided functor before setting any result on the promise.

Retry at {D4982969}.

Reviewed By: andriigrynenko

Differential Revision: D5058750

fbshipit-source-id: 4d1d878b4889e5e6474941187f03de5fa84d3061

Summary:
The dirty hack I was using to link `folly_base` into `folly` doesn't work in newer versions of CMake :(
This refactors the makefile to not need to dirty hack by using an object library rule instead. It also makes the compiler version detection more generic.

Reviewed By: yfeldblum

Differential Revision: D5158919

fbshipit-source-id: cd052a5f58ed3d88c377c68cca07ca8497ca0c7a

Summary:
Callables that are passed as rvalues to makeFutureWith should be
executed as rvalues.
Generally callables that get captured by value should be executed
as rvalues, to allow passing e.g. folly::Partial objects that contain
move-only objects like unique_ptr or folly::Promise.
`collect` would move out of parameters passed as lvalues.

Reviewed By: fugalh

Differential Revision: D5120420

fbshipit-source-id: 1633c6b7e3fbb562f4d31e21d28c98b053de9912

Summary:
In mcrouter code, we would like a non-throwing alternative to `decodeVarint()`. There
are real, expected scenarios where only part of a serialized varint fits into a packet,
in which case mcrouter fails to decode the varint and throws.  In these scenarios,
throwing too many exceptions can lead to lock contention and degrade performance.

Reviewed By: yfeldblum

Differential Revision: D5153823

fbshipit-source-id: 138273af832903f0b04bee0bcacddd66b4274129

Summary:
Add `equals` interface to StringPiece (Range class). To support following case insensitive compare case:
```
folly::StringPiece a("hello");
if (a.equals("HELLO", folly::AsciiCaseInsensitive())) {
  // Do something.
}
```

Reviewed By: ot

Differential Revision: D5150495

fbshipit-source-id: 26816820f93959678f550768396f55293b5588cb

Summary:
[Folly] Fix `tryTo` to support conversion to enumerations.

`tryTo` should return `Expected<Tgt, ConversionCode>` instead of `Tgt`.

Reviewed By: yfeldblum

Differential Revision: D5144706

fbshipit-source-id: cd23f3cf75de7c5a26bc569f3cb47fff360f6e2a

Summary:
`#include` inside a namespace is disallowed when using clang modules. Here I
just unconditionally include them at top level, since they are available in all the
relevant platforms.

Reviewed By: yfeldblum, Orvid

Differential Revision: D5140355

fbshipit-source-id: bb87225c1d8f4ac64b90a7aff5f912c13e150e3a

Summary:
allow-large-files
Moving DestructorCheck from proxygen library to folly.

Reviewed By: djwatson

Differential Revision: D5110897

fbshipit-source-id: 02a6cf6336000e8c36484e75d2da820588baf2df

Summary: This has always been the design rule for what belongs in `folly/portability/`, but was never written down anywhere except in my head, so put it somewhere people can actually find it so I can free that space in my head for other things.

Reviewed By: yfeldblum

Differential Revision: D5140587

fbshipit-source-id: 1f09c17b7ccfff780e1825670a7ffaa75cd1b1d5

Summary:
In contrast to Container::insert(), for any STL container class, Container::emplace() does not have an overload that takes a Container::iterator as its first parameter. (The reason is to prevent ambiguity with respect to target class constructor parameters.) Instead, container classes have a separate emplace_hint() function.
Because of this separation, folly::emplace_iterator would fail to perform hinted emplacement in constructs where std::insert_iterator would perform hinted insertion.
This diff adds a new class, folly::hint_emplace_iterator(), and corresponding convenience function, folly::hint_emplacer(), which calls Container::emplace_hint() rather than Container::emplace().
It would have been trivial to copy&paste the existing folly::emplace_iterator class and simply replace the emplace() call with emplace_hint(), but I did not like the large amount of code repetition. So I decided to do some refactoring and move the emplace()/emplace_hint()/emplace_front()/emplace_back() calls into separate trait classes, and replace emplace_iterator()/hint_emplace_iterator()/front_emplace_iterator()/back_emplace_iterator() with suitable type aliases.

Reviewed By: yfeldblum

Differential Revision: D5097860

fbshipit-source-id: c0b733131a0d0d21fc0a8b08ad655142c6a41c19

Summary:
We were hitting a bug in CMake's Ninja generator that was causing it to incorrectly attempt to escape the closing quote on `_HAS_AUTO_PTR_ETC=1`, so remove the quotes, as they aren't actually needed.
This also makes a few quality-of-life changes to make building Folly with Ninja slightly easier.

Closes: https://github.com/facebook/folly/issues/604

Reviewed By: yfeldblum

Differential Revision: D5134585

fbshipit-source-id: 3816e53774f7963b9b4fd8ddf68b83ff7afdefe1

Summary:
Clearly someone noticed this was an issue before and fixed the other 2 overloads, but never fixed these :(

Specifically, ARM has unsigned chars, so this would be producing the wrong values there.

Reviewed By: yfeldblum, mzlee

Differential Revision: D5122992

fbshipit-source-id: eb71dea82c187c09c2c4496f1f7c99bd01db6dd0

Summary: `[[nodiscard]]` is the future. Let's start now.

Reviewed By: yfeldblum

Differential Revision: D5108297

fbshipit-source-id: c98f44af9e282616af92f9171516b6ea18e68c6d

Summary:
* Add streaming interface to the `ZstdCodec`
* Implement `ZstdCodec::doCompress()` and `ZstdCodec::doUncompress()` using the streaming interface.
  [fbgs CodecType::ZSTD](https://fburl.com/pr8chg64) and check that no caller requires thread-safety.

Reviewed By: yfeldblum

Differential Revision: D5026558

fbshipit-source-id: 61faa25c71f5aef06ca2d7e0700f43214353c650

Summary:
Adds a C-style streaming API to `folly/io/Compression.h`, with a zlib-esque interface.
Stacked diffs will add streaming support to zstd, zlib, gzip, lzma, lz4_frame, and automatic codecs.
This interface is targeting advanced users who are building higher level interfaces.
They can use this as a common base so they don't have to reimplement the same code for every codec.

Reviewed By: yfeldblum

Differential Revision: D5026332

fbshipit-source-id: e3abf1767b493c2fef153b895858a3a81b67d989

Summary:
This is generated by applying clang-tidy -checks=modernize-use-override to all .cpp files under folly.
It enforces the use of the keywords virtual, override and final in a way compliant to the style guide.

Reviewed By: yfeldblum

Differential Revision: D5108973

fbshipit-source-id: 61c55aa372feebe3b3be12a2705a04879aae57a4

Summary:
This class serves a similar use case to `ReadMostlySharedPtr`, but with two differences:

- It returns actual `shared_ptr`s, so it can be used as a drop-in replacement.
- Its memory utilization is constant, independent of the number of threads that use it.

Also, the code is much simpler. On the other hand, it is about 4x slower (but it still scales linearly in the number of concurrent threads acquiring the reference).

Reviewed By: djwatson

Differential Revision: D5104730

fbshipit-source-id: 8c18b635e0390394b06417b6df8b790e4bd2d90d

Summary:
`std::optional` allows heterogeneous comparisons, so `folly::Optional` should as well.
This allows numerical comparisons between different types, like `size_t` and `uint64_t`.

Fixes https://github.com/facebook/folly/issues/602.

Reviewed By: AsyncDBConnMarkedDownDBException

Differential Revision: D5110651

fbshipit-source-id: 34f3368283953033fbb2423ab30b04e38b5b7974

Summary:
[Folly] RFC: Embed `exception_wrapper` directly into `Try`.

Rather than storing it elsewhere on the heap. With `exception_wrapper` at 24 bytes on x64, it may now be small enough. However, it will expand the size of `Try<T>` for `sizeof(T) <= 16`, giving `Try` a new minimum size of 32 bytes on x64 instead of 16.

Reviewed By: ericniebler

Differential Revision: D5051436

fbshipit-source-id: 10d59686d64382c88d54340c97567eafb3e2f682

Summary: [Folly] Fix some old license headers.

Reviewed By: meyering

Differential Revision: D5110463

fbshipit-source-id: c7bb57194e0d33fbe1c6ddaa7d94437833b0cb0d

Add FOLLY_NODISCARD for [[nodiscard]] attribute when it exists, FOLLY_WARN_UNUSED_RESULT uses FOLLY_NODISCARD.

Summary: The `nodiscard` attribute was added to standard C++ in C++17. Prefer the standard formulation when it is available; otherwise, use `__attribute__((__warn_unused_result__))` on compilers that support the GNU extensions, and `_Check_return_` on MSVC. The old `FOLLY_WARN_UNUSED_RESULT` is now expands to `FOLLY_NODISCARD`.

Reviewed By: yfeldblum

Differential Revision: D5105137

fbshipit-source-id: 9aa22e81cd9f0b89f9343433aeae3ba365227ccb

Summary: This silences a few warnings under MSVC, and gets Folly closer to being able to compile with `-Wconversion` enabled.

Reviewed By: yfeldblum

Differential Revision: D5100686

fbshipit-source-id: e5e04c7aa143597e151a56a4d1f90dda26d0033b

Summary: Because just having a linter enforce it isn't good enough to catch everything.

Reviewed By: yfeldblum

Differential Revision: D5101828

fbshipit-source-id: a1bc482b37139a1eddeb93bc298596af950aa87d

Summary:
This makes it easier to consume Folly from a non-cmake project.
Note that this also requires making libevent, which was previously categorized as a semi-portable header into a non-portable header, meaning it can't be referenced directly. (libevent includes `Windows.h` in one of its headers -_-....)

Reviewed By: yfeldblum

Differential Revision: D5106051

fbshipit-source-id: 5ce2d4188c9036d6ab206af3036c8fd4b09516a4

Summary: To take advantage of read locks.

Reviewed By: siyengar

Differential Revision: D5106090

fbshipit-source-id: a32afd698e9204196aa3d23f21a7d41803b2eb66

Summary:
[Folly] Refactor `folly/gen/test/StringTest.cpp`.

Prefer to compare whole values once per test case, rather than sequentially comparing each part in turn.

Reviewed By: andrewjcg

Differential Revision: D5101467

fbshipit-source-id: 3d19d32bc6a5ecc5863bea76c4292935c775fe75