Summary:
Adjust `CxxAllocatorAdaptor` such that it becomes default constructible.  This makes `SysArenaAllocator` default constructible too, which makes it much easier to use.

A default-constructed `SysArenaAllocator` is not useful at all.  Any attempt to allocate just throws `std::bad_alloc`.  But it makes it possible to at least compile code like this:

```
using MyAlloc = SysArenaAllocator<char>;
struct Foo {
   Foo() = default;  // BOOM
   Foo(MyAlloc &a) : v(a) {};
   vector<int, MyAlloc> v;
}
```

Reviewed By: yfeldblum

Differential Revision: D21967640

fbshipit-source-id: 5b74c6db14d75364b374cad71d0069b17769e5d6

Differential Revision:
D22027490

Original commit changeset: 964d9fa19ca9

fbshipit-source-id: 2c92ea47c64450cb031be4a6df3c3be4901500b7

Summary:
On Linux platforms the folly::futexWait() functions are implemented using the
futex() syscall, which requires passing a timeout parameter that specifies a
an expiry time either in CLOCK_REALTIME or CLOCK_MONOTONIC.

The futexWait() implementation currently assumes that the std::chrono::system_clock
and std::chrono::steady_clock implementations are thin wrappers over these
clock types and that we can directly convert the .time_since_epoch() values to
a timespec value that we can pass to the futex() syscall.

The Futex.clock_source test is checking this assumption about the implementation
of the std::chrono clocks.

Unfortunately, this assumption does not hold on recent libc++ implementations for
Apple platforms, which now uses the CLOCK_UPTIME_RAW clock for the
std::chrono::steady_clock implementation and so this test was failing on the
Mac platforms.

However, since we aren't actually relying on this assumption on platforms other than
Linux, we can just disable this test for non-Linux platforms.

Reviewed By: yfeldblum

Differential Revision: D22075639

fbshipit-source-id: 229995ba7c01b52d1949ef5942774920876d0994

Summary: Thread fences are not supported by TSAN

Reviewed By: yfeldblum

Differential Revision: D22056483

fbshipit-source-id: dfe5b462656605f2e659302125e248b287037629

Summary:
Original commit changeset: 25d4049019e4

Base diff broke fboss build (using fbcode_builder) with the following error:

/tmp/fbcode_builder_getdeps-ZrootZfboss2.gitZbuildZfbcode_builder-root/installed/folly/include/folly/init/Init.h:22:10: fatal error: folly/experimental/symbolizer/SymbolizerMode.h: No such file or directory
 #include <folly/experimental/symbolizer/SymbolizerMode.h>

Revert this first to unblock fboss while I am investigating the failure.

Reviewed By: shri-khare

Differential Revision: D22077183

fbshipit-source-id: 8bafc0518df82c61922104b7d59ef5ee20fdd572

Summary: Move the tests for the async framework into the a test directory under folly/fibers/async/

Differential Revision: D22023986

fbshipit-source-id: c38aa2a63381c2aea1fd89a0cf2740ca028152c9

Summary:
[Folly] Add missing `#include <memory>` in `folly/memory/ReentrantAllocator.h`.

Closes: https://github.com/facebook/folly/pull/1379.

Reviewed By: Orvid

Differential Revision: D22062251

fbshipit-source-id: 30e2f5aa2708048c478a298cf7e12a012ba59540

Summary: Fixed the missed initialization in InitOptions.

Reviewed By: luciang

Differential Revision: D22023637

fbshipit-source-id: 25d4049019e42708c98e5b589ed4838e2870d39b

Summary: F14 class member fields are often in headers, and often the default constructor is implicit. The current implementation unconditionally instantiates `reserve()`, which has non-negligible cost. By specializing the default constructor we can avoid that in the common case.

Reviewed By: philippv, luciang

Differential Revision: D22027490

fbshipit-source-id: 964d9fa19ca92797bcb209e09959dc4706af39d4

Summary:
This diff implements a deduction guide for explicitly creating and returning Async objects in lambdas and functions with deduced return types.

This saves the user from having to specify often lengthy return types when annotating such functions.

Reviewed By: A5he

Differential Revision: D21770141

fbshipit-source-id: f80898ef6eeadee7c5a7168aaae4031e224a0935

Summary: This diff implements traits to aid in the development of templated functions accepting annotated functions.

Reviewed By: yfeldblum, A5he

Differential Revision: D21770066

fbshipit-source-id: 40ae340aeeb484c4f9769c13b5c9a92a97723801

Summary:
This diff implements `coro_wait`, an annotated helper to block on the execution of a coroutine.

The goal here is to provide an easy way to migrate from fibers to coroutines.

Reviewed By: A5he

Differential Revision: D21978610

fbshipit-source-id: d59a222978d9db2963656312e71c7dcb2b9a11e9

Summary:
This diff adds `future_wait`, an annotated helper to run blocking `get` operations on futures.

`future_wait` will help annotate functions (and their caller stack) that block on futures.

For semifutures, deferred work is performed on fiber-main context, so there is no concern of bleeding fibers.

Reviewed By: yfeldblum

Differential Revision: D21965552

fbshipit-source-id: 79941c3b73c67d63d83dcdc778c62a0fc9051de3

Summary:
I think LZ4 was disabled accidentally in our rocksdb getdeps build in
D21319896. Enable it again on macOS and Linux, because otherwise this
breaks people with EdenFS mounts containing LZ4-compressed proxy
hashes.

Reviewed By: xavierd

Differential Revision: D21990356

fbshipit-source-id: b9166c2992ae51f09de3fa9a4f114143aa008f43

Summary:
Adds a helper utility called 'tag_invoke' for defining CPOs that dispatch to a call to an overload of the ADL-name 'tag_invoke()' that takes the CPO as the first argument instead of to a CPO-specific ADL-name.

This makes it possible to build generic adapters, such as type-erasing adapters, that can forward through calls to all CPOs through to an underlying object.

Adds FOLLY_DECLVAL(T) helper macro used in the implementation of some of the traits.

Reviewed By: yfeldblum

Differential Revision: D17867173

fbshipit-source-id: fadae6ec97498008a5238036b7310a1e0ae119a2

Summary:
folly::Hash<Range<T>> uses SpookyHashV2::Hash64 (for integral
T). On 32-bit platforms we need an explicit cast to avoid a narrowing
warning when converting this to size_t.

(Note: this ignores all push blocking failures!)

Reviewed By: shixiao

Differential Revision: D21491467

fbshipit-source-id: 1cbd05553c61b8dccb664ec4478cfb0b049dc5b5

Differential Revision:
D21918702

Original commit changeset: 3213e9536147

fbshipit-source-id: 4e9394b2026f0d6d74e668c7c72b3612a42770ea

Summary: This header is widely included (via `Future.h`) and instantiations of `UnboundedQueue`'s methods are expensive, so outline them (note that the template methods will only be instantiated if used, so that's fine).

Reviewed By: philippv

Differential Revision: D22014083

fbshipit-source-id: b6a71c38c142917e9e0d86fbb64a88462382952a

Summary: This would allow us have better stack trace with inline functions in signal handler output.

Reviewed By: luciang

Differential Revision: D21918702

fbshipit-source-id: 3213e9536147759a4e59f5b6f68d22d941d36c7f

Summary: [Folly] Wrap `_r_debug` per platform, since the way to get it varies by platform.

Reviewed By: ot, luciang

Differential Revision: D22004737

fbshipit-source-id: 6f6a6163c9709da0a5042b807cdd88fcdf2e57eb

Summary: Thread fences are not supported by TSAN

Reviewed By: yfeldblum

Differential Revision: D21989519

fbshipit-source-id: bb657c82a64abe025e8f4c030916c0cacc3c0b81

Summary:
The `collectSemiFuture` method doesn't exist.  Use `collectAllSemiFuture` instead.
Pull Request resolved: https://github.com/facebook/folly/pull/1385

Reviewed By: yfeldblum

Differential Revision: D21991532

Pulled By: DerekTBrown

fbshipit-source-id: 4ba3378fe34b7e6bb910f7045267fdbab87ebb14

Summary:
Original commit changeset: 8eb472ce50bf

This breaks time measurement to include measuring the wait preceding handler/callback invocation.

Reviewed By: w-o-o

Differential Revision: D21986042

fbshipit-source-id: 42701b929878c3f56d736de5ca0417814c64fce1

Summary:
Debug builds can be prone to stack overflows if they are configurated to use the same stack sizes as prod builds.

This diff effectively doubles the stack size for debug builds to provide more buffer against overflows.

Reviewed By: yfeldblum

Differential Revision: D21913754

fbshipit-source-id: bd32cc4dd9c79a50be178e5d6d30804a83e60ee4

Summary: Returns the previous/next power of two that are strictly smaller/greater than the parameter.

Reviewed By: yfeldblum, Gownta

Differential Revision: D21920224

fbshipit-source-id: be919063379e5b231cc69d743128fcaeb0ea9f39

Summary: [Folly] Cut the FOR_EACH_KV macro, which may be replaced by a combination of range-for and structured bindings.

Differential Revision: D21826182

fbshipit-source-id: ce4712afd3d0d7806eb1fca8c97009da117f982e

Reviewed By: yfeldblum

Differential Revision: D21921631

fbshipit-source-id: e905d6d2a96775a8c3b328fb78c8d32897f634f6

Summary: connect will automatically bind the socket if the socket is not bound yet

Reviewed By: yangchi

Differential Revision: D21845740

fbshipit-source-id: 27a5b44476dfc0b2ae5ff2f0a6c1bd4e976eadc9

Summary: [Thrift] Dead Code: `TAsyncSocket`.

Reviewed By: vitaut

Differential Revision: D20851837

fbshipit-source-id: d4279fb1ab712f338d399220df26d56c4ab7076a

Summary:
[Folly] `EventBase::getRecentSteadyTime`, returning a recent `steady_clock::time_point` which is updated each pass through the event loop, but not for each ready event or function.

Assuming everything in the loop is truly asynchronous, this permits callers to get a reasonably accurate approximation of the current time, but for many callers to blend or amortize the cost of getting that current time.

May only be called from the running IO thread.

Differential Revision: D21866783

fbshipit-source-id: 8eb472ce50bf012616e567b29f6724c67ef8d41a

Summary: [Folly] `atomic_ref::compare_exchange_strong` and `atomic_ref::compare_exchange_weak`.

Differential Revision: D21923944

fbshipit-source-id: 55620473ea253782cc1dbb95baef38c96a9fbc70

Summary: This provides a single mechanism to mitigate deadlocks in singleton destructors.

Reviewed By: yfeldblum

Differential Revision: D21827615

fbshipit-source-id: 090bad1a91238310e7814663193711df0f4d622a

Summary: [Folly] Deduction guide for `atomic_ref`.

Reviewed By: markisaa

Differential Revision: D21923854

fbshipit-source-id: 8ad10692b95c653fc65302e6ad0118cbd615a62f

Summary:
All implementations of transports in practice were all AsyncTransportWrappers
(AsyncSocket, AsyncSSLSocket, AsyncFizzBase, etc.).

AsyncTransportWrapper was confusing. The only additional functionality that
it provided was the ability to query underlying transports, a piece of
functionality which makes just as much sense on AsyncTransport.

The simplified model:

"AsyncTransport deals with bidirectional I/O. It is both an AsyncReader, and
an AsyncWriter. It may be nested."

This diff changes AsyncTransportWrapper usages in folly to refer to
AsyncTransport, and aliases AsyncTransportWrapper for compatibility.

Reviewed By: yfeldblum

Differential Revision: D21915048

fbshipit-source-id: 741fad91b8f7c8080f942168f5513b12602cfe9a

Summary:
It was very hard to read without any code highligting.
Pull Request resolved: https://github.com/facebook/folly/pull/1364

Reviewed By: Orvid

Differential Revision: D21921822

Pulled By: yfeldblum

fbshipit-source-id: aa1bc39a5d38b055fe4370ccd4ac0b7d5e0273d4

Summary:
[Folly] Add missing `#include <sys/wait.h>` in `folly/test/RandomTest.cpp`.

Fixes https://github.com/facebook/folly/issues/1371.

Reviewed By: Orvid

Differential Revision: D21910410

fbshipit-source-id: 31a045960b2e67282fa77595dfdf840c338ef661

Summary:
[Folly] Mark `_r_debug` imports as weak imports. `_r_debug` is available in `<link.h>` but is not a portable API, so detect whether it is available at runtime and use it only if it is available.

Fixes: https://github.com/facebook/folly/issues/1373.

Reviewed By: Orvid

Differential Revision: D21911715

fbshipit-source-id: 660c0bc90d405d9a43826e7bdfc3b04480728b66

Summary: [Folly] Cut dead code: `countLoadedElfFiles()`.

Differential Revision: D21910945

fbshipit-source-id: 43ff7d118b4876e2cbd4527713c8552963810537

Summary:
[Folly] Let `ElfCache` be unbounded to permit binaries with many dynamically-linked libraries from continuously missing the cache when symbolizing.

Some applications symbolize stacktraces relatively frequently. When the build is using dynamic linking, such as might be done when developing the application or running the unit-tests, the overhead from re-loading `ElfFile` instances can appear. Address this by making the cache be unboundedly large.

This is unlikely to affect applications built using mostly-static linking, such as might be done for production builds, even when they are large applications built from many libraries, since the capacity parameter is usually much larger than the total number of dynamically loaded libraries.

Currently, no substantial work is done when initializing `ElfFile` instances. If substantial work were to be done, especially in an unoptimized build such as might be used when developing the application or running the unit-tests, and instances do not stay in cache, then that substantial work would be repeated whenever symbolizing stacktraces rather than being amortized.

Reviewed By: luciang

Differential Revision: D18819555

fbshipit-source-id: 0e75326133e901e7bd49ea3cefe9b318e6d4466f

Summary: It's possible that we still have a recurring pool resizer task scheduled after virtual event base is destroyed. This changes makes sure that we don't try to reschedule it if VirtualEventBase is already destroyed.

Reviewed By: yfeldblum

Differential Revision: D21875241

fbshipit-source-id: c4622c5d103c6291386055c153ab4aeebe7795a2