Summary:
`std::atomic_wait()` and `std::atomic_notify_one()` are marked as unavailable.
Not really sure what that means, but it seems to be breaking some open source
builds https://github.com/facebook/folly/issues/1527.  Explicitly qualify the
calls into those functions to try and fix the build break.

Since we cannot conditionally import either of the above (because they are
marked as unavailable), we can't rely on the standard implementations.  To
prevent ADL from kicking in when the standard-library defines these, we fully
qualify these and use `tag_invoke` for the customization points used in tests.

Reviewed By: davidtgoldblatt

Differential Revision: D26742072

fbshipit-source-id: 9f44bbfd37530f5ecffa3e03d673cfb1df953299

Summary:
Generic ascii-ification functions `to_ascii` and `to_ascii_size` for varying unsigned integer types over varying integer bases.

Has minimal dependencies. Is explicitly async-signal-safe.

Reviewed By: kennyyu

Differential Revision: D26593764

fbshipit-source-id: b1432bee8ca8eb0a5304943c4e231e201425f14a

Summary: Executors just carry on after a task they are running fails, although they try to log something marginally useful. Deduplicate the logic.

Reviewed By: aary, ot, philippv

Differential Revision: D26745058

fbshipit-source-id: 90fa558c89591b8a2d08e6820388970dee8811be

Summary:
This just fixes the include order within groups of includes, so is significantly less aggressive than the other codemod which regroups includes.

I've manually ensured that:
- groups are split when trivial.
- glog is not reordered relative to other folly headers (seems to cause down stream issues)
- portability headers are not reordered (seems to cause down stream issues)
other diffs will finish the regrouping and ordering of those groups.

Reviewed By: yfeldblum

Differential Revision: D26405757

fbshipit-source-id: 9b79a91a41a4e6ac677ed0cb7fb24dfb7c8093d2

Summary: Tag all inline-like executors, so that there's a single way to detect them in places where we don't want inline executors.

Differential Revision: D26564118

fbshipit-source-id: 1a55c03bee0a0a56328175c016d3880a86eab8b1

Summary: Folly may assume all compilers have `__has_include`. Remove the single case of testing for it before using it.

Reviewed By: simpkins

Differential Revision: D26788728

fbshipit-source-id: a11b47f6730700d81141d14c627e9d414ee6f68d

Summary: This diff is part of a series cleaning up coro::Socket

Reviewed By: yairgott

Differential Revision: D26837067

fbshipit-source-id: e7ef587a6f859a167404b3eb2c8399544aa1d092

Reviewed By: yfeldblum

Differential Revision: D26848785

fbshipit-source-id: 441aeac55f51ee8ec5e2316288f2c1f778a60dda

Summary:
Allows waiting for a range of SemiAwaitables while receiving progress incrementally.
Often requested as a repeatedly-invokable collectAll.

Uses an external AsyncScope to avoid the following sharp edge with using an internal scope (demonstrated in V1 of this diff): if the AsyncGenerator is destroyed without being fully drained we'd have to block on the scope, which can deadlock.

Reviewed By: helfman

Differential Revision: D25924855

fbshipit-source-id: 46dd7c64d58560f57a7c18e35c159beb984286a7

Summary: Mod all such cases not to pass any exception type list since such cases presumably want to catch all exceptions.

Reviewed By: ericniebler

Differential Revision: D26712856

fbshipit-source-id: 1b5de869da5701a6bec85770f11c88195d7e62d8

Summary:
D24094832 (https://github.com/facebook/folly/commit/842ecea531e8d6a90559f213be3793f7cd36781b) enabled code blocks which were currently not supported with SGX build mode, resulting in fbenclave build errs [T85891699].

Our SGX targets depend on folly and are built with a custom toolchain. Because of our dep constraints we don't support all features. We typically try to toggle certain folly features, for example: https://www.internalfb.com/intern/diffusion/FBS/browsefile/master/tools/buckconfigs/fbcode/sgx.bcfg?commit=8981fc7187d8b2484a764e9277a1efa082a13f50&lines=36

We were unable to disable these blocks of code because this macro was defined to be 1. We would typically just add the compiler flag: -DFOLLY_HAVE_SO_TIMESTAMPING=0. But doing causes redefinition.

Reviewed By: bschlinker

Differential Revision: D26765404

fbshipit-source-id: 06d800efa7f23d9235a019ed7cc8fe4cde53c91c

Reviewed By: yfeldblum, philippv, luciang

Differential Revision: D26832361

fbshipit-source-id: 9f67a0af8c3c939cbfda1bd46806849e164e5354

Summary: Since most uses just specify `std::exception` and really just want to catch everything.

Reviewed By: ericniebler

Differential Revision: D26712827

fbshipit-source-id: b33c1a311a839a50d81b9bc6c2b441908130dec6

Summary: FiberManager depends on those tasks to be run to know when it's safe to shut down (i.e. all outstanding tasks should be run).

Differential Revision: D26811875

fbshipit-source-id: 98b59ad28e25e7e47197e23ad3209349fdbfbb44

Summary: Adds `pretty_formating_indent_size` option which is used to change the indentation size when used with `pretty_formatting`

Reviewed By: yfeldblum

Differential Revision: D26793086

fbshipit-source-id: 53efea33d7daa5c8f8840fc7f087d2d976ed3eda

Summary:
Revise `folly::demangle` and its test suite.

As a few items:
* Minimize preprocessor conditional compilation.
* Make the tests work for all combinations.

Differential Revision: D26551208

fbshipit-source-id: 422f6f96632c4dfc3f2e51f7b3ae8855cdb3ab30

Summary:
If we have `PATH_MAX` we can probably have `NAME_MAX` as well.

It should be exact equivalent of `NAME_MAX` on Windows:
https://docs.microsoft.com/en-us/cpp/c-runtime-library/path-field-limits?view=msvc-160

Reviewed By: Orvid

Differential Revision: D26784071

fbshipit-source-id: 1e28d5de4358efded182db85f0382939c96a4dce

Summary:
Update the check in `folly/Portability.h` to handle more recent versions of
MSVC that do support `__has_include`.  The code on the `__has_include` code
path was checking the value of `__cplusplus` rather than `_MSVC_LANG`.
Microsoft only defines `__cplusplus` correctly when the compiler is invoked
with the `/Zc:__cplusplus` flag.

This updates the code to use the `FOLLY_CPLUSPLUS` macro instead.

Reviewed By: yfeldblum

Differential Revision: D26769080

fbshipit-source-id: e40cfaef967b13d2fe1be2b40a109cb0ed39515a

Summary: Workaround for: "folly/Range.h:252:9: error: field 'b_' will be initialized after field 'e_' [-Werror,-Wreorder]"

Reviewed By: yfeldblum

Differential Revision: D26788131

fbshipit-source-id: 3664ea96adc26b0f97ad8d11259b018c39254692

Summary: Ensure that threshold is not 0, otherwise when capacity < 10, threshold is 0, which can lead to consumers never transferring credit to producers.

Differential Revision: D26791831

fbshipit-source-id: 741bcf17de18198e43471d4b36d98c79288652fb

Summary: These cause unused variable warnings on other platforms.

Reviewed By: mzlee

Differential Revision: D26771614

fbshipit-source-id: 9170c0da97375682624ee73fe422f34860f35a80

Summary:
On Apple platforms, some of the ucontext methods used here are
deprecated.

Reviewed By: yfeldblum, snufkinsnorka

Differential Revision: D26765225

fbshipit-source-id: 92c7e554b1d1e98b7b8566079a0cb3a0e8afc2d3

Summary: Depending on inlining of std library primitives (e.g. coroutine_handle) it's possible to have more frames in the stack trace.

Reviewed By: yfeldblum

Differential Revision: D26793792

fbshipit-source-id: 44fb1344353e29ec92559ee34740157373112f8f

Summary:
When the given deadline to futexWaitUntil() is less than the idle
timeout that controls purging, MemoryIdler should not purge JEMalloc arenas.
Fix a bug where if the deadline is less than the idle timeout, purging happens
100% of the time unconditionally.

Reviewed By: mogeb, davidtgoldblatt, jalatif

Differential Revision: D26784786

fbshipit-source-id: 316ef96658d0cc2263b973b0b7c345605784eb36

Summary:
With the exception of std::string, nothing else string-like can be
optimized further than a copy. So, create a generic Stringish constructor
that copies .size() elements from .data(), where .data() has a value type
of char.

Reviewed By: yfeldblum

Differential Revision: D5407445

fbshipit-source-id: acf709f07e73bb5bef3f124169c81d76edefa52c

Summary:
Dropping support for earlier zstd versions allows us to remove all of the version check logic.
Zstd-1.4.0 was released in April 2019, and it stabilized a large portion of our API.

Reviewed By: yfeldblum, Cyan4973

Differential Revision: D26585060

fbshipit-source-id: 3e8bd3aa1930c993cc0f2e8fc147db66de9dfdda

Summary:
This modifies the existing `co_bt` gdb script to make use of the new async stack traces available with folly::coro. This adds 2 new commands to gdb:

- `co_bt` with no arguments print the async stack trace for the current thread if there is an async operation in progress. This will print the normal stack frames interleaved with async stack frames as appropriate.
- `co_async_stack_roots` will print the `AsyncStackRoot` pointers available on the current thread
- `co_bt [ADDRESS]` will print the async stack frames starting at the provided `AsyncStackRoot` pointer

Reviewed By: andriigrynenko

Differential Revision: D26719625

fbshipit-source-id: 8edf6ab0851ab92614b3dbeafdf50a517dcc3a61

Summary: Add support for both <coroutine> and <experimental/coroutine> headers. Also add support for __cpp_impl_coroutine (which is required by the standard).

Reviewed By: yfeldblum

Differential Revision: D26745085

fbshipit-source-id: 0bf932e2e30d5b105b1559d817563946fcd3b573

Summary: As a standing rule, let us not have our things be susceptible to ADL except when we very consciously and very specifically want an extension point.

Reviewed By: aary

Differential Revision: D26678138

fbshipit-source-id: 9f845dbc5ed95aaecf4d6cd256aedd0b240e00d3

Summary: Depending on the version of the std library, coro types may be in std or std::experimental namespace. Use coro namespace instead to make switching library implementation easier.

Reviewed By: yfeldblum

Differential Revision: D26744795

fbshipit-source-id: 8856b901d4d757bf378acb56f236135feb0c5488

Summary: Fix github actions builds for projects depending on zstd

Reviewed By: wez

Differential Revision: D26743251

fbshipit-source-id: a3fd8a14750227d025bff763cca8aa683b26a422

Summary:
Callback destruction can involve user logic.  In practice, we
found quite a bunch of patterns like:

```
executor->add([x = someGuardObjectThatTriggersWorkInDtor] {
  ...
});
```

So ensure that dtor is

* Executed under `RequestContextScopeGuard`,
* Protected from leaking unhandled exceptions.

Reviewed By: ot, luciang

Differential Revision: D26744394

fbshipit-source-id: 5fcca0287a98de919c3649a9613e6d54cc1a1ba3

Use ExecutionObserver in EventBase to monitor function not executed EventBaseAtomicNotificationQueueby in EventBase

Summary:
Our service schedules tasks (eSemiFuture/coroutine) on SerialExecutor on top of IOThreadPoolExecutor. When using EventBaseWatchdog to locate long running tasks, I found some long running tasks were not observed by PerThreadExecController. After some investigation, I found there are 2 cases in EventBase that tasks are not executed by handlerReady in EventBaseAtomicNotificationQueue.

1. Short-circuit scenario in runInEventBaseThread which bypasses EventBaseAtomicNotificationQueue.
2. If notification Queue is marked 'internal', some events may be ran "manually" in loopBody.

As a result, the observer logic in EventHandler (EventBaseAtomicNotificationQueue derives from EventHandler) is passed.

Reviewed By: andriigrynenko

Differential Revision: D26563459

fbshipit-source-id: e2741cff373c89a5cd438904f910b23a64fad653

Summary:
Adding support for write and socket timestamps by introducing `ByteEvent` that can be delivered to observers.
`AsyncTransport::WriteFlags` has long had timestamping related flags, such as `TIMESTAMP_TX`, but the code required to act on these flags only existed in proxygen. This diff generalizes the approach so that it works for other use cases of `AsyncSocket`.

This diff is long, but much of it is unit tests designed to prevent regressions given the trickiness of socket timestamps and `ByteEvent`.

**Each `ByteEvent` contains:**
- Type (WRITE, SCHED, TX, ACK)
- Byte stream offset that the timestamp is for (relative to the raw byte stream, which means after SSL in the case of AsyncSSLSocket)
- `steady_clock` timestamp recorded by AsyncSocket when generating the `ByteEvent`
- For SCHED, TX, and ACK events, if available, hardware and software (kernel) timestamps

**How `ByteEvent` are used:**
- Support is enabled when an observer is attached with the `byteEvents` config flag set. If the socket does not support timestamps, the observer is notified through the `byteEventsUnavailable` callback. Otherwise, `byteEventsEnabled` is called
- When the application writes to a socket with `ByteEvent` support enabled and a relevant `WriteFlag`, SCHED/TX/ACK `ByteEvent` are requested from the kernel, and WRITE `ByteEvent` are generated by the socket for the *last byte* in the write.
  - If the entire write buffer cannot be written at once, then additional `ByteEvent` will also be generated for the last byte in each write.
  - This means that if the application wants to timestamp a specific byte, it must break up the write buffer before handing it to `AsyncSocket` such that the byte to timestamp is the last byte in the write buffer.
- When socket timestamps arrive from the kernel via the socket error queue, they are transformed into `ByteEvent` and passed to observers

**Caveats:**
1. Socket timestamps received from the kernel contain the byte's offset in the write stream. This counter is a `uint32_t`, and thus rolls over every ~4GB. When transforming raw timestamp into `ByteEvent`, we correct for this and transform the raw offset into an offset relative to the raw byte offset stored by `AsyncSocket` (returned via `getRawBytesWritten()`).
2. At the moment, a read callback must be installed to receive socket timestamps due to epoll's behavior. I will correct this with a patch to epoll, see https://github.com/libevent/libevent/issues/1038#issuecomment-703315425 for details
3. If a msghdr's ancillary data contains a timestamping flag (such as `SOF_TIMESTAMPING_TX_SOFTWARE`), the kernel will enqueue a socket error message containing the byte offset of the write ( `SO_EE_ORIGIN_TIMESTAMPING`) even if timestamping has not been enabled by an associated call to `setsockopt`. This creates a problem:
    1. If an application was to use a timestamp `WriteFlags` such as `TIMESTAMP_TX` without enabling timestamping, and if `AsyncSocket` transformed such `WriteFlags` to ancillary data by default, it could create a situation where epoll continues to return `EV_READ` (due to items in the socket error queue), but `AsyncSocket` would not fetch anything from the socket error queue.
    2. To prevent this scenario, `WriteFlags` related to timestamping are not translated into msghdr ancillary data unless timestamping is enabled. This required adding a boolean to `getAncillaryData` and `getAncillaryDataSize`.

Differential Revision: D24094832

fbshipit-source-id: e3bec730ddd1fc1696023d8c982ae02ab9b5fb7d

Summary:
Wrapper around `folly::netops` methods that makes it easier to mock these methods in unit tests.

When we want to mock out calls to `folly::netops` we currently:
- Use methods like `getSockOptVirtual` and `setSockOptVirtual`
- Mock part of the socket, like in the tests in `AsyncSSLSocketWriteTest`

I've the latter makes the tests particularly error prone, since we're mocking the object that's also under test.

This change introduces `netops::Dispatcher`, which is a class containing all of the functions in `folly::netops`:
- By default `AsyncSocket` uses a default, static instance of `Dispatcher` that forwards calls to the original `netops::` calls (e.g., calling `netops::Dispatcher::sendmsg` results in a call to `netops::sendmsg`.
- When a test wants to mock a a `folly::netops` call, it can call `setOverrideNetOpsDispatcher` to insert a mock `netops::Dispatcher`. I use it in this manner in D24094832

Differential Revision: D24661160

fbshipit-source-id: e9cb4ed28ffe409c74998a1c9501c0706fc853e0

Summary:
During the wangle accept process and in a few pieces of application code we transform one type of `AsyncSocket` to another, potentially *after* a write has occurred.

Since we do not currently carry `appBytesWritten` and `rawBytesWritten` during transformations, those values may not represent all bytes written. Likewise, if we transform from a `AsyncSSLSocket`, we lose count of the number of raw bytes written.

It's very difficult to reason about whether these problems will actually manifest, so I'd prefer to just guard against it.

With this change, we explicitly track the number of bytes written to the socket by incrementing a counter in `sendSocketMessage`, which is used by both `AsyncSocket` and `AsyncSSLSocket`. In addition, we copy the appBytesWritten and rawBytesWritten during socket moves.

Reviewed By: yfeldblum

Differential Revision: D24551958

fbshipit-source-id: 88416114b52931ff3ceef847401d556ccf0ab664

Summary: Both `AsyncSocket` and `AsyncSSLSocket` currently have code to generate a socket message and control messages with ancillary data. Merge this code into a new function in `AsyncSocket`.

Differential Revision: D24096351

fbshipit-source-id: 87d90648c10c87832f868e322acf59c97b8ac8b7

Summary:
Move `ready_awaitable`, `variant_awaitable` types to `folly/experimental/coro/Coroutine.h`, which reexports the foundational vocabulary coroutine helper types and is a suitable place for these vocabulary coroutine helper types.

`ready_awaitable` is an awaitable which is ready and has a value or, if of void, which is just ready. `variant_awaitable` is an awaitable composed of one of several possible backing awaitables.

Reviewed By: aary

Differential Revision: D26270528

fbshipit-source-id: e98f64b3d3ffaf5bbd322397a41bb5fe85a6bb55

Summary:
`folly::format` is a problematic API because it returns a `Formatter` object that may store references to arguments as its comment warns:

```
 * Formatter class.
 *
 * Note that this class is tricky, as it keeps *references* to its lvalue
 * arguments (while it takes ownership of the temporaries), and it doesn't
 * copy the passed-in format string. Thankfully, you can't use this
 * directly, you have to use format(...) below.
```

This has negative safety and performance (encourages reuse of the same formatter) implications because contrary to what the comment says you can use the object directly since it's returned from `folly::format`. For example
```
auto f = folly::format(std::string("{}"), 42);
f.str();
```
is a UB with no compile-time diagnostic (only caught by ASAN).

It's also unnecessary because the `Formatter` object is usually converted to string straight away via `str()` or written to an output stream. Reusing the formatter doesn't make much sense either because the expensive part is formatting, not capturing arguments.

This diff deprecates `folly::format` suggesting `fmt::format` as a potential replacement. `fmt::format` doesn't have the above problem because arguments are always in scope. It also has the following advantages:

* Better compile times.
* Compile-time format string checks.
* Compatibility with C++20 `std::format`.
* Better performance, particularly with format string compilation which eliminates format string processing overhead altogether.
* Smaller binary footprint.

Also remove `folly::writeTo` which is no longer used and the `format_nested_fbstrings` benchmark which is identical to `format_nested_strings` since there is no `fbstr()` any more.

Reviewed By: yfeldblum

Differential Revision: D26391489

fbshipit-source-id: f0309e78db0eb6d8c22b426d4cc333a17c53f73e

Summary: Follow a convention that function object types with corresponding function object instances be named with a `_fn` suffix.

Reviewed By: ericniebler

Differential Revision: D26674781

fbshipit-source-id: f8a3b8f18677c905897da8bae38cc76693146073