Summary:
This runs a command, raising an exception if it exits with a non-zero error status.

It prints out the arguments in a mostly copy-and-pasteable form, with PATH-like
env vars pretty printed to make it easier to see what is being invoked; here's
an example of how cmake is being invoked later in this stack:

```
 ---
+ CMAKE_PREFIX_PATH=\
+      /data/users/wez/scratch/dataZusersZwezZfbsource/fbcode_builder_getdeps/installed/ninja-5d7ec7:\
+      /data/users/wez/scratch/dataZusersZwezZfbsource/fbcode_builder_getdeps/installed/cmake-91dc9a:\
+ PKG_CONFIG_PATH=\
+      /data/users/wez/scratch/dataZusersZwezZfbsource/fbcode_builder_getdeps/installed/ninja-5d7ec7/lib/pkgconfig:\
+      /data/users/wez/scratch/dataZusersZwezZfbsource/fbcode_builder_getdeps/installed/cmake-91dc9a/lib/pkgconfig:\
+ cd /data/users/wez/scratch/dataZusersZwezZfbsource/fbcode_builder_getdeps/build/zstd-470344 && \
+ cmake configure /data/users/wez/scratch/dataZusersZwezZfbsource/fbcode_builder_getdeps/repos/github.com-facebook-zstd.git/build/cmake -DCMAKE_INST
ALL_PREFIX=/data/users/wez/scratch/dataZusersZwezZfbsource/fbcode_builder_getdeps/installed/zstd-470344 -DBUILD_SHARED_LIBS=OFF -DCMAKE_BUILD_TYPE=R
elWithDebInfo -G Ninja
```

Reviewed By: simpkins

Differential Revision: D14690999

fbshipit-source-id: cdb0c681c7dfdfdc6e8c96bf4830bfbcf666411b

Summary:
This is the new getdeps entrypoint.  It lives in `opensource/fbcode_builder` so that
it is synced into the various opensource projects at FB.

In the incarnation in this diff is has a single subcommand that can be used to validate
a manifest file.

Reviewed By: sinancepel

Differential Revision: D14690995

fbshipit-source-id: 53f8ec9bafb7b1930970079e3ce20f496ac1c188

Summary:
Add some helpers for manipulating environment variables
that will hold either compiler flags or paths.

These are used in later diffs when setting up arguments/environment
for eg: cmake.

Reviewed By: sinancepel, simpkins

Differential Revision: D14690993

fbshipit-source-id: 7f9753cd99d968550fe9e3ba8b7017a44683061e

Summary:
These are ported over from the logic in the watchman and eden getdeps
scripts, with additions to help bootstrap a build environment.

These are sufficient to build watchman with thrift support on windows, mac and
linux, and eden on mac and linux when combined with the getdeps code that
follows in later diffs in this stack.

Reviewed By: simpkins

Differential Revision: D14691005

fbshipit-source-id: 7f8b02fedcdc020e2d0e758c466959d8161d4587

Summary:
Adds a parser for manifest files that describe projects
that may be either 1st party or 3rd party.

A selection of manifest files appears in a later diff in this stack.

This diff provides the raw parser and a couple of low level helpers.
It also defines a mechanism for validating the schema to help catch
structural (rather than semantic) issues with manifest file contents.

Later diffs in the stack add helpers for accessing the data in
a higher level way.

Reviewed By: sinancepel

Differential Revision: D14691003

fbshipit-source-id: 7d2930a3359ede0f6e21fdc45686b083ab7a9ffa

Summary:
As part of folding getdeps into fbcode_builder, this
expression parser is needed to allow constrained and deterministic
conditionals in the manifest file format.

For example, the watchman manifest will use this cargo-inspired syntax
for system dependent sections:

```
[dependencies]
folly

[dependencies.not(os=windows)]
thrift
```

Reviewed By: sinancepel

Differential Revision: D14691014

fbshipit-source-id: 080bcdb20579da40d225799f5f22debe65708b03

Summary:
Detect at runtime whether testpilot is the test runner to decide how
to communicate skip status.

Reviewed By: simpkins

Differential Revision: D15073229

fbshipit-source-id: 417a1f4e42d0655e25cc62b0abb016c157d1adea

Summary:
Allow the eventbase to be constructed with a higher-precision timer, for those callers that need more precision for shorter (or higher entropy) waits.

(Note: this ignores all push blocking failures!)

Differential Revision: D15186374

fbshipit-source-id: 98cca2d15fc18f9e865129f4629a4351e9a8b9c9

Summary:
there were test failures that fell into three buckets

first, the strands worker had concurrency issues. the handoff between submit and the worker was wrong.

second, take_until was not waiting for the producer to signal done. this was originally by-design. now the expectation is that take until will not early-complete on cancellation.

third, the tests had concurrency issues. the EXPECT assertions were not allowing for non-deterministic interleaving.

Reviewed By: lewissbaker

Differential Revision: D14947473

fbshipit-source-id: 36f7cf87b9226367dc44afed663fa6418503c059

Summary: [Folly] Let `folly/FBVector.h` support `-fno-exceptions`. Same mechanism as with `folly/small_vector.h`.

Reviewed By: Orvid

Differential Revision: D15158754

fbshipit-source-id: fe67d608a5b38258d05718efae502b7277e1f4ee

Summary: This also makes co_awaitTry to work for any SemiAwaitable that implements await_resume_try in it's awaiter.

Reviewed By: yfeldblum

Differential Revision: D15170076

fbshipit-source-id: 7f6ce0e2fa762acc5bcc4a32ed29d189787bf1ef

Summary:
use PUSHMI_TEMPLATE_DEBUG in a few more places
add some additional code to the submit customization point to allow the compiler to emit error info when none of the fallbacks worked.

Reviewed By: yfeldblum

Differential Revision: D15016463

fbshipit-source-id: 1c43c21093d54d662c1d084040608db0e0c029be

Summary: Original commit changeset: 04dbc7bc7752

Reviewed By: vchynarov

Differential Revision: D15168113

fbshipit-source-id: a69618eabec30e7599c13bb32c25f6efd6da561e

Summary: Switch to the correct callability check to match the internals. Without this change then is ambiguous and can still generate errors on polymorphic lambdas.

Reviewed By: yfeldblum

Differential Revision: D15147830

fbshipit-source-id: 3f577641495a24076e9ffa19deaad190452c420c

Summary:
Disabling the nullptr conversion to non-pointer folly::Optional<T> has
baked long enough. Re-enabled it with the same behavior that
std::optional has.

Reviewed By: Orvid

Differential Revision: D15151503

fbshipit-source-id: d170f3f0e6bf3bb4461f17bdb6f8078b5a883615

Summary: Call folly::SingletonVault::singleton<BenchmarkTag>()->registrationComplete() to avoid an assert

Reviewed By: yfeldblum

Differential Revision: D15159381

fbshipit-source-id: 6f3be22d433e77d6e1b5293098a6dedd42e65bb6

Summary: Trivial change to remove comments that were initially accurate but inaccurate once we decided to DCHECK on the executor instead.

Reviewed By: yfeldblum

Differential Revision: D15148289

fbshipit-source-id: 5d0495f4b36db3a0c8610592bc759e121ed1dcff

Summary:
When built as a static library on Win32, `zstd` has an output name like `zstd_static.lib` and `zstd_staticd.lib`:
https://github.com/facebook/zstd/blob/69baaee3e42f90dedea2c946bc19bfeac4e782ee/build/cmake/lib/CMakeLists.txt#L140
So `FindZstd.cmake` should also take this into consideration.
Pull Request resolved: https://github.com/facebook/folly/pull/1120

Reviewed By: yfeldblum

Differential Revision: D15149814

Pulled By: Orvid

fbshipit-source-id: 298809a524468ab5aa68e58f5fef0cbb0f366051

Differential Revision:
D15057633

Original commit changeset: 6ba47a57a78e

fbshipit-source-id: 1ae1384e5e9de3f2e80571b626a41ef6e713b3b2

Summary:
[Folly] Enforce `SingletonThreadLocal` uniqueness also in the case where `FOLLY_TLS` is not defined.

Since the uniqueness check should happen in all scenarios, just move it to a place which is not subject to conditional compilation.

Reviewed By: yfeldblum

Differential Revision: D15142661

fbshipit-source-id: 04dbc7bc775255a010f24c1496552cfc27970e1f

Summary: Another overload that is not really necessary and adds complication. Removing to simplify.

Reviewed By: yfeldblum

Differential Revision: D15110009

fbshipit-source-id: a7a90799ff4d89d45ae82d2e755be5ee3799104c

Summary: This is mainly to workaround bugs triggered by LTO, when stack allocated variables in await_suspend end up on a coroutine frame.

Reviewed By: lewissbaker

Differential Revision: D15143193

fbshipit-source-id: 9553274e2d9c021902d9d19e7ecb2a91a86e787a

Summary:
Disabling the nullptr conversion to non-pointer folly::Optional<T> has
baked long enough. Re-enabled it with the same behavior that
std::optional has.

Reviewed By: yfeldblum

Differential Revision: D15057633

fbshipit-source-id: 6ba47a57a78ec4834ed4ecc8987a7c8870102ae4

Summary: Another overload that is not really necessary and adds complication. Removing to simplify.

Reviewed By: yfeldblum

Differential Revision: D15109455

fbshipit-source-id: 4312aab817d9796358e0b659c50c6e8f9d9ccb4e

Summary:
after discussion with Lewis, change the contract for empty and error signals from the underlying executor in the strand implementation.

error will forward the error to items in the queue and then reschedule for any remaining items

done will forward the empty signal to items in the queue and then reschedule for any remaining items.

These changes should prevent infinite scheduling loops and allow the underlying executor to push back against the items being submitted to the strand.

Reviewed By: lewissbaker

Differential Revision: D14955343

fbshipit-source-id: 926109594d7aed1766d868b705c84a6ed664e2f3

Summary: Adds a SemiFuture variant of collectAny and forwards collectAny to it. This ensures that both options are available.

Reviewed By: yfeldblum

Differential Revision: D15111077

fbshipit-source-id: f4d6efc684ca632b71f7a8d2659ca4d968d15b6f

Summary: Make sure the future object doesn't get destroyed concurrently with the setCallback_ call.

Reviewed By: yfeldblum

Differential Revision: D15122238

fbshipit-source-id: c8de1cd158f317c3ed7591460ca2cccfa7633ae7

Summary: Allow calling `baton.reset()` concurrently with `co_await`.

Reviewed By: yfeldblum

Differential Revision: D15058504

fbshipit-source-id: af7ff69ddc2c8a4663e0f7ef03121c01502a984d

Summary:
Just a minor typo fix: `Github` -> `GitHub`.
Pull Request resolved: https://github.com/facebook/folly/pull/1119

Differential Revision: D15120076

Pulled By: yfeldblum

fbshipit-source-id: e0caccc022d0d740fd25ad1697b130fe7680f9a3

Summary:
`WriteFlags::EOR` currently marks the end of a record (e.g., an HTTP response) and is used to request ACK timestamping.

`WriteFlags::TIMESTAMP_TX` will be used to request timestamping when the entire write buffer has been transmitted by the NIC. If hardware timestamps are unavailable, then the timestamp will be taken when the the entire buffer has been handed to the NIC by the kernel. TX timestamps can be compared to send() timestamps to determine how long the write buffer was waiting in the kernel to be sent to the NIC. In the case of a large CWND + LOWAT, this could be a significant amount of time. In addition, TX timestamps help with throughput calculations as they enable the precise transmit time to be determined.

We may want to rename `WriteFlags::EOR` or add a separate flag for ACK timestamping. For now, I've clarified the purpose of this field.

Reviewed By: yfeldblum

Differential Revision: D15081941

fbshipit-source-id: 239833cd5a0413e7468840960118a038ffdac068

Summary: It's unsafe to read Executor from Core, because it can be concurrently modified by a consumer thread.

Reviewed By: yfeldblum

Differential Revision: D15117907

fbshipit-source-id: 40caf4b2878609775c1c8476336349ddf3764d4d

Summary:
- `HasArgumentTypes` uses nested `boost::mpl::transform` calls to strip
  reference qualifiers from the function argument types and then another
  `mpl::transform` call to remove `const` qualifiers.
- Replace the nested `mpl::transform` calls to just one call by using
  `folly::remove_cvref`.
Pull Request resolved: https://github.com/facebook/folly/pull/1086

Reviewed By: Orvid

Differential Revision: D14638843

Pulled By: yfeldblum

fbshipit-source-id: 8c360e50ffaba0328aa8e4c86245ce25d45bc01b

Reviewed By: lewissbaker

Differential Revision: D15114457

fbshipit-source-id: 0f49d631bd316fda828946971b607c94ee75250b

Summary:
- `fbstring_core` defines constants based on the host endianness.
- This is purely duplicated as these constants live in `Portability.h`.
  As such, remove them from `fbstring_core` class.
Pull Request resolved: https://github.com/facebook/folly/pull/1117

Reviewed By: Orvid

Differential Revision: D15096910

Pulled By: yfeldblum

fbshipit-source-id: ff4e828dfd1b19daeedf48bbf1719a3fd72c0843

Summary:
- Implement `erase` and `erase_if` for both `FBVector` and
  `small_vector`.
- This matches the APIs as in the C++20 Library Fundamentals v2.
Pull Request resolved: https://github.com/facebook/folly/pull/1089

Reviewed By: Orvid

Differential Revision: D15112753

Pulled By: yfeldblum

fbshipit-source-id: dc93c600fa8e7e8a7ed42d6a6e07439d4fa51204

Summary: as title

Differential Revision: D15115871

fbshipit-source-id: 16eff7f913bdd782192ffc0e06f03f1cf8f48393

Summary:
This change has no effect for normal use of the semaphore.

With try_acquire (previous change), we now allow the callers to pass their own baton.
It's possible that the caller ends up not needing to use the `post`, and simply wants to signal the semaphore. It's basically useful in scenario where the caller wants to wait for the first of multiple events.
Current code would deadlock in this scenario, this fixes it.

Reviewed By: andriigrynenko

Differential Revision: D15090395

fbshipit-source-id: 8e3d73705ef3559717b7335f6a9e9ea8bed1cb17

Summary: This provides an interface for the Semaphore, which allow async waiting for more complex usage on fiber, without the future overhead.

Reviewed By: andriigrynenko

Differential Revision: D15082111

fbshipit-source-id: 76306525509f36867999db459ee0b7c42f416b6c

Summary:
This new test should have been inside the
FOLLY_F14_VECTOR_INTRINSICS_AVAILABLE conditional compilation guard.

Reviewed By: mengz0

Differential Revision: D15114483

fbshipit-source-id: 2931be7d4abf7a4a95827052905bd219c9beff13

Summary: It's unsafe to use Future after setCallback was called (its executor may be moved out), so we have to copy its executor before that.

Reviewed By: yfeldblum

Differential Revision: D15113490

fbshipit-source-id: 2fa9c323ddfe1919b84bbfe05b6c5643d0c65703