Summary:
Most of the tests in FunctionSchedulerTest update a variable in one thread (the
FunctionScheduler thread) and then check its value in the main thread.  These
previously were not using any synchronization between the threads.  This fixes
them to use `std::atomic` to ensure proper synchronization.

Reviewed By: wez

Differential Revision: D6880254

fbshipit-source-id: facfbdf06312f731c64389fb4382b5cb078b76b9

Summary:
Hi! I noticed this repo could use some documentation to help new contributors.

**why make this change?:**
Regarding the `CONTRIBUTING.md` -> Including instructions for new contributors to open source is a courtesy that will foster a welcoming and safe open source community at Facebook.

Regarding the Code of Conduct ->

Facebook Open Source provides a Code of Conduct statement for all
projects to follow, to promote a welcoming and safe open source community.

Exposing the COC via a separate markdown file is a standard being
promoted by Github via the Community Profile in order to meet their Open
Source Guide's recommended community standards.

As you can see, adding this file will improve [the folly community profile](https://github.com/facebook/folly/community)
checklist and increase the visibility of our COC.

Closes https://github.com/facebook/folly/pull/719

Reviewed By: flarnie

Differential Revision: D6881011

Pulled By: simpkins

fbshipit-source-id: a6f0988ac2b49f81bb13d3219095105b7b27e66f

Summary: Add a constexpr implementation of `strcmp()`

Reviewed By: yfeldblum

Differential Revision: D6881816

fbshipit-source-id: 08a9e5ab9ef4a422ff6d004ec13b8ec8c71b0d6f

Summary:
- Use `FOLLLY_HAS_FEATURE(cxx_constexpr_string_builtins)` to check for the
  availability of `__builtin_strlen()` on clang, as recommended by the clang
  documentation (https://clang.llvm.org/docs/LanguageExtensions.html)
- Only use `std::strlen()` on gcc, rather than having checks to exclude all
  other compilers.  `strlen()` happens to be constexpr on gcc, but this is not
  required by the standard and cannot be assumed to be true in general.

Reviewed By: yfeldblum

Differential Revision: D6881815

fbshipit-source-id: 88c614419ae390464893087513dc764b0bfddfb8

Summary:
This test has been failing in travis because it is missing test/certs/tests-cert.pem
Mark it as a content dir

Reviewed By: yfeldblum

Differential Revision: D6884000

fbshipit-source-id: c7d42a4b23334781de28f1586ecbde04aea74ff2

Summary:
Update the build steps in the README to build using cmake instead of autoconf
on Linux platforms.

I haven't updated the instructions for Mac OS X or the
`bootstrap-osx-homebrew.sh` script primarily because I have not tested the
steps on Mac.  It sounds like the build is close to working on Mac, but
currently fails due to missing compiler flags to disable some warnings on
clang.

Reviewed By: akushner

Differential Revision: D6780814

fbshipit-source-id: 9c9c211c306d5b35235549ae451bb620098f37e3

Summary:
Update the CMake build process to always invoke test programs from the root of
the repository.  This makes the CMake build consistent with how we run tests
internally at Facebook.

Reviewed By: yfeldblum

Differential Revision: D6880257

fbshipit-source-id: 4c27cc643faa21d9c26faf8c77f6700ec5fe6393

Summary: DeferredExecutor suffered from a case where boosting would not work if no work was present. This change modifies is so that on a call to via the next executor will be set in the DeferredExecutor. When add is called the callback will be stored. Whichever happens second actually enqueues the work on the chained executor. get uses via to correctly implement this.

Reviewed By: andriigrynenko

Differential Revision: D6663244

fbshipit-source-id: 74600d511373e0f6f7ca4128f25f3947a4981200

Summary: Android also has limited support for thread_local so we should not enable it at all as a precaution

Reviewed By: magedm

Differential Revision: D6884145

fbshipit-source-id: f39dd8fd5405ca0bc5be9b3538718a6f58058442

Summary: Make EventBaseLoopController not dependent on EventBase's runOnDestruction. This will allow us to make FiberManager work with any Executor.

Reviewed By: yfeldblum

Differential Revision: D6828478

fbshipit-source-id: 4d74776044a02954d022ef6f6f1e6834839973b8

Summary:
FunctionSchedulerTest.cpp was unfortunately copied into folly twice in separate
locations.  D1845525 moved it into `folly/test`, D2051557 moved it into
`folly/experimental/test`

The version in `folly/experimental/test` has had several updates and new tests
added; the version in `folly/test` has had no significant changes since it was
first added.

This diff deletes the older copy in `folly/test`

Differential Revision: D6880255

fbshipit-source-id: 8a4d5f6421ec18b319ffd76f98915e925b407468

Summary:
Sometimes the compiler lies to us and says it supports thread_local when it is not always fully implemented.

Unconditionally disable this when `FOLLY_MOBILE` is set

Reviewed By: yfeldblum

Differential Revision: D6875230

fbshipit-source-id: 051f79eac78da03973bad9090b6577393b88998b

Summary:
Disable running the async_test in open source builds.  A few of the tests
functions in this binary are flaky.

Additionally, this test consistently hangs in Travis CI builds.  It hangs in
`AsyncSocketTest.ServerAcceptOptions`; I suspect it never sees the socket
accept event and therefore never breaks out of the loop.  I suspect that even
if we fixed this test other subsequent tests would also hang.  We should
ideally update all of the tests to always have their own internal event base
loop timeout rather than potentially looping forever, so it could at least run
other test functions after a hang like this.

Reviewed By: yfeldblum

Differential Revision: D6874011

fbshipit-source-id: 46c07a1cf3216eda1900e214447e6e49b6c8e489

Summary:
[Folly] Move `invoke` helpers into a special detail namespace.

So that code in `namespace folly::detail` can use `invoke_result`, etc., unqualified.

Reviewed By: aary

Differential Revision: D6869406

fbshipit-source-id: 1b0ebbfb16621cf7e32c0f89162a19410a70605a

Summary:
Update our continuous integration configuration files to invoke ctest with the
`--output-on-failure` flag so it will print the output of all tests that fail.
Without this flag it is rather difficult to debug test failures in CI.

Reviewed By: yfeldblum

Differential Revision: D6869299

fbshipit-source-id: 02d2e1ac03f786034b20797d02e9c3aa64c1b30b

Summary: #title

Reviewed By: yfeldblum

Differential Revision: D6864158

fbshipit-source-id: 13c98c3e44db6febae844f099baa9fbecc9db673

Summary:
Change some `EXPECT_EQ()` statements to `EXPECT_TRUE()` and `EXPECT_FALSE()`.
This was causing compilation failures on some gcc-4.9 platforms.

Reviewed By: yfeldblum

Differential Revision: D6869102

fbshipit-source-id: c3294eeca90130fec601c60a76cfa4dc1bc81639

Summary: Removed instances of logging reclaim_

Reviewed By: mzlee

Differential Revision: D6864752

fbshipit-source-id: d36205052799d2307e1cd6a0307c094ac3fa8b26

Summary:
Various folly tests failed to compile when using the older gcc-4.9 version.
Since we apparently want to keep supporting gcc-4.9 for a bit longer, update
the code so that it can be compiled with gcc-4.9.

Reviewed By: yfeldblum

Differential Revision: D6817546

fbshipit-source-id: a5224560330b49e94e10d21f81a83538ec7f34e9

Summary: Add fbcode_builder configs for folly to folly/build.

Reviewed By: yfeldblum

Differential Revision: D6700053

fbshipit-source-id: 3b9e974f727e7b7815580d8a12a6adfc3b529866

Summary:
The code in PriorityThreadFactoryTest.ThreadPriority attempted to set the
thread niceness to 1.  This would fail if the process was already running at a
higher niceness value and was not being run as root.

This updates the test to get the current niceness first, and to use that plus 1
as the niceness value to change to.

Reviewed By: yfeldblum

Differential Revision: D6817548

fbshipit-source-id: 80e740f1fbe751865a418a58081bde4086b21679

Summary:
Update the ExceptionWrapperTest to check typeid strings against the result of
calls to `demangle()`, rather than expecting `typeid(int)` to always be
demangled as the string "int".  When building with gcc-7.2 on Ubuntu 17.10
these type strings appear to be demangled simply as "i".

Reviewed By: yfeldblum

Differential Revision: D6817545

fbshipit-source-id: 134952106ad812f6980516247081bb9718b5ab38

Summary:
Update folly's TestMain program to enable glog logging to stderr by default.

Some of the tests in folly/experimental/test/TestUtilTest.cpp require that this
is enabled, and fail if log messages are not logged to stderr.

Reviewed By: yfeldblum

Differential Revision: D6817543

fbshipit-source-id: 87724c52124e72ad19f65524bcbd6536680f02ec

Rename hazptr DEBUG_PRINT macro to HAZPTR_DEBUG_PRINT to avoid name clashes with other uses in code.

Reviewed By: yfeldblum, magedm

Differential Revision: D6863117

fbshipit-source-id: 1626eacafbdddcfdaf181b2a5d0f6e216425b1ff

Summary:
Drop instructions for building on Ubuntu 12.04, 13.10, and 14.04.  The oldest
Ubuntu platform we support these days is 16.04.

Our Travis CI configurations do still test building on Ubuntu 14.04 for now,
but it is not a vanilla 14.04 installation.  We upgrade gcc to 4.9 and CMake to
3.2 in order to build folly on this older Ubuntu version.

Reviewed By: yfeldblum

Differential Revision: D6780815

fbshipit-source-id: 0d27cdbb928d32c1527623c8862d50ce2215dd48

Summary:
Fix a few unused parameters. One was unconditional; the other two are conditional based on some configuration values set during CMake configure time.
Closes https://github.com/facebook/folly/pull/747

Reviewed By: djwatson

Differential Revision: D6858958

Pulled By: yfeldblum

fbshipit-source-id: acb7fa5a79b9abfdf3dc210f649d0dea8ca4a87a

Summary: [Folly] Generate group varint tables at compile time in C++, rather than as a separate custom build step in Python.

Reviewed By: simpkins

Differential Revision: D6832563

fbshipit-source-id: fa218c512cbac383f153e7b6fd4df7f181bcb0de

Summary: [Folly] Generate format tables at compile time in C++, rather than as a separate custom build step in Python.

Reviewed By: ot

Differential Revision: D6830372

fbshipit-source-id: 25770676e59c8070eaef7cbb691a5ba1c4b0a8f8

Summary: [Folly] Generate format tables at compile time in C++, rather than as a separate custom build step in Python.

Reviewed By: ot

Differential Revision: D6829681

fbshipit-source-id: 160b5a7616b015cc37ff389adabfec095cf136ec

Summary: Fleshes out the SemiFuture API with waiting versions of xVia calls that take a TimedDrivableExecutor that can be driven until some time point.

Reviewed By: yfeldblum

Differential Revision: D6658862

fbshipit-source-id: 74906d8101d2a762a27da1a1ec8348f106037f5d

Summary:
[Folly] Use `invoke` in `applyTuple` implementation.

V.s. reimplementing `invoke` as `makeCallable`

Reviewed By: spacedentist

Differential Revision: D6843993

fbshipit-source-id: 82f3e121486972245b75f808654d0a1299b7eafe

Summary:
[Folly] Fix missing "last-minute-reprieve" load-acquire in `Baton` and `SaturatingSemaphore`.

If the CAS fails, it is because `post` with its store-release was invoked just after spinning but just before parking the thread. So the failure load needs a matching load-acquire.

We cannot actually move the load-acquire into the CAS until C++17, since the failure memory order must be not stronger than the success memory order until C++17. Therefore, simulate the effect with an acquire fence in the CAS failure case.

The CAS success case does not need a load-acquire; there is already a load-acquire after the thread is unparked.

Reviewed By: davidtgoldblatt

Differential Revision: D6851304

fbshipit-source-id: a43243ad6a35bd9a53a9d2a5958b50a6c8806419

Summary:
It can be dangerous to set a CMake variable and not wrap the values as strings at times. The arguments can be forwarded to the compiler in use which will not know how to handle multiple arguments getting treated as one. For an example error using CMake 3.9.6 and Clang 5.0.1, if you do not wrap `CMAKE_CXX_FLAGS_COMMON` using string literals, you will get an error:

```
Problems were encountered while collecting compiler information:
	clang-5.0: error: unknown argument: '-g;-Wall;-Wextra'
```

Closes https://github.com/facebook/folly/pull/746

Reviewed By: simpkins

Differential Revision: D6854510

Pulled By: yfeldblum

fbshipit-source-id: c3ae626033e6733d0ce6f19fc6c06190315bf0db

Summary: [Folly] `make_array_with`, for making `std::array` given size and item ctor

Reviewed By: ot

Differential Revision: D6831280

fbshipit-source-id: 448bbf4843ffa70324f1a1d2d9e2790dc296548d

Summary: Flakyness was caused by a small chance that the function would still be in the heap when adding a function. Increased delay to 3 seconds.

Reviewed By: yfeldblum

Differential Revision: D6855408

fbshipit-source-id: 47d4035698a5d14a7ed71902656210f0e17b0b5d

Summary: Add steps to hazptr_obj construction and retirement to catch misuse bugs such as double retire.

Reviewed By: yfeldblum

Differential Revision: D6851965

fbshipit-source-id: 026e578b595792e3118b6b4b9a22c8c1dce6acba

Summary: In future chains destruction of the future then the promise will cause an exception to propagate. If all the work builds up in the executor and the executor does not drain then the exception does not propagate.

Reviewed By: yfeldblum

Differential Revision: D6837229

fbshipit-source-id: 095650b8aae0de4ddbe86c044d78a6fac45f9c46

Summary:
The googletest framework does not have a built-in mechanism for skipping tests
at run-time.  Folly uses a `SKIP()` macro for some tests to report themselves
as skipped.  For our internal builds these are reported as failures with a
special message that gets handled by our test runner framework.  However for
open source builds it is better to report these tests as passing rather than as
failing.

Reviewed By: yfeldblum

Differential Revision: D6843331

fbshipit-source-id: f74f29354305703448e5757ddc0ec3e72380a8f7

Summary:
This reverts commit 5ad448f0aad8f51f4328bfe9af37d63023089e88

bypass-lint

An infra SEV is better than not reverting this diff.
If you copy this password, see you in SEV Review!
cause_a_sev_many_files

Differential Revision: D6851455

fbshipit-source-id: d96ac9c2f907f09a4086ccf65ec4a3ef47cad205

Summary:
[Folly] Fix when the Timekeeper is destroyed with in-flight delays.

Previously, the Timekeeper dtor would immediately trigger the delayed callbacks early with a success result. But there are various situations where that is wrong behavior, such as when the callback enqueues more delayed callbacks in the success path. Higher-level, a future returned by `Timekeeper::after` or `sleep` would be completed early with a value.

Now, let it immediately trigger the delayed callbacks early with an error result. Higher-level, a future returned by `Timekeeper::after` or `sleep` will be completed early with an error.

Also: use `NoTimeout` consistently, and, on interrupt, pass the interrupt exception through.

Differential Revision: D6837669

fbshipit-source-id: 7d18d7f57999d56bbb5269cacdb443ac22448cf0