Summary:
Pull Request resolved: https://github.com/facebook/folly/pull/1273

[Folly] Skip some `is_constexpr_default_constructible` tests under gcc7.

In gcc7 specifically, i.e. not gcc6 and not gcc8, some of the expectations fail. The compiler is wrong and this affects the outcome of `is_constexpr_default_constructible`, but this is mostly harmless as far as existing uses go. Fix the tests by skipping them when using gcc7.

Reviewed By: vitaut

Differential Revision: D18820312

fbshipit-source-id: a2d0d53ed2716fffba7840e2b167e9ad4ac012ff

Summary: [Folly] Add `kGnuc` C++ constant representing `__GNUC__` preprocessor constant.

Reviewed By: vitaut

Differential Revision: D18827910

fbshipit-source-id: 43e07e12017df1e7cf4d6a5747e7a85d8a7616f3

Summary: This is the expected design of the class, so suppress the warning using `FOLLY_MSVC_DISABLE_WARNING` instead of fixing the issue.

Reviewed By: Orvid

Differential Revision: D18733718

fbshipit-source-id: ff9368a9ce31ad11e5992d65f0b5b26b2859ff02

Reviewed By: ikostia

Differential Revision: D18814410

fbshipit-source-id: 889306e51c03a29c2b72e34b7dc60db21f11ff97

Summary:
D15485589 updated folly to depend on fmt.  This updates the installed
`folly-config.cmake` file to correctly find the `fmt` dependency, so that
downstream projects that depend on folly still work correctly.

Reviewed By: vitaut

Differential Revision: D18822127

fbshipit-source-id: 970751c7252bf62173d2d26cdc76e46fc08618ba

Summary: This is implicitly used, so explicitly include the file

Reviewed By: Orvid

Differential Revision: D18800769

fbshipit-source-id: 18e1dd06213927370e6a6620863cd68b1d675a14

Summary:
[Folly] Let `ElfFile` open functions take a single builder-style composite `Options` argument v.s. taking a sequence of individual arguments one for each option.

Right now there is only one option but it is possible to add more in the future.

While here, rename and invert `readOnly` to `writable`.

Reviewed By: vitaut

Differential Revision: D18740699

fbshipit-source-id: 6fb016f731bf46a1b4ac6b2efcea739f6261818a

Summary: Shared-ptr, which should be explicitly joined and waits for all other instances to be destroyed.

Reviewed By: spalamarchuk

Differential Revision: D18696536

fbshipit-source-id: 9d7b0b960a00095be7df033680c7a116c358637c

Summary: [Folly] Implement `co_invoke` as a generic CPO with customizations found via ADL.

Reviewed By: lewissbaker

Differential Revision: D18753006

fbshipit-source-id: 16239f0bd6140f56bd23effbf092f2b8279c1350

Summary:
Use the new recvmsg api on the client to receive a packet
from AsyncUDPSocket

Reviewed By: mjoras

Differential Revision: D18797963

fbshipit-source-id: 319d5c41f3a868e7b78947fdbcf2c411b6d7fbf0

Summary:
Add a mode to read callback which only notifies but does not call getReadBuffer.

This also adds a readmsg api for notification callbacks to invoke

This is useful for callbacks that want to perform their own logic of reading from the socket, for example
a callback might want to perform multiple read calls per callback to save on CPU of epoll

Differential Revision: D18797964

fbshipit-source-id: 86bf1553078a20ea16f56f0c404887fca5050065

Summary: Add support for multiple EventBase backends

Reviewed By: simpkins, mjoras

Differential Revision: D16157574

fbshipit-source-id: 915c3f08cac5673b5c4ca52a661b41b8a228df75

Summary: Mark the header as it is not a header provided by folly

Reviewed By: yfeldblum

Differential Revision: D18800770

fbshipit-source-id: 95c9dcdeb6f4b745f0bce859e4d9669c009c353a

Summary:
This diff introduces the following changes:

- EliasFano encoding populates all skip pointers between last value and the universeUpperBound.

Reviewed By: ot, philippv

Differential Revision: D18734361

fbshipit-source-id: 2451614ff99dca22f0247cb572542f8cadc97b6f

Summary: The projects have been moved to a "shed/" subdirectory, so the root Cargo.toml with workspace has to be adjusted to that move.

Reviewed By: farnz

Differential Revision: D18807189

fbshipit-source-id: 0fd66fa7edd38ab4fdf905872f38fac57ae0230e

Summary:
Add a `install_fb_python_executable()` function to `FBPythonBinary.cmake` for
helping to install python executables generated with
`add_fb_python_executable()`.  This primarily helps by automatically looking
up the correct output file to install from the generated targets.

Reviewed By: wez

Differential Revision: D18774539

fbshipit-source-id: 4b397580d72ac448f21d1db6d2cdd653cf3635df

Reviewed By: yfeldblum

Differential Revision: D18780743

fbshipit-source-id: 5b26163f5dabcb14fd9ad7b4d9489d3ca1f6df0d

Summary:
Add hazard-pointer-based implementation to allow concurrent reading during updates. This is done by using lightweight concurrent structures protected by hazard pointers instead of sequential structures protected by read locks.

The implementation is gated by a gflag that is off by default.

Reviewed By: davidtgoldblatt

Differential Revision: D18622072

fbshipit-source-id: 120ba14a7a559883e64a3fdf81b35a26315312c1

Summary:
It's impossible for a consumer of a released version of
rocksdb to do anything about this except not use it, and this particular
version of rocksdb ships with a number of shadow warnings.

Disable warning to error promotion.

See also: https://twitter.com/pcwalton/status/1201679307552083968

Reviewed By: chadaustin

Differential Revision: D18785637

fbshipit-source-id: 1db2b00b3c397d6c0b8f05b9d1c658877685c961

Summary:
I tried building on a fresh docker image ubuntu:16.04, the current setup doesn't work because libunwind-dev is missing. Adding this fixed the problem for me.
Pull Request resolved: https://github.com/facebook/folly/pull/1268

Reviewed By: Orvid

Differential Revision: D18759832

Pulled By: yfeldblum

fbshipit-source-id: 8a861844e0b4687bf0107553274322954fdc1c00

Summary: Similar to other sanitizer macros add one for memory sanitizer.

Reviewed By: pixelb

Differential Revision: D18662903

fbshipit-source-id: aa62dfedbfd1b174403af451e14ace9896b26466

Summary: As per title

Reviewed By: MohamedBassem

Differential Revision: D18781525

fbshipit-source-id: a23d8207bd3776b55ba42ec87598a0a9375848aa

Summary:
When assigning a function whose return type is marked `nodiscard` to a `Function<void(Args...)>`, the fact that we are internally explicitly casting the result of the function call to `void` hides the `nodiscard` warning.

For instance:

```
struct [[nodiscard]] DoNotIgnore {};
Function<void()> fn = [] { return DoNotIgnore{}; };
```

emits no warnings, and when `fn()` is invoked, the `DoNotIgnore` struct gets silently ignored.

This diff causes the warning to be emitted.

It is only enabled on compilers that support `if constexpr`. It could be supported on more compilers at the cost of one or more of the following:

* extra template instantiations
* an additional function dispatch
* SFINAE
* Spamming out 4 more specializations of the `FunctionTraits` template.

Reviewed By: yfeldblum

Differential Revision: D18668177

fbshipit-source-id: 0a2cd1366855a0582ab27bb157998d3a4bf4e5a0

Summary: Provides a way to transition to folly::AsyncSSLSocket for applications that manage their own SSL_CTX

Reviewed By: yfeldblum

Differential Revision: D18625198

fbshipit-source-id: cae8c531203134bbb27b648f3f92a6794b14ea3c

Summary:
OpenBCM libraries are stored with git LFS. As a result, fetcher fetches LFS pointers and not the contents. Use git-lfs to pull the real contents before copying to install dir using NoopBuilder.
In future, if more builders require git-lfs, we would consider installing
git-lfs as part of the sandcastle infra as against repeating similar
 logic for each builder that requires git-lfs.

Reviewed By: wez

Differential Revision: D18759806

fbshipit-source-id: f988a0460107bc0685e7aba107daba9ed88f71e7

Summary:
As titled. This is needed by OpenBCM, and in future, possibly by other
manifests as well.

Reviewed By: wez

Differential Revision: D18759807

fbshipit-source-id: d445dfa382cea4bf96443ab9889926a4abbf0757

Summary:
The previous approach (D16760775) reserved space for inlined function info in each `SymbolizedFrame`.

```
struct SymbolizedFrame {
  Dwarf::LocationInfo location;
  Dwarf::LocationInfo inlineLocations[Dwarf::kMaxLocationInfoPerFrame];
  ...
```

That increased the size of `SymbolizedFrame` and `FrameArray` and lead to stack overflow in some already deep stacks.
```
template <size_t N>
struct FrameArray {
  FrameArray() {}

  size_t frameCount = 0;
  uintptr_t addresses[N];
  SymbolizedFrame frames[N];
};
```

To avoid allocate more space on stack, changed to use extra frames to store inline calls:
- Usually the callers allocate `FrameArray<100>` frames, but the stack trace is usually smaller than 100
- Use the unused slots to fill in inlined function info:
 -- each function gets at most `kMaxLocationInfoPerFrame` (currently 3) inlined entries
 -- when the available buffer fills up no more inlined functions are filled in.

To find the inline calling stack, we need first need to find the subprogram Debug Info Entry (with tag DW_TAG_subprogram) with the given address, then recursively find all the inline subroutines (with tag DW_TAG_inlined_subroutine) in the call stack. Sadly debug info has no index we can use for jump, and a linear search over debug info entries (and their attributes) is needed during the process, which would cause performance regression.

```
buck run mode/opt folly/experimental/symbolizer/test:dwarf_benchmark -- --benchmark

============================================================================
folly/experimental/symbolizer/test/DwarfBenchmark.cpprelative  time/iter  iters/s
============================================================================
DwarfFindAddressFast                                         4.03us  248.36K
DwarfFindAddressFull                                         4.03us  248.18K
DwarfFindAddressFullWithInline                             293.23us    3.41K
============================================================================
```

Reviewed By: luciang

Differential Revision: D17586385

fbshipit-source-id: 1b84b3f3a576573ce24092b433a501a3bdf76be0

Summary: users may need AsyncUDPSocket to send back datagram to clients.

Reviewed By: yfeldblum

Differential Revision: D18764100

fbshipit-source-id: 7ab7cce5711f47db92f43a68b94568729d5746d0

Summary: Workaround for something that looks like a compiler bug

Reviewed By: kevin-vigor

Differential Revision: D18700404

fbshipit-source-id: 6d9c9a40e9e468ee910c5456bcbfdf02c1b1c59a

Summary:
This is the header which provides `_mm_set1_epi8`
(https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_mm_set1_epi8).

Although this header is transitively found via other headers (which is why this
isn't a build failure), without this explicit include IWYU's heursitics around
template functions wrongly assume that this header should be provided by
downstream includers of this header.

Reviewed By: yfeldblum

Differential Revision: D18753275

fbshipit-source-id: 7d6ee934542867f2d1e84d40397f48ea8146facc

Summary:
localPush invoked in recycleIndex can end up looping more than once if it has to retry the update of head. When that happens, the onRecycle call will be made again which will call destructor on the object again if eagerRecycle is true.

Fixed it by making sure only the 1st pass of the loop will call onRecycle.

(Note: this ignores all push blocking failures!)

Reviewed By: nbronson

Differential Revision: D18752349

fbshipit-source-id: 27dcb5c7840f724bbd39f4dc0176e21095a22284

Summary: For this iterator to satisfy the `input_or_output_iterator` concept in range-v3, it must also satisfy the `semiregular` concept, which requires a default constructor.

Reviewed By: yfeldblum

Differential Revision: D18689298

fbshipit-source-id: a38cde0041ceba1aac79128d428df05ee0f00ab4

Summary:
This is an update to the fbcode_builder codebase to allow setting up the python virtualenv with python dependencies installed. I've included wheel and cython (with a pinned version to 0.28.6 which is the only version that works with thriftpy3 at the moment, due to https://github.com/cython/cython/issues/2985) as standard packages since these are required by some of our top-level dependencies (folly and thrift)

As far as I know, there are no other projects that use PYTHON_VENV at the moment except LogDevice so the impact should be minimal.

Reviewed By: lucaspmelo

Differential Revision: D18758383

fbshipit-source-id: 264941311c5e3a19dc4ef2bb78c9a1baa34dfd8c

Summary: As titled

Differential Revision: D18726457

fbshipit-source-id: 717a6cda4a78e1b246f20328df1f01b78560cac5

Summary: [Folly] More direct overload resolution control in `folly::coro::concat`. Just name the type directly rather than using SFINAE, when the SFINAE would just name the type directly in a more roundabout way.

Differential Revision: D18746633

fbshipit-source-id: 6da909834b511426b1cf7bbda0fd7643b5761f14

Summary:
This diff addresses a collection of issues with our thrift-py3 build story in open source.
- Cython 0.29 bug https://github.com/cython/cython/issues/2985 prevents us from loading the generated binary python extensions. I've tested 0.28.6 and it works perfectly.
- Adds ssl to the extensions (since we need SSLContext in get_client, we must have access to the module)
- No need to special case folly_pic. There is really no easy way to get the python bindings to work without using shared library libfolly.so. So, In our build (logdevice) we will build folly as a shared library, this also reduces the complexity everywhere.
- We also need iobuf as extension for thrift to work, added that to setup.py
- Refactored some of the CMake code that had hardcoded file names to use globbing to future-proof this as much as possible.
- Moved `python/lang/cast.pxd` to match the python module name `folly.cast`, so now it lives in `python/cast.pxd`. This simplifies the globbing as well.
- Moved `setup.py` to live in the `/python` directory.
- Added `*.py` in setup.py to pickup any raw python code (including `__init__.py`)

Reviewed By: yfeldblum

Differential Revision: D18685009

fbshipit-source-id: 749b30942a3e5e9e314b5248cc0aa90c6ac1581f

Summary: This is another step of moving the python extensions for folly that are currently defined in thrift's codebase. Another step for getting us closer on unblocking LogDevice to use the python3 thrift client in open-source.

Reviewed By: yfeldblum, vitaut

Differential Revision: D16221352

fbshipit-source-id: bc24fce073d67397f20f28f79c68512444704402

Reviewed By: farnz

Differential Revision: D18726052

fbshipit-source-id: 4f18430342ab6fd4fc82cc7d03e21f3e50e0ce25

Summary: [Folly] Avoid linear recursion in `folly::coro::concat`.

Reviewed By: kirkshoop

Differential Revision: D18746601

fbshipit-source-id: a383715bfc47ae8c0d4baad8799e98699c7cc14f

Summary: [Folly] Remove remnants of replacing `std::string` with the implementation of `folly::fbstring`.

Reviewed By: luciang

Differential Revision: D18738367

fbshipit-source-id: b57d38100c9da38c6351145979ac6d2f677ba817