Summary: This is the second attempt, the first one was D22958650. Decided to do a different diff as some affected files were moved from experimental/afrind/coro/h2proxy to proxygen/facebook/lib/experimental/coro/ which created some confusion while arc pulling

Reviewed By: yfeldblum

Differential Revision: D25432869

fbshipit-source-id: a183898302a79084d890548b9b7ecc4409f501d2

Summary:
`/proc/self/exe` doesn't exist on apple platforms, so provide an
implementation that does.

Reviewed By: yfeldblum

Differential Revision: D26599826

fbshipit-source-id: e00dde59d639063e59cb97feb75caf0a49a01954

Summary: Move `order_preserving_reinsertion_view` to a new header `folly/container/View.h` and revise its customization facility in terms of `folly::tag_invoke`.

Reviewed By: iahs

Differential Revision: D25787117

fbshipit-source-id: b7ccd3b6a1413a2639ef1beb1f1ee23bbed045e3

Summary:
This'll move getdeps dependency for katran to 0.3 (which is already the case
for travis build)

Reviewed By: avasylev

Differential Revision: D26129525

fbshipit-source-id: ec9d0615a3e02d75454a3f9dd974ac5c7589e40a

Summary: IoUringBackend benchmarks

Reviewed By: kevin-vigor

Differential Revision: D26594012

fbshipit-source-id: c6a08e6ec13b736c32619958713706118e2f1a49

Summary: No need to overload coroutine `promise_type::return_value` to handle initializer list expressions - just template and default the parameter.

Reviewed By: Orvid

Differential Revision: D26508901

fbshipit-source-id: 61c4a2225355b0044638cd89b9153d599317a453

Summary: When EventBase is destructed, the underlying local storage should be destructed prior to event loop being destroyed.

Reviewed By: andriigrynenko

Differential Revision: D26583298

fbshipit-source-id: 9bfb8442b2a827aa2b3564b27ea765ec1e7b26a2

Summary: Owing to a set of bugs, it is not currently possible to actually declare ranges::enable_view without actually defining it, so we have to include the actual definition when we're in compilation units with it available. If the definition is not available, then the `const` form is sufficient to keep things compiling.

Reviewed By: yfeldblum

Differential Revision: D26337214

fbshipit-source-id: fb042b62967e3e6f536e8268e1b6dd6ccd20b810

Summary: Some compilers fail when `friend` declarations have mismatched `constexpr`-specifiers.

Reviewed By: Mizuchi

Differential Revision: D26601032

fbshipit-source-id: a49e327ff9353ddb21eac96776f97d4089c85374

Summary: Use `std::filesystem` or `std::experimental::filesystem`, via `folly/portability/Filesystem.h`, in `folly/test/FileTest.cpp`. Replaces the use of `boost::filesystem`.

Reviewed By: Orvid

Differential Revision: D26572916

fbshipit-source-id: f769e00b2772f3bfaed899f5694d89db87089e35

Summary:
Make the implementation of `folly::fs::lexically_normal` match C++17 `std::filesystem::path::lexically_normal`. The implementation from `boost::filesystem::path::lexically_normal` is easy to fall back on but has some differences.

The implementation is copied mutatis mutandis from https://github.com/gulrak/filesystem/ at tag v1.5.0, in which `ghc::filesystem` is a complete portable standalone implementation of the `std::filesystem` spec and released under the MIT license.

Reviewed By: Orvid

Differential Revision: D26572520

fbshipit-source-id: 5ce03f37c078ee4f62e3480d4abc259199867c8e

Summary: [Folly] Prefer to nest helper functions in coro tests within the specific tests which use them.

Reviewed By: ispeters, Orvid

Differential Revision: D20324066

fbshipit-source-id: 4134145c406f2d1fdeaddf9a7d244c1bd25ec60b

Summary: Some versions of gcc miscompile the code in the parallel-map exception test. Work around the miscompile by adding an extra log line.

Reviewed By: Orvid

Differential Revision: D26509079

fbshipit-source-id: 1474437d96aeabad0294bcb395b7baec229eb9ba

Summary: The CMake function `check_cxx_compiler_flag` is snake-case rather than uppercase.

Reviewed By: vitaut

Differential Revision: D26573998

fbshipit-source-id: 91d5e2cea933d35967d013b2344e50f52fb6ba77

Summary: Tweak a test that relies on hardcoding the expected result of `std::exception().what()` instead to call that and use the result without hardcoding it.

Differential Revision: D26573226

fbshipit-source-id: 3802d12186c96b864e2680d99f5cfca185235f8d

Reviewed By: andriigrynenko

Differential Revision: D26572552

fbshipit-source-id: 035e1313cd4dec070555b5cd41efc58a0b4a948a

Summary:
Revise `EventBaseLocal` interface to export the suite `emplace`, `try_emplace`, `emplace_with`, and `try_emplace_with`, and adding initializer-list overloads for completeness.

This mirrors the interface of `DelayedInit`.

Differential Revision: D26262870

fbshipit-source-id: 951e2f781a1b5546d96adb2e77aa1cadfbff2d6b

Reviewed By: yfeldblum

Differential Revision: D25514804

fbshipit-source-id: 7e6ad5c6063d2cf5047f656c0f2336b34576c60b

Summary: EventBaseLoopController does this already. This way it's safe to destroy FiberManager even if some local callback is left in the executor.

Differential Revision: D26563934

fbshipit-source-id: 0845e5c532634fa9c53694cd67e983886cea82de

Summary:
A portability header for `<filesystem>` backed up by `<experimental/filesystem>`.

The only thing it does is figure out the right header to include and the right namespace to import so that folly code which already may assume C++17 can use names via `folly::fs`.

And polyfills `lexically_normal`.

Reviewed By: Orvid

Differential Revision: D26453988

fbshipit-source-id: 7a7b2e7a312f5d0438d60bc866b109240d096520

Summary: Technically speaking the contract of isRunning() is unclear on whether it can be used as a synchronization mechanism; it could, e.g. be used solely for diagnostics purposes, in which case memory_order_relaxed would be enough. But it is used at least to implement waitUntilRunning(), so memory_order_acquire/memory_order_release is needed to achieve proper synchronization.

Reviewed By: yfeldblum

Differential Revision: D26436697

fbshipit-source-id: 2be07c473e1cb286e6044fa677304816921e888d

Summary:
Currently, the first thing you want to do when getting a context from the pool is
reset it, because you don't know the state the last user left it in. This is bug
prone, because you may forget to reset the context. Instead, the pool should
handle the resetting logic, so it cannot be forgotten.

This diff adds a `Resetter` to the pool, and the reset function is called every
time a context is returned to the pool. I chose to reset when returning to the
pool instead of when retrieving a context because that gives the context a
chance to free any resources it doesn't expect to need in the future before it
potentially becomres idle.

Reviewed By: Cyan4973

Differential Revision: D26439710

fbshipit-source-id: 8b9afa3db2fda4d167f0fd5307791e8a8a4f283c

Summary: We already cache the contexts in the context pool. We don't also need to cache the contexts in the `Codec` when the user keeps the codec around. This will allow us to better utilize the contexts, and potentially reduce memory usage.

Reviewed By: felixhandte

Differential Revision: D26356275

fbshipit-source-id: 6d80326f469de61094478c73b6fe557eebcd7a22

Summary: Mark the param to `folly::type_info_of` param as `[[maybe_unused]]` since, when RTTI is unavailable, it is unused.

Differential Revision: D26537864

fbshipit-source-id: 3fd0a1bb0d3ecbbcdc5e07f153e321a0b8537478

Summary: Let `FOLLY_MAYBE_UNUSED` which wraps `[[maybe_unused]]` support MSVC even when the latter misreports `__cplusplus`.

Differential Revision: D26537706

fbshipit-source-id: 37554b7f9d27332088b72de41e53a5b85ef46327

Summary: This permits removal of the `_getptd()`-based implementation of `folly::uncaught_exceptions` sometimes used on windows, in favor of forwarding to `std::uncaught_exceptions`.

Reviewed By: akrieger

Differential Revision: D26509011

fbshipit-source-id: b8fd14df91fcd849420d3c52328cb080b528245b

Reviewed By: andriigrynenko

Differential Revision: D26497717

fbshipit-source-id: 35307fce7f9e85882f8f9e5a6bdfe651122727a3

Summary: Ensure all the tests in `folly/lang/test/` are in the cmake build. For disambiguation, prefix them all with `lang_`.

Reviewed By: Orvid

Differential Revision: D26496837

fbshipit-source-id: 185a7990c2c7f535123229a07436e901dca6ae7f

Summary: This returns a char* so correct return is nullptr, not 0.

Reviewed By: usikder

Differential Revision: D26122982

fbshipit-source-id: 8c62520403fce966f83939be7cc03f6dc6be4aee

Summary: Cut log lines in `folly::uncaught_exceptions` test cases. Having log lines is helpful when debugging test failures but we can always add them in when necessary. This makes running the test binary directly less noisy, and running test binaries directly is an important case not to be overlooked.

Reviewed By: markisaa

Differential Revision: D26504200

fbshipit-source-id: 00e06e1396b9ccc9cdd739ace1007726ebaa3d88

Summary: A show-build-dir subcommand. Possibly useful for building a project and then running only one test or benchmark binary directly.

Reviewed By: wez

Differential Revision: D26502869

fbshipit-source-id: 0d8f6c42a2bbeb2440503a39c7fc770e3b3e4fff

Summary:
Cut `std::hash` specialization in folly for `signed __int128` and `unsigned __int128`.

There are cases where folly does polyfill things in the global and standard namespaces, but in order for folly to play nicely with other libraries this practice is overall to be avoided.

Reviewed By: nlutsenko

Differential Revision: D26455137

fbshipit-source-id: 948140513b8daf6fe777d04ea42346d69c5eb03f

Summary: Avoid the use of fancy macros in the `folly::enumerate` test suite in order to facilitate cmake's gtest integration.

Reviewed By: Orvid

Differential Revision: D26477530

fbshipit-source-id: 1838709e76016c389b052a9523a0681c58b8af96

Summary: Cut the `EventBaseLocal::emplace` overload taking a pointer since it is unused and to consolidate on the approach of not letting internals leak.

Differential Revision: D26246689

fbshipit-source-id: 0d9dc1bfcc3d37dc980142b221ee4443b98205a3

Summary: Use the global immutable executor by default and remove the default entirely for the deprecated form.

Reviewed By: yfeldblum

Differential Revision: D26414638

fbshipit-source-id: b48fe4683165e7f29e8003560f2917e143138bb0

Summary: Let `File` tests not use `/etc/hosts` since that file is not portable across all systems. Likewise the fs-util tests using `/usr/lib` and `/usr/bin`.

Reviewed By: chadaustin

Differential Revision: D26447117

fbshipit-source-id: 669a3d7e0ea4efd54ca2efd5c15d8a21227b5c8c

Summary:
[Folly] Let some utility functions be invocable objects: `to_signed`, `to_unsigned`, `to_narrow`, `to_underlying`.

Additionally, force the template type param to be deduced.

Reviewed By: markisaa

Differential Revision: D21959729

fbshipit-source-id: eedd9f2f84efb62c99ed0d5f65123a7fe000cf0a

Summary:
Currently there is logic that keeps histograms which only have one value reported to it separately.

The multi level histogram keeps the histogram for several time buckets. Just in case we had only one value added, it will keep reporting the value even if it was reported long ago and shouldn't appear in the time window level we are querying.

This is inconsistent with non histogram metrics (`avg` for example) reported from the same histogram, which don't have this logic.

A scenario would look like this:
1. Report value 5 to histogram
2. Immediately query the 60 second level -> `avg` reports 5, `p50` reports 5.
3. Wait 2 minutes
4. look at the 60 second level -> `avg` reports 0 (no value in the last 60 seconds) but `p50` keeps reporting 5.

I think this does more harm than good, so I suggest to kill this behavior.

Reviewed By: simpkins

Differential Revision: D26339016

fbshipit-source-id: 120485f8b78876e60ce66a534edcf86e7d9a836d

Summary: [folly] no `shared_ptr` storage in `EventBaseLocal` since its refcount operations are unnecessary. Pare it down to `unique_ptr` with a straightforward fun-ptr deleter.

Reviewed By: iahs

Differential Revision: D26246619

fbshipit-source-id: 3d0214ccb6c4730ca7b573065b4468a0dce85d40

Summary:
Introduce `folly::detail::thunk`, a carefully curated collection of generic general-purpose thunk templates: `make`, `ruin`, `ctor`, `dtor`.

Initial uses in `StaticSingletonManager` and `to_erased_unique_ptr`.

Reviewed By: vitaut

Differential Revision: D26417824

fbshipit-source-id: 482f4154a957b3c3dbeede726ed870a8d10c2a32