Summary: A macro which expands to `constexpr` under C++17. Can be used with `if` and lambdas in cases where `constexpr` is an optional hint but not necessary for the program to compile.

Reviewed By: Mizuchi

Differential Revision: D32607012

fbshipit-source-id: 56a6d8679ab2add4f88c89642166f1ed4b956089

Summary:
Fixes this warning:

```
folly\experimental\bser\Load.cpp(109) : warning C4866: compiler may not enforce left-to-right evaluation order for call to 'folly::dynamic::operator[]'
folly\experimental\bser\Load.cpp(131) : warning C4866: compiler may not enforce left-to-right evaluation order for call to 'folly::dynamic::operator[]'
folly\experimental\bser\Load.cpp(136) : warning C4866: compiler may not enforce left-to-right evaluation order for call to 'folly::dynamic::operator[]'
```

Reviewed By: luciang

Differential Revision: D31320782

fbshipit-source-id: 9e42176436d7ebf22af38b0589ccdc75e020b771

Reviewed By: Gownta

Differential Revision: D31824054

fbshipit-source-id: 101f8daa3018e89c1857d4d2980e97bc8487ca21

Reviewed By: yfeldblum

Differential Revision: D32364716

fbshipit-source-id: f36356d5818adebe5bbbe219044c81282ab008a6

Summary: I found this useful to see where manifests resolve to when they are already built

Reviewed By: HarveyHunt

Differential Revision: D32644308

fbshipit-source-id: b796cb67f154177fbac1093290d97fe5aab6b20c

Summary: Fix FLAKE8 lint about redefintion of 'getdeps' variable

Reviewed By: HarveyHunt

Differential Revision: D32644576

fbshipit-source-id: 9c3b4ef54d2278238c3dc88a4969e34e24976a3d

Summary: This fixes some missing cert errors when running eden_scm tests against our own build of openssl on macOS

Reviewed By: HarveyHunt

Differential Revision: D32617808

fbshipit-source-id: efc34341c2c9b578f9c1c92e0678dfb16ef9112e

Summary: System openssl is preferred on Linux

Reviewed By: HarveyHunt

Differential Revision: D32617807

fbshipit-source-id: 30913858b7f4172cea3d819a63d57563b3da64aa

Summary: I don't think the spaces were breaking anything, but many years on unix means they set my spidey sense tingling when looking at the build logs.

Reviewed By: StanislavGlebik

Differential Revision: D32619583

fbshipit-source-id: 8d5bc35f085faced20457645f1c1430371a3c578

Summary: Just replace it with `__GLIBCXX__`.

Reviewed By: andrewjcg

Differential Revision: D32624136

fbshipit-source-id: fa3ae4b4e7c3b6c05793a25cc99a93a0d0c18c7f

Summary: A lambda-expression parallel to `FOLLY_CREATE_MEMBER_INVOKER_SUITE`.

Reviewed By: Gownta

Differential Revision: D32601861

fbshipit-source-id: 8bb5876d800215346b19c42090a1cc13b6aa9042

Summary: In generic algorithms parameterized by a mutex type, it may be the case that a shared lock is desired if the mutex is a shared mutex and a unique lock is desired otherwise. This allows a wider range of mutex type arguments rather than just permitting shared mutex types. A hybrid lock may be used with read-only access to data; when the mutex type is shared, the lock would be optimized to a shared lock, but when the mutex type is non-shared, the lock would fall back to a unique lock. This may be helpful since writes may dominate reads in some cases and unique locks on non-shared mutex types may be faster than unique locks on shared mutex types.

Reviewed By: Gownta

Differential Revision: D29624498

fbshipit-source-id: 9caaf9c413fd6ce7ea318906362c3c4330f8d343

Summary: Lets make this faster

Reviewed By: Croohand

Differential Revision: D32614135

fbshipit-source-id: 2285bdb89c2ad982667261800f327f851a6cfcec

Summary: Make it faster, the build can run in parallel.  Unfortunately install can't but its pretty quick anyway.

Reviewed By: Croohand

Differential Revision: D32608049

fbshipit-source-id: 6c86184993a065e29f95df658f1b50ba563a5b14

Summary: fix a lint, platform variable was declared twice

Reviewed By: Croohand

Differential Revision: D32605614

fbshipit-source-id: 8e43de8689bf30410273355444db9c3d94663d43

Summary: The stdlibs export ways to detect which are in use. Cut the unnecessary preprocessor names for detecting/overriding.

Differential Revision: D32515501

fbshipit-source-id: 2bc85cda30ebbdfa0163e3fe287aceb8df923303

Summary: The project as moved out of github facebookincubator org to facebook org

Reviewed By: StanislavGlebik

Differential Revision: D32593002

fbshipit-source-id: 4ea29dc63fa60e9a9a4f169ea65f7fdca6333005

Summary:
Most referenced repos have moved from master to main as default branch, so flip the default in getdeps.

As well as tidying things up, this means more manifests will be able to use the pinned git commit hash for a dependency that shipit generates (e.g. build/deps/github_hashes/facebook/folly-rev.txt). This is because a "rev = " setting in the manifest is treated as a dynamic override in GitFetcher.__init__ and this diff reduces the number of such overrides.

Reviewed By: StanislavGlebik

Differential Revision: D32567564

fbshipit-source-id: 3f1b734eb1bb0f5dbafb01ceb935a3d51b8dcc9a

Reviewed By: capickett

Differential Revision: D32375291

fbshipit-source-id: 4e88bd4b0caae41c84ef7c249b3108bed9afa80a

Summary: Provies single-await co_nothrow wrapper

Reviewed By: capickett

Differential Revision: D32470528

fbshipit-source-id: 30434b133e282f1015f97025c448bb88a1701e7a

Summary: Other template classes, as well as the docstring, use `Ex` to refer to the exception class.

Differential Revision: D32192455

fbshipit-source-id: 664db8beee0850ac3fb8e3cfcd46a28d568cb808

Summary: Enable auto-reserve for operator=(std::initializer_list).

Reviewed By: yfeldblum, shixiao

Differential Revision: D32233038

fbshipit-source-id: ae16a5508dcae5957ea44404ac55d489a14937af

Summary: libffi is needed for getdeps python 3.8 update

Reviewed By: krallin

Differential Revision: D32459310

fbshipit-source-id: 6515eed088fb6de0091c2348b5732d1b635113e0

Summary:
ftp.pcre.org is dead. We are currently migrating from PCRE1 to
PCRE2. In the meantime, download from SourceForge instead like we do
with Boost.

Reviewed By: akushner, xavierd

Differential Revision: D32520283

fbshipit-source-id: 9fda6930d7d8b677786a43419c4c0dc6289305f1

Summary:
In the vast majority of cases in fbcode, the sanitizer macros are checked with
`#ifdef`, so do the same in some places to fix `-Wundef`.

Reviewed By: luciang

Differential Revision: D32501662

fbshipit-source-id: 123e22d78476c9db0e328ccb01a734a06a163594

Summary:
Users may set `FOLLY_USE_LIBCPP` or `FOLLY_USE_LIBSTDCPP` to `0` or
`1`, so make sure everything checks it via `#if`.

Reviewed By: luciang

Differential Revision: D32496561

fbshipit-source-id: 5eee660b540af0bf1eaee4949576acf11c9be8d0

Summary: Cast the result of shifts to the integer type parameter, rather than the shift width.

Reviewed By: aary, luciang

Differential Revision: D32160950

fbshipit-source-id: 0100a1a92c48bfa1cd957cf42ed84d01302ea4f7

Summary: Previously update() could be run both directly from within the update notification callback (that can happen in any context while holding some application locks), but also while observer is initially created from the observable. This change moves the update logic to be called on the observer internal thread, making the implementation even more resilient to various locks that may be held by the application.

Reviewed By: yfeldblum

Differential Revision: D32338088

fbshipit-source-id: 557f47c98469a951ce4b5513ce96e2b3a5d8ba6b

Reviewed By: igorsugak

Differential Revision: D32415926

fbshipit-source-id: b62ac87215800eed8e6cf8acf92f0518b9a56da5

Reviewed By: ot

Differential Revision: D31763384

fbshipit-source-id: ef666193f83a16d4eedf65a499361d967809163f

Differential Revision:
D32405920 (https://github.com/facebook/folly/commit/6b58b9e81875d92ba53add248d113593b24d2c8b)

Original commit changeset: b0b5c55149ae

fbshipit-source-id: f5a6d0dd6bb4434cebe02b5cde357d94e28253f0

Summary: Provies single-await co_nothrow wrapper

Reviewed By: capickett

Differential Revision: D32405920

fbshipit-source-id: b0b5c55149aebe4246422fabeffb7ed433b4e20d

Summary: Have constructor do init() instead. I can't think of any valid reason to have this API other than confusing everyone who decides to use it.

Reviewed By: praihan

Differential Revision: D32302228

fbshipit-source-id: 136e0d2919291acd60be953337309cd006bd674b

Summary: Now we'll ignore all the known sanitizers: ASAN, TSAN, MSAN, UBSAN.

Reviewed By: yfeldblum, jdonald

Differential Revision: D32364717

fbshipit-source-id: f71a294dd9ebaa8521f0487ebc65c6f7c1e7bf04

Summary:
Inlining `getStackTraceInPlace` fails on Fedora with

```
/builddir/build/BUILD/folly-2020.12.21.00/folly/experimental/symbolizer/StackTrace.cpp: In function 'folly::symbolizer::(anonymous namespace)::getStackTraceInPlace(ucontext_t&, unw_cursor&, unsigned long*, unsigned long)':
/builddir/build/BUILD/folly-2020.12.21.00/folly/experimental/symbolizer/StackTrace.cpp:88:9: error: function 'folly::symbolizer::(anonymous namespace)::getStackTraceInPlace(ucontext_t&, unw_cursor&, unsigned long*, unsigned long)' can never be inlined because it uses setjmp
   88 | ssize_t getStackTraceInPlace(
      |         ^~~~~~~~~~~~~~~~~~~~
```

Reviewed By: yfeldblum

Differential Revision: D29639503

fbshipit-source-id: 823692d95171d5fb3968761c00b4cc5650db171b

Differential Revision: D32394449

fbshipit-source-id: 2c2bc54c2d71cc677c35195adc73f579b5d0c101

Summary: exception_wrapper no longer rethrows during this construction

Reviewed By: yfeldblum

Differential Revision: D32371738

fbshipit-source-id: 0d5d51cdde4115aaf8774950e53bfac0b37f0b88

Summary: Breaks rescheduling on error

Differential Revision: D32398162

fbshipit-source-id: 582db297e0b700617c2e455e1f6d2fd1fa40e143

Summary:
- For Windows in xplat we use [Clang9/12 + MSVC 2017](https://www.internalfb.com/code/search?q=filepath%3Afbsource%2Ftools%2Fbuckconfigs%2Fcxx%2Fwindows%20repo%3Afbsource%20vs2017_15.9) and it's [<experimental/coroutine>](https://www.internalfb.com/phabricator/paste/view/P467028969)
- When upgrading to MSVC 2019 we also get [<coroutine>](https://www.internalfb.com/phabricator/paste/view/P467029007) in addition to  [<experimental/coroutine>](https://www.internalfb.com/phabricator/paste/view/P467029069)
- The MSVC2019 ```<coroutine>``` does not work with our current Windows [coroutine solution](https://fb.workplace.com/groups/rp.co.await/permalink/748274059391415/) / [D26877884](https://www.internalfb.com/diff/D26877884)
- Hence I am *re-using* an existing flag to opt-out of ```<coroutine>``` as MSVC 2019 left for backwards compatibility also ```<experimental/coroutine>```

Reviewed By: yfeldblum

Differential Revision: D32282445

fbshipit-source-id: d2eeb3057518e95135cf054ab6156dac5aa15065

Summary: Provies single-await co_nothrow wrapper

Reviewed By: capickett

Differential Revision: D31450124

fbshipit-source-id: e8d18c49248d85ef864abad2eecffe69de58a546