Summary:
MSVC is being grumpy, and I want to continue to work from the preview build, so commit the workaround, as there's no significant difference.
Upstream bug report: https://developercommunity.visualstudio.com/content/problem/59614/compiler-crash-when-constexpr-constructing-stdchro.html

Reviewed By: yfeldblum

Differential Revision: D5099876

fbshipit-source-id: 64d5573d78b14339ff3177dd910a22787463ccd2

Summary: `std::hash` lives in `<functional>`, not `<xstddef>`.

Reviewed By: yfeldblum

Differential Revision: D5097468

fbshipit-source-id: d0684491d1d4b0f83f07ad837a66a915ce2ec8a6

Summary: 4.0 has been out for three months now, so it's pretty safe to remove them.

Reviewed By: Orvid, yfeldblum, mzlee

Differential Revision: D5096007

fbshipit-source-id: 595c3e86cd7cf1a1706f27f107fb0af8ab89a676

Summary: Use SafeAssert instead of assert.

Reviewed By: nbronson

Differential Revision: D5085575

fbshipit-source-id: daeff427b9b1fc5dff6ea986d16a70364acd2dd7

Summary: Name all repeating function threads for ease of debugging.

Reviewed By: yfeldblum

Differential Revision: D5065281

fbshipit-source-id: e875e654dfa644a265e44416baf5fbf23c9da434

Summary:
Previously we defined an assignment from std::string on all basic_fbstring
specialisations, but we don't actually want to do that because it's nonsense to
construct a basic_fbstring<char16_t> from an std::string. Equally it's not
nonsense to construct one of those from an std::u16string but the previous code
didn't allow it.

We now permit basic_fbstring<C, T, A1, S> to be constructed or assigned-to from
std::basic_string<C, T, A2>. The character type and traits must match but the
allocator is permitted to vary.

Background on my determination that the allocator type was unimportant and
could be disregarded: In part this is because C++17 made the same choice for
basic_string_view. Another factor was C++17's std::pmr::string (it's a
std::string with a different allocator) which I thought should be convertible
to fbstring in the same way as std::string.

Reviewed By: Gownta

Differential Revision: D5060569

fbshipit-source-id: f8984c528b76356240970c67916c58995d3f228d

Summary: It is pretty confusing to inherit from classes that manage threads. See the docblocks in this diff.

Reviewed By: yfeldblum

Differential Revision: D4973498

fbshipit-source-id: 2fcf1ddf68ef46d4d78a9b40f304262064862715

Summary:
folly/detail/ChecksumDetail.h gets included in Checksum.h and it
unconditionally includes <immintrin.h>. This doesn't compile on
aarch64 platform. Add #ifdefs for this.

Reviewed By: yfeldblum

Differential Revision: D5048636

fbshipit-source-id: d2074eb1b01487b02d95f3e2eebe683237d918fe

Summary: [Folly] Fix violations of `unused-lambda-capture`.

Reviewed By: Orvid

Differential Revision: D5060391

fbshipit-source-id: 34aabc847719603d13da8f2b52a7ec187d803a4a

Summary: It's *almost* dead. This switches things to explicitly reference `std::make_unique` so that `folly::make_unique` can be marked as deprecated until mobile catches up and it can be killed completely.

Reviewed By: yfeldblum

Differential Revision: D5026584

fbshipit-source-id: aefc8cb3de84583fd3722fdb9dfea620884590c5

Summary:
[Folly] Drop support for deprecated associative containers.

Namely, `__gnu_cxx::hash_set` and `__gnu_cxx::hash_map`.

Reviewed By: wqfish

Differential Revision: D5058813

fbshipit-source-id: ebbcf10765f5d06776ee8f697cfb78614a3a566c

Summary:
This diff adds StampedPtr, which packs a pointer and a uint16_t into
a uint64_t with maximum portability and without adding any additional
functionality.

Reviewed By: yfeldblum, davidtgoldblatt

Differential Revision: D4804614

fbshipit-source-id: 25fe7aff47d1e126ac8edfff4eb0bbb1d34071aa

Summary: AsyncSocket::handleErrMessages() should check if the error message callback is still installing before calling it, since the callback could be uninstaled on the previous loop iteration.

Reviewed By: yfeldblum

Differential Revision: D5051001

fbshipit-source-id: fc01932c0d36bd8f72bf1905f12211fb83d28674

Summary:
[Folly] List the new GCC 4.9 and C++14 minimum requirement.

We no longer support GCC 4.8 or C++11.

Closes #590.

Reviewed By: Orvid, mzlee

Differential Revision: D5058942

fbshipit-source-id: 0545d1bb294494e5ef5f17a40c9cf3ac688bd8d0

Summary:
MSVC doesn't support `^` and `&` operator for __m128i type
Closes https://github.com/facebook/folly/pull/594

Reviewed By: yfeldblum, Orvid

Differential Revision: D5053356

Pulled By: djwatson

fbshipit-source-id: f789824052e0c679c265c83ad704109805c21402

Summary:
Problems:
- The vDSO check code in configure.ac is broken, and will always fail (uses AC_LANG_PROGRAM but with arguments in the AC_LANG_SOURCE style)
- On Linux, using dlopen/dlsym requires -ldl (libdl) during the link phase. This check was missing and this argument was not added to the linker arguments.
- On a Linux system without vDSO support, libfolly.so still uses vDSO in ClockGettimeWrappers.cpp

Solution:
- Switched to AC_LANG_SOURCE
- Required libdl to exist when build target is Linux. This also adds this dependency to libfolly.la, resulting in fixing a dependency issue for Proxygen (recent Proxygen build would have issues in building examples due to failing linking step due to missing dlopen / dlsym / dlclose symbols)
- In ClockGettimeWrappers.cpp, checking if `__linux__` is set is not sufficient to determine that the system has vDSO support. The autoconf script already exposes a correct check: FOLLY_HAVE_LINUX_VDSO (this is already used in folly/detail/CacheLocality.cpp), so switched to that one.
Closes https://github.com/facebook/folly/pull/592

Reviewed By: yfeldblum

Differential Revision: D5049816

Pulled By: Orvid

fbshipit-source-id: 58b2ed4c4101274505c61b4825accf262c0d56ef

Summary:
Return not just number of cancelled ops, but all of them as well.
Test was incorrectly assuming `wait(1)` will return exactly one operation, fix
that as well.

Reviewed By: ot

Differential Revision: D5054684

fbshipit-source-id: 1c53c3f7ba855d1fcfeac8b1b27f90f0872d2c21

Summary:
[Folly] `exception_wrapper::get_object<>`.

Returns a pointer to the stored object, if the template type parameter is of the right sort.

Reviewed By: jsedgwick

Differential Revision: D5000720

fbshipit-source-id: 2869439085e8dfb56e6cb439794b03876b7d715c

Summary: This diff shows an issue in `folly::retrying`. When the future generation function throws an exception and `folly::retrying` is nested in another functor that returns Future, it will throw `broken promise` instead of the actual exception message, which can be very generic and confusing. Fix is to capture the exception so that exact error message can be propagated up.

Reviewed By: yfeldblum

Differential Revision: D5050690

fbshipit-source-id: 5b9b24977788f60aa778bb8e9cdf4281ea9a0023

Summary: To satisfy internal linter

Reviewed By: yfeldblum

Differential Revision: D4957870

fbshipit-source-id: 191ac768790fbd8cc8a4d24036c016644ff1d125

Summary: changes as suggested by FB-internal linter

Reviewed By: yfeldblum

Differential Revision: D4957742

fbshipit-source-id: c9d94c477d24f153cab0d25edccfd39ff31fdfdf

Summary: suggested by internal linter

Reviewed By: Orvid

Differential Revision: D4958232

fbshipit-source-id: 69c67d80be092db17703d672524124ca5ef7ba32

Summary: Before this change, when a non-const FunctionRef lvalue is copied, it is treated as any other callable: it is wrapped with an indirection. That's semantically incorrect and potentially creates lifetime problems. Instead, use the compiler generated copy constructor, which only copies the object and function pointers.

Reviewed By: yfeldblum

Differential Revision: D5040843

fbshipit-source-id: f691060bdced2e287ba22d22b961c02c2b924147

Summary: Instead of using `UNKNWON_UNCOMPRESSED_LENGTH` use an `Optional`.

Reviewed By: yfeldblum

Differential Revision: D5038919

fbshipit-source-id: 7fb60542277019996be3ff50509df5a5060cb1a0

Summary:
We would like to use `folly/Optional` in settings where exceptions
are disabled. An example is ObjC++ codebases where supporting exceptions
doesn't quite help (since objc_msgSend() can throw) and yet we need to pay the
additional binary size cost for the unwind tables.

This patch makes a small change to outline the "assert" utility included
inside Optional.h

Reviewed By: yfeldblum, mzlee

Differential Revision: D5030172

fbshipit-source-id: 7def3c6eda22c41c8cab2037444978e0a4c50abf

Summary:
It should be implemented with `io_cancel`, but it is not
supported (D682836), so still have to drain events, ignoring only
op callbacks.

Reviewed By: luciang, ot

Differential Revision: D5044020

fbshipit-source-id: 0bcd04c91a437fccaf2189ccf771a1cb61c68942

Summary:
This diff fixes a race that happens on destruction of `ScopedEventBaseThread`.

```
Thread1: ~ScopedEventBaseThread()
Thread1: eb_.terminateLoopSoon() <- preempted just after stop_ = true
Thread2: eb->loopForever() in run(...) exits because stop_ is true
Thread2: ...
Thread2: eb->~EventBase()
Thread1: queue_->putMessage(nullptr) <- accesses destroyed EventBase
```

Reviewed By: yfeldblum

Differential Revision: D5042654

fbshipit-source-id: 95515ed7cde09ff5f125ef121bea86ab3907f98a

Summary:
[Folly] `hasher` instances for 8-bit and 16-bit integral types.

Allowing the use of `Hash` with such types.

They are not necessarily the ideal algorithms for those widths, essentially forwarding to the 32-bit instances.

Reviewed By: luciang

Differential Revision: D5043094

fbshipit-source-id: 6ef96dfc8d1baf0a15b9bdd585b7c7672099e4f0

Summary:
This is useful for checking if it's possible to still write to a transport,
even if its read side is closed (for transports that support half shutdown,
like AsyncSocket). Default implementation just returns true for now (up
to implementers to override).

Reviewed By: yfeldblum

Differential Revision: D4982649

fbshipit-source-id: 0a9a2e2b745ea3db57e9f151f3a8634e1bda2465

Summary: [folly] add missing const to fix `folly::toDynamic` on `std::vector<bool>`

Reviewed By: ender-wieczorek, yfeldblum

Differential Revision: D5039403

fbshipit-source-id: edd052c7d1d832d424166cba15fcd9f4f8bd219c

Summary:
I was looking for a way to get rusage of a particular pid because
getrusage isn't good enough since it records the rusage of all the children
that has been terminated (and waited for). Even though wait4 is marked as
deprecated, wait3 (the cousin of wait4) is still being used in places like
time. Furthermore, there is no suitable replacement to get rusage with wait*.

Reviewed By: yfeldblum

Differential Revision: D5008084

fbshipit-source-id: 6e511ebec7464d21309e5112aca95083e9307ea1

Summary: This reverts commit 71134c1657bdd4c38c12d8ca17f8335ef4c27352

Differential Revision: D4982969

fbshipit-source-id: fc1e766a5fd03fbd02c345904c3c6587013f38d5

Summary: Closes https://github.com/facebook/folly/pull/588

Reviewed By: ericniebler

Differential Revision: D5029876

Pulled By: yfeldblum

fbshipit-source-id: 6a8f16373dcfb1c7b2741eb808da0f6dbc4207b6

Add folly::Identity function object to Utility.h; replace AtomicHashArray's AHAIdentity and folly/gen's Identity with it

Summary: Code duplication is bad.

Reviewed By: yfeldblum

Differential Revision: D5011806

fbshipit-source-id: cab7bb3af1c934a5a63cd3fb98aa33f2578aebfb

Summary: Closes https://github.com/facebook/folly/pull/587

Reviewed By: yfeldblum

Differential Revision: D5022071

Pulled By: Orvid

fbshipit-source-id: 2506087de76ba4544bf68a330bc2a18977c65f28

Summary:
Code may pass a callback which captures an object with a destructor which mutates through a stored reference, triggering heap-use-after-free or stack-use-after-scope.

```lang=c++
void performDataRace() {
  auto number = std::make_unique<int>(0);
  auto guard = folly::makeGuard([&number] { *number = 1; });
  folly::via(getSomeExecutor(), [guard = std::move(guard)]() mutable {}).wait();
  // data race - we may wake and destruct number before guard is destructed on the
  // executor thread, which is both stack-use-after-scope and heap-use-after-free!
}
```

We can avoid this condition by always destructing the provided functor before setting any result on the promise.

Reviewed By: spacedentist

Differential Revision: D4982969

fbshipit-source-id: 71134c1657bdd4c38c12d8ca17f8335ef4c27352

Summary:
C++ up to and including C++17 lacks an alternative to std::back_inserter() that uses emplace_back() instead of push_back(). This causes unnecessary temporary objects in some cases, when using std::back_inserter() together with STL functions such as std::copy() or std::transform(). The same holds for std::front_inserter() and std::inserter().
This diff introduces folly::back_emplacer(), folly::front_emplacer(), folly::emplacer(), and related iterator classes, which call emplace_back(), emplace_front(), and emplace() respectively, with perfect forwarding of any arguments to the output iterator's operator=.
Includes support for variadic emplacement / multi-argument constructors through a utility function folly::make_emplace_args() which packs its arguments into a special tuple for use with operator=.

Reviewed By: ericniebler

Differential Revision: D4897174

fbshipit-source-id: c85c30c457e0c946938051819baa662d1a0b8ca1

Summary: There are still some upstream references to `folly::make_unique` that need to be removed before it can be full killed, but this gets it most of the way there.

Reviewed By: yfeldblum

Differential Revision: D5024310

fbshipit-source-id: 6cfe8ea93662be18bb55588c8200dec72946e205

Summary:
Change every instance of EXPECT_EQ(false, ... to the simpler/shorter EXPECT_FALSE(...
Likewise, convert each EXPECT_EQ(true, ... to EXPECT_TRUE(...

Differential Revision: D5019004

fbshipit-source-id: 0203f10fa47237f869a75a057ac4456ef03e1f53

Summary:
There's nothing io/async/ssl-specific in this file. Moving to the
top-level directory will help this be more discoverable. Part of general cleanup
for io/async/ssl

Reviewed By: yfeldblum

Differential Revision: D5005566

fbshipit-source-id: 66a05a2139ee80a6d63791d1851da3f1858e8abf