Summary:
[Folly] Rename `exception_wrapper::get_object` to `get_exception`.

This will be a template overload of the existing non-template member `get_exception`, but it should just work.

Reviewed By: spacedentist

Differential Revision: D5180845

fbshipit-source-id: 28e16e039ec6a7939b38f217b4ad5c6bc803f515

Summary:
- Fix TimePoint to use steady_clock rather than system_clock
- Use nanoseconds instead of milliseconds in most locations

This code should probably also be moved into a folly::testing namespace or
something.  This class is pretty specific to unit tests, and `folly::TimePoint`
seems like too generic of a name for it.  However, just to keep things simple
I'm not doing that as part of this diff yet.

Reviewed By: yfeldblum

Differential Revision: D5175630

fbshipit-source-id: 26490fc7ff1b25fb86f09309e81108828cd0f091

Summary:
Use the newly introduced getOSThreadID() function to get a thread ID for
determining thread scheduling information on Linux.

Reviewed By: yfeldblum

Differential Revision: D5173596

fbshipit-source-id: 3e6fa352c3774986b0ac1f93bd6c7e4a29e08471

Summary:
Some of the code in TimeUtil.cpp computes how long the current thread has spent
waiting to be schedule on the CPU, so we can discount this time when testing
timeout behavior.

It appears that this code has been broken for a fairly long time.  Older Linux
kernels reported values in /proc/<pid>/schedstat using jiffies.  However, it
appears that this was changed in Linux 2.6.23 to report values using
nanoseconds.  (It looks to me like this was changed in commit 425e0968a25f,
which purports to simply be moving code from sched.c to sched_stats.h,
but it appears to also have also changed this behavior.)

This updates TimeUtil.cpp to compute the value correctly in modern Linux
kernels.

Reviewed By: yfeldblum

Differential Revision: D5173598

fbshipit-source-id: 98436d3a687400bf68661156ffce93eea7232632

Summary:
Adds a core-local allocator to CacheLocality.  Multiple objects using
cache locality may share the same allocator, and allocate things less than
cacheline sized, without incurring additional false-sharing overhead.

Reviewed By: nbronson, ot

Differential Revision: D5139886

fbshipit-source-id: a9804662d6339829a12e0791f418dabd9678f1bf

Summary:
`kDecayCmd` was guarded such that it wasn't being defined at all if JEMalloc wasn't available.

Closes https://github.com/facebook/folly/issues/608

Reviewed By: interwq

Differential Revision: D5193721

fbshipit-source-id: 1a2666de70e90eac1e9f2e130d0452b01b3239fa

Summary: This diff adds a Traits template parameter to IndexedMemPool that allows more control over the lifetime management of individual elements, including mixes of lazy and eager recycle semantics (or colocation of different classes of data inside a single element). It also arranges that an index is not reported as isAllocated() until it has been passed to Traits::initialize and passed to Traits::onAllocate at least once, so code that is traversing valid indexes doesn't need to deal with the post-initialize but pre-onAllocate state (it must still deal with indexes that reported isAllocated() as true but have since been passed to onRecycle). The default behavior is unchanged.

Reviewed By: nbronson

Differential Revision: D5177462

fbshipit-source-id: e7d22c860ab6bf25083977dfb5a63955641c9cfb

Summary: MemoryMapping doesn't use fbstring directly at all, so this include isn't needed.

Reviewed By: yfeldblum

Differential Revision: D5188209

fbshipit-source-id: d86b876a96343c830295bea1162580215a340815

Summary:
The syscall() function is defined in <unistd.h>
<sys/syscall.h> apparently only defines IDs to be used with syscall(), but does
not define the syscall() function itself.

This caused build failures for files that included ThreadId.h before unistd.h

Reviewed By: Orvid

Differential Revision: D5189658

fbshipit-source-id: 2ec8ea1d58f3fc14cf458a53ecaa811978527398

Summary:
This diff adds helper functions that can resize std::string or std::vector
without constructing or initializing new elements.  They are designed
for retroactively optimizing code where touching every element twice
(or touching never-used elements once) shows up in profiling, and where
restructuring the code to use fixed-length arrays or IOBuf-s would
be difficult.

Implementations are provided for 5 string implementations (pre-c++11
libstdc++, libstdc++ with SSO, libc++, std::basic_fbstring, and MSVC)
and 3 vector implementations (libstdc++, libc++, and MSVC).  On an
unsupported platform you will hopefully get a #warn if you include
UninitializedMemoryHacks.h followed by a linker error if you actually
use it.

Reviewed By: yfeldblum

Differential Revision: D5102679

fbshipit-source-id: 536c00eabae4cdb8a0affe3e919a372f4dc51ac5

Summary: Update decay time API to be jemalloc 4 & 5 compatible.

Reviewed By: yfeldblum

Differential Revision: D5188574

fbshipit-source-id: 8e3c26c8b6431efdd0ec7ff492a065bddb816b4b

Summary:
Add a getOSThreadID() call.  This is similar to getCurrentThreadID(), but
returns the OS-level thread ID.

Reviewed By: yfeldblum

Differential Revision: D5173627

fbshipit-source-id: 0e8695ecfc1e382d12526c1b7d1717be114c9f4a

Summary:
These builtins are available on all platforms under GCC, using the instruction directly when available and a fallback implementation otherwise.
They are implemented in the builtins portability header for MSVC.

Reviewed By: yfeldblum

Differential Revision: D5185106

fbshipit-source-id: a58305a6b99eb49bd165876a4a60c512a259b225

Summary: This makes the name of the header match the source file.

Reviewed By: yfeldblum

Differential Revision: D5186193

fbshipit-source-id: b1f9041fb730eacb91ad167e500c25df8f8ba947

Summary:
[Folly] Let map-related functions be templated over key types.

This supports the case where map members like `find` may be overloaded or templated on types other than the map's `key_type const&`.

In C++14, standard library map types gain template overloads for `find` and for other members, permitting lookups without constructing `key_type` instances. This is useful primarily when `key_type` is expensive but another object type comparable with `key_type` is inexpensive. As a common example, a `key_type` of `std::string` is expensive in the general case because it allocates storage on the heap but `std::string_view` (C++17), when constructed with non-allocated `char const*, std::size_t`, would be inexpensive.

Reviewed By: terrelln

Differential Revision: D5145879

fbshipit-source-id: 979b75bfe55661aab11d5302da1bcd7830abd5af

Summary:
The docs give `ThreadLocalPRNG rng = Random::threadLocalPRNG()` as an example
of creating a thread local PRNG, but `Random::threadLocalPRNG()` does not/no longer
exist. I think it's just `folly::ThreadLocalPRNG` right now.

Reviewed By: yfeldblum

Differential Revision: D5184992

fbshipit-source-id: 63a9ef62b32fca42088abec419ae53531910cc82

Summary: Destroy created arena which has extent_hooks linked.

Reviewed By: jasone

Differential Revision: D5177535

fbshipit-source-id: 7d75f4276fc174c4d4ce1102dfb8ec8c27c1f56d

Summary: Add `count()` and `swap()` methods. Ensure that `operator==` works.

Reviewed By: yfeldblum

Differential Revision: D5169393

fbshipit-source-id: a8025f6fdf251e38b0d2f27733d18967a55c6a15

Summary: We are fully on C++14 now, so these warnings should never be firing.

Reviewed By: yfeldblum

Differential Revision: D5179124

fbshipit-source-id: 31c6ddbce5c45b60fe73990f49d65ac95d17fe87

Summary: Do this by moving the two helpers that need to refer to them into `folly/futures/helpers.h`.

Reviewed By: yfeldblum

Differential Revision: D5179109

fbshipit-source-id: bdb319ff3432d3629a955c1390dc8bf6f27f4ce6

Summary: It's deprecated, so use the non-deprecated form instead.

Reviewed By: yfeldblum

Differential Revision: D5179133

fbshipit-source-id: 91440bc3768ee68d2aada2299fbfbcdd852f946c

Summary:
[Folly] Apply `clang-format` to `folly/gen/` (partial: namespace).

With some manual rearrangement in the places where `clang-format` does awkward things, with the result that clang-format over `folly/gen/` becomes a no-op.

Reviewed By: Orvid

Differential Revision: D5177428

fbshipit-source-id: 17f51d00454a7be7f29dcf1a2ff3d0eaf1de72ab

Summary:
[Folly] Apply `clang-format` to `folly/portability/`.

With some manual rearrangement in the places where `clang-format` does awkward things, with the result that `clang-format` over `folly/portability/` becomes a no-op.

Reviewed By: igorsugak

Differential Revision: D5170107

fbshipit-source-id: ceadd96740b4877cbae947846f0e738e6aaf5ed1

Summary: Using extent_hooks mallctl to update hooks.

Reviewed By: jasone

Differential Revision: D5174623

fbshipit-source-id: 9313ee9ae55c85d973736077727e54a5825f4c3d

Hazard pointers: Optimize memory order, add bulk reclamation control, add stats, add implementation switches, add benchmarks.

Summary: Make the implementation partially performant by optimizing memory order and using asymmetric memory barrier for full fences. Also added more control for bulk reclamation implementation, stats, and quality of implementation switches.

Reviewed By: djwatson

Differential Revision: D5129614

fbshipit-source-id: c597edf711fdc8f16f80523bd8cae42c51fbe140

Summary:
jemalloc 5.0 comes replaced chunks with extents APIs. Make the API compatible
with both jemalloc 4 and 5.

Reviewed By: yfeldblum

Differential Revision: D5170925

fbshipit-source-id: ce25723975729b0b63371f89a96842a1b2e3b3cc

Summary: It is nothing but a file with the license header in it and has been since it was introduced nearly 4 years ago.

Reviewed By: yfeldblum

Differential Revision: D5163176

fbshipit-source-id: f510411cbb3d9d4c90d68c9b8d1f04d9f97fcb89

Reviewed By: yfeldblum

Differential Revision: D5105818

fbshipit-source-id: e3926a0c70a68855e0180bdd44cb0ec76e66bb94

Summary:
Add a few keywords people search for when looking for this that won't otherwise
find this file.

Add a reference to the usage notes for Singleton which are a good description
of how you should operate SingletoThreadLocal as well.

Reviewed By: nbronson

Differential Revision: D5094598

fbshipit-source-id: 9980850805e1564e5c394af713e2fa17fe8844fe

Summary:
Test output before the fix is applied:
```
folly/experimental/Bits.h:247:59: runtime error: signed integer overflow: -2147483648 - 1 cannot be represented in type 'int'
     #0 folly/experimental/Bits.h:247 folly::Bits<...>::set(int*, unsigned long, unsigned long, int)
     #1 folly/experimental/test/BitsTest.cpp:228 std::enable_if<...>::type (anonymous namespace)::testSet<...>(unsigned char*, unsigned long, unsigned long, int)
     #2 folly/experimental/test/BitsTest.cpp:263 Bits_Boundaries_Test::TestBody()
    #17 folly/experimental/test/BitsTest.cpp:381 main
```

Reviewed By: philippv

Differential Revision: D5160789

fbshipit-source-id: 43f1926d58f1a5c019d4f8794d10a7a80a5c4749

Summary: All functions in this file are defined in `folly/fibers/FiberManager-inl.h`. There are no remaining references to this file.

Reviewed By: yfeldblum

Differential Revision: D5163160

fbshipit-source-id: 2fcb782a4de78f5c067610c876d0cf98f3b69e63

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.

Retry at {D4982969}.

Reviewed By: andriigrynenko

Differential Revision: D5058750

fbshipit-source-id: 4d1d878b4889e5e6474941187f03de5fa84d3061

Summary:
The dirty hack I was using to link `folly_base` into `folly` doesn't work in newer versions of CMake :(
This refactors the makefile to not need to dirty hack by using an object library rule instead. It also makes the compiler version detection more generic.

Reviewed By: yfeldblum

Differential Revision: D5158919

fbshipit-source-id: cd052a5f58ed3d88c377c68cca07ca8497ca0c7a

Summary:
Callables that are passed as rvalues to makeFutureWith should be
executed as rvalues.
Generally callables that get captured by value should be executed
as rvalues, to allow passing e.g. folly::Partial objects that contain
move-only objects like unique_ptr or folly::Promise.
`collect` would move out of parameters passed as lvalues.

Reviewed By: fugalh

Differential Revision: D5120420

fbshipit-source-id: 1633c6b7e3fbb562f4d31e21d28c98b053de9912

Summary:
In mcrouter code, we would like a non-throwing alternative to `decodeVarint()`. There
are real, expected scenarios where only part of a serialized varint fits into a packet,
in which case mcrouter fails to decode the varint and throws.  In these scenarios,
throwing too many exceptions can lead to lock contention and degrade performance.

Reviewed By: yfeldblum

Differential Revision: D5153823

fbshipit-source-id: 138273af832903f0b04bee0bcacddd66b4274129

Summary:
Add `equals` interface to StringPiece (Range class). To support following case insensitive compare case:
```
folly::StringPiece a("hello");
if (a.equals("HELLO", folly::AsciiCaseInsensitive())) {
  // Do something.
}
```

Reviewed By: ot

Differential Revision: D5150495

fbshipit-source-id: 26816820f93959678f550768396f55293b5588cb

Summary:
[Folly] Fix `tryTo` to support conversion to enumerations.

`tryTo` should return `Expected<Tgt, ConversionCode>` instead of `Tgt`.

Reviewed By: yfeldblum

Differential Revision: D5144706

fbshipit-source-id: cd23f3cf75de7c5a26bc569f3cb47fff360f6e2a

Summary:
`#include` inside a namespace is disallowed when using clang modules. Here I
just unconditionally include them at top level, since they are available in all the
relevant platforms.

Reviewed By: yfeldblum, Orvid

Differential Revision: D5140355

fbshipit-source-id: bb87225c1d8f4ac64b90a7aff5f912c13e150e3a

Summary:
allow-large-files
Moving DestructorCheck from proxygen library to folly.

Reviewed By: djwatson

Differential Revision: D5110897

fbshipit-source-id: 02a6cf6336000e8c36484e75d2da820588baf2df

Summary: This has always been the design rule for what belongs in `folly/portability/`, but was never written down anywhere except in my head, so put it somewhere people can actually find it so I can free that space in my head for other things.

Reviewed By: yfeldblum

Differential Revision: D5140587

fbshipit-source-id: 1f09c17b7ccfff780e1825670a7ffaa75cd1b1d5