Summary:
Update all of the RequestContext tests to use a test fixture that helps ensure
they all start from a consistent state.

Otherwise tests can end up running with RequestContxt settings left over from
previous test functions, which can affect their results.

In particular, several tests leave behind data for the "test" key.  This
causes subsequent calls to `setContextData()` to not actually set new data for
this key, but to instead reset its value to null.  This would cause many tests
to segfault since they did not check if `getContextData()` returned null
before dereferencing the result.

Reviewed By: yfeldblum, A5he

Differential Revision: D9233617

fbshipit-source-id: ce7a7c738592305f01b16fec7796505ea192ede4

Summary:
- Fix the variable name passed to FIND_PACKAGE_HANDLE_STANDARD_ARGS() so that
  it matches the module name (`FindGMock.cmake`).  This makes sure that the
  failure is detected correctly if GMock is not found.
- googletest depends on pthreads, so use `find_package(Threads)` and add
  `Threads::Threads` to the list of required library dependencies.

Reviewed By: yfeldblum

Differential Revision: D9212536

fbshipit-source-id: eae6220a2dbfe777bff1ac0ee0fb4df53de16955

Summary:
Use CMake's built-in FindThreads module rather than having our own custom
FindPThread.cmake module.

Reviewed By: yfeldblum

Differential Revision: D9212535

fbshipit-source-id: 9a652c510cb310c18547d31bd8215dedd8532a4c

Summary:
Ubuntu 18.04 (and presumably other Debian-based distributions) install
dwarf.h at /usr/include/libdwarf/dwarf.h.  However other platforms like Mac
typically install dwarf.h directly inside include/ without a libdwarf
subdirectory.

Commit e66fb34c previously changed the code to look only for "dwarf.h" to
support Homebrew installations of dwarfutils on Mac, but accidentally broke
finding dwarf.h on Ubuntu in the process.  This change should hopefully work
on both platforms.

Fixes: #905

Reviewed By: yfeldblum

Differential Revision: D9212428

fbshipit-source-id: a4520a47718a2da25e597ac7350344931ba21634

Summary: [Folly] Import `Policy` members into `F14Table` to deduplicate repeated uses of `Policy::`.

Reviewed By: shixiao

Differential Revision: D9176546

fbshipit-source-id: bbd32a17cca7d38b3e5d55c1840353821f4e2ddc

Summary: Add thread cached ints benchmark

Reviewed By: yfeldblum

Differential Revision: D9212949

fbshipit-source-id: 552aab15e7421f74b5cec3ce4abd211ab3141153

Summary:
Given an exception_wrapper `ew` holding a `std::runtime_error`, the following assertion fails:

```
try {
  ew.handle();
} catch( std::runtime_error const & ) {
} catch( std::exception const & ) {
  assert(false);
}
```

Reviewed By: simpkins

Differential Revision: D9199924

fbshipit-source-id: b6f90ccf269a1b58f0dd07723451ff34cde1d529

Summary: Move the definition of the `ZSTD_STATIC_LINKING_ONLY` and `ZDICT_STATIC_LINKING_ONLY` macros from code to the target to fix the modular build. It is needed because these macros affect the public API of `zstd.h`.

Reviewed By: terrelln

Differential Revision: D9189720

fbshipit-source-id: efacc1456803900fd65159a43cf1fba2daf15673

Summary: On fork, flush the secureRandom buffer, so that we don't share entropy between the parent and child.

Reviewed By: ricklavoie

Differential Revision: D9196474

fbshipit-source-id: 12ff8488d814466186df61328a5f1d4000beb27f

Summary:
Print benchmark results as and when they complete instead of outputting the
whole thing once at the end

Reviewed By: djwatson, ot

Differential Revision: D9177038

fbshipit-source-id: 54898b303771f214c21163cd87b11f8e2083cdf4

Summary:
When passing a callable to `folly::via` that returns a SemiFuture,
via should return a Future. The implementation does the correct thing
but the declaration's return type is not correct. This diff fixes that.

Reviewed By: yfeldblum

Differential Revision: D9219041

fbshipit-source-id: e61544231e7846c713ff43394c3bf5d1aae18233

Summary: Late change in D9175807 removed necessary temporaries. This caused a lifetime management problem for GCC.

Reviewed By: Orvid

Differential Revision: D9227937

fbshipit-source-id: d5fea8a98855c6302189a7dee8cd5862d13a63a3

Summary: folly::Future's map() functions create a std::vector<Future<...>>, then use push_back to populate that vector. This could result in reallocations. Avoid that by reserving proper space ahead of the push_backs.

Reviewed By: yfeldblum

Differential Revision: D9204713

fbshipit-source-id: 51d9154f483a47c6196a4d4d9d4af14e4eeab6e0

Summary: autotools-based builds are being deprecated, but they lack the symbolizer library target.

Reviewed By: yfeldblum

Differential Revision: D9216312

fbshipit-source-id: 585ce3c43a0800823c7de4ece99b56a1af82bae4

Summary:
Overall plan to modify Future<T>::then to be r-value qualified and use Future<T>::thenTry or Future<T>::thenValue.

The goal is to disambiguate folly::Future and to improve type and lifetime safety of Future and its methods.

 * Deprecate l-value qualified calls to Future<T>::then.
 * Make appropriate changes to folly to make this correct without local deprecation warnings.

Reviewed By: yfeldblum

Differential Revision: D9175807

fbshipit-source-id: 9dc9812270ca3fb800f3a56d3aef8ef3d1d209e6

Summary: [Folly] Dead Code: `folly/experimental/symbolizer/ElfUtil.cpp`.

Reviewed By: calebmarchent

Differential Revision: D9218592

fbshipit-source-id: e231852c068eb797c7c3a4a3955fefc38e4be2fc

Summary:
Original commit changeset: 6b5faf000e5f

Breaks builds on Ubuntu Bionic, effectivly undoing the work of D3878961.
Note: both autotools and CMake builds incorrect on Bionic, its just that
autotools build fails explicitly where CMake fails silently; failing to
detect a correctly installed libdwarf headers. The difference being that
CMake does not build symbolizer.

Reviewed By: yfeldblum

Differential Revision: D9194639

fbshipit-source-id: c6798a0672195a70ced4898535f2f932018224d5

Summary: When merging centroids together, we recalculate the mean and weight. This can sometimes lead to inaccuracy due to floating point arithmetic. In a bad scenario, this can actually lead to the digest being unsorted, which triggers assertions in the code. To fix this, sort the digest at the end of merge. Since this is bounded to 100 elements that are mostly sorted, this appears to be cheap according to benchmarks.

Reviewed By: yfeldblum

Differential Revision: D9213936

fbshipit-source-id: 5a2978a1b759b70206aef57245bef193aed65efd

Summary:
Blocking algorithm:
 Push:
1.  push
2.  increase the PTicket number
3.  put (PTicket << 1) to the corresponding place in futex array.
4.  if the original  futex value & 1  == 1,  wake up ()

Pop:
1.  increase the CTicket number
2.  spin if the corresponding CTicket futex is not ready
3.  set the right bit of the CTicket futex  to 1, wait on it.
4. pop

Add additional control to improve the accuracy:
For the top several levels (top 0 - 3 levels by default), it does not arbitrarily insert any node in the middle of the list. Thus guaranteeing no later coming lower priorities can be insert at the top levels (pruning strategy still valid for the top four levels). For the bottom levels (start from level 7 by default), if insertion requires to hold parent + child locks, it traverses the parent list to check whether the parent list has lower priority nodes than the new node. If the condition holds, insert the new node to the parent and get the last node in the parent list and insert it to the child list.

Reviewed By: magedm

Differential Revision: D9094903

fbshipit-source-id: fa4d31fb0c21da746570029e0e3b4b3fbeaa2024

Summary: This code is hot enough that this might matter. Though likely over-optimization.

Reviewed By: djwatson

Differential Revision: D9197636

fbshipit-source-id: d9e2a90410c03a73d1754d99c72967f5dcd96c0f

Summary: Production data shows that it performs significantly worse under common RequestContext load (few elements, clang lto compiled).

Reviewed By: djwatson

Differential Revision: D9182929

fbshipit-source-id: 0c638268d9b6cd2451b48ccc4e228faf90f0e18e

Summary: Currently, fbcode_builder assumes you're building code living in the facebook github org. If you try to do travis builds using a facebookincubator repo, an error occurs due to hard-coded assumptions about the org. This fixes that

Reviewed By: knekritz

Differential Revision: D9183307

fbshipit-source-id: 0a1ac399953485e84f0534cc0616765227088c80

Summary:
Overall plan to modify Future<T>::then to be r-value qualified and use Future<T>::thenTry or Future<T>::thenValue. The goal is to disambiguate folly::Future and to improve type and lifetime safety of Future and its methods.

Add a std::move that was missed in the folly benchmark.

Reviewed By: shixiao

Differential Revision: D9197265

fbshipit-source-id: d02ab7b0dc22f6465910a80b2d0af1b54fb7bde7

Summary: This update adds the name of the function which called the LOG() to the `LogMessage` object so that a custom formatter could use it to show method name with logs.

Reviewed By: simpkins

Differential Revision: D9071926

fbshipit-source-id: 9d5359d84cf2544371c6f1826f99d8b47a272dd1

Summary:
Apparently certain Android NDK does not support numeric conversion functions of
`basic_string`. Use folly/Conv instead.

Changes generated by `%s/std::to_string/to<std::string>/g`.

In addition, Android SDK's treatment of `long double` is inconsistent. Avoid
that in the tests for now.

Reviewed By: yfeldblum

Differential Revision: D9196009

fbshipit-source-id: 54a32c426a4beb6a0e2d7f95d6b30bf6d7cc67cf

Summary:
When we have a single thread handling both connections and requests, we end up
call the accept callback on the same thread. The code handling the
incoming connections does intend to short-circuit such connection
and not place them on EventBase's queue but it only checks only whether there is no
EventBase registerd for the accept callback. However, by default, we are
registering an EventBase for this callback so this short-circuit falls short
(yay puns).

Reviewed By: djwatson

Differential Revision: D8986246

fbshipit-source-id: 45b817669ae4fd908b39c93ae5b82bb9a14cc2ed

Summary: It's only two stores, but for move that ends up being a large percentage of the work it has to do.  Add initializers in the move constructor, so that we don't both default-initialize and then swap() inline.

Reviewed By: yfeldblum

Differential Revision: D8678422

fbshipit-source-id: 71b574145182ad3a4a3e9d0d824d83abe65fb6fa

Summary: The algorithm in the TDigest paper does not handle weird outliers very well. This diff changes the clamp logic to clamp between the prev and next centroids rather than min_ and max_. This gives much better results.

Reviewed By: yfeldblum

Differential Revision: D9192686

fbshipit-source-id: 171a7b7db5552802f91e6e95bb541a1b03c8821d

Summary:
Add a missing include in `folly/detail/FingerprintPolynomial.h` to fix the
modular build.

Reviewed By: andrewjcg

Differential Revision: D9182707

fbshipit-source-id: c498b10bd02f6528a62fce8145521a97755d6496

Summary: We have a surprisingly high number of unrelated dependencies on those 2 imports

Reviewed By: djwatson

Differential Revision: D9155350

fbshipit-source-id: e85e42934af8378cdc0db909d8a6afacb504df8f

Reviewed By: yfeldblum, palmtenor

Differential Revision: D9144908

fbshipit-source-id: 6201a4beaf1e2d2cf16c8e3986097a6e8e47c6f3

Summary: Per title

Reviewed By: mingtaoy

Differential Revision: D9159614

fbshipit-source-id: d26320587ae55b4415185206a7a6a5f8f38ff428

Summary:
- Several files have the executable bit set and do not need to.
Pull Request resolved: https://github.com/facebook/folly/pull/904

Differential Revision: D9177526

Pulled By: yfeldblum

fbshipit-source-id: 5dd5d5cfca5b184b42de4db4a052daaadfef2496

Summary:
Resubmitting as https://github.com/facebook/folly/pull/743 failed internal builds according to yfeldblum

Edit: as pointed out in the conversation below, this check needs to be gated for Boost versions [1.59, 1.64] as Boost 1.65 removed this method.
Closes https://github.com/facebook/folly/pull/745

Reviewed By: Orvid

Differential Revision: D6853821

Pulled By: yfeldblum

fbshipit-source-id: 2e0c8f425055ee82c317146c4c836c28f7130e9b

Summary:
Replace `folly/Histogram.h` by `folly/stats/Histogram.h`.  Use `auto` to declare type of `getNumBuckets`.
Pull Request resolved: https://github.com/facebook/folly/pull/892

Reviewed By: aary

Differential Revision: D9043331

Pulled By: yfeldblum

fbshipit-source-id: 51dc6164f78ab72b947327e31f198a33a56c5fc4

Summary:
Problem:
- There was a bug in a much older version of MSVC relating to
  accessing functions in an anonymous namespace with the workaround
  being to have an extra anonymous namespace.

Solution:
- Remove the workaround as the MSVC versions that Folly now targets
  (MSVC 2015 and MSVC 2017) should not have this bug.
Pull Request resolved: https://github.com/facebook/folly/pull/898

Reviewed By: aary

Differential Revision: D9176601

Pulled By: yfeldblum

fbshipit-source-id: 7db87d28f8968eb5b3ff9d9375777f997b060a59

Summary:
According to https://github.com/pytorch/pytorch/pull/6697, ARM64 clang from the
Android SDK does not define the newer `__ARM_NEON` macro (specified in the ARM
C language extensions 2.1:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ihi0053d/index.html),
but rather, it uses `__ARM_NEON__`.

Portability should check for both until full deprecation?

Reviewed By: nbronson

Differential Revision: D9163276

fbshipit-source-id: db6407f85b21b0ad3e4d564c73ef3ca5d8a16c2f

Summary:
Add some missing headers required for
other oss projects.

These were not synced to the makefile.

Reviewed By: shixiao

Differential Revision: D9161271

fbshipit-source-id: 283042c35ac9f78fef24348e0d78b26ab8f2eeb8

Summary:
On architectures with SSE2 but not AVX2, the _mm_set1_epi8
intrinsic at the core of F14Table::findImpl expands to multiple
instructions.  One of those is a MOVD of either 4 or 8 byte width.
Only the bottom byte of that move actually affects the result, but
if a 1-byte needle has been spilled then this will be a 4 byte load.
GCC 5.5 has been observed to reload (or perhaps fuse a reload and a
narrow) needle using a MOVZX with a 1 byte load in parallel to the MOVD.
This combination causes a failure of store-to-load forwarding, which has
a big performance penalty (60 nanoseconds per find on a microbenchmark).
Keeping needle >= 4 bytes avoids the problem and also happens to result
in slightly more compact code.

Reviewed By: yfeldblum

Differential Revision: D9149727

fbshipit-source-id: 9e957207c23914da317e763eb944bf7dd43a5c51

Summary:
Change "If advanced debugging functionality is required" to "If advanced debugging functionality is required, use:" for consistency in README.md and to be more reader friendly.
Pull Request resolved: https://github.com/facebook/folly/pull/894

Reviewed By: shixiao

Differential Revision: D9094182

Pulled By: yfeldblum

fbshipit-source-id: 147d436aaee291104b67eab1e549554696740907