Summary:
Include the fbcode_builder sources in the folly repository under
build/fbcode_builder/.  These build scripts will make it easier. to set
up continuous integration for the opensource github repository.

Note that for folly this is potentially slightly confusing, since this
will now add a top-level build directory in addition to the existing
folly/build subdirectory.  However, it seems easiest for now to follow
the default fbcode_builder conventions.

This does not yet include configuration files for the folly build--I
will add those in a subsequent diff.

Test Plan:
Confirmed the CI build work with the upcoming configuration files.

Reviewed By: yfeldblum

Differential Revision: D6700052

fbshipit-source-id: ba026835e866bda5eed0776ec8bbf1ac51014034

Summary:
Some compilers such as Apple Clang do not support the compiler flag `-fopenmp`. So, do not add it by default to the list of `CXX_FLAGS` that are expected for *every* compiler to support. Instead, check if the `CXX_COMPILER` specified by `CMake` supports `-fopenmp` by using `CHECK_CXX_COMPILER_FLAG`.
Closes https://github.com/facebook/folly/pull/741

Reviewed By: simpkins

Differential Revision: D6843171

Pulled By: yfeldblum

fbshipit-source-id: 671958d867400b5802d7d563036639d61d11f615

Summary: Update CMakeLists.txt to support CMake versions as old as 3.0.2.

Reviewed By: yfeldblum

Differential Revision: D6843104

fbshipit-source-id: 43c2fc685c63df373ed33183f8144de779c97edf

Summary:
Within() is not properly propegating cancellations and other
interrupts via raise() since it technically breaks the normal propegation
mechnaism of copying the interrupt handler pointer.

Reviewed By: yfeldblum

Differential Revision: D6838285

fbshipit-source-id: 8f3efbd3eebe21c2f348b6aba991b0997be4f14f

Summary: [Folly] Move `folly/PicoSpinLock.h` to `folly/synchronization/`.

Differential Revision: D6830101

fbshipit-source-id: 529df14d9cda46bae5989f901ca73effbe0022e5

Summary: [Folly] Fixed initialization of `Tearable` with libstdc++-v4.9.2, which is missing definitions of `atomic_init`.

Reviewed By: davidtgoldblatt

Differential Revision: D6833004

fbshipit-source-id: 88d4cc91f90618a98df110bec5e434c35e750b16

Summary:
The SingletonTestGlobal code asserted that there was exactly one singleton
object registered (the one defined in this test file).  However if folly is
built as a shared library, all of it will be loaded, and several other
singletons are also defined by other parts of folly.  (Currently 7 singletons
get registered.)

Reviewed By: yfeldblum

Differential Revision: D6817544

fbshipit-source-id: de3947770690ffb68d097040bbbfbe42bce3bf94

Summary: Add more types and a macro to make defining them easier.

Reviewed By: mingtaoy

Differential Revision: D6823450

fbshipit-source-id: eb13a8b48efb1625fc3f8035356812f918703c6d

Summary: Foolishly #defined __has_feature when it wasn't and let it leak, but something later must have been relying on something similar. This replaces the uses with FOLLY_HAS_FEATURE.

Reviewed By: yfeldblum, magedm

Differential Revision: D6829724

fbshipit-source-id: 40635dd67135316f27be2aa2a6b2d579dbf843e1

Summary: thread_local does not work on certain mobile builds. This will disable it if FOLLY_MOBILE is set.

Reviewed By: yfeldblum, magedm

Differential Revision: D6785773

fbshipit-source-id: 6a74edec739f42562045aadb4e1ee39d121ce90d

Summary:
This Diff adds new `FOLLY_SDT_WITH_SEMAPHORE` Macro that allows the (potentially expensive) Static Tracepoints be gated with Semaphore and be enabled on-demand.
The Semaphores are compatible with SystemTap's Tracepoint Semaphores, with the following difference:
- Instead of having build Process generate a header file containing the Semaphore variable and check function, and to be included, this Diff uses the approach that users need to explicitly define the semaphore using `FOLLY_SDT_SEMAPHORE_DEFINE` before using `FOLLY_SDT_WITH_SEMAPHORE`. Then the check function could be used in the same file, or in any other linked module with doing `FOLLY_SDT_SEMAPHORE_DECLARE` first. This is inspired from GFlag's defining and declaring.
- We keep allowing original `FOLLY_SDT` with no Semaphore for flexibility.

Differential Revision: D6814268

fbshipit-source-id: e1e4463c71539b4d2071b21880d4ee7689fedce8

Summary:
Since C++14, constexpr non-static member function will not be implicitly marked
const. See the blog post below for more details.
https://akrzemi1.wordpress.com/2013/06/20/constexpr-function-is-not-const/

Reviewed By: mzlee

Differential Revision: D6819658

fbshipit-source-id: 4a756191fca3e744bda3c63c2669e24d6b16861e

Summary: [Folly] Move `folly/SmallLocks.h` to `folly/synchronization/`.

Differential Revision: D6806563

fbshipit-source-id: 26c7be6b6a01673a4f58a0952b5c531528f8ca7f

Summary: Create a "fast" stack trace printer that caches symbol lookups.

Reviewed By: yfeldblum

Differential Revision: D6000178

fbshipit-source-id: e81be1db21cfcd2cd26524c9ef6262337153ae36

Summary:
D6806326 reduced the minimum version of CMake required to 3.2.0.  This had the
unintended effect of also disabling some newer CMake policies by default, which
caused builds to fail in newer CMake versions.

In particular, we make use of the GoogleTest module when it is available (CMake
3.9+).  However it requires policy `CMP0057` to be enabled.

This explicitly enables `CMP0057` when it is available.

Reviewed By: yfeldblum

Differential Revision: D6816891

fbshipit-source-id: 60ca46654d46207a96f0fad9c3467426a25b4afd

Summary:
Several of the tests in LoggerTest.cpp check error messages that include
demangled type names.  The type names are returned slightly differently on
other platforms (e.g., `i` instead of `int`, or `A13_c` instead of
`char [13]`)

This changes the tests to perform regular expression matches rather than exact
string matches.  This now allows any strings to appear where a type name is
expected.

Reviewed By: yfeldblum

Differential Revision: D6805680

fbshipit-source-id: 56d501944dacb505c3c09d84c555a1f686065077

Summary:
The `ThreadLocal.SharedLibrary` test depends on building a separate
`thread_local_test_lib.so`.  This can only be built when folly was compiled
with PIC.

This also fixes the test to fail normally rather than segfaulting if it cannot
load `thread_local_test_lib.so`.

Reviewed By: yfeldblum

Differential Revision: D6805683

fbshipit-source-id: b451b94c2a4b3184a8f61de3b7f83e69169205f0

Summary:
In general, building folly as a shared library is not recommended since the
library ABI changes frequently.

Nonetheless, this updates the CMake files to support building with
`BUILD_SHARED_LIBS=ON`.  Previously the build would fail when using this
option.

The main reason to support this for now is because some of the tests can only
be run when compiled with `-fPIC`.  Defining `FOLLY_SHARED_LIBRARY_SUPPORT` in
`folly-config.h` makes it possible to skip these tests when being compiled
without shared library support.

Reviewed By: yfeldblum

Differential Revision: D6805682

fbshipit-source-id: 098290c7405837350577f48ed224947fb62415db

Summary:
Update the CMake build scripts to work with CMake 3.2.2, as well as older boost
libraries.

Several other open source Facebook projects have CI that checks that the code
builds with modified Ubuntu 14.04 systems (Ubuntu 14.04 + gcc 4.9 +
CMake 3.2.2).  By default Ubuntu 14.04 ships with gcc 4.8.2 and CMake 2.8; we
do not support vanilla Ubuntu 14.04.

Reviewed By: yfeldblum

Differential Revision: D6806326

fbshipit-source-id: 243f2f9cea20c7a9430dc386c921e3cafeee77f7

Summary:
[Folly] Dedup spinning in `Baton` and `SaturatingSemaphore`.

And add spin-yield to spin-only `SaturatingSemaphore`, as is done in `Baton`.

Reviewed By: djwatson

Differential Revision: D6726786

fbshipit-source-id: 428efb950577ab1d500caffe56bf2a8cacf66c34

Summary: [Folly] Split `SaturatingSemaphore` test cases into spin-only and may-block variants.

Reviewed By: djwatson

Differential Revision: D6726718

fbshipit-source-id: d22a76de6077d9c8b4eb2ef7f6d118f48c8c5104

Summary:
[Folly] Use relaxed CAS in `Baton` wait path.

As is done in `SaturatingSemaphore`. There are surrounding operations on `state_` with stronger memory orders.

Reviewed By: nbronson

Differential Revision: D6726704

fbshipit-source-id: 8032db4b98a09455c84c730e2e99515d1a9442da

Summary:
[Folly] Merge wait and timed-wait implementations in `Baton`.

Now `MemoryIdler` is also used in the timed-wait case, not just in the wait case.

Reviewed By: spalamarchuk

Differential Revision: D6720048

fbshipit-source-id: 7612eb60d1908d08d41897fa163b0693b59abab1

Summary:
`std::make_from_tuple` constructs an object of type T, using the elements of the
tuple t as the arguments to the constructor. Backport.

For the unit test, I referred to
https://github.com/phalpern/uses-allocator/blob/711f6071a1230272de28c022400d678e7e9f0228/make_from_tuple.t.cpp

Reviewed By: yfeldblum

Differential Revision: D6808665

fbshipit-source-id: 257f27110c01da39b5415b02415d74f0b6062051

Summary: [Folly] Cut extraneous dep on `glog` from `Expected`.

Reviewed By: mzlee

Differential Revision: D6768016

fbshipit-source-id: 7b242797ccfe18ea7ccb3ef7a045ff55147dd2eb

Summary:
When `gtest_add_tests()` is not available (CMake versions before 3.9) just use
`add_test()` to add each test executable as a single test.

Reviewed By: yfeldblum

Differential Revision: D6805681

fbshipit-source-id: a5fa95600dc29659498725cdc3cb1ae00188e1a3

Summary: [Folly] Fix `folly/synchronization/Tearable.h` under `gcc49`, which version of `libstdc++` lacks `std::is_trivially_copyable`.

Reviewed By: simpkins

Differential Revision: D6805662

fbshipit-source-id: 5f368cda58b860c7a7ee05addb325a655ab09830

Summary:
If the callback passed to `window` throws an exception, the process will
segfault.

This happens because `Core::doCallback` will execute a callback that throws
an exception twice. Once with the original arguments, and again with the wrapped
exception: https://fburl.com/wdmztc4l

In the case of `window`, the callback in question moves its `ctx` to the next
iteration of `spawn`, and so the second call to the callback segfaults.

This prevents the issue by wrapping the call to `func` in a future, which captures
the exception and returns it to the caller, rather than allowing it to bubble out and
break things.

Reviewed By: yfeldblum

Differential Revision: D6802396

fbshipit-source-id: 3595c622e8e8f58209c7b20f553f7642bc49c089

Summary:
[Folly] Improve the `SingletonThreadLocal` fast path.

Principally, by having the thread-local cache checked checked before the static-local guard variable is checked, rather than after.

This change measurably improves the `EventBase` benchmark:

```name=branch
============================================================================
folly/io/async/test/EventBaseBenchmark.cpp      relative  time/iter  iters/s
============================================================================
timeMeasurementsOn                                           1.02us  980.21K
timeMeasurementsOff                              251.64%   405.41ns    2.47M
============================================================================
```
```name=master
============================================================================
folly/io/async/test/EventBaseBenchmark.cpp      relative  time/iter  iters/s
============================================================================
timeMeasurementsOn                                           1.03us  969.51K
timeMeasurementsOff                              247.08%   417.45ns    2.40M
============================================================================
```

This change shortens the fast-path in `folly::RequestContext::getStaticContext()` (manually cleaned up):

```name=branch
---- fast path ----
<+0>:     mov    rax,QWORD PTR fs:folly::SingletonThreadLocal<...>::get()::cache@tpoff
<+9>:     test   rax,rax
<+12>:    je     folly::RequestContext::getStaticContext()+16
<+14>:    ret
<+15>:    nop
---- slow path ----
<+16>:    push   rbp
<+17>:    mov    rbp,rsp
<+20>:    call   folly::SingletonThreadLocal<...>::getWrapperOutline()
<+25>:    mov    rdx,QWORD PTR fs:0x0
<+34>:    mov    QWORD PTR fs:folly::SingletonThreadLocal<...>::get()::cache@tpoff,rax
<+43>:    add    rdx,OFFSET FLAT:folly::SingletonThreadLocal<...>::get()::cache@tpoff
<+50>:    mov    QWORD PTR [rax+0x10],rdx
<+54>:    pop    rbp
<+55>:    ret
```
```name=master
---- fast path ----
<+0>:     push   rbp
<+1>:     mov    rbp,rsp
<+4>:     push   rbx
<+5>:     sub    rsp,0x8
<+9>:     cmp    BYTE PTR guard variable for folly::RequestContext::getStaticContext()::singleton[rip],0x0
<+16>:    je     folly::RequestContext::getStaticContext()+48
<+18>:    mov    rax,QWORD PTR fs:folly::SingletonThreadLocal<...>::get()::cache@tpoff
<+27>:    test   rax,rax
<+30>:    je     folly::RequestContext::getStaticContext()+96
<+32>:    mov    rbx,QWORD PTR [rbp-0x8]
<+36>:    leave
<+37>:    ret
<+38>:    nop    WORD PTR cs:[rax+rax*1+0x0]
---- slow path ----
<+48>:    mov    edi,OFFSET FLAT:guard variable for folly::RequestContext::getStaticContext()::singleton
<+53>:    call   __cxa_guard_acquire
<+58>:    test   eax,eax
<+60>:    je     folly::RequestContext::getStaticContext()+18
<+62>:    sub    rsp,0x8
<+66>:    mov    edi,OFFSET FLAT:folly::RequestContext::getStaticContext()::singleton
<+71>:    push   0x0
<+73>:    call   folly::SingletonThreadLocal<...>::SingletonThreadLocal({lambda()})
<+78>:    pop    rax
<+79>:    mov    edi,OFFSET FLAT:guard variable for folly::RequestContext::getStaticContext()::singleton
<+84>:    pop    rdx
<+85>:    call   __cxa_guard_release
<+90>:    jmp    folly::RequestContext::getStaticContext()+18
<+92>:    nop    DWORD PTR [rax+0x0]
<+96>:    call   folly::SingletonThreadLocal<...>::getSlow()
<+101>:   mov    rbx,QWORD PTR [rbp-0x8]
<+105>:   mov    QWORD PTR fs:folly::SingletonThreadLocal<...>::get()::cache@tpoff,rax
<+114>:   leave
<+115>:   ret
<+116>:   mov    rbx,rax
<+119>:   mov    edi,OFFSET FLAT:guard variable for folly::RequestContext::getStaticContext()::singleton
<+124>:   call   __cxa_guard_abort
<+129>:   mov    rdi,rbx
<+132>:   call   _Unwind_Resume
```

Reviewed By: andriigrynenko

Differential Revision: D6763655

fbshipit-source-id: 6f2d317ffd40a4e1f143b4bbbd087e85cc667b8c

Summary: Add method to recursively compute RFC7386-compliant merge-diff between two folly::dynamic objects.

Reviewed By: yfeldblum

Differential Revision: D6794339

fbshipit-source-id: f2b807404faa922d5a705f858825329a95fb0d38

Summary: [Folly] Fix autotools build to include `GlobalShutdownSocketSet`.

Reviewed By: pixelb

Differential Revision: D6801184

fbshipit-source-id: f832b6b5b77872d1ced44295efee7a39529561aa

Summary:
The top-level CMakeLists.txt explicitly includes any files inside "test"
subdirectories.  However, the folly/io/async/test contains several library
headers and sources that we do want to include in libfolly.  Explicitly
re-include these files.

Reviewed By: yfeldblum

Differential Revision: D6794707

fbshipit-source-id: 9df3157503f317c49e48252497b8a3d06e6161d5

Summary:
[Folly] Split out the global `ShutdownSocketSet` singleton into its own library to keep the dependencies of `ShutdownSocketSet` lighter-weight.

In general, globals should be an opt-in sort of thing anyway.

Reviewed By: elsteveogrande

Differential Revision: D6790009

fbshipit-source-id: c68fa2bbaeaf3ff205e0c3b1c739d7561e940e64

Summary:
Previously to use gmock you simply needed to link against libgmock_main.
However, googletest pull request #1339 was recently merged into upstream
googletest: https://github.com/google/googletest/pull/1339

These changes now require explicitly linking against libgmock_main, libgmock,
and libgtest.

Reviewed By: yfeldblum

Differential Revision: D6794709

fbshipit-source-id: 03dcccec966e62240987ee0051dfa87be8614cca

Summary:
The exception_tracer code changes program behavior when you link it in.
Therefore it should not be included in the main libfolly library.

This splits the exception_tracer code out into 3 separate libraries, which
matches the behavior described in the exception_tracer README.md file.

Reviewed By: yfeldblum

Differential Revision: D6787807

fbshipit-source-id: 51400c3ff464d359b4acc56679b5f584f3b586fd

Summary:
Move Benchmark.cpp out of the main libfolly library and into its own
libfollybenchmark library.

This more closely follows the build artifacts produced by the autoconf build,
and will help avoid breaking downstream projects that depend on folly and
expect to find libfollybenchmark.  The code in Benchmark.cpp is also normally
only needed by test programs.

Reviewed By: yfeldblum

Differential Revision: D6793538

fbshipit-source-id: fd273c11fc9f199a159b9e5d14badaf805480db0

Summary: Exported symbol breaks under strict warnings on some mobile builds. Remove export by using anonymous namespace as it is not required.

Reviewed By: yfeldblum

Differential Revision: D6791282

fbshipit-source-id: fd7f8294fdcdc2069cc6fea64c9e269bc094c9f8

Summary: Merge patch is simple method of editing JSON documents. This implementation uses the recursive version documented in the RFC.

Reviewed By: yfeldblum

Differential Revision: D6777104

fbshipit-source-id: 554f801fe793a6fe004a8321ca41510b48225aa9

Summary: as title

Reviewed By: yfeldblum

Differential Revision: D6565911

fbshipit-source-id: 5bed8f44520f6c1d7d6e685bf2a38cf97f734205

Summary: Variable shadowing warning under specific compiler flags. This works around that by renaming.

Reviewed By: yfeldblum

Differential Revision: D6782706

fbshipit-source-id: 60f379f301a88ab370b056469693a198439d1b11