Summary:
If we're going to have a constructor for it, we should have operator=.

Otherwise, gcc-4.9 goes via the copy constructor effectively "ignoring" the attempted nesting for e.g..

```
d = { other_dynamic };  // Should be ARRAY containing dynamic
```

NOTE: this only fixes gcc-4.9, there's still issues in clang.

Reviewed By: yfeldblum

Differential Revision: D2745180

fb-gh-sync-id: 667787c788fc7c131d8a34c608c355f5b875be50

Reviewed By: alikhtarov

Differential Revision: D2741459

fb-gh-sync-id: c4bd068cf735ae25364edba40960096fb35e8c43

Summary:
By default signal handlers are run on the signaled thread's stack.
In case of stack overflow running the `SIGSEGV` signal handler on
the same stack leads to another `SIGSEGV` and crashes the program
Use `SA_ONSTACK`, so alternate stack is used (only if configured via
`sigaltstack`).

Reviewed By: luciang

Differential Revision: D2747021

fb-gh-sync-id: 48388acd6147e2919412ec32acfca1ca76f22a16

Summary:
[Folly] Use `SharedMutex` as the default mutex type in `Synchronized`.

`folly::SharedMutex` is, overall, a faster mutex than `boost::shared_mutex`. Let's upgrade.

Reviewed By: nbronson

Differential Revision: D2743132

fb-gh-sync-id: e36881495e8e1002cd481607e05e555c5da19b9a

Summary: Revert D2741855

Reviewed By: mzlee

Differential Revision: D2744015

fb-gh-sync-id: b1e9b0a5ab95cb988d2b5c08c86139452b092465

Summary: Unit test showing array assignment problem on gcc 4.9

Reviewed By: lbrandy

Differential Revision: D2739900

fb-gh-sync-id: 6b0fde956672b8248fbd4e620fd112195c45c646

Reviewed By: pavlo-fb

Differential Revision: D2743230

fb-gh-sync-id: 4a52d1758a43fd103318bbe0913776340eaa6af7

Summary: There is slight drift in external deps between the TARGETS and automake files, keeping tests from linking in the 'make check' step when building folly outside of fbcode.

Reviewed By: yfeldblum

Differential Revision: D2740482

fb-gh-sync-id: ae6243f9bb112a7d2680017b3d577a1f23ef4f60

Summary: Update the protocol pick logic to use discrete_distribution

Reviewed By: siyengar

Differential Revision: D2741855

fb-gh-sync-id: 244bd087124a7a9584a1108fe8f8150093275878

Summary:
This also introduces a new try_get_fast() API which returns ReadMostlySharedPtr.
We should eventually migrate all users onto this API.

Reviewed By: elsteveogrande

Differential Revision: D2706745

fb-gh-sync-id: d558d705f431fc6147334c188fd0c6156644ba5c

Summary: With openssl-1.0.2 and later add support for ALPN.  Clients can request NPN only, but the default is to support either (client will send ALPN list, server will send NPN advertisement if ALPN is not negotiated).

Reviewed By: siyengar

Differential Revision: D2710441

fb-gh-sync-id: a8efe69e1869bbecb4ed9e0a513448fcfdb21ca6

Summary: EINTR should be retried

Reviewed By: afrind

Differential Revision: D2735879

fb-gh-sync-id: 6f25cd26e29ab8e7e13a3d63f24bf2d104c14809

Summary:
This is an experimental diff that may improve the performance of `HHWheelTimer::cancelAll`. If there are no timers to cancel, then it can bail early.

Since perflab is unlikely to be conclusive, and since this diff looks like a strict improvement, I'll proceed with landing it.

Reviewed By: djwatson

Differential Revision: D2735297

fb-gh-sync-id: 9f5a811ee6d9fa9434576e9abd3ef3443a7579b7

Reviewed By: pavlo-fb

Differential Revision: D2708425

fb-gh-sync-id: 665d077210503df4f4e8aa8f88ce5b9b277582f3

Summary: New version.

Reviewed By: cyan

Differential Revision: D2730844

fb-gh-sync-id: 4305bdfba2e8d25eba295bbf3f13a140c0d04a1c

Summary:
Mark some methods as virtual.  This makes writing some
better unit tests on the associated task possible.

Reviewed By: siyengar

Differential Revision: D2730126

fb-gh-sync-id: f79f7632e873cb218bb49883d9b53beea7bb96e7

Summary: when a promise is broken, add type info to the message. This will allow for some small improvements to debugging errors from broken promises, namely giving developers a slightly more refined target to grep for.

Reviewed By: fugalh

Differential Revision: D2725575

fb-gh-sync-id: b92edbde874e63eaeab97395da7bb52f76968800

Reviewed By: djwatson

Differential Revision: D2720027

fb-gh-sync-id: 1d56aabedeaf65a5d48e152eaee5c81695be7620

Summary: Adding a flag in `folly::json::serialization_opts` that allows you to request all numbers to be parsed into strings. This saves you from exceptions being thrown by `folly::parseJson` if it encounters numbers that wouldn't fit in int64.

Reviewed By: yfeldblum

Differential Revision: D2713039

fb-gh-sync-id: 4f3d0d20f3012efd6229adf895200a3901bb4493

Reviewed By: mzlee

Differential Revision: D2709222

fb-gh-sync-id: 67a00a49bbcef5572b6092d7bfba1842d985e643

Summary: getRawBytesReceived and getRawBytesWritten should be used instead.

Reviewed By: mzlee

Differential Revision: D2708684

fb-gh-sync-id: 2de87dc2b8c3466f94293a3d7df89fc5fce3a00f

Summary:
In rare cases, it is required to run code **in the child process**, before it calls `exec()` because you need to change the state of the process **before** the child binary gets to run. This diff adds a callback to permit this. The callback is deliberately harder to use than an `std::function`, because you **REALLY HAVE TO KNOW WHAT YOU ARE DOING** to use this. And you have to check your work three times. Even glog `LOG()` must not be called from inside this callback. Your random library of choice is also probably unsafe.

This diff is primarily applicable to job managers and shells. For example, these tasks benefit from this callback: adding a child to a Linux `cgroup`, twiddling its various POSIX process attributes.

Implementing a correct callback for the post-vfork environment is fraught with peril. Read http://ewontfix.com/7/, and the docstrings in this diff.

Reviewed By: yfeldblum

Differential Revision: D2688323

fb-gh-sync-id: aae49e2b3957ca845895acca26e9cb44df1afc07

Summary: Currently, the tryRunAfterDelay implicitly converts a negative delay in int to unsigned int. With this change, the api makes it clear than only unsinged int is accepted as valid delay

Reviewed By: yfeldblum

Differential Revision: D2710034

fb-gh-sync-id: cb3c6b91bb86bbe07fa0e590b2ea871242d19745

Summary:
Change mutex to MicroSpinLock, for constexpr-ctor-ness on OSX.

Fixes this error seen on mac:

  ThreadLocalDetail.h:202:38: note: non-literal type 'std::mutex' cannot be used in a constant expression

Reviewed By: ldemailly

Differential Revision: D2713511

fb-gh-sync-id: bc1c34b4a0ee21347278aa368b408f286345e050

Summary: Small, silly bug which is triggered when there are no keys to unregister, invalidating the current size of the structure.

Reviewed By: yzhan

Differential Revision: D2712604

fb-gh-sync-id: f6f031936d8e4e458b49c08714f42cb2eec4c4fe

Summary: Comes in handy, and std::experimental::optional has it.

Reviewed By: yfeldblum

Differential Revision: D2708324

fb-gh-sync-id: 87cdf2449f356d3baf9fb56a608e9c43d8fe79ae

Summary:
Since this is used in so many places during the program's static-initialization (at startup), this class itself could be (has been demonstrated to be) a point of SIOF problems itself.

Made this class constexpr-constructible, so it doesn't need to be part of static initialization, making it SIOF-proof.

Reviewed By: luciang

Differential Revision: D2709231

fb-gh-sync-id: f248c9f2848c09045e000cfdc03636d847e522c9

Summary: This is a //tiny// documentation change. I noticed that there are lots of places in the codebase where people follow this recommended usage of `with_exception` in an if–else chain, (e.g., https://fburl.com/181606454). IMHO, a short-circuiting `||` operator is easier to read and write.

Reviewed By: yfeldblum

Differential Revision: D2687840

fb-gh-sync-id: 6354555aeba81dcfe7adf17e7e573de0b1206b37

Summary: facepaw

Reviewed By: djwatson

Differential Revision: D2709030

fb-gh-sync-id: 20fe50bc70e97c4fedeae8fd271a4de70fa0e805

Summary: [Folly] Avoid requiring a suppression (`unevaluated-expression`).

I am not a fan of suppressing warnings. This warning comes from the internals of gtest, but anyway.

Replace with something that does not trigger the warning.

Reviewed By: Gownta

Differential Revision: D2706279

fb-gh-sync-id: 2ecac1d230308a8fd21a69565193c52585526448

Summary: Add template parameters to support arbitrary types when looking up a key.

This is useful to avoid the cost of 'materializing' a key which is likely to be present in the array (or, alternatively, switching on a tagged union KeyT).

Use the new capability to greatly simplify the lookup logic in HHVMs static string table.

Reviewed By: nbronson

Differential Revision: D2662451

fb-gh-sync-id: 707fa033f350b80ca8080af17f1a8a74c59f2e88

Summary: Using -Werror and -Wfloat-conversion was causing failure in code that is deliberately
performing that conversion.  Add explicit casts to avoid the warnings/errors.
Here are two of the diagnostics:

  ./folly/Conv.h: In instantiation of "typename std::enable_if<std::is_floating_point<_Tp>::value, Tgt>::type folly::to(folly::StringPiece) [with Tgt = float; typename std::enable_if<std::is_floating_point<_Tp>::value, Tgt>::type = float; folly::StringPiece = folly::Range<const char*>]":
  ./thrift/lib/cpp2/protocol/SimpleJSONProtocol.tcc:687:28:   required from "T apache::thrift::SimpleJSONProtocolReader::castIntegral(const string&) [with T = float; std::string = std::basic_fbstring<char>]"
  ./thrift/lib/cpp2/protocol/SimpleJSONProtocol.tcc:680:26:   required from "uint32_t apache::thrift::SimpleJSONProtocolReader::readJSONKey(T&) [with T = float; uint32_t = unsigned int]"
  ./thrift/lib/cpp2/protocol/SimpleJSONProtocol.tcc:654:16:   required from "uint32_t apache::thrift::SimpleJSONProtocolReader::readInContext(T&) [with T = float; uint32_t = unsigned int]"
  ./thrift/lib/cpp2/protocol/SimpleJSONProtocol.tcc:1035:34:   required from here
  ./folly/Conv.h:1222:31: error: conversion to "float" from "std::enable_if<true, double>::type {aka double}" may alter its value [-Werror=float-conversion]

  ./folly/Conv.h: In instantiation of "typename std::enable_if<((std::is_integral<_Tp2>::value && std::is_floating_point<_Tp>::value) || (std::is_floating_point<_DInputType>::value && std::is_integral<_Tp>::value)), Tgt>::type folly::to(const Src&) [with Tgt = long int; Src = double; typename std::enable_if<((std::is_integral<_Tp2>::value && std::is_floating_point<_Tp>::value) || (std::is_floating_point<_DInputType>::value && std::is_integral<_Tp>::value)), Tgt>::type = long int]":
  ./folly/dynamic-inl.h:636:51:   required from "T folly::dynamic::asImpl() const [with T = long int]"
  ./folly/dynamic-inl.h:384:64:   required from here
  ./folly/Conv.h:1245:16: error: conversion to "long int" from "double" may alter its value [-Werror=float-conversion]

This change deserves a little more explanation:

  -  return ceil((double(sizeof(IntegerType) * CHAR_BIT) * M_LN2) / M_LN10);
  +  return (unsigned int)(ceil(sizeof(IntegerType) * CHAR_BIT * M_LN2 / M_LN10));

In addition to adding the cast to destination type, I have also removed the unnecessary cast to double of the first product (there is not risk that it will overflow, and no need to promote to double, there), and I have also removed the grouping parentheses, since the standard left-to-right evaluation works just fine here.

Reviewed By: Gownta, yfeldblum

Differential Revision: D2703928

fb-gh-sync-id: 23b49281d9120d106f1fdbd30921e8f39c01367d

Summary: CodeMod: Use the `ExceptionWrapper::with_exception` variant that deduces exception types.

Since we must specify the exception type in the lambda arg, and there is a variant of `ExceptionWrapper::with_exception` that deduces the type of the exception from the type of the lambda arg, we don't need to specify the exception type again as a template parameter anymore.

Reviewed By: meyering

Differential Revision: D2694895

fb-gh-sync-id: 505469f9008973a315e836f356e5db97df4ec921

Summary: Do not negate signed numbers like INT_MIN or INTMAX_MIN, since
that would evoke undefined behavior.  Otherwise, the test (below)
would fail with this run-time error:

  [ RUN      ] Conv.Integral2String
  folly/Conv.h:521:47: runtime error: negation of -2147483648 cannot be represented in type 'int'; cast to an unsigned type to negate this value to itself

Reviewed By: markisaa

Differential Revision: D2704195

fb-gh-sync-id: 4036437fb972109672004163880078127e7df797

Summary: [Folly] Avoid deprecated `Singleton<T>::get()` in `folly/futures`.

Changes `getTimekeeperSingleton()` to return a `shared_ptr<Timekeeper>`, and patches its call-sites.

Additionally, have the call-sites keep the singleton instance alive for the duration that it is being directly used.

Reviewed By: ddrcoder

Differential Revision: D2702361

fb-gh-sync-id: 82b72ee514dc4f2a7f7522af8b2e92b34df063d6

Summary: get_weak() is always used with .lock(), but try_get() is actually more performant than get_weak().lock().
Using get_weak() to store a weak_ptr and keep locking is not safe in fork scenarios.

Reviewed By: yfeldblum

Differential Revision: D2694223

fb-gh-sync-id: 908d44293ffd9b3782152d43e28d5de172d1654a

Summary: [Folly] Fix `ExceptionWrapper::with_exception` to support lvalue ref functors.

Ex:

    auto handler = [&](const std::runtime_error& e) { handle_runtime_error(e); };
    exception_wrapper wrap = get_some_exception_wrapper_from_context();
    wrap.with_exception(handler); // broken before this diff, fixed after

Reviewed By: markisaa

Differential Revision: D2698680

fb-gh-sync-id: 4976ba08e3601e22891d00d79a5dae5118887b71

Summary: This changes ReadMostlySharedPtr API to have 3 types: MainPtr, WeakPtr, SharedPtr. MainPtr and SharedPtr are equivalents of std::shared_ptr, and WeakPtr is an equivalent of std::weak_ptr. The only difference is that it can only be a single MainPtr, and while it's alive copying SharedPtr/WeakPtr or WeakPtr doesn't require atomic operations (and thus can be more performant than std::shared_ptr). Unlike original ReadMostlySharedPtr API, there're no thread-safety guarantees between reset() and getShared() for ReadMostlySharedPtr.

ReadMostlySharedPtr can work with different RefCount implementations. This diff introduces RCURefCount (which is currently using liburcu) and TLRefCount.

Reviewed By: djwatson

Differential Revision: D2683572

fb-gh-sync-id: a7a03af4b1cf5f81a613368c6eebe70b2eaef064

Summary: So far this is a speculative fix.. I am waiting to see the results from the Ubuntu machine, but I suspect this is the problem.

Reviewed By: bugok

Differential Revision: D2697600

fb-gh-sync-id: e33d452a52c5ace2b7401d6495621ce68a5076b5

Summary: See D2696092

Reviewed By: meyering

Differential Revision: D2696360

fb-gh-sync-id: 2cfa9258be899a93a58c59dae70a10fef6f457c8