Summary:
A library that provides gflags-like functionality, with the addition of:
- Threadsafe read/writes for all flags
- Arbitrary C++ types
- No declare/define split, all setting definitions are declaration and are safe to place in headers
- Runtime introspection of all flags
- Compile time and runtime collision checks
- Namespaces per project

Down the road:
- Overlay support (change a set of settings based on some context)
- Construct arbitrary user types from string
- Support multiple library instances with distinct settings in a single process
- Callbacks on setting updates

Reviewed By: aary, mnv104

Differential Revision: D6217956

fbshipit-source-id: 7c03d79c7601ce7b266df78e62b7193712d8331e

Summary: This diff change the `FOLLY_USE_SYMBOLIZER` gates to check for a value of `1`.

Reviewed By: yfeldblum

Differential Revision: D7471272

fbshipit-source-id: 74dbb4d56e1adc56ec75af5b4950ca2c027851cc

Summary:
We used `link_whole` to make sure the `setStackTraceGetter` constructor is
always linked when using Singleton's to setup symbolizer for stack traces.
However, using `link_whole` means we always link in the singleton library, even
if it's never used.

This diff merges `SingletonStackTrace.cpp` into `Singleton.cpp` to avoid the
need for `link_whole` and to link the former if and only if we use the latter.

Reviewed By: pixelb

Differential Revision: D7230733

fbshipit-source-id: de9be51a4eefee201563523d25800ab19ea777e3

Summary: These were being mangled as C++ functions rather than C functions.

Reviewed By: yfeldblum

Differential Revision: D7462668

fbshipit-source-id: e4e83e16aafad3d888599dd78bdbb4ac2711ad7f

Summary: It's unused, remove it.

Reviewed By: yfeldblum

Differential Revision: D7462683

fbshipit-source-id: 604c5691d69f2576c83c25350d29515efbc77a7b

Summary: `timespec` is defined in `sys/time.h`, so don't rely on `<chrono>` including it.

Reviewed By: yfeldblum

Differential Revision: D7462731

fbshipit-source-id: 590954e2230a0da322e2f5eb966bb49b18aa56f7

Summary:
Add API to AsyncUdpSocket to support three options on the socket.

- SO_RCVBUF and SO_SNDBUG options are responsible for the size of the queues that contain received and sent messages, respectively.
- SO_BUSY_POLL sets the approximate time in microseconds to busy poll on a blocking receive when there is no data

Details in socket man: http://man7.org/linux/man-pages/man7/socket.7.html

Reviewed By: yfeldblum

Differential Revision: D7372123

fbshipit-source-id: 5fd92489cbe86879d63df208c3821febdadb0020

Summary: MSVC calls this out explicitly as a non-standard cast and errors.

Reviewed By: yfeldblum

Differential Revision: D7451404

fbshipit-source-id: 9261b15fdc47b6ffbc1b53e83cbfbe9f9af894a9

Reviewed By: ouj

Differential Revision: D7424982

fbshipit-source-id: 3190564d3e79d10d7d64c1822a53e058a201f87d

Summary:
Remove hazptr_obj_batch feature.  Not required after D7429494:

After timer runs out, *all* thread caches are cleaned up, not just the current one,
so it should be safe to push anything to local thread cache, even if thread isn't used often,
as long as *some* thread is used.

Reviewed By: magedm

Differential Revision: D7433978

fbshipit-source-id: 01508fd199fcd267550efc08d2695b53f1569c84

Summary:
Continued reclamation issues from lots of UnboundedQueue batches, or lots of threads.

In addition to the current number of outstanding objects, cleanup *all threads* on a timer
basis.

Reviewed By: magedm

Differential Revision: D7429494

fbshipit-source-id: 7e9bdae9ae49927ca0b6e3f24963a4d4b23a4f0b

Summary:
I would like to store a folly::Poly I'm defining in an ordered
container (boost::containers::flat_set). While I could implement operator<
for exactly my type, it seems nicer to add it as another interface all
Poly users can reuse.

Reviewed By: ericniebler

Differential Revision: D7415861

fbshipit-source-id: 1912eaa009acea5c243db3e14fc0715a0829f251

Summary:
[Replaceable] Move `Replaceable` mixin param defaults to base template.

Saves a few lines overall.

Reviewed By: WillerZ

Differential Revision: D7421561

fbshipit-source-id: f56d1ffdd081b0a8a20cb7a492f06c9647445782

Summary: This check is causing some issues in github commits. Figuring out exactly which versions of 4.9 have the bug is a pain, so let's just get rid of it. See D6695110 for more context.

Reviewed By: yfeldblum

Differential Revision: D7431713

fbshipit-source-id: 17d1b025edf52592495c5f69c5a15025b33b3895

Summary: Windows doesn't have a nice function to do this, so we have to do it ourself, throwing the right exception with a struct that no public header defines, because Windows.

Reviewed By: akrieger

Differential Revision: D5100900

fbshipit-source-id: 4f6840e50c5c1aef36adade098739201c97b9af7

Summary: Actually remove it. All uses of it (outside of thrift) were removed in the previous diff.

Reviewed By: ot

Differential Revision: D7422614

fbshipit-source-id: 6a59c34b3cbc0ee7c50f8cbf8c5e641352f2db1a

Summary:
There is a missing `#include <ostream>`.  Add it.
Closes https://github.com/facebook/folly/pull/807

Reviewed By: shixiao

Differential Revision: D7425693

Pulled By: yfeldblum

fbshipit-source-id: cb645f7da94ca5fe5f8d4314b99621557109f360

Summary:
Python is considered a Safe Enivronment, where things like aborts and segfaults
can not happen.

If clients where used outside of "async with" we use to print a error message
and then C++ would abort.

This fix makes sure C++ no longer aborts but we still print the message
that the "async with" should be used.

All futures are now shielded so cancel will not produce strange exceptions when
C++ decides to fullfill the canceled future.

Also we now pass a tuple of client and future to all bridgeFutureWith calls.
This has the affect of making sure the client can not GC before the future
is completed.

We now use a unique_ptr for RequestChannel so there is no more race to delete
the shared pointer.

Reviewed By: yfeldblum

Differential Revision: D7389380

fbshipit-source-id: 6a3ca019190907e726c550c9b379a2a2610d0b0a

Summary: `-Wextra-semi` became more strict. This fixes folly build with the latest clang.

Reviewed By: yfeldblum

Differential Revision: D7359992

fbshipit-source-id: ce7caf05aa536f35e9af4ed33a86072afd09f387

Summary: Revert changes accidentally slipped into D7405057.

Reviewed By: yfeldblum, Orvid

Differential Revision: D7419691

fbshipit-source-id: ab9bea3393eb33aa19b3009263a53ac91e30692c

Summary: folly::ThreadLocal already maintains this list for us.  Add an accessor in folly::SingletonThreadLocal, and use it

Reviewed By: yfeldblum

Differential Revision: D7264843

fbshipit-source-id: 45278f7a074e50b96b451437c327de5d6713363a

Summary: [Folly] Fix `retrying` when the policy throws.

Differential Revision: D7392852

fbshipit-source-id: 3cb1d19697f111bf19047dc382056b39ad241035

Summary: Every compiler we currently support supports the `[[deprecated]]` attribute, so use that instead.

Reviewed By: yfeldblum, ot

Differential Revision: D7405895

fbshipit-source-id: 541c537cd7a0be0d901378c0e79f5cd0f55b85e3

Summary: Adding more details to the documentation and a unit test which checks various executors.

Reviewed By: yfeldblum, djwatson

Differential Revision: D7410461

fbshipit-source-id: 2ae6926f43862ec45a06ff76dbacae681fe6feaa

Reviewed By: wqfish

Differential Revision: D7205067

fbshipit-source-id: 2236c132b2150e38da6d5a5c9970347320e19a60

Summary:
Fix "declaration of 'h' shadows a previous local [-Werror=shadow-compatible-local]"

(Note: this ignores all push blocking failures!)

Reviewed By: djwatson

Differential Revision: D7406485

fbshipit-source-id: f23548022a3ccb1f480c7265b11c31d2e2876fd4

Summary:
Due to a quirk in how MSVC does name resolution, if a default value is declared in the forward declaration of a template, and the definition is made available in the same unit, the default values in the forward declaration must use the names given in the definition, not the declaration.
To keep it sane, just use the same template parameter names for both the declaration and definition.

(Note: this ignores all push blocking failures!)

Reviewed By: shixiao

Differential Revision: D7405057

fbshipit-source-id: dda14043fec30fa505bb0bb3e2e31d0abb52ba1f

Summary:
This diff adds a reverse iterator to F14VectorMap/Set; this is mainly useful because
if there have been no calls to erase(), the reverse iterator will visit the entries in
insertion order.

Reviewed By: nbronson

Differential Revision: D7173038

fbshipit-source-id: 0a64c4e753c9c36c6ac8b6141654b6f29f410580

Summary:
The layout of an exception_ptr is determined by the ABI, not the OS. MinGW (and
Cygwin, depending on the build settings) define `_WIN32` and would therefore
have `kIsWindows` be true, but they use the Itanium ABI instead of Microsoft's,
so we shouldn't take the MSVC codepath for them.

Unfortunately, there isn't a reliable preprocessor method to determine the ABI
being used. `_MSC_VER` can be defined even when using the Itanium ABI (e.g.
when using windows-itanium triples with clang), and `_MSC_VER` can be undefined
even when using the Microsoft ABI (e.g. when building with `-fno-ms-extensions`
with clang).

To address this, introduce `kMicrosoftAbiVer`, which defaults to `_MSC_VER`,
but can be overridden manually if necessary. This should do the right thing by
default most of the time, while providing an escape hatch for when `_MSC_VER`
would be incorrect to use directly.

Reviewed By: yfeldblum

Differential Revision: D7377853

fbshipit-source-id: dd868370e9a496b98dd26dec77c4a75c49147c3c

Summary:
Currently, `collectN` attaches a callback to each input future. When the callback fires, it calls `emplace_back` on vector `ctx->v` with the result of the future. As the added unit test shows, this does not work if the futures are completed in parallel.

See https://fb.facebook.com/groups/474291069286180/permalink/1838209692894304/ for more discussion.

Reviewed By: yfeldblum

Differential Revision: D7372982

fbshipit-source-id: 875eff19172bdbfb7d4f687911f4fa22061e4ed8

Summary:
`std::tuple` and `std::unordered_map` have long been standardized and supported by every platform we care about.
Beyond that MSVC is starting to remove the tr1 namespace entirely, so these references don't work under the newest MSVC.

Reviewed By: yfeldblum

Differential Revision: D7389783

fbshipit-source-id: c089490360ebf15ac23925f71e991602fda3d7a0

Summary: The nightlies for MSVC included support for std::launder, but the version that released with VS2017.7 Preview 2 doesn't actually support it. The version included in the preview also adds a macro to detect if it's been enabled, so use that.

Reviewed By: yfeldblum

Differential Revision: D7388311

fbshipit-source-id: 197230c9947cb271d6107d0cd5e905643e5589d1

Summary:
MSVC moves faster than boost updates, so it's not unusual to be building with an MSVC newer than the boost being used was able to be tested against. This causes Boost to emit a message at compile time for every compilation unit it is included in.
Luckly, boost provides a way out of the message, so add a config option to do so and enable it by default.

Reviewed By: yfeldblum

Differential Revision: D7388583

fbshipit-source-id: 8ecddc048df432df5200f4601e4121bdbd275220

Summary:
[Folly] Use C++ `thread_local` for fast-path cache in `SingletonThreadLocal`.

Because modules might be `dlclose`'d, use `static thread_local` rather than `static __thread` in the slow path which integrates the dtor into both `dlclose` and thread exit.

Because there might be multiple dynamically-loaded modules where the `static __thread` caches cannot be merged into a single cache, let all caches be tracked in a list. We have not found a case where this can happen while at the same time the `StaticSingletonManager` singleton does get merged, but this is at least not strictly wrong.

Reviewed By: djwatson

Differential Revision: D7316155

fbshipit-source-id: 0bf06638853ed70464856853349445d9fa6eabc0

Summary: Currently, initializing a `ThreadLocal` with 0 silently passes and then fails at a later stage making it very hard to debug what went wrong

Reviewed By: yfeldblum

Differential Revision: D7326627

fbshipit-source-id: dab62166753168e292f67938c52f82a1b610be2a

Summary:
Latest clang reported `-Wextra-semi` in `BOOST_MPL_HAS_XXX_TRAIT_DEF` uses with the trailing `;`. Codemod them away before the upgrade.
```lang=bash
fbgr -sl 'BOOST_MPL_HAS_XXX_TRAIT_DEF\(.*\);$' | xargs perl -pi -e 's,(BOOST_MPL_HAS_XXX_TRAIT_DEF\(.*\));$,\1,'
```

Reviewed By: yfeldblum

Differential Revision: D7383619

fbshipit-source-id: f7f9415617cf6d4a876ebe8bf782d0115cd01c23

Summary:
Compilation of basic sample from doc using VS2017 currently fails with:
```
C2327 'folly::ProducerConsumerQueue<folly::fbstring>::writeIndex_': is not a type name, static, or enumerator
```
Fixed it and updated the docs.
Closes https://github.com/facebook/folly/pull/806

Reviewed By: akrieger

Differential Revision: D7379931

Pulled By: yfeldblum

fbshipit-source-id: 6b7a72abd3324af56de355a6e65bdc7e1195596d

Summary:
Macro BENCHMARK_DRAW_LINE can be used as the following:
```lang=bash
BENCHMARK_DRAW_LINE()
BENCHMARK_DRAW_LINE();
```
This inconsistency was detected by `-Wextra-semi` in the latest clang. This diff removes the trailing `;` inside `BENCHMARK_DRAW_LINE` and updates all of the references.

```lang=bash
fbgr -sl 'BENCHMARK_DRAW_LINE\(\)' | xargs perl -pi -e 's,(?<!#define )BENCHMARK_DRAW_LINE\(\)(?!;),BENCHMARK_DRAW_LINE\(\);,'
```

Reviewed By: yfeldblum

Differential Revision: D7382525

fbshipit-source-id: 76f1da01bb4dde1b0fa4ebf98748d001d8e04ab0

Summary: As title

Reviewed By: yfeldblum

Differential Revision: D7379148

fbshipit-source-id: 6865940adee5899a055e1dac6b23705db2bc8ed7

Summary:
`iterator F14VectorMap::erase(const_iterator, const_iterator)` was missing a
conversion from `const_iterator` to `iterator`. This diff adds it as well as a
test. For sets, `iterator == const_iterator` so no need for anything special.

Perhaps we could save the roundtrip from iterator space to index space and
back using some const_cast of fancy pointers? The cost is going to be amortized
anyway...

Reviewed By: nbronson

Differential Revision: D7373152

fbshipit-source-id: 91f651b3e4a1314c68fb8809baeb1477f8881790