Summary:
gflags's pkg-config file is installed by default under the name gflags.pc; however, folly has been searching for it under the name libgflags.pc.

Several package managers (Homebrew, apt) install the .pc file under its default upstream name; as such it seems appropriate for folly to look for it under that name, too.

refs Homebrew/homebrew-core#7977.
Closes https://github.com/facebook/folly/pull/531

Reviewed By: yfeldblum

Differential Revision: D4348089

Pulled By: Orvid

fbshipit-source-id: 6adec290ec88b5d3f66103cf8e5094e99f2512ad

Summary: Test case ThreadLocal.SharedLibrary is failing due to looking for "thread_local_test_lib.so", while the actual .so generated is "lib_thread_local_test.so". Change Makefile.am to conform it.

Reviewed By: Orvid

Differential Revision: D4350758

fbshipit-source-id: 9a2a23325059ed71529821620398ffa6ed84f83e

Summary: This corrects an oversight in folly::Expected where self-assign was not being detected correctly due to a half-applied edit.

Reviewed By: yfeldblum

Differential Revision: D4348181

fbshipit-source-id: 710b25c4c6d7aeaaea50493ccc5788d875ec4c2e

Summary:
Fix a warning exposed by gcc's -Wshadow-compatible-local.

Rename inner "lockStolen" to "stolen".

Differential Revision: D4346385

fbshipit-source-id: 323cb6c96ecfe18b5540525f4124dbd75faf0b1b

Summary:
Fix a warning exposed by gcc's -Wshadow-compatible-local option.
Rename inner "i" to "j".

Reviewed By: knekritz

Differential Revision: D4346505

fbshipit-source-id: f0a4ac32fefd6614900e58d1c8c7f15e8934fd04

Summary:
This is a first diff to remove the "easiest" unused includes in fbcode.

* For safety, we only touch .cpp files without #if and #define,
* We do not try to remove redundant systems headers (aka. "packing").

The diff was generated as follows:
```
foundation/scripts/ls-cpp-dirs | grep -v '^\(\.\.\|external/\|.*/external\)' | xargs ffmr -o /tmp/ffmr-diff-1 codegraph/scripts/ffmr/analyze_includes_no_headers_no_packing_skipping_ifdefs.sh

cat /tmp/ffmr-diff-1/*.diff | patch -p2
hg commit -m something
arc diff --prepare --nolint --nounit --less-context --excuse refactoring
```

Note: `grep -v` is just an optimization. The actual configuration is in these two files:
diffusion/FBS/browse/master/fbcode/codegraph/analysis/config.py
diffusion/FBS/browse/master/fbcode/codegraph/scripts/ffmr/analyze_includes_no_headers_no_packing_skipping_ifdefs.sh

See the task for more context, and the recent "safety" improvements on the tool.

depends on D4317825 for very few cases where `nolint` had to be manually added.

Reviewed By: igorsugak

Differential Revision: D4312617

fbshipit-source-id: ecc1f0addfd0651fa4770fcc43cd1314661a311a

Summary: [Folly] Let `ScopedEventBaseThread` destruct the `EventBase` in the IO thread.

Reviewed By: andriigrynenko

Differential Revision: D4330951

fbshipit-source-id: 5b0e7071800e1d49048b08aa1233d72b820fe55d

Summary:
[Folly] Split `EventBaseThread` from `ScopedEventBaseThread`.

Now `ScopedEventBaseThread` is really scoped and immovable, while `EventBaseThread` is movable and can be started and stopped.

Users which will never move, and will never start or stop, the `ScopedEventBaseThread` can continue using it. Users which need to move, or which need to start and stop, the object will use `EventBaseThread` instead.

Reviewed By: andriigrynenko

Differential Revision: D4338447

fbshipit-source-id: 57c186630bc199a7a7b7223b1fcb077ce3d86743

Summary: More progress towards being able to build Folly cleanly with MSVC's truncation and sign coersion warnings enabled.

Reviewed By: yfeldblum

Differential Revision: D4288060

fbshipit-source-id: ce42d2099163ed5a9c9a9bb736a80bb2407f7595

Summary: In FunctionScheduler, cancelFunction and cancelAllFunction will not wait for current running function, which will lead to segmentation fault if the function captures resource to be destructed right after calling cancelFunction or cancelAllFunction. This diff introduces cancelFunctionAndWait and cancelAllFunctionsAndWait, making it possible to wait for completion of current running function.

Reviewed By: yfeldblum

Differential Revision: D4324384

fbshipit-source-id: ac4b272894f753ef3bb175173f10d1ca20c17c41

Summary: TimedMutex is a fair mutex, which can cause a deadlock if same mutex is requested first in a fiber, and then in main context.

Reviewed By: yfeldblum

Differential Revision: D4209155

fbshipit-source-id: 0623d9a2e6a0b5cc310fb71ad1b1cf33afd6a30e

Summary: BEXTR is an instruction in BMI set, which extract given number of bits from a 64 bit register starting from a given position. The position and size of extracted bits are packed into a one 64bit integer.

Reviewed By: Orvid

Differential Revision: D4316516

fbshipit-source-id: 3f752388763b0e26c506d7d49cf6c05cf28271c0

Summary: This reverts commit 8178dacc9268e1001efc5f803a35ef49e23d692a

Differential Revision: D4310312

fbshipit-source-id: 7c4b90e834f1a95e51524e1e82ac5294e5ba2dc5

Summary: [Folly] Always use an `EventBaseManager` with `ScopedEventBaseThread`.

Reviewed By: andriigrynenko

Differential Revision: D4336412

fbshipit-source-id: 459a679f8fda0db1ca0a9fdca2f852bb00c5231e

Summary:
Because it finds dead code.
This also removes the dead code found.

Reviewed By: yfeldblum

Differential Revision: D4310312

fbshipit-source-id: 8178dacc9268e1001efc5f803a35ef49e23d692a

Summary:
This allows folly to compile with warnings 4245, 4287 and 4365 enabled, all of which are sign mismatch warnings.
This is labeled as 'mostly' because I'll probably have to clean up a few more of these.

Reviewed By: yfeldblum

Differential Revision: D4263259

fbshipit-source-id: 0db618f0405817503a63094edd75b24ec1e5c9ad

Summary:
This makes the changes required to compile Folly cleanly with the rest of MSVC's truncation warnings, 4244 & 4267.
Only another 2800 sign mismatch warnings left to go.

Reviewed By: yfeldblum

Differential Revision: D4257094

fbshipit-source-id: 1651eca875a31f53774d36c682f5e2745ddfcda5

Summary:
This refactors folly/stats/* to use a single type for indexes rather than `size_t`, `int`, `unsigned int`, `uint64_t` and `int64_t` depending on where you looked.
This also has the result of getting MSVC to not complain about implicit sign conversions and implicit truncations.

Reviewed By: simpkins

Differential Revision: D4282174

fbshipit-source-id: 8529be34dce8ad18bc64395330bbdf2cd7305be4

Summary:
We were using `assert` without including anything that defines it.

Closes https://github.com/facebook/folly/issues/530

Reviewed By: yfeldblum

Differential Revision: D4337047

fbshipit-source-id: 327d19a685e7a4cc1e1eb6e471a6457fe9dee6c7

Summary:
[Folly] Check the baton waits in the `ScopedEventBaseThread` tests.

Also:
* `Baton<T>::timed_wait` can take a `duration`, not just a `time_point`.
* Allow a bit more time for waiting, just in case the machine running the tests is under load.

Reviewed By: andriigrynenko

Differential Revision: D4330126

fbshipit-source-id: 55878577b1deeb260686647e5f22a81d6fb9e06d

Summary: This makes it similar to other other events registered with EventBase.

Reviewed By: yfeldblum

Differential Revision: D4331277

fbshipit-source-id: 5d728d4ae5faff1a72ed724b4e2a6c0dd6c3b02d

Summary:
We use this in eden and this avoids needing to patch the homebrew recipe.

I've also made the use of the folly symbolizer specific to the facebook
internal build of folly, because it fails to compile in the Linux OSS build
too.

Reviewed By: yfeldblum

Differential Revision: D4292166

fbshipit-source-id: b69153be8ab9cc461bc7f456248e73972ba7f461

Reviewed By: yfeldblum

Differential Revision: D4331194

fbshipit-source-id: 1e1579e3b775b1b4e329aa28aae11a2b54294697

Summary: This fixes a deadlock possible when singleton chain is created concurrently with destroyInstances().

Reviewed By: lbrandy, yfeldblum

Differential Revision: D4329028

fbshipit-source-id: a11b3ff42d164ead2f8e3e77e0e17be43a8ad306

Summary:
GCC has the temerity to insinuate that my code has out-of-array-bounds access. After cross-checking with clang and ubsan, reviewing the code, and running constexpr tests (for which out-of-range errors are caught at compile time), I can say with pretty high confidence that this is an instance of GCC#61971 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61971). Basically, the gcc-4 series is known to issue spurious -Warray-bounds warnings. The "fix" is to route internal accesses to some helper functions, for which -Warray-bounds has been suppressed.

User code that accesses elements with operator[] will still warn on out-of-bounds access. If this is a problem in practice, we can suppress the warning there, too. Trying this for now since it is less likely to hide real problems.

Reviewed By: yfeldblum

Differential Revision: D4317305

fbshipit-source-id: 7bf92f993ac1a29631463c582c1b64d76f755181

Summary:
A recent diff added [[noreturn]] annotations that cause buck
build to fail for ExceptionTracerTest.cpp, due to our use of -Werror
and -Wunreachable-code-return.  This diff removes the unreachable return
statement.

Differential Revision: D4326888

fbshipit-source-id: 7863c163eedcf2a7e19730c1de194f05c544a2c0

Summary: If your function doesn't return you should be explicit about it.

Reviewed By: meyering

Differential Revision: D4309893

fbshipit-source-id: ce275ec8f42e2cb3253a1e40e263934649f09d9e

Reviewed By: yfeldblum

Differential Revision: D4323918

fbshipit-source-id: 8dcd4ef3629fff061a9f149093ef1fe087f1c7e2

Summary: Find and remove a couple of unnecessary includes

Reviewed By: matbd

Differential Revision: D4322316

fbshipit-source-id: 7b55119bd7566fd62762ace5e35aa536489fafad

Reviewed By: igorsugak

Differential Revision: D4320762

fbshipit-source-id: 2028de6ccc6fb129381b03d694b88677a5aa50d6

Summary: Allow observers to be notified when AsyncSocket attaches and detaches from EVB

Reviewed By: siyengar

Differential Revision: D4256175

fbshipit-source-id: a3ff96811f885e508f20cf11ce52e0f00e5ee461

Summary: The most common place this happened was in tests where it was being used to force the return type of a lambda, but there were a couple of places in the main code that triggered this as well.

Reviewed By: yfeldblum

Differential Revision: D4310187

fbshipit-source-id: e3701cff9827eacaf3be8d28296441466eb2fa11

Summary:
Moving russoue's `JemallocNodumpAllocator` (D3147173) from
`mcrouter` codebase to `folly`, so we can use it in a few other services
that suffer from a huge core dump problem.

Reviewed By: russoue, jmswen, luciang

Differential Revision: D4311394

fbshipit-source-id: 6a13c478b939bd411e0fd37e655125f62434c366

Summary: Adding new `addFunctionOnce` method that executes provided callback only once.

Reviewed By: yfeldblum

Differential Revision: D4315635

fbshipit-source-id: 4819ec30b4f2e4ab3185a37158404e1c7a96758a

Summary: Prior to C++14 these shifts are undefined behavior, but the unsigned version is not, so do the shifts on unsigned values before converting to the final type.

Reviewed By: yfeldblum

Differential Revision: D4309311

fbshipit-source-id: 914b207bac2f77a96c07a8a5df81980c672aa677

Summary: Which warns about the use of a ternary statement with the first operand omitted. This is a GCC extension and MSVC does not support it, so eliminate the last use of it.

Reviewed By: yfeldblum

Differential Revision: D4309989

fbshipit-source-id: 04c968708e47f8cb707fd0892e8780bc676df0de

Summary: They aren't needed and they count as initialized but unused variables.

Reviewed By: yfeldblum

Differential Revision: D4308844

fbshipit-source-id: a6833dbf434ebdefff0b375729a4e62495463ac0

Summary: Split out of an earlier pair of diffs, this focuses exclusively on Folly's networking APIs and works to eliminate places where values were being implicitly truncated.

Reviewed By: yfeldblum

Differential Revision: D4288042

fbshipit-source-id: dd6e19acd319296a45c29c8050dc62f06571e1e6

Summary: Because the `break;` can be dead, and sometimes is indicitive of a different type of error.

Reviewed By: meyering

Differential Revision: D4310056

fbshipit-source-id: ad215eb9b2e5bb4d5c703582203efce893b26a76

Summary: To monitor client support of TLS 1.3.

Reviewed By: ngoyal

Differential Revision: D4308473

fbshipit-source-id: cb6fb444c8b7ced39e6655a0f63b18523c2fb9c5