Summary:
[Folly] Fix `constexpr_min` after {D5739715} (facebook/folly@6d7c6d55f0f4b7b75607608ef9037db58083368f).

Add new unit-tests for `constexpr_min` and `constexpr_max` to avoid silly mistakes like this in the future.

It was defined recursively in terms of `constexpr_max` rather than, as intended, in terns of `constexpr_min`. HT Mandar12.

Reviewed By: Orvid

Differential Revision: D5761831

fbshipit-source-id: 2dad5833e05679232b3c529d33325a0205c2e4e4

Reviewed By: meyering

Differential Revision: D5757469

fbshipit-source-id: ad70c47251993c79a502d30f312534e28c9241d4

Summary: Fulfilling starts destroying the evb in another thread which races with the socket closing on the evb.

Reviewed By: siyengar, ngoyal

Differential Revision: D5755271

fbshipit-source-id: ace37eee63e684c97ca0fe503293eee83514e0ac

Summary: title

Reviewed By: yfeldblum

Differential Revision: D5751299

fbshipit-source-id: d3967c2499da9a2c98c2862b9bdc9994c12edc76

Summary:
[Folly] Extract non-portability `constexpr` math functions to new header.

This new header, `folly/ConstexprMath.h`, is specifically for compile-time-computable math functions. We start with `min`, `max`, `abs`, and `log2`.

Included substantive changes:
* Add new tests for `constexpr_strlen`, which remains in the portability header.
* Make `constexpr_min` and `constexpr_max` variadic.
* Make `constexpr_log2` tail-recursive, remove `const_log2` in `FixedString.h`, and move the related comment.

Reviewed By: Orvid

Differential Revision: D5739715

fbshipit-source-id: 29d3cc846ce98bb4bdddcc8b0fa80e4d32075fe0

Summary:
When trying to build with targets files on OSX, I couldn't use the symbolizer because it needs StackTrace, which requires libunwind and elf. This makes it so that we only build on linux for now. This also makes it so that we set FOLLY_USE_SYMBOLIZER in autoconf, since that wasn't set before.

Does a few things surrounding usage of the symbolizer library:
- Introduce FOLLY_USE_SYMBOLIZER in folly-config.h and USE_SYMBOLIZER as an AM definition
-- Filter some code out of init and some other random libs that optionally need the symbolizer
- Fix libdwarf detection. Previously on a fresh ubuntu container, we didn't find libdwarf/dwarf.h, so we stopped trying before looking at dwarf.h

Reviewed By: yfeldblum

Differential Revision: D5644352

fbshipit-source-id: f0a3580c41122e5e8fdfd17a9fdbb0921be21401

Summary: <array> is sometimes necessary for using `std::array`. Fix up

Reviewed By: aary

Differential Revision: D5740866

fbshipit-source-id: 13bafadd26fdd0f2eff3513115b43811682e7cda

Summary:
Code was breaking in versions of C++ where constexpr functions are
required to have one line bodies

Reviewed By: yfeldblum, mzlee

Differential Revision: D5739062

fbshipit-source-id: 6c509f1daf77751d33ce9c173a0d7f1d3bd2a006

Dynamic MPMCQueue: Eliminate cases of enqueue indefinite blocking and failure in the extensible version that impossible under the default pre-allocated version

Summary:
Currently under the extensible version (Dynamic == true), some enqueue operations may block indefinitely or fail (return false) even though such outcomes are impossible under the default (Dynamic == false) pre-allocated version.

This diff eliminates such cases by changing the algorithms for the extensible version. Some of the high-level changes:
- The offset formula for an expansion guarantees that no enqueue operation left behind in a closed array does not have an existing dequeue operation that unblocks it. The old formula was 1 + max(head, tail). The new formula is max(head, current offset) + current capacity.
- Conditional operations validate state after the success of CAS.

Reviewed By: djwatson

Differential Revision: D5701013

fbshipit-source-id: 4917c5b35b7e2a2fddfd2e11fb5aeb478502137c

Summary:
[Folly] `constexpr_log2`.

Useful for anything that needs to compute log2 at compile time.

Reviewed By: eduardo-elizondo

Differential Revision: D5734727

fbshipit-source-id: 8eab7991eea2104570eecd8e84ede6160bb0b549

Summary: [Folly] Shrink `MicroSpinLock.h` transitive includes and inline methods.

Reviewed By: meyering

Differential Revision: D5732693

fbshipit-source-id: 386816f0d97c145ff8a4180d41c8a682694aa6cb

Summary: This comment is outdated.

Reviewed By: yfeldblum

Differential Revision: D5730049

fbshipit-source-id: f6088c4354210fafb019656cdf8246abf90fbc06

Summary:
Before this change, future context will not be cleaned up until timekeeper times out. These objects has been occupying memory when more shorter future tasks are registered.
Switch to use weak ptr to hold context, so that context objects are deallocated as soon as the future completes (or times out)

Reviewed By: yfeldblum

Differential Revision: D5692040

fbshipit-source-id: b3b74a29b2ccafef6c4a06011699b069feb3a847

Summary:
Let clients choose whether to use fibers or not, but default
to the same autodetected setting as prior logic.

Reviewed By: yfeldblum

Differential Revision: D5585605

fbshipit-source-id: 9a4bf9f9bc23b4e15601f30c40602f21798c9685

Summary:
MSVC warns this might be used but uninitialized. Force
the struct to be zero initialized.

Reviewed By: yfeldblum

Differential Revision: D5585320

fbshipit-source-id: 9454a2a4a66c7689f42b1eb211dc57f5d3b88fea

Summary:
Off-by-one error in DIR::open() would result in paths not
ending in a trailing separator to fail to open. Fix the arithmetic.

Reviewed By: Orvid

Differential Revision: D5579657

fbshipit-source-id: 79507bc398549033eb26b2ffa788d66241deb623

Summary:
This implementation should suffice for MSVC. _ReadWriteBarrier()
generates no instructions but instructs the compiler not to reorder accesses
around it, and we have to rely on MSVC not currently having any other
optimizations for const members to worry about.

Reviewed By: yfeldblum

Differential Revision: D5723782

fbshipit-source-id: a68caa4673a5c410b326c1d2e3c0752bd945f4a6

Summary: [Folly] Apply `clang-format` to `folly/experimental/exception_tracer/`.

Reviewed By: Orvid

Differential Revision: D5722994

fbshipit-source-id: 2e52c920119ba58d123aaffd59491d7561c37c17

Summary:
This reverts commit 1744685ff9fa8d3620aef2545c8fe3ebc481df06

bypass-lint

Differential Revision: D5714883

fbshipit-source-id: 0cdb5f2cac095a9202cb1310ff8e75e75b4afd74

Summary: This enables the last of the magic internally.

Reviewed By: yfeldblum

Differential Revision: D5719795

fbshipit-source-id: fb59a0d7873e9a9f3b73f556b42b647091ca7e67

Summary: [Folly] Shrink `MicroSpinLock.h` transitive includes and inline methods.

Reviewed By: Orvid

Differential Revision: D5714883

fbshipit-source-id: 1744685ff9fa8d3620aef2545c8fe3ebc481df06

Summary: Currently FunctionScheduler calls that cancel/restart timer for a function of particular id are O(n). By introducing hashmap that translate id to pointer of particular RepeatFunc, we make it O(1).

Reviewed By: simpkins

Differential Revision: D5668557

fbshipit-source-id: e5e8bf9bd75b6d5d42f0bfa398d476703e5801fa

Summary:
The current definition of void_t was leading to errors because unused
template parameters are ignored and SFINAE SFIAEs

Reviewed By: yfeldblum

Differential Revision: D5700825

fbshipit-source-id: d23336070c217e8594980d6db710cb417b014236

Summary:
The flag FOLLY_FORCE_EXCEPTION_COUNT_USE_STD forces
the usage of std:uncaught_exceptions() for folly's
implementation of uncaught_exceptions()

Reviewed By: yfeldblum

Differential Revision: D5542302

fbshipit-source-id: 2c2f507ab9dde916a160a9c370a267cdcfd7203a

Summary:
- Throw exception if no forward progress was made with `StreamCodec.compress()` and `StreamCodec.uncompress()`
- Prevents infinite looping behavior when no forward progress was made
- Update tests

Reviewed By: terrelln

Differential Revision: D5685690

fbshipit-source-id: 969393896b74f51250f0e0ce3af0cd4fedcab49a

Summary: [Folly] Fix typo in `Function.h`.

Reviewed By: yfeldblum

Differential Revision: D5703550

fbshipit-source-id: 9dc09697fd09db6c65b1a4f2d8bdf44451b4aab2

Summary:
add public kSlotSize to IndexedMemPool,
needed to support getting the approximate memory footprint of the pool
(since a Slot has two atomic uint32_t's more than a bare Elem)

Reviewed By: yfeldblum

Differential Revision: D5690225

fbshipit-source-id: 667da6b67b339038b92b0e5acde17219fe1c85c5

Summary:
Try was missing some important-ish overloads that help it behave well
in rvalue contexts

Reviewed By: yfeldblum

Differential Revision: D5692021

fbshipit-source-id: c34627b56eb52dceaeb1f00ae930ee3bc6e00306

Summary:
unwrapTryTuple only accepted rvalue tuple types, this diff fixes that
to work with forwarding reference tuple types.

Also reduces the number of template instantiations

Reviewed By: yfeldblum

Differential Revision: D5682996

fbshipit-source-id: ee6dd2c20d8dfca33e769a98a6ca56fa96c73b72

Summary: Link local is not the only type of address that is based on mac address, therefore create generic function to extract mac address from EUI-64 autoconfigured addresses using the same logic as for getMacAddressFromLinkLocal

Reviewed By: pallotron

Differential Revision: D5697781

fbshipit-source-id: 4d69085a1d8f08e06496b8a9b638ac7ff31c6c3a

Summary: Reformatted the scripts and test files to look better and also to avoid lint warnings in the future

Reviewed By: andriigrynenko

Differential Revision: D5673856

fbshipit-source-id: 5818625ec14d18ef3b9b804df53949afefc3b98f

Summary:
- Replace LZMA2Codec with LZMA2StreamCodec
- Update tests to reflect LZMA2_VARINT_SIZE requiring data length

Reviewed By: terrelln

Differential Revision: D5625388

fbshipit-source-id: 3303c6dda5d41f40615c87504a46923815b0b716

Summary:
[Folly] `Try::exception` overload for `Try&&`.

For consistency with `Try::value`.

Reviewed By: WillerZ

Differential Revision: D5691758

fbshipit-source-id: 9904b2a5c90f4575a3c09dc012658d359d11fdd9

Summary:
`FOLLY_AARCH64` is more descriptive.
(searching for A64 tells you nothing, searching for aarch64 tells you a lot)

Reviewed By: yfeldblum, andrewjcg

Differential Revision: D5663075

fbshipit-source-id: 8f31fde4aa394f5452305929541af6d38e4d8a37

Summary:
the README didn't have explicit instructions for ubuntu 16.04 LTS...  now it does.

i also added a section for how to handle building folly w/a custom boost installation.
Closes https://github.com/facebook/folly/pull/664

Reviewed By: eduardo-elizondo

Differential Revision: D5694143

Pulled By: yfeldblum

fbshipit-source-id: e2786d045c3459cac49c8b052d90ca24d10f7922

Summary: Add a macro to enable optional scoped trace section functionality (user-defined). This macro will have no effect unless configured to do so. This change means that if proxygen is being upgraded, folly must also be updated.

Reviewed By: mzlee

Differential Revision: D5635123

fbshipit-source-id: 7db17f6ae8c0d1484cf9fad043eb42717279bd0a

Summary:
[Folly] Use simple `exception_wrapper` ctor in the `Promise::setException` test.

And add a new case testing with `exception_ptr`.

Reviewed By: andrewjcg

Differential Revision: D5683035

fbshipit-source-id: e8276166dacbe09a9a745271d636db44c593058c

Summary:
Adding a for_each function that allows generalized indexed and breakable iteration through ranges, these can either be runtime ranges (i.e. entities for which std::begin and std::end work) or compile time ranges (as deemed by the presence of a std::tuple_length<>, get<> (ADL resolved) functions)

The function is made to provide a convenient library based solution to the proposal p0589r0, which aims to generalize the range based for loop even further to work with compile time ranges

A drawback of using range based for loops is that sometimes you do not have access to the index within the range.  This provides easy access to that, even with compile time ranges.

Further this also provides a good way to break out of a loop without any overhead when that is not used.

A simple use case would be when using futures, if the user was doing calls to n servers then they would accept the callback with the futures like this

   auto vec = std::vector<std::future<int>>{request_one(), ...};
   when_all(vec.begin(), vec.end()).then([](auto futures) {
     folly::for_each(futures, [](auto& fut) { ... });
   });

Now when this code switches to use tuples instead of the runtime std::vector, then the loop does not need to change, the code will still work just fine

   when_all(future_one, future_two, future_three).then([](auto futures) {
     folly::for_each(futures, [](auto& fut) { ... });
   });

Reviewed By: yfeldblum

Differential Revision: D5557336

fbshipit-source-id: 79fcbafa7e1671f8856f0dcb7bf7996435dadeaa

Summary:
Even though MockAsyncSSLSocket's initializes AsyncSSLSocket, which should
initialize AsyncSocket, this does not actually happen because AsyncSSLSocket
virtually inherits from AsyncSocket.

Because of this, prior to this diff, the MockAsyncSSLSocket was not properly
setting its EventBase.

Reviewed By: knekritz

Differential Revision: D5676596

fbshipit-source-id: 5f3c0e848179cb5eb4d2dc4921a11e7c04d7c0e0

Summary:
[Folly] Use `exception_wrapper::from_exception_ptr` in `Try` and `Promise`.

It does just what we need; DRY.

Reviewed By: andrewjcg

Differential Revision: D5674663

fbshipit-source-id: 73e46df62c06736c4eaf013d05dfea819cbec515