Summary:
folly::symbolizer now supports both DWARF4 and DWARF5 debug info
- http://www.dwarfstd.org/doc/DWARF4.pdf
- http://www.dwarfstd.org/doc/DWARF5.pdf

Split DWARF (Debug Fission)
- with `-fsplit-dwarf-inlining`: folly::symbolizer will use the debug info from the skeleton CU.
- without `-fsplit-dwarf-inlining`: folly::symbolizer won't read .dwo sections and can't symbolize it (yet).

Major things that changed between the standards that affect folly::symbolizer:
- new forms DW_FORM_addrx*, DW_FORM_loclistx, DW_FORM_rnglistx, DW_FORM_strx*, whose values are interpreted against new CU attributes DW_AT_addr_base, DW_AT_loclists_base, DW_AT_rnglists_base, DW_AT_str_offsets_base
- The .debug_line line header format is completely re-written and the constraint that the file register must be >= 1 was lifted.
- DWARF5 `.debug_loclists` replaces DWARF4 `.debug_ranges`

Differential Revision: D25521092

fbshipit-source-id: 5b48e8abed495f379d8b119177913f55ae11bd2b

Summary: This diff adds support to customize main branch name when generating GitHub Actions.

Differential Revision: D30679305

fbshipit-source-id: 0fc7eb1c97c27e2b42e60cc1ab69a48ab93b93fa

Summary:
Some changes that had to be done in Debian for the build to work:

* Installation of system deps failed as it was not detecting the OS correctly
* Updated the CMake manifest to uncomment the deb dependency as the CMake versions are newer
* fb303 was not getting cloned as it was looking for a non-existent master branch

Pull Request resolved: https://github.com/facebook/watchman/pull/943

Differential Revision: D30700180

Pulled By: fanzeyi

fbshipit-source-id: 62eb9f8ba57510eb98d6bd56e40384bf38a74d8c

Reviewed By: capickett

Differential Revision: D30712092

fbshipit-source-id: 642e642bab883259f177f4419a0c3d562c929beb

Summary: Part of folly vformat and svformat deprecation

Reviewed By: vitaut

Differential Revision: D30656958

fbshipit-source-id: 0cccb7b2294fada3c61e36cd527af2ef05bb5a0a

Summary:
Fix an algorithm bug that occurs when the Key or Value types are not nothrow copy constructible.
- Nodes (the entities protectable by iterators) may be cloned as a result of rehashing.
- Key-value item objects are unique (because they are not copyable).
- Multiple nodes may point to the same key-value item.
- In the incorrect algorithm, each node has a bool member that indicates if it owns the key-value item or not (i.e., if it is responsible for deleting it).
- When a node is cloned, its bool member is cleared.
- The problem is that if the key is erased and the clone (or  descendant clone) may be reclaimed (because it is unprotected by iterators) then the key value item will be reclaimed, even if a cloned-from node is still protected by iterators.
- The failure happens when an iterator holder to a cloned-from node tries to access the already-reclaimed key-value, expecting it (correctly) to be still protected.

The fix:
- Eliminate the bool owned member in the node structure.
- Add a link counter to the key-value item structure.
- Increment (atomically) the link counter when the (latest) node to the key-value item is cloned.
- Decrement (atomically) the link counter when a node pointing to the item is reclaimed.
- Reclaim the item only when its last link is released.
- Note that atomic increments  and decrements are used only if the node pointing to an item is cloned.

Added a test to detect the incorrect behavior.
This change fixes only the regular (non-SIMD) version.
Currently, the SIMD version fails the added test, therefore (for now) the test is enabled only for the regular version.

Reviewed By: davidtgoldblatt

Differential Revision: D30371519

fbshipit-source-id: 29e143712afb3ef794f9f6f4d99919d5b4688416

Summary: Add cFollyPromise method declarations that are needed to create an empty `folly::Promise`

Reviewed By: Gownta

Differential Revision: D30519790

fbshipit-source-id: 46092d5a400b0fccc11a9e77271a18b4f6fa3f6d

Summary: This ensures the token passed to child tasks continues to be signalled when the token applied to collect* is even after collect returns

Reviewed By: ispeters

Differential Revision: D30542448

fbshipit-source-id: b286175f4a8c5e5b3e2e628c6611f368ac79c1b6

Summary:
When compiled with `-Wcovered-switch-default`, Folly fails to build because it adds `default` to switches which are already exhaustive. For C++ safety, these switches are intentionally including a default, so wrap them in a pragma block to indicate that and locally disable the warning.

Causes -fmodules import issues for upstream library in D30379442.

Still remaining issues with C++ definition: P445339268

Reviewed By: ispeters

Differential Revision: D30397871

fbshipit-source-id: adead9e01d0ba3b21c2e1446150cc6fed0f58602

Summary: The len and bytes functions only operate on the current IOBuf, so add some comments explaining it.

Reviewed By: nanshu

Differential Revision: D30501776

fbshipit-source-id: 997dd77db52a3c11722efff8ae83b05e073e1285

Summary:
Fix SIMD version to return iterator to new item in insertion operations.

Added a test to detect the incorrect behavior.

Changed existing tests that di not test the SIMD version to do so. Three of these tests fail without the fix.

Reviewed By: davidtgoldblatt

Differential Revision: D30435627

fbshipit-source-id: 20ba400be9213fa138fda06e0e7bd84cf9d8cf12

Summary: I noticed two mispellings while reading through the code.  This fixes them.

Reviewed By: Orvid

Differential Revision: D30429734

fbshipit-source-id: b976cc4ae4534a9f065b8a7e6fee5a39d7241a28

Summary: This definition is the same cython uses for make_shared and make_unique

Reviewed By: yfeldblum

Differential Revision: D30232407

fbshipit-source-id: 6a0cf4637721bc9d5e5f7f87f3c0f2b031810a5f

Summary:
Original commit changeset: 7b10cb9dd2c4

`configerator_proxy2` reports a big memory regression. Reverting until we understand what's going on and have a plan to address it.

(Note: this ignores all push blocking failures!)

Differential Revision: D30401909

fbshipit-source-id: 28443ba08b75c634021965319fead2f8a36b7235

Summary:
Implements step 13 of ["Adding a new version of an existing project"](https://www.internalfb.com/intern/wiki/Third_Party2/Usage/#adding-a-new-version-of)

Steps are:
1. Update `fbcode://third-party2/config.py` to use the new CLI11-2.0.0 version
2. `fbcode $> tp2_update_fbcode CLI11` (updated third-party2 symlink)
3. `fbcode $> tp2_config buckify CLI11` (updated symlink to third-party-buck)
4. `fbcode $> buckify_tp2` (added TARGETS & other metadata files to third-party-buck)

Differential Revision: D30286158

fbshipit-source-id: 2a0bd5c92f9022eda2ae3f24b757fd2120bfcd4d

Summary:
The LifecycleObserver already tracks connect() but does not notify on
connectError().  Follow the same pattern.

Note that we intentionally added this to AsyncSocket's LifecycleObserver
rather than AsyncTransport b/c AsyncTransport is not supposed to have
a concept of a 'connection'.  This is counter to the 'connect()' callback
that already exists in AsyncTransport::LifecycleObserver so marked a quick
TODO to remember to move that.

Reviewed By: bschlinker

Differential Revision: D28612132

fbshipit-source-id: cefa650bd007d48e38f9cb67bc9a82d322036d4c

Summary: This diff adds the manifest file for delos_core so we can build using getdeps.

Reviewed By: hanm

Differential Revision: D26011286

fbshipit-source-id: becb1a665a95f0d593072885c3ddfcf5c4403f51

folly | CppAttributes | Add portable version of FOLLY_ATTR_MAY_ALIAS, to allow for usage across compilers.

Summary: This attribute is GCC/Clang specific, allow portable usage, well, via portability header and custom define.

Reviewed By: yfeldblum

Differential Revision: D30296807

fbshipit-source-id: bf496574139f42b07a11d582dedf6bac733318ec

Summary: Reverts {D28111907 (https://github.com/facebook/folly/commit/f35ba916372e02d67781d1529b19d49300fa4070)}.

Differential Revision: D28121832

fbshipit-source-id: 12871812fa34d2ef7d33b91908ffcb5e0a44b1a9

Summary: [Folly] Cut an outdated comment in `FutureBase::thenImplementation`.

Reviewed By: LeeHowes

Differential Revision: D23493983

fbshipit-source-id: 497ab55c10fc6561abb8febf55828190916441f8

Summary:
The WorkersProvider can be used to collect OS thread IDs of all active
threads consuming tasks from the CPUThreadPoolExecutor queue. The
WorkersProvider::KeepAlive holds a read lock for the `osThreadIds_` list here to
block the active threads from exiting (they will need to acquire a wlock on the same list on exit)
while the observer captures the backtraces.
The actual logic to captures the traces in coming in a subsequent diff.

Reviewed By: mshneer

Differential Revision: D30133823

fbshipit-source-id: 5bcdc52c55077b53fe8ec3be6d2413cac4436125

Summary: When constructing a new AsyncSocket, we can use an already connected file descriptor, which we assign to the `fd_` member variable. We move this assignment from the constructor body to the constructor initializer list to avoid a situation where an observer is unaware of an attached fd because `fd_` was assigned after the observer was created.

Reviewed By: yfeldblum

Differential Revision: D30261699

fbshipit-source-id: 5adbc744715355fba08f5430a77c9094e246899d

Summary: `BasicDynamicTokenBucket` declares a copy constructor, but not copy assignment operator.

Differential Revision: D30258099

fbshipit-source-id: c993177e11023d13d01884e5060269c4d5813088

Summary:
Fix flaky test. Without this fix it is possible for the background asynchronous reclamation thread to be too slow in pushing p1 into the cohorts safe list before the main thread checks for p1's reclamation.

This fix lets the main thread wait for p1 to be reclaimed before checking that p2 was not reclaimed. Since p1 is considered for reclamation before p2, it is possible that this check would pass even if p2 was about to be reclaimed in error. So the test then retires p3 and waits for it to be reclaimed before checking again that p2 was not reclaimed.

Reviewed By: yfeldblum

Differential Revision: D30248673

fbshipit-source-id: 268edb299681ab4b7256dac591d8cacbb960a7cc

Reviewed By: yfeldblum

Differential Revision: D30232471

fbshipit-source-id: 1137e306fca34f687c99c7f2155a03515926da45

Summary: This is unsafe and leads to all kinds of bugs. It is unfortunately too late to ban it, but we can at least print a warning to help debugging and maybe discourage new uses.

Reviewed By: yfeldblum

Differential Revision: D29972469

fbshipit-source-id: 1534bcc69eaf8f105998d65c0a6503740924cffa

Summary:
Fix a bug in hazptr_obj_cohort handling of children of reclaimed nodes during reclamation of the safe list. When the cohort is active, the children nodes should be pushed to the domain (to be checked against hazard pointers) and not reclaimed immediately because it is possible that a child node is protected by hazard pointers.

Added test that catches the bug.

Reviewed By: yfeldblum

Differential Revision: D30170939

fbshipit-source-id: e5bfe46b6fa5d4e5ce5cef02a3934ced424138f0

Summary: We update the TcpInfo namespace to `folly` (previosuly `folly::tcpinfo`) to avoid introducing unnecessary namespaces and to make it slightly easier to refer to. We also move the structs in the `TcpInfoTypes.h` file to the `folly::detail` namespace and move `LookupOptions` to the `TcpInfo` class, following comments in D22134355 (https://github.com/facebook/folly/commit/68a78d99d10743b54d38a550b2f0ebdc5c872f76).

Reviewed By: bschlinker

Differential Revision: D30159429

fbshipit-source-id: 7260fc80c2e76b3439c539b65cc188b2e5517b24

Summary: `getTerminateCancellationToken()` is the public API that can be used to get a cancellation token that'll be cancelled when any of the registered signal (SIGTERM or SIGINT) is received.

Reviewed By: andriigrynenko

Differential Revision: D29883069

fbshipit-source-id: 4270c42316b80afb2c75f54de7e720dcb7a083ca

Summary: Allow this to be used by more utilities.

Reviewed By: DurhamG

Differential Revision: D29958512

fbshipit-source-id: b6a1a7017102a4ff4ad252246d3252903bbb793f

Summary: Even when RTTI is disabled, to avoid unused-arg warnings. Then use `FOLLY_TYPE_INFO_OF` to simplify the conditional compilation in `UniqueInstance`.

Reviewed By: praihan

Differential Revision: D30183405

fbshipit-source-id: 040d90751822dedb8faca561a89dcf35da25119b

Reviewed By: yfeldblum

Differential Revision: D30191509

fbshipit-source-id: 00e782bf381bd5cb126fd7b18ee3454c6b9d13a7

Summary: The fdAttach callback notifies all AsyncSocketLifecycleObservers attached to the socket that a file descriptor has just been associated with the socket. In AsyncSocket, the file descriptor is created when connect() is **called**, not when it succeeds. This callback lets observers know about the fd immediately; otherwise, observers would have to wait until the connect succeeds to learn about the file descriptor attached event.

Reviewed By: bschlinker

Differential Revision: D29910574

fbshipit-source-id: c452f1091c657a7d118b1e06546555aa04a34bf1

Summary: Allows us to serialized and unserialize StreamingStats.

Reviewed By: yfeldblum

Differential Revision: D30108179

fbshipit-source-id: 7a920acfa10e6c16613e9059049b8550478e81f0

Summary:
This is a follow-up on https://github.com/facebook/folly/issues/1594

Pull Request resolved: https://github.com/facebook/folly/pull/1628

Differential Revision: D30179861

Pulled By: yfeldblum

fbshipit-source-id: 8949cd95e089a14f0ee63b784cecebe93c473607

Summary: To match the behavior of non-erased unique_ptr

Reviewed By: yfeldblum

Differential Revision: D30160280

fbshipit-source-id: 7fc624fa973c5cc1effc1746b5bee6c835d28150

Summary:
Original diff D29248955 (https://github.com/facebook/folly/commit/6f4811eff3b7472347cc34c0ac9876ddd96287fc) had a bug that was causing a memory leak and was reverted.

This diff reapplies it but with an extra fix.

Reviewed By: yfeldblum

Differential Revision: D30082935

fbshipit-source-id: 0f119189fe631fc363dffe5c515a8bfa9a054cf6

Summary:
In order to collect backtraces of all threads consuming from the executor's
queue(s), we need to record their actual thread IDs. We can keep track of the IDs
in a list owned by the executor. Each thread in the pool will add its own
thread ID to the tracking list by calling `folly::getOSThreadID()` and is also
responsible for removing it from the list as it exits.

Reviewed By: yfeldblum, mshneer

Differential Revision: D30103988

fbshipit-source-id: c59a1c31811684974fdb238433bd4796d0bbf2c8

Summary:
The existing FanoutChannel construct takes in an input receiver, allows the creation of output receivers, and broadcasts all received values to the output receivers. It is good for the scenario where you already have an input receiver that you want to forward to multiple output receivers.

However, for the scenario for which there is no existing input receiver, it is a bit heavy weight. To use it in this scenario, you have to create a separate channel, pass its receiver as the input receiver to the FanoutChannel, and write values to the sender.

In addition to having to create a separate input channel that is otherwise unnecessary, it is not optimized for the case where there is a single output receiver. In many cases, there is typically only one output receiver. It would be ideal to have a construct that uses the same amount of memory as a simple channel, in the case where there is only one output receiver.

FanoutSender solves both of these problems. FanoutSender does not require an input channel, and instead allows one to directly write values to all output receivers. In addition, in the case where there is only one output receiver, it uses exactly the same amount of memory as a simple channel.

Reviewed By: aary

Differential Revision: D29896797

fbshipit-source-id: 18178f42364d53e84fb07424ed3e8cc0497e21e1

Summary:
In order to colect backtraces from all threads consuming from a
task queue, we need the ability to expose their correpsonding thread IDs.
Here we introduce a new interface `WorkerProvider` which can be used to
collect the thread IDs. The implementations of this interface will come
later in the stack.

Reviewed By: mshneer

Differential Revision: D30101184

fbshipit-source-id: 24aaaeeba1983e3917c0224e94fc741b66a4f6a4