Summary:
As mentioned in D30901400 (https://github.com/facebook/folly/commit/b258ee31860b47b9196872264f6f3a331d450b1f) / OSS commit b258ee31, `folly::Subprocess::CLOSE` has implications that are rather suboptimal in real-world use.

To recap, opening a socket or file will use the lowest unused fd number, meaning that if we close stdin/stdout/stderr they can be replaced by a random file or socket. This may result in unexpected behaviour.

Reviewed By: luciang

Differential Revision: D30991108

fbshipit-source-id: 9055af84423500a1896015b5fe866ceb2cc64186

Summary:
There's no compelling reason I could uncover why someone with a const folly::LogCategory* shouldn't be able to get the propagation level, so I'm marking this method as const to allow for that.  This makes the method more consistent with all of the other get methods in the class.

For example, if one gets the category configuration map through getCategoryConfigs(), the map returned is const.

Reviewed By: yfeldblum

Differential Revision: D31066791

fbshipit-source-id: 46267ae7bb950fbd1b3c3d8b032ed2491d54e446

Summary:
Added code to skip some TFO unit tests if the kernel tcp_fastopen setting does
not support the test.

Reviewed By: mingtaoy

Differential Revision: D30937011

fbshipit-source-id: 6973897445a87744686ed568cb0c0c755faa46c3

Summary:
So that if `std::chrono::steady_clock` and `folly::chrono::coarse_steady_clock` have the same spec, time points from the two clocks are compatible.

The intention is to provide a generic interface to determine whether it is safe to interpret a time-point from one clock as a time-point from another clock.

For example, it is safe to interpret a time-point from the coarse-steady-clock as a time-point from the steady-clock, and the code marks this by giving both clocks the same spec tag, but it is not safe to interpret a time-point from the system-clock as a time-point from the steady-clock, and the code marks this by giving the two clocks different or void spec tags.

Concrete code can already do this at will. The idea is to have a generic way to do this, from within an algorithm templated over all the clock types and having no special knowledge of any clock type.

Reviewed By: simpkins

Differential Revision: D29222091

fbshipit-source-id: b9442acd08716a46e704b6d800cc1cd1d0583e25

Summary: Rather than having coarser `duration` types, the only purpose of which is signalling coarseness via a hijacked channel.

Reviewed By: simpkins

Differential Revision: D29221055

fbshipit-source-id: 025a8b94972ee77a7d4a5bd34f269c492aaf2c4e

Summary:
Returns the RequestContext object if it already exists. Uses
SingletonThreadLocal::try_get() underneath.

Reviewed By: mshneer

Differential Revision: D31046069

fbshipit-source-id: 0d1b7af870494b70d890d0b8ef9cf0b89ac67ccc

Summary: As title.  So things can return non-void from the function

Reviewed By: yfeldblum

Differential Revision: D31038691

fbshipit-source-id: c8a499ffe7e2451cc11dbfb3f7e6e49591a6444c

Summary: This diff changes the users of FanoutChannel to use the context functionality added in the previous diff. It includes a new helper class in falcon/proxy called ProxyNotificationFanoutChannel, which handles updating the current version and sending an initial NewSubscription to new subscribers with that version. This diff then changes ProxyCache, ProxyProdEntity, OverriddenBlobEntity, and OverriddenMapEntity to use ProxyNotificationFanoutChannel. (Previously, the logic in ProxyNotificationFanoutChannel was duplicated in all 4 of those classes.)

Reviewed By: aary

Differential Revision: D30889895

fbshipit-source-id: 39c9167f2bc6cc51e0b089eb5382faa498ffcb89

Summary:
One common pattern with FanoutChannel is to send to new subscribers an initial update indicating the current state of the stream. This is currently the pattern for all uses of FanoutChannel.

This pattern is currently accomplished by adding a transform to the input receiver before passing it to fanout channel. The transform updates the current state of the stream in some shared state object. That shared state object is then captured and used in the getInitialValues function passed to subscribe, in order to let new subscribers know the current state of the stream.

However, this approach can lead to a race condition. In this approach, the transform function is executed (on the transform executor) before the getInitialValues function is executed (on the FanoutChannel executor). If someone adds a new subscriber in between, getInitialValues will use the updated shared state, even though the corresponding update has not yet been sent from the output of the transform to the input of the fanout channel.

To solve this race condition, we need to ensure that new subscribers are not added between the shared state change and the fanning out of the update that led to the shared state change. To do this, this diff adds explicit support for a custom context object that can store state. The context object's update function is called on every update, allowing the shared state to be updated on each new value. The context object is also accessible to the getInitialValues function, which allows sending an update with the current state (based on the context) to new subscribers.

This enables the desired pattern without a race condition, and avoids the need for a transform.

Reviewed By: aary

Differential Revision: D30889893

fbshipit-source-id: 9a79fd5a823db1ae477b6b63170978925b791dda

Summary: This diff renames getNewReceiver/anyReceivers to subscribe/anySubscribers.

Reviewed By: aary

Differential Revision: D30889890

fbshipit-source-id: 8c3d8b1b1e930a703b5ce40e05ee129531af255e

Summary:
FanoutSender is like FanoutChannel, except that instead of listening to and fanning out values from an input receiver, it allows values to be directly pushed into the sender.

This diff changes FanoutChannel to use FanoutSender, increasing code re-use. FanoutChannel now listens to values from the input receiver, and pushes them into a FanoutSender.

Reviewed By: aary

Differential Revision: D30889891

fbshipit-source-id: 6d2ae416a5a0a895a1b1269d21f6830d45d92184

Summary: This diff changes TValue to ValueType in FanoutChannel (adhering to the folly guideline of not prefixing template parameters with T).

Reviewed By: aary

Differential Revision: D30889892

fbshipit-source-id: 2ef79620289d554c9802124426d3c4ac70a06f12

Differential Revision:
D31006847 (https://github.com/facebook/folly/commit/865e847605911ed0eab96a0170fc372d09c3de5c)

Original commit changeset: 2ce67a097c07

fbshipit-source-id: 1bd09fcd6233f8c88969856c47317fbe8c197754

Summary:
Returns the `RequestContext` object if it already exists. Uses
`SingletonThreadLocal::try_get()` underneath.

Reviewed By: yfeldblum

Differential Revision: D31006847

fbshipit-source-id: 2ce67a097c07de10b4359e3e70b820b80d885117

Summary: as in title

Reviewed By: yfeldblum

Differential Revision: D30966043

fbshipit-source-id: aebe6972edfab79d610d01edcb737bd6102aa364

Summary: Fixes an improper cast. `SingletonThreadLocal` allows a factory which returns any type, as long as that type can be reference-cast to the target type. So the new code must do a reference-cast.

Reviewed By: amlannayak

Differential Revision: D31022770

fbshipit-source-id: 0fce6008fc3e21b6082ec7dcf3c3f9019b541ae9

Summary:
We already have this functionality for Digest part.
Let's add it for Hmac.

Reviewed By: yfeldblum

Differential Revision: D30879080

fbshipit-source-id: de6feb7aa5f6fa41f9595f00c8fa4cf3087719af

Summary: Accesses the per-thread singleton if it has already been created.

Reviewed By: amlannayak

Differential Revision: D31003518

fbshipit-source-id: 959418c4bc81da2b0ab7c639cdddb6d0beaf0121

Summary:
It's possible that AsyncTransport read completed successfully in one loop, then the read coro gets a cancellation request.  In this case, prefer to return successfully with the read data.

Read cancellation need not be fatal, eg: an application may just want to interrupt a read and come back to it later.  In this case, the successfully read data could be lost.

In particular, if an EOF was lost, the application might start another read, AsyncSocket::setReadCB can assert in invalidState(ReadCallback*) because the DestructorGuard count is 0.

Reviewed By: yairgott

Differential Revision: D30964504

fbshipit-source-id: ea963e6572f2bb552899d3b1e6274bbd0bcdc265

Summary: Added the bytesAcked field in TcpInfo to represent the number of acknowledged bytes in the connection.

Reviewed By: bschlinker

Differential Revision: D30511022

fbshipit-source-id: 6056c741399a058811fee0dbd94b1722c802db13

Summary: These warnings appear when compiling with Clang modules. In this case, the `default` case should never be hit regardless of user input, so we may translate this to an unreachability hint.

Reviewed By: yfeldblum

Differential Revision: D30962081

fbshipit-source-id: 48914f79a8d40f597cb60b8d8d6d9af37ac4b655

Summary: See title.

Reviewed By: yfeldblum

Differential Revision: D30923907

fbshipit-source-id: 8cbe749fa4662a171a247c8c16f6b9bc7b587e30

fix self-assignment for OpenSSLHash::Digest, throw if context allocation fails, implement move support

Summary:
The copy assignment operator was not checking for self-assignment, which means the code was wrong when an object was being copied into itself.
Also, allocation failure in the constructor would be silently ignored and result in a segfault crash later. Throw std::runtime_error if OpenSSL context allocation fails.
Also, move constructor and move assignment operator were not implemented - they are now.

Reviewed By: yfeldblum

Differential Revision: D30879545

fbshipit-source-id: 8b06f6fe97912a03ec5480a3b7c69aebf3a7f2ca

Summary:
It's somewhat common to want to ignore `stdout` / `stderr` when spawning a child, and the current mechanism we provide to do this is `folly::Subprocess::CLOSE`.

However, this is somewhat dangerous when used without care, since any new files or sockets the child process opens will take on these low fds. From `man 2 open`,

> The file descriptor returned by a successful call will be the lowest-numbered file descriptor not currently open for the process.

Note that stdin/stdout/stderr are *not* special-cased here.

To provide a safer way to not inherit or pipe the standard fds, provide a `folly::Subprocess::DEV_NULL` option instead, which hooks up the OS-relevant null device to the fd.

`folly::Subprocess::CLOSE` will subsequently be removed.

Reviewed By: yfeldblum, luciang

Differential Revision: D30901400

fbshipit-source-id: 0b59de5da6c6a0f714233c09788fa2d0020f3823

Summary:
This change updates the CMake config to detect whether GCC's `-fcoroutines` flag is supported and enable it for the build. This is required to enable support for Folly coroutines.

Followed the instructions in GCC page about C++ coroutines to get them enabled.
https://gcc.gnu.org/wiki/cxx-coroutines

NOTE: This Wiki page used to indicate that exceptions had to be disabled to enable subroutines, but this only applied to experimental support for coroutines and it's no longer the case.

This was uncovered by the fbthrift build, which needs Folly coroutines to implement streaming. A new fbthrift test using a stream type uncovered this missing feature in our build on Fedora.

Reviewed By: yfeldblum

Differential Revision: D30026779

fbshipit-source-id: 3324c2fc52fe5db793bdaba9c81f41bfe6ef2242

Reviewed By: vitaut

Differential Revision: D30676171

fbshipit-source-id: f820b1c08750c4d844925a82d5fd710bc8a1ca5c

Summary:
Rearrange invoking asynchronous reclamation in executor.

Eliminate the LOG message about skipping asynchronous reclamation.

Reviewed By: yfeldblum

Differential Revision: D30908286

fbshipit-source-id: ee79714bf8e6253a01d04c6d2ffa81895c4133c8

Summary:
`FOLLY_HAS_STD` and `FOLLY_HAVE_STD` are now `FOLLY_HAVE_SDT`.

This typo reveals that the tests aren't run on platforms that don't have this feature enabled :/

Reviewed By: yfeldblum

Differential Revision: D30780817

fbshipit-source-id: 338fdd5e5b08f3b5347609dd783f0a75506f9e30

Reviewed By: yfeldblum

Differential Revision: D30914679

fbshipit-source-id: 79a609ed1eda97a97e6eeeb47038a1e746b75e2d

Summary:
This is useful if we want to bind to a nonlocal address or an address that doesn't exist yet.

       IP_FREEBIND (since Linux 2.4)
              If enabled, this boolean option allows binding to an IP
              address that is nonlocal or does not (yet) exist.  This
              permits listening on a socket, without requiring the
              underlying network interface or the specified dynamic IP
              address to be up at the time that the application is
              trying to bind to it.  This option is the per-socket
              equivalent of the ip_nonlocal_bind /proc interface
              described below.

Reviewed By: yfeldblum, mjoras

Differential Revision: D30903919

fbshipit-source-id: 09058cac1c14a4003525b0a7c5381ea301ca28da

Summary: Adds a new method `co_schedule()` that takes a task, schedules it on the current executor and adds it to the AsyncScope.

Reviewed By: andriigrynenko

Differential Revision: D30005811

fbshipit-source-id: 48c7aa240dc73c0b4dd54e539e620cf69c68c4fd

Summary:
From documentation in https://linux.die.net/man/2/ftruncate
> The file offset is not changed.

Reviewed By: Orvid, Skory

Differential Revision: D30843563

fbshipit-source-id: 9314576d927d9ddc07df6d0ceae394d148d7af94

Summary: getdeps.py pulls repos from master branch by default. For FBOSS force it to pull from 'main'

Reviewed By: shri-khare

Differential Revision: D30857755

fbshipit-source-id: 9891f1ddc08c8f13bdcb00385e1ad4516a84776c

Summary:
std::vector<bool>::iterator::operator* returns a temporary proxy bool accessor
in many implementations.  So range-based for loops over it don't work if we
assume non-const lvalue-ref binding, eg.
```
for (auto& ref : vectorBools) { ... }
```
Won't compile.  Silly std::vector<bool>.

Reviewed By: SmithAndr

Differential Revision: D30833990

fbshipit-source-id: cb8d53a48eb2a40587911ad2f0c50b99a472a59c

Summary: Shard the domain's list of untagged retired objects.

Reviewed By: davidtgoldblatt

Differential Revision: D30806913

fbshipit-source-id: 93061ebcd3f62c49eb0f96193e5961c4eeb6f061

Summary:
Consolidate retired_, the list of non-cohort retired objects, with untagged_, the list of cohort untagged objects, in the domain.

Eliminate redundant functions.

Reviewed By: davidtgoldblatt

Differential Revision: D30806882

fbshipit-source-id: bdcbc4990a3d114f7f6bea294df498c5743bed43

Summary:
Remove hazptr_priv, the thread-local list of retired objects.

Non-cohort retired objects are pushed directly into the domain.

Reviewed By: davidtgoldblatt

Differential Revision: D30806863

fbshipit-source-id: 526c90f5a198b4e42a55062cb7344e5286bf28fd

Summary:
The primary branch in the GitHub wangle repository has been renamed from
`master` to `main`.  Update the getdeps manifest to reflect this, so that
getdeps builds correctly clone the repository.

Reviewed By: xavierd

Differential Revision: D30822418

fbshipit-source-id: 9670fff1e85e77adf84485ff8f2236f8826630ef

fbcode: symbolizer: clang-12 DWARF5 emits Split DWARF inlining as DW_TAG_skeleton_unit instead of DW_TAG_compile_unit

Summary:
```name=clang-9
$ llvm-dwarfdump --show-form buck-out/gen/aab7ed39/folly/experimental/symbolizer/test/symbolizer_test_utils_dwarf5_split_dwarf_inlining#compile-SymbolizerTestUtils.cpp.o1ef1b890\,platform009-clang/SymbolizerTestUtils.cpp.o
.debug_info contents:
0x00000000: Compile Unit: length = 0x00000127, format = DWARF32, version = 0x0005, unit_type = DW_UT_skeleton, abbr_offset = 0x0000, addr_size = 0x08, DWO_id = 0x7d3c88943756aebb (next unit at 0x0000012b)

0x00000014: DW_TAG_compile_unit
              DW_AT_stmt_list   (0x00000000)
              DW_AT_str_offsets_base    (0x00000008)
              DW_AT_comp_dir    (".")
              DW_AT_GNU_pubnames        (true)
              DW_AT_GNU_dwo_name        ("buck-out/dbg/gen/aab7ed39/folly/experimental/symbolizer/test/symbolizer_test_utils_dwarf5_split_dwarf_inlining#compile-SymbolizerTestUtils.cpp.o1ef1b890,platform009-clang/SymbolizerTestUtils.cpp.o")
              DW_AT_low_pc      (0x0000000000000000)
              DW_AT_ranges      (indexed (0x0) rangelist = 0x00000010
                 [0x0000000000000000, 0x000000000000005b)
                 [0x0000000000000000, 0x0000000000000065)
                 [0x0000000000000000, 0x000000000000005a)
                 [0x0000000000000000, 0x0000000000000065)
                 [0x0000000000000000, 0x000000000000000b)
                 [0x0000000000000000, 0x0000000000000076)
                 [0x0000000000000000, 0x0000000000000014)
                 [0x0000000000000000, 0x0000000000000065)
                 [0x0000000000000000, 0x0000000000000076)
                 [0x0000000000000000, 0x0000000000000014)
                 [0x0000000000000000, 0x0000000000000065)
                 [0x0000000000000000, 0x0000000000000085)
                 [0x0000000000000000, 0x000000000000000b))
              DW_AT_addr_base   (0x00000008)
              DW_AT_rnglists_base       (0x0000000c)

```
```name=clang-12
$ llvm-dwarfdump --show-form buck-out/gen/aab7ed39/folly/experimental/symbolizer/test/symbolizer_test_utils_dwarf5_split_dwarf_inlining#compile-SymbolizerTestUtils.cpp.o1ef1b890\,platform009-clang-12/SymbolizerTestUtils.cpp.o
.debug_info contents:
0x00000000: Compile Unit: length = 0x00000127, format = DWARF32, version = 0x0005, unit_type = DW_UT_skeleton, abbr_offset = 0x0000, addr_size = 0x08, DWO_id = 0xb881aa098abf71b5 (next unit at 0x0000012b)

0x00000014: DW_TAG_skeleton_unit
              DW_AT_stmt_list [DW_FORM_sec_offset]	(0x00000000)
              DW_AT_str_offsets_base [DW_FORM_sec_offset]	(0x00000008)
              DW_AT_comp_dir [DW_FORM_strx1]	(".")
              DW_AT_GNU_pubnames [DW_FORM_flag_present]	(true)
              DW_AT_dwo_name [DW_FORM_strx1]	("buck-out/dbg/gen/aab7ed39/folly/experimental/symbolizer/test/symbolizer_test_utils_dwarf5_split_dwarf_inlining#compile-SymbolizerTestUtils.cpp.o1ef1b890,platform009-clang-12/SymbolizerTestUtils.cpp.o")
              DW_AT_low_pc [DW_FORM_addr]	(0x0000000000000000)
              DW_AT_ranges [DW_FORM_rnglistx]	(indexed (0x0) rangelist = 0x00000010
                 [0x0000000000000000, 0x000000000000004c)
                 [0x0000000000000000, 0x000000000000005f)
                 [0x0000000000000000, 0x0000000000000054)
                 [0x0000000000000000, 0x000000000000005f)
                 [0x0000000000000000, 0x000000000000000b)
                 [0x0000000000000000, 0x0000000000000070)
                 [0x0000000000000000, 0x0000000000000014)
                 [0x0000000000000000, 0x000000000000005f)
                 [0x0000000000000000, 0x0000000000000070)
                 [0x0000000000000000, 0x0000000000000014)
                 [0x0000000000000000, 0x000000000000005f)
                 [0x0000000000000000, 0x0000000000000086)
                 [0x0000000000000000, 0x000000000000000b))
              DW_AT_addr_base [DW_FORM_sec_offset]	(0x00000008)
              DW_AT_rnglists_base [DW_FORM_sec_offset]	(0x0000000c)
```

Differential Revision: D30755400

fbshipit-source-id: 6e7fd8bc9d3bef90a5195dc30dff60c489c4df35

Summary: Add build-time flags for setting default spin and yield counts.

Reviewed By: fadimounir

Differential Revision: D30761279

fbshipit-source-id: 3b74bae438b1f87b1ca8b955bb244eb907b22891