Summary:
basic_fbstring provides an allocator template paramater for
compatibility with basic_string, but ignores it. Assert at compile
time that a custom allocator isn't used.

This would have prevented the regression introduced in D22970418 (https://github.com/facebook/folly/commit/abb4ece62120ff32aaf28dc4bbfdc6a2f2b41f78) and
fixed in D23035304 (https://github.com/facebook/folly/commit/8b650246220717f27046593b5819fbaa60427bcb).

Reviewed By: luciang

Differential Revision: D23144806

fbshipit-source-id: c541f274e97736b9408651a66088bcbb78025539

Summary:
Fixes a few documentation errors that get surfaced when compiling with the -Wdocumentation flag.

Full explanation of errors with examples here:
https://clang.llvm.org/docs/DiagnosticsReference.html#wdocumentation

Reviewed By: yfeldblum

Differential Revision: D23119100

fbshipit-source-id: 4e84f624e4d81914b78211af4860540498f8110c

Summary: try_dequeue() used to consume from the queue but not from the semaphore, causing the two to diverge and breaking subsequent dequeue() calls.

Reviewed By: yfeldblum

Differential Revision: D23160324

fbshipit-source-id: f709733d984f51abc53595d38dbef3daffbfa6d9

Summary: [Folly] Move `DeterministicSchedule` helper alias `TLState` to the source, and outline all uses into the source.

Reviewed By: nbronson, luciang

Differential Revision: D23157071

fbshipit-source-id: 957576a61a796f46da781e02419a1229e681d4c1

Reviewed By: mzlee

Differential Revision: D23066827

fbshipit-source-id: 6362acb7a6680a24871859d7874a9caec0a1538e

Summary:
Changed the way how enums generated in thrift-py3:

1. Use C++ map to store name to unique Enum Python instances cache
2. Dynamically find instances from cache (or create one and add to cache) instead of populating all instances at module load time
3. use `__getattr__` and `__getitem__` instead of code-gen all the getters

Reviewed By: yfeldblum

Differential Revision: D22499183

fbshipit-source-id: b2af8d94024c3591c3d7faaa15cbd026a134cc78

Summary: [Folly] Remove wrong use of `errno` in `AsyncUDPSocket`.

Reviewed By: markisaa

Differential Revision: D23153435

fbshipit-source-id: f567aa97ebe243ff5b6ad99e300212df290800bb

Summary:
Previously, there was a race between exitingSems_[...] = tls.sem (in beforeThreadExit) and exitingSems_[...].post() (in joinAll). The race exists because exitingSems_ is a map that is not protected by the "shared access" synchronization mechanism used by DeterministicSchedule (i.e. it does not sit between a beforeSharedAccess and afterSharedAccess pair). Specifically, the main thread can be reading exitingSems_ while a child thread is writing to it.

This diff fixes that: after all threads are ready to exit (this part isn't changed), we first wait for the joiner thread itself to be scheduled, and then, it will post the semaphore to wake up the child thread to run its thread-local destructors, and at the same time call .join() on the child. All this runs in a "critical section" between beforeSharedAccess and afterSharedAccess in the joiner thread.

For clarity also changed the child thread to use descheduleCurrentThread, and to make the DeterministicSchedule destructor no longer call beforeThreadExit since it makes little sense.

Reviewed By: yfeldblum

Differential Revision: D23119075

fbshipit-source-id: 22bc6ffd9a9d888cc09bdee066dcac7f05b29fa7

Summary: [Folly] Reimplement `SignalSafeElfCache::Path` minimally so that it meets the expectations of `std::basic_string` as used by the rest of `SignalSafeElfCache`.

Reviewed By: chadaustin, luciang

Differential Revision: D23152224

fbshipit-source-id: 48c7a7277d00a928d3de2937699ad112d6d560c2

Summary: [Folly] Cut an extra `rdtsc` in `DistributedMutex` spin.

Reviewed By: aary

Differential Revision: D21947987

fbshipit-source-id: 8d6dca75f5290581a886385cefe994c19af839e1

Summary:
It's difficult to use C++ allocators if they are not default-constructible.  The non-default-constructibility "infects" the container, and any class that holds the container (transitively).

In D21967640 (https://github.com/facebook/folly/commit/f0471228b89be4a399afcf0e9692c84754d06875), I made `folly::SysArenaAllocator` default constructible, and adopted the behavior of merely throwing `std::bad_alloc` in the event that we didn't *actually* initialize it with a `folly::SysArena`.  In hindsight, it's not clear this was an improvement.  All it did was move a compile-time problem to run-time.

What I do here is a bit better.  I enhance `CxxAllocatorAdaptor` such that it has two modes:
- **Normal / classic mode:** non-default constructible.
  - Guaranteed at compile-time to have a non-null "inner allocator"
- **`FallbackToStdAlloc` mode:** default-constructible.
  - Passes allocations through to `std::allocator` if no "inner allocator" provided

Using this support, I introduce a new allocator, `folly::FallbackSysArenaAllocator`, which is similar to `SysArenaAllocator` *except* that it uses the fallback mode and is therefore default-constructible.

This is useful in a large codebase where we want to use arena-allocation on a specific *instance* of a container type -- and not every single instance.

Reviewed By: yfeldblum

Differential Revision: D22938039

fbshipit-source-id: feaba12d76564a386a03e759eedf06a77bbc8942

Summary:
Now that the subprocess output is no longer piped, we can see a weird situation
where the command being run is displayed after the compilation step:
  + cd /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/build/eden && \
  [1/13] rust_job_pool
      Finished release [optimized] target(s) in 0.75s
  [12/13] Install the project...
  -- Install configuration: "RelWithDebInfo"
  -- Installing: /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/bin/edenfs
  -- Set runtime path of "/data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/bin/edenfs" to ""
  -- Up-to-date: /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/bin/edenfsctl
  -- Up-to-date: /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/lib/libbackingstore_rs.a
  -- Up-to-date: /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/lib/libbackingstore.a
  -- Up-to-date: /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/include/eden/scm/lib/backingstore/c_api/HgNativeBackingStore.h
  -- Up-to-date: /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/eden/include/eden/scm/lib/backingstore/c_api/RustBackingStore.h
  + /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/installed/cmake-Ncng4tsJb6gdOu40ggy14-YtgNQD43 (https://github.com/facebook/folly/commit/f47621ec247c8009d8a8aae8823f0de7c27a70fe)k5ev0n-FXq99I/bin/cmake \
  +      --build \
  +      /data/users/xavierd/scratch/dataZusersZxavierdZfbsource/fbcode_builder_getdeps/build/eden \
  +      --target \
  +      install \
  +      --config \
  +      Release \
  +      -j \
  +      24

This is a bit awkward. Flushing stdout's buffer allows for the ordering to be
correct.

Reviewed By: wez

Differential Revision: D23079405

fbshipit-source-id: e2bf25b098d6ab4a788a5ec07deb635a42cae18c

Summary: Original commit changeset: 2d4ad67a4a01

Reviewed By: yfeldblum

Differential Revision: D23064000

fbshipit-source-id: 88d8d550772c2045f61d5a355cf33c9d8df7d046

Summary: Found because I saw the error message

Reviewed By: magedm

Differential Revision: D23019298

fbshipit-source-id: 6744e9e6d0c21cf76db756f68b3e948a044e6888

Summary: [Folly] Fix TSAN-reported race in `ShutdownSocketSet` test where the shutdown does not wait for the server.

Reviewed By: yfeldblum

Differential Revision: D23057822

fbshipit-source-id: 4b682e6e80cff503e85cb2b663f8399b69265a77

Summary:
The folly::fibers GDB extension, specifically the `info fibers` command,
depended on a specific format of the std::unique_ptr pretty printer
output. This pretty printer format changed between GCC 7 and GCC 9, with
the latter omitting the target address. However, the new pretty printer
does expose an iterator for the child target address that we can use
instead.

Differential Revision: D23063364

fbshipit-source-id: 6125edaba9abcfd0b7a9c0741a18854637c97804

Summary:
`std::allocator<void>::allocate` is not invocable as policy. Let folly allocators behave the same.

Switch existing sites to parameterizing the allocators over `char` instead, since `std::allocator<char>::allocate` is invocable.

Reviewed By: yfeldblum

Differential Revision: D22986960

fbshipit-source-id: ca1ff3cb1785029b6b6f59ddc4046b1b105d8bd6

Summary:
The hinted forms of insert_or_assign were forwarding with
std::move rather than std::forward, which has the potential to elevate
a non-const lvalue ref to an rvalue ref.

(Note: this ignores all push blocking failures!)

Reviewed By: yfeldblum

Differential Revision: D21475865

fbshipit-source-id: e91e759762cf6f045c843cd7de1402953e6afb61

Summary: Original commit changeset: 8d5e96feea4d

Reviewed By: yfeldblum

Differential Revision: D23046629

fbshipit-source-id: e24c4a0ba5f40a584646a602f618e881dbf0f344

Summary:
basic_fbstring unfortunately just ignores the allocator. Switching it to use std::basic_string.

This is necessary because ElfCache must be async-signal-safe, but basic_fbstring ignores the allocator and always uses standard malloc/free, which are not safe async-signal-safe.

Reviewed By: yfeldblum

Differential Revision: D23035304

fbshipit-source-id: 7b4e77a3764701366556a5fe5a352f952b052ed4

Summary:
These are all test setup issues:
 - EventBase needs to be destructed before objects that callbacks may refer to.
 - A socket should not be operated on by a thread that is different from the event base it is associated with (in this case, the socket was being closed on the RSA computation thread).

Reviewed By: yfeldblum

Differential Revision: D23043485

fbshipit-source-id: 733868317aef09e32e79169aedb84a988de3bb41

Summary: Increase coverage of blocking operation logging.

Reviewed By: yfeldblum

Differential Revision: D22933413

fbshipit-source-id: e820927ddafa0bb5f2d50dbb1dceeeb2e89133b3

Summary: A doc comment in folly/Poly.h makes reference to a non-existent entity "`Decay`" and is missing namespace qualifiers, making the example confusing and wrong.

Reviewed By: Alfus, yfeldblum

Differential Revision: D23038865

fbshipit-source-id: 50f515b31919552e11ae18ff645ef71812d77bfb

Summary: [Folly] Simplify `reentrant_allocator` hierarchy while preserving presence/absence rules of `allocate` and `dealllocate`. Apply same rules to `max_size` and `address`. Plus some assorted tweaks. Plus some comments.

Reviewed By: luciang

Differential Revision: D23016816

fbshipit-source-id: 601318ea112193afcffc93d6783dbd79168a164e

Summary: [Folly] Add `exception_wrapper::from_exception_ptr` taking by `&&`, permitting callers to move, since `std::exception_ptr` copy is expensive and `std::rethrow_exception` takes by value.

Reviewed By: ericniebler, markisaa

Differential Revision: D23016839

fbshipit-source-id: c07695fef0828a50426fe4e2b40fae9582c7ffd9

Summary:
This failed on mode/opt, because the `- sh_addr + sh_offset` was actually using the address and offset of the *symbol table section*, not the *data section* (where the kStringValue variable actually is). It still worked, because for mapped sections, the `offset - address` just happens to be the same for all sections, so it didn't matter what section we used; in debug mode, we use dynamic linking, so the symbol section is called .dynsym and is loaded in memory, but in opt mode, the symbol section is called .symtab and is *not* loaded, so sh_addr is zero, and that formula no longer works.

The goal there was really just to subtract the binary base address encoded in the ELF file. ElfFile already provides this via getBaseAddress(), and that's also how we can identify whether the loaded ELF (in this case, the same as the current executable) is PIE; so switched both the calculation and the if condition to use this result.

Reviewed By: yfeldblum

Differential Revision: D23020998

fbshipit-source-id: f7e66bb554c62aa13d7d2fc1017cb31542507be9

Summary: Avoid traversing the callbacks map twice when inserting a non-existing entry

Reviewed By: kevin-vigor

Differential Revision: D23030404

fbshipit-source-id: afbf7564f4039ffbd942f407429874fde795025d

Summary: Fix Singleton TSAN issue (mutex used after being destroyed)

Reviewed By: yfeldblum

Differential Revision: D22925120

fbshipit-source-id: e25c113cdef7076c93a189281f5b9d842f576dd3

Summary: Add definition to EventBase.

Differential Revision: D23004586

fbshipit-source-id: 828767b3d9a43c33bcf047b9b06c08bfba8fde68

Reviewed By: andriigrynenko

Differential Revision: D23008623

fbshipit-source-id: db3e5a3dfe8dbbf1c9583b8e4924da31c2f5c174

Summary:
The implementation of `std::basic_string` with the legacy ABI and with `_GLIBCXX_FULLY_DYNAMIC_STRING`, as appears by default on CentOS 7, incorrectly requires the provided allocator type to have a default constructor. The `Allocator` concept does not require this and many allocator types with runtime state shared between copies will not provide this.

Switch to `folly::fbstring` in `ElfCache` to sidestep this problem.

Fixes: https://github.com/facebook/folly/issues/1344.

Reviewed By: yfeldblum

Differential Revision: D22970418

fbshipit-source-id: 1e188d668991d25f53da5702b31f4a7a7ec7d7e8

Summary: (Note: this ignores all push blocking failures!)

Reviewed By: andriigrynenko

Differential Revision: D23005233

fbshipit-source-id: 4ea528505e06fec0af7841ccbd6d41eabe0de558

Summary:
A tracepoint semaphore address is written to the notes section as either the absolute address (if binary is compiled as non-PIE) or the relative address (if binary is compiled as PIE) of the semaphore. In the former case, the test passes; in the latter case, the test as it was could not possibly pass because the binary is mapped to some random base address.

This diff makes a guess: if the addresses are equal, then we're non-PIE; otherwise check if the address offset is valid - that offset is the address at which the binary is mapped, so it always begins with the ELF header, so we can check against that.

If someone knows how to easily figure out that random address or to detect whether the binary is PIE (thereby disabling the test) that'd be great too.

This fixes TSAN for the test, as TSAN binaries are built as PIE.

Reviewed By: yfeldblum

Differential Revision: D22752824

fbshipit-source-id: cd320f9fb8355a20f65e2385f0a1ab1c24ec0b81

Summary:
Previously `OpenSSLUtils::getCommonName` was allocating a 64 byte long string and copying the common name from the `X509` into it. We unexpectedly returned that string potentially containing trailing `\0`s.

This diff rewrites the function to allocate a big enough buffer, write to it, then return an appropriately trimmed new string from it.

Reviewed By: yfeldblum

Differential Revision: D22910431

fbshipit-source-id: 77b4fc3ccde4f7ddb0f62b884ecd7ff0c868c1ca

Reviewed By: yfeldblum, andriigrynenko

Differential Revision: D22965140

fbshipit-source-id: 8f9996ccc28aff621879774e901b0c75e8c62883

Summary: Make hazptr_obj_cohort active_ atomic to be data-race-free.

Reviewed By: yfeldblum

Differential Revision: D22976574

fbshipit-source-id: 5a09aa7cedc26c71b2160b2df14a7e0f7b55e2e7

Summary:
The deps for Fedora in the public README are a little out of date.  Add /
update some.

Reviewed By: yfeldblum

Differential Revision: D22951514

fbshipit-source-id: 645af3df1b71dcdab06408d73d99c34c482ea534

Summary:
When we do the context switch onto the fiber, the stack frame points back to
the main context stack. While the fiber is running, this allows backtraces to
continue back onto the main context. When the fiber is suspended, we execute
code on the main context's stack, the pointers to this stack are now garbage,
backtracing in gdb runs into problems, such as garbage frames, gdb
crashes, and occasional cycles.

The fix here is to write a 0 to the saved return address in the last frame, when a fiber suspends.
gdb detects this and stops the trace
  #38 folly::fibers::FiberManager::activateFiber(folly::fibers::Fiber*) (this=0x0, fiber=0x0) at folly/fibers/FiberManagerInternal-inl.h:82
  #39 folly::fibers::FiberManager::runReadyFiber(folly::fibers::Fiber*) (this=0x0, fiber=0x0) at folly/fibers/FiberManagerInternal-inl.h:127
  #40 0x0000000000000000 in  ()

I gated the fix to linux since I'm not sure about the ABI for other platforms.

Reviewed By: yfeldblum

Differential Revision: D22774189

fbshipit-source-id: 2d4ad67a4a01bebc4ff1f9c285f6e3e95d13432c

Summary:
- Move to the newer and forward moving libzstd-dev
https://packages.ubuntu.com/search?suite=default&section=all&arch=any&keywords=libzstd&searchon=names

Reviewed By: wez

Differential Revision: D22981784

fbshipit-source-id: 3647357aad60f2335ea494c35c174e9ffec61346

Summary: The find path reads a node that the insert path writes; they need to have acquire/release semantics due to the node being allocated on the fly.

Reviewed By: yfeldblum, magedm

Differential Revision: D22937394

fbshipit-source-id: c1497ed1764cd43e396bc520e9b716cdfe29e5ca