The intent of the macro is to say what locks cannot be held when calling the method, not making a promise that they will be acquired.
PiperOrigin-RevId: 454158686
Change-Id: I71087460c3df27c7d6e0571156f19f525024f1de
This change introduces the symbol
ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
to guard redundant declarations of static constexpr data
members that are needed prior to C++17.
This change also introduces the symbol
ABSL_INTERNAL_CPLUSPLUS_LANG, which is supposed to be set
to the same value as __cplusplus, except it uses _MSVC_LANG
on MSVC so that the value is correct on MSVC.
Neither of these new symbols should be used outside of Abseil.
Fixes#1191
PiperOrigin-RevId: 453923908
Change-Id: I1316c52c19fa0c168b93cced0c817e4cb7c9c862
When we would perform a stacktrace using the frame pointer walking, because we
did the adjustment for the return address separately, we were misaligning the
stack size and frame. Simplify the logic and correct the offset.
The recovered frame pointer provides us with the return address of the current
frame and the previous frame's frame pointer. Subsequently, we decide if we
want to record this frame or not. The value in `next_frame_pointer` already
points to the value from the previous stack frame (that is the next frame
pointer to iterate). As such, the value computed by `ComputeStackFrameSize` is
the value for the current frame. This was offset by one previously.
Take the opportunity to clean up some of the local comments, fixing typos and
splitting up the comments to reflect the lines that they are associated with.
PiperOrigin-RevId: 453744059
Change-Id: If14813e0ac36f327f4b7594472f2222d05c478aa
A few targets were missing `linkopts = ...` and so were not obeying
the project-wide default settings.
Omit any changes to cctz for now, because it's vendored from another project.
For portability, absl_time_test builds a small, incomplete tzdata
database into the test binary and uses that instead of the system tzdata
database. (absl_time_test needs to run on some platforms that lack a
system tzdata database.) However, this causes issues if TZ is set to
something that isn’t in the test database. To address them, fall back to
America/Los_Angeles if TZ is set to an unknown value during testing.
Bug: https://bugs.debian.org/1012194
PiperOrigin-RevId: 453257912
Change-Id: I293d0f96876b31c32a2847468a3377bb49f3aa15
Avoid using value move/swap and delete those functions from slot_policy types. There was only one use of params_type::move in `erase`.
PiperOrigin-RevId: 453237739
Change-Id: Ie81c6dba6c4db34e97a067d2c0defcded8044a5a
https://pastebin.com/CmnzwUFN
The key idea is to avoid using 16 byte NEON and use 8 byte NEON which has lower latency for BitMask::Match. Even though 16 byte NEON achieves higher throughput, in SwissMap it's very important to catch these Matches with low latency as probing on average happens at most once.
I also introduced NonIterableMask as ARM has really great cbnz instructions and additional AND on scalar mask had 1 extra latency cycle
PiperOrigin-RevId: 453216147
Change-Id: I842c50d323954f8383ae156491232ced55aacb78
absl::CordBuffer holds data for eventual inclusion within an existing
absl::Cord. CordBuffers are useful for building large Cords that may
require custom allocation of its associated memory, a pattern that is
common in zero-copy APIs.
PiperOrigin-RevId: 453212229
Change-Id: I6a8adc3a8d206691cb1b0001a9161e5080dd1c5f
The "deleted" overload error is useless to users. By passing some dummy string to the base class constructor we use a valid constructor and remove the unintended use of the deleted default constructor.
PiperOrigin-RevId: 452826509
Change-Id: I5430a373c8e7e3a13336d2c42899e0e59444620b
Decompose RandenPoolSeedSeq from NonsecureURBGBase.
Adjust how the RandenPoolSeedSeq detects contiguous buffers passed to the generate function. Previously it made incorrect assumptions regarding the contiguous concept, which have been replaced with some type-based tests for a small number of known contiguous random access iterator types, including raw pointers.
PiperOrigin-RevId: 452564114
Change-Id: Idab1df9dd078d8e5c565c7fa7ccb9c0d3d392ad2
We were using `init_type`s for temp values that we would move into slots, but in this case, we need to have actual slots. We use node handles for managing slots outside of nodes.
Also, in btree::copy_or_move_values_in_order, pass the slots from the iterators rather than references to values. This allows for moving from map keys instead of copying for standard layout types.
In the test, fix a couple of ClangTidy warnings from missing includes and calling `new` instead of `make_unique`.
PiperOrigin-RevId: 452062967
Change-Id: I870e89ae1aa5b3cfa62ae6e75b73ffc3d52e731c
Timeouts were once necessary when the SpinLock Unlock used an atomic
store and could therefore have a race and a missed wakeup, however,
the Unlock path now uses an atomic exchange, so the missed wakeup
cannot happen.
Fixes#1179
PiperOrigin-RevId: 452047517
Change-Id: I844944879b51b7f7ddac148e063a376cddd0d05a
This fixes an overload that is ambiguous for some toolchains, because
0U does not always refer to a uint32_t (on some toolchains, uint32_t
is an unsigned long).
PiperOrigin-RevId: 451962182
Change-Id: Id13700817ea3eb6d04e2cc02f20726040eb447fb
Without the change absl-cpp build fails on this week's gcc-13 snapshot as:
/build/abseil-cpp/absl/strings/internal/str_format/extension.h:34:33: error: found ':' in nested-name-specifier, expected '::'
34 | enum class FormatConversionChar : uint8_t;
| ^
| ::
Benchmarks: https://pastebin.com/tZ7dr67W. Works well especially on smaller ranges.
After a week on spending optimizing NEON SIMD where I almost managed to make hash tables work with NEON SIMD without performance hits (still 1 cycle to optimize and I gave up a little), I found an interesting optimization for aarch64 to use cls instruction (count leading sign bits).
The loop has a property that ctrl_ group is not matched against count when the first slot is empty or deleted.
```
void skip_empty_or_deleted() {
while (IsEmptyOrDeleted(*ctrl_)) {
uint32_t shift = Group{ctrl_}.CountLeadingEmptyOrDeleted();
ctrl_ += shift;
slot_ += shift;
}
...
}
```
However, `kEmpty` and `kDeleted` have format of `1xxxxxx0` and `~ctrl & (ctrl >> 7)` always sets the lowest bit to 1.
In naive implementation, it does +1 to start counting zero bits, however, in aarch64 we may start counting one bits immediately. This saves 1 cycle and 5% of iteration performance.
Then it becomes hard to find a supported and sustainable C++ version of it.
`__clsll` is not supported by GCC and was supported only since clang 8, `__builtin_clrsb` is not producing optimal codegen for clang. `__rbit` is not supported by GCC and there is no intrinsic to do that, however, in clang we have `__builtin_bitreverse{32,64}`. For now I decided to enable this only for clang, only if they have appropriate builtins.
PiperOrigin-RevId: 451168570
Change-Id: I7e9256a60aecdc88ced4e6eb15ebc257281b6664
Previously was disabled on iPhone, but still enabled for macOS.
The unscaled cycle clock does not work correctly when run on a VM.
PiperOrigin-RevId: 449876559
Change-Id: I679ade90b43462e8d2794b1a2b32569d59029ed9
Add a new (internal) feature test macro to detect whether the wrappers are no-ops on a given platform.
Note that one-arg __builtin_prefetch(x) is equivalent to __builtin_prefetch(x, 0, 3), per `man BUILTIN_PREFETCH(3)` and gcc docs.
PiperOrigin-RevId: 449508660
Change-Id: I144e750205eec0c956d8dd62bc72e10bdb87c4f7
Both Mutex and CondVar signal PerThreadSem/Waiter after satisfying the wait condition,
as the result the waiting thread may return w/o waiting on the
PerThreadSem/Waiter at all. If the waiting thread then exits, it currently
destroys Waiter object. As the result Waiter::Post can be called on
already destroyed object.
PerThreadSem/Waiter must be type-stable after creation and must not be destroyed.
The futex-based implementation is the only one that is not affected by the bug
since there is effectively nothing to destroy (maybe only UBSan/ASan
could complain about calling methods on a destroyed object).
Here is the problematic sequence of events:
1: void Mutex::Block(PerThreadSynch *s) {
2: while (s->state.load(std::memory_order_acquire) == PerThreadSynch::kQueued) {
3: if (!DecrementSynchSem(this, s, s->waitp->timeout)) {
4: PerThreadSynch *Mutex::Wakeup(PerThreadSynch *w) {
5: ...
6: w->state.store(PerThreadSynch::kAvailable, std::memory_order_release);
7: IncrementSynchSem(this, w);
8: ...
9: }
Consider line 6 is executed, then line 2 observes kAvailable and
line 3 is not called. The thread executing Mutex::Block returns from
the method, acquires the mutex, releases the mutex, exits and destroys
PerThreadSem/Waiter.
Now Mutex::Wakeup resumes and executes line 7 on the destroyed object. Boom!
CondVar uses a similar pattern.
Moreover the semaphore-based Waiter implementation is not even destruction-safe
(the Waiter cannot be used to signal own destruction). So even if Mutex/CondVar
would always pair Waiter::Post with Waiter::Wait before destroying PerThreadSem/Waiter,
it would still be subject to use-after-free bug on the semaphore.
PiperOrigin-RevId: 449159939
Change-Id: I497134fa8b6ce1294a422827c5f0de0e897cea31
CondVar::WaitWithTimeout can live-lock when timeout is racing with Signal/SignalAll
and Signal/SignalAll thread is not scheduled due to priorities, affinity or other
scheduler artifacts. This could lead to stalls of up to tens of seconds in some cases.
PiperOrigin-RevId: 449159670
Change-Id: I64bbd277c1f91964cfba3306ba8a80eeadf85f64
Abseil Team
Andy Getzendanner
Dino Radakovic
Derek Mauro
Tom Manshreck
Saleem Abdulrasool
James Y Knight
Jeremy Nimmer
Benjamin Barenblat
Evan Brown
Samuel Benzaquen
Laramie Leavitt
Tom Rybka
Anqi D
Greg Falcon
Jose Renau
Sergei Trofimovich