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Diffstat (limited to 'third_party/abseil_cpp/absl/base/thread_annotations.h')
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diff --git a/third_party/abseil_cpp/absl/base/thread_annotations.h b/third_party/abseil_cpp/absl/base/thread_annotations.h new file mode 100644 index 000000000000..e23fff1d2013 --- /dev/null +++ b/third_party/abseil_cpp/absl/base/thread_annotations.h @@ -0,0 +1,335 @@ +// Copyright 2017 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +// +// ----------------------------------------------------------------------------- +// File: thread_annotations.h +// ----------------------------------------------------------------------------- +// +// This header file contains macro definitions for thread safety annotations +// that allow developers to document the locking policies of multi-threaded +// code. The annotations can also help program analysis tools to identify +// potential thread safety issues. +// +// These annotations are implemented using compiler attributes. Using the macros +// defined here instead of raw attributes allow for portability and future +// compatibility. +// +// When referring to mutexes in the arguments of the attributes, you should +// use variable names or more complex expressions (e.g. my_object->mutex_) +// that evaluate to a concrete mutex object whenever possible. If the mutex +// you want to refer to is not in scope, you may use a member pointer +// (e.g. &MyClass::mutex_) to refer to a mutex in some (unknown) object. + +#ifndef ABSL_BASE_THREAD_ANNOTATIONS_H_ +#define ABSL_BASE_THREAD_ANNOTATIONS_H_ + +#include "absl/base/attributes.h" +#include "absl/base/config.h" +// TODO(mbonadei): Remove after the backward compatibility period. +#include "absl/base/internal/thread_annotations.h" // IWYU pragma: export + +// ABSL_GUARDED_BY() +// +// Documents if a shared field or global variable needs to be protected by a +// mutex. ABSL_GUARDED_BY() allows the user to specify a particular mutex that +// should be held when accessing the annotated variable. +// +// Although this annotation (and ABSL_PT_GUARDED_BY, below) cannot be applied to +// local variables, a local variable and its associated mutex can often be +// combined into a small class or struct, thereby allowing the annotation. +// +// Example: +// +// class Foo { +// Mutex mu_; +// int p1_ ABSL_GUARDED_BY(mu_); +// ... +// }; +#if ABSL_HAVE_ATTRIBUTE(guarded_by) +#define ABSL_GUARDED_BY(x) __attribute__((guarded_by(x))) +#else +#define ABSL_GUARDED_BY(x) +#endif + +// ABSL_PT_GUARDED_BY() +// +// Documents if the memory location pointed to by a pointer should be guarded +// by a mutex when dereferencing the pointer. +// +// Example: +// class Foo { +// Mutex mu_; +// int *p1_ ABSL_PT_GUARDED_BY(mu_); +// ... +// }; +// +// Note that a pointer variable to a shared memory location could itself be a +// shared variable. +// +// Example: +// +// // `q_`, guarded by `mu1_`, points to a shared memory location that is +// // guarded by `mu2_`: +// int *q_ ABSL_GUARDED_BY(mu1_) ABSL_PT_GUARDED_BY(mu2_); +#if ABSL_HAVE_ATTRIBUTE(pt_guarded_by) +#define ABSL_PT_GUARDED_BY(x) __attribute__((pt_guarded_by(x))) +#else +#define ABSL_PT_GUARDED_BY(x) +#endif + +// ABSL_ACQUIRED_AFTER() / ABSL_ACQUIRED_BEFORE() +// +// Documents the acquisition order between locks that can be held +// simultaneously by a thread. For any two locks that need to be annotated +// to establish an acquisition order, only one of them needs the annotation. +// (i.e. You don't have to annotate both locks with both ABSL_ACQUIRED_AFTER +// and ABSL_ACQUIRED_BEFORE.) +// +// As with ABSL_GUARDED_BY, this is only applicable to mutexes that are shared +// fields or global variables. +// +// Example: +// +// Mutex m1_; +// Mutex m2_ ABSL_ACQUIRED_AFTER(m1_); +#if ABSL_HAVE_ATTRIBUTE(acquired_after) +#define ABSL_ACQUIRED_AFTER(...) __attribute__((acquired_after(__VA_ARGS__))) +#else +#define ABSL_ACQUIRED_AFTER(...) +#endif + +#if ABSL_HAVE_ATTRIBUTE(acquired_before) +#define ABSL_ACQUIRED_BEFORE(...) __attribute__((acquired_before(__VA_ARGS__))) +#else +#define ABSL_ACQUIRED_BEFORE(...) +#endif + +// ABSL_EXCLUSIVE_LOCKS_REQUIRED() / ABSL_SHARED_LOCKS_REQUIRED() +// +// Documents a function that expects a mutex to be held prior to entry. +// The mutex is expected to be held both on entry to, and exit from, the +// function. +// +// An exclusive lock allows read-write access to the guarded data member(s), and +// only one thread can acquire a lock exclusively at any one time. A shared lock +// allows read-only access, and any number of threads can acquire a shared lock +// concurrently. +// +// Generally, non-const methods should be annotated with +// ABSL_EXCLUSIVE_LOCKS_REQUIRED, while const methods should be annotated with +// ABSL_SHARED_LOCKS_REQUIRED. +// +// Example: +// +// Mutex mu1, mu2; +// int a ABSL_GUARDED_BY(mu1); +// int b ABSL_GUARDED_BY(mu2); +// +// void foo() ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu1, mu2) { ... } +// void bar() const ABSL_SHARED_LOCKS_REQUIRED(mu1, mu2) { ... } +#if ABSL_HAVE_ATTRIBUTE(exclusive_locks_required) +#define ABSL_EXCLUSIVE_LOCKS_REQUIRED(...) \ + __attribute__((exclusive_locks_required(__VA_ARGS__))) +#else +#define ABSL_EXCLUSIVE_LOCKS_REQUIRED(...) +#endif + +#if ABSL_HAVE_ATTRIBUTE(shared_locks_required) +#define ABSL_SHARED_LOCKS_REQUIRED(...) \ + __attribute__((shared_locks_required(__VA_ARGS__))) +#else +#define ABSL_SHARED_LOCKS_REQUIRED(...) +#endif + +// ABSL_LOCKS_EXCLUDED() +// +// Documents the locks acquired in the body of the function. These locks +// cannot be held when calling this function (as Abseil's `Mutex` locks are +// non-reentrant). +#if ABSL_HAVE_ATTRIBUTE(locks_excluded) +#define ABSL_LOCKS_EXCLUDED(...) __attribute__((locks_excluded(__VA_ARGS__))) +#else +#define ABSL_LOCKS_EXCLUDED(...) +#endif + +// ABSL_LOCK_RETURNED() +// +// Documents a function that returns a mutex without acquiring it. For example, +// a public getter method that returns a pointer to a private mutex should +// be annotated with ABSL_LOCK_RETURNED. +#if ABSL_HAVE_ATTRIBUTE(lock_returned) +#define ABSL_LOCK_RETURNED(x) __attribute__((lock_returned(x))) +#else +#define ABSL_LOCK_RETURNED(x) +#endif + +// ABSL_LOCKABLE +// +// Documents if a class/type is a lockable type (such as the `Mutex` class). +#if ABSL_HAVE_ATTRIBUTE(lockable) +#define ABSL_LOCKABLE __attribute__((lockable)) +#else +#define ABSL_LOCKABLE +#endif + +// ABSL_SCOPED_LOCKABLE +// +// Documents if a class does RAII locking (such as the `MutexLock` class). +// The constructor should use `LOCK_FUNCTION()` to specify the mutex that is +// acquired, and the destructor should use `UNLOCK_FUNCTION()` with no +// arguments; the analysis will assume that the destructor unlocks whatever the +// constructor locked. +#if ABSL_HAVE_ATTRIBUTE(scoped_lockable) +#define ABSL_SCOPED_LOCKABLE __attribute__((scoped_lockable)) +#else +#define ABSL_SCOPED_LOCKABLE +#endif + +// ABSL_EXCLUSIVE_LOCK_FUNCTION() +// +// Documents functions that acquire a lock in the body of a function, and do +// not release it. +#if ABSL_HAVE_ATTRIBUTE(exclusive_lock_function) +#define ABSL_EXCLUSIVE_LOCK_FUNCTION(...) \ + __attribute__((exclusive_lock_function(__VA_ARGS__))) +#else +#define ABSL_EXCLUSIVE_LOCK_FUNCTION(...) +#endif + +// ABSL_SHARED_LOCK_FUNCTION() +// +// Documents functions that acquire a shared (reader) lock in the body of a +// function, and do not release it. +#if ABSL_HAVE_ATTRIBUTE(shared_lock_function) +#define ABSL_SHARED_LOCK_FUNCTION(...) \ + __attribute__((shared_lock_function(__VA_ARGS__))) +#else +#define ABSL_SHARED_LOCK_FUNCTION(...) +#endif + +// ABSL_UNLOCK_FUNCTION() +// +// Documents functions that expect a lock to be held on entry to the function, +// and release it in the body of the function. +#if ABSL_HAVE_ATTRIBUTE(unlock_function) +#define ABSL_UNLOCK_FUNCTION(...) __attribute__((unlock_function(__VA_ARGS__))) +#else +#define ABSL_UNLOCK_FUNCTION(...) +#endif + +// ABSL_EXCLUSIVE_TRYLOCK_FUNCTION() / ABSL_SHARED_TRYLOCK_FUNCTION() +// +// Documents functions that try to acquire a lock, and return success or failure +// (or a non-boolean value that can be interpreted as a boolean). +// The first argument should be `true` for functions that return `true` on +// success, or `false` for functions that return `false` on success. The second +// argument specifies the mutex that is locked on success. If unspecified, this +// mutex is assumed to be `this`. +#if ABSL_HAVE_ATTRIBUTE(exclusive_trylock_function) +#define ABSL_EXCLUSIVE_TRYLOCK_FUNCTION(...) \ + __attribute__((exclusive_trylock_function(__VA_ARGS__))) +#else +#define ABSL_EXCLUSIVE_TRYLOCK_FUNCTION(...) +#endif + +#if ABSL_HAVE_ATTRIBUTE(shared_trylock_function) +#define ABSL_SHARED_TRYLOCK_FUNCTION(...) \ + __attribute__((shared_trylock_function(__VA_ARGS__))) +#else +#define ABSL_SHARED_TRYLOCK_FUNCTION(...) +#endif + +// ABSL_ASSERT_EXCLUSIVE_LOCK() / ABSL_ASSERT_SHARED_LOCK() +// +// Documents functions that dynamically check to see if a lock is held, and fail +// if it is not held. +#if ABSL_HAVE_ATTRIBUTE(assert_exclusive_lock) +#define ABSL_ASSERT_EXCLUSIVE_LOCK(...) \ + __attribute__((assert_exclusive_lock(__VA_ARGS__))) +#else +#define ABSL_ASSERT_EXCLUSIVE_LOCK(...) +#endif + +#if ABSL_HAVE_ATTRIBUTE(assert_shared_lock) +#define ABSL_ASSERT_SHARED_LOCK(...) \ + __attribute__((assert_shared_lock(__VA_ARGS__))) +#else +#define ABSL_ASSERT_SHARED_LOCK(...) +#endif + +// ABSL_NO_THREAD_SAFETY_ANALYSIS +// +// Turns off thread safety checking within the body of a particular function. +// This annotation is used to mark functions that are known to be correct, but +// the locking behavior is more complicated than the analyzer can handle. +#if ABSL_HAVE_ATTRIBUTE(no_thread_safety_analysis) +#define ABSL_NO_THREAD_SAFETY_ANALYSIS \ + __attribute__((no_thread_safety_analysis)) +#else +#define ABSL_NO_THREAD_SAFETY_ANALYSIS +#endif + +//------------------------------------------------------------------------------ +// Tool-Supplied Annotations +//------------------------------------------------------------------------------ + +// ABSL_TS_UNCHECKED should be placed around lock expressions that are not valid +// C++ syntax, but which are present for documentation purposes. These +// annotations will be ignored by the analysis. +#define ABSL_TS_UNCHECKED(x) "" + +// ABSL_TS_FIXME is used to mark lock expressions that are not valid C++ syntax. +// It is used by automated tools to mark and disable invalid expressions. +// The annotation should either be fixed, or changed to ABSL_TS_UNCHECKED. +#define ABSL_TS_FIXME(x) "" + +// Like ABSL_NO_THREAD_SAFETY_ANALYSIS, this turns off checking within the body +// of a particular function. However, this attribute is used to mark functions +// that are incorrect and need to be fixed. It is used by automated tools to +// avoid breaking the build when the analysis is updated. +// Code owners are expected to eventually fix the routine. +#define ABSL_NO_THREAD_SAFETY_ANALYSIS_FIXME ABSL_NO_THREAD_SAFETY_ANALYSIS + +// Similar to ABSL_NO_THREAD_SAFETY_ANALYSIS_FIXME, this macro marks a +// ABSL_GUARDED_BY annotation that needs to be fixed, because it is producing +// thread safety warning. It disables the ABSL_GUARDED_BY. +#define ABSL_GUARDED_BY_FIXME(x) + +// Disables warnings for a single read operation. This can be used to avoid +// warnings when it is known that the read is not actually involved in a race, +// but the compiler cannot confirm that. +#define ABSL_TS_UNCHECKED_READ(x) absl::base_internal::ts_unchecked_read(x) + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace base_internal { + +// Takes a reference to a guarded data member, and returns an unguarded +// reference. +// Do not used this function directly, use ABSL_TS_UNCHECKED_READ instead. +template <typename T> +inline const T& ts_unchecked_read(const T& v) ABSL_NO_THREAD_SAFETY_ANALYSIS { + return v; +} + +template <typename T> +inline T& ts_unchecked_read(T& v) ABSL_NO_THREAD_SAFETY_ANALYSIS { + return v; +} + +} // namespace base_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_BASE_THREAD_ANNOTATIONS_H_ |