attributes.h

// 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.
//
// This header file defines macros for declaring attributes for functions,
// types, and variables.
//
// These macros are used within Abseil and allow the compiler to optimize, where
// applicable, certain function calls.
//
// Most macros here are exposing GCC or Clang features, and are stubbed out for
// other compilers.
//
// GCC attributes documentation:
//   https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Function-Attributes.html
//   https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Variable-Attributes.html
//   https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Type-Attributes.html
//
// Most attributes in this file are already supported by GCC 4.7. However, some
// of them are not supported in older version of Clang. Thus, we check
// `__has_attribute()` first. If the check fails, we check if we are on GCC and
// assume the attribute exists on GCC (which is verified on GCC 4.7).

// SKIP_ABSL_INLINE_NAMESPACE_CHECK

#ifndef ABSL_BASE_ATTRIBUTES_H_
#define ABSL_BASE_ATTRIBUTES_H_

#include "absl/base/config.h"

// ABSL_HAVE_ATTRIBUTE
//
// A function-like feature checking macro that is a wrapper around
// `__has_attribute`, which is defined by GCC 5+ and Clang and evaluates to a
// nonzero constant integer if the attribute is supported or 0 if not.
//
// It evaluates to zero if `__has_attribute` is not defined by the compiler.
//
// GCC: https://gcc.gnu.org/gcc-5/changes.html
// Clang: https://clang.llvm.org/docs/LanguageExtensions.html
#ifdef __has_attribute
#define ABSL_HAVE_ATTRIBUTE(x) __has_attribute(x)
#else
#define ABSL_HAVE_ATTRIBUTE(x) 0
#endif

// ABSL_HAVE_CPP_ATTRIBUTE
//
// A function-like feature checking macro that accepts C++11 style attributes.
// It's a wrapper around `__has_cpp_attribute`, defined by ISO C++ SD-6
// (https://en.cppreference.com/w/cpp/experimental/feature_test). If we don't
// find `__has_cpp_attribute`, will evaluate to 0.
#if defined(__cplusplus) && defined(__has_cpp_attribute)
// NOTE: requiring __cplusplus above should not be necessary, but
// works around https://bugs.llvm.org/show_bug.cgi?id=23435.
#define ABSL_HAVE_CPP_ATTRIBUTE(x) __has_cpp_attribute(x)
#else
#define ABSL_HAVE_CPP_ATTRIBUTE(x) 0
#endif

// -----------------------------------------------------------------------------
// Function Attributes
// -----------------------------------------------------------------------------
//
// GCC: https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html
// Clang: https://clang.llvm.org/docs/AttributeReference.html

// ABSL_PRINTF_ATTRIBUTE
// ABSL_SCANF_ATTRIBUTE
//
// Tells the compiler to perform `printf` format string checking if the
// compiler supports it; see the 'format' attribute in
// <https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Function-Attributes.html>.
//
// Note: As the GCC manual states, "[s]ince non-static C++ methods
// have an implicit 'this' argument, the arguments of such methods
// should be counted from two, not one."
#if ABSL_HAVE_CPP_ATTRIBUTE(gnu::format)
#define ABSL_PRINTF_ATTRIBUTE(string_index, first_to_check) \
  [[gnu::format(printf, string_index, first_to_check)]]
#define ABSL_SCANF_ATTRIBUTE(string_index, first_to_check) \
  [[gnu::format(scanf, string_index, first_to_check)]]
#elif ABSL_HAVE_ATTRIBUTE(format)
#define ABSL_PRINTF_ATTRIBUTE(string_index, first_to_check) \
  __attribute__((__format__(__printf__, string_index, first_to_check)))
#define ABSL_SCANF_ATTRIBUTE(string_index, first_to_check) \
  __attribute__((__format__(__scanf__, string_index, first_to_check)))
#else
#define ABSL_PRINTF_ATTRIBUTE(string_index, first_to_check)
#define ABSL_SCANF_ATTRIBUTE(string_index, first_to_check)
#endif

// ABSL_ATTRIBUTE_ALWAYS_INLINE
// ABSL_ATTRIBUTE_NOINLINE
//
// Forces functions to either inline or not inline. Introduced in gcc 3.1.
//
// Note that guarantees are ultimately toolchain-dependent. For example, MSVC
// will not inline any function by default, meaning at least /Ob1 or a higher
// levels of optimization is necessary.
#if ABSL_HAVE_ATTRIBUTE(always_inline)
#define ABSL_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline))
#define ABSL_HAVE_ATTRIBUTE_ALWAYS_INLINE 1
#elif defined(_MSC_VER) && \
    (_MSC_VER >= 1937 ||   \
     (_MSC_VER >= 1927 && ABSL_INTERNAL_CPLUSPLUS_LANG > 201703L))
#define ABSL_ATTRIBUTE_ALWAYS_INLINE [[msvc::forceinline]]
#define ABSL_HAVE_ATTRIBUTE_ALWAYS_INLINE 1
#else
#define ABSL_ATTRIBUTE_ALWAYS_INLINE
#endif

#if ABSL_HAVE_ATTRIBUTE(noinline)
#define ABSL_ATTRIBUTE_NOINLINE __attribute__((noinline))
#define ABSL_HAVE_ATTRIBUTE_NOINLINE 1
#elif defined(_MSC_VER) && \
    (_MSC_VER >= 1937 ||   \
     (_MSC_VER >= 1927 && ABSL_INTERNAL_CPLUSPLUS_LANG > 201703L))
#define ABSL_ATTRIBUTE_NOINLINE [[msvc::noinline]]
#define ABSL_HAVE_ATTRIBUTE_NOINLINE 1
#else
#define ABSL_ATTRIBUTE_NOINLINE
#endif

// ABSL_ATTRIBUTE_NO_TAIL_CALL
//
// Prevents the compiler from optimizing away stack frames for functions which
// end in a call to another function.
#if ABSL_HAVE_ATTRIBUTE(disable_tail_calls)
#define ABSL_HAVE_ATTRIBUTE_NO_TAIL_CALL 1
#define ABSL_ATTRIBUTE_NO_TAIL_CALL __attribute__((disable_tail_calls))
#elif defined(__GNUC__) && !defined(__clang__) && !defined(__e2k__)
#define ABSL_HAVE_ATTRIBUTE_NO_TAIL_CALL 1
#define ABSL_ATTRIBUTE_NO_TAIL_CALL \
  __attribute__((optimize("no-optimize-sibling-calls")))
#else
#define ABSL_ATTRIBUTE_NO_TAIL_CALL
#define ABSL_HAVE_ATTRIBUTE_NO_TAIL_CALL 0
#endif

// ABSL_INTERNAL_MUSTTAIL
//
// Tells the compiler that a `return` statement must be compiled as a tail
// call, reusing the caller's stack frame rather than creating a new one.
// Compilation fails if the compiler cannot generate a tail call.
//
// MANDATORY USAGE REQUIREMENTS:
// * Functionally correct fallback: Code MUST be written with a functionally
//   correct fallback when the attribute is unavailable
//   (`!ABSL_INTERNAL_HAVE_MUSTTAIL`, where `ABSL_INTERNAL_MUSTTAIL` expands to
//   nothing). Never rely on `ABSL_INTERNAL_MUSTTAIL` for program correctness
//   (such as preventing unbounded stack growth in recursive cycles) unless
//   explicitly gated on `#if ABSL_INTERNAL_HAVE_MUSTTAIL` with a non-recursive
//   fallback.
// * Benchmark justification: The performance or code-size impact of using
//   `ABSL_INTERNAL_MUSTTAIL` MUST be clearly demonstrated by benchmarks.
// * This macro is strictly for internal Abseil use and must not be exposed as a
//   public Abseil API.
//
// Technical requirements and limitations:
// * Must be placed immediately before `return`, and the returned expression
//   must be a function call (not wrapped in another expression or conversion).
// * The caller and callee must have compatible function signatures, including
//   matching return types, parameter types, calling conventions, and implicit
//   `this` arguments (a non-static member function can only tail-call another
//   non-static member function of the same class).
// * No variables, temporaries, or by-value parameters with non-trivial
//   destructors may be live at the `return` statement.
// * Arguments to the tail call must not reference local variables or by-value
//   parameters in the caller's stack frame, whose lifetime ends before the
//   callee runs.
// * If the caller is inlined into an outer function where the call is no
//   longer in tail position, the compiler drops `musttail`. It is therefore
//   only effective on out-of-line / non-inlined functions, not `inline`
//   header functions or templates.
// * Only enabled on 64-bit x86 and AArch64, where Clang's backend support for
//   `musttail` is reliable. Other targets (such as 32-bit x86/ARM, PowerPC,
//   and WebAssembly) have incomplete backend tail-call support or compiler
//   crashes even when `__has_cpp_attribute(clang::musttail)` is true (e.g.,
//   https://github.com/llvm/llvm-project/issues/53271).
//
// See: https://clang.llvm.org/docs/AttributeReference.html#musttail
#ifdef ABSL_INTERNAL_HAVE_MUSTTAIL
#error "ABSL_INTERNAL_HAVE_MUSTTAIL cannot be directly set."
#elif defined(ABSL_INTERNAL_MUSTTAIL)
#error "ABSL_INTERNAL_MUSTTAIL cannot be directly set."
#elif ABSL_HAVE_CPP_ATTRIBUTE(clang::musttail) && \
    (defined(__aarch64__) || defined(__x86_64__) || defined(_M_X64))
#define ABSL_INTERNAL_HAVE_MUSTTAIL 1
#define ABSL_INTERNAL_MUSTTAIL [[clang::musttail]]
#else
#define ABSL_INTERNAL_HAVE_MUSTTAIL 0
#define ABSL_INTERNAL_MUSTTAIL
#endif

// ABSL_ATTRIBUTE_WEAK
//
// Tags a function as weak for the purposes of compilation and linking.
// Weak attributes did not work properly in LLVM's Windows backend before
// 9.0.0, so disable them there. See https://bugs.llvm.org/show_bug.cgi?id=37598
// for further information. Weak attributes do not work across DLL boundary.
// The MinGW compiler doesn't complain about the weak attribute until the link
// step, presumably because Windows doesn't use ELF binaries.
#if ABSL_HAVE_ATTRIBUTE(weak) &&                                  \
    (!defined(_WIN32) ||                                          \
     (defined(__clang__) && __clang_major__ >= 9 &&               \
      !defined(ABSL_BUILD_DLL) && !defined(ABSL_CONSUME_DLL))) && \
    !defined(__MINGW32__)
#undef ABSL_ATTRIBUTE_WEAK
#define ABSL_ATTRIBUTE_WEAK __attribute__((weak))
#define ABSL_HAVE_ATTRIBUTE_WEAK 1
#else
#define ABSL_ATTRIBUTE_WEAK
#define ABSL_HAVE_ATTRIBUTE_WEAK 0
#endif

// ABSL_ATTRIBUTE_NONNULL
//
// Tells the compiler either (a) that a particular function parameter
// should be a non-null pointer, or (b) that all pointer arguments should
// be non-null.
//
// Note: As the GCC manual states, "[s]ince non-static C++ methods
// have an implicit 'this' argument, the arguments of such methods
// should be counted from two, not one."
//
// Args are indexed starting at 1.
//
// For non-static class member functions, the implicit `this` argument
// is arg 1, and the first explicit argument is arg 2. For static class member
// functions, there is no implicit `this`, and the first explicit argument is
// arg 1.
//
// Example:
//
//   /* arg_a cannot be null, but arg_b can */
//   void Function(void* arg_a, void* arg_b) ABSL_ATTRIBUTE_NONNULL(1);
//
//   class C {
//     /* arg_a cannot be null, but arg_b can */
//     void Method(void* arg_a, void* arg_b) ABSL_ATTRIBUTE_NONNULL(2);
//
//     /* arg_a cannot be null, but arg_b can */
//     static void StaticMethod(void* arg_a, void* arg_b)
//     ABSL_ATTRIBUTE_NONNULL(1);
//   };
//
// If no arguments are provided, then all pointer arguments should be non-null.
//
//  /* No pointer arguments may be null. */
//  void Function(void* arg_a, void* arg_b, int arg_c) ABSL_ATTRIBUTE_NONNULL();
//
// NOTE: The GCC nonnull attribute actually accepts a list of arguments, but
// ABSL_ATTRIBUTE_NONNULL does not.
#if ABSL_HAVE_ATTRIBUTE(nonnull)
#define ABSL_ATTRIBUTE_NONNULL(arg_index) __attribute__((nonnull(arg_index)))
#else
#define ABSL_ATTRIBUTE_NONNULL(...)
#endif

// ABSL_ATTRIBUTE_NORETURN
//
// Tells the compiler that a given function never returns.
//
// Deprecated: Prefer the `[[noreturn]]` attribute standardized by C++11 over
// this macro.
#ifdef ABSL_ATTRIBUTE_NORETURN
#error "ABSL_ATTRIBUTE_NORETURN should not be defined."
#endif
#define ABSL_ATTRIBUTE_NORETURN [[noreturn]]

// ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS
//
// Tells the AddressSanitizer (or other memory testing tools) to ignore a given
// function. Useful for cases when a function reads random locations on stack,
// calls _exit from a cloned subprocess, deliberately accesses buffer
// out of bounds or does other scary things with memory.
// NOTE: GCC supports AddressSanitizer(asan) since 4.8.
// https://gcc.gnu.org/gcc-4.8/changes.html
#if defined(ABSL_HAVE_ADDRESS_SANITIZER) && \
    ABSL_HAVE_ATTRIBUTE(no_sanitize_address)
#define ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS __attribute__((no_sanitize_address))
#elif defined(ABSL_HAVE_ADDRESS_SANITIZER) && defined(_MSC_VER) && \
    _MSC_VER >= 1928
// https://docs.microsoft.com/en-us/cpp/cpp/no-sanitize-address
#define ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS __declspec(no_sanitize_address)
#elif defined(ABSL_HAVE_HWADDRESS_SANITIZER) && ABSL_HAVE_ATTRIBUTE(no_sanitize)
// HWAddressSanitizer is a sanitizer similar to AddressSanitizer, which uses CPU
// features to detect similar bugs with less CPU and memory overhead.
// NOTE: GCC supports HWAddressSanitizer(hwasan) since 11.
// https://gcc.gnu.org/gcc-11/changes.html
#define ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS \
  __attribute__((no_sanitize("hwaddress")))
#else
#define ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS
#endif

// ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY
//
// Tells the MemorySanitizer to relax the handling of a given function. All "Use
// of uninitialized value" warnings from such functions will be suppressed, and
// all values loaded from memory will be considered fully initialized.  This
// attribute is similar to the ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS attribute
// above, but deals with initialized-ness rather than addressability issues.
// NOTE: MemorySanitizer(msan) is supported by Clang but not GCC.
#if ABSL_HAVE_ATTRIBUTE(no_sanitize_memory)
#define ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY __attribute__((no_sanitize_memory))
#else
#define ABSL_ATTRIBUTE_NO_SANITIZE_MEMORY
#endif

// ABSL_ATTRIBUTE_NO_SANITIZE_THREAD
//
// Tells the ThreadSanitizer to not instrument a given function.
// NOTE: GCC supports ThreadSanitizer(tsan) since 4.8.
// https://gcc.gnu.org/gcc-4.8/changes.html
#if ABSL_HAVE_ATTRIBUTE(no_sanitize_thread)
#define ABSL_ATTRIBUTE_NO_SANITIZE_THREAD __attribute__((no_sanitize_thread))
#else
#define ABSL_ATTRIBUTE_NO_SANITIZE_THREAD
#endif

// ABSL_ATTRIBUTE_NO_SANITIZE_UNDEFINED
//
// Tells the UndefinedSanitizer to ignore a given function. Useful for cases
// where certain behavior (eg. division by zero) is being used intentionally.
// NOTE: GCC supports UndefinedBehaviorSanitizer(ubsan) since 4.9.
// https://gcc.gnu.org/gcc-4.9/changes.html
#if ABSL_HAVE_ATTRIBUTE(no_sanitize_undefined)
#define ABSL_ATTRIBUTE_NO_SANITIZE_UNDEFINED \
  __attribute__((no_sanitize_undefined))
#elif ABSL_HAVE_ATTRIBUTE(no_sanitize)
#define ABSL_ATTRIBUTE_NO_SANITIZE_UNDEFINED \
  __attribute__((no_sanitize("undefined")))
#else
#define ABSL_ATTRIBUTE_NO_SANITIZE_UNDEFINED
#endif

// ABSL_ATTRIBUTE_NO_SANITIZE_CFI
//
// Tells the ControlFlowIntegrity sanitizer to not instrument a given function.
// See https://clang.llvm.org/docs/ControlFlowIntegrity.html for details.
#if ABSL_HAVE_CPP_ATTRIBUTE(gnu::no_sanitize) && defined(__llvm__)
#if defined(__clang__) && !defined(__apple_build_version__) && \
    __clang_major__ >= 16
#define ABSL_ATTRIBUTE_NO_SANITIZE_CFI [[gnu::no_sanitize("cfi", "kcfi")]]
#else
#define ABSL_ATTRIBUTE_NO_SANITIZE_CFI [[gnu::no_sanitize("cfi")]]
#endif
#elif ABSL_HAVE_ATTRIBUTE(no_sanitize) && defined(__llvm__)
#if defined(__clang__) && !defined(__apple_build_version__) && \
    __clang_major__ >= 16
#define ABSL_ATTRIBUTE_NO_SANITIZE_CFI \
  __attribute__((no_sanitize("cfi", "kcfi")))
#else
#define ABSL_ATTRIBUTE_NO_SANITIZE_CFI __attribute__((no_sanitize("cfi")))
#endif
#else
#define ABSL_ATTRIBUTE_NO_SANITIZE_CFI
#endif

// ABSL_ATTRIBUTE_NO_SANITIZE_SAFESTACK
//
// Tells the SafeStack to not instrument a given function.
// See https://clang.llvm.org/docs/SafeStack.html for details.
#if ABSL_HAVE_ATTRIBUTE(no_sanitize)
#define ABSL_ATTRIBUTE_NO_SANITIZE_SAFESTACK \
  __attribute__((no_sanitize("safe-stack")))
#else
#define ABSL_ATTRIBUTE_NO_SANITIZE_SAFESTACK
#endif

// ABSL_ATTRIBUTE_RETURNS_NONNULL
//
// Tells the compiler that a particular function never returns a null pointer.
#if ABSL_HAVE_CPP_ATTRIBUTE(gnu::returns_nonnull)
#define ABSL_ATTRIBUTE_RETURNS_NONNULL [[gnu::returns_nonnull]]
#elif ABSL_HAVE_ATTRIBUTE(returns_nonnull)
#define ABSL_ATTRIBUTE_RETURNS_NONNULL __attribute__((returns_nonnull))
#else
#define ABSL_ATTRIBUTE_RETURNS_NONNULL
#endif

// ABSL_HAVE_ATTRIBUTE_SECTION
//
// Indicates whether labeled sections are supported. Weak symbol support is
// a prerequisite. Labeled sections are not supported on Darwin/iOS.
#ifdef ABSL_HAVE_ATTRIBUTE_SECTION
#error ABSL_HAVE_ATTRIBUTE_SECTION cannot be directly set
#elif ABSL_HAVE_ATTRIBUTE(section) && !defined(__APPLE__) && \
    ABSL_HAVE_ATTRIBUTE_WEAK
#define ABSL_HAVE_ATTRIBUTE_SECTION 1

// ABSL_ATTRIBUTE_SECTION
//
// Tells the compiler/linker to put a given function into a section and define
// `__start_ ## name` and `__stop_ ## name` symbols to bracket the section.
// This functionality is supported by GNU linker.  Any function annotated with
// `ABSL_ATTRIBUTE_SECTION` must not be inlined, or it will be placed into
// whatever section its caller is placed into.
//
#ifndef ABSL_ATTRIBUTE_SECTION
#define ABSL_ATTRIBUTE_SECTION(name) \
  __attribute__((section(#name))) __attribute__((noinline))
#endif

// ABSL_ATTRIBUTE_SECTION_VARIABLE
//
// Tells the compiler/linker to put a given variable into a section and define
// `__start_ ## name` and `__stop_ ## name` symbols to bracket the section.
// This functionality is supported by GNU linker.
#ifndef ABSL_ATTRIBUTE_SECTION_VARIABLE
#ifdef _AIX
// __attribute__((section(#name))) on AIX is achieved by using the `.csect`
// pseudo op which includes an additional integer as part of its syntax
// indicating alignment. If data fall under different alignments then you might
// get a compilation error indicating a `Section type conflict`.
#define ABSL_ATTRIBUTE_SECTION_VARIABLE(name)
#elif ABSL_HAVE_CPP_ATTRIBUTE(gnu::section)
#define ABSL_ATTRIBUTE_SECTION_VARIABLE(name) [[gnu::section(#name)]]
#else
#define ABSL_ATTRIBUTE_SECTION_VARIABLE(name) __attribute__((section(#name)))
#endif
#endif

// ABSL_DECLARE_ATTRIBUTE_SECTION_VARS
//
// A weak section declaration to be used as a global declaration
// for ABSL_ATTRIBUTE_SECTION_START|STOP(name) to compile and link
// even without functions with ABSL_ATTRIBUTE_SECTION(name).
// ABSL_DEFINE_ATTRIBUTE_SECTION should be in the exactly one file; it's
// a no-op on ELF but not on Mach-O.
//
#ifndef ABSL_DECLARE_ATTRIBUTE_SECTION_VARS
#define ABSL_DECLARE_ATTRIBUTE_SECTION_VARS(name)   \
  extern char __start_##name[] ABSL_ATTRIBUTE_WEAK; \
  extern char __stop_##name[] ABSL_ATTRIBUTE_WEAK
#endif
#ifndef ABSL_DEFINE_ATTRIBUTE_SECTION_VARS
#define ABSL_INIT_ATTRIBUTE_SECTION_VARS(name)
#define ABSL_DEFINE_ATTRIBUTE_SECTION_VARS(name)
#endif

// ABSL_ATTRIBUTE_SECTION_START
//
// Returns `void*` pointers to start/end of a section of code with
// functions having ABSL_ATTRIBUTE_SECTION(name).
// Returns 0 if no such functions exist.
// One must ABSL_DECLARE_ATTRIBUTE_SECTION_VARS(name) for this to compile and
// link.
//
#define ABSL_ATTRIBUTE_SECTION_START(name) \
  (reinterpret_cast<void*>(__start_##name))
#define ABSL_ATTRIBUTE_SECTION_STOP(name) \
  (reinterpret_cast<void*>(__stop_##name))

#else  // !ABSL_HAVE_ATTRIBUTE_SECTION

#define ABSL_HAVE_ATTRIBUTE_SECTION 0

// provide dummy definitions
#define ABSL_ATTRIBUTE_SECTION(name)
#define ABSL_ATTRIBUTE_SECTION_VARIABLE(name)
#define ABSL_INIT_ATTRIBUTE_SECTION_VARS(name)
#define ABSL_DEFINE_ATTRIBUTE_SECTION_VARS(name)
#define ABSL_DECLARE_ATTRIBUTE_SECTION_VARS(name)
#define ABSL_ATTRIBUTE_SECTION_START(name) (reinterpret_cast<void*>(0))
#define ABSL_ATTRIBUTE_SECTION_STOP(name) (reinterpret_cast<void*>(0))

#endif  // ABSL_ATTRIBUTE_SECTION

// ABSL_ATTRIBUTE_STACK_ALIGN_FOR_OLD_LIBC
//
// Support for aligning the stack on 32-bit x86.
#if ABSL_HAVE_ATTRIBUTE(force_align_arg_pointer)
#if defined(__i386__)
#if ABSL_HAVE_CPP_ATTRIBUTE(gnu::force_align_arg_pointer)
#define ABSL_ATTRIBUTE_STACK_ALIGN_FOR_OLD_LIBC [[gnu::force_align_arg_pointer]]
#else
#define ABSL_ATTRIBUTE_STACK_ALIGN_FOR_OLD_LIBC \
  __attribute__((force_align_arg_pointer))
#endif
#define ABSL_REQUIRE_STACK_ALIGN_TRAMPOLINE (0)
#elif defined(__x86_64__)
#define ABSL_REQUIRE_STACK_ALIGN_TRAMPOLINE (1)
#define ABSL_ATTRIBUTE_STACK_ALIGN_FOR_OLD_LIBC
#else  // !__i386__ && !__x86_64
#define ABSL_REQUIRE_STACK_ALIGN_TRAMPOLINE (0)
#define ABSL_ATTRIBUTE_STACK_ALIGN_FOR_OLD_LIBC
#endif  // __i386__
#else
#define ABSL_ATTRIBUTE_STACK_ALIGN_FOR_OLD_LIBC
#define ABSL_REQUIRE_STACK_ALIGN_TRAMPOLINE (0)
#endif

// ABSL_MUST_USE_RESULT
//
// Tells the compiler to warn about unused results.
//
// Deprecated: Use the standard C++17 `[[nodiscard]]` instead.
//
// When annotating a function, it must appear as the first part of the
// declaration or definition. The compiler will warn if the return value from
// such a function is unused:
//
//   ABSL_MUST_USE_RESULT Sprocket* AllocateSprocket();
//   AllocateSprocket();  // Triggers a warning.
//
// When annotating a class, it is equivalent to annotating every function which
// returns an instance.
//
//   class ABSL_MUST_USE_RESULT Sprocket {};
//   Sprocket();  // Triggers a warning.
//
//   Sprocket MakeSprocket();
//   MakeSprocket();  // Triggers a warning.
//
// Note that references and pointers are not instances:
//
//   Sprocket* SprocketPointer();
//   SprocketPointer();  // Does *not* trigger a warning.
#ifdef ABSL_MUST_USE_RESULT
#error "ABSL_MUST_USE_RESULT should not be defined."
#endif
#define ABSL_MUST_USE_RESULT [[nodiscard]]

// ABSL_ATTRIBUTE_HOT, ABSL_ATTRIBUTE_COLD
//
// Tells GCC that a function is hot or cold. GCC can use this information to
// improve static analysis, i.e. a conditional branch to a cold function
// is likely to be not-taken.
// This annotation is used for function declarations.
//
// Example:
//
//   int foo() ABSL_ATTRIBUTE_HOT;
#if defined(__cplusplus) && ABSL_HAVE_CPP_ATTRIBUTE(gnu::hot)
#define ABSL_ATTRIBUTE_HOT [[gnu::hot]]
#elif ABSL_HAVE_ATTRIBUTE(hot)
#define ABSL_ATTRIBUTE_HOT __attribute__((hot))
#else
#define ABSL_ATTRIBUTE_HOT
#endif

#if defined(__cplusplus) && ABSL_HAVE_CPP_ATTRIBUTE(gnu::cold)
#define ABSL_ATTRIBUTE_COLD [[gnu::cold]]
#elif ABSL_HAVE_ATTRIBUTE(cold)
#define ABSL_ATTRIBUTE_COLD __attribute__((cold))
#else
#define ABSL_ATTRIBUTE_COLD
#endif

// ABSL_XRAY_ALWAYS_INSTRUMENT, ABSL_XRAY_NEVER_INSTRUMENT, ABSL_XRAY_LOG_ARGS
//
// We define the ABSL_XRAY_ALWAYS_INSTRUMENT and ABSL_XRAY_NEVER_INSTRUMENT
// macro used as an attribute to mark functions that must always or never be
// instrumented by XRay. Currently, this is only supported in Clang/LLVM.
//
// For reference on the LLVM XRay instrumentation, see
// http://llvm.org/docs/XRay.html.
//
// A function with the XRAY_ALWAYS_INSTRUMENT macro attribute in its declaration
// will always get the XRay instrumentation sleds. These sleds may introduce
// some binary size and runtime overhead and must be used sparingly.
//
// These attributes only take effect when the following conditions are met:
//
//   * The file/target is built with a Clang compiler that supports XRay
//     attributes.
//   * The file/target is built with the -fxray-instrument flag set for the
//     Clang/LLVM compiler.
//   * The function is defined in the translation unit (the compiler honors the
//     attribute in either the definition or the declaration, and must match).
//
// There are cases when, even when building with XRay instrumentation, users
// might want to control specifically which functions are instrumented for a
// particular build using special-case lists provided to the compiler. These
// special case lists are provided to Clang via the
// -fxray-always-instrument=... and -fxray-never-instrument=... flags. The
// attributes in source take precedence over these special-case lists.
//
// To disable the XRay attributes at build-time, users may define
// ABSL_NO_XRAY_ATTRIBUTES. Do NOT define ABSL_NO_XRAY_ATTRIBUTES on specific
// packages/targets, as this may lead to conflicting definitions of functions at
// link-time.
//
// XRay isn't currently supported on Android:
// https://github.com/android/ndk/issues/368
#if ABSL_HAVE_CPP_ATTRIBUTE(clang::xray_always_instrument) && \
    !defined(ABSL_NO_XRAY_ATTRIBUTES) && !defined(__ANDROID__)
#define ABSL_XRAY_ALWAYS_INSTRUMENT [[clang::xray_always_instrument]]
#define ABSL_XRAY_NEVER_INSTRUMENT [[clang::xray_never_instrument]]
#if ABSL_HAVE_CPP_ATTRIBUTE(clang::xray_log_args)
#define ABSL_XRAY_LOG_ARGS(N) \
  [[clang::xray_always_instrument, clang::xray_log_args(N)]]
#else
#define ABSL_XRAY_LOG_ARGS(N) [[clang::xray_always_instrument]]
#endif
#else
#define ABSL_XRAY_ALWAYS_INSTRUMENT
#define ABSL_XRAY_NEVER_INSTRUMENT
#define ABSL_XRAY_LOG_ARGS(N)
#endif

// ABSL_ATTRIBUTE_NULL_AFTER_MOVE
//
// Indicates that a user-defined smart-pointer-like type makes guarantees on the
// state of a moved-from object, leaving it in a null state, where it can be
// used as long as it is not dereferenced. In other words, these are the same
// semantics that smart pointers from the standard library provide.
//
// The clang-tidy check bugprone-use-after-move allows member functions of types
// marked with this attribute to be called on objects that have been moved from;
// without the attribute, this would result in a use-after-move warning.
#if ABSL_HAVE_CPP_ATTRIBUTE(clang::annotate) && defined(__clang__) && \
    __clang_major__ >= 12
#define ABSL_ATTRIBUTE_NULL_AFTER_MOVE                       \
  [[clang::annotate("clang-tidy", "bugprone-use-after-move", \
                    "null_after_move")]]
#else
#define ABSL_ATTRIBUTE_NULL_AFTER_MOVE
#endif

// ABSL_ATTRIBUTE_REINITIALIZES
//
// Indicates that a member function reinitializes the entire object to a known
// state, independent of the previous state of the object.
//
// The clang-tidy check bugprone-use-after-move allows member functions marked
// with this attribute to be called on objects that have been moved from;
// without the attribute, this would result in a use-after-move warning.
#if ABSL_HAVE_CPP_ATTRIBUTE(clang::reinitializes)
#define ABSL_ATTRIBUTE_REINITIALIZES [[clang::reinitializes]]
#else
#define ABSL_ATTRIBUTE_REINITIALIZES
#endif

// -----------------------------------------------------------------------------
// Variable Attributes
// -----------------------------------------------------------------------------

// ABSL_ATTRIBUTE_UNUSED
//
// Prevents the compiler from complaining about variables that appear unused.
//
// Deprecated: Use the standard C++17 `[[maybe_unused]]` instead.
//
// Due to differences in positioning requirements between the old, compiler
// specific __attribute__ syntax and the now standard `[[maybe_unused]]`, this
// macro does not attempt to take advantage of `[[maybe_unused]]`.
#ifdef ABSL_ATTRIBUTE_UNUSED
#error "ABSL_ATTRIBUTE_UNUSED should not be defined."
#endif
#if defined(__cplusplus) && defined(__clang__) && \
    ABSL_HAVE_ATTRIBUTE(diagnose_if) && !defined(SWIG)
struct [[deprecated("Use [[maybe_unused]] instead.")]] _absl_unused_macro;
// Trick: We use __attribute__((diagnose_if(...))) to refer to our own
// deprecated symbol, which then causes a deprecation message to be emitted when
// the macro is used. Since diagnose_if() isn't valid on every declaration, we
// also suppress the warning regarding that.
#define ABSL_ATTRIBUTE_UNUSED                                                \
  [[maybe_unused]]                                                           \
  _Pragma("clang diagnostic push") /*                                     */ \
      _Pragma("clang diagnostic ignored \"-Wignored-attributes\"")           \
          __attribute__((diagnose_if(                                        \
              sizeof(_absl_unused_macro*) == 0, "",                          \
              "warning"))) /*                                             */ \
          _Pragma("clang diagnostic pop")
#else
#define ABSL_ATTRIBUTE_UNUSED [[maybe_unused]]
#endif

// ABSL_ATTRIBUTE_INITIAL_EXEC
//
// Tells the compiler to use "initial-exec" mode for a thread-local variable.
// See http://people.redhat.com/drepper/tls.pdf for the gory details.
#if ABSL_HAVE_CPP_ATTRIBUTE(gnu::tls_model)
#define ABSL_ATTRIBUTE_INITIAL_EXEC [[gnu::tls_model("initial-exec")]]
#elif ABSL_HAVE_ATTRIBUTE(tls_model)
#define ABSL_ATTRIBUTE_INITIAL_EXEC __attribute__((tls_model("initial-exec")))
#else
#define ABSL_ATTRIBUTE_INITIAL_EXEC
#endif

// ABSL_ATTRIBUTE_PACKED
//
// Instructs the compiler not to use natural alignment for a tagged data
// structure, but instead to reduce its alignment to 1.
//
// Use of this attribute is HIGHLY DISCOURAGED. Taking the address of or
// binding a reference to any unaligned member is UB, and it is very easy to
// do so unintentionally when passing such members as function arguments.
//
// DO NOT APPLY THIS ATTRIBUTE TO STRUCTS CONTAINING ATOMICS. Doing
// so can cause atomic variables to be mis-aligned and silently violate
// atomicity on x86.
//
// This attribute can either be applied to members of a structure or to a
// structure in its entirety. Applying this attribute (judiciously) to a
// structure in its entirety to optimize the memory footprint of very
// commonly-used structs is fine. Do not apply this attribute to a structure in
// its entirety if the purpose is to control the offsets of the members in the
// structure. Instead, apply this attribute only to structure members that need
// it.
//
// When applying ABSL_ATTRIBUTE_PACKED only to specific structure members the
// natural alignment of structure members not annotated is preserved. Aligned
// member accesses are faster than non-aligned member accesses even if the
// targeted microprocessor supports non-aligned accesses.
#if ABSL_HAVE_ATTRIBUTE(packed)
#define ABSL_ATTRIBUTE_PACKED __attribute__((__packed__))
#else
#define ABSL_ATTRIBUTE_PACKED
#endif

// ABSL_ATTRIBUTE_FUNC_ALIGN
//
// Tells the compiler to align the function start at least to certain
// alignment boundary
#if ABSL_HAVE_CPP_ATTRIBUTE(gnu::aligned)
#define ABSL_ATTRIBUTE_FUNC_ALIGN(bytes) [[gnu::aligned(bytes)]]
#elif ABSL_HAVE_ATTRIBUTE(aligned)
#define ABSL_ATTRIBUTE_FUNC_ALIGN(bytes) __attribute__((aligned(bytes)))
#else
#define ABSL_ATTRIBUTE_FUNC_ALIGN(bytes)
#endif

// ABSL_FALLTHROUGH_INTENDED
//
// Annotates implicit fall-through between switch labels, allowing a case to
// indicate intentional fallthrough and turn off warnings about any lack of a
// `break` statement.
//
// Deprecated: Use the standard C++17 `[[fallthrough]]` instead.
//
// This macro has no effect on runtime behavior and performance of code.

#ifdef ABSL_FALLTHROUGH_INTENDED
#error "ABSL_FALLTHROUGH_INTENDED should not be defined."
#endif
#define ABSL_FALLTHROUGH_INTENDED                                         \
  struct [[deprecated(                                                    \
      "Use [[fallthrough]] instead.")]] _absl_fallthrough_intended_macro; \
  (void)sizeof(_absl_fallthrough_intended_macro*);                        \
  [[fallthrough]]

// ABSL_DEPRECATED()
//
// Marks a deprecated class, struct, enum, function, method and variable
// declarations. The macro argument is used as a custom diagnostic message (e.g.
// suggestion of a better alternative).
//
// Deprecated: Use the standard `[[deprecated("message")]]` macro instead.
//
// Examples:
//
//   class ABSL_DEPRECATED("Use Bar instead") Foo {...};
//
//   ABSL_DEPRECATED("Use Baz() instead") void Bar() {...}
//
//   template <typename T>
//   ABSL_DEPRECATED("Use DoThat() instead")
//   void DoThis();
//
//   enum FooEnum {
//     kBar ABSL_DEPRECATED("Use kBaz instead"),
//   };
//
// Every usage of a deprecated entity will trigger a warning when compiled with
// GCC/Clang's `-Wdeprecated-declarations` option. Google's production toolchain
// turns this warning off by default, instead relying on clang-tidy to report
// new uses of deprecated code.
#ifdef ABSL_DEPRECATED
#error "ABSL_DEPRECATED should not be defined."
#endif
#if ABSL_HAVE_ATTRIBUTE(deprecated)
#define ABSL_DEPRECATED(message) [[deprecated(message)]]
#else
#define ABSL_DEPRECATED(message)
#endif

// When deprecating Abseil code, it is sometimes necessary to turn off the
// warning within Abseil, until the deprecated code is actually removed. The
// deprecated code can be surrounded with these directives to achieve that
// result.
//
// class [[deprecated("Use Bar instead")]] Foo;
//
// ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
// Baz ComputeBazFromFoo(Foo f);
// ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
#if defined(__GNUC__) || defined(__clang__)
// Clang also supports these GCC pragmas.
#define ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING \
  _Pragma("GCC diagnostic push")                             \
      _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"")
#define ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING \
  _Pragma("GCC diagnostic pop")
#elif defined(_MSC_VER)
#define ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING \
  _Pragma("warning(push)") _Pragma("warning(disable: 4996)")
#define ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING \
  _Pragma("warning(pop)")
#else
#define ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING
#define ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING
#endif  // defined(__GNUC__) || defined(__clang__)

// ABSL_REQUIRE_EXPLICIT_INIT
//
// ABSL_REQUIRE_EXPLICIT_INIT is placed *after* the data members of an aggregate
// type to indicate that the annotated member must be explicitly initialized by
// the user whenever the aggregate is constructed. For example:
//
//   struct Coord {
//     int x ABSL_REQUIRE_EXPLICIT_INIT;
//     int y ABSL_REQUIRE_EXPLICIT_INIT;
//   };
//   Coord coord = {1};  // warning: field 'y' is not explicitly initialized
//
// Note that usage on C arrays is not supported in C++.
// Use a struct (such as std::array) to wrap the array member instead.
//
// Avoid applying this attribute to the members of non-aggregate types.
// The behavior within non-aggregates is unspecified and subject to change.
//
// Do NOT attempt to suppress or demote the error generated by this attribute.
// Just like with a missing function argument, it is a hard error by design.
//
// See the upstream documentation for more details:
// https://clang.llvm.org/docs/AttributeReference.html#require-explicit-initialization
#if defined(__cplusplus) && !defined(SWIG)
#if defined(_MSC_VER) && !defined(__clang__)
// Workaround for MSVC: https://github.com/abseil/abseil-cpp/issues/2157
#define ABSL_REQUIRE_EXPLICIT_INIT
#elif ABSL_HAVE_CPP_ATTRIBUTE(clang::require_explicit_initialization)
#define ABSL_REQUIRE_EXPLICIT_INIT             \
  [[clang::require_explicit_initialization]] = \
      AbslInternal_YouForgotToExplicitlyInitializeAField::v
#else
#define ABSL_REQUIRE_EXPLICIT_INIT \
  = AbslInternal_YouForgotToExplicitlyInitializeAField::v
#endif
#else
#if ABSL_HAVE_ATTRIBUTE(require_explicit_initialization)
#define ABSL_REQUIRE_EXPLICIT_INIT \
  __attribute__((require_explicit_initialization))
#else
// No portable fallback for C is available
#define ABSL_REQUIRE_EXPLICIT_INIT
#endif
#endif

#if defined(__cplusplus) && !defined(SWIG)
struct AbslInternal_YouForgotToExplicitlyInitializeAField {
  // A portable version of [[clang::require_explicit_initialization]] that
  // never builds, as a last resort for all toolchains.
  // The error messages are poor, so we don't rely on this unless we have to.
  template <class T>
  constexpr operator T() const /* NOLINT */ {
    const void* volatile deliberately_volatile_ptr = nullptr;
    // Infinite loop to prevent constexpr compilation
    for (;;) {
      // This assignment ensures the 'this' pointer is not optimized away, so
      // that linking always fails.
      deliberately_volatile_ptr = this;  // Deliberately not constexpr
      (void)deliberately_volatile_ptr;
    }
  }
  // This is deliberately left undefined to prevent linking
  static AbslInternal_YouForgotToExplicitlyInitializeAField v;
};
#endif

// ABSL_CONST_INIT
//
// A variable declared with `ABSL_CONST_INIT` will not compile (on supported
// platforms) unless the variable has a constant initializer. This is useful for
// variables with static and thread storage duration, because it guarantees that
// they will not suffer from the so-called "static init order fiasco".
//
// `ABSL_CONST_INIT` must be placed on the initializing declaration
// (i.e. definition) of the variable. Some compilers will give a
// `-Wmissing-constinit` warning when it is placed on some other
// declaration but missing from the initializing declaration.
//
// For thread_local variables, placing `ABSL_CONST_INIT` on the non-initializing
// declaration tells the compiler that the variable is already initialized,
// reducing overhead that would otherwise be incurred by a hidden guard
// variable.
//
// Example:
//
//   class MyClass {
//    public:
//     ABSL_CONST_INIT static MyType my_var;
//   };
//
//   ABSL_CONST_INIT MyType MyClass::my_var = MakeMyType(...);
//
// For code or headers that are assured to only build with C++20 and up, prefer
// using the standard `constinit` keyword directly over this macro.
//
// Note that `ABSL_CONST_INIT` must not be used on a variable declared
// constexpr.
#if defined(__cpp_constinit) && __cpp_constinit >= 201907L
#define ABSL_CONST_INIT constinit  // NOLINT(clang-diagnostic-pre-c++20-compat)
#elif ABSL_HAVE_CPP_ATTRIBUTE(clang::require_constant_initialization)
#define ABSL_CONST_INIT [[clang::require_constant_initialization]]
#else
#define ABSL_CONST_INIT
#endif

// ABSL_ATTRIBUTE_PURE_FUNCTION
//
// ABSL_ATTRIBUTE_PURE_FUNCTION is used to annotate declarations of "pure"
// functions. A function is pure if its return value is only a function of its
// arguments. The pure attribute prohibits a function from modifying the state
// of the program that is observable by means other than inspecting the
// function's return value. Declaring such functions with the pure attribute
// allows the compiler to avoid emitting some calls in repeated invocations of
// the function with the same argument values.
//
// Example:
//
//  ABSL_ATTRIBUTE_PURE_FUNCTION std::string FormatTime(Time t);
#if ABSL_HAVE_CPP_ATTRIBUTE(gnu::pure)
#define ABSL_ATTRIBUTE_PURE_FUNCTION [[gnu::pure]]
#elif ABSL_HAVE_ATTRIBUTE(pure)
#define ABSL_ATTRIBUTE_PURE_FUNCTION __attribute__((pure))
#else
// If the attribute isn't defined, we'll fallback to ABSL_MUST_USE_RESULT since
// pure functions are useless if its return is ignored.
#define ABSL_ATTRIBUTE_PURE_FUNCTION ABSL_MUST_USE_RESULT
#endif

// ABSL_ATTRIBUTE_CONST_FUNCTION
//
// ABSL_ATTRIBUTE_CONST_FUNCTION is used to annotate declarations of "const"
// functions. A const function is similar to a pure function, with one
// exception: Pure functions may return value that depend on a non-volatile
// object that isn't provided as a function argument, while the const function
// is guaranteed to return the same result given the same arguments.
//
// Example:
//
//  ABSL_ATTRIBUTE_CONST_FUNCTION int64_t ToInt64Milliseconds(Duration d);
#if defined(_MSC_VER) && !defined(__clang__)
// Put the MSVC case first since MSVC seems to parse const as a C++ keyword.
#define ABSL_ATTRIBUTE_CONST_FUNCTION ABSL_ATTRIBUTE_PURE_FUNCTION
#elif ABSL_HAVE_CPP_ATTRIBUTE(gnu::const)
#define ABSL_ATTRIBUTE_CONST_FUNCTION [[gnu::const]]
#elif ABSL_HAVE_ATTRIBUTE(const)
#define ABSL_ATTRIBUTE_CONST_FUNCTION __attribute__((const))
#else
// Since const functions are more restrictive pure function, we'll fallback to a
// pure function if the const attribute is not handled.
#define ABSL_ATTRIBUTE_CONST_FUNCTION ABSL_ATTRIBUTE_PURE_FUNCTION
#endif

// ABSL_ATTRIBUTE_LIFETIME_BOUND indicates that a resource owned by a function
// parameter or implicit object parameter is retained by the return value of the
// annotated function (or, for a parameter of a constructor, in the value of the
// constructed object). This attribute causes warnings to be produced if a
// temporary object does not live long enough.
//
// When applied to a reference parameter, the referenced object is assumed to be
// retained by the return value of the function. When applied to a non-reference
// parameter (for example, a pointer or a class type), all temporaries
// referenced by the parameter are assumed to be retained by the return value of
// the function.
//
// See also the upstream documentation:
// https://clang.llvm.org/docs/AttributeReference.html#lifetimebound
// https://learn.microsoft.com/en-us/cpp/code-quality/c26816?view=msvc-170
#if ABSL_HAVE_CPP_ATTRIBUTE(clang::lifetimebound)
#define ABSL_ATTRIBUTE_LIFETIME_BOUND [[clang::lifetimebound]]
#elif ABSL_HAVE_CPP_ATTRIBUTE(msvc::lifetimebound)
#define ABSL_ATTRIBUTE_LIFETIME_BOUND [[msvc::lifetimebound]]
#elif ABSL_HAVE_ATTRIBUTE(lifetimebound)
#define ABSL_ATTRIBUTE_LIFETIME_BOUND __attribute__((lifetimebound))
#else
#define ABSL_ATTRIBUTE_LIFETIME_BOUND
#endif

// Internal attribute; name and documentation TBD.
//
// See the upstream documentation:
// https://clang.llvm.org/docs/AttributeReference.html#lifetime_capture_by
#if ABSL_HAVE_CPP_ATTRIBUTE(clang::lifetime_capture_by)
#define ABSL_INTERNAL_ATTRIBUTE_CAPTURED_BY(Owner) \
  [[clang::lifetime_capture_by(Owner)]]
#else
#define ABSL_INTERNAL_ATTRIBUTE_CAPTURED_BY(Owner)
#endif

// Internal attribute; name and documentation TBD.
//
// See the upstream documentation:
// https://clang.llvm.org/docs/AttributeReference.html#lifetime_capture_by_this
//
// Note: ABSL_INTERNAL_ATTRIBUTE_CAPTURED_BY(this) is deprecated. Use
// ABSL_INTERNAL_ATTRIBUTE_CAPTURED_BY_THIS instead.
#if ABSL_HAVE_CPP_ATTRIBUTE(clang::lifetime_capture_by_this)
#define ABSL_INTERNAL_ATTRIBUTE_CAPTURED_BY_THIS \
  [[clang::lifetime_capture_by_this]]
#elif ABSL_HAVE_CPP_ATTRIBUTE(clang::lifetime_capture_by)
#define ABSL_INTERNAL_ATTRIBUTE_CAPTURED_BY_THIS \
  ABSL_INTERNAL_ATTRIBUTE_CAPTURED_BY(this)
#else
#define ABSL_INTERNAL_ATTRIBUTE_CAPTURED_BY_THIS
#endif

// ABSL_ATTRIBUTE_VIEW indicates that a type is solely a "view" of data that it
// points to, similarly to a span, string_view, or other non-owning reference
// type.
// This enables diagnosing certain lifetime issues similar to those enabled by
// ABSL_ATTRIBUTE_LIFETIME_BOUND, such as:
//
//   struct ABSL_ATTRIBUTE_VIEW StringView {
//     template<class R>
//     StringView(const R&);
//   };
//
//   StringView f(std::string s) {
//     return s;  // warning: address of stack memory returned
//   }
//
// We disable this on Clang versions < 13 because of the following
// false-positive:
//
//   absl::string_view f(std::optional<absl::string_view> sv) { return *sv; }
//
// See the following links for details:
// https://reviews.llvm.org/D64448
// https://lists.llvm.org/pipermail/cfe-dev/2018-November/060355.html
#if ABSL_HAVE_CPP_ATTRIBUTE(gsl::Pointer) && \
    (!defined(__clang_major__) || __clang_major__ >= 13)
#define ABSL_ATTRIBUTE_VIEW [[gsl::Pointer]]
#else
#define ABSL_ATTRIBUTE_VIEW
#endif

// ABSL_ATTRIBUTE_OWNER indicates that a type is a container, smart pointer, or
// similar class that owns all the data that it points to.
// This enables diagnosing certain lifetime issues similar to those enabled by
// ABSL_ATTRIBUTE_LIFETIME_BOUND, such as:
//
//   struct ABSL_ATTRIBUTE_VIEW StringView {
//     template<class R>
//     StringView(const R&);
//   };
//
//   struct ABSL_ATTRIBUTE_OWNER String {};
//
//   StringView f(String s) {
//     return s;  // warning: address of stack memory returned
//   }
//
// We disable this on Clang versions < 13 because of the following
// false-positive:
//
//   absl::string_view f(std::optional<absl::string_view> sv) { return *sv; }
//
// See the following links for details:
// https://reviews.llvm.org/D64448
// https://lists.llvm.org/pipermail/cfe-dev/2018-November/060355.html
#if ABSL_HAVE_CPP_ATTRIBUTE(gsl::Owner) && \
    (!defined(__clang_major__) || __clang_major__ >= 13)
#define ABSL_ATTRIBUTE_OWNER [[gsl::Owner]]
#else
#define ABSL_ATTRIBUTE_OWNER
#endif

// ABSL_ATTRIBUTE_TRIVIAL_ABI
// Indicates that a type is "trivially relocatable" -- meaning it can be
// relocated without invoking the constructor/destructor, using a form of move
// elision.
//
// From a memory safety point of view, putting aside destructor ordering, it's
// safe to apply ABSL_ATTRIBUTE_TRIVIAL_ABI if an object's location
// can change over the course of its lifetime: if a constructor can be run one
// place, and then the object magically teleports to another place where some
// methods are run, and then the object teleports to yet another place where it
// is destroyed. This is notably not true for self-referential types, where the
// move-constructor must keep the self-reference up to date. If the type changed
// location without invoking the move constructor, it would have a dangling
// self-reference.
//
// The use of this teleporting machinery means that the number of paired
// move/destroy operations can change, and so it is a bad idea to apply this to
// a type meant to count the number of moves.
//
// Warning: applying this can, rarely, break callers. Objects passed by value
// will be destroyed at the end of the call, instead of the end of the
// full-expression containing the call. In addition, it changes the ABI
// of functions accepting this type by value (e.g. to pass in registers).
//
// See also the upstream documentation:
// https://clang.llvm.org/docs/AttributeReference.html#trivial-abi
//
// b/321691395 - This is currently disabled in open-source builds since
// compiler support differs. If system libraries compiled with GCC are mixed
// with libraries compiled with Clang, types will have different ideas about
// their ABI, leading to hard to debug crashes.
#define ABSL_ATTRIBUTE_TRIVIAL_ABI

// ABSL_ATTRIBUTE_NO_UNIQUE_ADDRESS
//
// Indicates a data member can be optimized to occupy no space (if it is empty)
// and/or its tail padding can be used for other members.
//
// For code that is assured to only build with C++20 or later, prefer using
// the standard attribute `[[no_unique_address]]` directly instead of this
// macro.
//
// https://devblogs.microsoft.com/cppblog/msvc-cpp20-and-the-std-cpp20-switch/#c20-no_unique_address
// Current versions of MSVC have disabled `[[no_unique_address]]` since it
// breaks ABI compatibility, but offers `[[msvc::no_unique_address]]` for
// situations when it can be assured that it is desired. Since Abseil does not
// claim ABI compatibility in mixed builds, we can offer it unconditionally.
#if defined(_MSC_VER) && _MSC_VER >= 1929
#define ABSL_ATTRIBUTE_NO_UNIQUE_ADDRESS [[msvc::no_unique_address]]
#elif ABSL_HAVE_CPP_ATTRIBUTE(no_unique_address)
#define ABSL_ATTRIBUTE_NO_UNIQUE_ADDRESS [[no_unique_address]]
#else
#define ABSL_ATTRIBUTE_NO_UNIQUE_ADDRESS
#endif

// ABSL_ATTRIBUTE_UNINITIALIZED
//
// GCC and Clang support a flag `-ftrivial-auto-var-init=<option>` (<option>
// can be "zero" or "pattern") that can be used to initialize automatic stack
// variables. Variables with this attribute will be left uninitialized,
// overriding the compiler flag.
//
// See https://clang.llvm.org/docs/AttributeReference.html#uninitialized
// and
// https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-uninitialized-variable-attribute
#if ABSL_HAVE_CPP_ATTRIBUTE(clang::uninitialized)
#define ABSL_ATTRIBUTE_UNINITIALIZED [[clang::uninitialized]]
#elif ABSL_HAVE_ATTRIBUTE(uninitialized)
#define ABSL_ATTRIBUTE_UNINITIALIZED __attribute__((uninitialized))
#else
#define ABSL_ATTRIBUTE_UNINITIALIZED
#endif

// ABSL_ATTRIBUTE_WARN_UNUSED
//
// Compilers routinely warn about trivial variables that are unused.  For
// non-trivial types, this warning is suppressed since the
// constructor/destructor may be intentional and load-bearing, for example, with
// a RAII scoped lock.
//
// For example:
//
// class ABSL_ATTRIBUTE_WARN_UNUSED MyType {
//  public:
//   MyType();
//   ~MyType();
// };
//
// void foo() {
//   // Warns with ABSL_ATTRIBUTE_WARN_UNUSED attribute present.
//   MyType unused;
// }
//
// See https://clang.llvm.org/docs/AttributeReference.html#warn-unused and
// https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Attributes.html#index-warn_005funused-type-attribute
#if ABSL_HAVE_CPP_ATTRIBUTE(gnu::warn_unused)
#define ABSL_ATTRIBUTE_WARN_UNUSED [[gnu::warn_unused]]
#else
#define ABSL_ATTRIBUTE_WARN_UNUSED
#endif

// ABSL_UNSAFE_BUFFERS()
//
// Wraps code that performs unsafe buffer accesses or pointer arithmetic. Used
// to suppress warnings when `-Wunsafe-buffer-usage` is enabled.
//
// **WARNING**: This macro should be used when unavoidable. Applying it means
// the compiler is unable to prove that your code avoids out-of-bounds reads or
// writes, forcing reliance on manual review. Over time, code evolves and
// undocumented assumptions can silently break, introducing vulnerabilities.
// Always prioritize refactoring to safer alternatives (e.g. std::array,
// absl::Span, or bounds-checked containers) over using this suppression.
//
// When using this macro is unavoidable, restrict its scope to the smallest
// possible expression or statement. You must also add a `// SAFETY: ...`
// comment explaining why the operation is actually safe.
// Justifications include:
//  * Explicit bounds checks (e.g., `CHECK()`) immediately preceding the access.
//  * Invariants strictly enforced by surrounding types or functions.
//  * Preconditions required of the caller (though this is heavily discouraged).
//
// Example (expression):
//
//   // SAFETY: `buf` is NUL-terminated so `strdup` won't read past the end.
//   return ABSL_UNSAFE_BUFFERS(strdup(buf));
//
// Example (single-line statement):
//
//   // SAFETY: `offset` is bounds-checked above to be within `buffer`.
//   ABSL_UNSAFE_BUFFERS(buffer += offset;)
//
// Example (multi-line statement):
//
//   // SAFETY: `offset` is bounds-checked above to be within `buffer`.
//   ABSL_UNSAFE_BUFFERS(
//       char* p = buffer + offset;
//       p[0] = 'a';
//   )
//
// Note: When wrapping a multi-line statement, placing a semicolon after the
// closing parenthesis may produce an extra semicolon warning.
#if defined(__clang__)
#define ABSL_UNSAFE_BUFFERS(...)             \
  _Pragma("clang unsafe_buffer_usage begin") \
      __VA_ARGS__ _Pragma("clang unsafe_buffer_usage end")
#else
#define ABSL_UNSAFE_BUFFERS(...) __VA_ARGS__
#endif

#endif  // ABSL_BASE_ATTRIBUTES_H_