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Diffstat (limited to 'third_party/abseil_cpp/absl/base/attributes.h')
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1 files changed, 683 insertions, 0 deletions
diff --git a/third_party/abseil_cpp/absl/base/attributes.h b/third_party/abseil_cpp/absl/base/attributes.h new file mode 100644 index 000000000000..f1d3cfe4d188 --- /dev/null +++ b/third_party/abseil_cpp/absl/base/attributes.h @@ -0,0 +1,683 @@ +// 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. +// +// This file is used for both C and C++! +// +// 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). + +#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_ATTRIBUTE(format) || (defined(__GNUC__) && !defined(__clang__)) +#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. +#if ABSL_HAVE_ATTRIBUTE(always_inline) || \ + (defined(__GNUC__) && !defined(__clang__)) +#define ABSL_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline)) +#define ABSL_HAVE_ATTRIBUTE_ALWAYS_INLINE 1 +#else +#define ABSL_ATTRIBUTE_ALWAYS_INLINE +#endif + +#if ABSL_HAVE_ATTRIBUTE(noinline) || (defined(__GNUC__) && !defined(__clang__)) +#define ABSL_ATTRIBUTE_NOINLINE __attribute__((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__) +#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_ATTRIBUTE_WEAK +// +// Tags a function as weak for the purposes of compilation and linking. +// Weak attributes currently do not work properly in LLVM's Windows backend, +// so disable them there. See https://bugs.llvm.org/show_bug.cgi?id=37598 +// for further information. +// 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(__GNUC__) && !defined(__clang__))) && \ + !(defined(__llvm__) && defined(_WIN32)) && !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) || (defined(__GNUC__) && !defined(__clang__)) +#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. +#if ABSL_HAVE_ATTRIBUTE(noreturn) || (defined(__GNUC__) && !defined(__clang__)) +#define ABSL_ATTRIBUTE_NORETURN __attribute__((noreturn)) +#elif defined(_MSC_VER) +#define ABSL_ATTRIBUTE_NORETURN __declspec(noreturn) +#else +#define ABSL_ATTRIBUTE_NORETURN +#endif + +// 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 ABSL_HAVE_ATTRIBUTE(no_sanitize_address) +#define ABSL_ATTRIBUTE_NO_SANITIZE_ADDRESS __attribute__((no_sanitize_address)) +#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_ATTRIBUTE(no_sanitize) +#define ABSL_ATTRIBUTE_NO_SANITIZE_CFI __attribute__((no_sanitize("cfi"))) +#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_ATTRIBUTE(returns_nonnull) || \ + (defined(__GNUC__) && \ + (__GNUC__ > 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)) && \ + !defined(__clang__)) +#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(__GNUC__) && !defined(__clang__))) && \ + !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 +#define ABSL_ATTRIBUTE_SECTION_VARIABLE(name) __attribute__((section(#name))) +#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) || \ + (defined(__GNUC__) && !defined(__clang__)) +#if defined(__i386__) +#define ABSL_ATTRIBUTE_STACK_ALIGN_FOR_OLD_LIBC \ + __attribute__((force_align_arg_pointer)) +#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. +// +// 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. +// +// ABSL_MUST_USE_RESULT allows using cast-to-void to suppress the unused result +// warning. For that, warn_unused_result is used only for clang but not for gcc. +// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66425 +// +// Note: past advice was to place the macro after the argument list. +#if ABSL_HAVE_ATTRIBUTE(nodiscard) +#define ABSL_MUST_USE_RESULT [[nodiscard]] +#elif defined(__clang__) && ABSL_HAVE_ATTRIBUTE(warn_unused_result) +#define ABSL_MUST_USE_RESULT __attribute__((warn_unused_result)) +#else +#define ABSL_MUST_USE_RESULT +#endif + +// 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 ABSL_HAVE_ATTRIBUTE(hot) || (defined(__GNUC__) && !defined(__clang__)) +#define ABSL_ATTRIBUTE_HOT __attribute__((hot)) +#else +#define ABSL_ATTRIBUTE_HOT +#endif + +#if ABSL_HAVE_ATTRIBUTE(cold) || (defined(__GNUC__) && !defined(__clang__)) +#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 in at least C++11 mode, 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_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. +#if ABSL_HAVE_ATTRIBUTE(unused) || (defined(__GNUC__) && !defined(__clang__)) +#undef ABSL_ATTRIBUTE_UNUSED +#define ABSL_ATTRIBUTE_UNUSED __attribute__((__unused__)) +#else +#define ABSL_ATTRIBUTE_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_ATTRIBUTE(tls_model) || (defined(__GNUC__) && !defined(__clang__)) +#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. 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) || (defined(__GNUC__) && !defined(__clang__)) +#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_ATTRIBUTE(aligned) || (defined(__GNUC__) && !defined(__clang__)) +#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. The ABSL_FALLTHROUGH_INTENDED macro should be followed by +// a semicolon and can be used in most places where `break` can, provided that +// no statements exist between it and the next switch label. +// +// Example: +// +// switch (x) { +// case 40: +// case 41: +// if (truth_is_out_there) { +// ++x; +// ABSL_FALLTHROUGH_INTENDED; // Use instead of/along with annotations +// // in comments +// } else { +// return x; +// } +// case 42: +// ... +// +// Notes: when compiled with clang in C++11 mode, the ABSL_FALLTHROUGH_INTENDED +// macro is expanded to the [[clang::fallthrough]] attribute, which is analysed +// when performing switch labels fall-through diagnostic +// (`-Wimplicit-fallthrough`). See clang documentation on language extensions +// for details: +// https://clang.llvm.org/docs/AttributeReference.html#fallthrough-clang-fallthrough +// +// When used with unsupported compilers, the ABSL_FALLTHROUGH_INTENDED macro +// has no effect on diagnostics. In any case 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 + +// TODO(zhangxy): Use c++17 standard [[fallthrough]] macro, when supported. +#if defined(__clang__) && defined(__has_warning) +#if __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough") +#define ABSL_FALLTHROUGH_INTENDED [[clang::fallthrough]] +#endif +#elif defined(__GNUC__) && __GNUC__ >= 7 +#define ABSL_FALLTHROUGH_INTENDED [[gnu::fallthrough]] +#endif + +#ifndef ABSL_FALLTHROUGH_INTENDED +#define ABSL_FALLTHROUGH_INTENDED \ + do { \ + } while (0) +#endif + +// 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). +// +// 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(); +// +// Every usage of a deprecated entity will trigger a warning when compiled with +// clang's `-Wdeprecated-declarations` option. This option is turned off by +// default, but the warnings will be reported by clang-tidy. +#if defined(__clang__) && __cplusplus >= 201103L +#define ABSL_DEPRECATED(message) __attribute__((deprecated(message))) +#endif + +#ifndef ABSL_DEPRECATED +#define ABSL_DEPRECATED(message) +#endif + +// ABSL_CONST_INIT +// +// A variable declaration annotated with the `ABSL_CONST_INIT` attribute 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". Prefer to put this attribute on the most visible +// declaration of the variable, if there's more than one, because code that +// accesses the variable can then use the attribute for optimization. +// +// Example: +// +// class MyClass { +// public: +// ABSL_CONST_INIT static MyType my_var; +// }; +// +// MyType MyClass::my_var = MakeMyType(...); +// +// Note that this attribute is redundant if the variable is declared constexpr. +#if ABSL_HAVE_CPP_ATTRIBUTE(clang::require_constant_initialization) +#define ABSL_CONST_INIT [[clang::require_constant_initialization]] +#else +#define ABSL_CONST_INIT +#endif // ABSL_HAVE_CPP_ATTRIBUTE(clang::require_constant_initialization) + +#endif // ABSL_BASE_ATTRIBUTES_H_ |