Abseil Common Libraries (C++) (grcp 依赖)
https://abseil.io/
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
623 lines
24 KiB
623 lines
24 KiB
// 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). |
|
// |
|
// ----------------------------------------------------------------------------- |
|
// Sanitizer Attributes |
|
// ----------------------------------------------------------------------------- |
|
// |
|
// Sanitizer-related attributes are not "defined" in this file (and indeed |
|
// are not defined as such in any file). To utilize the following |
|
// sanitizer-related attributes within your builds, define the following macros |
|
// within your build using a `-D` flag, along with the given value for |
|
// `-fsanitize`: |
|
// |
|
// * `ADDRESS_SANITIZER` + `-fsanitize=address` (Clang, GCC 4.8) |
|
// * `MEMORY_SANITIZER` + `-fsanitize=memory` (Clang-only) |
|
// * `THREAD_SANITIZER` + `-fsanitize=thread` (Clang, GCC 4.8+) |
|
// * `UNDEFINED_BEHAVIOR_SANITIZER` + `-fsanitize=undefined` (Clang, GCC 4.9+) |
|
// * `CONTROL_FLOW_INTEGRITY` + `-fsanitize=cfi` (Clang-only) |
|
// |
|
// Example: |
|
// |
|
// // Enable branches in the Abseil code that are tagged for ASan: |
|
// $ bazel build --copt=-DADDRESS_SANITIZER --copt=-fsanitize=address |
|
// --linkopt=-fsanitize=address *target* |
|
// |
|
// Since these macro names are only supported by GCC and Clang, we only check |
|
// for `__GNUC__` (GCC or Clang) and the above macros. |
|
#ifndef ABSL_BASE_ATTRIBUTES_H_ |
|
#define ABSL_BASE_ATTRIBUTES_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 defined(__GNUC__) |
|
#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 ADDRESS_SANITIZER attribute above, but deals |
|
// with initialized-ness rather than addressability issues. |
|
// NOTE: MemorySanitizer(msan) is supported by Clang but not GCC. |
|
#if defined(__clang__) |
|
#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 defined(__GNUC__) |
|
#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 defined(__GNUC__) && \ |
|
(defined(UNDEFINED_BEHAVIOR_SANITIZER) || defined(ADDRESS_SANITIZER)) |
|
#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 defined(__GNUC__) && defined(CONTROL_FLOW_INTEGRITY) |
|
#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 defined(__GNUC__) && defined(SAFESTACK_SANITIZER) |
|
#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_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_
|
|
|