| // 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). |
| |
| #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__) && !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_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. |
| // 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(_WIN32) || (defined(__clang__) && __clang_major__ >= 9)) && \ |
| !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(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_ATTRIBUTE(no_sanitize) && defined(__llvm__) |
| #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) |
| #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 |
| #ifdef _AIX |
| // __attribute__((section(#name))) on AIX is achieved by using the `.csect` |
| // psudo op which includes an additional integer as part of its syntax indcating |
| // 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) |
| #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) || \ |
| (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. |
| // |
| // For code or headers that are assured to only build with C++17 and up, prefer |
| // just using the standard `[[nodiscard]]` directly over this macro. |
| // |
| // 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. |
| // |
| // TODO(b/176172494): Use ABSL_HAVE_CPP_ATTRIBUTE(nodiscard) when all code is |
| // compliant with the stricter [[nodiscard]]. |
| #if 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. |
| // |
| // For code or headers that are assured to only build with C++17 and up, prefer |
| // just using the standard '[[maybe_unused]]' directly over this macro. |
| // |
| // 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]]'. |
| #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. |
| // |
| // Therefore, 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) || (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 supported, GCC and Clang can issue a warning on switch labels |
| // with unannotated fallthrough using the warning `-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." |
| #elif ABSL_HAVE_CPP_ATTRIBUTE(fallthrough) |
| #define ABSL_FALLTHROUGH_INTENDED [[fallthrough]] |
| #elif ABSL_HAVE_CPP_ATTRIBUTE(clang::fallthrough) |
| #define ABSL_FALLTHROUGH_INTENDED [[clang::fallthrough]] |
| #elif ABSL_HAVE_CPP_ATTRIBUTE(gnu::fallthrough) |
| #define ABSL_FALLTHROUGH_INTENDED [[gnu::fallthrough]] |
| #else |
| #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). |
| // |
| // For code or headers that are assured to only build with C++14 and up, prefer |
| // just using the standard `[[deprecated("message")]]` directly over this macro. |
| // |
| // 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. |
| #if ABSL_HAVE_ATTRIBUTE(deprecated) |
| #define ABSL_DEPRECATED(message) __attribute__((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 ABSL_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") |
| #else |
| #define ABSL_INTERNAL_DISABLE_DEPRECATED_DECLARATION_WARNING |
| #define ABSL_INTERNAL_RESTORE_DEPRECATED_DECLARATION_WARNING |
| #endif // defined(__GNUC__) || defined(__clang__) |
| |
| // 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". |
| // |
| // This attribute must be placed on the initializing declaration of the |
| // variable. Some compilers will give a -Wmissing-constinit warning when this |
| // attribute is placed on some other declaration but missing from the |
| // initializing declaration. |
| // |
| // In some cases (notably with thread_local variables), `ABSL_CONST_INIT` can |
| // also be used in a non-initializing declaration to tell the compiler that a |
| // variable is already initialized, reducing overhead that would otherwise be |
| // incurred by a hidden guard variable. Thus annotating all declarations with |
| // this attribute is recommended to potentially enhance optimization. |
| // |
| // 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 |
| // just using the standard `constinit` keyword directly over this macro. |
| // |
| // Note that this attribute is redundant if the variable is declared constexpr. |
| #if defined(__cpp_constinit) && __cpp_constinit >= 201907L |
| #define ABSL_CONST_INIT constinit |
| #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 |
| #if ABSL_HAVE_CPP_ATTRIBUTE(clang::lifetimebound) |
| #define ABSL_ATTRIBUTE_LIFETIME_BOUND [[clang::lifetimebound]] |
| #elif ABSL_HAVE_ATTRIBUTE(lifetimebound) |
| #define ABSL_ATTRIBUTE_LIFETIME_BOUND __attribute__((lifetimebound)) |
| #else |
| #define ABSL_ATTRIBUTE_LIFETIME_BOUND |
| #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 |
| |
| #endif // ABSL_BASE_ATTRIBUTES_H_ |