标准库检测

C++ 20 开始终于有了 feature testing macro __has_cpp_attribute(), 见 https://en.cppreference.com/w/cpp/feature_test

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#ifdef __has_cpp_attribute                      // Check if __has_cpp_attribute is present
#  if __has_cpp_attribute(deprecated)           // Check for an attribute
#    define DEPRECATED(msg) [[deprecated(msg)]]
#  endif
#endif
#ifndef DEPRECATED
#    define DEPRECATED(msg)
#endif

Explicitly mark as weak symbol

__attribute__((weak))

Used to declare a weak symbol, which can be overriden by a strong symbol at link time.

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void my_function() __attribute__((weak));

Notnull tags

__attribute__((nonnull(arg_index)))

__attribute__((returns_nonnull))

They only can check at compile-time and will be UB of violoated at runtime.

and can use syntax __attribute__((nonnull(arg_index1, arg_index2))) for multiple args.

__attribute__((no_sanitize_address)) or in MSVC __declspec(no_sanitize_address) to ignore a given function on memory address issues

__attribute__((no_sanitize_memory)) supported by Clang only; and handles with uninitialized memory issues

__attribute__((no_sanitize_thread)) for tsan, and

__attribute__((no_sanitize("undefined"))) for ubsan

__attribute__((no_sanitize("cfi"))) for CFI(Control Flow Integrity)

https://clang.llvm.org/docs/ControlFlowIntegrity.html

__attribute__((no_sanitize("safe-stack"))) for safe stack

For safe-stack sanitizer https://clang.llvm.org/docs/SafeStack.html

constinit

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#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

Lifetime bound

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#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

https://clang.llvm.org/docs/AttributeReference.html#lifetimebound