libc/src/__support/macros/attributes.h

//===-- Portable attributes -------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// This header file defines macros for declaring attributes for functions,
// types, and variables.
//
// These macros are used within llvm-libc 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.

#ifndef LLVM_LIBC_SRC___SUPPORT_MACROS_ATTRIBUTES_H
#define LLVM_LIBC_SRC___SUPPORT_MACROS_ATTRIBUTES_H

#include "config.h"
#include "properties/architectures.h"

#ifndef __has_attribute
#define __has_attribute(x) 0
#endif

#define LIBC_INLINE inline
#define LIBC_INLINE_VAR inline
#define LIBC_INLINE_ASM __asm__ __volatile__
#define LIBC_UNUSED __attribute__((unused))

#ifndef LIBC_HAS_BUILTIN_IS_CONSTANT_EVALUATED
#define LIBC_HAS_BUILTIN_IS_CONSTANT_EVALUATED                                 \
  (__has_builtin(__builtin_is_constant_evaluated))
#endif // LIBC_HAS_BUILTIN_IS_CONSTANT_EVALUATED

// TODO: Remove the macro once Clang/LLVM bump their minimum compilers' version.
// The reason for indirection is GCC is known to fail with constexpr qualified
// functions that doesn't produce constant expression. This avoids it by using
// LIBC_ENABLE_CONSTEXPR as a flag to control whether the function should be
// constexpr qualified or not.
#if LIBC_ENABLE_CONSTEXPR &&                                                   \
    (LIBC_HAS_BUILTIN_IS_CONSTANT_EVALUATED ||                                 \
     (defined(LIBC_COMPILER_IS_GCC) && (LIBC_COMPILER_GCC_VER >= 900)) ||      \
     (defined(LIBC_COMPILER_IS_CLANG) && LIBC_COMPILER_CLANG_VER >= 1100))
#define LIBC_HAS_CONSTANT_EVALUATION
#define LIBC_CONSTEXPR constexpr
#else
#define LIBC_CONSTEXPR
#endif

// Uses the platform specific specialization
#define LIBC_THREAD_MODE_PLATFORM 0

// Mutex guards nothing, used in single-threaded implementations
#define LIBC_THREAD_MODE_SINGLE 1

// Vendor provides implementation
#define LIBC_THREAD_MODE_EXTERNAL 2

// libcxx doesn't define LIBC_THREAD_MODE, unless that is passed in the command
// line in the CMake invocation. This defaults to the original implementation
// (before changes in https://github.com/llvm/llvm-project/pull/145358)
#ifndef LIBC_THREAD_MODE
#define LIBC_THREAD_MODE LIBC_THREAD_MODE_PLATFORM
#endif // LIBC_THREAD_MODE

#if LIBC_THREAD_MODE != LIBC_THREAD_MODE_PLATFORM &&                           \
    LIBC_THREAD_MODE != LIBC_THREAD_MODE_SINGLE &&                             \
    LIBC_THREAD_MODE != LIBC_THREAD_MODE_EXTERNAL
#error LIBC_THREAD_MODE must be one of the following values: \
LIBC_THREAD_MODE_PLATFORM, \
LIBC_THREAD_MODE_SINGLE, \
LIBC_THREAD_MODE_EXTERNAL.
#endif

#if LIBC_THREAD_MODE == LIBC_THREAD_MODE_SINGLE
#define LIBC_THREAD_LOCAL
#else
#define LIBC_THREAD_LOCAL thread_local
#endif

#if __cplusplus >= 202002L
#define LIBC_CONSTINIT constinit
#elif __has_attribute(__require_constant_initialization__)
#define LIBC_CONSTINIT __attribute__((__require_constant_initialization__))
#else
#define LIBC_CONSTINIT
#endif

#if defined(__clang__) && __has_attribute(preferred_type)
#define LIBC_PREFERED_TYPE(TYPE) [[clang::preferred_type(TYPE)]]
#else
#define LIBC_PREFERED_TYPE(TYPE)
#endif

#if __has_attribute(ext_vector_type) &&                                        \
    LIBC_HAS_FEATURE(ext_vector_type_boolean)
#define LIBC_HAS_VECTOR_TYPE 1
#else
#define LIBC_HAS_VECTOR_TYPE 0
#endif

#if __has_attribute(no_sanitize)
// Disable regular and hardware-supported ASan for functions that may
// intentionally make out-of-bounds access. Disable TSan as well, as it detects
// out-of-bounds accesses to heap memory.
#define LIBC_NO_SANITIZE_OOB_ACCESS                                            \
  __attribute__((no_sanitize("address", "hwaddress", "thread")))
#else
#define LIBC_NO_SANITIZE_OOB_ACCESS
#endif

#endif // LLVM_LIBC_SRC___SUPPORT_MACROS_ATTRIBUTES_H