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// Copyright © Tavian Barnes <tavianator@tavianator.com>
// SPDX-License-Identifier: 0BSD

/**
 * Configuration and feature/platform detection.
 */

#ifndef BFS_PRELUDE_H
#define BFS_PRELUDE_H

// Possible __STDC_VERSION__ values

#define C95 199409L
#define C99 199901L
#define C11 201112L
#define C17 201710L
#define C23 202311L

// Get the static_assert() definition as well as __GLIBC__
#include <assert.h>

// Get the convenience macros that became standard spellings in C23
#if __STDC_VERSION__ < C23

/** _Alignas(), _Alignof() => alignas(), alignof() */
#include <stdalign.h>
/** _Bool => bool, true, false */
#include <stdbool.h>

/**
 * C23 deprecates `noreturn void` in favour of `[[noreturn]] void`, so we expose
 * _noreturn instead with the other attributes.
 */
// #include <stdnoreturn.h>

/** Part of <threads.h>, but we don't use anything else from it. */
#define thread_local _Thread_local

#endif // !C23

// bfs packaging configuration

#include "config.h"

#ifndef BFS_COMMAND
#  define BFS_COMMAND "bfs"
#endif
#ifndef BFS_HOMEPAGE
#  define BFS_HOMEPAGE "https://tavianator.com/projects/bfs.html"
#endif

// This is a symbol instead of a literal so we don't have to rebuild everything
// when the version number changes
extern const char bfs_version[];

extern const char bfs_confflags[];
extern const char bfs_cc[];
extern const char bfs_cppflags[];
extern const char bfs_cflags[];
extern const char bfs_ldflags[];
extern const char bfs_ldlibs[];

// Feature detection

// https://clang.llvm.org/docs/LanguageExtensions.html#has-attribute
#ifndef __has_attribute
#  define __has_attribute(attr) false
#endif

// https://clang.llvm.org/docs/LanguageExtensions.html#has-builtin
#ifndef __has_builtin
#  define __has_builtin(builtin) false
#endif

// https://en.cppreference.com/w/c/language/attributes#Attribute_testing
#ifndef __has_c_attribute
#  define __has_c_attribute(attr) false
#endif

// https://clang.llvm.org/docs/LanguageExtensions.html#has-feature-and-has-extension
#ifndef __has_feature
#  define __has_feature(feat) false
#endif

// https://en.cppreference.com/w/c/preprocessor/include
#ifndef __has_include
#  define __has_include(header) false
#endif

// Sanitizer macros (GCC defines these but Clang does not)

#if __has_feature(address_sanitizer) && !defined(__SANITIZE_ADDRESS__)
#  define __SANITIZE_ADDRESS__ true
#endif
#if __has_feature(memory_sanitizer) && !defined(__SANITIZE_MEMORY__)
#  define __SANITIZE_MEMORY__ true
#endif
#if __has_feature(thread_sanitizer) && !defined(__SANITIZE_THREAD__)
#  define __SANITIZE_THREAD__ true
#endif

// Fundamental utilities

/**
 * Get the length of an array.
 */
#define countof(...) (sizeof(__VA_ARGS__) / sizeof(0[__VA_ARGS__]))

/**
 * False sharing/destructive interference/largest cache line size.
 */
#ifdef __GCC_DESTRUCTIVE_SIZE
#  define FALSE_SHARING_SIZE __GCC_DESTRUCTIVE_SIZE
#else
#  define FALSE_SHARING_SIZE 64
#endif

/**
 * True sharing/constructive interference/smallest cache line size.
 */
#ifdef __GCC_CONSTRUCTIVE_SIZE
#  define TRUE_SHARING_SIZE __GCC_CONSTRUCTIVE_SIZE
#else
#  define TRUE_SHARING_SIZE 64
#endif

/**
 * Alignment specifier that avoids false sharing.
 */
#define cache_align alignas(FALSE_SHARING_SIZE)

// Wrappers for attributes

/**
 * Silence warnings about switch/case fall-throughs.
 */
#if __has_attribute(fallthrough)
#  define _fallthrough __attribute__((fallthrough))
#else
#  define _fallthrough ((void)0)
#endif

/**
 * Silence warnings about unused declarations.
 */
#if __has_attribute(unused)
#  define _maybe_unused __attribute__((unused))
#else
#  define _maybe_unused
#endif

/**
 * Warn if a value is unused.
 */
#if __has_attribute(warn_unused_result)
#  define _nodiscard __attribute__((warn_unused_result))
#else
#  define _nodiscard
#endif

/**
 * Hint to avoid inlining a function.
 */
#if __has_attribute(noinline)
#  define _noinline __attribute__((noinline))
#else
#  define _noinline
#endif

/**
 * Marks a non-returning function.
 */
#if __STDC_VERSION__ >= C23
#  define _noreturn [[noreturn]]
#else
#  define _noreturn _Noreturn
#endif

/**
 * Hint that a function is unlikely to be called.
 */
#if __has_attribute(cold)
#  define _cold _noinline __attribute__((cold))
#else
#  define _cold _noinline
#endif

/**
 * Adds compiler warnings for bad printf()-style function calls, if supported.
 */
#if __has_attribute(format)
#  define _printf(fmt, args) __attribute__((format(printf, fmt, args)))
#else
#  define _printf(fmt, args)
#endif

/**
 * Annotates functions that potentially modify and return format strings.
 */
#if __has_attribute(format_arg)
#  define _format_arg(arg) __attribute__((format_arg(arg)))
#else
#  define _format_arg(arg)
#endif

/**
 * Annotates allocator-like functions.
 */
#if __has_attribute(malloc)
#  if __GNUC__ >= 11 && !__OPTIMIZE__ // malloc(deallocator) disables inlining on GCC
#    define _malloc(...) _nodiscard __attribute__((malloc(__VA_ARGS__)))
#  else
#    define _malloc(...) _nodiscard __attribute__((malloc))
#  endif
#else
#  define _malloc(...) _nodiscard
#endif

/**
 * Specifies that a function returns allocations with a given alignment.
 */
#if __has_attribute(alloc_align)
#  define _alloc_align(param) __attribute__((alloc_align(param)))
#else
#  define _alloc_align(param)
#endif

/**
 * Specifies that a function returns allocations with a given size.
 */
#if __has_attribute(alloc_size)
#  define _alloc_size(...) __attribute__((alloc_size(__VA_ARGS__)))
#else
#  define _alloc_size(...)
#endif

/**
 * Shorthand for _alloc_align() and _alloc_size().
 */
#define _aligned_alloc(align, ...) _alloc_align(align) _alloc_size(__VA_ARGS__)

/**
 * Check if function multiversioning via GNU indirect functions (ifunc) is supported.
 *
 * Disabled on TSan due to https://github.com/google/sanitizers/issues/342.
 */
#ifndef BFS_USE_TARGET_CLONES
#  if __has_attribute(target_clones) && (__GLIBC__ || __FreeBSD__) && !__SANITIZE_THREAD__
#    define BFS_USE_TARGET_CLONES true
#  endif
#endif

/**
 * Apply the target_clones attribute, if available.
 */
#if BFS_USE_TARGET_CLONES
#  define _target_clones(...) __attribute__((target_clones(__VA_ARGS__)))
#else
#  define _target_clones(...)
#endif

#endif // BFS_PRELUDE_H