compat_c23.h

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#pragma once
#include <stdbool.h>  // For bool, true, false
#include <stddef.h>   // For offsetof, size_t
 
#ifndef nullptr
#define nullptr ((void *)0)
#endif
 
#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L) || (defined(_MSC_VER) && _MSC_VER >= 1900)
// On modern compilers, <assert.h> may also define `static_assert` as a macro.
// We include it here to ensure the system's definition is seen first, which
// allows our `#ifndef` guard to correctly prevent a redefinition warning.
#include <assert.h>
#ifndef static_assert
#define static_assert(cond, msg) _Static_assert(cond, msg)
#endif
#endif
 
// (Internal) Helper to check for native C23-style attributes [[...]]
#if defined(__has_c_attribute)
#define COMPAT_HAS_C_ATTRIBUTE(x) __has_c_attribute(x)
#else
#define COMPAT_HAS_C_ATTRIBUTE(x) 0
#endif
 
#if COMPAT_HAS_C_ATTRIBUTE(nodiscard)
#define c23_nodiscard [[nodiscard]]
#elif defined(__GNUC__) || defined(__clang__)
#define c23_nodiscard __attribute__((warn_unused_result))
#elif defined(_MSC_VER)
#define c23_nodiscard _Check_return_
#else
#define c23_nodiscard
#endif
 
#if COMPAT_HAS_C_ATTRIBUTE(deprecated)
#define c23_deprecated [[deprecated]]
#elif defined(__GNUC__) || defined(__clang__)
#define c23_deprecated __attribute__((deprecated))
#elif defined(_MSC_VER)
#define c23_deprecated __declspec(deprecated)
#else
#define c23_deprecated
#endif
 
#if COMPAT_HAS_C_ATTRIBUTE(fallthrough)
#define c23_fallthrough [[fallthrough]]
#elif defined(__GNUC__) || defined(__clang__)
#define c23_fallthrough __attribute__((fallthrough))
#else
#define c23_fallthrough /* fallthrough */
#endif
 
#if COMPAT_HAS_C_ATTRIBUTE(maybe_unused)
#define c23_maybe_unused [[maybe_unused]]
#elif defined(__GNUC__) || defined(__clang__)
#define c23_maybe_unused __attribute__((unused))
#else
#define c23_maybe_unused
#endif