llvm/clang/lib/Headers/__stddef_nullptr_t.h

/*===---- __stddef_nullptr_t.h - Definition of nullptr_t -------------------===
 *
 * 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
 *
 *===-----------------------------------------------------------------------===
 */

/*
 * When -fbuiltin-headers-in-system-modules is set this is a non-modular header
 * and needs to behave as if it was textual.
 */
#if !defined(_NULLPTR_T) ||                                                    \
    (__has_feature(modules) && !__building_module(_Builtin_stddef))
#define _NULLPTR_T

#ifdef __cplusplus
#if defined(_MSC_EXTENSIONS) && defined(_NATIVE_NULLPTR_SUPPORTED)
namespace std {
typedef decltype(nullptr) nullptr_t;
}
using ::std::nullptr_t;
#endif
#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L
typedef typeof(nullptr) nullptr_t;
#endif

#endif