llvm-project/clang/lib/Headers/__stddef_null.h
Ian Anderson 9a7a6dd3c3 [Modules] Make clang modules for the C standard library headers
Make top level modules for all the C standard library headers.

The `__stddef` implementation headers need header guards now that they're all modular. stdarg.h and stddef.h will be textual headers in the builtin modules, and so need to be repeatedly included in both the system and builtin module case. Define their header guards for consistency, but ignore them when building with modules.

`__stddef_null.h` needs to ignore its header guard when modules aren't being used to fulfill its redefinition obligation.
`__stddef_nullptr_t.h` needs to add a guard for C23 so that `_Builtin_stddef` can compile in C17 and earlier modes. `_Builtin_stddef.nullptr_t` can't require C23 because it also needs to be usable from C++.

Reviewed By: Bigcheese

Differential Revision: https://reviews.llvm.org/D159064
2023-10-03 12:41:11 -07:00

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C

/*===---- __stddef_null.h - Definition of NULL -----------------------------===
*
* 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
*
*===-----------------------------------------------------------------------===
*/
#if !defined(NULL) || !__has_feature(modules)
/* linux/stddef.h will define NULL to 0. glibc (and other) headers then define
* __need_NULL and rely on stddef.h to redefine NULL to the correct value again.
* Modules don't support redefining macros like that, but support that pattern
* in the non-modules case.
*/
#undef NULL
#ifdef __cplusplus
#if !defined(__MINGW32__) && !defined(_MSC_VER)
#define NULL __null
#else
#define NULL 0
#endif
#else
#define NULL ((void*)0)
#endif
#endif