https://github.com/AaronBallman created https://github.com/llvm/llvm-project/pull/140890
WG14 N3469 changed _Lengthof to _Countof but it also introduced the <stdcountof.h> header to expose a macro with a non-ugly identifier. GCC vends this header as part of the compiler implementation, so Clang should do the same. >From 10cb78bd9f361dd442c40702dad3c7809f466615 Mon Sep 17 00:00:00 2001 From: Aaron Ballman <aa...@aaronballman.com> Date: Wed, 21 May 2025 08:59:47 -0400 Subject: [PATCH] [C2y] Add stdcountof.h WG14 N3469 changed _Lengthof to _Countof but it also introduced the <stdcountof.h> header to expose a macro with a non-ugly identifier. GCC vends this header as part of the compiler implementation, so Clang should do the same. --- clang/docs/ReleaseNotes.rst | 4 +++- clang/lib/Headers/stdcountof.h | 15 +++++++++++++++ clang/test/C/C2y/n3469.c | 13 +++++++++++-- 3 files changed, 29 insertions(+), 3 deletions(-) create mode 100644 clang/lib/Headers/stdcountof.h diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index b466f3758e0b6..7b2777f711b8d 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -249,7 +249,9 @@ C2y Feature Support a conforming extension in earlier C language modes, but not in C++ language modes (``std::extent`` and ``std::size`` already provide the same functionality but with more granularity). The feature can be tested via - ``__has_feature(c_countof)`` or ``__has_extension(c_countof)``. + ``__has_feature(c_countof)`` or ``__has_extension(c_countof)``. This also + adds the ``<stdcountof.h>`` header file which exposes the ``countof`` macro + which expands to ``_Countof``. C23 Feature Support ^^^^^^^^^^^^^^^^^^^ diff --git a/clang/lib/Headers/stdcountof.h b/clang/lib/Headers/stdcountof.h new file mode 100644 index 0000000000000..5714e6d6ff860 --- /dev/null +++ b/clang/lib/Headers/stdcountof.h @@ -0,0 +1,15 @@ +/*===---- stdcountof.h - Standard header for countof -----------------------=== + * + * 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 + * + *===-----------------------------------------------------------------------=== + */ + +#ifndef __STDCOUNTOF_H +#define __STDCOUNTOF_H + +#define countof _Countof + +#endif /* __STDCOUNTOF_H */ diff --git a/clang/test/C/C2y/n3469.c b/clang/test/C/C2y/n3469.c index 3d9ac8e6411e9..4660596614075 100644 --- a/clang/test/C/C2y/n3469.c +++ b/clang/test/C/C2y/n3469.c @@ -1,9 +1,9 @@ -// RUN: %clang_cc1 -fsyntax-only -std=c2y -verify %s +// RUN: %clang_cc1 -fsyntax-only -std=c2y -verify -ffreestanding %s /* WG14 N3469: Clang 21 * The Big Array Size Survey * - * This renames _Lengthof to _Countof. + * This renames _Lengthof to _Countof and introduces the stdcountof.h header. */ void test() { @@ -12,3 +12,12 @@ void test() { expected-error {{expected expression}} } +#ifdef countof +#error "why is countof defined as a macro?" +#endif + +#include <stdcountof.h> + +#ifndef countof +#error "why is countof not defined as a macro?" +#endif _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
