[clang] [C2y] Add stdcountof.h (PR #140890)
Aaron Ballman via cfe-commits
cfe-commits at lists.llvm.org
Thu May 22 05:41:15 PDT 2025
https://github.com/AaronBallman updated https://github.com/llvm/llvm-project/pull/140890
>From 10cb78bd9f361dd442c40702dad3c7809f466615 Mon Sep 17 00:00:00 2001
From: Aaron Ballman <aaron at aaronballman.com>
Date: Wed, 21 May 2025 08:59:47 -0400
Subject: [PATCH 1/3] [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
>From 7d94ea7a3d0b663ffca61f89bca2ca56ef585f7d Mon Sep 17 00:00:00 2001
From: Aaron Ballman <aaron at aaronballman.com>
Date: Wed, 21 May 2025 09:33:56 -0400
Subject: [PATCH 2/3] Update other places where the builtin header needs to be
mentioned
---
clang/lib/Headers/CMakeLists.txt | 1 +
clang/lib/Headers/module.modulemap | 5 +++++
clang/lib/Lex/ModuleMap.cpp | 1 +
clang/lib/Lex/PPDirectives.cpp | 4 ++--
clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc | 1 +
.../Modules/Inputs/builtin-headers/system-modules.modulemap | 5 +++++
6 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/clang/lib/Headers/CMakeLists.txt b/clang/lib/Headers/CMakeLists.txt
index 449feb012481f..013bd13d1d276 100644
--- a/clang/lib/Headers/CMakeLists.txt
+++ b/clang/lib/Headers/CMakeLists.txt
@@ -18,6 +18,7 @@ set(core_files
__stdarg_va_list.h
stdatomic.h
stdbool.h
+ stdcountof.h
stdckdint.h
stddef.h
__stddef_header_macro.h
diff --git a/clang/lib/Headers/module.modulemap b/clang/lib/Headers/module.modulemap
index dcaf09e8f2c55..35897a3ed0e79 100644
--- a/clang/lib/Headers/module.modulemap
+++ b/clang/lib/Headers/module.modulemap
@@ -231,6 +231,11 @@ module _Builtin_stdbool [system] {
export *
}
+module _Builtin_stdcountof [system] {
+ header "stdcountof.h"
+ export *
+}
+
module _Builtin_stddef [system] {
textual header "stddef.h"
diff --git a/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
index 4175959d8f55b..be9cab8afb9b3 100644
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -260,6 +260,7 @@ static bool isBuiltinHeaderName(StringRef FileName) {
.Case("stdarg.h", true)
.Case("stdatomic.h", true)
.Case("stdbool.h", true)
+ .Case("stdcountof.h", true)
.Case("stddef.h", true)
.Case("stdint.h", true)
.Case("tgmath.h", true)
diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index b2a8459d6b9cc..68f9ca9cb4d40 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -252,8 +252,8 @@ static bool warnByDefaultOnWrongCase(StringRef Include) {
.Cases("assert.h", "complex.h", "ctype.h", "errno.h", "fenv.h", true)
.Cases("float.h", "inttypes.h", "iso646.h", "limits.h", "locale.h", true)
.Cases("math.h", "setjmp.h", "signal.h", "stdalign.h", "stdarg.h", true)
- .Cases("stdatomic.h", "stdbool.h", "stdckdint.h", "stddef.h", true)
- .Cases("stdint.h", "stdio.h", "stdlib.h", "stdnoreturn.h", true)
+ .Cases("stdatomic.h", "stdbool.h", "stdckdint.h", "stdcountof.h", true)
+ .Cases("stddef.h", "stdint.h", "stdio.h", "stdlib.h", "stdnoreturn.h", true)
.Cases("string.h", "tgmath.h", "threads.h", "time.h", "uchar.h", true)
.Cases("wchar.h", "wctype.h", true)
diff --git a/clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc b/clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc
index 463ce921f0672..cc54bc9446a01 100644
--- a/clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc
+++ b/clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc
@@ -389,6 +389,7 @@ SYMBOL(cosh, None, <math.h>)
SYMBOL(coshf, None, <math.h>)
SYMBOL(coshl, None, <math.h>)
SYMBOL(cosl, None, <math.h>)
+SYMBOL(countof, None, <stdcountof.h>)
SYMBOL(cpow, None, <complex.h>)
SYMBOL(cpowf, None, <complex.h>)
SYMBOL(cpowl, None, <complex.h>)
diff --git a/clang/test/Modules/Inputs/builtin-headers/system-modules.modulemap b/clang/test/Modules/Inputs/builtin-headers/system-modules.modulemap
index 0161ff80fe618..186965177caaf 100644
--- a/clang/test/Modules/Inputs/builtin-headers/system-modules.modulemap
+++ b/clang/test/Modules/Inputs/builtin-headers/system-modules.modulemap
@@ -49,6 +49,11 @@ module cstd [system] [no_undeclared_includes] {
export *
}
+ module stdcountof {
+ header "stdcountof.h"
+ export *
+ }
+
module stddef {
header "stddef.h"
export *
>From 3f36d58552b6c67867b0730391b00ad43da5e56c Mon Sep 17 00:00:00 2001
From: Aaron Ballman <aaron at aaronballman.com>
Date: Thu, 22 May 2025 08:40:50 -0400
Subject: [PATCH 3/3] Actually test the module header
---
clang/test/Modules/builtin-headers.mm | 1 +
1 file changed, 1 insertion(+)
diff --git a/clang/test/Modules/builtin-headers.mm b/clang/test/Modules/builtin-headers.mm
index 4c9ddec4e99c2..ad2d66ae38dfd 100644
--- a/clang/test/Modules/builtin-headers.mm
+++ b/clang/test/Modules/builtin-headers.mm
@@ -17,6 +17,7 @@
@import _Builtin_stdarg;
@import _Builtin_stdatomic;
@import _Builtin_stdbool;
+ at import _Builtin_stdcountof;
@import _Builtin_stddef;
@import _Builtin_stdint;
@import _Builtin_stdnoreturn;
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