From: Paul Eggert <eggert@cs.ucla.edu>
Date: Thu, 30 Apr 2026 00:10:56 +0000 (-0700)
Subject: stdbit-h: namespace cleanup port to G++ 15
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;ds=inline;p=thirdparty%2Fgnulib.git

stdbit-h: namespace cleanup port to G++ 15

For the namespace cleanup, don’t assume that the system <stdbit.h>
defines size_t etc. unless it also defines
__STDC_VERSION_STDBIT_H__.  This works around problems with C++
compilers where ‘#include <stdbit.h>’ is a no-op, such as g++ 15.2.1.
Problem reported by Bruno Haible in:
https://lists.gnu.org/r/bug-gnulib/2026-04/msg00203.html
It also lets us simplify the code by removing a special case for
the Intel icpx C++ compiler.
* lib/stdbit.in.h: When deciding whether <stdbit.h> works,
use (defined __STDC_VERSION_STDBIT_H__) rather than @HAVE_STDBIT_H@.
This fixes problems when <stdbit.h> works for C so @HAVE_STDBIT_H@
is 1, whereas <stdbit.h> does nothing for C++.
(__STDC_VERSION_STDBIT_H__): Move definition to end.
---

diff --git a/ChangeLog b/ChangeLog
index 86585c6ff6..98aff8ecd2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,20 @@
 2026-04-29  Paul Eggert  <eggert@cs.ucla.edu>
 
+	stdbit-h: namespace cleanup port to G++ 15
+	For the namespace cleanup, don’t assume that the system <stdbit.h>
+	defines size_t etc. unless it also defines
+	__STDC_VERSION_STDBIT_H__.  This works around problems with C++
+	compilers where ‘#include <stdbit.h>’ is a no-op, such as g++ 15.2.1.
+	Problem reported by Bruno Haible in:
+	https://lists.gnu.org/r/bug-gnulib/2026-04/msg00203.html
+	It also lets us simplify the code by removing a special case for
+	the Intel icpx C++ compiler.
+	* lib/stdbit.in.h: When deciding whether <stdbit.h> works,
+	use (defined __STDC_VERSION_STDBIT_H__) rather than @HAVE_STDBIT_H@.
+	This fixes problems when <stdbit.h> works for C so @HAVE_STDBIT_H@
+	is 1, whereas <stdbit.h> does nothing for C++.
+	(__STDC_VERSION_STDBIT_H__): Move definition to end.
+
 	stdbit-h: <stddef.h> namespace cleanup
 	* lib/stdbit.in.h: Include <stddef.h> only if the stdc_memreverse8
 	module is also used, since it’s the only one that needs size_t.
diff --git a/doc/posix-headers/stdbit.texi b/doc/posix-headers/stdbit.texi
index 87f91d0a54..b658447021 100644
--- a/doc/posix-headers/stdbit.texi
+++ b/doc/posix-headers/stdbit.texi
@@ -15,6 +15,9 @@ Portability problems fixed by Gnulib:
 This header file is missing on many non-C23 platforms:
 glibc 2.38, macOS 14, FreeBSD 14.0, NetBSD 10.0, OpenBSD 7.5, AIX 7.3.1, HP-UX 11.31, Solaris 11.4, Cygwin 3.5.3, mingw, MSVC 17, Android 15.
 @item
+This header file exists but is a no-op:
+G++ 15.2.
+@item
 This header file does not define the necessary types
 with the Intel @code{icpx} C++ compiler.
 @end itemize
diff --git a/lib/stdbit.in.h b/lib/stdbit.in.h
index 04a9dfd183..990f3edfde 100644
--- a/lib/stdbit.in.h
+++ b/lib/stdbit.in.h
@@ -38,9 +38,7 @@
 #endif
 
 /* If needed for APIs, get size_t, avoiding namespace pollution on GNU.  */
-#if (@GNULIB_STDC_MEMREVERSE8@ \
-     && (!@HAVE_STDBIT_H@ \
-         || (defined __cplusplus && defined __INTEL_CLANG_COMPILER)))
+#if @GNULIB_STDC_MEMREVERSE8@ && !defined __STDC_VERSION_STDBIT_H__
 # define __need_size_t
 # include <stddef.h>
 #endif
@@ -51,8 +49,7 @@
 #if (@GNULIB_STDC_MEMREVERSE8U@ \
      || @GNULIB_STDC_LOAD8@ || @GNULIB_STDC_LOAD8_ALIGNED@ \
      || @GNULIB_STDC_STORE8@ || @GNULIB_STDC_STORE8_ALIGNED@)
-# if (!(@HAVE_STDBIT_H@ && defined __UINT_FAST64_TYPE__) \
-      || (defined __cplusplus && defined __INTEL_CLANG_COMPILER))
+# if !(defined __STDC_VERSION_STDBIT_H__ && defined __UINT_FAST64_TYPE__)
 #  include <stdint.h>
 #  define _GL_STDBIT_UINT_FAST16 uint_fast16_t
 #  define _GL_STDBIT_UINT_FAST32 uint_fast32_t
@@ -196,12 +193,7 @@ extern "C" {
 
 
 /* Some systems are only missing C2y features in stdbit.h.  */
-#if !@HAVE_STDBIT_H@ || defined __cplusplus
-
-/* ISO C 23 § 7.18.1 General  */
-
-#define __STDC_VERSION_STDBIT_H__ 202311L
-
+#ifndef __STDC_VERSION_STDBIT_H__
 
 /* ISO C 23 § 7.18.2 Endian  */
 
@@ -217,7 +209,7 @@ extern "C" {
 
 
 /* Some systems are only missing C2y features in stdbit.h.  */
-#if !@HAVE_STDBIT_H@
+#ifndef __STDC_VERSION_STDBIT_H__
 
 /* ISO C 23 § 7.18.3 Count Leading Zeros  */
 
@@ -1263,7 +1255,7 @@ stdc_bit_ceil_ull (unsigned long long int n)
 
 #endif
 
-#endif /* @HAVE_STDBIT_H@ */
+#endif /* !__STDC_VERSION_STDBIT_H__ */
 
 
 /* ISO C2y § 7.18.17 Rotate Left  */
@@ -2212,5 +2204,10 @@ stdc_store8_aligned_les64 (int_least64_t value, unsigned char ptr[8])
 
 _GL_INLINE_HEADER_END
 
+/* ISO C 23 § 7.18.1 General  */
+#ifndef __STDC_VERSION_STDBIT_H__
+# define __STDC_VERSION_STDBIT_H__ 202311L
+#endif
+
 #endif /* _@GUARD_PREFIX@_STDBIT_H */
 #endif /* _@GUARD_PREFIX@_STDBIT_H */