The patch titled Subject: headers: add check for C standard version has been added to the -mm mm-hotfixes-unstable branch. Its filename is headers-add-check-for-c-standard-version.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days
------------------------------------------------------ From: Hanne-Lotta M��enp���� hannelotta@gmail.com Subject: headers: add check for C standard version Date: Sun, 26 Oct 2025 21:58:46 +0200
Compiling the kernel with GCC 15 results in errors, as with GCC 15 the default language version for C compilation has been changed from -std=gnu17 to -std=gnu23 - unless the language version has been changed using
KBUILD_CFLAGS += -std=gnu17
or earlier.
C23 includes new keywords 'bool', 'true' and 'false', which cause compilation errors in Linux headers:
./include/linux/types.h:30:33: error: `bool' cannot be defined via `typedef'
./include/linux/stddef.h:11:9: error: cannot use keyword `false' as enumeration constant
Add check for C Standard's version in the header files to be able to compile the kernel with C23.
Link: https://lkml.kernel.org/r/20251026195846.69740-1-hannelotta@gmail.com Signed-off-by: Hanne-Lotta M��enp���� hannelotta@gmail.com Cc: David Hunter david.hunter.linux@gmail.com Cc: "Gustavo A. R. Silva" gustavoars@kernel.org Cc: Kees Cook kees@kernel.org Cc: Arnd Bergmann arnd@arndb.de Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
include/linux/stddef.h | 2 ++ include/linux/types.h | 2 ++ 2 files changed, 4 insertions(+)
--- a/include/linux/stddef.h~headers-add-check-for-c-standard-version +++ a/include/linux/stddef.h @@ -7,10 +7,12 @@ #undef NULL #define NULL ((void *)0)
+#if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 202311L enum { false = 0, true = 1 }; +#endif
#undef offsetof #define offsetof(TYPE, MEMBER) __builtin_offsetof(TYPE, MEMBER) --- a/include/linux/types.h~headers-add-check-for-c-standard-version +++ a/include/linux/types.h @@ -32,7 +32,9 @@ typedef __kernel_timer_t timer_t; typedef __kernel_clockid_t clockid_t; typedef __kernel_mqd_t mqd_t;
+#if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 202311L typedef _Bool bool; +#endif
typedef __kernel_uid32_t uid_t; typedef __kernel_gid32_t gid_t; _
Patches currently in -mm which might be from hannelotta@gmail.com are
headers-add-check-for-c-standard-version.patch
On October 26, 2025 4:56:30 PM PDT, Andrew Morton akpm@linux-foundation.org wrote:
The patch titled Subject: headers: add check for C standard version has been added to the -mm mm-hotfixes-unstable branch. Its filename is headers-add-check-for-c-standard-version.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days
From: Hanne-Lotta M��enp���� hannelotta@gmail.com Subject: headers: add check for C standard version Date: Sun, 26 Oct 2025 21:58:46 +0200
Compiling the kernel with GCC 15 results in errors, as with GCC 15 the default language version for C compilation has been changed from -std=gnu17 to -std=gnu23 - unless the language version has been changed using
KBUILD_CFLAGS += -std=gnu17
or earlier.
C23 includes new keywords 'bool', 'true' and 'false', which cause compilation errors in Linux headers:
./include/linux/types.h:30:33: error: `bool' cannot be defined via `typedef'
./include/linux/stddef.h:11:9: error: cannot use keyword `false' as enumeration constant
Add check for C Standard's version in the header files to be able to compile the kernel with C23.
What? These are internal headers, not UAPI. We build Linux with -std=gnu11. Let's not add meaningless version checks.
-Kees
Link: https://lkml.kernel.org/r/20251026195846.69740-1-hannelotta@gmail.com Signed-off-by: Hanne-Lotta M��enp���� hannelotta@gmail.com Cc: David Hunter david.hunter.linux@gmail.com Cc: "Gustavo A. R. Silva" gustavoars@kernel.org Cc: Kees Cook kees@kernel.org Cc: Arnd Bergmann arnd@arndb.de Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org
include/linux/stddef.h | 2 ++ include/linux/types.h | 2 ++ 2 files changed, 4 insertions(+)
--- a/include/linux/stddef.h~headers-add-check-for-c-standard-version +++ a/include/linux/stddef.h @@ -7,10 +7,12 @@ #undef NULL #define NULL ((void *)0)
+#if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 202311L enum { false = 0, true = 1 }; +#endif
#undef offsetof #define offsetof(TYPE, MEMBER) __builtin_offsetof(TYPE, MEMBER) --- a/include/linux/types.h~headers-add-check-for-c-standard-version +++ a/include/linux/types.h @@ -32,7 +32,9 @@ typedef __kernel_timer_t timer_t; typedef __kernel_clockid_t clockid_t; typedef __kernel_mqd_t mqd_t;
+#if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 202311L typedef _Bool bool; +#endif
typedef __kernel_uid32_t uid_t; typedef __kernel_gid32_t gid_t; _
Patches currently in -mm which might be from hannelotta@gmail.com are
headers-add-check-for-c-standard-version.patch
On Mon, Oct 27, 2025, at 03:31, Kees Cook wrote:
On October 26, 2025 4:56:30 PM PDT, Andrew Morton akpm@linux-foundation.org wrote:
From: Hanne-Lotta M��enp���� hannelotta@gmail.com Subject: headers: add check for C standard version Date: Sun, 26 Oct 2025 21:58:46 +0200
Compiling the kernel with GCC 15 results in errors, as with GCC 15 the default language version for C compilation has been changed from -std=gnu17 to -std=gnu23 - unless the language version has been changed using
KBUILD_CFLAGS += -std=gnu17
or earlier.
C23 includes new keywords 'bool', 'true' and 'false', which cause compilation errors in Linux headers:
./include/linux/types.h:30:33: error: `bool' cannot be defined via `typedef'
./include/linux/stddef.h:11:9: error: cannot use keyword `false' as enumeration constant
Add check for C Standard's version in the header files to be able to compile the kernel with C23.
What? These are internal headers, not UAPI. We build Linux with -std=gnu11. Let's not add meaningless version checks.
I have a similar patch in my own testing tree but in the end decided not to send it because supporting std=gnu23 doesn't actually add any features we want.
The next time we raise the compiler version from gcc-8 to anything newer, we can change the version selection to use --std=gnu2x unconditionally.
Arnd
linux-stable-mirror@lists.linaro.org
-
Andrew Morton -
Arnd Bergmann -
Kees Cook