From: Nathan Chancellor <nathan@xxxxxxxxxx>
commit ee2ab467bddfb2d7f68d996dbab94d7b88f8eaf7 upstream.
GCC 15 changed the default C standard version to C23, which should not
have impacted the kernel because it requests the gnu11 standard via
'-std=' in the main Makefile. However, the x86 compressed boot Makefile
uses its own set of KBUILD_CFLAGS without a '-std=' value (i.e., using
the default), resulting in errors from the kernel's definitions of bool,
true, and false in stddef.h, which are reserved keywords under C23.
./include/linux/stddef.h:11:9: error: expected identifier before ‘false’
11 | false = 0,
./include/linux/types.h:35:33: error: two or more data types in declaration specifiers
35 | typedef _Bool bool;
Set '-std=gnu11' in the x86 compressed boot Makefile to resolve the
error and consistently use the same C standard version for the entire
kernel.
Closes: https://lore.kernel.org/4OAhbllK7x4QJGpZjkYjtBYNLd_2whHx9oFiuZcGwtVR4hIzvduultkgfAIRZI3vQpZylu7Gl929HaYFRGeMEalWCpeMzCIIhLxxRhq4U-Y=@protonmail.com/
Closes: https://lore.kernel.org/Z4467umXR2PZ0M1H@tucnak/
Reported-by: Kostadin Shishmanov <kostadinshishmanov@xxxxxxxxxxxxxx>
Reported-by: Jakub Jelinek <jakub@xxxxxxxxxx>
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Cc:stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/all/20250121-x86-use-std-consistently-gcc-15-v1-1-8ab0acf645cb%40kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/boot/compressed/Makefile | 1 +
1 file changed, 1 insertion(+)
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -33,6 +33,7 @@ targets := vmlinux vmlinux.bin vmlinux.b
# avoid errors with '-march=i386', and future flags may depend on the target to
# be valid.
KBUILD_CFLAGS := -m$(BITS) -O2 $(CLANG_FLAGS)
+KBUILD_CFLAGS += -std=gnu11
KBUILD_CFLAGS += -fno-strict-aliasing -fPIE
KBUILD_CFLAGS += -Wundef
KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
Patches currently in stable-queue which might be from nathan@xxxxxxxxxx are
queue-5.15/x86-boot-use-std-gnu11-to-fix-build-with-gcc-15.patch
queue-5.15/efi-libstub-use-std-gnu11-to-fix-build-with-gcc-15.patch
queue-5.15/kbuild-move-wenum-enum-conversion-to-w-2.patch
