Since commit 80b6093b55e3 ("kbuild: add -Wundef to KBUILD_CPPFLAGS for W=1 builds"), building with W=1 detects misuse of #(el)if. $ make W=1 ARCH=s390 CROSS_COMPILE=s390x-linux-gnu- [snip] arch/s390/boot/decompressor.c:28:7: warning: "CONFIG_KERNEL_ZSTD" is not defined, evaluates to 0 [-Wundef] 28 | #elif CONFIG_KERNEL_ZSTD | ^~~~~~~~~~~~~~~~~~ This issue has been hidden because arch/s390/boot/Makefile overwrites KBUILD_CFLAGS, dropping -Wundef. CONFIG_KERNEL_ZSTD is a bool option. #elif defined() should be used. The line #ifdef CONFIG_KERNEL_BZIP2 is fine, but I changed it for consistency. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Link: https://lore.kernel.org/r/20230106161024.2373602-1-masahiroy@kernel.org Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Linux kernel ============ There are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. Please read Documentation/admin-guide/README.rst first. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. The formatted documentation can also be read online at: https://www.kernel.org/doc/html/latest/ There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.
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