Unverified Commit 2a0a3080 authored Dec 23, 2025 by Thomas Weißschuh Committed by Nathan Chancellor Jan 16, 2026

kbuild: uapi: drop dependency on CC_CAN_LINK

The header tests try to compile each header. Some UAPI headers depend on
libc headers so they need a full userspace toolchain to build. This
dependency is expressed in kconfig as a dependency on CC_CAN_LINK.
Many kernel builds do not satisfy CC_CAN_LINK as they only use a
minimal kernel (cross-) compiler. In those configurations the UAPI
headers are not tested at all.

However most UAPI headers do not even depend on any libc headers,
and such dependencies are undesired in any case. Also the static
analysis performed by headers_check.pl does not need CC_CAN_LINK.

Drop the hard dependency on CC_CAN_LINK and instead skip the affected
compilation step for exactly those headers which require libc.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://patch.msgid.link/20251223-uapi-nostdinc-v1-5-d91545d794f7@linutronix.de

Signed-off-by: Nathan Chancellor <nathan@kernel.org>

parent c25d01e1

init/Kconfig

+1 −1

Original line number	Diff line number	Diff line
		@@ -247,7 +247,7 @@ config WERROR

		config UAPI_HEADER_TEST
		bool "Compile test UAPI headers"
		depends on HEADERS_INSTALL && CC_CAN_LINK
		depends on HEADERS_INSTALL
		help
		Compile test headers exported to user-space to ensure they are
		self-contained, i.e. compilable as standalone units.

usr/include/Makefile

+2 −1

Original line number	Diff line number	Diff line
		@@ -151,7 +151,8 @@ endif
		always-y := $(patsubst $(obj)/%.h,%.hdrtest, $(shell find $(obj) -name '*.h' 2>/dev/null))

		target-no-libc = $(filter-out $(uses-libc), $*.h)
		target-can-compile = $(filter-out $(no-header-test), $*.h)
		target-can-compile = $(and $(filter-out $(no-header-test), $*.h), \
		$(or $(CONFIG_CC_CAN_LINK), $(target-no-libc)))

		# Include the header twice to detect missing include guard.
		quiet_cmd_hdrtest = HDRTEST $<