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kconfig: Replace "cc-option-bit" with "cc-option-str"

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$(cc-option-bit) returns the flag it was given when the compiler accepts
it, and an empty string otherwise. It was originally only used
internally for machine bit flags, but it is generally useful[1].

Rename it to $(cc-option-str), which says what it returns rather than
what it was first used for, and extract the probe logic from the existing
$(cc-option) macro to reuse it. Additionally add support for an optional
fallback, much like the Kbuild cc-option macro. This can be used as:

	config CC_OPT_FOO
		def_string "$(cc-option-str,-fnew-option,-fold-option)"

If the fallback is omitted, it is just an empty string.

Build tested ARCH=x86_64 defconfig with GCC 16.2.0.

Assisted-by: LLM
Signed-off-by: Kees Cook <kees@kernel.org>
Tested-by: Julian Braha <julianbraha@gmail.com>
Reviewed-by: Julian Braha <julianbraha@gmail.com>
Link: https://patch.msgid.link/20260919005929.4077729-2-kees@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
This commit is contained in:
Kees Cook 2026-09-18 17:59:26 -07:00 committed by Nathan Chancellor
parent 651fb291c4
commit 889a621272
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GPG Key ID: 1D6B269171C01A96
1 changed files with 13 additions and 4 deletions
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17
scripts/Kconfig.include
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@ -23,9 +23,19 @@ success = $(if-success,$(1),y,n)
# Return n if <command> exits with 0, y otherwise
failure = $(if-success,$(1),n,y)
# $(cc-probe,<flag>)
# The command $(cc-option) and $(cc-option-str) test <flag> with. Not meant
# to be called directly; use one of those two instead.
cc-probe = trap "rm -rf .tmp_$$" EXIT; mkdir .tmp_$$; $(CC) -Werror $(CLANG_FLAGS) $(1) -c -x c /dev/null -o .tmp_$$/tmp.o
# $(cc-option,<flag>)
# Return y if the compiler supports <flag>, n otherwise
cc-option = $(success,trap "rm -rf .tmp_$$" EXIT; mkdir .tmp_$$; $(CC) -Werror $(CLANG_FLAGS) $(1) -c -x c /dev/null -o .tmp_$$/tmp.o)
cc-option = $(success,$(cc-probe,$(1)))
# $(cc-option-str,<flag>[,<fallback>])
# Return <flag> if the compiler supports it, <fallback> otherwise.
# <fallback> defaults to an empty string and is returned untested.
cc-option-str = $(if-success,$(cc-probe,$(1)),$(1),$(2))
# $(ld-option,<flag>)
# Return y if the linker supports <flag>, n otherwise
@ -61,9 +71,8 @@ ld-version := $(shell,set -- $(ld-info) && echo $2)
# machine bit flags
# $(m32-flag): -m32 if the compiler supports it, or an empty string otherwise.
# $(m64-flag): -m64 if the compiler supports it, or an empty string otherwise.
cc-option-bit = $(if-success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null,$(1))
m32-flag := $(cc-option-bit,-m32)
m64-flag := $(cc-option-bit,-m64)
m32-flag := $(cc-option-str,-m32)
m64-flag := $(cc-option-str,-m64)
# Test whether the compiler can link userspace applications
cc_can_link_user = $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(1))