[PATCH] kbuild: Set NOSTDINC_FLAGS late to speed up compile (a little) (e8e69931) · Commits · 戴 / test

Move definition of NOSTDINC_FLAGS below inclusion of arch Makefile, so any arch specific settings to $(CC) takes effect before looking up the compiler include directory. The previous solution that replaced ':=' with '=' caused gcc to be invoked one additional time for each directory visited. This decreases kernel compile time with 0.1 second (3.6 -> 3.5 seconds) when running make on a fully built kernel Signed-off-by:

Sam Ravnborg <sam@ravnborg.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

Makefile

+4 −2

Original line number	Diff line number	Diff line
		@@ -332,9 +332,7 @@ KALLSYMS = scripts/kallsyms
		PERL = perl
		CHECK = sparse

		NOSTDINC_FLAGS = -nostdinc -isystem $(shell $(CC) -print-file-name=include)
		CHECKFLAGS := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__
		CHECKFLAGS += $(NOSTDINC_FLAGS)
		MODFLAGS = -DMODULE
		CFLAGS_MODULE = $(MODFLAGS)
		AFLAGS_MODULE = $(MODFLAGS)
		@@ -531,6 +529,10 @@ endif

		include $(srctree)/arch/$(ARCH)/Makefile

		# arch Makefile may override CC so keep this after arch Makefile is included
		NOSTDINC_FLAGS := -nostdinc -isystem $(shell $(CC) -print-file-name=include)
		CHECKFLAGS += $(NOSTDINC_FLAGS)

		# warn about C99 declaration after statement
		CFLAGS += $(call cc-option,-Wdeclaration-after-statement,)

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