kbuild: remove extra ifdef/endif of top Makefile (b8b0618c) · Commits · 戴 / test

The GNU make's origin function know undefined variable well, so the outer ifdef/endif conditional checking is unneeded. From `info make` documentation, origin will return `undefined' if VARIABLE was never defined. `command line' if VARIABLE was defined on the command line. ... Therefore, $(origin V) will get a value anyway, killing ifdef/endif is viable and safe. Furthermore, I've checked the minimal requirements from Documentation/Changes is GNU make 3.79.1, and that version of GNU make has support of origin function well already, so now it's safe to kill the outer conditional checking, without upgrading the minimal requirements. Signed-off-by:

Cheng Renquan <crq@kernel.org> Signed-off-by:

Sam Ravnborg <sam@ravnborg.org>

Makefile

+9 −17

Original line number	Diff line number	Diff line
		@@ -35,11 +35,9 @@ MAKEFLAGS += -rR --no-print-directory
		# To put more focus on warnings, be less verbose as default
		# Use 'make V=1' to see the full commands

		ifdef V
		ifeq ("$(origin V)", "command line")
		KBUILD_VERBOSE = $(V)
		endif
		endif
		ifndef KBUILD_VERBOSE
		KBUILD_VERBOSE = 0
		endif
		@@ -54,11 +52,9 @@ endif
		# See the file "Documentation/sparse.txt" for more details, including
		# where to get the "sparse" utility.

		ifdef C
		ifeq ("$(origin C)", "command line")
		KBUILD_CHECKSRC = $(C)
		endif
		endif
		ifndef KBUILD_CHECKSRC
		KBUILD_CHECKSRC = 0
		endif
		@@ -69,12 +65,10 @@ endif
		ifdef SUBDIRS
		KBUILD_EXTMOD ?= $(SUBDIRS)
		endif
		ifdef M

		ifeq ("$(origin M)", "command line")
		KBUILD_EXTMOD := $(M)
		endif
		endif


		# kbuild supports saving output files in a separate directory.
		# To locate output files in a separate directory two syntaxes are supported.
		@@ -98,11 +92,9 @@ ifeq ($(KBUILD_SRC),)

		# OK, Make called in directory where kernel src resides
		# Do we want to locate output files in a separate directory?
		ifdef O
		ifeq ("$(origin O)", "command line")
		KBUILD_OUTPUT := $(O)
		endif
		endif

		# That's our default target when none is given on the command line
		PHONY := _all

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