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    SubjectRe: [PATCH] kbuild: strip the last slash in KBUILD_EXTMOD
    On Sat, Mar 11, 2017 at 10:34:50PM +0900, Masahiro Yamada wrote:
    >Hi Wei,
    >
    >
    >2017-02-23 0:08 GMT+09:00 Wei Yang <richard.weiyang@gmail.com>:
    >> Current kbuild will build the target again if we run "make M=dir" and "make
    >> M=dir/" by turns, since if_changed will see the prerequisite is changed.
    >> The behavior may confuse the user a little, since actually we are building
    >> the same target and no difference.
    >>
    >> According to current implementation in scripts/Makefile.build, the obj
    >> passed to next level is a directory name with last slash stripped. This
    >> patch strips the last slash in KBUILD_EXTMOD which is assigned from "M=".
    >>
    >> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
    >> ---
    >> Makefile | 6 ++++--
    >> 1 file changed, 4 insertions(+), 2 deletions(-)
    >>
    >> diff --git a/Makefile b/Makefile
    >> index b1037774e8e8..db6ed60928ab 100644
    >> --- a/Makefile
    >> +++ b/Makefile
    >> @@ -184,13 +184,15 @@ endif
    >> # Old syntax make ... SUBDIRS=$PWD is still supported
    >> # Setting the environment variable KBUILD_EXTMOD take precedence
    >> ifdef SUBDIRS
    >> - KBUILD_EXTMOD ?= $(SUBDIRS)
    >> + __KBUILD_EXTMOD ?= $(SUBDIRS)
    >> endif
    >>
    >> ifeq ("$(origin M)", "command line")
    >> - KBUILD_EXTMOD := $(M)
    >> + __KBUILD_EXTMOD := $(M)
    >> endif
    >>
    >> +KBUILD_EXTMOD = $(patsubst %/,%,$(__KBUILD_EXTMOD))
    >> +
    >> # If building an external module we do not care about the all: rule
    >> # but instead _all depend on modules
    >> PHONY += all
    >
    >This patch would break a use-case
    >where KBUILD_EXTMOD is given as an environment.
    >

    Hi, Masahiro

    Thanks for your comment.

    Got your point, you are right.

    >
    >
    >Maybe adding the following should be enough?
    >
    >KBUILD_EXTMOD := $(patsubst %/,%,$(KBUILD_EXTMOD))
    >

    Yep, it looks good.

    BTW, I found another interesting thing.

    make M=dir////

    is also a valid target in kbuild.

    Even this is a very rare case, I plan to use this to handle it.

    KBUILD_EXTMOD := $(subst $(CURDIR)/,,$(KBUILD_EXTMOD))

    This also works for an out tree build.

    I would send out v2 soon, hope you like this.

    >
    >--
    >Best Regards
    >Masahiro Yamada

    --
    Wei Yang
    Help you, Help me
    [unhandled content-type:application/pgp-signature]
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