linux-kernel - Re: [PATCH v2] Kbuild: fix # escaping in .cmd files for future Make

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Message-ID: <CAK7LNARmy0COjgWgSa7uB426Me_jAmeJCDSQkJWZoTVwqoA1CA@mail.gmail.com>
Date:   Mon, 9 Apr 2018 22:31:02 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] Kbuild: fix # escaping in .cmd files for future Make

2018-04-09 6:35 GMT+09:00 Rasmus Villemoes <linux@...musvillemoes.dk>:
> I tried building using a freshly built Make (4.2.1-69-g8a731d1), but
> already the objtool build broke with
>
> orc_dump.c: In function ‘orc_dump’:
> orc_dump.c:106:2: error: ‘elf_getshnum’ is deprecated [-Werror=deprecated-declarations]
>   if (elf_getshdrnum(elf, &nr_sections)) {
>
> Turns out that with that new Make, the backslash was not removed, so cpp
> didn't see a #include directive, grep found nothing, and
> -DLIBELF_USE_DEPRECATED was wrongly put in CFLAGS.
>
> Now, that new Make behaviour is documented in their NEWS file:
>
>   * WARNING: Backward-incompatibility!
>     Number signs (#) appearing inside a macro reference or function invocation
>     no longer introduce comments and should not be escaped with backslashes:
>     thus a call such as:
>       foo := $(shell echo '#')
>     is legal.  Previously the number sign needed to be escaped, for example:
>       foo := $(shell echo '\#')
>     Now this latter will resolve to "\#".  If you want to write makefiles
>     portable to both versions, assign the number sign to a variable:
>       C := \#
>       foo := $(shell echo '$C')
>     This was claimed to be fixed in 3.81, but wasn't, for some reason.
>     To detect this change search for 'nocomment' in the .FEATURES variable.
>
> This also fixes up the two make-cmd instances to replace # with $(pound)
> rather than with \#. There might very well be other places that need
> similar fixup in preparation for whatever future Make release contains
> the above change, but at least this builds an x86_64 defconfig with the
> new make.
>
> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=197847
> Cc: Randy Dunlap <rdunlap@...radead.org>
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> ---

Applied to linux-kbuild.  Thanks!


-- 
Best Regards
Masahiro Yamada