linux-kernel - Re: [PATCH] objtool: fix build with future Make

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Date:   Sun, 25 Mar 2018 16:42:09 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kbuild@...r.kernel.org,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] objtool: fix build with future Make

On 03/25/2018 03:32 PM, Rasmus Villemoes wrote:
> I tried building using a freshly built Make (4.2.1-69-g8a731d1), but 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.
> 
> There are likely other places in the tree that will need fixing, so
> cc-ing Kbuild, but with this at least a x86-64 defconfig builds.

Hi,

For one of these patches, can we say:
Fixes https://bugzilla.kernel.org/show_bug.cgi?id=197847
?

Thanks.

> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> ---
>  tools/objtool/Makefile         | 2 +-
>  tools/scripts/Makefile.include | 2 ++
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
> index e6acc281dd37..8ae824dbfca3 100644
> --- a/tools/objtool/Makefile
> +++ b/tools/objtool/Makefile
> @@ -35,7 +35,7 @@ CFLAGS   += -Wall -Werror $(WARNINGS) -fomit-frame-pointer -O2 -g $(INCLUDES)
>  LDFLAGS  += -lelf $(LIBSUBCMD)
>  
>  # Allow old libelf to be used:
> -elfshdr := $(shell echo '\#include <libelf.h>' | $(CC) $(CFLAGS) -x c -E - | grep elf_getshdr)
> +elfshdr := $(shell echo '$(pound)include <libelf.h>' | $(CC) $(CFLAGS) -x c -E - | grep elf_getshdr)
>  CFLAGS += $(if $(elfshdr),,-DLIBELF_USE_DEPRECATED)
>  
>  AWK = awk
> diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
> index dd614463d4d6..495066bafbe3 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
> @@ -120,3 +120,5 @@ ifneq ($(silent),1)
>  	QUIET_UNINST   = @printf '  UNINST   %s\n' $1;
>    endif
>  endif
> +
> +pound := \#
> 


-- 
~Randy