Re: [PATCH] objtool: fix build with future Make

From: Randy Dunlap
Date: Sun Mar 25 2018 - 19:42:25 EST


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 âorc_dumpâ:
> orc_dump.c:106:2: error: âelf_getshnumâ 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@xxxxxxxxxxxxxxxxxx>
> ---
> 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