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

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Jun 28, 2018 at 06:52:55PM +0200, Paul Menzel wrote:
> Dear Greg,
> 
> 
> On 06/28/18 01:51, Greg KH wrote:
> > On Wed, Jun 27, 2018 at 03:10:00PM +0200, Paul Menzel wrote:
> >> From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> >> Date: Sun, 8 Apr 2018 23:35:28 +0200
> >>
> >> commit 9564a8cf422d7b58f6e857e3546d346fa970191e upstream.
> >>
> >> 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.
> >>
> >> Link: https://bugzilla.kernel.org/show_bug.cgi?id=197847
> >> Cc: Randy Dunlap <rdunlap@infradead.org>
> >> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> >> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> >> Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
> >> ---
> >>
> >> Fix one conflict in `scripts/Kbuild.include`.
> > 
> > What stable kernel(s) are you wanting this applied to?
> 
> I tested, that it’s needed for 4.9 and 4.14. Strangely, it’s still not
> enough. I need the additional attached patch to be able to build the
> attached configuration with the stable series, while on master commit
> 9564a8cf (Kbuild: fix # escaping in .cmd files for future Make) seems
> to be enough, despite the same lines being present in
> `tools/build/Build.include`.

That's a crazy thing for make to do, ugh, tools should know better...

Anyway, both of these are now queued up, thanks.

greg k-h