linux-kernel - Re: [PATCH 1/1] perf build: Allow nested externs to enable BUILD

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Date:   Fri, 9 Oct 2020 14:25:20 +0200
From:   Vasily Gorbik <gor@...ux.ibm.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: [PATCH 1/1] perf build: Allow nested externs to enable
 BUILD_BUG() usage

On Fri, Oct 09, 2020 at 01:23:27PM +0200, Jiri Olsa wrote:
> On Fri, Oct 09, 2020 at 08:47:45AM +0200, Vasily Gorbik wrote:
> > Currently BUILD_BUG() macro is expanded to smth like the following:
...snip...
> > diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> > index 190be4fa5c21..8137a6046a47 100644
> > --- a/tools/perf/Makefile.config
> > +++ b/tools/perf/Makefile.config
> > @@ -16,7 +16,7 @@ $(shell printf "" > $(OUTPUT).config-detected)
> >  detected     = $(shell echo "$(1)=y"       >> $(OUTPUT).config-detected)
> >  detected_var = $(shell echo "$(1)=$($(1))" >> $(OUTPUT).config-detected)
> >  
> > -CFLAGS := $(EXTRA_CFLAGS) $(EXTRA_WARNINGS)
> > +CFLAGS := $(EXTRA_CFLAGS) $(filter-out -Wnested-externs,$(EXTRA_WARNINGS))
> 
> looks good, but I can't apply the patch with 'git am'
> 
> 	Applying: perf build: Allow nested externs to enable BUILD_BUG() usage
> 	error: patch failed: tools/perf/Makefile.config:16
> 	error: tools/perf/Makefile.config: patch does not apply
> 	Patch failed at 0001 perf build: Allow nested externs to enable BUILD_BUG() usage
> 	hint: Use 'git am --show-current-patch=diff' to see the failed patch
> 	When you have resolved this problem, run "git am --continue".
> 	If you prefer to skip this patch, run "git am --skip" instead.
> 	To restore the original branch and stop patching, run "git am --abort".
> 
> I wonder it's that picture at the bottom ;-)
> 
> jirka
> 
> 
> >  
> >  include $(srctree)/tools/scripts/Makefile.arch
> >  
> > -- 
> > ⣿⣿⣿⣿⢋⡀⣀⠹⣿⣿⣿⣿
> > ⣿⣿⣿⣿⠠⣶⡦⠀⣿⣿⣿⣿
> > ⣿⣿⣿⠏⣴⣮⣴⣧⠈⢿⣿⣿
> > ⣿⣿⡏⢰⣿⠖⣠⣿⡆⠈⣿⣿
> > ⣿⢛⣵⣄⠙⣶⣶⡟⣅⣠⠹⣿
> > ⣿⣜⣛⠻⢎⣉⣉⣀⠿⣫⣵⣿
> 

What? This makes tux and blind people very unhappy. Those are nothing
else but braille utf-8 characters. And I've seen people on lkml are
using those, i.e. debian icon in a signature. Oh, well... I'll avoid
using this signature in future.

BTW which branch did you try to apply it on? I've just checked perf/core
and there should be no conflicts as well. But I assume this should go
via objtool together with other changes which introduced that BUILD_BUG()
usage.
 
Anyhow I've resent the patch without fancy signatures included.