Re: [PATCH RESEND 1/1] perf build: Allow nested externs to enable BUILD_BUG() usage

From: Stephen Rothwell <sfr@canb.auug.org.au>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Namhyung Kim <namhyung@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux Next Mailing List <linux-next@vger.kernel.org>
Subject: Re: [PATCH RESEND 1/1] perf build: Allow nested externs to enable BUILD_BUG() usage
Date: Mon, 12 Oct 2020 16:13:38 +1100	[thread overview]
Message-ID: <20201012161338.3c94f6e5@canb.auug.org.au> (raw)
In-Reply-To: <20201012085936.241cc62d@canb.auug.org.au>

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Hi all,

On Mon, 12 Oct 2020 08:59:36 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> On Fri, 9 Oct 2020 14:41:11 +0200 Jiri Olsa <jolsa@redhat.com> wrote:
> >
> > On Fri, Oct 09, 2020 at 02:25:23PM +0200, Vasily Gorbik wrote:  
> > > Currently BUILD_BUG() macro is expanded to smth like the following:
> > >    do {
> > >            extern void __compiletime_assert_0(void)
> > >                    __attribute__((error("BUILD_BUG failed")));
> > >            if (!(!(1)))
> > >                    __compiletime_assert_0();
> > >    } while (0);
> > > 
> > > If used in a function body this obviously would produce build errors
> > > with -Wnested-externs and -Werror.
> > > 
> > > To enable BUILD_BUG() usage in tools/arch/x86/lib/insn.c which perf
> > > includes in intel-pt-decoder, build perf without -Wnested-externs.
> > > 
> > > Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
> > > Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>    
> > 
> > that one applied nicely ;-) thanks
> > 
> > Acked-by: Jiri Olsa <jolsa@redhat.com>  
> 
> I will apply that patch to the merge of the tip tree today (instead of
> reverting the series I reverted in Friday) (unless I get an update of
> the tip tree containing it, of course).

Tested-by: Stephen Rothwell <sfr@canb.auug.org.au> # build tested

-- 
Cheers,
Stephen Rothwell

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