linux-kernel - Re: [PATCH 1/4] perf ui progress: Make sure we always define step value

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Date:   Sat, 09 Sep 2017 12:09:51 +0200
From:   Milian Wolff <milian.wolff@...b.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 1/4] perf ui progress: Make sure we always define step value

On Freitag, 8. September 2017 15:26:42 CEST Arnaldo Carvalho de Melo wrote:
> Em Fri, Sep 08, 2017 at 03:16:37PM +0200, Milian Wolff escreveu:
> > On Freitag, 8. September 2017 14:05:07 CEST Jiri Olsa wrote:
> > > +++ b/tools/perf/ui/progress.c
> > > @@ -25,7 +25,7 @@ void ui_progress__update(struct ui_progress *p, u64
> > > adv)
> > > 
> > >  void ui_progress__init(struct ui_progress *p, u64 total, const char
> > >  *title)
> > > 
> > > {
> > > 
> > >  	p->curr = 0;
> > > 
> > > -	p->next = p->step = total / 16;
> > > +	p->next = p->step = total / 16 ?: 1;
> > > 
> > >  	p->total = total;
> > >  	p->title = title;
> > 
> > This is a GNU extension, does this compile with clang?
> 
> Huh?
> 
> [acme@...et linux]$ find tools/ -name "*.[ch]"| xargs grep ?: | wc -l
> 64
> [acme@...et linux]$ find . -name "*.[ch]"| xargs grep ?: | wc -l
> 725
> [acme@...et linux]$
> 
> And yes, tools/perf/ is built with clang regularly, I use containers to
> test build the tools/{perf,lib} codebase with gcc and clang on almost
> all distros, things like:

OK, thanks for the clarification. I was wondering because I didn't know about 
this syntax. Googling I found this: https://en.wikipedia.org/wiki/%3F:#C

Quote:

> A GNU extension to C allows omitting the second operand, and using 
implicitly the first operand as the second also:
>
>     a = x ? : y;

Cheers

-- 
Milian Wolff | milian.wolff@...b.com | Senior Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt Experts