linux-kernel - Re: [PATCH v4 03/15] perf util: refactor inline

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Date:   Sun, 08 Oct 2017 21:53:20 +0200
From:   Milian Wolff <milian.wolff@...b.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     acme@...nel.org, jolsa@...nel.org,
        Jin Yao <yao.jin@...ux.intel.com>,
        Linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Jiri Olsa <jolsa@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>, kernel-team@....com
Subject: Re: [PATCH v4 03/15] perf util: refactor inline_list to operate on symbols

On Donnerstag, 5. Oktober 2017 03:56:13 CEST Namhyung Kim wrote:
> Hi Milian,
> 
> On Sun, Oct 01, 2017 at 04:30:48PM +0200, Milian Wolff wrote:
> > This is a requirement to create real callchain entries for inlined
> > frames.
> > 
> > Since the list of inlines usually contains the target symbol too,
> > i.e. the location where the frames get inlined to, we alias that
> > symbol and reuse it as-is is. This ensures that other dependent
> > functionality keeps working, most notably annotation of the
> > target frames.
> > 
> > For all other entries in the inline_list, a fake symbol is created.
> > These are marked by new 'inlined' member which is set to true. Only
> > those symbols are managed by the inline_list and get freed when
> > the inline_list is deleted from within inline_node__delete.
> > 
> > Cc: Jiri Olsa <jolsa@...hat.com>
> > Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> > Cc: David Ahern <dsahern@...il.com>
> > Cc: Namhyung Kim <namhyung@...nel.org>
> > Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > Cc: Yao Jin <yao.jin@...ux.intel.com>
> > Signed-off-by: Milian Wolff <milian.wolff@...b.com>
> > ---
> 
> [SNIP]
> 
> > +static struct symbol *new_inline_sym(struct dso *dso,
> > +				     struct symbol *base_sym,
> > +				     const char *funcname)
> > +{
> > +	struct symbol *inline_sym;
> > +	char *demangled = NULL;
> > +
> > +	if (dso) {
> > +		demangled = dso__demangle_sym(dso, 0, funcname);
> > +		if (demangled)
> > +			funcname = demangled;
> > +	}
> > +
> > +	if (strcmp(funcname, base_sym->name) == 0) {
> 
> It seems you need to check availability of base_sym first as 'else'
> statement below checks it.  Or if it's guaranteed not NULL (I think
> you make it so later), remove the check (and add an assert?) instead.

I'll make it fail-safe by adding the check before calling strcmp. Well 
spotted, many thanks!

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