linux-kernel - Re: [PATCH] tools, perf: Add asprintf replacement

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Message-ID: <20140318181337.GD6482@ghostprotocols.net>
Date:	Tue, 18 Mar 2014 15:13:37 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	Andi Kleen <andi@...stfloor.org>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, peterz@...radead.org,
	eranian@...gle.com, namhyung@...nel.org, jolsa@...hat.com
Subject: Re: [PATCH] tools, perf: Add asprintf replacement

Em Tue, Mar 18, 2014 at 08:05:33AM -0700, Andi Kleen escreveu:
> > Humm, this unconditionally replaces it with an alternative that limits
> > the buffer to a fixed size :-\
> 
> Better than corrupting memory.

Yes, it is better than corrupting memory, use the less ugly, good point.
 
> I guess you could use two passes to avoid the limit, but it would surprise me
> if anything in perf needs more than 1K of printf. One issue 
> with doing two passes is that I wasn't sure the snprintf return

The return of snprintf is crazy, that is why we use scnprintf.

> value would work properly on all libcs (e.g. the weirdo one Android uses)
> 
> > 
> > Do you recall at least one of those old glibc version/release number?
 
> glibc-2.13-2.x86_64 (FC14)

> > A reproducer? So that I can try to reproduce it here and try to polish
> > this a bit more...
> 
> I saw it with perf report --branch-history in TUI mode and then pressing
> e. But even running valgrind in stdio mode showed some corruption.
> Without the patch also using some of the --call-graph options segfaulted.

Thanks for the data points,

- Arnaldo
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