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Date: Mon, 20 Apr 2015 20:06:45 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>, linux-kernel@vger.kernel.org,
        David Ahern <dsahern@gmail.com>,
        Frederic Weisbecker <fweisbec@gmail.com>, Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@gmail.com>,
        Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 03/44] perf tools: Add user events for AUX area tracing
Message-ID: <20150420230645.GV11111@kernel.org>
References: <1428594864-29309-1-git-send-email-adrian.hunter@intel.com>
 <1428594864-29309-4-git-send-email-adrian.hunter@intel.com>
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Em Thu, Apr 09, 2015 at 06:53:43PM +0300, Adrian Hunter escreveu:
> +static int skipn(int fd, off_t n)
> +{
> +	char buf[4096];
> +	ssize_t ret;
> +
> +	while (n > 0) {
> +		ret = read(fd, buf, MIN(n, sizeof(buf)));
> +		if (ret <= 0)
> +			return ret;
> +		n -= ret;
> +	}
> +
> +	return 0;

We have min() in tools/perf/util/include/linux/kernel.h, and that is
what is being used elsewhere in tools/perf/:

[acme@zoo linux]$ find tools/perf/ -name "*.[ch]" | xargs grep '\<min('
| wc -l
20
[acme@zoo linux]$ find tools/perf/ -name "*.[ch]" | xargs grep '\<max('
| wc -l
8
[acme@zoo linux]$

I noticed it tho because of this:

util/session.c: In function ‘skipn’:
util/session.c:279:28: error: comparison between signed and unsigned
integer expressions [-Werror=sign-compare]
   ret = read(fd, buf, MIN(n, sizeof(buf)));
                            ^
util/session.c:279:47: error: signed and unsigned type in conditional
expression [-Werror=sign-compare]
   ret = read(fd, buf, MIN(n, sizeof(buf)));
                                               ^
cc1: all warnings being treated as errors
make[3]: *** [/tmp/build/perf/util/session.o] Error 1
make[3]: *** Waiting for unfinished jobs....

Fixing it to be:

    ret = read(fd, buf, min(n, (off_t)sizeof(buf)));

Ok?

- Arnaldo