linux-kernel - Re: [PATCH 03/22] tools lib traceevent: Add traceevent_host

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Message-ID: <87ob59rliz.fsf@sejong.aot.lge.com>
Date:	Mon, 25 Nov 2013 16:24:52 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	David Ahern <dsahern@...il.com>
Subject: Re: [PATCH 03/22] tools lib traceevent: Add traceevent_host_bigendian function

Hi Steve,

On Sat, 23 Nov 2013 03:27:08 -0500, Steven Rostedt wrote:
> On Fri, 22 Nov 2013 23:22:52 +0900
> Namhyung Kim <namhyung@...nel.org> wrote:
>
>> 2013-11-21 (목), 12:01 +0100, Jiri Olsa:
>> > Adding traceevent_host_bigendian function to get host
>> > endianity. It's used in following patches.
>> 
>> [SNIP]
>> > +static inline int traceevent_host_bigendian(void)
>> > +{
>> > +	unsigned char str[] = { 0x1, 0x2, 0x3, 0x4 };
>> > +	unsigned int *ptr;
>> > +
>> > +	ptr = (unsigned int *)str;
>> > +	return *ptr == 0x01020304;
>> 
>> Is it safe for every architecture supported - especially ones that
>> require stricter alignment?  I know many architectures/compilers align
>> stack but not sure doing this is safe for all architecture.
>
> Would you prefer this (I tested it on both a big and little endian)
>
> {
> 	unsigned char str[] = { 0x1, 0x2, 0x3, 0x4 };
> 	unsigned int val;
>
> 	memcpy(&val, str, 4);
> 	return val == 0x01020304;
> }

Yeah, looks good to me.

Thanks,
Namhyung
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