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Subject: Re: [PATCH v3] tools/lib/traceevent, perf tools: Handle %pU format
 correctly
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Qu Wenruo <wqu@suse.com>, linux-btrfs@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-trace-devel@vger.kernel.org
References: <20191021094730.57332-1-wqu@suse.com>
 <20191021095625.2dfe3359@gandalf.local.home>
 <3830b0c5-5b76-36c1-5e3a-64dad62f76fb@gmx.com>
 <20191021102408.3bb4aa8b@gandalf.local.home>
From:   Qu Wenruo <quwenruo.btrfs@gmx.com>
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Message-ID: <6bc13ae1-9f26-afaa-ddfa-f1dd1cdcf6df@gmx.com>
Date:   Mon, 21 Oct 2019 22:30:37 +0800
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On 2019/10/21 =E4=B8=8B=E5=8D=8810:24, Steven Rostedt wrote:
> On Mon, 21 Oct 2019 22:03:21 +0800
> Qu Wenruo <quwenruo.btrfs@gmx.com> wrote:
>=20
>> On 2019/10/21 =E4=B8=8B=E5=8D=889:56, Steven Rostedt wrote:
>>> On Mon, 21 Oct 2019 17:47:30 +0800
>>> Qu Wenruo <wqu@suse.com> wrote:
>>>  =20
>>>> +static void print_uuid_arg(struct trace_seq *s, void *data, int siz=
e,
>>>> +			   struct tep_event *event, struct tep_print_arg *arg)
>>>> +{
>>>> +	unsigned char *buf;
>>>> +	int i;
>>>> +
>>>> +	if (arg->type !=3D TEP_PRINT_FIELD) {
>>>> +		trace_seq_printf(s, "ARG TYPE NOT FIELID but %d", arg->type);
>>>> +		return;
>>>> +	}
>>>> +
>>>> +	if (!arg->field.field) {
>>>> +		arg->field.field =3D tep_find_any_field(event, arg->field.name);
>>>> +		if (!arg->field.field) {
>>>> +			do_warning("%s: field %s not found",
>>>> +				   __func__, arg->field.name);
>>>> +			return;
>>>> +		}
>>>> +	}
>>>> +	if (arg->field.field->size < 16) {
>>>> +		trace_seq_printf(s, "INVALID UUID: size have %u expect 16",
>>>> +				arg->field.field->size);
>>>> +		return;
>>>> +	}
>>>> +	buf =3D data + arg->field.field->offset;
>>>> +
>>>> +	for (i =3D 0; i < 8; i++) {
>>>> +		trace_seq_printf(s, "%02x", buf[2 * i]);
>>>> +		trace_seq_printf(s, "%02x", buf[2 * i + 1]);
>>>> +		if (1 <=3D i && i <=3D 4) =20
>>>
>>> I'm fine with this patch except for one nit. The above is hard to rea=
d
>>> (in my opinion), and I absolutely hate the "constant" compare to
>>> "variable" notation. Please change the above to:
>>>
>>> 		if (i >=3D 1 && i <=3D 4) =20
>>
>> Isn't this ( 1 <=3D i && i <=3D 4 ) easier to find out the lower and u=
pper
>> boundary? only two numbers, both at the end of the expression.
>=20
> I don't read it like that.
>=20
>>
>> I feel that ( i >=3D 1 && i <=3D 4 ) easier to write, but takes me ext=
ra
>> half second to read, thus I changed to the current one.
>=20
> How do you read it in English?

How about mathematics interval?

i in [1, 4].

It looks way easier and simpler no matter what language you speak.

Thanks,
Qu
>=20
>   "If one is less than or equal to i and i is less than or equal to
>   four."
>=20
> Or
>=20
>   "If i is greater than or equal to one and i is less than or equal to
>    four."
>=20
> ?
>=20
> I read it the second way, and I believe most English speakers read it
> that way too.
>=20
> It took me a minute or two to understand the original method, because
> my mind likes to take a variable and keep it on the same side of the
> comparison, and the variable should always be first.
>=20
> -- Steve
>=20
>=20


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