linux-kernel - Re: [PATCH v3] tools/lib/traceevent, perf tools: Handle %pU format correctly

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Date:   Mon, 21 Oct 2019 22:30:37 +0800
From:   Qu Wenruo <quwenruo.btrfs@....com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Qu Wenruo <wqu@...e.com>, linux-btrfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-trace-devel@...r.kernel.org
Subject: Re: [PATCH v3] tools/lib/traceevent, perf tools: Handle %pU format
 correctly



On 2019/10/21 下午10:24, Steven Rostedt wrote:
> On Mon, 21 Oct 2019 22:03:21 +0800
> Qu Wenruo <quwenruo.btrfs@....com> wrote:
> 
>> On 2019/10/21 下午9:56, Steven Rostedt wrote:
>>> On Mon, 21 Oct 2019 17:47:30 +0800
>>> Qu Wenruo <wqu@...e.com> wrote:
>>>   
>>>> +static void print_uuid_arg(struct trace_seq *s, void *data, int size,
>>>> +			   struct tep_event *event, struct tep_print_arg *arg)
>>>> +{
>>>> +	unsigned char *buf;
>>>> +	int i;
>>>> +
>>>> +	if (arg->type != TEP_PRINT_FIELD) {
>>>> +		trace_seq_printf(s, "ARG TYPE NOT FIELID but %d", arg->type);
>>>> +		return;
>>>> +	}
>>>> +
>>>> +	if (!arg->field.field) {
>>>> +		arg->field.field = 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 = data + arg->field.field->offset;
>>>> +
>>>> +	for (i = 0; i < 8; i++) {
>>>> +		trace_seq_printf(s, "%02x", buf[2 * i]);
>>>> +		trace_seq_printf(s, "%02x", buf[2 * i + 1]);
>>>> +		if (1 <= i && i <= 4)  
>>>
>>> I'm fine with this patch except for one nit. The above is hard to read
>>> (in my opinion), and I absolutely hate the "constant" compare to
>>> "variable" notation. Please change the above to:
>>>
>>> 		if (i >= 1 && i <= 4)  
>>
>> Isn't this ( 1 <= i && i <= 4 ) easier to find out the lower and upper
>> boundary? only two numbers, both at the end of the expression.
> 
> I don't read it like that.
> 
>>
>> I feel that ( i >= 1 && i <= 4 ) easier to write, but takes me extra
>> half second to read, thus I changed to the current one.
> 
> 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
> 
>   "If one is less than or equal to i and i is less than or equal to
>   four."
> 
> Or
> 
>   "If i is greater than or equal to one and i is less than or equal to
>    four."
> 
> ?
> 
> I read it the second way, and I believe most English speakers read it
> that way too.
> 
> 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.
> 
> -- Steve
> 
> 



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