linux-kernel - Re: [PATCH 1/1] workqueue: use type int instead of bool to index array

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Date:   Thu, 7 Sep 2017 00:04:59 +0800
From:   zijun_hu <zijun_hu@...o.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     zijun_hu@....com, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        jiangshanlai@...il.com
Subject: Re: [PATCH 1/1] workqueue: use type int instead of bool to index
 array

On 2017/9/6 22:33, Tejun Heo wrote:
> Hello,
> 
> On Wed, Sep 06, 2017 at 11:34:14AM +0800, zijun_hu wrote:
>> From: zijun_hu <zijun_hu@....com>
>>
>> type bool is used to index three arrays in alloc_and_link_pwqs()
>> it doesn't look like conventional.
>>
>> it is fixed by using type int to index the relevant arrays.
> 
> bool is a uint type which can be either 0 or 1.  I don't see what the
> benefit of this patch is.q
> 
bool is NOT a uint type now, it is a new type introduced by gcc, it is
rather different with "typedef int bool" historically
see following code segments for more info about type bool
	bool v = 0x10;
	printf("v = %d\n", v);
the output is v = 1.

it maybe cause a invalid array index if bool is represented as uint
bool highpri = wq->flags & WQ_HIGHPRI; WQ_HIGHPRI = 1 << 4,
@highpri maybe 16, but the number of array elements is 2.

bool is a logic value, the valid value is true or false. 
indexing array by type bool is not a good program custom

it is more extendable to use type int, type bool maybe is improper if the number of
array elements is extended to more than 2 in future

besides, the relevant array is indexed by type int in many other places of the
same source file. this patch can keep consistency
>