linux-kernel - Re: [RFC PATCH] cleanup: make scoped

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Message-ID: <34d2f916-3551-4b75-b87a-9d413662369b@intel.com>
Date: Mon, 30 Sep 2024 14:33:28 +0200
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Markus Elfring <Markus.Elfring@....de>
CC: LKML <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
	<kernel-janitors@...r.kernel.org>,
	<nex.sw.ncis.osdt.itp.upstreaming@...el.com>,
	Amadeusz Sławiński
	<amadeuszx.slawinski@...ux.intel.com>, Andy Shevchenko
	<andriy.shevchenko@...el.com>, Simon Horman <horms@...nel.org>, Tony Nguyen
	<anthony.l.nguyen@...el.com>, Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC PATCH] cleanup: make scoped_guard() to be return-friendly

On 9/30/24 13:30, Markus Elfring wrote:
> …
>> Current scoped_guard() implementation does not support that,
>> due to compiler complaining:
> …
>> +++ b/include/linux/cleanup.h
>> @@ -168,9 +168,16 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
>>
>>   #define __guard_ptr(_name) class_##_name##_lock_ptr
>>
>> -#define scoped_guard(_name, args...)					\
>> -	for (CLASS(_name, scope)(args),					\
>> -	     *done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)
>> +#define scoped_guard(_name, args...)	\
>> +	__scoped_guard_labeled(__UNIQUE_ID(label), _name, args)
>> +
>> +#define __scoped_guard_labeled(_label, _name, args...)	\
>> +	if (0)						\
>> +		_label: ;				\
>> +	else						\
>> +		for (CLASS(_name, scope)(args);		\
>> +		     __guard_ptr(_name)(&scope), 1;	\
>> +		     ({ goto _label; }))
>>
>>   #define scoped_cond_guard(_name, _fail, args...) \
>>   	for (CLASS(_name, scope)(args), \
> 
> * How do you think about to define such macros before their use?

will do, no problem

> 
> * Would you ever like to avoid reserved identifiers in such source code?
>    https://wiki.sei.cmu.edu/confluence/display/c/DCL37-C.+Do+not+declare+or+define+a+reserved+identifier

we already don't care about this guideline (see __guard_ptr())

OTOH there is DCL37-C-EX3 that says "does not apply for std lib",
and here (in the kernel) we don' need stdlib, (or for the purpose of
bureaucracy we ARE the stdlib for ourselves)

> 
> 
> Regards,
> Markus