linux-kernel - Re: [PATCH] printf: Emit "SUCCESS" if NULL is passed for %pe

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Message-ID: <YzbdmJvcPiYAIalt@alley>
Date:   Fri, 30 Sep 2022 14:14:16 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH] printf: Emit "SUCCESS" if NULL is passed for %pe

On Fri 2022-09-30 13:10:50, Uwe Kleine-König wrote:
> For code that emits a string representing a usual return value it's
> convenient to have a 0 result in a string representation of success
> instead of "00000000".

Does it really always mean success, please?

IMHO, if a function returns a pointer then typically only a valid
pointer means success. Error code means some reasonable explanation
of the failure. And NULL should never happen.

For example:

struct bla *find_bla(int key)
{
	struct bla *b;

	/* Try to get bla using the given key */
	...

	if (succeded)
		return b;

	/* Did not find bla for the given key */
	return -EINVAL;

}

It might be used:

int process_bla()
{
	struct bla *b;

	b = get_bla();
	if (IS_ERR(b))
		return PTR_ERR(b);

	/* do something with b */
	...
}

If get_bla() returns NULL then it means a super fault. It means
that get_bla() failed and did not know why.

IMHO, this patch might do more harm than good.

Best Regards,
Petr