linux-kernel - Re: (trivia) remove useless typecast around `jif' variable

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Date:	Mon, 5 Mar 2007 17:29:35 +0100 (MET)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Michael Tokarev <mjt@....msk.ru>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: (trivia) remove useless typecast around `jif' variable

On Mar 5 2007 19:12, Michael Tokarev wrote:

>Date: Mon,  5 Mar 2007 19:12:51 +0300 (MSK)
>From: Michael Tokarev <mjt@....msk.ru>
>To: undisclosed-recipients:  ;

I have no clue what you sent it to, so I added linux-kernel again.



>Subject: (trivia) remove useless typecast around `jif' variable
>
>in fs/proc/proc_misc.c:show_stat() routine (which handles /proc/stat
>file), there's a local variable named 'jif' of type unsigned long,
>declared as following:
>
>static int show_stat(struct seq_file *p, void *v)
>{
>        unsigned long jif;
>
>But later on, it's explicitly casted to (unsigned long) in printf().
>Remove the useless cast, to let the compiler to do the work for us
>in case we'll want to use different type here (say, u64 or something).

In case we wanted to use different types, we would also have to
change the accompanying %lu into %llu. Only changing jif to u64 will
cause a problem, as the compiler does _not_ automatically
promote/demote types in varargs that already have a certain size. In
other words,

int foo(unsigned long x)
{
        printk("%llu\n", x);  /* and */
        printk("%lu\n", x);
}

will throw a warning (rightfully if you ask me).



Jan
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