linux-kernel - Re: [PATCH] Add human-readable units modifier to vsnprintf()

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Date:	Tue, 22 May 2012 22:10:48 -0700
From:	Joe Perches <joe@...ches.com>
To:	Kent Overstreet <koverstreet@...gle.com>
Cc:	Tejun Heo <tejun@...gle.com>, linux-bcache@...r.kernel.org,
	linux-kernel@...r.kernel.org, dm-devel@...hat.com, agk@...hat.com
Subject: Re: [PATCH] Add human-readable units modifier to vsnprintf()

On Wed, 2012-05-23 at 00:50 -0400, Kent Overstreet wrote:
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
[]
> @@ -1002,6 +1023,7 @@ int format_decode(const char *fmt, struct printf_spec *spec)
>  		case ' ': spec->flags |= SPACE;   break;
>  		case '#': spec->flags |= SPECIAL; break;
>  		case '0': spec->flags |= ZEROPAD; break;
> +		case 'h': spec->flags |= HUNITS;  break;
>  		default:  found = false;
>  		}
>  

I think that doesn't work well because
gcc __attribute__((format(printf, x, y)))
verification fails.  It's also possible
to confuse it with printf's own 'h' / 
integer precision use.

$ cat h.c
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char** argv)
{
  printf("%h02u\n", 1);
  return 0;
}

$ gcc h.c
h.c: In function ‘main’:
h.c:6:3: warning: unknown conversion type character ‘0’ in format [-Wformat]


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