linux-kernel - Re: [PATCH v2 next 04/11] tools/nolibc/printf: Output pad characters in 16 byte chunks

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Message-ID: <20260207234305.508019e5@pumpkin>
Date: Sat, 7 Feb 2026 23:43:05 +0000
From: David Laight <david.laight.linux@...il.com>
To: Willy Tarreau <w@....eu>
Cc: Thomas Weißschuh <linux@...ssschuh.net>,
 linux-kernel@...r.kernel.org, Cheng Li <lechain@...il.com>
Subject: Re: [PATCH v2 next 04/11] tools/nolibc/printf: Output pad
 characters in 16 byte chunks

On Sat, 7 Feb 2026 20:38:36 +0100
Willy Tarreau <w@....eu> wrote:

> On Fri, Feb 06, 2026 at 07:11:14PM +0000, david.laight.linux@...il.com wrote:
> > From: David Laight <david.laight.linux@...il.com>
> > 
> > Simple to do and saves calls to the callback function.  
> 
> +20 bytes here but OK for me.

I think some of those come back when I change all the variables to 'int'.
Some, but not all, is because width is 32bit but len is 64bit.
The final change that did:
	width -= len;
	...
	while (width > 0)
saved a surprising amount provided the ... contained some code.
Breath on the code (or compiler version) and you easily get +/-60 bytes.

	David

> 
> > Signed-off-by: David Laight <david.laight.linux@...il.com>  
> 
> Acked-by: Willy Tarreau <w@....eu>
> 
> > ---
> > 
> > Changes for v2:
> > Formally patch 3, unchanged.
> > 
> >  tools/include/nolibc/stdio.h | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h
> > index 552f09d51d82..c044a6b3babe 100644
> > --- a/tools/include/nolibc/stdio.h
> > +++ b/tools/include/nolibc/stdio.h
> > @@ -355,10 +355,12 @@ int __nolibc_printf(__nolibc_printf_cb cb, void *state, const char *fmt, va_list
> >  			outstr = fmt;
> >  			len = ofs - 1;
> >  		flush_str:
> > -			while (width-- > len) {
> > -				if (cb(state, " ", 1) != 0)
> > +			while (width > len) {
> > +				unsigned int pad_len = ((width - len - 1) & 15) + 1;
> > +				width -= pad_len;
> > +				written += pad_len;
> > +				if (cb(state, "                ", pad_len) != 0)
> >  					return -1;
> > -				written += 1;
> >  			}
> >  			if (cb(state, outstr, len) != 0)
> >  				return -1;  
> 
> Willy