Re: [PATCH v2 next 07/11] tools/nolibc/printf: Add support for conversion flags "#- +" and format "%X"

[David Laight]

On Mon, 16 Feb 2026 20:57:37 +0100
Thomas Weißschuh <linux@xxxxxxxxxxxxxx> wrote:

> On 2026-02-06 19:11:17+0000, david.laight.linux@xxxxxxxxx wrote:
> > From: David Laight <david.laight.linux@xxxxxxxxx>
> > 
> > Add support for all the normal flag chacacters except '0' (zero pad).
> >   '-' left alignment.
> >   '+' and ' ' Sign characters for non-negative numbers.
> >   '#' adds 0x to hex numbers.
> > Partially support "%X", outputs lower case a..f the same as "%x".
> > 
> > Move the "%s" code in with the numeric formats to save a va_arg() call.
> > 
> > Prepend the sign (or "0x") after conversion to ascii and use the length
> > returned by u64toh_r() and u64toa_r().
> > Both needed for precision and zero-padding in the next patch.
> > 
> > Signed-off-by: David Laight <david.laight.linux@xxxxxxxxx>
> > ---
> > 
> > Changes for v2:
> > - Add support for left justifying fields (removed from patch 6).
> > - Merge in the changes from the old patch 8.
> > - Add support for "%#x" (formally part of patch 9).
> > 
> >  tools/include/nolibc/stdio.h | 97 ++++++++++++++++++++++++++----------
> >  1 file changed, 71 insertions(+), 26 deletions(-)  
> 
> (...)
> 
> > +non_numeric_conversion:
> > +			if (ch == 'm') {
> >  #ifdef NOLIBC_IGNORE_ERRNO
> >  				outstr = "unknown error";
> > +				len = __builtin_strlen(outstr);  
> 
> Why the builtin and not the regular one?

In that case the builtin one will generate a compile-time constant.
But that code gets changed in later patches.
The #if belongs in strerror().

	David

> 
> >  #else
> >  				outstr = strerror(errno);
> > +				goto do_strnlen_output;
> >  #endif /* NOLIBC_IGNORE_ERRNO */
> >  			} else {
> >  				if (ch != '%') {  
> 
> (...)