Re: [avr-libc-dev] Implementing the vprintf "%*s" and "%.*s" formats

[David Brown]

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It seems reasonable to me.  It is probably not a heavily used feature
in printf, but it is part of the standards and its absence could be
surprising to people.

David


On 17/10/17 22:10, Paul "LeoNerd" Evans wrote:
> I often find it useful to be able to print a character buffer of 
> dynamically-known size by using some variant on
> 
> printf("%.*s", len, buf);
> 
> It appears to me that avr-libc doesn't recognise this particular
> flag. It is documented that
> 
> The variable width or precision field (an asterisk * symbol) is
> not realized and will to abort the output.
> 
> But it's unclear from this whether the absence is deliberate, or
> simply not implemented yet.
> 
> Would folk be amenable to a patch to add this feature? I have an 
> (as-yet untested) attempt at it it. I don't think it would
> massively increase code size, and it doesn't consume any more RAM
> at runtime.
> 
> But I thought I'd ask, in case there's some specific reason for
> its absence.
> 
> -----
> 
> === modified file 'libc/stdio/vfprintf.c' --- libc/stdio/vfprintf.c
> 2017-10-17 19:56:22 +0000 +++ libc/stdio/vfprintf.c   2017-10-17
> 19:57:23 +0000 @@ -344,6 +344,12 @@ flags |= FL_WIDTH; continue; } 
> +             if (c == '*') { +                   if (flags & FL_PREC) +      
>                 prec =
> va_arg(ap, int); +                else +                      width = 
> va_arg(ap, int); +              } if
> (c == '.') { if (flags & FL_PREC) goto ret;
> 
> 
> 
> 
> _______________________________________________ AVR-libc-dev
> mailing list address@hidden 
> https://lists.nongnu.org/mailman/listinfo/avr-libc-dev
> 

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