RE: Use of '%#02x' is almost always wrong

[David Laight]

From: Joe Perches
> Sent: 10 October 2021 17:46
> 
> Perhaps too many developers do not know that using '%#<width>x'
> in printf output _includes_ the 0x prefix in the output width.
> 
> So %#02x already has the width taken by the 0x prefix and will
> always emit 3 or more output bytes.
> 
> sprintf(buf, "%#02x", 1) emits 0x1 (3 bytes of output)
> sprintf(buf, "%#02x", 255) emits 0xff (4 bytes of output)
> 
> So presumably all the uses of %#02x in the kernel are not outputting
> what is actually expected.  Perhaps all of these should use %#04x.

Doesn't help. The definition of "%#x" is completely broken.
Basically 0 doesn't get the "0x" prefix, so "%#04x" outputs
"0000" if the value is zero.
So the correct replacement is (probably) "0x%02x".

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)