Re: error in hh length modifier when used with sscanf

CBFalconer <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> Bill Bennett wrote:
> > "CBFalconer" <[EMAIL PROTECTED]> wrote in message
> > > Bill Bennett wrote:
> > > >
> > > > unsigned char buffer[] = "$$$$$$$$";
> > > > for (int i=0; i<8; i++) printf("%6x ", buffer[i]); printf("\n");
> > > > sscanf("55", "%hhx", buffer+2);
> > > > for (int i=0; i<8; i++) printf("%6x ", buffer[i]); printf("\n");
> > > >
> > > > I expect
> > > >     24     24     24     24     24     24     24     24
> > > >     24     24     55     24     24     24     24     24
> > > > but I get
> > > >     24     24     24     24     24     24     24     24
> > > >     24     24     55       0       0       0     24     24
> > > >
> > > > In other words, I expected one byte to be stored but instead 4
> > > > are stored, trampling adjacent bytes.
> > > >
> > > > Using %hx instead of %hhx has the correct result, only 2 bytes
> > > > are stored.
> > > >
> > > > Seems like an error in how the hh is handled, right?
> > >
> > > WRONG.  You got what you asked for.  Look up the meaning of hh in
> > > C99 (it is new since C90).  You are lucky you didn't get some sort
> > > of bus alignment violation, so it would appear you are using
> > > something x86 based, with sizeof(int) == 4 and sizeof(short) == 2
> > > that stores integers low byte first.
...
> > In the ISO/IEC 9899 C spec it says specifically for fscanf:
> > 
> > hh   Specifies that a following d , i , o , u , x , X , or n conversion
> > specifier applies to an argument with type pointer to signed char or
> > unsigned char.
> 
> There appears to be a conflict here between N869 and the summaries
> on <http://www.dinkumware.com>.  This may be an error in N869 that
> has been revised in the actual standard.  The proper place to
> thrash this out is on comp.lang.c and comp.std.c.  followups and
> cross-posts set.

As far as I can see, both n869.pdf and the final standard say the same
thing, that "%hhx" is for reading in a single unsigned char in
hexadecimal format. How are you reading them to allow four bytes to
get trashed?