Messages in this thread | | | Subject | Re: [PATCH] Re: sscanf("-1", "%d", &i) fails, returns 0 | From | Henning Schmiedehausen <> | Date | 11 Nov 2002 10:27:53 +0100 |
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Hi,
On Mon, 2002-11-11 at 04:05, Randy.Dunlap wrote: > On Sun, 10 Nov 2002, Henning P. Schmiedehausen wrote: > > | "Randy.Dunlap" <rddunlap@osdl.org> writes: > | > | >+ digit = *str; > | >+ if (is_sign && digit == '-') > | >+ digit = *(str + 1); > | > | If signed is not allowed and you get a "-", you're in an error case > | again... > > Yes, and a 0 value is returned. > IOW, asking for an unsigned number (in the format string) > and getting "-123" does return 0. > > What should it do?
I would model this after user space. (Which does strange things:
--- cut --- #include <stdio.h>
main() { char *scan = "-100"; unsigned int foo; int bar;
int res = sscanf(scan, "%ud", &foo);
printf("%s = %ud = %d\n", scan, foo, res);
res = sscanf(scan, "%ud", &bar);
printf("%s = %d = %d\n", scan, bar, res);
} --- cut ---
% gcc -o xxx xxx.c ./xxx -100 = 4294967196d = 1 -100 = -100 = 1
Hm, so I guess, yes, a warning message would be nice IMHO. Returning an error code would IMHO moot, because noone is checking these codes anyway.
Regards Henning
> This function can't return -EINPUTERROR or -EILSEQ. > (since it's after feature-freeze :) > And the original problem was that a leading '-' sign on a > signed number (!) caused a return of 0. At least that is fixed. > > So now the problem (?) is that a '-' sign on an unsigned number > returns 0. We can always add a big printk() there that > something is foul. Other ideas?
-- Dipl.-Inf. (Univ.) Henning P. Schmiedehausen -- Geschaeftsfuehrer INTERMETA - Gesellschaft fuer Mehrwertdienste mbH hps@intermeta.de
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