Date: Tue, 31 Jul 2001 08:45:18 -0700 (PDT) From: John Baldwin <jhb@FreeBSD.org> To: "David O'Brien" <obrien@FreeBSD.org> Cc: cvs-all@FreeBSD.org, cvs-committers@FreeBSD.org, Garrett Wollman <wollman@khavrinen.lcs.mit.edu> Subject: Re: cvs commit: src/usr.sbin/newsyslog Makefile newsyslog.c Message-ID: <XFMail.010731084518.jhb@FreeBSD.org> In-Reply-To: <20010730163112.A83693@dragon.nuxi.com>
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On 30-Jul-01 David O'Brien wrote:
> On Mon, Jul 30, 2001 at 11:20:17AM -0700, John Baldwin wrote:
>> > It looks like someone cut-and-pasted my canonical `parse an integer
>> > correctly' code into a new function where the results were not used
>> > carefully. It would be an error to use `strtol' to parse a number
>> > which is not supposed to be negative.
> ...
>> Not to mention, the code in question doesn't check to see if strtoul()
>> failed (it doesnt' check to see what the 't' var points to) which it
>> would do for a negative number, yes?
>
> It does check. strtoul() is documented to return INT_MAX and set errno
> in the negative input case. The code exits if the value from strtoul()
> is > N (where N is a very small number). Thus the return value from
> strtoul() is checked for validity. A problem with negative input is not
> distinguished between invalid positive input.
Incorrect:
The strtoul() function returns either the result of the conversion or, if
there was a leading minus sign, the negation of the result of the conver-
sion, unless the original (non-negated) value would overflow; in the lat-
ter case, strtoul() returns ULONG_MAX.
It only returns ULONG_MAX if the original value would overflow.
strtoul() of '-4' will return -4:
const char *s = "-4";
int
main()
{
int x;
x = strtoul(s, NULL, 0);
printf("s = \"%s\", x = %d\n", s, x);
return 0;
}
s = "-4", x = -4
Granted, when x is unsigned, you get:
s = "-4", x = 4294967292
Which will be large enough for the cases assumed here.
Does go to show that strtol() wouldn't fail in the negative case however as I
thought. Hmm. This means that you probably could just have done
s/strtoul/strtol/ to get rid of the warning. :)
--
John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
"Power Users Use the Power to Serve!" - http://www.FreeBSD.org/
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