Date: Thu, 30 Jun 2011 19:12:43 +0200 From: Stefan Esser <se@freebsd.org> To: Bruce Evans <brde@optusnet.com.au>, Alexander Best <arundel@freebsd.org>, Poul-Henning Kamp <phk@phk.freebsd.dk>, standards@freebsd.org, Bruce Evans <bde@freebsd.org> Subject: Re: RESENT with patch ... Re: [RFC] Consistent numeric range for "expr" on all architectures Message-ID: <4E0CAE8B.6030309@freebsd.org> In-Reply-To: <20110630165050.GB82980@zim.MIT.EDU> References: <99048.1309258976@critter.freebsd.dk> <4E0A0774.3090004@freebsd.org> <20110629082103.O1084@besplex.bde.org> <4E0B1C47.4010201@freebsd.org> <20110630073705.P1117@besplex.bde.org> <4E0C2F41.2060302@freebsd.org> <4E0CA55E.2090102@freebsd.org> <20110630165050.GB82980@zim.MIT.EDU>
next in thread | previous in thread | raw e-mail | index | archive | help
Am 30.06.2011 18:50, schrieb David Schultz:
> On Thu, Jun 30, 2011, Stefan Esser wrote:
>> int
>> +is_integer(const char *s)
>> +{
>> + if (*s == '-')
>> + s++;
>> + while (isdigit(*s))
>> + s++;
>> + return *s == '\0';
>> +}
>
> I only glanced at the patch for a few seconds, but your
> is_integer() routine will accept a bare minus sign ("-") as an
> integer.
I mentioned in the message, that I do not test for empty numeric
operands. I had considered:
int
is_integer(const char *s)
{
if (*s == '-')
s++;
if (!isdigit(*s++)
return 0;
while (isdigit(*s))
s++;
return *s == '\0';
}
But this will break script that do
while :
do
i=`expr "$i" + 1`
done
without first setting i=0. And I assume, such scripts exist in huge numbers.
But "-" will not be accepted as operand (neither integer nor string).
Didn't I give the example "expr -- - : -" which fails with a syntax
error?
Therefore, I do not need to check for actual digits in the input (and
thus may accept "" as 0 for backwards compatibility), but "-" will not
be allowed as parameter to expr by the parser ("syntax error").
Regards, STefan
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4E0CAE8B.6030309>