Date: Sat, 15 Nov 2003 07:04:04 -0600 From: Jacques Vidrine <nectar@freebsd.org> To: Bruce Evans <bde@zeta.org.au> Cc: freebsd-arch@FreeBSD.org Subject: Re: __TIME_MIN/__TIME_MAX Message-ID: <3FB62444.9000102@freebsd.org> In-Reply-To: <20031115190419.G1478@gamplex.bde.org> References: <20031114194119.GA94198@madman.celabo.org> <20031115114906.L11453@gamplex.bde.org> <3FB5B258.6010207@freebsd.org> <20031115190419.G1478@gamplex.bde.org>
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Bruce Evans said the following on 11/15/03 2:17 AM: > On Fri, 14 Nov 2003, Jacques Vidrine wrote: >> So this kind of thing OK? >> >> long n; >> time_t t; >> errno = 0; >> n = strtoul(...); >> if (errno == ERANGE || (long)(t = n) != n) >> /* out of range */; > > > Not quite like that. strtoul() returns an unsigned long whose value may > be lost by assigning it to a plain long. Mixtures of signed and unsigned > types are tricky to handle as usual. Suppose we make n unsigned long > and it has value ULONG_MAX, and time_t is long, then (t = n) == n, > but t doesn't actually represent n (casting (t = n) to long or unsigned > long doesn't help). So it seems to be necessary to be aware that time_t > is signed and either use strtol() initially or check that t >= 0 if > n is unsigned long. If time_t is actually signed then we may get a GCC > warning for this check... Doh, sorry, that's a typo. I meant strtol (which is what is currently used in the relevant portion of libc--- strptime.c, BTW). Negative values must be allowed here. Cheers, -- Jacques Vidrine NTT/Verio SME FreeBSD UNIX Heimdal nectar@celabo.org jvidrine@verio.net nectar@freebsd.org nectar@kth.se
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