Date: Mon, 19 Nov 2012 10:44:00 -0800 From: mdf@FreeBSD.org To: Navdeep Parhar <np@freebsd.org> Cc: Gleb Smirnoff <glebius@freebsd.org>, Andre Oppermann <andre@freebsd.org>, src-committers@freebsd.org, svn-src-user@freebsd.org Subject: Re: svn commit: r243215 - user/andre/tcp_workqueue/sys/sys Message-ID: <CAMBSHm-RUKkm%2BsaLMA9xwrB-L3Hauiy2SHf-Z3RoFMyX6S-ysA@mail.gmail.com> In-Reply-To: <50AA7773.1050401@FreeBSD.org> References: <201211181217.qAICH7aH021497@svn.freebsd.org> <20121119114510.GQ38060@FreeBSD.org> <50AA3529.2030300@freebsd.org> <CAMBSHm_eu-z6fuxTL2bdavQeBjOcE1zvS5h4itGa%2BP%2BiQhqrrA@mail.gmail.com> <50AA76CD.3070904@freebsd.org> <50AA7773.1050401@FreeBSD.org>
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On Mon, Nov 19, 2012 at 10:16 AM, Navdeep Parhar <np@freebsd.org> wrote: > On 11/19/12 10:13, Andre Oppermann wrote: >> On 19.11.2012 18:01, mdf@FreeBSD.org wrote: >>> On Mon, Nov 19, 2012 at 5:33 AM, Andre Oppermann <andre@freebsd.org> >>> wrote: >>>> On 19.11.2012 12:45, Gleb Smirnoff wrote: >>>>> >>>>> On Sun, Nov 18, 2012 at 12:17:07PM +0000, Andre Oppermann wrote: >>>>> A> Author: andre >>>>> A> Date: Sun Nov 18 12:17:07 2012 >>>>> A> New Revision: 243215 >>>>> A> URL: http://svnweb.freebsd.org/changeset/base/243215 >>>>> A> >>>>> A> Log: >>>>> A> Add mtodo(m, o, t) macro taking an additional offset into >>>>> A> the mbuf data section before the casting to type 't'. >>>>> >>>>> IMHO, argument order of (m, t, o) is more intuitive, since >>>>> matches order of mtod(). >>>> >>>> >>>> Yes, but that looks rather horrible and counter-intuitive: >>>> >>>> th = mtodo(m, struct tcphdr *, 20); >>>> >>>> vs. >>>> >>>> th = mtodo(m, 20, struct tcphdr *); >>>> >>>> Reads m->m_data at offset 20 is struct tcphdr. >>>> >>>> Naming it mtood() wasn't convincing either. ;-) >>> >>> Why a cast at all? Perpetuating the mistake of mtod()'s casting isn't >>> necessary. mtod() can't be fixed for source reasons, but the new one >>> doesn't need to cast. Since C automatically casts from void * to any >>> other pointer, the code gets shorter (usually) too: >>> >>> th = mtodo(m, 20); >> >> m->m_data is caddr_t which is "char *" > > No matter what it is you can always cast it to void * before returning, > instead of having the caller supply the type. Right, this is what I meant. Instead of a parameter to cast to, just return void *. Let the caller cast, or not, as needed. It's a simpler macro that way. Cheers, matthew
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