Date: Sat, 15 Jan 2011 17:27:42 +1100 (EST) From: Bruce Evans <brde@optusnet.com.au> To: Garrett Cooper <gcooper@freebsd.org> Cc: svn-src-head@freebsd.org, mdf@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Bruce Evans <brde@optusnet.com.au> Subject: Re: svn commit: r217369 - in head/sys: cam/scsi sys Message-ID: <20110115170529.T16715@besplex.bde.org> In-Reply-To: <AANLkTi=B5mZCJ_bhe=Gf1pLUmWsTswi3O3U2ZLnHMODV@mail.gmail.com> References: <201101131820.p0DIKXip059402@svn.freebsd.org> <AANLkTinh619WaGgq=5fFxTvEX0JPir34k8xb%2Bs6oSH8Y@mail.gmail.com> <20110114174719.D28159@besplex.bde.org> <AANLkTikVwuSO3h8tKeYXCvC6zqYVHVxdY5Abrzo-Ks2R@mail.gmail.com> <20110115133929.D16210@besplex.bde.org> <AANLkTi=B5mZCJ_bhe=Gf1pLUmWsTswi3O3U2ZLnHMODV@mail.gmail.com>
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This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --0-2066649743-1295072862=:16715 Content-Type: TEXT/PLAIN; charset=X-UNKNOWN; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE On Fri, 14 Jan 2011, Garrett Cooper wrote: > On Fri, Jan 14, 2011 at 6:42 PM, Bruce Evans <brde@optusnet.com.au> wrote= : >> On Fri, 14 Jan 2011 mdf@FreeBSD.org wrote: >> >>> On Thu, Jan 13, 2011 at 10:50 PM, Bruce Evans <brde@optusnet.com.au> >>> wrote: >>>> >>>> On Thu, 13 Jan 2011 mdf@freebsd.org wrote: >>>> >>>>> There appear to be 330 uses of SYSCTL and QUAD on the same line in >>>>> CURRENT. =A0This seems reasonable to change them to S64, U64 and X64 = so >>>>> they correctly reflect the size they operate upon. >>>>> >>>>> What do y'all think? >>>> >>>> Now I suggest delaying this until they can be renamed to a type- gener= ic >>>> SYSCTL_INT() (would probably need to be spelled differently, SYSCTL_I(= ) >>>> say, even if SYSCTL_INT() was changed at the same time). >>> >>> I'm torn on this one. =A0The compiler knows the type (unless, for >>> SYSCTL_INT, NULL/0 is used, but that is also a compile-time check), >>> but to interpret it requires the use of __builtin_foo which is a gcc >>> extension and not part of standard C. >>> >>> Philosophically, while I like this kind of letting the compiler do the >>> work, if you want C++ you know where to find it. >> >> Oops. =A0I think sizeof() and issigned() can be used to determine the ty= pe >> well enough in functions and initialized data (do a fuller type check if >> the compiler supports it), but I don't know how to do this in static >> sysctl declarations (since sizeof() can't be used in cpp expressions). > > Why not just create some dumb testcases that can be run at build > time to determine that for you? Well, how? You are given SYSCTL_I(&var, ...) and have to convert this to what is now in SYSCTL_INT(), using only the type of var, in hundreds or thousands of files. I don't even know how to do this with a test case for each file, short of parsing all the files. Oops, I do know how to translate from sizeof(var) to CTLTYPE_INT or CTLTYPE_UINT. That's just (sizeof(var) =3D=3D sizeof(int) ? CTLTYPE_INT : ...). The signness is harder (might need gnu typeof(), but not the recent type checking attributes). This won't convert from SYSCTL_I() existing SYSCTL_INT() (the switch on the size would have to be in an ifdef for that, but sizeof() doesn't work in ifdefs), but it works for generating CTLTYPE_* internally SYSCTL_I(). The difficulty is converting from a bare variable `var' to an integer representing the signedness of its type, without using an unportability like typeof(). With typeof(), this is: =09/* Only works for arithmetic types: */ =09#define=09isinteger(var)=09((typeof(var))0.1 =3D=3D 0) =09#define=09issigned(var)=09((typeof(var))-1 < 0) =09... Bruce --0-2066649743-1295072862=:16715--
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