Date: Tue, 20 Sep 2022 17:20:11 +0200 From: Jₑₙₛ Gustedt <jens.gustedt@...ia.fr> To: Rich Felker <dalias@...c.org> Cc: musl@...ts.openwall.com Subject: Re: [PATCH] vfprintf: support C2x %b and %B conversion specifiers Rich, on Tue, 20 Sep 2022 10:46:18 -0400 you (Rich Felker <dalias@...c.org>) wrote: > On Tue, Sep 20, 2022 at 04:27:28PM +0200, Jₑₙₛ Gustedt wrote: > > on Tue, 20 Sep 2022 16:22:36 +0200 you (Jₑₙₛ Gustedt > > <jens.gustedt@...ia.fr>) wrote: > > > > > There is a feature test macro for the maximum width of bit-precise > > > integers, `BITINT_MAXWIDTH`. It is guaranteed to be at least > > > `ULLONG_WIDTH` but can (and will) be larger on many platforms. > > > > e.g on my ubuntu-nothing-fancy machine I get > > > > clang -E -dM -xc /dev/null | grep -i bitint > > #define __BITINT_MAXWIDTH__ 128 > > As I understand it, that gives the application knowledge of what > bit-precise types the compiler can provide to it, but doesn't do > anything to tell the application what wN modifiers printf can be > expected to support. If it were required to support wN for > N==BITINT_MAXWIDTH that would at least be something to go from, but I > see no such requirement and I'm not sure it's desirable (it means you > can't let the compiler offer larger BITINT_MAXWIDTH, but would have to > define it as what libc supports). > > I think a separate macro indicating what printf supports is needed to > solve this problem well. That's an excellent point. It would be good if we filed a national body comment for the ballot period to get such a thing in. Jₑₙₛ -- :: INRIA Nancy Grand Est ::: Camus ::::::: ICube/ICPS ::: :: :::::::::::::::::::::: gsm France : +33 651400183 :: :: ::::::::::::::: gsm international : +49 15737185122 :: :: http://icube-icps.unistra.fr/index.php/Jens_Gustedt :: Content of type "application/pgp-signature" skipped
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