Date: Sat, 20 Oct 2012 20:11:18 -0400 From: Rich Felker <dalias@...ifal.cx> To: musl@...ts.openwall.com Subject: Re: [PATCH 2/4] Add basic sys/cdefs.h found on most unix On Sun, Oct 21, 2012 at 02:13:47AM +0200, Abdoulaye Walsimou GAYE wrote: > On 10/21/2012 01:38 AM, Rich Felker wrote: > >On Sun, Oct 21, 2012 at 01:38:52AM +0200, Abdoulaye Walsimou GAYE wrote: > >>On 10/21/2012 01:18 AM, Isaac Dunham wrote: > >>>On Sat, 20 Oct 2012 22:15:43 +0200 > >>>Abdoulaye Walsimou Gaye <awg@...toolkit.org> wrote: > >>> > >>>>Signed-off-by: Abdoulaye Walsimou Gaye <awg@...toolkit.org> > >>>>--- > >>>> include/sys/cdefs.h | 22 ++++++++++++++++++++++ > >>>> 1 file changed, 22 insertions(+) > >>>> create mode 100644 include/sys/cdefs.h > >>>I'm pretty sure that the last three times sys/cdefs.h was proposed, > >>>it was rejected. > >>Unfortunately many packages (wrongly?) use to rely on macros defined there, > >I've found it's really very few; an equivalent sys/cdefs.h does not > >exist on most systems. It was never intended for use by applications; > >it's an internal part of glibc (and perhaps also some BSDs?) used for > >handling backwardsness like pre-ANSI C compilers (abstracting const > >away as __const, or abstracting away prototypes with __P()) and > >optional use of GCC-specific features. > > But applications borrowed from systems internal and ported to others > systems tend to use these macros (libtirpc, libbsd come in mind). > Major BSD systems have it (FreeBSD, NetBSD, OpenBSD, PCBSD), it not > a reason to have it on linux systems but it helps/simplifies packages porting > from these OS. As it stands, these libraries/apps won't work anywhere but GNU/Linux (by "GNU/" I mean glibc-based) or BSD. If the offending code is removed and replaced with what should be there, they'd be a lot more portable. So I would not say sys/cdefs.h aids in porting them; I'd say its presence gives these libs/apps a way to be lazy and non-portable... > >For things like 'extern "C"', there's no reason to use sys/cdefs.h; > >the just writing the code it expands to inline is much more > >clear/informative and provides better performance as a nice side > >effect. > > > >>sometimes indirectly via <features.h>. > >I don't see what you mean by this. > > some applications use <features.h> to get macros defined in <sys/cdefs.h> > as on glibc, eglibc, uClibc <features.h> have a #include <sys/cdefs.h> Both of these usages are incorrect and could easily be fixed (both are implementation-internal headers). Rich
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