Date: Thu, 17 Nov 2011 20:02:02 +0100 From: Robert Millan <rmh@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: Kostik Belousov <kostikbel@gmail.com>, Adrian Chadd <adrian@freebsd.org>, freebsd-current@freebsd.org, freebsd-arch@freebsd.org Subject: Re: [PATCH] Detect GNU/kFreeBSD in user-visible kernel headers Message-ID: <CAOfDtXNy8r5ww5xSwhH-4w7daWdzB0KsVbO75JAOT=-Wzi%2BdHw@mail.gmail.com> In-Reply-To: <201111170959.56767.jhb@freebsd.org> References: <CAOfDtXPX1Rv9T7%2B1jYQbkM14tRY7mqgCzPcUqvHxFaRObbwvEg@mail.gmail.com> <B188597B-4446-4EAB-A9BD-D9EBBEB8B1D7@bsdimp.com> <CAOfDtXMsmDa2XaZ0qmMKZxF5xagotw5EwaU=7y_GUxKLhaJ9OQ@mail.gmail.com> <201111170959.56767.jhb@freebsd.org>
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[-- Attachment #1 --] 2011/11/17 John Baldwin <jhb@freebsd.org>: > I recall the discussion from earlier. I can't recall if I had replied to it > though. :-/ In my current opinion, I think it would be fine to define > __FreeBSD_kernel__ on FreeBSD and to do it in <sys/param.h> for now until all > the compilers we use have been updated to define it automatically (which may > be a long time). I think it will also be fine to patch in-system headers to > use __FreeBSD_kernel__ once <sys/param.h> is defined. Unfortunately headers > in 3rd party software are going to have to check for both __FreeBSD__ and > __FreeBSD_kernel__ to support both GNU/kFreeBSD and older FreeBSD for the > foreseeable future. I think that is fine, but that the sooner we add > __FreeBSD_kernel__ on FreeBSD the sooner we get the clock started for a day > when those extra checks can go away. I would also be fine with MFC'ing the > addition of __FreeBSD_kernel__ to older branches (at least 7 - 9) as well. Well, here's a patch then. I wrote a comment in it trying to explain the situation. Please let me know what you think. [-- Attachment #2 --] Index: sys/sys/param.h =================================================================== --- sys/sys/param.h (revision 227580) +++ sys/sys/param.h (working copy) @@ -60,6 +60,23 @@ #undef __FreeBSD_version #define __FreeBSD_version 1000001 /* Master, propagated to newvers */ +/* + * __FreeBSD_kernel__ indicates that this system uses the kernel of FreeBSD, + * which by definition is always true on FreeBSD :-). This macro may also + * be defined on other systems that use the kernel of FreeBSD, such as + * GNU/kFreeBSD. + * + * It is tempting to use this macro in userland code when we want to enable + * kernel-specific routines, and in fact it's fine to do this in code that + * is part of FreeBSD itself. However, be aware that as presence of this + * macro is still not widespread (e.g. older FreeBSD versions, 3rd party + * compilers, etc), it is STRONGLY DISCOURAGED to check for this macro in + * external applications without also checking for __FreeBSD__ as an + * alternative. + */ +#undef __FreeBSD_kernel__ +#define __FreeBSD_kernel__ __FreeBSD__ + #ifdef _KERNEL #define P_OSREL_SIGWAIT 700000 #define P_OSREL_SIGSEGV 700004
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