Date: Tue, 22 Nov 2011 08:24:07 -0500 From: John Baldwin <jhb@freebsd.org> To: freebsd-arch@freebsd.org Cc: Kostik Belousov <kostikbel@gmail.com>, Robert Millan <rmh@debian.org>, freebsd-current@freebsd.org, Adrian Chadd <adrian@freebsd.org> Subject: Re: [PATCH] Detect GNU/kFreeBSD in user-visible kernel headers Message-ID: <201111220824.07823.jhb@freebsd.org> In-Reply-To: <CAOfDtXNypUhu-dWznLyHcZMN-ZPSn_qTC6pSuL68r2M2hOjZTg@mail.gmail.com> References: <CAOfDtXPX1Rv9T7%2B1jYQbkM14tRY7mqgCzPcUqvHxFaRObbwvEg@mail.gmail.com> <20111121092749.GD50300@deviant.kiev.zoral.com.ua> <CAOfDtXNypUhu-dWznLyHcZMN-ZPSn_qTC6pSuL68r2M2hOjZTg@mail.gmail.com>
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On Monday, November 21, 2011 12:39:26 pm Robert Millan wrote: > (replying with Debian hat this time) > > 2011/11/21 Kostik Belousov <kostikbel@gmail.com>: > > There are some implementations that > > use FreeBSD kernel, and which could potentially benefit from providing > > its own value for __FreeBSD_kernel. > > Actually, we wouldn't be able to provide a different value for the > macro (whatever its name). Our compiler simply doesn't know which > version of the kernel it is building for. Only the headers do, but if > we define it in the headers we'd just use the FreeBSD definitions. > > Our compiler defines __FreeBSD_kernel__ as an empty macro, I don't > expect this will change because unlike with FreeBSD, on Debian there > are strong technical limitations to making it a number. > > If __FreeBSD_kernel__ is to be defined in FreeBSD land, may I suggest > that it is defined as an empty macro as well? This covers the vast > majority of cases (e.g. like the ones in my initial patch which > started this discussion), and it doesn't preclude the possibility that > this macro becomes a number without breaking backward compatibility. > > OTOH once you define it as a number, it becomes relevant whether you > did it with #ifndef or with #undef, and so you have to commit to it. > > Just to make it clear: It's no problem to me if it's defined as a > number, but it doesn't help much either. At least from Debian POV it's > not worth making a big argument about. It could be a good idea from > FreeBSD POV, but please only do this if it's useful to FreeBSD. Is __FreeBSD_version defined if __FreeBSD_kernel__ is defined on kFreeBSD? Most things that want to check versions that I've seen do something like this: #ifdef __FreeBSD__ #include <sys/param.h> #if __FreeBSD_version > XXXXXXX /* use new feature */ #endif #endif If __FreeBSD_version is defined when __FreeBSD_kernel__ is defined, then I think having it be empty would be ok as it would allow usage as above. Also, in that case I think __FreeBSD_kernel__ is much closer in meaning to __FreeBSD__ than to __FreeBSD_version. -- John Baldwin
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