Date: Sat, 10 Oct 2009 14:11:07 -0400 From: Alex Goncharov <alex-goncharov@comcast.net> To: Dag-Erling Smørgrav <des@des.no> Cc: freebsd-hackers@freebsd.org, stef@memberwebs.com, simon@FreeBSD.org Subject: Re: Is the FreeBSD ABI compatibility policy documented anywhere Message-ID: <E1MwgPL-000Neg-W2@daland.home> In-Reply-To: <86d44vp415.fsf@ds4.des.no> (message from Dag-Erling Smørgrav on Sat, 10 Oct 2009 19:11:50 %2B0200) References: <4ABBD5FA.5070507@memberwebs.com> <20091010142758.GB1225@arthur.nitro.dk> <86d44vp415.fsf@ds4.des.no>
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,--- You/Dag-Erling (Sat, 10 Oct 2009 19:11:50 +0200) ----*
| "Simon L. Nielsen" <simon@FreeBSD.org> writes:
| > It's not entirely that simple. The ABI on a stable branch like 7.x
| > should be backward compatible, but there isn't a guarantee of forward
| > compatibility. IE, 7.0 binary should be able to run on 7.x, but a 7.2
| > binary might not run on 7.0. It should be more or less the same with
| > the API's.
|
| Correct, but we're getting closer to that now that we have symbol
| versioning - although we won't reach 100% until we have versioned
| symbols in *all* libraries, which is currently not the case. Even then,
| a developer might break the ABI by mistake, but hopefully we'd catch
| that before it made it into a release.
It's important to note that symbol compatibility is not the whole
thing -- the behaviour on exceptions may be equally important to some
applications. E.g. CMUCL code has to handle different ways to notify
of memory protection failures this way:
#if __FreeBSD_version < 700004
#define PROTECTION_VIOLATION_SIGNAL SIGBUS
#define PROTECTION_VIOLATION_CODE BUS_PAGE_FAULT
#else
#define PROTECTION_VIOLATION_SIGNAL SIGSEGV
#define PROTECTION_VIOLATION_CODE SEGV_ACCERR
#endif
A CMUCL binary built on a pre-7.1 (?) release of FreeBSD, will crash
almost immediately when run on 7.1 (well, "if memory serves").
-- Alex -- alex-goncharov@comcast.net --
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