On 12 July 2011 13:40, Dave Martin <dave.mar...@linaro.org> wrote: > On Tue, Jul 12, 2011 at 01:10:24PM +0100, David Gilbert wrote:
>> Does it help address rth's concerns though? > > Which ones in particular? Good question - hence my prompt to rth at the bottom; I know he originally asked why not go to VDSO, so what I don't yet understand is whether he would accept the other alternatives. >> Isn't this a bit over-the-top for the failure we're trying to catch? > > Yes and no. Implementing such a solution just for this case would be very > over-the-top. But integrating with a general mechanism for reporting errors > if it exists (now or in the future) is very sensible. Right - but I don't think we should be doing anything new here; we can't be the first people to be trying to detect running on an older kernel and exiting relatively cleanly. > If it's necessary to to any check at all before concluding that it's safe > to call a function, I don't see the difference. Checking a magic number > in one place seems no better than checking for a version number in another > place, AFAICT. Something like AUXV would have seemed cleaner to me; but that's just preference. > Having a faulting instruction doesn't permit the program to abort cleanly > ahead of time (unless you check in advance -- in which case you're really > back to a magic number again). > > This matters if constructors might do things like screwing up the terminal -- > if so, the chance to un-screw thing up should be offered to the program before > it exits. > > Possibly constructors should never do things like that, in which case these > concerns don't apply. I don't know what the official line is regarding > what kind of things global constructors should and shouldn't do. If I understand correctly that's the whole point of abort() - if they need to tidy up then they should be handling SIGABRT. >> Also, remember this whole discussion is just to print a message and exit >> nicely >> in the case of someone using a currently incredibly rare function on an old >> kernel! > > I'd say we want to notify the operating environment and/or the user. This > may be realised by writing some text to stderr, but that's not useful in > the context of GUI environments. Yes it is; exiting with a non-zero return value and writing to stderr is perfectly normal - whatever launched it can go and display that text. (Or as I say trapping SIGABRT). > I am not suggesting that we should engineer a special solution to that > problem here, so long as we don't defeat potential solutions either. > For now, it doesn't like any of the proposals risk that though. Dave _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
