Date: Mon, 01 Jun 1998 11:49:30 -0700 From: Mike Smith <mike@smith.net.au> To: Joerg Schilling <schilling@fokus.gmd.de> Cc: mike@smith.net.au, freebsd-current@FreeBSD.ORG Subject: Re: cdrecord trouble on currnet Message-ID: <199806011849.LAA00742@dingo.cdrom.com> In-Reply-To: Your message of "Mon, 01 Jun 1998 18:30:15 %2B0200." <199806011630.SAA17075@sherwood.gmd.de>
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> >From mike@antipodes.cdrom.com Mon Jun 1 18:17:40 1998
>
> >> You cannot deal with this problem:
> >> =
>
> >> Systems that define _SC_PAGESIZE or _SC_PAGE_SIZE (HP-UX)
> >> don't support getpagesize() so there is no way to fix this
> >> in runtime except if you introduce an additional =
>
> >> =
>
> >> HAVE_GETPAGESIZE
> >> =
>
> >> in the autoconfiguration.
> >> =
>
> >> But even then the code would be badly readable. =
>
> >This is a problem with the design of cdrecord, insofar as it's fairly
>
> Sorry, this is a problem for evryone who wants to write portable code.
> But FreeBSD seems to ignore this issue.
It's not an operating system issue, it's an application issue.
Obtaining the page size is something that needs to be abstracted out of
the application's space into the operating system interface for the
application, simply because it's something that's traditionally
platform-specific.
In your case, you would probably want a vector mechanism, eg.
struct {
int (* pagesize)();
...
} sysdep;
so then in your application context you say:
pagesize = sysdep.pagesize();
and in the BSD layer you would say:
int
bsd_pagesize(void)
{
int pagesize;
if ((pagesize = sysconf(_SC_PAGESIZE)) == -1)
pagesize = getpagesize();
return(pagesize);
}
...
void
appsetup(void)
{
...
sysdep.pagesize = bsd_pagesize;
...
}
This is really basic portability design.
> You may have a functional sysconf(_SC_PAGESIZE) _and_ getpagesize() if you
> like to be able to run portable applications but you cannot have a non
> functional sysconf(_SC_PAGESIZE).
That's an opinion. It's not one that others share. I would be
inclined to say that if you want to call sysconf() at all, you need to
be prepared to handle it properly, and that includes setting/checking
errno when you make the call.
> This looks to me like Microsofts tried to create a Posix environment that
> is Posix compliant on the paper but would prevent you from running real world
> Posix applications on it.
This is more of a commentary on the usefulness of the Posix standard
than anything else.
> I would call a sysconf implementation that is not functional for sysconf(_SC_PAGESIZE)
> although getpagesize() exists buggy.
That's one interpretation. I'd be curious to know whether the
functionality of one given sysconf() argument implies the functionality
of others though.
Peter? Is this something that your reading of the Posix words would
let us get away with? It'd certainly reduce the noise on this one a
little.
--
\\ Sometimes you're ahead, \\ Mike Smith
\\ sometimes you're behind. \\ mike@smith.net.au
\\ The race is long, and in the \\ msmith@freebsd.org
\\ end it's only with yourself. \\ msmith@cdrom.com
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