linux-kernel - Re: linux-next: build failure after merge of the vfs tree

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Date:   Wed, 19 Sep 2018 09:17:03 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     David Howells <dhowells@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linux-Next <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: linux-next: build failure after merge of the vfs tree

On Wed, Sep 19, 2018 at 1:50 AM Stephen Rothwell <sfr@...b.auug.org.au> wrote:
> On Tue, 18 Sep 2018 23:17:21 +0100 David Howells <dhowells@...hat.com> wrote:
> > Stephen Rothwell <sfr@...b.auug.org.au> wrote:
> > > > After merging the vfs tree, today's linux-next build (powerpc
> > > > allyesconfig) failed like this:
> > > >
> > > > samples/vfs/test-fsinfo.c: In function 'fsinfo':
> > > > samples/vfs/test-fsinfo.c:37:17: error: '__NR_fsinfo' undeclared (first use in this function); did you mean 'fsinfo'?
> >
> > I think the problem is that I haven't allocated system call numbers for any
> > arches other than x86 - even the x86 syscall numbers are provisional until the
> > patchset is taken upstream.  I'm not sure of the best way to deal with this -
> > make the samples dependent on the X86 arch?
>
> But the sample programs are built with HOSTCC, so you can't depend on
> ARCH (since I, for one, am cross compiling).  Maybe SUBARCH.  Better
> would be to use either Kconfig's shell primitive or some make magic to
> figure out if the syscall number define's are defined.
>
> > > > samples/vfs/test-fsinfo.c:180:30: warning: format '%llx' expects argument of type 'long long unsigned int', but argument 2 has type '__u64' {aka 'long unsigned int'} [-Wformat=]
> > > >   printf("\tmax file size: %llx\n", f->max_file_size);
> >
> > Sigh.  On powerpc __u64 is unsigned long, but on x86_64 it's unsigned long
> > long.  Is it possible to shift all arches to use unsigned long long for __u64?
>
> I doubt it - that would probably cause more warnings in the arch code.

In kernelspace, it's unsigned long long on all architectures.
In userspace, it may still be unsigned long on early 64-bit architectures.

> Instead, just explicitly cast it to unsigned long long.

Or use C99's PRIx64?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds