Re: [PATCH] Enable '-Werror' by default for all kernel builds

[Christian König]

Am 07.09.21 um 07:32 schrieb Huang Rui:
> On Tue, Sep 07, 2021 at 07:06:04AM +0800, Linus Torvalds wrote:
> > [ Adding some subsystem maintainers ]
> >
> > On Mon, Sep 6, 2021 at 10:06 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > > > But hopefully most cases are just "people haven't cared enough" and
> > > > easily fixed.
> > > We'll see. For my testbed I disabled the new configuration flag
> > > for the time being because its primary focus is boot tests, and
> > > there won't be any boot tests if images fail to build.
> > Sure, reasonable.
> >
> > I've checked a few of the build errors by doing the appropriate cross
> > compiles, and it doesn't seem bad - but it does seem like we have a
> > number of really pointless long-standing warnings that should have
> > been fixed long ago.
> >
> > For example, looking at sparc64, there are several build errors due to
> > those warnings now being fatal:
> >
> >   - drivers/gpu/drm/ttm/ttm_pool.c:386
> >
> >     This is a type mismatch error. It looks like __fls() on sparc64
> > returns 'int'. And the ttm_pool.c code assumes it returns 'unsigned
> > long'.
> >
> >     Oddly enough, the very line after that line does "min_t(unsigned
> > int" to get the types in line.
> >
> >     So  the immediate reason is "sparc64 is different". But the deeper
> > reason seems to be that ttm_pool.c has odd type assumptions. But that
> > warning should have been fixed long ago, either way.
> >
> >     Christian/Huang? I get the feeling that both lines in that file
> > should use the min_t(). Hmm?
>
> Shall we align the return type like __fls() on all the arches?

I think so, yes. IIRC I was a bit surprised that it returns UL on x86. I 
mean the maximum possible value here is 63.

> But it looks OK for me to change min to min_t() here as well, I can file a
> patch to the update:
>
> -       for (order = min(MAX_ORDER - 1UL, __fls(num_pages)); num_pages;
> +       for (order = min_t(unsigned int, MAX_ORDER - 1UL, __fls(num_pages)); num_pages;
>
> Christian, what's your opinion?

The "MAX_ORDER - 1UL" can now be changed to "MAX_ORDER - 1", but apart 
from that looks good to me.

Thanks,
Christian.

> Thanks,
> Ray
>
> >   - drivers/input/joystick/analog.c:160
> >
> >     #warning Precise timer not defined for this architecture.
> >
> >     Unfortunate. I suspect that warning just has to be removed. It has
> > never caused anything to be fixed, it's old to the point of predating
> > the git history. Dmitry?
> >
> >   - at least a couple of stringop-overread errors. Attached is a
> > possible for for one of them.
> >
> > The stringop overread is odd, because another one of them is
> >
> >     fs/qnx4/dir.c: In function ‘qnx4_readdir’:
> >     fs/qnx4/dir.c:51:32: error: ‘strnlen’ specified bound 48 exceeds
> > source size 16 [-Werror=stringop-overread]
> >        51 |                         size = strnlen(de->di_fname, size);
> >           |                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > but I'm not seeing why that one happens on sparc64, but not on arm64
> > or x86-64. There doesn't seem to be anything architecture-specific
> > anywhere in that area.
> >
> > Funky.
> >
> > Davem - attached patch compiles cleanly for me, but I'm not sure it's
> > necessarily the right thing to do, and I didn't check the code
> > generation. Maybe it screws up. Can somebody test on sparc64 and
> > perhaps think about it more than I did?
> >
> >                 Linus
> >   arch/sparc/kernel/mdesc.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/sparc/kernel/mdesc.c b/arch/sparc/kernel/mdesc.c
> > index 8e645ddac58e..30f171b7b00c 100644
> > --- a/arch/sparc/kernel/mdesc.c
> > +++ b/arch/sparc/kernel/mdesc.c
> > @@ -39,6 +39,7 @@ struct mdesc_hdr {
> >   	u32	node_sz; /* node block size */
> >   	u32	name_sz; /* name block size */
> >   	u32	data_sz; /* data block size */
> > +	char	data[];
> >   } __attribute__((aligned(16)));
> >   
> >   struct mdesc_elem {
> > @@ -612,7 +613,7 @@ EXPORT_SYMBOL(mdesc_get_node_info);
> >   
> >   static struct mdesc_elem *node_block(struct mdesc_hdr *mdesc)
> >   {
> > -	return (struct mdesc_elem *) (mdesc + 1);
> > +	return (struct mdesc_elem *) mdesc->data;
> >   }
> >   
> >   static void *name_block(struct mdesc_hdr *mdesc)