Messages in this thread | | | Subject | Re: [PATCH] [v2] bcache: hide variable-sized types from uapi header check | From | Coly Li <> | Date | Mon, 18 Oct 2021 22:20:33 +0800 |
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On 9/28/21 4:55 PM, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > The headers_check helper complains about a GNU extension in > one of the exported headers: > > linux/bcache.h:354:2: warning: field '' with variable sized type 'union jset::(anonymous at ./usr/include/linux/bcache.h:354:2)' not at the end of a struct or class is a GNU extension [-Wgnu-variable-sized-type-not-at-end] > BKEY_PADDED(uuid_bucket); > ^ > linux/bcache.h:134:2: note: expanded from macro 'BKEY_PADDED' > union { struct bkey key; __u64 key ## _pad[BKEY_PAD]; } > ^ > > Address this by enclosing the GNU extensions in an #ifdef: Since the > header check is done with --std=c90, this shuts up the warning and makes > it possible to include the header file C90 user space applications, but > allows applications built with --std=gnu89 or higher to use those > parts. > > Another alternative would be to exclude this header from the check, > but the GNU extension check seems more sensible. > > Fixes: 81ab4190ac17 ("bcache: Pull on disk data structures out into a separate header") > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Hi Arnd,
IMHO, remove bcache related header from uapi check might be better solution. So far only bcache-tools uses this header with its own copy, no application includes the header(s) so far. It makes sense to exclude bcache.h from upai headers check.
Thanks.
Coly Li
> --- > v2: use __STRICT_ANSI__ check instead of __KERNEL__. > > I think this version is better than the first, let me know if that > works for you. > --- > include/uapi/linux/bcache.h | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/include/uapi/linux/bcache.h b/include/uapi/linux/bcache.h > index cf7399f03b71..b7901e986193 100644 > --- a/include/uapi/linux/bcache.h > +++ b/include/uapi/linux/bcache.h > @@ -23,9 +23,13 @@ static inline void SET_##name(type *k, __u64 v) \ > struct bkey { > __u64 high; > __u64 low; > +#ifndef __STRICT_ANSI__ > + /* gcc extension not meant for user space */ > __u64 ptr[]; > +#endif > }; > > +#ifndef __STRICT_ANSI__ > #define KEY_FIELD(name, field, offset, size) \ > BITMASK(name, struct bkey, field, offset, size) > > @@ -127,6 +131,8 @@ static inline struct bkey *bkey_idx(const struct bkey *k, unsigned int nr_keys) > > return (struct bkey *) (d + nr_keys); > } > +#endif > + > /* Enough for a key with 6 pointers */ > #define BKEY_PAD 8 >
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