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Date: Thu, 10 Nov 2016 23:54:01 -0500
From: Rich Felker <dalias@...c.org>
To: Felix Janda <felix.janda@...teo.de>, linux-devel@...r.kernel.org,
"David S. Miller" <davem@...emloft.net>, linux-api@...r.kernel.org,
musl@...ts.openwall.com
Subject: Re: [PATCH] uapi libc compat: allow non-glibc to opt out of
uapi definitions
On Thu, Nov 10, 2016 at 08:40:44PM -0500, Felix Janda wrote:
> Currently, libc-compat.h detects inclusion of specific glibc headers,
> and defines corresponding _UAPI_DEF_* macros, which in turn are used in
> uapi headers to prevent definition of conflicting structures/constants.
> There is no such detection for other c libraries, for them the
> _UAPI_DEF_* macros are always defined as 1, and so none of the possibly
> conflicting definitions are suppressed.
>
> This patch enables non-glibc c libraries to request the suppression of
> any specific interface by defining the corresponding _UAPI_DEF_* macro
> as 0.
>
> This patch together with the recent musl libc commit
>
> http://git.musl-libc.org/cgit/musl/commit/?id=04983f2272382af92eb8f8838964ff944fbb8258
>
> fixes the following compiler errors when <linux/in6.h> is included
> after musl <netinet/in.h>:
>
> ../linux/in6.h:32:8: error: redefinition of 'struct in6_addr'
> ../linux/in6.h:49:8: error: redefinition of 'struct sockaddr_in6'
> ../linux/in6.h:59:8: error: redefinition of 'struct ipv6_mreq'
>
> Signed-off-by: Felix Janda <felix.janda@...teo.de>
Acked-by: Rich Felker <dalias@...c.org>
> ---
> include/uapi/linux/libc-compat.h | 52 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 52 insertions(+)
>
> diff --git a/include/uapi/linux/libc-compat.h b/include/uapi/linux/libc-compat.h
> index 44b8a6b..c316725 100644
> --- a/include/uapi/linux/libc-compat.h
> +++ b/include/uapi/linux/libc-compat.h
> @@ -171,42 +171,94 @@
> #else /* !defined(__GLIBC__) */
Note that right now, the content above this line in libc-compat.h
makes assumptions about what glibc does and doesn't define that are
specific to current glibc versions. I think it would be nice to make
the whole remainder of the file unconditional rather than being the
#else path for !defined(__GLIBC__). Then future versions of glibc can
properly define their own __UAPI_DEF_* macros to tell the kernel
headers about anything new the define. But I don't think that has to
be part of the same change you're proposing now.
Rich
> /* Definitions for if.h */
> +#if !defined(__UAPI_DEF_IF_IFCONF)
> #define __UAPI_DEF_IF_IFCONF 1
> +#endif
> +#if !defined(__UAPI_DEF_IF_IFMAP)
> #define __UAPI_DEF_IF_IFMAP 1
> +#endif
> +#if !defined(__UAPI_DEF_IFNAMSIZ)
> #define __UAPI_DEF_IF_IFNAMSIZ 1
> +#endif
> +#if !defined(__UAPI_DEF_IFREQ)
> #define __UAPI_DEF_IF_IFREQ 1
> +#endif
> /* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
> +#if !defined(__UAPI_DEF_IF_NET_DEVICE_FLAGS)
> #define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
> +#endif
> /* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
> +#if !defined(__UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO)
> #define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
> +#endif
>
> /* Definitions for in.h */
> +#if !defined(__UAPI_DEF_IN_ADDR)
> #define __UAPI_DEF_IN_ADDR 1
> +#endif
> +#if !defined(__UAPI_DEF_IN_IPPROTO)
> #define __UAPI_DEF_IN_IPPROTO 1
> +#endif
> +#if !defined(__UAPI_DEF_IN_PKTINFO)
> #define __UAPI_DEF_IN_PKTINFO 1
> +#endif
> +#if !defined(__UAPI_DEF_IP_MREQ)
> #define __UAPI_DEF_IP_MREQ 1
> +#endif
> +#if !defined(__UAPI_DEF_SOCKADDR_IN)
> #define __UAPI_DEF_SOCKADDR_IN 1
> +#endif
> +#if !defined(__UAPI_DEF_IN_CLASS)
> #define __UAPI_DEF_IN_CLASS 1
> +#endif
>
> /* Definitions for in6.h */
> +#if !defined(__UAPI_DEF_IN6_ADDR)
> #define __UAPI_DEF_IN6_ADDR 1
> +#endif
> +#if !defined(__UAPI_DEF_IN6_ADDR_ALT)
> #define __UAPI_DEF_IN6_ADDR_ALT 1
> +#endif
> +#if !defined(__UAPI_DEF_SOCKADDR_IN6)
> #define __UAPI_DEF_SOCKADDR_IN6 1
> +#endif
> +#if !defined(__UAPI_DEF_IPV6_MREQ)
> #define __UAPI_DEF_IPV6_MREQ 1
> +#endif
> +#if !defined(__UAPI_DEF_IPPROTO_V6)
> #define __UAPI_DEF_IPPROTO_V6 1
> +#endif
> +#if !defined(__UAPI_DEF_IPV6_OPTIONS)
> #define __UAPI_DEF_IPV6_OPTIONS 1
> +#endif
> +#if !defined(__UAPI_DEF_IN6_PKTINFO)
> #define __UAPI_DEF_IN6_PKTINFO 1
> +#endif
> +#if !defined(__UAPI_DEF_IP6_MTUINFO)
> #define __UAPI_DEF_IP6_MTUINFO 1
> +#endif
>
> /* Definitions for ipx.h */
> +#if !defined(__UAPI_DEF_SOCKADDR_IPX)
> #define __UAPI_DEF_SOCKADDR_IPX 1
> +#endif
> +#if !defined(__UAPI_DEF_IPX_ROUTE_DEFINITION)
> #define __UAPI_DEF_IPX_ROUTE_DEFINITION 1
> +#endif
> +#if !defined(__UAPI_DEF_IPX_INTERFACE_DEFINITION)
> #define __UAPI_DEF_IPX_INTERFACE_DEFINITION 1
> +#endif
> +#if !defined(__UAPI_DEF_IPX_CONFIG_DATA)
> #define __UAPI_DEF_IPX_CONFIG_DATA 1
> +#endif
> +#if !defined(__UAPI_DEF_IPX_ROUTE_DEF)
> #define __UAPI_DEF_IPX_ROUTE_DEF 1
> +#endif
>
> /* Definitions for xattr.h */
> +#if !defined(__UAPI_DEF_XATTR)
> #define __UAPI_DEF_XATTR 1
> +#endif
>
> #endif /* __GLIBC__ */
>
> --
> 2.7.3
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