[PATCH] uapi libc compat: allow non-glibc to opt out of uapi definitions

[Felix Janda <felix.janda-1KBjaw7Xf1+zQB+pC5nmwQ@public.gmane.org>]

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-1KBjaw7Xf1+zQB+pC5nmwQ@public.gmane.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__) */
 
 /* 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