Re: [PATCH resent] uapi libc compat: allow non-glibc to opt out of uapi definitions
From: Carlos O'Donell <hidden>
Date: 2017-03-08 16:01:01
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lkml
On 11/11/2016 07:08 AM, 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
Would it be possible to amend the musl patch to define the macros to 1. A defined or undefined macro is typo prone. Please see this wiki for examples of the problems it causes: https://sourceware.org/glibc/wiki/Wundef Having the UAPI macros always defined and be 0 or 1 allows you to create tooling to check for problems, while an undefined macro is just that, either a mistake or the intended value.
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'
Do you have plans for fixing the error when the inclusion order is the other way? It will require kernel header changes to have each individual kernel header define the requisite __UAPI_* values to 1 e.g. moving libc-compat.h into the header. Do you plan to do that in a next step?
quoted hunk ↗ jump to hunk
Signed-off-by: Felix Janda <redacted> --- The previous mail misspelled the kernel mailing list. I am sorry for this resulting spam. There has already been one reply, which is available at http://www.openwall.com/lists/musl/2016/11/11/2 --- 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__) */
Would you please update the lead comment in libc-compat.h explaining this usage model so glibc and other libc's can follow best practice. Any new usage model should express how to fix header inclusion ordering in both directions.
/* Definitions for if.h */ +#if !defined(__UAPI_DEF_IF_IFCONF)
Typo prone. Please use #if __UAPI_DEF_IF_IFCONF for all of this.
#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__ */
-- Cheers, Carlos.