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Filename :
libc-compat.h
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/* * Compatibility interface for userspace libc header coordination: * * Define compatibility macros that are used to control the inclusion or * exclusion of UAPI structures and definitions in coordination with another * userspace C library. * * This header is intended to solve the problem of UAPI definitions that * conflict with userspace definitions. If a UAPI header has such conflicting * definitions then the solution is as follows: * * * Synchronize the UAPI header and the libc headers so either one can be * used and such that the ABI is preserved. If this is not possible then * no simple compatibility interface exists (you need to write translating * wrappers and rename things) and you can't use this interface. * * Then follow this process: * * (a) Include libc-compat.h in the UAPI header. * e.g. #include <linux/libc-compat.h> * This include must be as early as possible. * * (b) In libc-compat.h add enough code to detect that the comflicting * userspace libc header has been included first. * * (c) If the userspace libc header has been included first define a set of * guard macros of the form __UAPI_DEF_FOO and set their values to 1, else * set their values to 0. * * (d) Back in the UAPI header with the conflicting definitions, guard the * definitions with: * #if __UAPI_DEF_FOO * ... * #endif * * This fixes the situation where the linux headers are included *after* the * libc headers. To fix the problem with the inclusion in the other order the * userspace libc headers must be fixed like this: * * * For all definitions that conflict with kernel definitions wrap those * defines in the following: * #if !__UAPI_DEF_FOO * ... * #endif * * This prevents the redefinition of a construct already defined by the kernel. */ #ifndef _LIBC_COMPAT_H #define _LIBC_COMPAT_H /* We have included glibc headers... */ #if defined(__GLIBC__) /* Coordinate with glibc netinet/in.h header. */ #if defined(_NETINET_IN_H) /* GLIBC headers included first so don't define anything * that would already be defined. */ #define __UAPI_DEF_IN_ADDR 0 #define __UAPI_DEF_IN_IPPROTO 0 #define __UAPI_DEF_IN_PKTINFO 0 #define __UAPI_DEF_IP_MREQ 0 #define __UAPI_DEF_SOCKADDR_IN 0 #define __UAPI_DEF_IN_CLASS 0 #define __UAPI_DEF_IN6_ADDR 0 /* The exception is the in6_addr macros which must be defined * if the glibc code didn't define them. This guard matches * the guard in glibc/inet/netinet/in.h which defines the * additional in6_addr macros e.g. s6_addr16, and s6_addr32. */ #if defined(__USE_MISC) || defined (__USE_GNU) #define __UAPI_DEF_IN6_ADDR_ALT 0 #else #define __UAPI_DEF_IN6_ADDR_ALT 1 #endif #define __UAPI_DEF_SOCKADDR_IN6 0 #define __UAPI_DEF_IPV6_MREQ 0 #define __UAPI_DEF_IPPROTO_V6 0 #else /* Linux headers included first, and we must define everything * we need. The expectation is that glibc will check the * __UAPI_DEF_* defines and adjust appropriately. */ #define __UAPI_DEF_IN_ADDR 1 #define __UAPI_DEF_IN_IPPROTO 1 #define __UAPI_DEF_IN_PKTINFO 1 #define __UAPI_DEF_IP_MREQ 1 #define __UAPI_DEF_SOCKADDR_IN 1 #define __UAPI_DEF_IN_CLASS 1 #define __UAPI_DEF_IN6_ADDR 1 /* We unconditionally define the in6_addr macros and glibc must * coordinate. */ #define __UAPI_DEF_IN6_ADDR_ALT 1 #define __UAPI_DEF_SOCKADDR_IN6 1 #define __UAPI_DEF_IPV6_MREQ 1 #define __UAPI_DEF_IPPROTO_V6 1 #endif /* _NETINET_IN_H */ /* If we did not see any headers from any supported C libraries, * or we are being included in the kernel, then define everything * that we need. */ #else /* !defined(__GLIBC__) */ /* Definitions for in.h */ #define __UAPI_DEF_IN_ADDR 1 #define __UAPI_DEF_IN_IPPROTO 1 #define __UAPI_DEF_IN_PKTINFO 1 #define __UAPI_DEF_IP_MREQ 1 #define __UAPI_DEF_SOCKADDR_IN 1 #define __UAPI_DEF_IN_CLASS 1 /* Definitions for in6.h */ #define __UAPI_DEF_IN6_ADDR 1 #define __UAPI_DEF_IN6_ADDR_ALT 1 #define __UAPI_DEF_SOCKADDR_IN6 1 #define __UAPI_DEF_IPV6_MREQ 1 #define __UAPI_DEF_IPPROTO_V6 1 #endif /* __GLIBC__ */ #endif /* _LIBC_COMPAT_H */