‘struct in6_addr’ has no member named ‘s6_addr32’ with -ansi

问题

I'm working through some compile errors when building OpenSSL with no-asm -ansi. I'm catching the error:

$ ./config no-asm -ansi
...
$ make
...
gcc -DDSO_DLFCN -DHAVE_DLFCN_H -DOPENSSL_THREADS -DOPENSSL_NO_STATIC_ENGINE -DOPENSSL_PIC
-DOPENSSLDIR="\"/usr/local/ssl\"" -DENGINESDIR="\"/usr/local/lib/engines\"" -Wall -O3
-pthread -m64 -DL_ENDIAN  -ansi -fPIC -Iinclude -I. -Icrypto/include -MMD -MF
crypto/bio/bss_dgram.d.tmp -MT crypto/bio/bss_dgram.o -c -o crypto/bio/bss_dgram.o
crypto/bio/bss_dgram.c
In file included from /usr/include/netdb.h:27:0,
                 from ./e_os.h:443,
                 from crypto/bio/bio_lcl.h:2,
                 from crypto/bio/bss_dgram.c:62:
crypto/bio/bss_dgram.c: In function ‘dgram_get_mtu_overhead’:
crypto/bio/bss_dgram.c:433:20: error: ‘const struct in6_addr’ has no member named ‘s6_addr32’
                 && IN6_IS_ADDR_V4MAPPED(&tmp_addr))
                    ^

I found the struct in /usr/include/linux/in6.h:

#if __UAPI_DEF_IN6_ADDR
struct in6_addr {
    union {
        __u8        u6_addr8[16];
#if __UAPI_DEF_IN6_ADDR_ALT
        __be16      u6_addr16[8];
        __be32      u6_addr32[4];
#endif
    } in6_u;
#define s6_addr         in6_u.u6_addr8
#if __UAPI_DEF_IN6_ADDR_ALT
#define s6_addr16       in6_u.u6_addr16
#define s6_addr32       in6_u.u6_addr32
#endif
};
#endif /* __UAPI_DEF_IN6_ADDR */

I don't recall needing to define __UAPI_DEF_IN6_ADDR_ALT in the past. Searching for it reveals the following from the kernel's libc-compat.h, line 95 or so (if I am parsing it correctly):

#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
#define __UAPI_DEF_IPV6_OPTIONS         1
#define __UAPI_DEF_IN6_PKTINFO          1
#define __UAPI_DEF_IP6_MTUINFO          1

How should I proceed to get the alternate symbols defined?

The system is Ubuntu 14.04 (x86_64):

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.4 LTS
Release:    14.04
Codename:   trusty

GCC is:

$ gcc --version
gcc (Ubuntu 4.8.4-2ubuntu1~14.04.1) 4.8.4
Copyright (C) 2013 Free Software Foundation, Inc.

回答1:

This turned out to be interesting... The short of it is I needed to add both -ansi and -D_DEFAULT_SOURCE=1. However, -D_DEFAULT_SOURCE=1 kind of undoes what -ansi is trying to accomplish so it needs to be contained.

First, /usr/include/linux/in6.h was the wrong header. I found it through a grep for struct in6_addr, and not tracing includes like needed to be done.

Next... -D_DEFAULT_SOURCE=1 indirectly came from /usr/include/netinet/in.h:

#ifndef __USE_KERNEL_IPV6_DEFS
/* IPv6 address */
struct in6_addr
  {
    union
      {
    uint8_t __u6_addr8[16];
#ifdef __USE_MISC
    uint16_t __u6_addr16[8];
    uint32_t __u6_addr32[4];
#endif
      } __in6_u;
#define s6_addr         __in6_u.__u6_addr8
#ifdef __USE_MISC
# define s6_addr16      __in6_u.__u6_addr16
# define s6_addr32      __in6_u.__u6_addr32
#endif
  };
#endif /* !__USE_KERNEL_IPV6_DEFS */

Manually enabling __USE_MISC did not work. Tracing things for __USE_MISC in /usr/include/features.h:

/*
...
   __USE_MISC       Define things from 4.3BSD or System V Unix.
...
*/

#undef __USE_MISC
...

#if defined _DEFAULT_SOURCE
# define __USE_MISC 1
#endif

And finally, from a comment in /usr/include/features.h:

_DEFAULT_SOURCE The default set of features (taking precedence over __STRICT_ANSI__).

Though _DEFAULT_SOURCE=1 diverges from -ansi, the impact can be limited to the one source file that's affected by IN6_IS_ADDR_V4MAPPED. That is, in for the C source file crypto/bio/bss_dgram.c:

/* OpenSSL copyright ... */

#ifndef _DEFAULT_SOURCE
# define _DEFAULT_SOURCE 1
#endif

#include <stdio.h>
#include <errno.h>
#include <netinet/in.h>
...

Fiddling with __USE_KERNEL_IPV6_DEFS made things even worse. I believe it enabled /usr/include/linux/in6.h, which had similar (but completely different) member names than <netinet/in.h>.

来源：https://stackoverflow.com/questions/36220341/struct-in6-addr-has-no-member-named-s6-addr32-with-ansi

标签

Linux

ipv6

ansi