[Patches] IN6_IS_* macro and POSIX compilation

[Sebastien Vincent <sebastien dot vincent at turnserver dot org>]

Hi all,

We encounter some problems compiling a project (TurnServer.org) with 
latest eglibc/glibc and gcc. The compilation of Turnserver.org requires 
C99 and POSIX (no GNU capabilities).

List of issues reported:
https://sourceforge.net/p/turnserver/bugs/4/
https://bugs.launchpad.net/ubuntu/+source/eglibc/+bug/1086787
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=701428

The compilation runs fine with eglibc 2.13 but with recent eglibc/glibc 
it complains about:

"'const struct in6_addr' has no member named 's6_addr32'"


In inet/netinet/in.h (of the glibc trunk sources) the struct in6_addr is 
defined this way:
/* IPv6 address */
struct in6_addr
  {
    union
      {
  uint8_t __u6_addr8[16];
#if defined __USE_MISC || defined __USE_GNU
  uint16_t __u6_addr16[8];
  uint32_t __u6_addr32[4];
#endif
      } __in6_u;
#define s6_addr     __in6_u.__u6_addr8
#if defined __USE_MISC || defined __USE_GNU
# define s6_addr16    __in6_u.__u6_addr16
# define s6_addr32    __in6_u.__u6_addr32
#endif
  };

The IN6_IS_* macros are defined this way if __GNUC__ (which is always 
the case if gcc is used) :
#ifdef __GNUC__
# define IN6_IS_ADDR_UNSPECIFIED(a) \
  (__extension__                    \
   ({ const struct in6_addr *__a = (const struct in6_addr *) (a);       \
      __a->s6_addr32[0] == 0                  \
&& __a->s6_addr32[1] == 0                 \
&& __a->s6_addr32[2] == 0                 \
&& __a->s6_addr32[3] == 0; }))
...
#endif

In case of a strict C99 / POSIX compilation (-std=c99 
-D_POSIX_C_SOURCE=200112L -D_XOPEN_SOURCE=600) the __USE_MISC and 
__USE_GNU are not defined so the s6_addr32 is not available for the 
comparison.

So one possibility is to enforce the #ifdef __GNUC__ with the __USE_MISC 
or __USE_GNU definition => patch in attachment.

Best regards,
--
Sebastien Vincent

diff --git a/inet/netinet/in.h b/inet/netinet/in.h
index 89e3813..b4adfcb 100644
--- a/inet/netinet/in.h
+++ b/inet/netinet/in.h
@@ -394,7 +394,7 @@ extern uint16_t htons (uint16_t __hostshort)
 # endif
 #endif
 
-#ifdef __GNUC__
+#if (defined __GNUC__ && (defined __USE_MISC || defined __USE_GNU))
 # define IN6_IS_ADDR_UNSPECIFIED(a) \
   (__extension__							      \
    ({ const struct in6_addr *__a = (const struct in6_addr *) (a);	      \