passfd on more platforms

[Bruno Haible]

Here's the result of testing passfd:

Linux      OK      BSD4.4 way, MSG_CMSG_CLOEXEC
FreeBSD    OK      BSD4.4 way
OpenBSD    OK      BSD4.4 way
NetBSD     FAIL    BSD4.4 way
AIX        OK      BSD4.4 way
HP-UX      OK      BSD4.3 way
IRIX       OK      BSD4.3 way
OSF/1      OK      BSD4.4 way
Solaris    OK      BSD4.3 way
Cygwin     FAIL    BSD4.4 way

It is a bit surprising that Solaris 10 says that it doesn't support the
BSD4.4 way. That is because
  checking for UNIX domain sockets SCM_RIGHTS that behave in BSD4.4 way... no
because CMSG_SPACE etc. are not declared by <sys/socket.h> by default.
I'm not sure whether gnulib should define _XOPEN_SOURCE, _XOPEN_SOURCE_EXTENDED,
or _POSIX_C_SOURCE. But's let's leave it as is for now, since the BSD4.3 way
works.

On NetBSD 5.0, the test reports
  sendfd: Invalid argument
and then hangs.

On Cygwin, the test fails:
  recvfd: Permission denied
  FAIL: test-passfd.exe

On mingw, I haven't even tried the module. It first requires
  - a 'socketpair' module for the test,
  - to rewrite the test to use the 'execute' module instead of fork().

Bruno
-- 
In memoriam Odette Sansom <http://en.wikipedia.org/wiki/Odette_Hallowes>