Hello,

In the configure script, the program to detect whether
getaddrinfo is thread-safe is (pre-processor directives
omitted for brevity):

int main (void)
{
#ifdef h_errno
  return 0;
#else
  force compilation error
#endif
}

There are two problems with this strategy.

1) In the latest POSIX standard (Issue 7), h_errno has been removed
altogether.

http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/netdb.h.html

> The obsolescent h_errno external integer, and the obsolescent gethostbyaddr(),
> and gethostbyname() functions are removed, along with the HOST_NOT_FOUND,
> NO_DATA, NO_RECOVERY, and TRY_AGAIN macros.

2) In the previous POSIX standard (Issue 6), h_errno existed,
but it didn't have to be a macro.

http://pubs.opengroup.org/onlinepubs/009695399/basedefs/netdb.h.html

> When the <netdb.h> header is included, h_errno shall be available as a modifiable
> lvalue of type int. It is unspecified whether h_errno is a macro or an identifier
> declared with external linkage.

Thus if h_errno is an identifier declared with external linkage,
the macro test will fail.

Now what?

getaddrinfo is thread-safe /by definition/
(both in Issue 6 and in Issue 7)

http://pubs.opengroup.org/onlinepubs/009695399/functions/getaddrinfo.html
http://pubs.opengroup.org/onlinepubs/9699919799/functions/getaddrinfo.html

> The freeaddrinfo() and getaddrinfo() functions shall be thread-safe.

Maybe it would be sufficient to test for the POSIX feature macro?

http://pubs.opengroup.org/onlinepubs/007904975/functions/xsh_chap02_02.html

int main (void)
{
#if _POSIX_C_SOURCE >= 200112L (or 199506L ??)
  return 0;
#else
  force compilation error
#endif
}

Comments?

-- 
Regards.
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