Re: bug#17773: AIX build errors with coreutils-8.22

[Paul Eggert]

I looked into this some more, and found some problems:

* On Solaris we also need to define _POSIX_PTHREAD_SEMANTICS to prefer 
POSIX to pre-POSIX semantics for a few functions; see 
<http://docs.oracle.com/cd/E19683-01/806-6867/compile-fig-5/index.html>. 
 The extensions module does this, so a simple fix is to depend on the 
extensions module.  Almost everybody uses extensions anyway so I don't 
view this as being a big issue.  (Maybe threadlib should also depend on 
extensions, instead its calls to AC_USE_SYSTEM_EXTENSIONS and 
AC_GNU_SOURCE?)

* The patch uses $host_os so it should AC_REQUIRE([AC_CANONICAL_HOST]). 
 But why bother?  AC_CANONICAL_HOST is expensive and not every project 
needs it.  Instead, just define the symbols on all platforms; that's 
what 'extensions' does.

* This new behavior should be done in gl_EARLY, as _REENTRANT and 
_THREAD_SAFE affect the visibility of many other symbols.

So, how about the attached patch instead?  (I haven't tested it.)

0001-pthread-port-to-hosts-like-AIX-that-need-macros-like.patch
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