Fix errno thread-safety under AIX

Unlike Linux or Solaris, errno under AIX is not thread-safe by
default.

This patch sets _THREAD_SAFE_ERRNO when AIX is detected in order to
force the thread-safe implementation of errno. Without this, calls
like stat() in the rrdtool plugin fail with errno incorrectly set,
leading to the inability to create previously absent rrd files.

Maybe _THREAD_SAFE should be set instead, to prevent other possible
threads-related problems, but this is enough to scratch my current
itch...

Here is the relevant part of /usr/include/errno.h on AIX:

 #if defined(_THREAD_SAFE) || defined(_THREAD_SAFE_ERRNO)
 /*
  * Per thread errno is provided by the threads provider. Both the extern
  * int
  * and the per thread value must be maintained by the threads library.
  */
 extern  int     *_Errno( void );
 #define errno   (*_Errno())

 #else

 extern int errno;

 #endif  /* _THREAD_SAFE || _THREAD_SAFE_ERRNO */

Signed-off-by: Aurelien Reynaud <collectd@wattapower.net>
Signed-off-by: Florian Forster <octo@huhu.verplant.org>

diff --git a/configure.in b/configure.in
index 3e31cf2..8f6eade 100644 (file)
--- a/configure.in
+++ b/configure.in
@@ -88,6 +88,10 @@ if test "x$ac_system" = "xSolaris"
 then
        AC_DEFINE(_POSIX_PTHREAD_SEMANTICS, 1, [Define to enforce POSIX thread semantics under Solaris.])
 fi
+if test "x$ac_system" = "xAIX"
+then
+       AC_DEFINE(_THREAD_SAFE_ERRNO, 1, [Define to use the thread-safe version of errno under AIX.])
+fi
 
 # Where to install .pc files.
 pkgconfigdir="${libdir}/pkgconfig"