More stringent testing of OSX BSD like behavior. Fix BSD mis-detection

on OSX depending on include order.

include/boost/predef/os/bsd.h

@@ -8,6 +8,13 @@ http://www.boost.org/LICENSE_1_0.txt)
 #ifndef BOOST_PREDEF_OS_BSD_H
 #define BOOST_PREDEF_OS_BSD_H
 
+/* Special case: OSX will define BSD predefs if the sys/param.h
+ * header is included. We can guard against that, but only if we
+ * detect OSX first. Hence we will force include OSX detection
+ * before doing any BSD detection.
+ */
+#include <boost/predef/os/macos.h>
+
 #include <boost/predef/version_number.h>
 #include <boost/predef/make.h>
 

test/macos_endian.c

@@ -12,9 +12,10 @@ http://www.boost.org/LICENSE_1_0.txt)
  * tests that the sys/param.h include can be included before
  * endian detection and still have it work correctly.
  */
-#include <boost/predef/os/macos.h>
 
-#if BOOST_OS_MACOS
+#if defined(__APPLE__)
 #   include <sys/param.h>
+#   include <boost/predef/os/bsd.h>
+#   include <boost/predef/os/macos.h>
 #   include <boost/predef/other/endian.h>
 #endif

test/macos_vs_bsd.c

@@ -9,12 +9,11 @@ http://www.boost.org/LICENSE_1_0.txt)
  * OSX can masquerade as BSD when sys/param.h is previously included.
  * So we test that we only detect OSX in this combination.
  */
-#include <boost/predef/os/macos.h>
-
-#if BOOST_OS_MACOS
+#if defined(__APPLE__)
 #   include <sys/param.h>
 #   include <boost/predef/os/bsd.h>
-#   if BOOST_OS_BSD
-#       error "Both BOOST_OS_MACOS and BOOST_OS_BSD defined."
+#   include <boost/predef/os/macos.h>
+#   if !BOOST_OS_MACOS || BOOST_OS_BSD
+#       error "BOOST_OS_MACOS not detected and/or BOOST_OS_BSD mis-detected."
 #   endif
 #endif