8017 Comply with POSIX.1-2008 and C++11 for the definition of NULL

*** 14,29 ****
   */
  
  #ifndef _SYS_NULL_H
  #define _SYS_NULL_H
  
  #ifndef NULL
  
  #if defined(_LP64)
  #define NULL    0L
  #else
  #define NULL    0
! #endif
  
  #endif  /* NULL */
  
  #endif  /* _SYS_NULL_H */
--- 14,52 ----
   */
  
  #ifndef _SYS_NULL_H
  #define _SYS_NULL_H
  
+ #include <sys/feature_tests.h>
+ 
  #ifndef NULL
  
+ /*
+  * POSIX.1-2008 requires that the NULL macro be cast to type void *.
+  * Historically, this has not been done, so we only enable this in a
+  * POSIX.1-2008 compilation environment.
+  */
+ 
+ #if defined(_XPG7) && !defined(__cplusplus)
+ #define NULL    ((void *)0)
+ #else
+ 
+ /*
+  * ISO C++ requires that the NULL macro be defined as a constant integral
+  * type evaluating to zero until C++11, and an integer or pointer literal
+  * with value zero from C++11 onwards.
+  */
+ 
+ #if defined(__cplusplus) && __cplusplus >= 201103L
+ #define NULL    nullptr
+ #else
  #if defined(_LP64)
  #define NULL    0L
  #else
  #define NULL    0
! #endif  /* _LP64 */
! #endif  /* C++11 */
! #endif  /* _XPG7 */
  
  #endif  /* NULL */
  
  #endif  /* _SYS_NULL_H */