nullptr(1)                                                nullptr(1)


       NAME
             nullptr - per-user NULL pointer reference checking

       SYNOPSIS
             nullptr [enable | disable]

       DESCRIPTION
             The nullptr command supports three different behaviors when
             applications dereference through a NULL pointer.  To support
             existing applications the default behavior as delivered is to
             enable null-pointer dereferences.

             When null-pointer dereferences are enabled, any user program
             attempt to read memory in the first page (addresses 0-4095)
             will successfully return zero.  When disabled, these memory
             reads behave like any other bad memory reference and cause a
             SIGSEGV signal to be sent to the referencing lightweight
             process.  Memory writes to page 0 always generate SIGSEGV.

             The default behavior can be changed by changing the NULLPTR
             tunable parameter.

             The nullptr command can be used to override the default
             behavior for a particular user, based on the user ID of the
             invoking process.

             The nullptr command can be called with the following
             arguments:

             enable         With this argument, nullptr enables null-
                            pointer references for the current user.

             disable        With this argument, nullptr disables null-
                            pointer references for the current user.

             With no arguments, nullptr displays the behavior in effect for
             the current user.

       REFERENCES
             sysi86(2)








                           Copyright 1994 Novell, Inc.               Page 1