SCO comp.unix.sco.programmer FAQ.: How can I detect null references in my program?

	SCO comp.unix.sco.programmer FAQ. : SCO Development Environments. : How can I detect null references in my program?
	On OpenServer, there are two kernel global variables of interest in /etc/conf/pack.d/kernel/space.c that may be set. If notice_null_refs is non-zero, a kernel message will be generated when a program attempts to reference the page with a virtual address of zero. If signal_null_refs is non-zero, the kernel will detect zero page references and deliver a signal to the process, killing it and likely leaving a core dump for analysis. TLS594, available at ftp://ftp.sco.com/TLS allows finer control of these actions. robertlipe@usa.net
	On UnixWare 7, the 'nullptr' command can enable, disable, or trap null pointer references on a per-uid basis. On UW7 before 7.1.0, many system utilities (vi, more, pg) become unstable if nullptr disable is ineffect. robertlipe@usa.net
	With UW7.1, the MALLOC_CHECKS environment variable can be set to cause page zero to be unreadable. See malloc(3C). This works on a per-process basis. Note that since page zero must first be read to turn off access, when "nullptr disable" has been set, this MALLOC_CHECKS setting will cause a process to die when it first gets into malloc() code. dfp@sco.com
	Beginning with UnixWare 7.1.3 see also memtool(1) for dealing with null pointers and related memory bug checks. jls@sco.com
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