From: Groepaz (groepaz_at_gmx.net)
Date: 2003-08-27 22:32:02
On Wednesday 27 August 2003 12:05, Andre Majorel wrote: > A compiler that would represent the null pointer with another bit > pattern that all zeroes and still do that would be non-conformant. With > respect to pointers, the integer constant 0 (i.e. the token 0 in the > source code) is special. The integer value (i.e. an int which compares > equal to 0) is not. ahhh yes that makes sence. > > OR is it so that *(char*)NULL is defined to access memory at location > > zero? (which would again raise the question how to access the memory at > > that certain bitpattern defined as NULL :=P) > > I'm not sure I understand your question but... The null pointer might > not be a valid address at all. On some architectures, attempting to > dereference a null pointer might cause not just a segfault but a > CPU-level exception (bus error or something like that). i am aware of the fact that memory-address zero is "illegal" on a lot of architectures, but regardless of that i might still want to use it. (for example to trigger an exception on purpose).... however, i'd guess that on machines that have NULL defined other than zero, it contains a bitpattern that make a _physically_ not available address and so doesnt clash with neither the real address zero nor the real address its bitpattern would be pointing to. gpz ---------------------------------------------------------------------- To unsubscribe from the list send mail to majordomo_at_musoftware.de with the string "unsubscribe cc65" in the body(!) of the mail.
This archive was generated by hypermail 2.1.3 : 2003-08-27 22:38:43 CEST