Out-of-bounds pointers

[Scott Amspoker]

 In article <4199 at letni.UUCP> doug at letni.LawNet.Com (Doug Davis) writes:
 >In article <1009 at mtxinu.UUCP> ed at mtxinu.COM (Ed Gould) writes:
 >>     void
 >>     f() {
 >>            char bug[100];
 >             ^^^^^^^^^^  I assume you mean buf here, right?
 >>            char *p;
 >>
 >>            p = buf;
 >>
 >>            p--;	/* p contains an illegal value: &buf[-1] */
 >             ^^^ Opps,  You have now entered the land of illegal addresses,
 >                 normally called the twilight zone, incrementing the
 >                 pointer is no longer guarenteed to be == &buf[0], that
 >                 is installation dependent.  Most likely it will == something
 >                 really weird and you get a core dump.  Which one you get
 >                 is left as an exercise to the reader.

Agreed, it is undefined.  However *most likely* it will work just fine (based
on the several dozen systems I've worked with).  I would recommend avoiding
it though.

-- 
Scott Amspoker
Basis International, Albuquerque, NM
(505) 345-5232