Hallo, Mario!

*** Am Donnerstag 25. Juli 1996 um 09:51 schrieb Mario Semo an Thomas Seeling:

 TS>> void foo(int *x) {
 TS>> *x++;
 TS>> z=*x;

 MS> ??? whats illegal with z=*x;? x is a int *, *x is a int, ....
But x does not contain a valid pointer. As soon as x is incremented, it
(kind of) points to the successor of (*x), but that location is not defined
as a valid variable in the source.

 TS>> void bar(void) {
 TS>> int abc;
(*x) from above could point to (&abc)-1, (&abc)+1 or even something
completely different, as you invoke undefined behaviour (here "1"
means sizeof(int)).

 TS>> foo(&abc);

 MS> even with this the above is ok.
No, it is not. You may not reference pointers which contain illegal values.
Even more rigid, you must not construct such pointers if you want to stay
Ansi/Iso conformant.


Tschau...Thomas

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