Re: Variable length MODS

[James David Rich <james@xxxxxxxxxxx>]

On Fri, 13 Apr 2001, Peter Dow wrote:

> I believe the compiler puts in upper boundary checking based on what you
> enter as the dimensions or occurrences of the array or data structure, i.e.

but this is my point - there should not be an upper boundary on the size
of a variable if you don't say "I want a variable of this size".  You
should be able to define what a variable *looks* like without actually
saying how big it is.  That's what pointers and alloc are for.

> no relation  to the pointer. In the example I gave Tom, there's an array
> with a DIM(9999).  If only enough memory is allocated for 3 array entries,
> what happens when he references entry 4?  As far as the compiler is
> concerned, 4 is well within the defined upper boundary of 9999, but in fact
> no memory has been allocated for that entry and it moves into uncharted
> territory, but does not (as far as I know) give an error.

Note: the example below is pseudo-pseudo code :)

So if I want a variable (in this case a struct strdata) that has a:
{
char(length 1)
int(32 bit)
zone(5,2)
}
and I give DIM(1) but base it on a pointer ptr then I should be able to

alloc   sizeof(strdata)         ptr

and get the first occurence of strdata.  Then I ought to be able to

alloc   sizeof(strdata)         ptr

and get another occurence of strdata, or the second occurence.  But if the
compiler is limiting me to DIM(1) I cannot access my second occurence,
even though it is perfectly legitimate.  I really don't want to use DIM at
all, rather just use struct strdata to define what my memory that I'm
allocating looks like.  Then I should be able to allocate as much as I
want and as long as I don't try to access memory beyond what is allocated
(by moving my pointer too far or something) all should be well.

Or is there something wrong with this thinking?

James Rich
james@eaerich.com

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