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From: Mirsad Todorovac
Subject: range check test programs
Date: 30 Jul 2003, 15:30:14

On Wed, 30 Jul 2003, Peter N Lewis wrote:

> On the subject of range checking, another difference that Mac Pascals
> implemented was unrangechecked arrays where the lower and upper bound
> are both 0.
>
> That is:
>
> type UnboundArray = array[0..0] of Whatever;
>
> disables the range check tests for array access.
>
> Generally this is used for open arrays as parameters, and it pretty
> much just avoids having to define a specific maximum array size
> (which can also get in to trouble, such as:
>
> type UnboundArray = array[0..kMaxInt] of Whatever;
>
> which can have a size bigger than 4Gig if Whatever has any noticeable
> size, and which can cause problems (does GPC handle record/array
> sizes larger than 32 bits on 32 bit platforms?).
>
> Anyway, I don't know that this is worth emulating even with
> --mac-pascal turned on, but I figured I'd mention it while I thought
> of it and while range checks were being discussed.

(I'm sorry if this has been discussed in Dec/2002, I couldn't find in
archives.)

Perhaps it's worth a spare attribute or two, such as

	attribute(norange);

and

	attribute(mustrange);

(the names are not obligatory part of suggestion).

They'd allow finer-grained range checking control than {R+} and {R-},
per object or per entity. Of course, if that's not too much trouble for
Frank.

I hope it's not adding too much complexity to the compiler. In ideal case,
every particular type of range check might be turned on/off independently.
OTOH, you might consider it an overkill, as GNU Pascal is not used for
programming Mars vehicles anyway (-;

I've read about some researches telling how most often errors are so
called "of by one" errors, and IMHO is thus a vital part of chasing bugs
out of the program, triggering an error exactly where it occurs, not
segfaulting miles of code later.

Have a nice day,
Mirsad

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