Re: When to do a constraint check and not ??

[dewar@gnat.com (Robert Dewar)]

Tucker Taft <stt@avercom.net> wrote in message news:<3BE18C46.1AB713B4@avercom.net>...
> Certainly
> all compilers will want to believe that "in" and "in out"
> parameters are in range, so the (implicit) assignment
> from b to the formal parameter p when the function is
> called will need to ensure the value is in range.
> If it happens to have "stack junk" in it which puts it
> outside the typical 0..1 range used for booleans, then
> you will get a constraint_error raised here.

This is incorrect, it simply describes one possible implementation of
the RM rules, there is no specific requirement in the RM that the
range check be performed here. Different compilers may (and do) take
different
viewpoints on when to insert validity checks (to meet
the RM requirement that invalid data not cause erroneous
execution in most cases).
 
In GNAT Pro, a new switch -gnatV allows detailed control over when
validity checks occur, and can be used to force
validity checks in many situations where they are not required. We
have found this to be a useful debugging aid.