As we contemplate an s-block syntax for BitC, one question that emerges
is initialization rules. In particular, BitC really wants to require
that pointer slots (a) be initialized, and (b) be non-null.
In the lispish surface syntax this doesn't feel awkward, but in an
s-block surface syntax we will soon want to introduce something like a
constructor, and we will then get into situations where we say "field p
must be a non-null pointer to a mumble", but field p will not be
initialized at the first line of the constructor.
>From a safety perspective, I believe that the following constraints are
sufficient to ensure safety:
1. Field p must be properly initialized to a non-null pointer
before it is used.
2. The object pointer must not escape from the constructor
until all such type safety constraints are satisified.
In particular this constrains exception values.
First, does everyone agree that these conditions are sufficient?
Second, do we believe that we can specify an algorithm for checking this
property so that it can be statically determined at source level whether
a program is well-formed w.r.t. type safety?
shap
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