Re: How to pass access parameters to/from C safely/portably?

[dewar@merv.cs.nyu.edu (Robert Dewar)]

<<For example, with ObjectAda, I find that applying pragma Export
forces an anonymous access parameter to not have accessibility
checks applied, and the actual parameter can be a simple C
pointer-to-something - this seems to be the obvious implementation,
but it's worth checking...anyone confirm if GNAT does the same?
>>

Yes, of course it does. However, note that access parameters are NOT
an appropriate mapping for pointer types in C calls in general, since
Ada does not permit a null value to be passed as an access parameter.
It may work to suppress access checking (for the call, or for the
procedure), but this is getting quite non-portable. The only "correct"
Ada way of representing a pointer parameter in a C routine is as
a (named) access type on the Ada side. Yes, this is a nuisance, it
may even be considered to be a real oversight in the language design.
It has caused endless trouble in bindings!