Re: ada to c interfaces and CHARS_PTR

[Al Johnston <sofeise@mindspring.com>]

> > > C has not 'in out' parameters, only 'in' parameters. To pass
> the
> >
> > ???? Although I am still trying to figure this stuff out, it
> seems to
> > me that c as as much of an in/out as any other language has.
>
> No, this is completely wrong, there is a very important semantic
> difference between passing a parameter as IN OUT (which in Ada

after spend a day trying to get from a STRING to a chars_ptr using
a chain function calls (without calling an allocator routine) I find
that
I am in no position to defined any of my understandings of anything.
It has been a bad day.

Yes, I guess there is a big deference between c's by value and ada's
mode in/out/inout modes.  I am just so used to viewing everything
in c as pass by value... if i need to pass a string in c, what really
gets passed is the "value" of the c's address (char *)... or maybe the
"value" of the address where the subroutine is to write the address
of the string (char **).

The ada code I inherited uses " foo : in system.address" as formal
parameters for all of its calls to c.  Because of this, I am not used
to thinking about ada passing/returning an array or record by
value... but instead it (ada) returns the "value" of the address
of the array or structure. This view is incredibly limited, and
I know it.  If I learned ada from supporting better code, maybe
I wouldn't have such weird understandings.

I tend to vies everything in terms of c's by value model.  I think
I better stop this habit QUICKLY.

If you wish to suggest any books in particular, I will make and effort
to get and read them.. I have spent a lot of time in cohen's book,
in the RM and Rat.

-al