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From: Al Johnston <sofeise@mindspring.com>
Subject: Re: New to ada95: porting
Date: 2000/02/29
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Date: 2000-02-29T06:58:06+00:00
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> Look at the standard C interface utilities in the packages

Thanks, I have... I just don't know what to do with them..

for example:
1) cohen's book give an example of an interface to getenv() using
IF.C.Strings, but the gnat adainc code doesn't both with this
level, favoring a 'address of an unconstrained array.

2) how in the world do you implement a c char** as a
parameter in a procedure call?

3) I have a lot of these types of things in my current (8x) ada
code:

type NSV is array(positive range <>) of ordinal
type NSVP is access NSV;
type NI is record
    id : positive
    h : NSVP;
end record;
type HSV is array(positive range <>) of NI
type HSVP is access HSV;

This is used in an ada routine that calls a c routine.  currently
the c routine allocates the memory (including two different
types of dope vectors) and loads the structure and returns
it as a pointer, so when the ada code receives its value
for the inout arg of HSVP it thinks the unconstrained
array parts are "normal" ada unconstrained arrays.

Obviously, this is very nasty... and I have no expectation
that it will work under gnat (this stuff was written long ago
for sunAda; sun published there "dope vector" format and
my predecessor took advantage of it... and now I get to
pay).

Anyway, the above is the class of thing I am having trouble
figuring out how to re-code.  I desperately need an example
of the right way of doing this.  I was thinking about using
IF.C.Pointers on this one... but the outer private "element"
has a component that would need to be a inner private
"element" and at that point I get lost.


Well, those are the major types of issues that I am
confused on...

tnx for any guidance... at the moment recoding everything
in c is looking attractive.  We have a hell of a lot of these
types of structures (they are related to RPC client code).

-al


>

> When in doubt read the Reference Manual.

I don't have a problem reading the RM.... understanding it, however, is
another story :{

-al