Callback procedures in DEC Ada83

Callback procedures in DEC Ada83

[Stephen Bleasdale]

Hi,

Here's my question:

I would like to write callback routines in Ada83 using DEC Ada 3.0 on VAX/VMS.

I have used e.g. LIB$FILE_SCAN so I know how to use 'ADDRESS to supply callback
subprograms for use by existing routines. What I'd to do is actually call a
callback routine in my program.

I know this is not possible in vanilla Ada83, but ISTR once reading that most
implementations provide a non-portable way of doing this sort of thing.

I guess what I'm hoping for is that somewhere amongst all the DEC provided
routines is something of the form:

   procedure CALL_PROCEDURE ( ADDR : in SYSTEM.ADDRESS ) ;

---

Thanks in advance.

Stephen Davies <sd@eateggs.demon.co.uk>

Re: Callback procedures in DEC Ada83

[Larry Kilgallen]

In article <682.7077T710T120@eateggs.demon.co.uk>, Stephen Bleasdale <sd@eateggs.demon.co.uk> writes:

> I guess what I'm hoping for is that somewhere amongst all the DEC provided
> routines is something of the form:
> 
>    procedure CALL_PROCEDURE ( ADDR : in SYSTEM.ADDRESS ) ;

You want LIB.CALLG, which is named after the VAX instruction it
uses/emulates on VAX/Alpha.

Don't try to use it to call a subprogram which takes floating point
in the first six parameters in Alpha, as the semantics it provides
for parameter passing are to put the first six parameters into "the"
registers, with no way to specify the floating point set.

Larry Kilgallen