How to port exit(s) from C to Ada

How to port exit(s) from C to Ada

[Manuel Collado]

We are porting some legacy code from Modula2 + C to Ada. A basic library
module contains a procedure 'Terminate(status)' that forces termination
of the main program and returns a 'status' to the calling process. It is
implemented via the 'exit(status)' C system call.

I vould like to implement it in pure Ada. So far I'm aware of

    Ada.Command_Line.Set_Exit_Status (Code : in Exit_Status);

[LRM]: If the external execution environment supports returning an exit
status from a program, then Set_Exit_Status sets Code as the status.
Normal termination of a program returns as the exit status the value
most recently set by Set_Exit_Status, or, if no such value has been set,
then the value Success. If a program terminates abnormally, the status
set by Set_Exit_Status is ignored, and an implementation�defined exit
status value is set.

To terminate immediately, I can raise a user-defined unhandled
exception, but it would imply an abnormal termination, so the specified
exit status would be ingnored.

Is there a way to reproduce the behaviour of the 'exit(status)' C-call
in pure Ada, without calling it as a foreign procedure?

Thanks,
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Re: How to port exit(s) from C to Ada

[Georg Bauhaus]

Manuel Collado <m.collado@lml.ls.fi.upm.es> wrote:
: Is there a way to reproduce the behaviour of the 'exit(status)' C-call
: in pure Ada, without calling it as a foreign procedure?

A compiler may allow returning an Integer to the environment, if
your main unit is a function.
Or you could handle a user defined exception and set_exit_status.
 
-- georg

Re: How to port exit(s) from C to Ada

[Preben Randhol]

Manuel Collado wrote:
> We are porting some legacy code from Modula2 + C to Ada. A basic library
> module contains a procedure 'Terminate(status)' that forces termination
> of the main program and returns a 'status' to the calling process. It is
> implemented via the 'exit(status)' C system call.
> 
> I vould like to implement it in pure Ada. So far I'm aware of
> 
>     Ada.Command_Line.Set_Exit_Status (Code : in Exit_Status);

I think GNAT has something like this. You may want to check the source
code of it.

Preben
-- 
Ada95 is good for you.
http://libre.act-europe.fr/Software_Matters/02-C_pitfalls.pdf

Re: How to port exit(s) from C to Ada

[Stephen Leake]

Manuel Collado <m.collado@lml.ls.fi.upm.es> writes:

> To terminate immediately, I can raise a user-defined unhandled
> exception, but it would imply an abnormal termination, so the specified
> exit status would be ingnored.

Catch that exception in the top level procedure, and just exit
normally.

As long as you don't have dependent tasks, that will work.

> Is there a way to reproduce the behaviour of the 'exit(status)'
> C-call in pure Ada, without calling it as a foreign procedure?

There's really nothing wrong with calling 'exit', if that's the
behaviour you actually want.

-- 
-- Stephe

Re: How to port exit(s) from C to Ada

[Ted Dennison]

Manuel Collado <m.collado@lml.ls.fi.upm.es> wrote in message news:<3DA69C5B.A3B8F264@lml.ls.fi.upm.es>...
> We are porting some legacy code from Modula2 + C to Ada. A basic library
> module contains a procedure 'Terminate(status)' that forces termination
> of the main program and returns a 'status' to the calling process. It is
> implemented via the 'exit(status)' C system call.
...
> To terminate immediately, I can raise a user-defined unhandled
> exception, but it would imply an abnormal termination, so the specified
> exit status would be ingnored.
> 
> Is there a way to reproduce the behaviour of the 'exit(status)' C-call
> in pure Ada, without calling it as a foreign procedure?

You could always handle the "Terminate_Program" exception in the outer
scope of the main program. That would work as long as you don't raise
the exception in elaboration code or in any code called from the
declaration section of the main routine.