Re: How to exit an Ada program with (unix shell) error code?

[Martin <martin.dowie@btopenworld.com>]

On May 5, 9:31 pm, a...@anon.org (anon) wrote:
> Martin.
>
>   You misread RM 10.2 (29), its quoted below.
>
> Both of the subprograms types are valid and portable and even though
> RM 10.2 (29) allows a vendor to restrict the main subprogram. Adacore
> (GNAT) and IBM which follow the RM to the letter have decided to allow
> and support both main subprograms types in Ada 83/95/2005 specs.
>
> Note: At this time Adacore and IBM are the only ones supporting Ada 2005.
>
> Now, in the GNAT design the "GNATBIND" process actually wraps the main
> subprogram ( "procedure main" or a "function main return integer" ) within
> a function called "main" within a package called "ada_main".  And if the
> "main" subprogram is a procedure, the binder function "main" calls this
> procedure and returns the exit status which is normally set to zero unless it
> is altered by "Ada.Command_Line.Set_Exit_Status". But if main subprogram
> is a function type of partition, then the binder function "main" returns the
> value returned from the partition "function main" to the OS as the exit
> status. To see this, just compile any program and then bind it. Check the
> resulting output files "b~<name>.adb" and its spec file before linking.
>
> Note: normally during linking the linker "GNATLINK" deletes the
> binder source/object files.
>
> So both of these are valid in the RM.  It just that most programmers prefer
> the "Procedure" type of partitions design.
>
> --
> -- main subprograms as a procedure
> --
> procedure main is
>   begin -- main
>      null ;
>   end main ;
> --
> -- or main subprograms as a public parameterless function
> --
> function main return integer is
>   begin -- main
>      return ( 0 ) ; -- 0 := normal exit status.
>   end main ;
>
> Ada RM -- quoted
>
>   RM 10.2 Program Execution
>    ...
>
>                          Implementation Permissions
>    ...
>
> 29    An implementation may restrict the kinds of subprograms it supports as
>                         ------------
> main subprograms. However, an implementation is required to support all main
>                                                             ----------------
> subprograms that are public parameterless library procedures.
> -----------
>
>   RM 10.1 Separate Compilation
>
> 1     A program unit is either a package, a task unit, a protected unit, a
> protected entry, a generic unit, or an explicitly declared subprogram other
>                                        ------------------------------
> than an enumeration literal. Certain kinds of program units can be separately
> compiled. Alternatively, they can appear physically nested within other
> program units.


You forgot to underline the important bit - "procedures". Not
"subprograms", not "functions or procedures" - just "procedures". The
_only_ subprogram that _must_ be supported is:

   procedure <Main_Subprogram_Name> is
   ...

Yes an implementation is free to support other forms (including
functions) but they are not portable.

Lord only know why your quoting 10.1 - it's nothing to do with main
procedures.

Cheers
-- Martin