Re: Exiting from a function or procedure

[Robert Dewar <robert_dewar@my-deja.com>]

In article <vzJM4.1253$t25.356170@news.pacbell.net>,
  tmoran@bix.com wrote:
>      if not OK then
>        Log_And_Raise_Error;
>      end if;
>      return some_value;
>    end some_function;

I find the above code a very poor choice, precisely because,
as Tom notes, it will worry a maintenance programmer as to
what is going on! Far better is

      if not OK then
        Log_And_Raise_Error;
        raise Program_Error;
      end if;

or if you want to take the effort

      if not OK then
        Log_And_Raise_Error;
        raise Impossible_Exception_Cannot_Be_Raised;

Still for those using GNAT, use the opportunity to learn about
pragma No_Return, since it is a very clear way of documenting
the special case of a procedure that never returns.

By the way, I think it is a terrible design choice in Ada 95
that Raise_Exception can return to the caller. We end up special
casing this in GNAT to avoid the warning in this case (raising
Program_Error seems reasonable enough if Raise_Exception returns
and the return path is unblocked.


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