is this a bug of my Ada compiler

is this a bug of my Ada compiler

[IBRAHIM Bertrand]

In the following sample code, I've been very surprised not to be warned by the 
compiler that the initial value for k was out of range:

  procedure bug is

  type T is range 0..255;
  k: constant T := 16#FFE1#;

  begin
    null;
  end bug;

Even at execution time, no exception was raised. I thought that at least at 
elaboration time I would get a numeric_error but it compiled and ran without 
any problem. It is only if I try to compare k to another object of type T that 
I get the numeric_error exception raised.

Is it normal behaviour or is it a bug in my VADS 5.5 compiler (the SUN 
implementation) ?

Thank you for your replies,

Bertrand Ibrahim.


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Re: is this a bug of my Ada compiler

[Robert Firth]

In article <243@cui.UUCP> bertrand@cui.UUCP (IBRAHIM Bertrand) writes:

>In the following sample code, I've been very surprised not to be warned by the 
>compiler that the initial value for k was out of range:

    procedure bug is

    type T is range 0..255;
    k: constant T := 16#FFE1#;

    begin
      null;
    end bug;

>Even at execution time, no exception was raised.

Since the constant K is never subsequently used, the compiler
has probably optimised your code and deleted both K and the
initial assignment to it.  That is legitimate [RM 11.6 (7)],
but I confess I'd rather have had a compile-time warning.

[The person who thought up that
 rule about having to add at least
 as much matter as you quote was
 a BLOODY MORON
]

Re: is this a bug of my Ada compiler

[Fred Hosch]

In article <7324@aw.sei.cmu.edu>, firth@sei.cmu.edu (Robert Firth) writes:

> Since the constant K is never subsequently used, the compiler
> has probably optimised your code and deleted both K and the
> initial assignment to it.  That is legitimate [RM 11.6 (7)],
> but I confess I'd rather have had a compile-time warning.
> 
It's not clear to me that LRM 11.6(7) permits the compiler to optimize
away the declaration elaboration.  If K were a variable subsequently
assigned, the "predefined operation" of assignment "need not be invoked."
I think a CONSTRAINT_ERROR or NUMERIC_ERROR is required to be raised
in this case?

		---fred hosch
		fred@cs.utexas.edu

Re: is this a bug of my Ada compiler

[brucej]

> In the following sample code, I've been very surprised not to be warned by the
> compiler that the initial value for k was out of range:
>   procedure bug is
>   type T is range 0..255;
>   k: constant T := 16#FFE1#;
>  begin
>     null;
>   end bug;

The Verdix compiler typically does not elaborate static scalar constants.
The declaration in question merely inserts the constant `k' into the
compiler's symbol table. However, subsequent uses of the constant `k'
will be constraint checked against type `T'. In this example there are
no uses of `k'.

The new (1.10) version of the validation suite contains several tests
that enforce the requirement that constraint checks be performed on 
constant declarations.  It's a good bet that this minor bug will be fixed 
when Verdix validates VADS to 1.10.

Disclaimer: I do not work for Verdix, but for a computer vendor that
is the proud owner of a VADS source license. And yes, the 1.10 suite is 
a real pain....

----------
Bruce Jones, brucej@hcx1.harris.com
Harris Computers, Fort Lauderdale, FL