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From: "Jeffrey R.Carter" <spam.jrcarter.not@spam.acm.org.not>
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Subject: Re: GNAT or Language Problems?
Date: Sat, 17 Jun 2023 11:21:18 +0200
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On 2023-06-17 09:28, Randy Brukardt wrote:
> Regarding your second problem, refer to AI22-0041-1.
> 
> Essentially, there are problems if predicates are involved. We changed the
> rule to require static compatibility (as a Binding Interpretation). I don't
> have the energy to look up what "static compatibility" requires in this case
> (enjoy figuring out 4.9.1). In some cases, it requires static matching, in
> others, it has weaker requirements.

There are no predicates involved. One can cut it down to just the type and constant:

package B_Strings_Prob is
    type B_String (Max_Length : Positive := 1_000) is tagged limited private;

    Null_B_String : constant B_String; -- A string of zero characters
private -- B_Strings_Prob
    type B_String (Max_Length : Positive := 1_000) is tagged limited record
       Len   : Natural := 0;
       Value : String (1 .. Max_Length) := (1 .. Max_Length => ' ');
    end record;

    Null_B_String : constant B_String := (Max_Length => 1, others => <>);
end B_Strings_Prob;

and still get the error:

$ gnatmake -gnatc b_strings_prob.ads
x86_64-linux-gnu-gcc-13 -c -gnatc b_strings_prob.ads
b_strings_prob.ads:12:04: error: subtype does not statically match deferred 
declaration at line 5
gnatmake: "b_strings_prob.ads" compilation error

I don't see any mention of AI22-0041-1 in ARM 7.4.

> I don't have the time or energy tonight to look into your other problem.
> (I'm waiting for a backup to finish, or I would have already gone home --
> since I only got back from Lisbon last night, I'm not equipped for my usual
> late night work...)

I'm surprised you're this functional already.

-- 
Jeff Carter
"I was in love with a beautiful blonde once, dear.
She drove me to drink. That's the one thing I'm
indebted to her for."
Never Give a Sucker an Even Break
109